A system and method permit communications of a mobile station of emergency service personnel while blocking communications of mobile stations of other users. In response to an emergency in a region, a mobile switching center may be configured to restrict communications of mobile stations in the region through an identified cell site base station controlled by the mobile switching center during the emergency while the identified cell site base station continues wireless radio frequency transmissions. This configuration may be accomplished with the use of a trigger, such as a Specific_Called_Party_Digit_String trigger. While the mobile switching center is configured for the emergency, a designated trigger condition may be detected with respect to an attempted communication for a mobile station through the identified cell site base station.

A typical wireless mobile communication network is made of a number of cells, each of which includes at least one fixed-location transceiver known as a cell site or base station. The base station within each cell provides radio coverage for a variable number of mobile communication devices located within the geographic service area the cell. Radio coverage for base stations in nearby cells may overlap so that a mobile communication device in any one cell can communicate through and transition into other cells as the user roams, including handoff during an ongoing communication. The base station is continuously broadcasting radio frequency signals in the cell to identify itself and receive signals from the mobile communications devices that are located within that cell. The base station communicates with the wireless mobile communication devices within the cell by receiving and transmitting RF signals. When a call is made from the mobile communications device, the call attempt signaling is transmitted by the mobile communication device to the base station with the strongest RF signal (typically the closest physical base station). The selected base station receives and initially processes the call.
In recent years, wireless mobile communications devices have increasingly been used by criminal and terrorist organizations during the commission of a crime or attack. For example, during a three-day terrorist attack that struck several locations in Mumbai, India during late 2008, the attackers used mobile communications devices to coordinate the attack, monitor international reaction to the attacks, and keep abreast of police and military efforts to end the attack. The attackers also used mobile communication devices to order the killing of hostages and to adjust other tactics while the attacks were underway.
Currently, there is a process between the National Communication Service (NCS) and wireless mobile communication network carriers, such as Verizon Wireless, to prevent mobile communication in an affected area. This process defines a procedure for shutting down mobile communications in a given number of cells within the affected area (i.e., affected cells) by shutting off all transmit amplifiers within the base stations in each cell so as to stop transmission of RF signal from the base station in the affected cell. However, given the nature of RF propagation, once a base station shuts down, the RF from base stations in the surrounding cells fills the affected cell. Although the performance may not be the same in the affected cell, the RF from the surrounding areas often would be sufficient for communications use.
Due to the nature of RF propagation, the current form of shutting down mobile communications in a given cell requires an excessively large number of base stations be shut down. This includes shutting down the base stations in the affected cells and also shutting down base stations in surrounding cells that would propagate RF into the affected cells. As an example, in the case of New York City, in order to shut down mobile communications in Mid-town Manhattan, it would be necessary to shut down base stations in all cells located in Mid-town Manhattan (i.e., the affected cells) and also shut down all base stations in cells in New York City's other four boroughs—Bronx, Brooklyn, Queens, and Staten Island—and in New Jersey several miles west of the Hudson River (i.e., the surrounding cells). By shutting down the mobile communications in both the affected and surrounding cells, the general public located in the surrounding cells is prevented from communicating on the mobile communications network. This resulting shut down of mobile communications in the surrounding cells leads to a loss of revenue in both the affected and surrounding cells, thereby complicating the decision to shut down the mobile communications network.
The current method also does not allow emergency service personnel in the affected and surrounding cells to communicate on the wireless mobile communication network. Such emergency service personnel include, for example, E911 personnel, Wireless Priority Service ("WPS") personnel, or public safety personnel Further, because all mobile communications are shut down in the affected and surrounding cells, the general public is unable to communicate on the mobile communication network with emergency service agencies (such as E911) or emergency service personnel.
Hence a need exists for more effective techniques to selectively prevent mobile communication in affected cells without preventing mobile communications in cells surrounding the affected cells.

Public safety communications incident response


A signal transmission cable, formed in a flat and flexible shape, comprises an insulating body as outmost layer of the signal transmission cable. A woven fabric layer is arranged within the insulating body. A tin foil is arranged within the woven fabric layer. Two signal lines are encapsulated within the tin foil, and two power lines are placed within the insulating body. The signal lines and the power lines respectively are covered with an insulating layer. The signal transmission cable therefore constructed is easily wound and reduces the fabrication cost.

1. Field of the Invention
The invention relates to a signal transmission cable structure and, more particularly, to a signal transmission cable formed in flat and flexible shape.
2. Description of the Related Art
A signal transmission cable is conventionally used to connect, for example, a telephone handset or different computer components.
FIG. 1 and FIG. 2 are respectively a perspective view and a cross-sectional view showing a conventional signal transmission cable. As shown, a conventional signal transmission cable 1a is usually cylindrical, and comprises an insulating body 10a, a woven fabric layer 11a, a tin foil 12a, a nylon thread 13a, a ground line 19a, an insulating layer 18a, two signal lines 14a, 15a and two power lines 16a, 17a. The insulating body 10a is made of PVC having good insulating properties, and is the outmost layer of the signal transmission cable 1a. The woven fabric layer 11a is placed within the insulating body 10a, and acts as anti-interference protection. The ground lines 19 and the tin foil 12a are placed within the insulating layer 10a. The ground lines 19a are placed between the tin foil 12a and the woven fabric layer 10a. Within the tin foil 10a is further arranged the nylon thread 13a to improve the flexibility of the signal transmission cable 1a. The two signal lines 14a, 15a and the two power lines 16a, 17a within the nylon thread 13a and the two signal lines 14a, 15a are together encapsulated within the insulating layer 18a to prevent interference. In application, a terminal end of the signal transmission cable 1a is connected to a signal plug 2a.
Although the above conventional signal transmission cable has good signal transmission results, its outer shape however is cylindrical and occupies a substantial space when being wound. The conventional signal transmission cable cannot be therefore conveniently received in a device body and need an external receiving member. If the user carries outdoor the electronic device to which the conventional signal transmission cable is connected, the user further needs to take with him/her several additional connecting lines which connection is time-consuming. The additional connecting lines further take substantial occupation space and may be lost. If the signal transmission cable is outwardly laid on a flat surface, the resulting protrusion of the cable is not aesthetic and further may easily causes a walking person to stumble. Moreover, with a cylindrical outer shape, the different lines within the cable are separated with a relatively small spacing distance, which easily causes interference. Because bending of the cylindrical cable may further negatively affects the signal transmission, the nylon thread is therefore traditionally needed to increase the flexibility of the cable, which increases the fabrication cost.
It is therefore a principal object of the invention to provide a structure of signal transmission cable that is formed in a flat and flexible shape, which enables easy winding in a cable-receiving case, prevents interference between the different lines within the cable, does not protrude when laid on a flat surface, and reduces the occupation space when received within a device body.
It is another object of the invention to provide a structure of signal transmission cable which construction does not need a nylon thread to have a good flexibility, which reduces the manufacturing cost.
To accomplish the above and other objectives, a signal transmission cable of the invention, formed in a flat and flexible shape, comprises an insulating body as outmost layer of the signal transmission cable. A woven fabric layer is arranged within the insulating body. A tin foil is arranged within the woven fabric layer. Two signal lines are encapsulated within the tin foil, and two power lines are placed within the insulating body. The signal lines and the power lines respectively are covered with an insulating layer.
To provide a further understanding of the invention, the following detailed description illustrates embodiments and examples of the invention, this detailed description being provided only for illustration of the invention.


Methods and apparatus are provided for performing a handover by a serving base station in a communication system. A handover request message is received from a mobile station. A first handover response message is transmitted to the mobile station. The first handover response message includes a list of at least one neighbor base station. A handover indication message including a value of a handover indication type field is received. The value is determined by the mobile station from among at least two values individually indicating at least one of a handover cancel and the handover rejection. The value representing the handover cancel indicates that the mobile station intends to cancel a handover procedure, and the value representing the handover rejection indicates that the mobile station intends to reject performing handover with any of the at least one neighbor base stations in the list.

1. Field of the Invention
The present invention relates to a broadband mobile communication system, and more particularly to a method for performing a handover in a broadband wireless communication system employing an orthogonal frequency division multiplexing (hereinafter, referred to as an OFDM) method and an orthogonal frequency division multiplexing access (hereinafter, referred to as an OFDMA) method.
2. Description of the Related Art
In the fourth generation (hereinafter, referred to as a 4G) communication system, which is the next generation communication system, research has been actively pursued to provide users with services having various quality of services (hereinafter, referred to as a QoSs) and supporting a transmission speed of about 100 Mbps. The current third generation (hereinafter, referred to as a 3G) communication system supports a transmission speed of about 384 kbps in an outdoor channel environment having a relatively unfavorable channel environment, and supports a transmission speed of 2 Mbps at maximum even in an indoor channel environment having a relatively favorable channel environment.
Meanwhile, wireless local area network (hereinafter, referred to as a LAN) system, and a wireless metropolitan area network (hereinafter, referred to as a MAN) systems generally support transmission speeds of 20 to 50 Mbps. Accordingly, in the current 4 G communication system, research has been actively pursued to develop a communication system to ensure mobility and QoS in the wireless LAN system and the wireless MAN system supporting relatively high transmission speeds, and to support a high speed service which will be provided by the 4 G communication system.
Since the wireless MAN system has a wide service coverage and supports a high transmission speed, it is suitable for supporting a high speed communication service. However, because the wireless MAN system is a system which does not completely consider the mobility of a subscriber station (SS), a handover due to the high-speed movement of a subscriber station is also not considered. Herein, the wireless MAN system is a broadband wireless access (BWA) communication system, and it has a service coverage area which is larger than that which the wireless LAN system provides and, additionally, supports a transmission speed higher than that which the wireless LAN system provides.
A system employing an OFDM method and an OFDMA method in order to enable a physical channel of the wireless MAN system to support a broadband transmission network is known as an IEEE (Institute of Electrical and Electronics Engineers) 802.16a communication system. The IEEE 802.16a communication system is a broadband wireless access communication system employing an OFDM/OFDMA method. Further, since the IEEE 802.16a communication system applies an OFDM/OFDMA method to the wireless MAN system, the IEEE 802.16a communication system transmits a physical channel signal using a plurality of sub-carriers, thereby enabling a high speed data transmission. Therefore, the IEEE 802.16a communication system is called a broadband wireless access communication system.
Hereinafter, the structure of the conventional IEEE 802.16a communication system will be descried with reference to FIG. 1.
FIG. 1 is a block diagram schematically showing the structure of the IEEE 802.16a communication system. The IEEE 802.16a communication system has a single cell structure and includes a base station (BS) 100 and a plurality of subscriber stations 110, 120, and 130 controlled by the base station 100. The transmission/reception of signals between the base station 100 and the subscriber stations 110, 120, and 130 are accomplished through the OFDM/OFDMA method.
Hereinafter, the structure of the downlink frame of the conventional IEEE 802.16a communication system will be descried with reference to FIG. 2 which is a view which illustrates the structure of the downlink frame of the IEEE 802.16a communication system.
Referring to FIG. 2, the downlink frame of the IEEE 802.16a communication system includes a preamble portion 200, a broadcast control portion 210, and a plurality of time division multiplex (hereinafter, referred to as a TDM) portions 220 and 230. A synchronization signal (i.e., preamble sequence) used in obtaining a mutual synchronization between a base station and a subscriber station is transmitted through the preamble portion 200. The broadcast control portion 210 includes a downlink (hereinafter, referred to as a DL) portion DL-MAP 211 and an uplink (hereinafter, referred to as an UL) portion UL-MAP 213. The DL_MAP portion 211 is a portion through which a DL_MAP message is transmitted. Table 1 shows information elements (hereinafter, referred to as IEs) contained in the DL_MAP message.
TABLE 1SyntaxSizeNotesDL_MAP_Message_Format( ) {Management Message Type=28 bitsPHY Synchronization FieldVariableSee AppropriatePHY specification DCD Count8 bitsBase Station ID48 bits  Number of DL_MAP Element n16 bits Begin PHY specific section {See ApplicablePHY sectionfor (i=1; i<=n; i++) {For each DL_MAPelement 1 to nDL_MAP Information Element( )VariableSee correspondingPHY specification If!(byte boundary) {4 bitsPadding to reachbyte boundaryPadding Nibble}}}}
As shown in Table 1, the DL_MAP message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the 'PHYsical (PHY) Synchronization' set according to a modulation method and a demodulation method applied to a physical channel in order to obtain a synchronization, the 'DCD count' representing a count corresponding to the configuration variation of a downlink channel descript (hereinafter, referred to as a DCD) message containing a downlink bust profile, the 'Base Station ID'representing a base station identifier (BSID), and the 'Number of DL_MAP Elements n' representing the number of elements existing after the Base Station ID. Especially, the DL_MAP message contains information on ranging codes assigned to each ranging which will be described later.
Further, the UL_MAP portion 213 is a portion through which an UL_MAP message is transmitted. Table 2 shown below illustrates IEs contained in the UL_MAP message.
TABLE 2SyntaxSizeNotes UL_MAP_Message_Format( ) { Management Message Type=38 bits  Uplink Channel ID8 bits UCD Count8 bits Number of UL_MAP Element n16 bits  Allocation Start Time32 bits  Begin PHY specific section {See ApplicablePHY sectionFor (i=1; i<=n; i++) {For each UL_MAPelement 1 to nUL_MAP_Information_Element( )VariableSee correspondingPHY specification}}}
As shown in Table 2, the UL_MAP message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the 'Uplink Channel ID' representing a used uplink channel identifier, the 'UCD count' representing a count corresponding to the configuration variation of an uplink channel descript (hereinafter, referred to as an UCD) message containing an uplink bust profile, and the 'Number of UL_MAP Elements n' representing the number of elements existing after the UCD count. Herein, the uplink channel identifier is uniquely assigned in a media access control (hereinafter, referred to as a MAC) sub-layer.
Further, the TDM portions 220 and 230 (as shown in FIG. 2) are portions corresponding to time slots assigned to each subscriber station by a time division multiplexing (hereinafter, referred to as a TDM) time division multiple access (hereinafter, referred to as a TDMA) TDM/TDMA method. The base station transmits broadcast information, which must be broadcasted, to subscriber stations managed by the base station through the DL_MAP portion 211 of the downlink frame by means of a preset center carrier. Then, each of the subscriber stations is powered on and the base station then monitors all frequency bands set in each of the subscriber stations in advance, and detects a pilot channel signal having the highest pilot carrier to interference and noise ratio (hereinafter, referred to as a CINR).
Also, the subscriber station determines a base station having transmitted the pilot channel signal having the highest CINR to be a base station to which the subscriber station currently belongs. Further, the subscriber station confirms the DL_MAP portion 211 and the UL_MAP portion 213 of the downlink frame transmitted by the base station, and confirms control information controlling an uplink and a downlink of the subscriber station and information representing an actual position of data transmission/reception.
Table 3, illustrated below, shows the structure of the UCD message.
TABLE 3SyntaxSizeNotesUCD-message_Format( ) {Management Message Type=08 bitsUplink Channel ID8 bitsConfiguration Change Count8 bitsMini-slot size8 bitsRanging Backoff Start8 bitsRanging Backoff End8 bitsRequest Backoff Start8 bitsRequest Backoff End8 bitsTLV Encoded Information for the overall channelVariableBegin PHY Specific Section {For(i=1; i<=n; I+n) {Uplink_Burst_DescriptorVariable}}}
As shown in Table 3, the UCD message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the 'Uplink Channel ID' representing a used uplink channel identifier, the 'Configuration Change Count' counted by a base station, the 'Mini-slot Size' representing the size of a mini-slot of an uplink physical channel, the 'Ranging Backoff Start' representing a start point of a backoff using an initial ranging, that is, the size of an initial backoff window using an initial ranging, the 'Ranging Backoff' End representing an end point of a backoff using an initial ranging, that is, the size of a final backoff window, the 'Request Backoff Start' representing a start point of a backoff for 'contention data and requests', that is, the size of an initial backoff window, and the 'Request Backoff End representing an end point of a backoff for 'contention data and requests', that is, the size of a final backoff window.
Herein, the value of the backoff represents a kind of waiting time value for which a subscriber station must wait for the next ranging when failure occurs in rangings which will be described later. Further, a base station must transmit the backoff value, which is information on a time period for which the subscriber station must wait for the next ranging, to the subscriber station when the subscriber station fails in a ranging. For instance, when a value by the Ranging Backoff Start and the Ranging Backoff End is set to be 10, the subscriber station passes a chance in which the subscriber station can perform rangings of 210 times (i.e., 1024 times) and then must perform the next ranging.
Hereinafter, the structure of the uplink frame of the conventional IEEE 802.16a communication system will be descried with reference to FIG. 3, which is a view which illustrates the structure of the uplink frame of the IEEE 802.16a communication system.
Before describing FIG. 3, rangings as described and used in the IEEE 802.16a communication system, include, an initial ranging, a maintenance ranging, that is, a periodic ranging, and a bandwidth request ranging each of which will be described in detail below.
The initial ranging is a ranging which is performed when a base station requests the initial ranging in order to obtain a synchronization with a subscriber station. Further, the initial ranging is a ranging which is performed in order to match an exact time offset between the subscriber station and the base station and adjust the transmit power. That is, the subscriber station is powered on, receives a DL_MAP message, an UL_MAP message, and a UCD message, and obtains synchronization with the base station. Then, the subscriber station performs the initial ranging to adjust the time offset and the transmit power with the base station. The base station receives the MAC address of the subscriber station from the subscriber station through the initial ranging procedure. Further, the base station generates a basic connection ID (hereinafter, referred to as a basic CID) and a primary management connection ID (hereinafter, referred to as a primary management CID) mapped with the received MAC address of the subscriber station, and then transmits the generated basic CID and the primary management CID to the subscriber station. Then, the subscriber station recognizes the basic CID and the primary management CID of the subscriber station through the initial ranging procedure.
Herein, since the IEEE 802.16a communication system employs an OFDM/OFDMA method, the ranging procedure requires ranging sub-channels and ranging codes. A base station assigns usable raging codes (RCs) according to the object of a raging, that is, the kind of a raging. This will be described in detail.
The raging code is generated by segmenting pseudo-random noise (hereinafter, referred to as a PN) sequence having a predetermined length (e.g., length of 215−1 bits) by a predetermined unit. Generally, two sub-channels having a length of 53 bits constitute one ranging channel. Further, the raging code is constructed by segmenting a PN code through the ranging channel having a length of 106 bits. The 48 raging codes i.e., RC#1 to RC#48) (at maximum for 48 ranging codes per subscriber station) constructed in this way may be assigned to a subscriber station, and two raging codes (at minimum per a subscriber station) are applied to the three types of rangings, that is, the initial ranging, the periodic ranging and the bandwidth request ranging, according to a default value. In this way, different raging codes are assigned to each ranging. For instance, N number of raging codes are assigned for the initial ranging (N RCs for initial ranging), M number of raging codes are assigned for the periodic ranging (M RCs for periodic ranging), and L number of raging codes are assigned for the bandwidth request ranging (L RCs for BW-request ranging). The raging codes assigned in this way are transmitted to subscriber stations through the DL_MAP message as described above, and the subscriber stations perform the ranging procedure by using the raging codes contained in the DL_MAP message according to the objects of the raging code.
The periodic ranging is a ranging periodically performed when the subscriber station having adjusted the time offset and the transmit power with the base station through the initial ranging adjusts a channel status, etc., with the base station. The subscriber station performs the periodic ranging by means of the ranging codes assigned for the periodic ranging.
The bandwidth request ranging is a ranging performed when the subscriber station having adjusted the time offset and the transmit power with the base station through the initial ranging requests a bandwidth assignment in order to actually perform a communication with the base station.
Referring to FIG. 3, the uplink frame includes an 'Initial Maintenance Opportunities' portion 300 using the initial ranging, and the maintenance ranging, that is, the periodic ranging, a 'Request Contention Opportunities' portion 310 using the bandwidth request ranging, and a 'SS scheduled data' portion 320 containing the uplink data of subscriber stations. The Initial Maintenance Opportunities portion 300 includes a plurality of access burst intervals actually containing an initial ranging and a periodic ranging, and a collision interval in which collision between access burst intervals occurs. The Request Contention Opportunities portion 310 includes a plurality of bandwidth request intervals containing a bandwidth request ranging, and a collision interval in which collision between bandwidth request intervals occurs. Further, the SS scheduled data portion 320 includes a plurality of SS scheduled data parts (i.e., SS 1 scheduled data part to SS N scheduled data part) and a subscriber station transition gap which is present in each of the SS scheduled data parts.
An uplink interval usage code (hereinafter, referred to as a UIUC) portion which is a portion in which information designating the use of an offset recorded in an offset portion is recorded. Table 4 below shows the UIUC portion.
TABLE 4ConnectionIE nameUIUCIDDescriptionReserved0NAReserved for future useRequest1anyStarting offset of request regionInitial2broadcastStarting offset of maintenanceMaintenanceregion (used in Initial Ranging)Station3unicastStarting offset of maintenanceMaintenanceregion (used in periodic Ranging)Data Grant4unicastStarting offset of Data Grant BurstBurst Type 1Type 1 assignmentData Grant5unicastStarting offset of Data Grant BurstBurst Type 2Type 2assignmentData Grant6unicastStarting offset of Data Grant BurstBurst Type 3Type 3 assignmentData Grant7unicastStarting offset of Data Grant BurstBurst Type 4Type 4 assignmentData Grant8unicastStarting offset of Data Grant BurstBurst Type 5Type 5 assignmentData Grant9unicastStarting offset of Data Grant BurstBurst Type 6Type 6 assignmentNull IE10zeroEnding offset of the previous grant.Used to bound the length of thelast actual interval allocationEmpty11zeroUsed to schedule gaps intransmissionReserved12 to 15N/AReserved
As shown in Table 4, the UIUC portion contains information designating the use of the offset recorded in the offset portion. For instance, when a value of 2 is recorded in the UIUC portion, it signifies that a starting offset used in the initial ranging is recorded in the offset portion. When a value of 3 is recorded in the URIC portion, it signifies that a starting offset used in the maintenance ranging or the bandwidth request ranging is recorded in the offset portion. As described above, the offset portion is a portion recording a starting offset value used in the initial ranging, the bandwidth request ranging, or the maintenance ranging according to the information recorded in the UIUC portion. Further, information on a characteristic of a physical channel to be transmitted in the URIC portion is recorded in the UCD message.
Hereinafter, a ranging process between a base station and a subscriber station in the conventional IEEE 802.16a communication system will be descried with reference to FIG. 4 which is a flow diagram illustrating the ranging process between the base station and the subscriber station in the IEEE 802.16a communication system.
Referring to FIG. 4, the subscriber station 400 is powered on, monitors all frequency bands set in the subscriber station 400 in advance, and detects a pilot channel signal having the highest CINR. Also, the subscriber station 400 determines a base station 420 having transmitted the pilot channel signal having the highest CINR to be the base station 420 to which the subscriber station 400 currently belongs. Then, the subscriber station 400 receives the preamble of the downlink frame transmitted from the base station 420 and obtains a system synchronization with the base station 420.
As described above, when the system synchronization is obtained between the subscriber station 400 and the base station 420, the base station 420 transmits a DL_MAP message and an UL_MAP message to the subscriber station 400 in steps 411 and 413, respectively. Herein, as described in Table 1, the DL_MAP message performs the function of informing the subscriber station 400 of information required when the subscriber station 400 obtains a synchronization with respect to the base station 420 in a downlink, and information on the structure of a physical channel capable of receiving messages transmitted to the subscriber station 400 in the downlink. Further, as described in table 2, the UL_MAP message performs the function of informing the subscriber station 400 of information on the scheduling period of a subscriber station and the structure of a physical channel in an uplink.
Meanwhile, the DL_MAP message is broadcasted from a base station to all subscriber stations. Herein, a case in which a certain subscriber station can continuously receive the DL_MAP message signifies that the subscriber station has synchronized with the base station. That is, the subscriber stations having received the DL_MAP message can receive all messages transmitted through a downlink. Further, as described in Table 2, when the subscriber station fails in an access, the base station transmits the UCD message containing information notifying an usable backoff value to the subscriber station.
Meanwhile, when the subscriber station 400 having synchronized with the base station 420 performs the ranging, the subscriber station 400 transmits a ranging request (hereinafter, referred to as a RNG_REQ) message to the base station 420 in step 415. Then, in step 417, the base station 420 having received the RNG_REQ message transmits a ranging response (hereinafter, referred to as a RNG_RSP) message, which contains information for compensating for frequency, time, and transmit power for the ranging, to the subscriber station 400.
Table 5 illustrated below, shows the structure of the RNG_REQ message.
TABLE 5SyntaxSizeNotesRNG_REQ_message_Format( ) { Management Message Type=48 bits Downlink Channel ID8 bits Pending Until Complete8 bits TLV Encoded InformationVariableTLV specific}
As shown in Table 5, the 'Downlink Channel ID' represents a downlink channel identifier contained in the RNG_REQ message received in the subscriber station 400 through the UCD. The 'Pending Until Complete' represents a priority of a transmitted ranging response. That is, when the Pending Until Complete has a value of 0, a previous ranging response has a high priority. In contrast, when the Pending Until Complete has values other than 0, a currently transmitted ranging response has a high priority.
Table 6 illustrated below, shows the structure of the RNG_RSP message corresponding to the RNG_REQ message shown in Table 5.
TABLE 6SyntaxSizeNotesRNG_RSP_message_Format( ) { Management Message Type=58 bits Uplink Channel ID8 bits TLV Encoded InformationVariableTLV specific}
As shown in Table 6, the 'Uplink Channel ID' represents an uplink channel identifier contained in the RNG_REQ message. Meanwhile, in FIG. 4, since the IEEE 802.16a communication system considers only a state in which a subscriber station is currently motionless, that is, it does not entirely consider the mobility of the subscriber station, the base station 420 (as shown in FIG. 4) communicating with the subscriber station 400 unconditionally becomes a serving base station.
As described above, the IEEE 802.16a communication system considers only a state in which a subscriber station is currently motionless (i.e., a state in which the mobility of the subscriber station is not entirely considered), and a single cell structure. However, an IEEE 802.16e communication system is stipulated as a system considering the mobility of a subscriber station in the IEEE 802.16a communication system. Accordingly, the IEEE 802.16e communication system must consider the mobility of a subscriber station in a multi-cell environment. In order to support the mobility of the subscriber station in a multi-cell environment, changes in operations of the subscriber station and a base station are necessarily required. Especially, in order to support the mobility of the subscriber station, research into a handover of the subscriber station considering a multi-cell structure has been actively pursued.
Hereinafter, the structure of the conventional IEEE 802.16e communication system will be described with reference to FIG. 5.
FIG. 5 is a block diagram schematically showing the structure of the IEEE 802.16e communication system.
Referring to FIG. 5, the IEEE 802.16e communication system has a multi-cell structure, that is, a cell 500 and a cell 550. Further, the IEEE 802.16a communication system includes a base station 510 controlling the cell 500, a base station 540 controlling the cell 550, and a plurality of mobile subscriber stations (MSSs) 511, 513, 530, 551, and 553. The transmission/reception of signals between the base stations 510 and 540 and the mobile subscriber stations 511, 513, 530, 551, and 553 is accomplished through an OFDM/OFDMA method. Herein, the mobile subscriber station 530 (of the mobile subscriber stations 511, 513, 530, 551, and 553) exists in an overlapping area (i.e., handover area) between the cell 500 and the cell 550. Accordingly, only when a handover for the mobile subscriber station 530 must be supported, it is possible to support the mobility for the mobile subscriber station 530.
In the IEEE 802.16e communication system, a certain mobile subscriber station receives pilot channel signals transmitted from a plurality of base stations, and measures CINRs of the received pilot channel signals. The mobile subscriber station then selects a base station, which is the base station that has transmitted a pilot channel signal having the highest CINR from among the measured CINRs of the pilot channel signals, as a base station to which the mobile subscriber station currently belongs. That is, the mobile subscriber station recognizes a base station, which transmits a pilot channel signal capable of being favorably received in the mobile subscriber station, from among base stations having transmitted pilot channel signals as a base station to which the mobile subscriber station belongs. As a result, the base station to which the mobile subscriber station currently belongs becomes a serving base station. The mobile subscriber station having selected the serving base station receives a downlink frame and an uplink frame transmitted from the serving base station. Herein, the downlink frame and the uplink frame of the IEEE 802.16e communication system have the same structures as those of the downlink frame and the uplink frame of the IEEE 802.16a communication system shown in FIGS. 2 and 3 above and described herein.
The serving base station transmits a mobile subscriber station neighbor advertisement (hereinafter, referred to as a MOB_NBR_ADV) message to the mobile subscriber station. Table 7 illustrated below shows the structure of the MOB_NBR_ADV message.
TABLE 7SyntaxSizeNotesMOB_NBR_ADV_message_Format( ) { Management Message Type=488 bits Configuration Change Count8 bits N_NEIGHBORS8 bits For (j=0;j< N_NEIGHBORS;J++){  Neighbor BS-ID48 bits   Physical Frequency32 bits   TLV Encoded Neighbor InformationVariableTLV specific }}
As shown in Table 7, the MOB_NBR_ADV message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the 'Configuration Change Count' representing the number of times by which a Configuration changes, the 'N_NEIGHBORS' representing the number of neighbor base stations, the 'Neighbor BS-ID' representing identifiers (ID) of the neighbor base stations, the 'Physical Frequency' representing the physical frequency of the neighbor base station, and the 'TLV Encoded Neighbor Information' representing extra information relating to the neighbor base station in addition to the information.
The mobile subscriber station having received the MOB_NBR_ADV message transmits a mobile subscriber station scanning interval allocation request (hereinafter, referred to as a MOB_SCN_REQ) message to the serving base station when the mobile subscriber station intends to scan the CINRs of pilot channel signals transmitted from neighbor base stations. Herein, since a time point at which the mobile subscriber station requests a scanning has no direct relation to a scanning operation for the CINR of the pilot channel signal, a detailed description about the time point will be omitted.
Table 8 illustrated below shows the structure of the MOB_SCN_REQ message.
TABLE 8SyntaxSizeNotesMOB_SCN_REQ_message_Format( ) { Management Message Type=? 8 bits Scan Duration16 bitsUnits are frames}
As shown in Table 8, the MOB_SCN_REQ message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message and the 'Scan Duration' representing a scan duration for which the mobile subscriber station scans the CINRs of the pilot channel signals transmitted from the neighbor base stations. The 'Scan Duration' is constructed by the frame. Herein, the 'Management Message Type' of the MOB_SCN_REQ message to be transmitted has not been defined yet (i.e., Management Message Type=undefined or "?" as is shown in the table to conserve space).
Meanwhile, the serving base station having received the MOB_SCN_REQ message transmits a mobile subscriber station scanning interval allocation response (hereinafter, referred to as a MOB_SCN_RSP) message, which contains information to be scanned by the mobile subscriber station, to the mobile subscriber station. Table 9 illustrated below shows the structure of the MOB_SCN_RSP message.
TABLE 9SyntaxSizeNotesMOB_SCN_RSP_message_Format( ) { Management Message Type=?8 bits Length8 bitsin bytes For(I=0;i<Length/3;i++){  CID16 bits basic CID of theMSS  Duration8 bitsin frames }}
As shown in Table 9, the MOB_SCN_RSP message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the connection ID (hereinafter, referred to as a CID) of the mobile subscriber station having transmitted the MOB_SCN_REQ message, and a scan duration. In Table 9, the 'Management Message Type' of the MOB_SCN_RSP message to be transmitted has not been defined yet (i.e., Management Message Type=undefined), and the scan duration is a duration for which the mobile subscriber station performs the pilot CINR scanning. The mobile subscriber station having received the MOB_SCN_RSP message containing the scanning information scans pilot CINRs for neighbor base stations, which has been recognized through the MOB_NBR_ADV message, according to the scanning information parameters.
In order to support a handover in the IEEE 802.16e communication system, a mobile subscriber station must measure CINRs of pilot channel signals transmitted from neighbor base stations and a base station (i.e., serving base station) to which the mobile subscriber station currently belongs. Further, when the CINR of the pilot channel signal transmitted from the serving base station is smaller than the CINRs of the pilot channel signals transmitted from the neighbor base stations, the mobile subscriber station requests a handover from the serving base station. Herein, for convenience of description, the sentence 'measure the CINR of the pilot channel signal' may be expressed by a sentence 'scan or perform a scanning for the CINR of the pilot channel signal'. Also, the words 'scan' and 'scanning' have the same concept; 'scan' is used together with 'scanning' for convenience of description.
Hereinafter, a handover process by the request of a mobile subscriber station in the conventional IEEE 802.16e communication system will be descried with reference to FIG. 6.
FIG. 6 is a flow diagram illustrating the handover process by the request of the mobile subscriber station in the conventional IEEE 802.16e communication system.
Referring to FIG. 6, first, a serving base station 640 transmits a MOB_NBR_ADV message to a mobile subscriber station 600 in step 611. Then, the mobile subscriber station 600 receives the MOB_NBR_ADV message and obtains information on neighbor base stations. Further, in step 613, the mobile subscriber station 600 transmits a MOB_SCN_REQ message to the serving base station 640 when the mobile subscriber station 600 intends to scan the CINRs of pilot channel signals transmitted from the neighbor base stations. Herein, since a time point at which the mobile subscriber station 600 requests a scanning has no direct relation to a scanning operation for the CINR of the pilot channel signal, a detailed description about the time point will be omitted. Meanwhile, in step 615, the serving base station 640 having received the MOB_SCN_REQ message transmits the MOB_SCN_RSP message, which contains information to be scanned by the mobile subscriber station 600, to the mobile subscriber station 600. In step 617, the mobile subscriber station 600 having received the MOB_SCN_RSP message containing the scanning information performs a scanning for the CINRs of pilot channel signals with respect to neighbor base stations, which have been recognized through the reception of the MOB_NBR_ADV message, according to parameters (i.e., scan duration) contained in the MOB_SCN_RSP message.
Next, after having completely scanned the CINRs of the pilot channel signals received from the neighbor base stations, when the mobile subscriber station 600 determines to change the serving base station 640 to which the mobile subscriber station 600 currently belongs in step 619, that is, the mobile subscriber station 600 determines to change the current serving base station 640 to another new base station, the mobile subscriber station 600 transmits a mobile subscriber station handover request (hereinafter, referred to as a MOB_MSSHO_REQ) message to the serving base station 640 in step 621. Herein, a new base station (i.e., a base station to which the mobile subscriber station 600 is to be handed over), which is not a serving base station to which the mobile subscriber station 600 currently belongs, is called a target base station (target BS). Table 10 shows the structure of the MOB_MSSHO_REQ message and is illustrated below.
TABLE 10SyntaxSizeNotesMOB_MSSHO_REQ_message_Format( ) { Management Message Type=528 bits N_Recommended8 bits For (j=0;j< N_NEIGHBORS;J++){  Neighbor BS-ID48 bits   BS S/(N+1)8 bits  Service level prediction8 bits }}
As shown in Table 10, the MOB_MSSHO_REQ message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, and the 'N_Recommended' representing a result obtained by a scanning of a mobile subscriber station. Herein, as shown in Table 10, the 'N_Recommended' contains the identifiers of neighbor base stations, a CINR of a pilot channel signal for each of the neighbor base stations, and the level of a service predicted to be provided from the neighbor base stations to the mobile subscriber station.
Meanwhile, when the serving base station 640 receives the MOB_MSSHO_REQ message transmitted from the mobile subscriber station 600, the serving base station 640 detects a list of target base stations to which the mobile subscriber station 600 can be handed over by means of the 'N_Recommended' information of the received MOB_MSSHO_REQ message in step 623. Herein, for convenience of description, the list of target base stations to which the mobile subscriber station 600 can be handed over will be called a 'handover-executable target base station list'. In FIG. 6, it is assumed that a first target base station 660 and a second target base station 680 exist in the handover-executable target base station list. Also, the handover-executable target base station list may include a plurality of target base stations. In steps 625 and 627, the serving base station 640 transmits a handover notifications (hereinafter, referred to as HO_notifications) message to the target base stations (i.e., the first target base station 660 and the second target base station 680) contained in the handover-executable target base station list. Table 11 shows the structure of the HO_notification message and illustrated below.
TABLE 11SyntaxSizeNotesGlobal Header152-bit For (j=0;j< Num Records;J++){ MSS unique identifier48-bit48-bit unique identifier usedby MSS (as provided by theMSS or by the I-am-host-ofmessage) Estimated Time to HO16-bitIn milliseconds, relative to thetime stamp, value 0 of thisparameter indicates that noactual HO is pending Required BW 8-bitBandwidth which is requiredby MSS (to guaranteeminimum packet datatransmission) Required QoS 8-bitName of Service Classrepresenting AuthorizedQoSparamSet}Security fieldTBDA means to authenticate thismessageCRC field32-bitIEEE CRC-32
As shown in Table 11, the HO_notification message includes a plurality of IEs, that is, an identifier MSS ID of the mobile subscriber station 600 intending to perform a handover procedure to the first target base station 660 or the second target base station 680, an estimated start time of a handover by the mobile subscriber station 600, and information on the bandwidth requested from the mobile subscriber station 600 to a target base station which will become the new serving base station, and the level of a service that is to be provided to the mobile subscriber station 600. Herein, the bandwidth and the service level requested by the mobile subscriber station 600 are identical to the predicted service level information recorded in the MOB_MSSHO-REQ message described in Table 10 above.
Meanwhile, when the first target base station 660 or the second target base station 680 receive the HO_notification messages from the serving base station 640, they each transmit handover notification response (hereinafter, referred to as a HO_notification_response) messages, response messages with respect to the HO_notification message, to the serving base station 640 in steps 629 and 631, respectively. Table 12 shows the structure of the HO_notification_response message and is illustrated below.
TABLE 12SyntaxSizeNotesGlobal Header152-bit For (j=0;j< Num Records;J++){ MSS unique identifier48-bit 48-bit unique identifierused by MSS (as providedby the MSS or by theI-am-host-of message) QoS Estimated8-bitBandwidth which isprovided by BS(toguarantee minimumpacket datatransmission)TBDhow to set this field BW Estimated8-bitQuality of Service levelUnsolicited Grant Service(UGS)Real-time polling Service(rtPS)Non-Real-time pollingService nrtPS)Best effort ACK/NACK1-bitAcknowledgement orNegative acknowledgement1 is Acknowledgementwhich means that theneighbor BS accepts theHO_notificationmessage from the servingBS 0 is NegativeAcknowledgementwhich means that theneighbor BS may notaccept theHO_notification messagefrom the serving BS}Security fieldTBDA means to authenticatethis messageCRC field32-bit IEEE CRC-32
As shown in Table 12, the HO_notification_response message includes a plurality of IEs, that is, an identifier MSS ID (MSS unique identifier) of a mobile subscriber station intending to perform a handover procedure to target base stations, a response ACK/NACK regarding whether or not the target base stations can perform a handover according to the handover request of the mobile subscriber station, and bandwidth and service level information capable of being provided by each target base station when the mobile subscriber station is handed over to each target base station.
Meanwhile, the serving base station 640 having received the HO_notification_response messages from the first target base station 660 and the second target base station 680 analyzes the received HO_notification_response message, and selects a target base station, which can optimally provide the bandwidth and the service level requested by the mobile subscriber station 600 when the mobile subscriber station 600 is handed over, as a final target base station to which the mobile subscriber station 600 is to be handed over. For instance, when it is assumed that the service level capable of being provided by the first target base station 660 is smaller that that requested by the mobile subscriber station 600, and the service level capable of being provided by the second target base station 680 is identical to that requested by the mobile subscriber station 600, the serving base station 640 selects the second target base station 680 as a final target base station to which the mobile subscriber station 600 is to be handed over. Accordingly, the serving base station 640 transmits a handover notification confirmation (hereinafter, referred to as a HO_notification_confirm) message, a response message with respect to the HO_notification_response message, to the second target base station 680 in step 633. Table 13 shows the structure of the HO_notification_confirm message and is illustrated below.
TABLE 13SyntaxSizeNotesGlobal Header152-bit For (j=0;j< Num Records;J++){ MSS unique identifier48-bit48-bit universal MACaddress of the MSS(as provided to the BSon the RNG-REQ message) QoS Estimated 8-bitBandwidth which is providedby BS(to guarantee minimumpacket data transmission)TBDhow to set this field BW Estimated 8-bitQuality of Service levelUnsolicited Grant Service(UGS)Real-time polling Service(rtPS)Non-Real-time polling Service(nrtPS)Best effort}Security fieldTBDA means to authenticate thismessageCRC field32-bitIEEE CRC-32
As shown in Table 13, the HO_notification_confirm message includes a plurality of IEs, that is, an identifier MSS ID (MSS unique identifier) of a mobile subscriber station intending to perform a handover procedure to a selected target base station, and bandwidth and service level information capable of being provided by the selected target base station when the mobile subscriber station is handed over to the selected target base station.
Also, the serving base station 640 transmits a mobile subscriber station handover response (hereinafter, referred to as a MOB_HO_RSP) message, a response message with respect to the MOB_MSSHO_REQ message, to the mobile subscriber station 600 in step 635. Herein, the MOB_HO_RSP message contains information on a target base station to which the mobile subscriber station 600 is to be handed over. Table 14 illustrated below, shows the structure of the MOB_HO_RSP message.
TABLE 14SyntaxSizeNotesMOB_HO_RSP_message_Format( ) { Management Message Type=538 bits Estimated HO time8 bits N_Recommended8 bits For (j=0;j< N_NEIGHBORS;J++){  Neighbor BS-ID48 bits   Service level prediction8 bitsThis parameterexists only when themessage is sentby the BS }}
As shown in Table 14, the MOB_HO_RSP message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, an estimated start time of a handover procedure, and the 'N_Recommended' representing a result for target base stations selected by a serving base station. Herein, as shown in Table 14, the 'N_Recommended' contains identifiers of the selected target base stations and the level of a service predicted to be provided from each target base station to a mobile subscriber station. In FIG. 6, the MOB_HO_RSP message finally includes only target base station information on the second target base station 680 from among target base stations existing in the handover-executable target base station list. However, when there exist a plurality of target base stations capable of providing bandwidth and service level requested by the mobile subscriber station 600 from among the target base stations existing in the handover-executable target base station list, the MOB_HO_RSP message includes information on the plurality of target base stations.
Next, the mobile subscriber station 600 having received the MOB_HO_RSP message analyzes the 'N_Recommended' information contained in the MOB_HO_RSP message and selects a target base station to which the mobile subscriber station 600 is to be handed over. Then, the mobile subscriber station 600 having selected the target base station to which the mobile subscriber station 600 is to be handed over transmits a mobile subscriber station handover indication (hereinafter, referred to as a MOB_HO_IND) message, a response message with respect to the MOB_HO_RSP message, to the serving base station 640 in step 637. Table 15 illustrated below, shows the structure of the MOB_HO_IND message.
TABLE 15SyntaxSizeNotesMOB_HO_IND_message_Format( ) { Management Message Type=54 8 bits TLV Encoded InformationVariableTLV specific Target_BS_ID48 bits}
As shown in Table 15, the MOB_HO_ND message includes a plurality of IEs, that is, the 'Management Message Type' representing the type of a transmitted message, the 'Target_BS_ID' representing an identifier of a target base station selected by a mobile subscriber station, and the 'TLV Encoded Information' representing extra information in addition to the information.
Meanwhile, in step 639, the serving base station 640 having received the MOB_HO_ND message recognizes that the mobile subscriber station 600 is handed over to the target base station (i.e., the second target base station 680) contained in the MOB_HO_IND message, and then releases a link currently setup with the mobile subscriber station 600. In this way, when the link with the serving base station 640 is released, the mobile subscriber station 600 performs a handover procedure to the second target base station 680 in step 641.
Hereinafter, a handover process by the request of a base station in the conventional IEEE 802.16e communication system will be described with reference to FIG. 7.
FIG. 7 is a flow diagram illustrating the handover process by the request of the base station in the conventional IEEE 802.16e communication system.
Before describing FIG. 7, the handover process by the request of the base station occurs when the base station is overloaded and requires some type of load-sharing for dispersing the load of the base station, or the base station must cope with the change of the uplink status of a mobile subscriber station.
Referring to FIG. 7, first, a serving base station 740 transmits a MOB_NBR_ADV message to a mobile subscriber station 700 in step 711. Then, the mobile subscriber station 700 receives the MOB_NBR_ADV message and obtains information on neighbor base stations. Further, in step 713, the mobile subscriber station 700 transmits a MOB_SCN_REQ message to the serving base station 740 when the mobile subscriber station 700 intends to scan the CINRs of pilot channel signals transmitted from the neighbor base stations. Herein, since a time point at which the mobile subscriber station 700 requests a scanning has no direct relation to a scanning operation for the CINR of the pilot channel signal, a detailed description about the time point will be omitted. In step 715, the serving base station 740 having received the MOB_SCN_REQ message transmits the MOB_SCN_RSP message, which contains information to be scanned by the mobile subscriber station 700, to the mobile subscriber station 700. In step 717, the mobile subscriber station 700 having received the MOB_SCN_RSP message containing the scanning information performs a CINR scanning of pilot channel signals with respect to neighbor base stations, which has been recognized through the reception of the MOB_NBR_ADV message, according to parameters (i.e., scan duration) contained in the MOB_SCN_RSP message.
Meanwhile, when the mobile subscriber station 700 managed by the serving base station 740 determines to perform a handover procedure by its own handover necessity in step 719, the serving base station 740 transmits the HO_notification messages to neighbor base stations 760 an 780 in steps 721 and 723. Herein, the HO_notification message contains information on a bandwidth and the level of a service which must be provided by a target base station to be a new serving base station of the mobile subscriber station 700. In FIG. 7, it is assumed that the neighbor base stations of the serving base station 740 are two base stations, that is, the first target base station 760 and the second target base station 780.
In steps 725 and 727, the first target base station 760 and the second target base station 780 receive the HO_notification messages respectively, and transmit the HO_notification_response messages, response messages for the HO_notification messages, to the serving base station 740. As described in Table 12, the HO_notification_response message contains a response ACK/NACK regarding whether or not the target base stations can perform a handover procedure requested by the serving base station 740, and bandwidth and service level information capable of being provided to the mobile subscriber station 700.
Next, after receiving the HO_notification_response messages from the first target base station 760 and the second target base station 780, the serving base station 740 then selects target base stations capable of providing the bandwidth and the service level requested by the mobile subscriber station 700. For instance, when it is assumed that the service level capable of being provided by the first target base station 760 is smaller than that requested by the mobile subscriber station 700, and the service level capable of being provided by the second target base station 780 is identical to that requested by the mobile subscriber station 700, the serving base station 740 selects the second target base station 780 as a final target base station to which the mobile subscriber station 700 is to be handed over. Further, the serving base station 740 having selected the second target base station 780 as the final target base station transmits a HO_notification_confirm message, which is a response message for the HO_notification_response message in step 729.
Next, after transmitting the HO_notification_confirm message to the second target base station 780, the serving base station 740 transmits a MOB_HO_RSP message to the mobile subscriber station 700 in step 731. Herein, the MOB_HO_RSP message contains N_Recommended information selected by the serving base station 740, that is, selected target base stations e.g., in FIG. 7, the second target base station 780) and the bandwidth and the service level capable of being provided from the target base stations to the mobile subscriber station 700. The mobile subscriber station 700 having received the MOB_HO_RSP message recognizes the a handover has been requested by the serving base station 740, and selects a final target base station to which the mobile subscriber station 700 is to be handed over with reference to the N_Recommended information contained in the MOB_HO_RSP message. After selecting the final target base station, the mobile subscriber station 700 transmits a MOB_HO_IND message, a response message for the MOB_HO_RSP message, to the serving base station 740 in step 733. Then, in step 735, the serving base station 740 having received MOB_HO_IND message recognizes that the mobile subscriber station 700 is to be handed over to the target base station contained in the MOB_HO_IND message, and then releases a link currently setup with the mobile subscriber station 700. In this way, when the link with the serving base station 740 is released, the mobile subscriber station 700 performs a handover procedure to the second target base station 780 in step 737.
As described above, in the currently proposed handover procedure in the IEEE 802.16e communication system, a serving base station collects information of neighbor base stations, transmits a HO_notification message, and collects information necessary for the handover. Then, the serving base station receives a HO_notification_response message as a response of the HO_notification message, and transmits a MOB_HO_RSP message containing information of target base stations to which a mobile subscriber station can be handed over to the corresponding mobile subscriber station. Meanwhile, the mobile subscriber station determines a base station to which the mobile subscriber station is to be handed over from a list of target base stations, to which the mobile subscriber station can be handed over, contained in the MOB_HO_RSP message, and then transmits a MOB_HO_IND message containing information on the determined base station to the serving base station. Then, the mobile subscriber station releases a current connection with the serving base and tries to connect with the determined base station.
As described above, only a simple procedure for a handover is defined up to now. However, various circumstances may exist which have been not described in the procedure in a broadband mobile communication service of actual various radio environments. For instance, there may occur a case in which the serving base station must forcedly cause the subscriber station to perform a handover procedure according to the resource condition of the serving base station, or special circumstances such as the rejection of the subscriber station for a handover requested by the serving base station. Also, there may occur a case in which the movement direction of the subscriber station changes while being handed over to a target base station, and the subscriber station must cancel the handover procedure in order to connect to an original serving base station again.
However, the conventional broadband mobile communication system has not yet presented methods for solving the circumstances which may occur as described above. Additionally, when the conventional method is applied to the aforementioned circumstances, it is ineffective and further, the performance of the system may be substantially reduced.

This patent is subject to a terminal disclaimer.

Method for compulsorily performing handover in broadband wireless communication system


A power supply system offshore plant comprises: a generator; an AC/DC converter converting, AC generated from the generator into DC to supply the direct current to a DC bus; a power load connected to the DC bus to generate regenerative power; a first power storage unit for storing power when a voltage of the DC bus is maintained at a level of a first threshold value or higher for a first time period, and supplying the stored power to the DC bus when the voltage of the DC bus is maintained at a level of a second threshold value or lower for a second time period; and a first resistance unit for consuming power when the voltage of the DC bus is maintained at the level of the first threshold value or higher for a third time period. The third time period is longer than the first time period.

With rapid industrialization and industrial development, consumption of resources such as petroleum has increased, and stable production and supply of oil have become a crucial global problem.
For this reason, development of smaller marginal fields or deep-sea oil fields, which has been ignored due to lack of economic feasibility, is now emerging. Thus, development of offshore plants provided with oil drilling equipment suitable for use in such oil fields is actively carried out along with development of seabed mining technology.
An offshore plant is provided with various types of drilling-related equipment such as a Derrick crane system, a draw-works, a top drive, a mud pump, a cement pump, a riser, and a drill pipe.
The draw-works performs lifting of the drill pipe, insertion of a casing, and the like, and includes a drum and a motor. The drum is powered by the motor so as to wind or unwind a wire rope for controlling lifting of the drill pipe. The rotational speed of the motor can be adjusted so as to adjust the rotational speed of the drum, thereby enabling adjustment of the speed of the drill pipe.
The top drive provides power for drilling and pipe fastening in drilling operation.
Offshore plants are divided into a stationary platform anchored at one point of nearshore to perform drilling operations and a floating offshore plant capable of performing drilling operation at ocean depths of 3,000 m or more.
The floating offshore plant is provided with a plurality of thrusters as a main propulsion device or a propulsion device for computer-aided dynamic positioning. The thrusters are located at the bottom of a ship to change an operating direction of a propeller and are commonly used to allow the ship to navigate or to sail in a canal or enter/leave a port under its own power without a tug. The thruster is powered by a thrust motor connected thereto.
FIG. 1 is a diagram of a typical power supply system known in the art.
Referring to FIG. 1, AC power generated by a power generator 110 is supplied to an AC bus, to which a first AC/DC converter 121, a second AC/DC converter 122, and a third AC/DC converter 123 are connected.
The first AC/DC converter 121 converts alternating current supplied from the AC bus into direct current and supplies the direct current to a first DC bus 131, and a DC/AC converter 141 converts direct current supplied from the first DC bus 131 into alternating current and supplies the alternating current to a first thruster motor 151.
The second AC/DC converter 122 converts alternating current supplied from the AC bus into direct current and supplies the direct current to a second DC bus 132, and a DC/AC converter 142 converts direct current supplied from the second DC bus 132 into alternating current and supplies the alternating current to a second thruster motor 152.
The third AC/DC converter 123 converts alternating current supplied from the AC bus into direct current and supplies the direct current to a third DC bus 133, and a plurality of DC/AC converters 143 to 148 are connected to the third DC bus 133. The plurality of DC/AC converters 143 to 148 convert direct current supplied from the third DC bus 133 into alternating current and supply the alternating current to corresponding ones of a plurality of draw-works motors 153, 154, 155, 158, 159 and a plurality of top drive motors 156, 157.
Since the draw-works motors 153, 154, 155, 158, 159 and the top drive motors 156, 157 are configured to repeatedly lift or lower drilling equipment such as a drill pipe, a brake is frequently put on the motors to bring the motors to a sudden stop or to rotate the motors in a reverse direction during rotation at rated load, and, for the thruster motors 151, 152, a brake is also frequently put on the motors to bring the motors to a sudden stop or to rotate the motors in the reverse direction during rotation at rated load. When a brake is put on the motors, regenerative power is generated in the motors. In addition, when a thruster is rotated due to a disturbance, regenerative power is also generated in the thruster motors.
When regenerative power is generated in the draw-works motors, the top drive motors, or the thruster motors, voltage of a DC bus connected to the draw-works motors, the top drive motors, or the thruster motors is increased, and, when the voltage is increased beyond a degree which the DC bus can accommodate, the DC bus is tripped.
Thus, the typical power supply system is provided with resistors 161 to 166 to consume regenerative power as heat, thereby preventing the DC bus from tripping.
FIG. 2 is a graph showing power consumption of each component of a typical power supply system known in the art.
Referring to FIG. 2, electric power produced by a power generator is supplied to a first load 220 and an AC/DC converter 260 through a distributor. The AC/DC converter 260 converts alternating current into direct current and supplies the direct current to a second load 240 while supplying the direct current to a draw-works 230 through a DC/AC converter. Each of the first load 220 and the second load 240 is a load that consumes a constant level of electric power. On the contrary, power consumption of the draw-works 230 changes continuously, and, in FIG. 2, a negative value of electric power means that regenerative power is generated. Regenerative power generated in the draw-works 230 is consumed by the second load or a resistor 250.
In FIG. 2, it can be seen that abrupt change in power consumption of the draw-works 230 causes abrupt change in power output of the power generator 210. A diesel power generator consumes more fuel and discharges more exhaust gas in the case where power output is maintained at a constant level than in the case where power output is abruptly changed.
In order to supply suitable electric power corresponding to abrupt change in power consumption of the draw-works motors, the top drive motors, and the thruster motors, it is necessary to rapidly change power output of the power generator. However, the power generator has difficulty providing suitable electric power corresponding to abrupt change in power consumption of the draw-works motors, the top drive motors, and the thruster motors due to low responsiveness thereof. If suitable power supply to the draw-works motors, the top drive motors, and the thruster motors is not achieved, a dangerous situation can occur due to characteristics of drilling operation. Further, when power supply to the draw-works motors or the top drive motors is suddenly interrupted upon loss of power, a dangerous situation can also occur.
In other words, typical power supply systems have problems such as energy waste due to consumption of regenerative power by resistors, increase in fuel consumption and exhaust gas due to abrupt change in power output of a power generator, difficulty in suitable electric power supply to draw-works motors, top drive motors, and thruster motors, and danger upon loss of power.

Apparatus and method for supplying hybrid power of offshore plant

DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD.


The present invention comprises a test set-up (20) and method of testing a correlated double sampling circuit (CDS) (24) by using a sinusoidal test signal (22) for measuring linearity. The present invention generates a sinusoidal signal with two accurate and known levels at two different time points, as an input to the CDS. The cosinusoidal output of the CDS is then processed using an ADC (60) and processor (62) to check the functionality and linearity of the CDS circuit under test.

Correlated double sampler (CDS) circuits are used extensively in CCD imaging systems for both scientific and commercial imaging systems. Testing a CDS circuit and characterizing it for linearity at high resolutions and speeds is a challenging task, touching the limits of existing technology. This is especially true with the introduction of 12-bit frontends for CCD imaging systems at speeds up to 21-MSPS for the commercial end equipment market. The task is complicated by the way a CDS is required to sample its input, the CCD waveform as shown at 10 in FIG. 1.
The CDS samples at two different points t1 and t2 separated at a fixed distance in time T at a given rate. Thus, in each cycle of the input waveform, the CDS is required to sample at two given points in time and give an output proportional to the difference in the voltage levels at these two points. These two points correspond to the reset level 12 of the signal and the video level 14 of the signal. The output in this case was given to an internal 14-bit ADC and the ADC digital output was checked for linearity using static tests.
Testing such a circuit for linearity requires an input voltage waveform with two accurate and known levels at two given time points at the given repetition frequency. Moreover, the voltage level of this waveform should be accurate to at least a couple of LSBs more than the resolution of the CDS, so that the overall performance is limited by the CDS rather than by the input source. In addition, this waveform requires the video level to be changing in a discrete ramp fashion from cycle to cycle so that what we see at the CDS output would be a ramp. This aids in conveniently figuring the CDS linearity, conventionally performed using a simple histogram technique.
But, this ramp "modulation" also presents the greatest challenge in generating such a waveform. Other methods may involve input sources other than the exact waveform previously described and indirect interpretation of the accrued results. Additional constraints imposed by the nature of the CDS input circuitry and requirements arising from the limitations of the CDS input circuit further complicate the test process.
Although it is possible to do away with such special waveform requirements by including a sample-and-hold type test circuit in the CDS, this disrupts the normal functioning of the CDS. This introduces additional unwanted parasitic elements in the signal path, which is not desirable for such a high-resolution system.
Schemes also exist where the test-mode input pins to the CDS are brought out separately through the required additional components. But these schemes are unsatisfactory in that they do not test the actual signal path on which the CDS operates. They also require additional pins on the package.
There is desired a methodology of testing the CDS linearity at high resolution and high speed while aiming for the minimum test cost. The testing method should be repeatable and worthy of production testing.

Innovative method of correlated double sample (CDS) circuit testing


Apparatuses and methods for positioning a flexible hose into a wellbore with a protective housing are disclosed. A flexible hose is contained within a protective housing and both are positioned into a wellbore to a desired depth. Pressure can be applied to an interior of the protective housing, and a packoff seals between the flexible hose and the protective housing, causing the pressure to eject the hose from the protective housing.

Radial drilling is used to drill small-diameter horizontal wellbores. With this coiled tubing conveyed drilling technique, new wellbores are drilled perpendicular from the mother bore and into the reservoir formation. In a cased wellbore, a special cutting bottom hole assembly (BHA) is used to drill a hole in casing. This BHA is run through a jointed tubing workstring equipped with a deflector shoe that points sideways into casing when lowered downhole. The cutter BHA consists of a downhole positive displacement motor, a flexible driveshaft and a drill bit. The flexible driveshaft is designed to bend inside a short-radius curvature channel in the deflector shoe, transmit the force and torque from the PDM to the drill bit.
After the flexible drive shaft and mill have pierced a hole thru the casing and begun to create a new channel often called a radial wellbore or radial channel or radial arm from the mother wellbore—a variety of techniques could be used to extend this radial wellbore.
One of the techniques that could be used is to extend the wellbore with a hydraulic drilling method. In this method hydraulic horsepower is delivered to a nozzle that is fed through the deflector shoe and to the point where the flexible shaft and/or mill stopped progressing. Sufficient hydraulic power to cut into formation and extend the shaft is supplied to the nozzle and the nozzle is moved further into the wellbore cutting forward with hydraulic power.
FIG. 1 is an illustration of a radial jet drilling assembly according to the prior art. Radial jet drilling has been used to create a radial arm in formation rock from a mother well. In this arrangement a flexible hose is conveyed into a wellbore by gravity. The flexible hose, often approximately 300′ in length, is attached to a more rigid steel tubing. Generally the formation rocks are relatively shallow so the rigid steel tubing is small in size relative to conventional coiled tubing (often approximately ⅝″ size). The flexible hose is attached to this rigid steel tubing and lowered into the wellbore such that gravity can allow the hose to fall axially to the start of the diverter shoe (deflecting shoe in FIG. 1). The hose has a nozzle head that can direct high pressure jets into the formation rock and cut thru that formation creating a channel. In most instances the nozzle head itself is "self-propelled," meaning there is more flow directed backward away from the front of the radial hole compared to forward. Thus the net momentum of the fluid jets creates a force that helps drive the nozzle forward/radially into the formation.
A propulsion method is often necessary when attempting to reach extended depths within a non-vertical wellbore. Use of larger diameter tubing with greater relative stiffness is often utilized to offset a portion of the mentioned propulsion requisite. Flexible objects which are far less rigid in nature such as a hose connected to the distal end of coiled tubing will often require a propulsion method which imparts tension to and assists the less rigid objects along the well trajectory. In the scenario of attaching a flexible hose to the end of a conventional coiled tubing string, the hose itself can become entangled or damaged while conveying to the bottom of a long or tortuous wellbore. To overcome this the end of the hose is fitted with rubber/flexible cup elements as shown in FIG. 2. With the cup elements resting on the bottom of the flexible hose fluid can be pumped into the wellbore in the annular space between the coiled tubing and the mother wellbore such that there is a pressure drop as that fluid passes over the flexible rubber cups. This pressure drop keeps the flexible hose in tension below coiled tubing. Maintaining tension on the flexible hose despite conveying that hose into a deviated wellbore is advantageous because as long as tension is maintained on the hose by means of pumping over cups or (any other upset) the hose is far less likely to be damaged during the conveyance process.


An image-based refractive index measuring system comprises an optical device and an electronic device. The optical device is used to guiding an external light which is passed through an analyte. The electronic device comprises an image capture module, an image analyze module and a display module. The image capture module generates a first image by capturing the external light source. The image analyze module connects to the image capture module to receive the first image, and analyzes the first image in order to generate an analytical result comprising the refractive index of the analyte. The display module connects to the image analyze module to receive and display the analytical result.

1. Field of the Invention
The present invention relates to a measuring system, in particular to an image-based refractive index measuring system.
2. Description of the Related Art
Currently, the applications of the refractive index are relatively extensive, for example, a sugar meter that measures the juice sweetness or measures the water salinity that both may use the principle of refraction. The conventional sugar refractive index meter or the refractometer in circulation such as the refractometers disclosed by Republic of China Patent D111526 or D127363. The refractometer is basically a round pipe body that a duckbill shaped portion of the front end is a measure end, which having a head shaped lift cover and having a rectangular lens therein, the round pipe body may drop the liquid into the lens, and the intermediate round pipe body is a gripping portion, the terminal end is a drum-shaped eyecup end, which may view the scale on the lens to know the predicting refractive index or the concentration. In the conventional technology, the user has to visually interpret the scale on the lens by the eye, so as to know the predicting refractive index and the concentration of the predicting analyte. In the long-term use of the environment, it is easy to cause the occupational injury for the user's eyes.
In addition, the sugar detection meter in the Republic of China Patent M398117 and the juice sweetness detection device in the Republic of China Patent M395161, are arranged for measuring the refractive index by the optical manner. However, the sugar detection meter uses the grating spectrometer parts and the infrared detection element architecture, which lead to the complexity of the system design and costly. Therefore, it is more complex in manipulation and the higher cost is the biggest deficiency while using such type of meter.

Image-based refractive index measuring system


To provide a system by which evaluation of circumstances of contamination by microparticles having nucleic acid can be performed rapidly and accurately. The theme is achieved by a system for measuring microparticles that includes: (1) a microparticle adhesion step of adhering the microparticles having nucleic acid to a microparticle adhesion member; (2) a membrane breakage step of breaking membranes of the adhered microparticles by electrical discharge; (3) an electrophoresis step of electrophoresing the microparticles in a thickness direction of a gel to make the nucleic acid in the microparticles migrate from a negative electrode side toward a positive electrode side and adhere the nucleic acid on a surface of a nucleic acid detection member; and (4) a nucleic acid measurement step of fluorescently staining the surface of the nucleic acid detection member to measure a concentration of the nucleic acid.

From before, there have been needs to examine circumstances of contamination by microorganisms in air and on wall surfaces and floor surfaces of hospitals, food factories, and other locations where particular attention must be paid to sanitation as well as to examine circumstances of contamination by microorganisms of utensils and clothing used for surgery and food manufacturing (Non-Patent Document 1). In a conventional method, a sample is coated as a solution onto a culture medium or a membrane having a plurality of cells fixed thereon, formation of colonies by a microorganism or loss of the cells spread in the form of the membrane due to a virus is made to occur, and evaluation is performed by counting the number of colonies or number of loss (Non-Patent Document 2).
Meanwhile, by advances made in single-molecule DNA manipulation and measurement arts through progress of technical development in recent years, it has become possible to make clear observations by fluorescently staining of single-molecule DNA (Non-Patent Document 3). Using this art, it is becoming possible to take out a DNA molecule from a cell, extend and fix the DNA molecule on a substrate, and adhere a fluorescently stained restriction enzyme to the extended and fixed DNA to prepare a restriction map using a fluorescence microscope (Patent Document 1 and Non-Patent Document 4).    Patent Document 1: Japanese Published Unexamined Patent Application No. 2003-200400    Non-Patent Document 1: U Yanagi: "Behavior of bio-aerosol in office buildings and methods of control," Green Technology, vol. 17, No. 5, 44-47, 2007    Non-Patent Document 2: Sumiyo Ishimatsu: "Capture and detection of airborne microorganism particles," Green Technology, vol. 17, No. 5, 48-51, 2007    Non-Patent Document 3: Morikawa K., and Yanagida M., J. Biochem., 89, pp. 693-696, 1981    Non-Patent Document: A. Bensimon, A. Simon, A. Chiffaudel, V. Croquette, F. Heslot, D. Bensimon, "Alignment and sensitive detection of DNA by a moving interface," Science, Vol. 265(5181), pp. 2096-2098, 1994

Method of measuring microparticles having nucleic acid and apparatus therefor


A logic which enables implementation of a 80-bit wide or a 96-bit wide cache SRAM using the same memory array. The logic implementation is accomplished by merging tag, and data into an order block of information to maximize bus utilization. The logic reduces the bus cycles from four cycles for an 80-bit to three cycles for a 96-bit implementation.

The performance of computer systems, especially personal computers, has improved dramatically due to the rapid growth in computer architecture design and in particular to the performance of computer memory.
Computer processors and memories however have not pursued the same pace of development through the years. Memories are not able to deliver enough response speed to processors. To reduce the gap in speed between the processors and memories, the concept of memory hierarchy was introduced. A memory hierarchy comprises a number of different memory levels, sizes and speeds. The memory located near or inside the processor is usually the smallest and fastest and is commonly referred to as cache memory. Cache memory needs to be fast to accommodate the demand of the processor therefore it is usually constructed from static-type memory or static random access memory (SRAM).
Cache memory plays an important role in the computer memory hierarchy. Computer instructions and data which are most likely to be reused are stored temporarily in the cache memory because the processor can access these instructions or data much faster than accessing them from the slower computer main memory.
Almost all of cache memories are managed by hardware meaning that the cache operation is physically controlled by logic circuits. Implementation of cache memory is not the same in different type of processors since the logic control circuits are different. In some implementations, a processor-cache interface uses a 64-bit bus for data and an additional bus for tag. The tag bus width varies, but has nominally been 16 bits for a total of 80 bits wide for tag plus data. If the cache block (or cache line) size is four times the data bus width, then no useful information appears on the tag bus for three out of every four bus cycles therefore the bus is not utilized efficiently.
There is a need for a logic to implement a cache SRAM so that the utilization of data and tag bus can be more efficient. This logic could implement a 64-bit data bus plus a 16-bit or more tag bus but the same logic is also usable to implement a 96-bit bus.

Word selection logic to implement an 80 or 96-bit cache SRAM


This invention relates to a Christmas light assembly and more particularly to the one which includes a lamp base comprising divided strips to flexibly match with the outer diameter of bulb so as to let bulb be firmly retained therein. The divided strips are having projecting inner wall portions with a longitudinal scoop channel set between each two projecting inner wall portions for draining of water. The lamp base also comprises two resilient hook members to respectively engage with the upper flange of a lamp holder when it is inserted therein, so as to reinforce the connection.

1. Field of The Invention
Christmas light sets are commonly used everywhere in the world during Christmas holidays, as an ornamental item either indoor or outdoor.
This invention is related to a kind of Christmas light assembly and more particularly to the one which is generally comprised of a lamp bulb set in a lamp base and firmly retained by a lamp holder.
2. Description of the Prior Art
Regular Christmas light assembly, as shown in FIG. 1, is generally comprised of a lamp bulb, a lamp base and a lamp holder. Drawbacks of regular Christmas light assembly may include the following:
(1) Because the tolerance of the outer diameter of the lamp bulb is normally set within about .+-.0.2 mm and the inner diameter of the lamp base must be large enough to receive the outer diameter of the lamp bulb, the lamp bulb may be not firmly retained in the lamp base, and the two conductive wires of the lamp bulb may be twisted to cause short-circuit.
(2) Because basic tolerance in size is inevitable and the plastic material tends to the deform following the change of temperature, the lamp base is easy to break away from the lamp holder.
It is therefore, the scope of the present invention to improve the said problems and to reduce percent defective in the production of Christmas light assembly.

Innovative structure of christmas light assembly


Embodiments of the disclosure include a computer implemented system including at least one processor and memory storing instructions. In one embodiment, a system receives a batch identifier, determines a number of containers, sends the number of containers to a user device, and receives a first container identifier from a user device. The system retrieves a location identifier of a first item, sends the location identifier to the user device, and receives a physical location identifier from the user device. The system sends to the user device the first item when the physical location identifier matches the location identifier. The system receives a physical item identifier of the first item and sends a destination to the user device to bring the container.

E-commerce business is wide-spread for its convenience, and items that can be ordered electronically is various in kind. Because of the enormous number of items in a warehouse and complexity of orders, workers in a warehouse face inefficiency issues. In fact, various systems for picking items already exist to solve this issue.
The existing systems, however, are rudimentary in that they control picking tasks on an order-basis. That is, under existing systems, workers pick items until they complete picking every item in each order, regardless of where the ordered items are shelved in a warehouse. Considering the numerosity of items and space of a warehouse, these systems may waste time and labor of workers, especially when the ordered items are shelved physically far apart. Moreover, existing systems cannot effectively control workers' picking steps because they cannot effectively communicate with a central system while workers are picking items. For example, existing systems could not confirm whether workers are in the right location and/or whether workers have picked the right item in a warehouse. Therefore, there is a need for improved systems and methods for controlling fulfillment of order efficiently in an electronic manner.

Computerized systems and methods for assisted picking processes


A magnetic recording and reproducing apparatus for use with a tape cartridge including a single tape reel having a compact drive and winding reel arrangement.

One magnetic recording and reproducing apparatus used for backing up information as a computer peripheral equipment is of type of guiding and driving a magnetic tape on a single tape reel in a tape cartridge commonly called "IBM 3480" magnetic tape cartridge to a winding reel disposed in the magnetic recording and reproducing apparatus along a predetermined tape running path, as disclosed in Japanese Patent Application Laying-Open Gazzette No. 171,773/1983, for example. In such an apparatus, the magnetic tape contained in the tape cartridge has a leader block provided at its leading end while the magnetic recording and reproducing apparatus has leader block guide and drive means to draw out the leader block to the winding reel. Such an apparatus is disclosed in Japanese Patent Application Publication No. 42,539/1985, for example.
Present computers are so designed as to be physically provided with 51/4 inch Winchester disk drive or 51/4 inch floppy disk drive. These drives are so constructed as to meet the industrial standard in which they have a width of 53/4 inch, a height of 31/4 inch and a length of 8 inch. Such a size is called 51/4 inch form factor in the computer industry.
On designing the magnetic recording and reproducing apparatus, such components as the winding reel, a magnetic head, guide rollers and the leader block guide and drive means are required to have a reasonable layout in order to compact the magnetic recording and reproducing apparatus while it meets the aforementioned form factor. However, the prior magnetic recording and reproducing apparatus has failed to have the appropriate layout, which inhibits its compactness.

Drive and winding reel arrangement in a magnetic recording and reproducing device


An optical disc medium indexing system having a plurality of elongated parallel tracks wherein each track contains a nonerasable index portion located in less than a single frame. The index portions are formed on the substrate of the disc by a plurality of indentations representing the absolute address of each track on the disc recorded in a multiplex format. Each index portion containing information on the mark, track number and CRC. The disc is constructed so that information may be recorded on the entire surface of the medium including the indexed portions.

1. Field of the Invention
The present invention generally relates to a disc-shaped information carrier medium such as an optical disc or a magneto-optical disc and, more particularly, to the format of an index region of the information carrier medium.
For the purpose of the present invention, the term "optical disc" hereinafter referred to and used in the appended claims is to be understood as including not only a compact optical disc, but also a magneto-optical disc.
2. Description of the Prior Art
Conventional optical disc, typically contain at least one index region having an index such as the track number provided for each track on the optical disc.
According to the prior art, only the index is recorded in the index region. Therefore, the provision of an index region correspondingly reduces the information storage capacity of the optical disc as a whole. In addition, where the disc contains a substantial amount of information such as a long-time music or video recording or playback such use necessitates a memory buffer for the index region. Which buffer is required to have a relatively large storage capacity making it impossible, or impractical to record the information involving a long-time video or music recording or playback.
In particular, the problem associated with the recording large amounts of information such as the long-time recording or playback has obstructed the development of an digital audio disc or video disc having a capacity large enough to accommodate such information.
In order to eliminate the above discussed problems, the information can be recorded on the index region in a multiplex recording fashion.
However, it has been found that multiplex recording of information on a index region of the optical disc often causes a considerable reduction in signal reproduction quality and cannot provide a support for an error correction.

Optical recording medium track indexing system