A universal rake receiver architecture includes modular independent processing units that can be flexibly programmed to support different modes of operation. The processing units are capable of performing the basic correlation calculations of DS-CDMA and each unit has an internal local memory and controller that controls its mode of operation. Each unit performs the required synchronization and demodulation operations for a multipath of a signal in the digital domain using all-digital frequency and timing correction techniques. Frequency feedback need not be supplied to the analog section of the receiver. Interpolation most preferably is used to find the optimum sampling position of each incoming chip. This independence allows the receiver to be used with one to several antennas without design modifications.

1. Field of the Invention
The present invention relates to a rake receiver with a flexible architecture suitable for demodulating direct sequence code division multiple access (CDMA) communications or other types of CDMA communications.
2. Description of the Related Art
Aspects of this disclosure relate to code division multiple access (CDMA) technology. CDMA technology is presently used in a number of wireless communication applications including cellular telephone networks. Other applications of CDMA technology include satellite communications, some global positioning communication systems and wireless LANs and WANs using CDMA modems. CDMA is a spread spectrum technique that spreads a signal over a frequency band to achieve more robust and efficient communication. Typically a signal transmitted using CDMA is spread in frequency with a pseudonoise (PN) code. A PN code generally is expressed as a characteristic set of binary valued chips defined over a range of frequencies spanning the bandwidth of the communication channel. Direct sequence spread spectrum (DSSS) modulation techniques multiply a signal to be transmitted with the PN code that identifies the user or communication link and transmits the resulting modulated signal. Using the spreading code to expand the spectrum of the signal is the code division part of CDMA communication. The multiple access aspect of CDMA reflects the fact that multiple users can use the same bandwidth at the same central frequency for communication.
Multiple users can communicate over the same frequency band of a CDMA link because each of the users is assigned a different PN code and that user's signals are modulated with their assigned PN code prior to transmitting the signals over the network. Receivers despread and detect a particular user's signal according to the assigned or expected PN code. PN codes are nearly orthogonal and so can be used to identify users present on a single channel using the same frequency band. Often the communication between a base station and a mobile handset is accomplished over two channels having similar bandwidth characteristics but separated in frequency so that full duplex communication can proceed. This might be true whether the network is used for cellular telephony or a wireless LAN or WAN application. Because these channels are separated in frequency, the same PN code can be used to spread the user's signals on the two non-overlapping bandwidths of the two channels.
In a typical cellular telephone network, both the base station and the handset transmit and receive signals. The transmitted signals may vary significantly in power and quality because of the physical characteristics and limitations of the base station and the handset. Received signals can be of varying amplitudes with varying levels of noise. In such a cellular network, the separation between the cellular base station and the handset can vary significantly, particularly since the handset may be in an automobile. The range of amplitude variations can be large. Variations in receiver and transmitter position exist in other applications but are pronounced in cellular telephone applications and mean that a receiver may need to recover signals whose magnitude varies considerably.
Another challenge of cellular telephony is that of multipath propagation. When the cellular telephone network is within an urban environment or other environments with significantly varying terrain, a signal travelling between a base station and a handset may reach the receiver directly or after having reflected off of a building or other objects. Different portions of the signal may propagate along significantly different paths and a number of these different paths may be received at a receiver at substantially the same time. Different multipaths experience different levels of attenuation, phase delay and can arrive at different angles. Wireless communication subject to multipath propagation exhibits significant variations in received signal characteristics for small changes in the relative position of the receiver. These rapid variations for small changes in position are known as Rayleigh fading due to the power distribution of the received signal under such conditions. Because it uses a spread spectrum, CDMA communication has natural advantages in reducing the problems associated with multipath propagation. Diversity reception within the CDMA system can be used to achieve still better performance.
Diversity reception refers to the process whereby multiple receive channels are used to recover different portions of a signal. In the case of multipath propagation, the receiver might include two independent receiving channels. The two independent receive channels might be assigned to the two strongest multipaths that arrive at the receiver. Processing is performed to align the two strongest multipaths and the two multipaths are added according to an appropriate weighting scheme. Overall signal strength and signal to noise properties are improved. The rake receiver architecture is especially well suited to performing this form of diversity reception.
For multipath discrimination to be possible in the CDMA system, there should be a minimum separation between the times when the multipath signals are received. The minimum separation should be at least one chip in the PN sequence. When there is at least one chip difference in the reception time between two multipath signals there will be at least one chip of offset between the embodied PN codes. In CDMA systems, the PN codes are selected so that two PN codes separated in time by at least one chip have very low cross correlation and so can be treated as independent signals and processed accordingly so that the signals can be combined. This minimum difference in reception time or chip duration of course varies for different systems but is such that in most urban settings appropriate delays will exist between multipaths to make diversity reception generally advantageous.
Mobile receivers such as handsets or terminals identify base stations according to pilot signals transmitted by base stations. Pilot signals have particular characteristics that make them particularly well suited to identify appropriate base stations for the mobile receiver's communication and to allow the mobile receiver to detect aspects of the base station's identification, system timing and control signals. Information from the pilot signal is used by the mobile receiver to synchronize to the timing of the base station. Pilot signals are used to distinguish between different base stations, thus enabling the mobile terminal to accurately identify a specific base station and establish communication. Receivers generally identify the strongest pilot signal as the appropriate one to acquire and initiate communications with the corresponding base station.
PN codes used in present implementations of CDMA communication are sufficiently close to orthogonal to identify a given signal traveling through different multipaths to a receiver. Because they are not fully orthogonal, PN codes are not generally adequate to separate different data streams for a single user. Orthogonal codes are used for that purpose. For example, the pilot signal is spread by a specific orthogonal code while the data and control streams for a user may be spread by other orthogonal codes. When the base station transmits user signals to a mobile receiver, the user signals are modulated depending on the specific communication scheme in use. The orthogonal coding used for different communication links is generally set by standard, vary among different applications, and are expected to continue to evolve over time.
Rake receivers are known in the art. Useful illustrations of conventional aspects of rake receivers are provided, for example, by U.S. Pat. No. 5,764,687 entitled "Mobile Demodulator Architecture for a Spread Spectrum Multiple Access Communication System," which patent is hereby incorporated by reference in its entirety. Aspects of conventional rake receivers are discussed here with reference to FIG. 1, which illustrates aspects of U.S. Pat. No. 5,764,687. Further aspects of rake receivers are illustrated in U.S. Pat. No. 5,903,550 entitled "Method and System for Parallel Demodulation of Multiple Chips of a CDMA Signal." This patent is similarly incorporated by reference in its entirety for its teachings regarding aspects of the implementation and operation of rake receivers.
The wireless channel changes dynamically over time. This change is slow enough to be considered constant over a sufficiently short duration of time conventionally known as the coherence time. This coherence time is a function of the channel parameters and the speed of the mobile terminal relative to the base station. Over a coherence time the receiver should be able to estimate the channel characteristics and coherently sum up all of the different multipath contributions from the rake fingers. Each rake finger should then be able to track the variations that occur over time for its assigned multipath component. For example, each rake finger usually includes the ability to track the timing of a received multipath signal and to adjust the rake finger's timing for data recovery as the delay of the assigned multipath varies. The rake finger may also track other characteristics of the multipath signal that vary with time.
FIG. 1 provides an overview of a conventional implementation of a rake receiver 10 for a CDMA communication system that includes three rake fingers 12, 14, 16 for demodulation and one rake finger used as a searcher 24. Each finger 12, 14, 16 consists of two despreaders, one for pilot processing and one for data demodulation. Once assigned to a multipath, the finger continues to receive and process the pilot signal as required. The rake receiver 10 coherently combines the three multipaths using estimates of the amplitude and phase of the three strongest paths. This is accomplished in the signal combiner 26 within the demodulator 22. Each multipath component of the signal is weighted, phase adjusted and delay-adjusted using channel estimates. The total signal is a coherent sum of the three strongest multipaths.
The FIG. 1 rake receiver includes an analog front end section 18 that receives RF signals from an antenna. The analog section 18 down-converts the received RF signal to IF (intermediate frequency) or baseband, where it is oversampled by the sampling clock 20. Usually this oversampling is relatively high, such as eight times the chip rate, to allow timing recovery techniques to synchronize the system. The digitized I (in phase) and Q (quadrature) signals are then presented to the demodulating block 22 where the searcher 24 starts to test different delays of the locally generated PN code (not shown) against the received pilot I and Q signals. The searcher 24 tests for energy at different delays for the target PN code. Once the searcher detects a sufficient level of energy for a given delay, the searcher declares a lock on the signal and establishes the delay for recovering that signal. The searcher 24 informs the controller 26 of the lock and that a candidate offset is available. The controller 26 then transfers the state information to one of the available fingers 12, 14, 16 to initiate a fine tracking algorithm and signal demodulation.
The analog front end 18 is operated under closed loop control. Gain control information is fed back from a gain control section 28 to provide automatic gain control feedback to the analog front end 18. Frequency control information is derived by a frequency control section 30 from the signals output by the rake fingers 12, 14, 16. Frequency control section 30 provides frequency information to the analog front end 18 as a feedback signal to maintain a coarse lock for frequency recovery.
Each rake finger 12, 14, 16, operating in conjunction with the analog front end, has the capability of tracking a specific assigned multipath and correcting for the effects of propagation, including phase rotation and frequency and timing drifts. Demodulation is accomplished using correlators within each of the fingers to provide a multipath component of the signal. After correction, the multipath components from the rake fingers are combined together to give a soft estimate of the received symbol. The signals and the soft estimate are passed on to a slicer or channel decoder that generates a final, hard symbol decision.
Fine tracking is performed within the fingers 12, 14, 16 and involves two processes. The first is timing tracking, where the timing tracking loop measures energy on two sides (early and late) of the sample that is assumed to be the correct sampling instant. The second process determines the difference in energy between these two side samples. The difference in energy is then filtered and processed to control a decimator that selects which samples are to be chosen from the incoming oversampled data stream. Thus the ideal sampling instant is fine-tuned in steps of chip period divided by the oversampling ratio. The decimated sample stream is then despread by the I and Q PN codes to generate the pilot samples (PI, PQ). Furthermore the orthogonal modulation is uncovered to generate the data samples (DI, DQ). As discussed above, I and Q are the inphase and quadrature components of the pilot and data sequences, respectively.
The pilot signal is used to estimate the rotation of the associated data vector caused by propagation and attenuation of the I and Q components of the signal. Prior to combining the outputs of the rake fingers, the outputs are de-rotated and weighted by their relative strength. Thus the combination performed by the section 26 is a coherent maximum ratio combining process. Finally, the symbols are presented to a de-interleaver/decoder circuit that deinterleaves the received data stream and further uses a decoder such as a Viterbi decoder to remove coding. The decoded data are then made available to higher layer communication protocols.

Sasken Communication Technologies Limited


A method and logic encoded in tangible media and apparatus for securing links between a mesh point and one or more identities of one or more parent mesh points of a wireless mesh network in order to secure the links. A first association is carried out to one of the identities of one of the parent mesh points. The first mesh point undergoes a mutual authentication with an authenticator and announces the possibility of multiple links and/or multiple paths. The authentication generates a first master key from which the root master key of the key hierarchy is derived so that other master keys for different identities are derivable using a hierarchy. The mesh point undergoes a 4-way handshake to derive a first transient key. Other transient keys are obtained by a fast roaming method without having to re-undergo a backend authentication, the other transient keys being for other links and/or paths and derived using the hierarchy.

Wireless mesh networks are becoming common, e.g., in an outdoor environment for providing so-called hot spots for wireless local area networks (WLANs) conforming to the IEEE 802.11 standard. In a wireless mesh network, a set of mesh points are coupled by a backhaul network that typically forms a tree topology, at least one mesh point being the root of the tree topology, and coupled to a wired network that, for example, is coupled to the Internet. Some mesh points may also act as an access point (AP) so that one or more client stations may associate with them, and such a mesh point is called a mesh AP (MAP). Without loss of generality, each mesh point can be called a mesh AP. A non-AP mesh point, e.g., one that acts as a relay in the backhaul network, can simply be thought of as a mesh AP with the mesh AP functionality turned off, or without having the AP capability. In each tree structure of the backhaul network, one mesh AP is the root mesh point, and such a mesh point is called the root AP (RAP) herein.
Suppose a mesh AP wishes to join a mesh network as the child mesh AP of some parent mesh AP. Securing such a child mesh AP includes discovery wherein the child mesh AP receives advertisements from potential parent mesh APs and selects a parent mesh AP to join, association wherein the child mesh AP associates with the parent mesh AP, authentication wherein the child mesh AP undergoes an authentication, e.g., a shared-key authentication, or a certificate-based backend mutual authentication such as an IEEE 802.11x Extensible Authentication Protocol (EAP) authentication with an authentication server to obtain pairwise master keys (PMKs), followed by an 802.11i 4-way handshake using the PMK to obtain a pairwise transient key (PTK) for the child mesh AP to use to communicate with the parent mesh AP at L2. In the case that the AP functionalities of the mesh points is controlled by a controller using a protocol, securing the link includes the new child mesh AP joining the controller by forming a secure link, e.g., a secure tunnel to the controller so that the child mesh AP can function as an AP. It is desirable to provide for rapid roaming, so that when a connected mesh AP wishes to change its parent mesh AP, it need not undergo a complete authentication phase, e.g., a full IEEE 802.1x EAP authentication with an authenticator.
Multiple links (or "multilinks") and multiple paths (or "multipaths") are used for redundancy and load balancing purposes in a mesh network. Using Multilinks and multipaths are methods aimed at increasing mesh backhaul capacity. As one example of multilink, suppose a mesh AP includes two radios, and suppose one of the radios is used to connect to a parent mesh AP in the backhaul. Suppose the radio that forms such a primary link to the parent mesh AP in the backhaul cannot operate or there is a need to move to a different channel. One mechanism that provides a backup is to allow the second radio to form a secondary link to the parent mesh AP as an alternate link to the primary link. The backhaul is formed on one or the other link. While the secondary link can be secured in exactly the same way as the primary link using full authentication, e.g., mutual certificate-based authentication using an 802.1x EAP authentication followed by an 802.11i 4-way handshake to provide the pairwise transient key, it would be advantageous to have a mechanism that allows both the primary and secondary link to be secured at the same time, and that allows a change from primary to secondary link without having to undergo a full authentication.
As an example of multipath, suppose as another situation a mesh AP has more than one parent so that on the upstream there are two alternate paths to the root AP. Such a mechanism may be used for load balancing or to provide alternate paths to cover the case when a primary link on the path to the root AP may be down or unavailable. Having a secondary parent link and associate path to the root allows minimal downtime; no rediscovery of a new parent needs to occur. When such a second path is used, it is desirable to secure the secondary path to a second parent without having to carry out a complete authentication with an authenticator.
It also is possible to have multiple links and multiple paths simultaneously. That is, for example, a child mesh AP with two radios may have a primary and secondary link with a first parent, and as an alternate path, a primary and secondary link with a second parent.
Securing multiple links and paths in a mesh network is therefore important.

Securing multiple links and paths in a wireless mesh network including rapid roaming


To avoid blocking node AC queues in the degraded MU EDCA mode due to regular OFDMA transmission of data from another AC queue in resource units provided by an AP, the present invention proposes to use a dedicated HEMUEDCATimer for each AC queue, in order for them to be able to exit the degraded MU EDCA mode independently of the other AC queues. In this respect, upon successfully transmitting data stored in two or more traffic queues, in each of one or more accessed resource units provided by the AP within one or more transmission opportunities, the node sets each traffic queue transmitting in the accessed resource unit in the degraded MU EDCA mode for a predetermined degrading duration counted down by a respective timer associated with the transmitting traffic queue. Next, upon expiry of any timer, the node switches back the associated traffic queue to the conventional EDCA mode.

The IEEE 802.11 MAC standard defines the way Wireless local area networks (WLANs) must work at the physical and medium access control (MAC) level. Typically, the 802.11 MAC (Medium Access Control) operating mode implements the well-known Distributed Coordination Function (DCF) which relies on a contention-based mechanism based on the so-called "Carrier Sense Multiple Access with Collision Avoidance" (CSMA/CA) technique.
The 802.11 medium access protocol standard or operating mode is mainly directed to the management of communication nodes waiting for the wireless medium to become idle so as to try to access to the wireless medium.
The network operating mode defined by the IEEE 802.11ac standard provides very high throughput (VHT) by, among other means, moving from the 2.4 GHz band which is deemed to be highly susceptible to interference to the 5 GHz band, thereby allowing for wider frequency contiguous channels of 80 MHz to be used, two of which may optionally be combined to get a 160 MHz channel as operating band of the wireless network.
The 802.11ac standard also tweaks control frames such as the Request-To-Send (RTS) and Clear-To-Send (CTS) frames to allow for composite channels of varying and predefined bandwidths of 20, 40 or 80 MHz, the composite channels being made of one or more communication channels that are contiguous within the operating band. The 160 MHz composite channel is possible by the combination of two 80 MHz composite channels within the 160 MHz operating band. The control frames specify the channel width (bandwidth) for the targeted composite channel.
A composite channel therefore consists of a primary channel on which a given node performs EDCA backoff procedure to access the medium, and of at least one secondary channel, of for example 20 MHz each.
EDCA (Enhanced Distributed Channel Access) defines traffic categories and four corresponding access categories that make it possible to handle differently high-priority traffic compared to low-priority traffic.
Implementation of EDCA in the nodes can be made using a plurality of traffic queues (known as "Access Categories") for serving data traffic at different priorities, each traffic queue being associated with a respective queue backoff value. The queue backoff value is computed from respective queue contention parameters, e.g. EDCA parameters, and is used to contend for access to a communication channel in order to transmit data stored in the traffic queue.
Conventional EDCA parameters include CWmin, CWmax and AIFSN for each traffic queue, wherein CWmin and CWmax are the lower and higher boundaries of a selection range from which an EDCA contention window CW is selected for a given traffic queue. AIFSN stands for Arbitration Inter-Frame Space Number, and defines the number of time slots (usually 9 μs), additional to a DIFS interval (the total defining the AIFS period) the node must sense the medium as idle before decrementing the queue backoff value associated with the traffic queue considered.
The EDCA parameters may be defined in a beacon frame sent by a specific node in the network to broadcast network information.
The contention windows CW and the queue backoff values are EDCA variables.
Conventional EDCA backoff procedure consists for the node to select a queue backoff value for a traffic queue from the respective contention window CW, and then to decrement it upon sensing the medium as idle after the AIFS period. Once the backoff value reaches zero, the node is allowed to access the medium.
The EDCA queue backoff values or counters thus play two roles. First, they drive the nodes in efficiently accessing the medium, by reducing risks of collisions; second, they offer management of quality of service, QoS, by mirroring the aging of the data contained in the traffic queue (the more aged the data, the lower the backoff value) and thus providing different priorities to the traffic queues through different values of the EDCA parameters (especially the AIFSN parameter that delays the start of the decrementing of the EDCA queue backoff values).
Thanks to the EDCA backoff procedure, the node can thus access the communication network using contention type access mechanism based on the queue contention parameters, typically based on the computed queue backoff counter or value.
The primary channel is used by the communication nodes to sense whether or not the channel is idle, and the primary channel can be extended using the secondary channel or channels to form a composite channel. The primary channel can also be used alone.
Given a tree breakdown of the operating band into elementary 20 MHz channels, some secondary channels are named tertiary or quaternary channels.
In 802.11ac, all the transmissions, and thus the possible composite channels, include the primary channel. This is because the nodes perform full Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) and Network Allocation Vector (NAV) tracking on the primary channel only. The other channels are assigned as secondary channels, on which the nodes have only capability of CCA (clear channel assessment), i.e. detection of an idle or busy state/status of said secondary channel.
An issue with the use of composite channels as defined in the 802.11n or 802.11ac (or 802.11ax) is that the nodes compliant with a use of composite channels (i.e. 802.11n and 802.11ac-compliant nodes or "HT nodes" standing for High Throughput nodes) have to co-exist with legacy nodes not able to use composite channels but relying only on conventional 20 MHz channels (i.e. non-HT nodes compliant only with for instance 802.11a/b/g) exist within the same wireless network, and thus have to share the same 20 MHz channels.
To cope with this issue, the 802.11n and 802.11ac and 802.11ax standards provide the possibility to duplicate control frames (e.g. RTS/CTS or CTS-to-Self or ACK frames to acknowledge correct or erroneous reception of the sent data) over each 20 MHz channel in an 802.11a legacy format (called as "non-HT") to establish a protection of the requested TXOP over the whole composite channel.
This is for any legacy 802.11a node that uses any of the 20 MHz channel involved in the composite channel to be aware of on-going communications on the 20 MHz channel. As a result, the legacy node is prevented from initiating a new transmission until the end of the current composite channel TXOP granted to an 802.11n/ac/ax node.
As originally proposed by 802.11n, a duplication of conventional 802.11a or "non-HT" transmission is provided to allow the two identical 20 MHz non-HT control frames to be sent simultaneously on both the primary and secondary channels forming the used composite channel.
This approach has been widened for 802.11ac to allow duplication over the channels forming an 80 MHz or 160 MHz composite channel. In the remainder of the present document, the "duplicated non-HT frame" or "duplicated non-HT control frame" or "duplicated control frame" means that the node device duplicates the conventional or "non-HT" transmission of a given control frame over secondary 20 MHz channel(s) of the (40 MHz, 80 MHz or 160 MHz) operating band.
In practice, to request a composite channel (equal to or greater than 40 MHz) for a new TXOP, an 802.11n/ac node performs an EDCA backoff procedure in the primary 20 MHz channel as mentioned above. In parallel, it performs a channel sensing mechanism, such as a Clear-Channel-Assessment (CCA) signal detection, on the secondary channels to detect the secondary channel or channels that are idle (channel state/status is "idle") during a PIFS interval before the start of the new TXOP (i.e. before any queue backoff counter expires).
More recently, Institute of Electrical and Electronics Engineers (IEEE) officially approved the 802.11ax task group, as the successor of 802.11ac. The primary goal of the 802.11ax task group consists in seeking for an improvement in data speed to wireless communicating devices used in dense deployment scenarios.
Recent developments in the 802.11ax standard sought to optimize usage of the composite channel by multiple nodes in a wireless network having an access point (AP). Indeed, typical contents have important amount of data, for instance related to high-definition audio-visual real-time and interactive content. Furthermore, it is well-known that the performance of the CSMA/CA protocol used in the IEEE 802.11 standard deteriorates rapidly as the number of nodes and the amount of traffic increase, i.e. in dense WLAN scenarios.
In this context, multi-user (MU) transmission has been considered to allow multiple simultaneous transmissions to/from different users in both downlink (DL) and uplink (UL) directions from/to the AP and during a transmission opportunity granted to the AP. In the uplink, multi-user transmissions can be used to mitigate the collision probability by allowing multiple non-AP stations or nodes to simultaneously transmit.
To actually perform such multi-user transmission, it has been proposed to split a granted communication channel into sub-channels, also referred to as resource units (RUs), that are shared in the frequency domain by multiple users (non-AP stations/nodes), based for instance on Orthogonal Frequency Division Multiple Access (OFDMA) technique. Each RU may be defined by a number of tones, the 80 MHz channel containing up to 996 usable tones.
OFDMA is a multi-user variation of OFDM which has emerged as a new key technology to improve efficiency in advanced infrastructure-based wireless networks. It combines OFDM on the physical layer with Frequency Division Multiple Access (FDMA) on the MAC layer, allowing different subcarriers to be assigned to different stations/nodes in order to increase concurrency. Adjacent sub-carriers often experience similar channel conditions and are thus grouped to sub-channels: an OFDMA sub-channel or RU is thus a set of sub-carriers.
As currently envisaged, the granularity of such OFDMA sub-channels is finer than the original 20 MHz channel band. Typically, a 2 MHz or 5 MHz sub-channel may be contemplated as a minimal width, therefore defining for instance 9 sub-channels or resource units within a single 20 MHz channel.
The multi-user feature of OFDMA allows the AP to assign or offer different RUs to different non-AP stations/nodes in order to increase competition. This may help to reduce contention and collisions inside 802.11 networks.
Contrary to downlink OFDMA wherein the AP can directly send multiple data to multiple stations (supported by specific indications inside the PLCP header), a trigger mechanism has been adopted for the AP to trigger multi-user uplink (MU UL) OFDMA communications from various nodes.
To support multi-user uplink, i.e. uplink transmission to the 802.11ax access point (AP) during a pre-empted TXOP, the 802.11ax AP has to provide signalling information for the legacy nodes (non-802.11ax nodes) to set their NAV and for the 802.11ax nodes to determine the allocation of the resource units RUs provided by the AP.
The 802.11ax standard defines a trigger frame (TF) that is sent by the AP to the 802.11ax nodes to trigger Multi-User uplink communications.
The document IEEE 802.11-15/0365 proposes that a 'Trigger' frame (TF) is sent by the AP to solicit the transmission of uplink (UL) Multi-User (OFDMA) PPDU from multiple nodes. The TF defines the resource units as provided by the AP to the nodes. In response, the nodes transmit UL MU (OFDMA) PPDU as immediate responses to the Trigger frame. All transmitters can send data at the same time, but using disjoint sets of RUs (i.e. of frequencies in the OFDMA scheme), resulting in transmissions with less interference.
The bandwidth or width of the targeted composite channel is signalled in the TF frame, meaning that the 20, 40, 80 or 160 MHz value is added. The TF frame is sent over the primary 20 MHz channel and duplicated (replicated) on each other 20 MHz channels forming the targeted composite channel, if appropriate. As described above for the duplication of control frames, it is expected that every nearby legacy node (non-HT or 802.11ac nodes) receiving the TF on its primary channel, then sets its NAV to the value specified in the TF. This prevents these legacy nodes from accessing the channels of the targeted composite channel during the TXOP.
A resource unit RU can be reserved for a specific node, in which case the AP indicates, in the TF, the node to which the RU is reserved. Such RU is called Scheduled RU. The indicated node does not need to perform contention on accessing a scheduled RU reserved to it.
The type of data the node is allowed to transmit in the Scheduled RU may be specified by the AP in the TF. For instance, the TF includes a 2-bit "Preferred AC" field in which the AP indicates one of the four EDCA traffic queues. On the other hand, the AP may let the Scheduled RU be opened to any type of data. To activate or not the "Preferred AC", the TF includes another 1-bit field, namely "AC Preference Level".
In order to better improve the efficiency of the system with regards to un-managed traffic to the AP (for example, uplink management frames from associated nodes, unassociated nodes intending to reach an AP, or simply unmanaged data traffic), resource units may be proposed by the AP to the 802.11ax nodes through contention-based access. In other words, the resource unit RU can be randomly accessed by more than one node (of the group of nodes registered with the AP). Such RU is called Random RU and is indicated as such in the TF. Random RUs may serve as a basis for contention between nodes willing to access the communication medium for sending data.
An exemplary random resource selection procedure is defined in document IEEE 802.11-15/1105. According to this procedure, each 802.11ax node maintains a dedicated backoff engine, referred below to as OFDMA or RU (for resource unit) backoff engine, using RU contention parameters, including an RU backoff value, to contend for access to one of the random RUs. Once its OFDMA or RU backoff value reaches zero (it is for instance decremented at each new TF-R frame by the number of random RUs defined therein), a node becomes eligible for RU access and thus randomly selects one RU from among all the random RUs defined in the received trigger frame. It then uses the selected RU to transmit data of at least one of the traffic queues.
As readily apparent from the above, the Multi User Uplink medium access scheme (or OFDMA or RU access scheme) allows the number of collisions generated by simultaneous medium access attempts to be reduced, while also reducing the overhead due to the medium access since the medium access cost is shared between several nodes. The OFDMA or RU access scheme thus appears to be quite more efficient (with regards of the medium usage) than the conventional EDCA contention-based medium access scheme (in the context of a high density 802.11 cell).
Although the OFDMA or RU access scheme seems more efficient, the EDCA access scheme must also survive and thus coexist with the OFDMA or RU access scheme.
This is mainly due to the existence of legacy 802.11 nodes which must still have the opportunity to access the medium, while they are not aware of the OFDMA or RU access scheme. And the global fairness about the medium access must be ensured.
This is also all the more necessary that the 802.11ax nodes should also have the opportunity to gain access to the medium through conventional EDCA contention-based medium access, for instance to send data to another node (i.e. for traffic different from uplink traffic to the AP).
So the two medium access schemes, EDCA and OFDMA/RU access schemes, have to coexist.
This coexistence has downsides.
For instance, 802.11ax nodes and legacy nodes have the same medium access probability using the EDCA access scheme. However, the 802.11ax nodes have additional medium access opportunities using the MU Uplink or OFDMA or RU access scheme.
It results that access to the medium is not fully fair between the 802.11ax nodes and the legacy nodes.
To restore some fairness between the nodes, solutions have been proposed to modify, upon successfully transmitting data over an accessed resource unit (i.e. through UL OFDMA transmission), a current value of at least one queue contention parameter into a penalized or degraded value, to reduce a probability for the node to access a communication channel through (EDCA) contention. For instance, the penalized or degraded value is more restrictive than the original (or legacy) value.
For instance, document IEEE 802.11-16/1180 entitled "Proposed text changes for MU EDCA parameters" proposes that, upon successfully (MU UL OFDMA) transmitting data in a resource unit, RU, reserved by the AP, a node is set in a MU EDCA mode, for a predetermined duration counted down by a timer (noted HEMUEDCATimer below, standing for High Efficiency Multi-User EDCA Timer), in which the EDCA parameters are set to values, referred to as MU EDCA parameters values or MU values, different from legacy values used in a legacy EDCA mode. The MU parameter values are set to more restrictive values than the legacy values: more restrictive values for EDCA parameters means that a probability for a node to access the communication channel through EDCA access scheme using the MU values is reduced relatively to an access using the legacy values.
In other words, as soon as the node transmits some data from one or more traffic queues using a scheduled RU assigned to the node by the AP, the node shall modify the EDCA parameters associated with the transmitting traffic queue(s) (here below "degraded", "penalized" or "blocked" traffic queue(s)), with some special more restrictive ("MU" or "degraded") values that may be provided by the AP in a dedicated Information Element of a beacon frame, which also includes the value to be used by the nodes for their HEMUEDCATimer.
One may thus note that the AP sends, to the nodes, the more restrictive values to drive the node in modifying current values of their EDCA parameters into the MU values upon the node successfully transmitting data over the accessed resource unit. This is also to reduce a probability for the node to access the communication channel through EDCA access scheme.
In addition, the AP may determine the more restrictive values based on a history of data received from the nodes (e.g. through RUs).
The disclosed approach suggests increasing only the value of AIFSN for each transmitting traffic queue, while keeping CWmin and CWmax unchanged. As the corresponding AIFS period increases, the traffic queue in the MU EDCA mode is prevented (or at least substantially delayed) from having its queue backoff value or counter been decremented upon sensing the medium free, in particular in high density environment in which the medium does not remain free for a long time. New accesses to the medium using EDCA access scheme are statistically substantially reduced, or even no longer possible.
Upon switching into the MU EDCA mode, the node starts its HEMUEDCATimer countdown. The HEMUEDCATimer is reinitialized each time the node successfully (MU UL OFDMA) transmits data in a new reserved RU. The initializing value of HEMUEDCATimer is suggested to be high (e.g. tens of milliseconds) in order to encompass several new opportunities for MU UL transmissions.
When the HEMUEDCATimer lapses, the traffic queues in MU EDCA mode are switched back to the legacy EDCA mode with legacy EDCA parameters, thereby exiting the queues from the MU EDCA mode.
Thus, this mechanism of double operating modes, conventional EDCA mode and MU EDCA mode, promotes the usage of the MU UL mechanism by reducing the probability of a MU UL transmitting node to gain access to the medium using the EDCA mechanism.
The HEMUEDCATimer mechanism of reinitializing the HEMUEDCATimer each time the node successfully transmits new data in accessed reserved RU means the node remains in the MU EDCA state as long as the AP provides (scheduled or random) RUs to the node.
This approach has a main drawback as explained now.
If the node transmits data from two or more traffic queues in one or more resource units provided by the AP (for instance if a dedicated traffic queue becomes empty, the node selects other data to be sent from a traffic queue with higher priority), the two or more traffic queues are turned into the MU and more restrictive EDCA mode. They are mainly prevented from accessing the medium through EDCA access scheme, as for instance their respective AIFSN are very restrictive.
It may happen that the AP regularly provides resource units to that node (being in such situation) with an indication of a preferred traffic queue from which data are to be selected.
As long as this polling with preferred traffic queue continues, the node empties the corresponding traffic queue upon accessing the provided resource units, while keeping all the two or more traffic queues in the MU EDCA mode. It means the other traffic queue or queues remain locked in the MU and more restrictive EDCA mode, and cannot be purged by accessing the medium.
The QoS in the network is thus severely deteriorated.

Enhanced management of ACs in multi-user EDCA transmission mode in wireless networks


A GPS system comprising a GPS receiver for receiving and processing a GPS signal is provided. The traffic information receiver is adapted for receiving traffic information signal and a storage device for storing the GPS signal and the traffic information signal. The GPS receiver comprises a wireless receiver and a processor. The wireless receiver is adapted for receiving the GPS signal. The processor is adapted for controlling the wireless receiver and rotationally storing the GPS signal and the traffic information signal at a predetermined time period, and then transmitting the stored GPS signal and traffic information signal, in order, to the storage device, wherein the information corresponding to the GPS signal and the traffic information signal are transmitted according to a specific time or frequency setup by the processor.

1. Field of the Invention
The present invention generally relates to a system for receiving and processing a GPS signal and a traffic information signal, and more particularly to a GPS system for receiving and processing a GPS signal and a traffic information signal, wherein a processor of a GPS receiver rotationally stores the GPS signal and the traffic information signal into a buffer and then transmits the stored signals to a storage device, in order, for displaying the information.
2. Description of the Related Art
Presently, a traffic condition has improved significantly to provide more convenience and quality to our every day activities. Accordingly, a concept of global village is created. For saving energy, precious time and increasing efficiency, a system to accurately locate a person or object in a large range and to communicate thereto without any limit of time and location is very essential. Accordingly, a global positioning system (GPS) has been developed to accurately provide the information of the latitude and the longitude to enable the users all around the world know their exact location.
Furthermore, there are two major purposes of the GPS system. The first purpose is to locate, retrieve exact location information by referring to the location information transmitted by the satellite, and the second purpose is to synchronize signal in the internet. Because the satellite provides a time signal, and if the world wide internet system can receive this time signal, the internet system will have a stable resource for the synchronized signal, and most of the devices may be gradually designed to rely on this simple and stable method for receiving the synchronized signal.
Generally, a GPS receiver receives signals from a plurality of satellites corresponding to the positions of objects or persons, and the time signal can be chosen from a signal with the best quality. The GPS system is mostely used in the transportation industry. GPS receiver is installed in a car, airplane or a ship to receive the satellite signal to enable the user to learn the exact location for various services, for example, navigation, SOS, road rescue, security and so on.
As the semiconductor technology is well developed, the overall cost may be reduced. Thus, the car GPS is widely used, and the use of GPS system in the car has become the major purpose of the GPS system. Commonly, the user uses the GPS system with the car LCD display or the PDA for retrieving map signal and navigation status information.
Furthermore, the FM radio message system is another appliance of the traffic message channel (TMC), which broadcast the traffic and weather information to guide the user to take a proper route to arrive at the destination. The traffic information is being updated on real time basis, for example accident, traffic and other information, so that the user may choose the best route to arrive at the destination. Therefore, the TMC provides the traffic information on real time basis to the users on the road and the TMC is different from the roadside traffic news bulletin board.
When using the TMC and the GPS receiver in the car navigation, the TMC receives the real time traffic information and transmits the GPS signal and traffic signals to LCD display, PDA or car navigator where it is displayed. Referring to FIG. 4, the conventional terminal device A comprises a receiving interface A1 to receive signals from a GPS receiver C1 and a traffic information receiver C2. When the receiving interface A1 simultaneously receives GPS and traffic signals, a processor A2 in the terminal device A encodes the GPS and traffic signals and then wraps it into a packet as a signal set which is then transmitted to a receiving interface B1 of a portable host B through a transmission interface A3 of the terminal device A. Next, a memory program B2 in the portable host B decodes and restores the signal set into the GPS signal and traffic information so that the portable host B displays the map represented by the GPS signal and traffic information. Even though the conventional art provides the GPS signal and the traffic information signal to the portable host B, but there are still more defects, which are described as follows.                1. The conventional terminal device A simultaneously receives the signals transmitted by the GPS receiver C1 and the traffic information receiver C2, which is then encoded into a packet for converting signals into a signal set and then transmitted to the portable host B where it is decoded. Because, the GPS signal and traffic information signal are both continuously simultaneously transmitted, thus often packaging and decoding processes occupies the memory capacity and the system resource of the terminal device A and the portable device B, and therefore the overall transmission quality is adversely affected.        2. When the terminal device A simultaneously receives the GPS signal and traffic information signal, interference between the GPS signal and the traffic signal may easily occur and cause instability in signal transmission, or the information may be overwritten and become invalid.
Therefore, how to overcome the above defects is an important issue for the manufacturers in the field.

GPS system for receiving and processing GPS signal and traffic information signal


An electronic component includes a frame-shaped supporting body including a heat-curable resin and surrounding a functional unit on one main surface of a substrate and so as to be separated from a periphery of the substrate on an inner side and in which a lid member is fixed to the supporting body such that an opening of the frame-shaped supporting body is sealed. The frame-shaped supporting body includes a frame-shaped supporting body main body, a first protrusion that protrudes toward an inside from the supporting body main body and a second protrusion that protrudes toward an outside from the supporting body main body at a portion where the supporting body main body and the first protrusion are continuous with each other.

1. Field of the Invention
The present invention relates to an electronic component in which a substrate and a lid member are joined to each other via a frame-shaped supporting body including a heat-curable resin, and relates to a manufacturing method therefor.
2. Description of the Related Art
In a surface acoustic wave filter device, for example, a package structure having a cavity is adopted, in which a surface acoustic wave filter element faces the cavity. Consequently, in order to make progress in size reduction of such a device, development of wafer level chip size packaging (WLCSP) has been progressing. In WLCSP, the size of the planar shape of a package is the same as that of a surface acoustic wave element chip.
For example, in Japanese Unexamined Patent Application Publication No. 2002-532934, an example of this kind of surface acoustic wave device is disclosed. As illustrated in FIG. 9, a surface acoustic wave device 1001 described in Japanese Unexamined Patent Application Publication No. 2002-532934 includes a plate-shaped surface acoustic wave element 1002. The surface acoustic wave element 1002 includes a piezoelectric substrate 1003. Functional units 1004 including interdigital transducer (IDT), electrodes are formed on the upper surface of the piezoelectric substrate 1003. A rectangular frame-shaped supporting body 1005 is formed on the upper surface of the surface acoustic wave element 1002. The supporting body 1005 is arranged so as to surround the functional units 1004. A lid member 1006 is fixed to the top of the supporting body 1005 such that a cavity that the functional units 1004 face is sealed.
Penetrating electrodes 1007 are formed so as to penetrate through the frame-shaped supporting body 1005 and the lid member 1006. Outer terminals 1008 are formed on the upper ends of the penetrating electrodes 1007.
In the surface acoustic wave device 1001, the outer peripheries of the supporting body 1005 and the lid member 1006 have the same dimensions as the outer periphery of the surface acoustic wave element 1002. Therefore, a reduction in size can be achieved.
On the other hand, in the surface acoustic wave device 1001, the wider the cavity which the functional units 1004 face becomes, the greater the number of functional units that can be arranged in the cavity. If the size of the cavity can be increased, size reduction of the surface acoustic wave device 1001 can also progress. In order to increase the area of the planar shape of the cavity, the width of the frame-shaped supporting body 1005 may be decreased. However, the frame-shaped supporting body 1005 needs to have a certain width in order to allow the penetrating electrodes 1007 to be formed. In this case, the area of the cavity is decreased. In addition, if the width of the supporting body 1005 is decreased, the cavity cannot be sufficiently tightly sealed. Accordingly, in cases such as where there is a change in temperature, there is a risk of leak defects occurring. Consequently, there has been a problem in that the environmental resistance has been degraded.

Electronic component and manufacturing method therefor


A lacrosse stick includes a flared (e.g., forked) end and a flexible head frame adapted to receive a mesh thereon.

In the game of lacrosse, players use sticks to receive and shoot a ball. Lacrosse sticks generally include an elongated shaft and a head frame. The player grips a handle located toward the butt end of the shaft, and utilizes the head frame, which includes mesh, to receive and shoot the ball during play.
Decades ago, some lacrosse sticks were manufactured as one-piece, integral wooden structures. Such sticks were not only difficult and costly to fabricate, but owing to their unitary mechanical properties, also limited the maneuvers that a player could execute. For example, the stiff wood, while necessary for shaft strength, was poorly suited to the head frame; the lack of flexibility would, for example, limit the player's ability to scoop up the ball from the ground or make it more difficult for a player to receive a hard pass without feeling excessive vibrations.
As a result, it has become commonplace to fabricate lacrosse sticks using a shaft element formed of straight grained wood, or wood laminate, or a tough, lightweight metallic or reinforced plastic tubular element and to affix to the forward end of the shaft a flexible head frame (composed, for example, of a tough synthetic thermoplastic material such as high impact-strength nylon). Indeed, most lacrosse sticks today are sold as separate head and shaft portions.
A typical head frame for a lacrosse stick includes a socket to receive the forward end of the shaft. The shaft is then coupled to the head frame by a fastener, such as a screw. One problem with such a construction is that the connection between the head frame and shaft may loosen during play, compromising the player's ability to effectively control his stick. Worse, in some instances the head frame may detach entirely from the shaft.
Some lacrosse sticks exist that reinforce the connection between the head frame and the shaft to prevent disengagement of the head frame from the shaft. Unfortunately, regardless of reinforcement or attachment techniques, the head frame may still loosen or become detached over time. What is needed, then, is a lacrosse stick that integrates a head frame and a shaft into a unitary construction that does not become loosened or disengaged, but still retains flexibility in the head frame and rigidity in the shaft.


A high-strength multi-layered film excellent in heat resistance, shrinkability and stretchability and usable for wrapping of various articles which comprises at least five layers comprising a surface layer (S layer) mainly composed of at least one polymer selected from (A), (B), etc. and as inner layers at least one base layer (SBC layer) containing mainly a mixed composition comprising a combination such as (A)+(B)+(C) or the like, at least one core layer (H layer) containing mainly a polymer selected from (C), and at least one auxiliary layer (R layer) containing mainly at least one polymer selected from (A) and (B), with a proviso that when the R layer is placed adjacent to the S layer, the R layer comprises the resin different from that of the S layer, said (A) being a low-density polyethylene or a copolymer of ethylene with a specific monomer, said (B) being a soft thermoplastic elastomer having a Vicat softening point of 80.degree. C. or lower, and said (C) being a specific polymer such as a crystalline polypropylene or the like or a mixed polymer thereof; and a process for producing the same.

In film wrapping, a variety of wrapping methods taking advantage of the film properties are used. For example, many methods are used such as a method of sealing in a bag form, a method of wrapping by twisting a film, a method of wrapping by heat shrinking (to be referred to as a "shrink method" hereinafter), a tight-contact wrap method typified by Saran Wrap.RTM. (made by Asahi Chemical Industry Co., Ltd.), a stretch wrap method and a skin pack method. Each wrapping method is required to have its own wrapping properties, and in a practical sense, film materials, composition, form and properties are selected suitably for each wrapping method.
Of the above methods, the shrink method uses the heat shrinkability of a preliminarily stretched and oriented film. In this method, an article to be wrapped is preliminarily loosely wrapped by a film, for example, an article is wrapped by sealing, and then the film is allowed to shrink by heating it with hot air, infrared rays, hot water or other heating medium to bring the film into tight contact with the content contained therein. The characteristics of this wrapping are that the appearance of the wrapped article is esthetically good, that the commercial value is improved, that the content quality can be visually and tangibly recognized while the article is kept in a hygienic wrapping, that even an irregularly-formed article and even a plurality of articles can be tightly fixed or wrapped in one wrapping, and that the protection performance for the content against vibration and impact is excellent. Further, as compared with a stretch wrapping method which is popular nowadays in supermarkets and will be described later, the above shrink method characteristically permits an increase in wrapping speed. The shrink method also permits the wrapping of an irregularly formed article which cannot be wrapped esthetically by a stretch wrapping and of an article without any container such as a tray. Moreover, the shrink method characteristically permits the wrapping of various articles more tightly. However, on the other hand, the shrink method has defects in that the film is required to be sufficiently heated until the film becomes shrunken. This would result in the likelihood that the sealing portion would break and that the film would deteriorate after being shrunk (strength and optical properties). On the other hand, conventional shrink films have low stretchability, and would break if stretched, to any large extent. Some conventional shrink films cannot simply be stretched due to too strong of a stress caused by the stretching. Further, these films have almost no self-adhesion properties. For these reasons, these shrink films are not at all suitable for stretch wrapping. Conventional shrink films have the above-described defects and problems.
As long as the above defects can be overcome, shrink wrapping is more advantageous than stretch wrapping in use of film area a film, in lesser film thickness and in wrapping speed.
Meanwhile, stretch wrappings have the following excellent characteristics. An easily stretchable film is rich in fitness in which it is free from permanent deformation and the tendency to form a crease when stretched and it can cope with the concavo-convex form and size of an article to be wrapped. A film can be simply fixed by a wrapping tension without loosening by lightly attaching it under pressure or heat-sealing it. A film for fresh foods has proper permeability to gas to prevent the decrease in freshness and weight. The quality of an article can be visually and tangibly known while the article is kept in a hygienic wrapping. The appearance of a package is esthetically good and the commercial value of a wrapped article can be remarkably improved. A wrapping machine can be selected from less expensive manual wrapping machines and high speed automatic wrapping machines a required. Further, an article to be wrapped is not at all heated. As a wrapping method having the above excellent characteristics, the stretch wrapping method is widely used in supermarkets, etc., for wrapping fruits and vegetables, fresh foods, meat and cooked dishes. However, films for the stretch wrapping have the following defects and problems. Due to having low strength, the film is likely to break mechanically during wrapping or in distribution. The film is likely to form holes when sealed. Since the film is imparted with stretchability by taking care not to give too stretch and orientation when produced, the film is characterized with a low modulus of elasticity. The film thickness cannot be extremely decreased as a result of the importance placed on its operational capabilities (e.g. mechanical suitability and manual workability) (in order to avoid deteriorating these capabilities), and accordingly, a film having a large thickness is inevitably used. Many manufacturers have attempted to create films equivalent to or films which are excellent over conventionally widely used films formed of plasticized vinyl chloride (containing 30 to 33% by weight of a plasticizer), and these manufacturers have manufactured a variety of films from various resins by way of trial. However, up to the present time they have not been successful. From the viewpoint of environmental pollution and hygiene, it has been desired to develop a substitute film for the plasticized vinyl chloride film. However, the use of films having inferior qualities and being poor in handling properties is unavoidable at the present time. However, these substitute films being used at present are poor in handling and are used with reluctance in a working site due to their poor wrapping workability. These substitute films are not used in such amounts that they can replace vinyl chloride films. Presently, the amount of these films which are in use is very small.
The shrink wrapping is explained hereinafter, which, of course, does not limit the present invention.
As for shrink wrapping, a stretched film of plasticized polyvinyl chloride (to be referred to as PVC hereinafter) is used in the largest quantity as a high-class shrink wrapping film. This film has superior advantages in that it is capable of heat shrinkage at a high rate and at a relatively low temperature. It permits excellent shrink wrapping in a wide temperature range, and also has a high film elastic modulus (50 to 200 kg/mm.sup.2) and excellent suitability to mechanical wrapping. However, it is inferior in heat sealability and in moisture proof, and it has a hygienic problem due to the presence of a plasticizer and a problem of deterioration with time due to the plasticizer. There are also problems in that it generates a toxic gas such as a chlorine-containing gas when fused with a heating wire for cutting. It also generates a corrosive toxic gas when incinerated after use, and it also becomes stiff and fragile and is likely to break due to having poor resistance to cold when a wrapped article is preserved at a low temperature, handled in a cold area or frozen.
In recent years, a polypropylene-based (to be referred to as PP-based hereinafter) shrink wrap film has been attracting attention. The defect with this film is that the shrinkability is inferior to that of a PVC film. A PP-based stretched film is superior in mechanical properties, moisture resistance and fusion-sealability and excellent as a shrink wrapping film. Further, it has a lower specific gravity than PVC, and is advantageous in terms of material cost.
However, PP is a crystalline polymer having a high softening point, and likely to tear when stretched. Moreover, it has a higher heat-shrink temperature than a conventional stretched film, particularly a PVC film, and shows a small shrinkage at a lower temperature of about 100.degree. C. For this reason, PP is required to be heated to a higher temperature in a shrink wrapping step. The tolerable range of the heating temperature is narrow, and further, the dependence of the shrinkage on temperature is sharp. Therefore, due to a local uneven heating during the wrapping, it shrinks unevenly to cause undesirable defects, such as "creases" and "pockmarks", in the course of practical use. If the pp film is sufficiently heated to prevent the above defect, undesirably, an article to be wrapped would become over-heated, and the PP film would undergo devitrification, form holes by being melted, deteriorates in performance and would result in a large breaking which starts from a sealing portion or an air-discharge opening portion. These constitute serious defects. A PP film also has defects in that a wrapped article is likely to be loose since a stress is released after a certain period of time and the film after wrapping becomes hard and more fragile.
In a conventional polyethylene-based film, the molecule cannot be sufficiently stretched or oriented. Therefore, such a film has a low heat shrinkage, a low heat shrink stress in particular. Further, the film has a high shrink temperature, and it is also inferior in strength and optical properties. The strength of the film binding a wrapped article is also low. Therefore, the film having an increased thickness is used in a special field.
The polyethylene-based film, which is obtained by using high energy rays to cause a sufficient crosslinking reaction on the molecule and by stretching it at a high temperature, has a high heat shrinkage and a high heat shrink stress in a high-temperature range, and such a film is excellent before wrapping over a general polyethylene-based film in optical properties such as transparency and gloss and heat resistance such as melt resistance or resistance to formation of holes. Since, however, it is allowed to shrink in a high-temperature range, its performance greatly deteriorates as compared with a film used for shrink wrapping at a low-temperature (particularly, the optical properties greatly decrease). Furthermore, the above film has a defect in that the wrapping speed is inferior for the following reasons. It has heat shrink properties in which it rapidly shrinks under heat. It is difficult to heat-seal due to high crosslinking. It is easily broken due to inferior resistance to tearing and difficult to cut with a heating wire. As described above, to maintain the performance of a film, one of the important features required of shrink wrapping is that the wrapping can be carried out effectively at a low temperature, and this feature is also required when an article to be wrapped is brought into contact with the film (particularly when fresh foods are wrapped).
In case that a known film which has a high shrink temperature (it is practically required to allow the film to shrink at least 20% in the width and length directions), or which shrinks rapidly under heat (due to high shrink dependency upon temperature) is used wrapping is required to be conducted at a temperature greatly exceeding the melting point of the polymer and under very narrow conditions in order to particularly improve the finish of a wrapped article. This case involves a contradicting problem in that the properties of the film are greatly decreased.
On the other hand, when a stretched film is produced from PP as a material, there is employed a method in which PP is melted in an extruder, extruded through dies and rapidly cooled to obtain a film (hereinafter referred to as "raw film") in a tubular form, the tubular raw film is reheated at a high temperature of 130.degree. to 150.degree. C., and stretched by introducing air into the tube. When the material is a low-density polyethylene, it is considered that biaxial stretching for high stretching and orienting easily causes breaking at a processing time and that the stretching is technically very difficult.
For this reason, it is a general practice to employ a one-stage inflation method in which the material is extruded, e.g., at a temperature of 180.degree. to 220.degree. C. and then immediately inflated while properly cooling it with air to form a film having a predetermined size.
The above method has a characteristic feature in that the film can be produced at a very low cost with ease. However, intermolecular flow is likely to occur, and no satisfactory molecular orientation can be obtained by stretching. Further, the film shows very poor optical properties. Therefore, the heat shrinkage and heat shrink stress are small, and the heat shrink temperature region is on a high-temperature side. Only when the film has an increased thickness, can it be used in a special field. For this reason, it is conceivable to prevent he intermolecular flow and obtain a sufficient molecular orientation by employing a method which comprises forming a low-density polyethylene, irradiating the formed product with high-energy radiation under proper conditions to cause a partial crosslinking reaction, reheating the product up to a temperature beyond the melting point (e.g., 140.degree. C.) and stretching it. In this case, however, the degree of the shrinkage is low at a lower temperature, and the resultant film is likely to tear.
For other new wrapping film, a diversity of composite, multi-layered films are known.
With a technical advance in required properties, an increasing number of composite films tend to be produced. For example, there is a composite film obtained by melt-laminating other resin on a nearly unstretched film or a stretched film. Specifically, commercially available is a film having improved heat-sealability obtained by melt-laminating other resin on an unstretched polypropylene prepared by a casting method (called CPP) or an oriented polypropylene (OPP) or a film which is coated with vinylidene chloride-based latex to impart it with barrier properties (called K coat film). A variety of films or a combination of these films are selected depending upon use.
On the other hand, generally known is a co-extruded film obtained by melting a plurality of resins in separate extruders, extruding the resins through a multi-layer die while converging and fusing them inside the die and cooling the resultant product to form a film or sheet.
However, when a film having the above multi-layer structure of which at least one layer is highly stretched and oriented is obtained from a combination of resins having mutually different properties (melting point, softening point, melt index and orientation properties), the optimum extrusion conditions and stretching conditions differ depending upon the resins. Therefore, when such a film is produced by a prior art method, many problems occur including defective phenomena such as a nonuniform section, streaks including an insufficiently stretched portion, a puncture, breach, peeling of layers and whitening due to interfacial roughening. Further, there is obtained a film having different properties from those of an intended film. Thus, these defects have not yet been overcome. In order to overcome these defects, the present inventors completed composite films, which are disclosed in JP,A 55-118859 (corresponding to U.S. Pat. No. 4430378) and JP,A 58-175635. However, these films have not as yet sufficiently met the above requirement level. The present invention has achieved the creation of a film which fully satisfies the properties lacking in these composite films, which widens the use field, and which is capable of exhibiting high performances even though it has a much smaller thickness than any conventional film and is excellent in cost performance. These features will be more clear in comparison made with the Comparative Examples which will follow later.
The present status of the stretch wrapping, a second field to which the film of the present invention is directed, will be described hereinafter.
In this field, films formed from a soft PVC containing, as a material, a large amount, e.g., as much as about 30% by weight (nearly 50 vol %) of a plasticizer are mainly commercially used. If a large amount of a plasticizer is not incorporated, it would be difficult to process these films, or it would be impossible to impart the film with flexible properties, and these films could not be used in this field. Since a large amount of a plasticizer, such as DOP, DOA, etc., is incorporated, these films would have the problems in that the amount of permeating water vapor would increase, and a wrapped article would likely be altered, that these plasticizers would likely migrate to a wrapped article thus contaminating the article, that a gas of the plasticizer and a corrosive chlorine gas would be generated when the film is fused during a wrapping work, which would be hygienically undesirable, that a toxic gas would be generated when a used film is incinerated, and that the film would become less flexible and fragile and would be likely to break due to its poor resistance to cold when a wrapped article is preserved at a low temperature, which is as already described.
Meanwhile, single-layered films formed of a high-density polyethylene, a low-density polyethylene and a PP-based polymer among the generally usable polyolefins have excellent properties over the above defects. However these films do not have the other important properties required for use in the field to which the present invention is directed to. It has not been possible to form a practically usable stretch wrapping film which satisfies all of the following characteristics as a wrapping film. That is, any film for use in stretch wrapping is required to satisfy the following properties simultaneously.
a. The film is to be excellent in film-film adhesion.
b. The film is to have a proper degree of (excellent) recoverability from deformation, a proper degree of elastic elongation and high mechanical strength.
c. The film is to have a proper degree of lubricity.
d. The film is to be excellent in optical properties such as transparency and gloss.
e. The film is to a proper degree of gas permeability.
f. The film is to retain no water drops and to be excellent in anti-fogging property.
g. The film is to be excellent in wrapping workability.
h. The film is to have heat resistance sufficient to endure heat in sealing.
For example, when an unstretched film of PP is stretched, it causes a phenomenon called necking, that is, it is locally stretched and the thickness becomes extremely nonuniform. Even after a load is removed, the stretched portion remains as is. Therefore, the appearance of a wrapped article is extraordinarily impaired, and the purpose in wrapping is not achieved. A stretched film of the same is hard, strong and little extendable so that a very large force is required to extend it, and an article being wrapped would be destroyed. This film is also without any adhesion properties, and it is therefore required to incorporate as much as 5% by weight of a plasticizer such as low-molecular-weight polybutene in order to impart it with stretchability and adhesion properties. In this case, however, since polyolefin is, unlike PVC, not at all capable of retaining the plasticizer, most of the plasticizer bleeds out on the surface and makes the surface sticky, and such a film is not suitable for practical use.
A high-density polyethylene is also too hard to simply stretch. Even if stretched forcibly, it causes a nonuniform thickness due to necking, and results in a similar result. Further, it is all opaque or without gloss and cannot be put to practical use.
Films formed from low-density polyethylenes are much softer than the above film. However, unstretched films of this type cause a necking phenomenon in packaging, and they have little recoverability from deformation, low strength, low transparency, film-film adhesion property poor and a problem in practical use. Therefore, they cannot meet the object of the present invention. Further, when these films are sufficiently stretched (e.g., at an area stretch ratio of 20 times) at a temperature equal to or higher than the melting point according to a conventional method after imparted with a crosslinked structure by electron beam and rendered easily stretchable, the resultant films have the same defects as those of PP, and they cannot be used as a substrate for stretch packaging which is an object of the present invention.
A film formed from an elastic elastomer having nearly complete recoverability from deformation such as a styrene-butadiene copolymer and a rubber substrate formed from other material is free from a phenomenon of said necking. However, such a film has problems concerning optical, properties and hygienic storage of food. Besides these, the stress strength of elongation is nearly completely in proportion to the degree of elongation, and the response in recovery from deformation instantaneously occurs without any delay. There is therefore a problem in that the film takes its original shape immediately before the end portion of the film is set under an article to be wrapped or a tray. Thus, such a film has properties due to which it can be hardly employed for the use of the present invention.
Of these polyolefin-based films, those that are produced by mixing a main component such as linear low-density polyethylene, particularly an ultra-low-density polyethylene, crystalline 1,2-polybutadiene and an ethylene-vinyl acetate copolymer (EVA) with an anti-fogging agent and a tackifier and by forming the resultant mixtures into films by conventional methods (T-die method and air-cooling inflation method) are on trial in the market. However, these films have many of the defects as described above, and presently have not as yet arrived at the level of replacing conventional films.
These films cannot satisfy all of properties which are mutually contradicting such as easiness in elongation in wrapping, heat resistance of a sealing portion, easiness in sealing and prevention of breach in wrapping caused by insufficient film strength, and have unsatisfactory properties. For example, in an EVA film, it is required to increase the content of vinyl acetate (VAc) in EVA in order to make the film easily elongated. In this case, however, the bottom portion (under the tray) tends to be melted under heat and becomes broken in sealing. To prevent this, it is required to increase the film thickness from 16 .mu.m up to 20 .mu., 22 .mu. or 24 .mu.. When the film thickness is increased, however, the defects of the film also increases. That is, it is difficult to elongate the film, the film hardly adheres to the film before sealing, and the film is likely to break due to its decreased strength. Further, the film cost disadvantageously increases.
When other polymers, particularly a low-density polyethylene (particularly a linear type one) or PP-based rubber is incorporated, another problems arise. That is, the important properties such as transparency and gloss tend to be decreased.

Shrinkable, stretchable multi-layered film


The invention teaches a new way to make mesh bags using adhesive labels and continuous mesh tubing. Using adhesive labels on continuous mesh tubing is made possible by guiding the mesh tubing both on the outside of the tubing and the inside of the tubing so that an adhesive label does not stick to the mesh surface on the other side of the mesh tubing. As a result the invention also teaches a new type of mesh bag made with this process and a new machine used for making mesh bags.

1. Technical Field of the Invention
The present invention generally relates to the field of designing and manufacturing of packaging bags such as woven or mesh bags for containing onions, potatoes, citrus, nuts, fruits, or other produce. More particularly, the invention is related to a tube mesh bag coupled with pre-printed labels and the apparatus and method for manufacturing the same.
2. Description of the Related Art
Mesh bags have been widely used in commercial packaging and storing, laundry, as well as sports. More particularly, light weight and heavy duty mesh bags are widely used for packaging and storing fruits, nuts, onions, garlic, and etc. As with other containers of consumer products, labeling is needed to give notice of the brand of the product as well as to convey relevant information. The prior art's solutions for labeling are inferior to the present invention because they are lacking either in visibility, cost effectiveness, or aesthetics.
Prior art labeling methods on tube mesh included stitching the preprinted label on or tying it on. These methods are aesthetically lacking and/or are easily torn off or damaged in transport since they are only attached at one or two edges of the label.
Adhesive pre-printed labels are an aesthetic improvement since the label is entirely bonded to the mesh bag and does not have portions of the label hanging off the bag or unbounded edges such as the stitched or tied prior art labels. Thus, this type of label is superior to the prior art methods of labeling tube mesh bags.
Traditionally these adhesive pre-printed labels were used only on bags made from sheets of mesh. The sheet of mesh would then need to be sealed on two sides to create an open bag and three sides to form a closed bag. On the other hand, mesh tube could be sealed on one side to form an open bag and 2 sides to be sealed for a closed bag resulting in lower production costs. If the self adhesive heat activated preprinted labels could be used with tube mesh, then a mesh bag can be made with all the advantages of using adhesive labels, along with the lower costs of using tube mesh.
But, the machines which applied these labels must be used on sheets of mesh. Tube mesh could not be used with these machines because when they press the label onto the tube mesh, the other side of the tube mesh would also stick to the adhesive label, rendering the mesh unusable as a bag. Thus, a machine which can efficiently place these adhesive labels on tube mesh is desired.
The prior art in FIG. 1 shows a tube mesh bag 10 with a label 14 attached to a twist tie instead of on the bag itself. The label attached is small and thus is not very visible. Though the produce 11 inside the bag can be seen, the brand of the product would not be recognizable from a distance. Further the tag is attached to the bag by a twist tie 13 and could be easily torn off. Though this method may be cost effective, it is lacking in visibility and aesthetics.
The prior art in FIG. 2 shows a tube mesh bag with a label 221 222 tied to the bag at both ends using twist ties 23 24. This method allows the use of a larger label since it is held on at both sides. It is cost effective since the label is just tied on at the same time as the twist ties are secured. But the label is aesthetically lacking.
The prior art in FIG. 3 shows a tube mesh bag 30 which is stitched together at the bottom 34 and has a label 32 stitched at the top 31. This method is improved from the previously shown prior art in aesthetics and visibility, but it makes the package larger than necessary and can get wrinkled or bent easily during transport of the product.
The prior art in FIG. 4 shows a mesh bag which was made from a sheet of mesh 50 using adhesive labels 51. The adhesive labels are aesthetically superior to the other prior art labels and their size allows them to be easily read. They also do not increase the size of the package nor get damaged easily during transport the way the prior art shown in FIG. 3 does. These labels are primarily used on bags made from sheets of mesh rather than tube mesh since directly pressing the label onto a section of tube mesh would cause the other side of the tube stick to the label as well. But since sheets of mesh were used with this type of label, two sides of the mesh must be sealed 52 53 to form an open bag 54. A closed bag would require 3 sides to be sealed. Each set of seals results in added cost to the production of the bag.
What is desired is a tube mesh bag to which a pre-printed label is coupled using a dynamic guiding system to prevent the adhesive materials from being attached to the other side of the mesh tube.


For utilizing the chemical energy of a sugar directly as electric energy, electrolytic oxidation of a sugar on the negative electrode associated with cleavage of a carbon-carbon bond thereof is employed, thereby generating an electromotive force between the positive electrode and the negative electrode having an electrolyte therebetween. For an efficient oxidation of a sugar, it is effective for the negative electrode to have a component capable of forming a coordination compound with a sugar via a hydroxyl group thereof. Such a component may comprise a metal element capable of forming an amphoteric hydroxide. Use of an oxygen electrode as the positive electrode gives a battery capable of efficiently converting the chemical energy of a sugar into electric energy.

The present invention relates to a method for generating an electric power and a battery utilizing a sugar as a source of energy.
Like protein and lipid, sugar is an important energy source for animals. Glucose represented by the chemical formula: C6H12O6 is a typical example of a sugar. When one glucose molecule is completely oxidized, 24 electrons are taken out of it, and carbon dioxide and water are produced. These 24 electrons are utilized as energy in the body of any animal. According to the thermodynamic calculation, glucose has an energy of 2872 kJ per mol or 4.43 Wh per gram. This energy density is higher than 3.8 Wh/g, which is the weight energy density of metallic lithium used for the negative electrode of a lithium battery known to have a high energy density.
However, the methods of utilizing the energy of sugar, have not been developed so far except methods utilizing it as heat energy source through combustion thereof in air or as chemical energy source used for ATP or the like through the action of 10 or more oxidases in an animal body (see Alberts et al., Essential Cell Biology, Garland Publishing, Inc. 1997, p107). Specifically, no method have been produced of effectively utilizing the chemical energy of sugar directly as electric energy.

Battery and method for generating an electric power

Matsushita Electric Industrial Co., Ltd.


An apparatus for diagnosis of ocular surface disease includes an electronic tablet with an electronic display and a forward-facing camera. The camera may be placed above the screen when the device is held in landscape mode. A software app executing on the electronic tablet displays a test screen to a patient, the test screen comprising a test image and an alignment indicator. Once alignment is achieved, the patient may read the test image for a period of time, during which blink quality and quantity are tabulated. A video recorded during the test may be reviewed by a physician to confirm or modify blink quality and quantity counts during the test to diagnose ocular surface disease.

Ocular surface disease is a broad term that describes disorders of the surface of the cornea of the eye. These diseases include dry eye syndrome, meibomian gland dysfunction, blepharitis (eyelid inflammation), allergies, scarring from glaucoma medications, burns such as chemical or thermal burns, rosacea, allergies, and immunological conditions such as mucous membrane pemphigoid and Sjorgren's syndrome. These diseases can impact quality of life, and in some cases can severely affect eyesight, even resulting in blindness due to corneal scarring. These diseases often go undiagnosed and thus untreated, however, due to a lack of understanding of symptoms and inaccurate evaluation. Many patients simply feel that dry eyes at the end of the day are a "normal" occurrence and therefore do not seek medical attention. Nevertheless, early diagnosis is critical to effective treatment of many forms of ocular surface disease. Since a number of the causes of ocular surface disease occur more frequently in the elderly, the disease will continue to impact a larger and larger proportion of the population as the average lifespan of the population increases.
Inefficient or insufficient blinking is associated with certain types of ocular surface disease such as dry eye syndrome. Blinking is what triggers the expression of meibum, an oily substance that prevents evaporation of the eye's tear film and also prevents tear spillage onto the cheek. Blinking is also critical to the redistribution of essential nutrients in the tear film. Without a proper and complete blink at regular intervals, the meibum sits stagnant and thickens at the gland orifice from which it is secreted. Eventually gland blockage can occur, which leads to gland atrophy. Some current research indicates that the long-term viewing of electronic video displays, computers, electronic tablets, smartphones, and other such devices may lead to poor blinking habits, thus increasing ocular surface disease in an age when a large proportion of the population is viewing these devices for many hours per day.
Currently, diagnosis of ocular surface disease occurs, if at all, during a routine eye and vision examination. A more in-depth evaluation of the ocular surface and adjoining adnexa may be performed based on the patient's history, an assessment of associated risk factors, and examination of the anterior ocular structures and their functions. This often follows specific complaints by the patient, such as burning or stinging in the eyes, scratchiness, irritation, increased mucous, or reduced contact lens tolerance. By the time these factors are present, however, the disease may be well progressed. The prior art lacks a simple and effective method of diagnosis of this disease that can be performed routinely and inexpensively in a typical clinical setting in order to achieve an earlier diagnosis of ocular surface disease, and thus lead to a treatment that is more likely to be efficacious and less invasive for the patient.
Any references mentioned in this background section are not admitted to be prior art with respect to the present invention.

Apparatus for diagnosis of ocular surface disease


An electronic apparatus includes: an operator; and a power circuit configured to supply power to the operator, wherein the power circuit includes a first voltage converter configured to output a first voltage based on input power, and a power factor corrector (PFC) configured to output a second voltage by performing power factor correction for the first voltage, and supplies power based on the first voltage or the second voltage to the operator, wherein the power circuit stops an operation of the PFC, lowers the first voltage to have a level corresponding to the second voltage, and supplies power based on the lowered first voltage to the operator, based on power consumption of the operator lower than or equal to a predetermined value.

In alternating current (AC) circuits, voltage and current are varied in a sinusoidal waveform, but there may be cases where the sinusoidal waveforms of them are out of phase with each other, or the current has not the sinusoidal waveform but a pulse waveform. These cases cause a ratio of really used active power to the apparent power, in other words, the power factor (PF) to decrease, thereby increasing energy loss.
Therefore, a power circuit of a television (TV) or the like electronic apparatus that receives AC power includes a power factor corrector (PFC) to correct the power factor as far as possible.
With recent trends of the electronic apparatus having various additional functions, the TV or the like electronic apparatus may perform only an operation of a light load, i.e. low power consumption mode, such as a gallery mode, a picture-frame mode, a clock mode, an Internet-of-things (IoT) mode, etc. without performing a general TV operation of processing and displaying an image signal containing a broadcast in a partial section.
In such a light-load section of the low power consumption, there are no needs of satisfying power factor restraints, and therefore it is possible to reduce one stage in power conversion of the power circuit by turning off the PFC and thus making voltage to bypass the turned-off PFC, thereby improving the whole system efficiency.
The PFC is designed as a step-up PFC circuit or a step-down PFC circuit according to environments and the like conditions. The step-up PFC circuit is designed to have an output to which devices having a voltage rating higher than a PFC input voltage are connected, so that the voltage can bypass the PFC without difficulty.
The step-down PFC circuit is designed to have an output to which devices having a lower voltage rating than that of the step-up PFC circuit, and thus the step-down PFC circuit may be used as the PFC under a specific condition.
However, when the PFC is given as the step-down PFC circuit, the PFC works for only a voltage drop even in the light load section where the power factor correction is not required, and therefore a problem of lowering the whole system efficiency arises in the light load section.

Electronic apparatus including operator and power circuit configured to supply power to the operator


A reading circuit including a detection module, a first transistor, and a compensation module is disclosed. The detection module detects a light. The first transistor transforms the detection result for generating a current signal. The compensation module compensates a threshold voltage of the first transistor.

1. Field of the Invention
The invention relates to a reading circuit, and more particularly to a reading circuit for obtaining the intensity of a light.
2. Description of the Related Art
With the development of technology, input devices for electronic products have achieved great diversity. In various input devices, touch panels are widely used in the display arrays of liquid crystal displays (LCDs), thus, the capability to input data via the display panel of an LCD. When touch panels are utilized for data input, conventional input devices, such as keyboards and mice, are eliminated, thus, usable space is increased. In various electronic products, such as a personal digital assistant (PDA), a notebook computer (NB), a personal computer (PC), and a mobile phone, touch panels are served main input devices and gradually replace the conventional input device
Because the number of communication and electronic products has increased substantially and because products frequently utilize touch panels as input devices, much research has been devoted to touch panel contact techniques. The response method of the touch panel comprises a photo detection method utilizing a sensor produced by a low temperature poly-si (LTPS) technique. Because the sensitivity of the sensor is lower, a thin film transistor (TFT) is utilized to read the detected result provided by the sensor.
TFTs in different positions, however, have different threshold voltages due to manufacturing procedures. When two sensors detect lights having the same intensity, the TFTs are not able to provide the same reading result due to the different threshold voltages.

Reading circuit, display panel and electronic system utilizing the same