A method controls the operation of a mobile station, the operation including camping which modellable as a number of states (S1 to 4) with predetermined state transitions (S12-S34) between them. Each one of the states corresponds to a set of locally varying features which the mobile station currently supports. The features include a first feature indicating whether the mobile station is in circuit-switched mode or packet switched mode, and a second feature indicating whether or not the mobile station is in localized service area (LSA) model. For all combinations of the first and second features there is a corresponding state (S1 to S4), and for each one of these states there are two originating state transitions and two terminating state transitions, each one of the originating state transitions corresponding to a change in the respective feature.

The invention relates to cell selection in a mobile telecommunications network which comprises a packet radio network. An example of such networks is a combined GSM/GPRS network.
A mobile station (MS) in a cellular system, when switched on, selects the most suitable cell. Later, when the MS is in idle mode (i.e. not having a call in progress) and it is camped normally on a cell of the selected PLMN, it monitors its neighbouring cells for a possible handover, in case one of the neighbouring cells provides better service. This process is called cell reselection. The GSM/GPRS cell reselection chapters are based on ETSI recommendations GSM 03.22, GSM 03.60, GSM 03.64 and GSM 05.08. These recommendations are incorporated herein by reference, but for convenience, the parts of those documents which are essential for understanding the invention are repeated in this application.
Cell reselection in GSM
A cell reselection can be triggered if a path loss criterion parameter C1 indicates that the path loss to the cell has become too high; or the current serving cell has become barred; or there is a better cell in terms of the cell reselection parameter C2 in the same LA, or a much better cell in another LA of the selected PLMN. There are other reasons for a cell reselection but they are not essential for understanding the invention (such as a downlink signalling failure, or a random access attempt fails after a certain number of repetitions).
The MS will reselect a new cell in order to achieve the following conditions which are commonly referred to as a xe2x80x9cnormal service statexe2x80x9d: a) The registered PLMN is the selected PLMN; b) The MS is camped on a suitable cell of the LA on which the last successful LU was performed, and that cell has the highest value of C2 for any unbarred cell in that LA; c) The value of C2 for the MS is not lower than the value of C2 for any suitable cell in another LA of the selected PLMN by more than the hysteresis value CRH (Cell Reselect Hysteresis).
There may be temporary conditions under which not all these are fully satisfied, e.g., during cell selection on a PLMN or while in the process of reselecting another cell. However, if the above cannot be satisfied for a certain period of time, the MS will normally enter a limited service state in which it will try to camp on an acceptable cell. In this state, only emergency calls are possible.
Parameters C1 and C2 are used to ensure that the MS is camped on the cell with which it has the highest probability of successful communication on uplink and downlink. The MS uses C1 to determine whether a cell is suitable to camp on, C1 depends on 4 parameters: i) RLA (Received Level Average) is the received signal level suitably averaged; ii) RXLev_Access_Min which is broadcast on the BCCH, and is related to the minimum signal that the operator wants the network to receive when being initially accessed by an MS; iii) MS_TXPWR_MAX_CCH which is also broadcast on the BCCH, and is the maximum power that an MS may use when initially accessing the network; and iv) P which is the maximum power of the MS.
Use of the parameter C1 enables the MS to determine whether communication is possible with the network in the absence of interference. However, an additional safeguard against interference is used. This is to monitor the success rate of the MS in decoding signalling blocks of the paging subchannel. If there is a downlink signalling failure, i.e. the success rate drops too low, this indicates probable interference on the downlink, and the MS attempts to find another suitable cell. The path loss criterion parameter C1 used for cell selection and reselection is defined by:
C1 =(Axe2x88x92Max(B,0)),
where
A=RLAxe2x88x92RXLev_Access_Min
B=MS_TXPWR_MAX_CCHxe2x88x92P
All values are expressed in dBm. The path loss criterion is satisfied if C1 greater than 0.
In order to optimize cell reselection, additional cell reselection parameters can be broadcast on the BCCH of each cell. The cell reselection process employs a parameter C2 that depends on these parameters. The parameters used to calculate C2 are as follows:
Cell_Reselect_Offset which applies an offset to the C2 reselection criterion for that cell.
Penalty_Time: When the MS places the cell on the list of the strongest carriers, it starts a timer, which expires after the Penalty_Time. This timer will be reset when the cell is taken off the list. For the duration of this timer, C2 is given a negative offset (Temporary_Offset). This will tend to prevent fast moving MSs from selecting the cell. The all ones bit pattern on the Penalty_Time parameter is reserved to change the sign of Cell_Reselect_Offset and the value of Temporary_Offset is ignored as indicated by the equation defining C2.
Temporary_Offset which applies a negative offset to C2 for the duration of Penalty_Time after the timer T has started for that cell. An infinite value can be applied, but a number of finite values are also possible.
Timer T is implemented for each cell in the list of strongest carriers. T is started from zero at the time the cell is placed by the MS on the list of strongest carriers, except when the previous serving cell is placed on the list of strongest carriers at cell reselection. In this, case, T is set to the value of Penalty_Time (i.e. expired).
The reselection criterion C2 is used for cell reselection only and is defined by:
C2=C1+Cell_Reselect_Offset_Temporary_Offset*H(Penalty_Timexe2x88x92T) for Penaltyxe2x88x92Time less than   greater than 11111
C2=C1xe2x88x92Cell_Reselect_OffsetforPenalty_Time=11111
for non-serving cells:
H(x)=0 for x less than 0; and H(x)=1 for x greater than =0; and for serving cells: H(x)=0
Cell reselection in GPRS
In order to receive GPRS service, a cell reselection may be required. When the MS is in GPRS Idle state and it wishes to initiate a GPRS attach procedure, the following applies. If the currently camped-on cell supports GPRS then no cell reselection is required. If the currently camped-on cell does not support GPRS, then reselection of a cell supporting GPRS is required before execution of the attach procedure. If, however, the MS is in GPRS Standby or Ready state, cell selection and reselection procedures specific to GPRS are used (GPRS mode). Instead of the parameters C1 and C2, a GPRS MS applies the corresponding GPRS parameters C31 and C32, if provided. If the MS is in active mode, then the changes from one cell to another is performed according to the GSM handover procedures.
In GPRS Standby and Ready states, the MS performs cell reselection, except for a class A MS while in a circuit switched connection, in which case the cell is determined by the network according to the GSM handover procedures. The GPRS mode cell reselection procedures apply to the MSs attached to GPRS if a PBCCH (Packet Broadcast Control Channel) exists in the serving cell. Otherwise the MS shall perform cell reselection according to the GSM idle mode procedures. Optionally, the network may control the cell selection.
The cell reselection criteria C31 and C32 are provided as a complement to the current GSM cell reselection criteria. This provides a more general tool to make cell planning in GPRS as similar as possible to existing cell planning in GSM. The GPRS specific cell reselection algorithm is only applicable if the PBCCH is allocated. If the PBCCH is not allocated, the MS shall perform cell reselection according to the C2 criteria. The following cell reselection steps shall be followed, wherein (s) and (n) denote serving cell and neighbor cell respectively: 1) Path loss criterion (C1). The path loss criterion C1 greater than =0, is used as a minimum signal strength criterion for cell selection for GPRS in the same way as for GSM in Idle mode. 2) Signal strength threshold criterion (C31) for hierarchical cell structures (HCS). 3) Cell ranking (C32). 4) Cell reselection rules.
The MS selects the cell having the highest C32 value among those having the highest priority class and fulfilling the criterion C31 greater than =0. The priority classes may correspond to different HCS layers. They may also be used for other purposes. If no cells fulfil the criterion C31 greater than =0, the MS selects the cell having the highest C32 value among all cells.
The HCS signal strength threshold criterion (C31) is used to decide whether the cell is qualified for prioritized hierarchical cell reselection.
C31(s)=RLA(s)xe2x88x92HCS_THR(s) greater than =0, (serving cell)
C31(n)=RLA(n)xe2x88x92HCS_THR(n) greater than =0, (neighbour cell)
where HCS_THR is the signal threshold for applying HCS reselection.
The cell ranking criterion (C32) is used to select cells among those with the same priority:
C32(s)=C1(s)+GPRS_Reselect_Offset(s), (serving cell)
C32(n)=C1(n)+GPRS_Reselect_Offset(n)xe2x88x92Temporary_Offset(n)*H(Penalty_Time(n)xe2x88x92T(n)), (neighbour cell)
where GPRS_Reselect_Offset applies an offset and hysteresis value to each cell;
H(x)=0 for x less than 0; and H(x)=1 for x greater than =0
Network Controlled Cell Reselection
It is possible to order an MS in Ready state to send a measurement report to the network. The measurement report is a regular packet transmission, addressed to the proper network entity. It also is possible for the network to order an individual MS in Ready state to perform cell reselection to a cell appointed by the network, possibly in combination with a penalty parameter to keep the MS from returning to the original cell immediately. A network induced cell reselection temporarily overrides the MS originated cell reselection.
The degree to which the mobile station shall resign its radio network control is variable, and is specified in detail by the parameter Network_Control_Order. The following actions are possible to order to the mobile stations. NC0: normal MS control (the MS performs autonomous cell reselection); NC1: MS control with measurement reports (the MS sends measurement reports to the network according to additional information in the message NC1. It continues its normal cell reselection. NC2: Network control (the MS sends measurement reports to the network according to additional information in the message NC2. It performs no cell reselection on its own, and can only make a cell reselection according to a cell reselection command received from the network.
Two sets of parameters are broadcast on PBCCH and are valid in Transfer and Wait states respectively for all mobile stations in the cell. Network_Control_Order can also be sent individually to an MS on PACCH, in which case it overrides the broadcast parameter.
The measurement reports are sent individually from each MS as RLC transmissions, addressed to the RR management in a BSS. The measurement reporting is maintained in the MS RR states Wait with Cell Update and Transfer and in the BSS RR states Measurement Report Reception and Transfer.
The cell reselection commands include: 1) target cell channel description (GSM 04.08); 2) penalty to prevent immediate return (3 bits); and 3) penalty timer (5 bits).
There may appear exceptional situations where the network controlled cell reselection procedures (NC1 or NC2 modes of operation) should not be used:
1. When a class A mobile station is simultaneously involved in a circuit switched service and in a GPRS transfer. In this case, handover for the circuit switched service has precedence over GPRS network controlled cell reselection. In order to avoid that measurements are reported twice by the MS (once for the GPRS resource, once for the circuit switched resource), thus leading to inefficient usage of the radio bandwidth, network controlled cell reselection should not be activated in this case. 2. When an MS is performing a process called Anonymous Access, cell reselection implying a change of routing area results in the MS returning to the GPRS MM Idle state. Therefore, there might be cases where the network controlled cell reselection would result in a failure of the Anonymous Access.
Since the BSS is not able to detect such situations, the MS must inform the BSS when such a situation is encountered, so that the BSS can select a more appropriate mode of operation. This coordination procedure is as follows. When an MS in Transfer or Wait state has been asked by the network to behave according to the NC1 or NC2 modes of operation and the MS encounters one of the above mentioned situations, it continues reporting measurements and it will not obey the network controlled cell reselection commands, if received. As soon as an uplink transmission opportunity occurs, the MS informs the network that the requested mode of operation should be suspended. It is up to the network to decide whether to maintain or to change the mode of operation. The network replies with the value to be used. The MS adapts its behaviour accordingly. If no answer is received from the network, the MS assumes no change and continues to inform the network, as described above, until an answer is received.
When the situation which triggered the above mentioned actions ends, and provided that the MS is still in Transfer or Wait state, as soon as an uplink transmission opportunity occurs, the MS informs the network that the initial mode of operation (NC1 or NC2) may resume. It is up to the network to decide whether to maintain or to change the mode of operation. The network replies with the value to be used. The MS adapts its behaviour accordingly. If no answer is received from the network, the MS assumes no change (i.e. it continues to apply the last value received from the network) and it continues to inform the network, as described above, until an answer is received.
Localized Service Areas (LSA)
In cellular mobile communications systems, a mobile station may roam freely within the area of the mobile communications network and connect to the base transceiver station signal received best at a given time. Usually, all base transceiver stations provide substantially similar services for the mobile stations in a network. Some base transceiver stations can, however, be defined to provide a certain special service for all mobile stations of the network, e.g. call charges below the normal tariff. The base transceiver station broadcasts a message on such a special service on its broadcast control channel (BCCH), whereby mobile subscribers in the area note that they are within a special service area of the network and may take advantage of this service.
Within the context of this application, such special service areas are referred to as localized service areas (LSA) and the support of LSA is called SoLSA. A subscriber having SoLSA service is called a SoLSA subscriber. A mobile station currently having support for SoLSA is said to be in LSA mode. This could mean e.g. that the mobile station indicates to its user that certain special features (like lower rates or extra services) are available, and it uses these features when applicable. SoLSA for a GSM environment is described in a proposal to ETSI (European Telecommunication Standard Institute), document Tdoc 98S147. For convenience, the subject matter of the ""147 document is repeated here in a somewhat rearranged form.
Within the GSM standards there are features and capabilities defined which allow groups of subscribers to be managed according to a number of operator specific criteria, e.g. CAMEL, USSD, SIM Application Toolkit (SAT) and xe2x80x9cMultiple Subscriber Profilexe2x80x9d. Future trends in GSM system platform development are towards customised system solutions where, for example, radio access solutions will be enhanced to take into account indoors environment (micro and picocells) such as office buildings. New means to provide radio access solutions together with service and tariff packages (e.g. flat rate charging) can be introduced.
The concept of LSA extends the operator""s capability to offer different service features to subscribers or subscribers groups, different tariffs and different access rights depending on the location of the subscriber. Examples of LSAs are indoors office cells (those provided by indoors base stations); a home or an office and its neighbourhood, an industry area (covering all company buildings and the space between), or a part of a city or several locations.
Support of LSA (SoLSA) can be specified as a set of service features which are used in conjunction with existing toolkits, e.g. CAMEL and SAT. For example CAMEL phase 2 functionality already provides the means to offer cell based applications, as a CAMEL Service Environment (CSE) can be aware of the cell from which a call was originated. CSE capabilities include e.g. modified charging and barring of calls based on cell information. However, operators typically have several service platforms. It should be noted that CAMEL is but one example of a platform for the SoLSA concept.
SoLSA can enhance radio specific support for an LSA by standardising one or more of the following: definition of an LSA, LSA indication, LSA support (in idle mode (camping), or in active mode (handover)), LSA only access, exclusive access, and preferential access.
FIG. 1 shows the parts of the mobile network system that are essential for understanding the invention and FIG. 2 illustrates the concept of SoLSA. Subscriber-specific LSA information can be stored and managed either in the CSE or in the Home Location Register HLR. Two types of LSAs can be foreseen, either a truly customised LSA for a small office area and a residential area (xe2x80x9coffice/home zonexe2x80x9d), or a predefined LSA covering large campuses, sections of cities and districts (xe2x80x9ccity zonesxe2x80x9d) etc. These two LSAs fulfil different needs. They complement each other and they can be used simultaneously. A SoLSA subscriber can have a home LSA consisting of 1 or 2 cells; an office LSA consisting of 1 to 5 cells and a city LSA with dozens or hundreds of cells. The first two LSAs are preferably tailored on a per-subscriber basis. A truly subscriber-specific LSA can be defined on a cell identity basis and it is possible to define it as small as possible, consisting of even only one cell, if necessary. The third LSA could rely on a certain predefined LSA definitions. LSA information can consist of:
List of cell identities belonging to an LSA (Cell identity can be defined as specified in GSM 08.08, e.g.: Cell Global Identity (MCC+MNC+LAC+Cl), MNC+LAC+Cl LAC+Cl or Cl).
LSA_ID (The LSA ID is a number uniquely assigned to an area in one network. LSA ID can be associated with a Cell Identity list.)
LSA name (a text string describing area and/or service, e.g. xe2x80x9cEtsi Buildingxe2x80x9d).
LSA indication (a flag to activate/deactivate LSA indication)
LSA priority (a number value needed to support overlapping LSAs, for example city zone and office cells in same area).
LSA only access (Service outside LSAs is restricted).
LSA only access indication text (Text to be displayed when out of LSA area).
Exclusive access (User has exclusive access to a LSA).
Relevant MSP profile (an LSA may be associated with some MSP profiles).
Idle/active mode support (preferred cell selection in idle/active mode may be utilised in an LSA).
Examples of LSA Information
LAC+Cl, xe2x80x9cHomexe2x80x9d, Priority=3, MSP Profile 1
LAC+Cl, LAC+Cl, LAC+Cl, LAC+Cl, xe2x80x9cCorporatexe2x80x9d, Priority=1, MSP Profile 2 (a user with two LSAs)
LSA_ID=1234, xe2x80x9cCorporatexe2x80x9d, Priority=1, Excl_access=yes, Active mode support=mandatory
MCC+MNC+LAC+Cl, MCC+MNC+LAC+Cl, xe2x80x9cMoU at Fijixe2x80x9d Priority=2 (a user with exclusive access and LSA in VPLMN)
LSA Only Access=yes
OutOfLSA=xe2x80x9cNo calls allowedxe2x80x9d
LAC+Cl, LAC+Cl, LAC+Cl, LAC+Cl, xe2x80x9cCorporatexe2x80x9d, (a user with limited mobility)
The subscriber""s LSA information can be stored within the subscriber""s SIM. This information can be initially stored by the operator for new subscribers. The operator can manage LSA information in a SIM by using SIM data download of SAT (SIM Application Toolkit), USSD (Unstructured Supplementary Service Data) or SMS (Short Message Service), by concatenating multiple short messages if necessary.
LSA information transfer from the CSE can take place any time. At least it takes place when the subscriber""s LSA parameters are changed, e.g. due to possible changes in the radio network""s configuration. The MS can receive the LSA information for cell reselection procedures etc.
Idle mode support makes the behaviour of the MS more consistent and reliable in an LSA. A preferential cell reselection mechanism can be defined so that when camping on a cell in idle mode (MS in SERV state), the subscriber""s MS favours the cells belonging to his/her LSA. The MS shall always attempt to reselect a cell in a higher priority LSA. This requires new functionality in the MS. The MS can recognise the LSA by the LSA_ID or a cell id list stored in the SIM.
FIGS. 3 to 4 illustrate cell reselection in SoLSA. GSM phase 2 defines the above parameters C1 (for normal cell selection) and C2 for cell reselection). C2 is evaluated for the six strongest neighbouring cells, and the cell with the highest priority and C2 is reselected. If there are more than one LSA cell available which meet the reselection criteria, the highest LSA priority cell is selected.
For normal cells the calculation of C2 involves a parameter RXLev_Access_Min, but for LSA cells the LSA_RXLev_Access_Min is used instead. The value for the parameter is broadcast to the MS for each cell in the system information messages.
For SoLSA, a new parameter LSA_Camping_Margin is also broadcast to the MS for each cell in the system information messages. If the C2 of a lower priority LSA cell or a normal cell exceeds the C2 of an LSA cell by this margin, the LSA MS will no longer camp to the highest priority LSA cell even if its C1 is positive. This can be realised by adding LSA_Camping_Margin and (LSA_RXLev_Access_Minxe2x88x92RXLev_Access_Min) to the C2 of the LSA cells. This causes the MS to favour the LSA cells and minimises the negative effect of LSA mobiles on the network""s spectral efficiency.
New parameters can be added to appropriate system information messages to enable broadcasting of the LSA cell reselection parameters. These new parameters are transferred to the BSS from the OandM with other radio network parameters. Existing cell reselection parameters will affect the behaviour of all GSM subscribers in the same way. For SoLSA, there is a need for customer-specific idle mode supporting parameters. This enables SoLSA to handle LSA customers in e.g. traffic hot spots and in office environments without affecting regular GSM customers.
A Base Station Controller BSC needs subscriber-specific LSA information to favour LSA cells during active mode. This information can be delivered to the BSC from an MSC (Mobile services Switching Centre) during call setup and inter-BSC handover by using existing BSSAP messages or proprietary messages. The LSA information should identify the LSA cells, LSA priorities and the LSA-only access indicator. The MSC can retrieve the LSA information from the CSE or from the Visitor Location Register VLR, if available.
During inter-BSC handover, the LSA information can be delivered from the source BSC to the target BSC by including the LSA cell list to the HANDOVER_REQUEST and HANDOVER_REQUIRED messages (each of which will require a new information element). The transfer of the LSA information between the BSSs is transparent to the MSC.
A subscriber-specific identifier can be assigned to each LSA (e.g. an alphanumeric text or an icon). This identifier can be provided to a user in idle or active mode. It is also possible to indicate a change of the LSA during idle and active mode. The indication is a network option (activated/deactivated by the network). When the subscriber moves into and away from his/her LSA, the LSA indication may be given by the MS, as guided by the LSA indication bit. In the idle mode the MS can indicate the LSA e.g. by displaying the LSA name string (e.g. xe2x80x9cEtsi Buildingxe2x80x9d), an icon, or another signal to the subscriber, as a result of camping on a LSA cell.
An exclusive access (EA) feature makes it possible to guarantee that the members of a user group are the only users of the radio channels (physical resources) within a cell. In order to support EA in idle mode, other users"" mobile stations must be prevented from camping to that cell. This can be done by using a Cell_Bar_Access parameter. Users whose LSA the cell belongs to shall ignore the Cell_Bar_Access parameter and camp to an LSA cell normally. In order to bar the cell also for LSA users, a new broadcast parameter LSACell_Bar_Access can be used.
In order to support EA in active mode, handovers of non-EA LSA users to EA LSA cells should be prevented. This feature could be supported e.g. by flagging EA cells in the BSC and permitting handovers to EA cells only for users for whom a matching LSA id information is found in the LSA information delivered to the BSC. An LSA only access (LO) feature makes it possible to restrict the users"" access to a defined area. Originating and/or-receiving calls outside that area can be prevented. It is also possible to prevent handovers to cells not belonging to allowed LSAs. In idle mode a MS with LO is only allowed to access cells that are defined in the subscriber""s LSA information. All cells with no match with the LSA information stored in the SIM is regarded as not suitable. An indication can be given to the user (e.g. a text string like xe2x80x9cNo Service Allowedxe2x80x9d). If LO is set and a non-LSA cell is-selected, only emergency calls are allowed.
To support LO during active mode, the BSC can compare each handover candidate cell with LSA information delivered to the BSC and permit handover only if a match is found. CAMEL CSE (or NSS) may be used to prevent call attempts (MO and/or MT) outside LSA area as required by SoLSA application.
Preferential access (PA) means the ability to favour the allocation of radio resources at call setup and during the active mode to LSA users. Allocation of resources could be achieved by defining a specific load alarm for PA cells in-the BSC. Upon triggering the alarm threshold, access to PA cells would be granted only to LSA subscribers. In call setup phase and in handovers, PA can be supported by using the LSA information delivered to BSC (see section Localised service area support in active mode). For Camel Service Environment (CSE), the following functionality is required from a SoLSA server: (1) storage and management of subscriber specific LSA information, (2) interface to service provision and management system, (3) LSA information transfer to the MS, (4) conformance with SIM Application Toolkit (class 1) data down load procedure, and (5) LSA information transfer to the MSC.
Using CAMEL platform provides a number of benefits. CAMEL Application Part (CAP) protocol is able to transfer the cell id to the CSE for LSA information processing during call setup. That would make it easy for any CAMEL application (e.g. tariff applications) to use SoLSA capability. CAMEL platform would also enable SoLSA based services to roaming subscribers.
To support SoLSA, the MS and the SIM must support SIM Application Toolkit (class 1). The MS must also have: support a subscriber-specific LSA indication; LSA support in idle mode (decoding and processing of new SoLSA specific system information parameters and LSA specific cell reselection algorithm); LSA support for EA in Idle state (ignore Cell_Bar_Access bit while in LSA and support decoding and processing of LSACell_Bar_Access bit while in LSA); and LSA support for LSA only access in Idle state (indication to subscriber when not in an LO cell).
The BSC must support: LSA in active mode (reception and proccessing of LSA information during call setup, storage and execution of an LSA favouring algorithm, and transfer of LSA information between BSCs during external handovers); EA; LO; and PA.
A problem associated with the above-mentioned embodiment for providing special services in a network is that SoLSA is only defined for circuit-switched connections, i.e. GSM and its derivatives. In a dual mode GSM/GPRS network, the coverage of GSM and GPRS services may be different. Thus the prior art SoLSA provides little or no support for packet-switched connections, e.g. GPRS. A specific problem with the prior art GSM SoLSA is encountered when a dual-mode mobile station with SoLSA active is involved in a GPRS connection. In such a situation, SoLSA support is discontinued because GPRS cell reselection does not take SoLSA into account.
A straightforward solution would be to mirror the GSM SoLSA to the GPRS service. However, such a straightforward solution would involve several interworking problems which do not exist at all if SoLSA is implemented for GSM only. For example, in GSM-only SoLSA, the MS is in SoLSA state if the network supports it. Obviously, a dual-mode MS should be in SoLSA state if both networks (GSM and GPRS) support it. However, difficult decisions are encountered if only one network supports SoLSA, or if the MS can barely receive a BTS supporting GPRS SoLSA but it receives well a BTS supporting GSM SoLSA.
An object of this invention is to develop methods and network elements for overcoming the above problems. The object is achieved by means of methods and transceivers which are characterized by what is disclosed in the characterizing part of the appended independent claims. Preferred embodiments of the invention are specified in the dependent claims.
In the following, xe2x80x98transceiverxe2x80x99 refers commonly to a mobile station MS or that part of a land-based mobile network (BTS/BSC or RNC) which is serving that MS. xe2x80x98Dual-modexe2x80x99 refers to a transceiver supporting both circuit-switched and packet-switched connections. GSM and GPRS will be used as well-known examples of circuit-switched and packet-switched connections respectively, but the invention is not limited to these two embodiments. The invention is based on the idea that a dual-mode transceiver can be modelled as a state diagram, as shown in FIG. 5. The state diagram has four states, as follows: State S1 is GSM Idle (non-SoLSA) state, state S2 is GSM SoLSA, State S3 is GPRS Ready or Standby state and state S4 is GPRS SoLSA. FIG. 5 also shows the corresponding transitions T12, T13, . . . T34 between the states S1 to S4.
State transitions T12 and T34 correspond to a positive finding of SoLSA. The reverse transitions T21 and T43 correspond to negative finding of SoLSA. The State transitions T13 and T24 relate to the GPRS attach procedure and state transitions T13, and T24 relate to the GPRS detach procedure.
In retrospect, constructing the state diagram of FIG. 5 may seem rather straightforward, considering that states S1 to S3 exist in prior art system. However, a corresponding prior art state diagram would be trivial as state S4 and half of the state transitions are omitted, i.e. all transitions to/from state S4. Thus, it can be said that the invention is also based on developing well-determined criteria and/or priorities for these state transitions.
Preferably, the criteria for the state transitions are based on the fact that of the two communications modes, i.e. circuit-switched and packet-switched, one has better coverage. In a combined GSM/GPRS system, GSM typically has better coverage than GPRS. Thus, in situations where there is a possible conflict between a state transition based on GSM criteria and a state transition based on GPRS criteria, it is advantageous to use the GPRS criteria to determine whether the mobile station is in SoLSA mode or not. Such a conflict may occur when the mobile station has an activated GPRS context (in Standby or Active state). In such a situation, the mobile station would not perform state transition T12 unless T34 is also possible.
The methods and network elements according to the invention extend the concept of SoLSA to packet radio network by solving the interworking problems of prior art systems.

Cell selection in a packet radio network


This invention relates to the composition and method of treating arthritis, repairing of articular joint surfaces and the relief of symptoms associated with arthritis. The composition comprises a nitric oxide synthase inhibitor and amino sugars. The nitric oxide synthase inhibitor reduces the level of nitric oxide, the free radical believed responsible for the degradation of articular cartilage. Amino sugars are the building blocks of articular cartilage and have anti-inflammatory actions.

The present invention concerns compositions and methods of treating arthritis, repairing of articular joint surfaces and relief of symptoms associated with arthritis.
Arthritis, a musculoskeletal disorder, is the leading cause of disability in the United States. The Centers for Disease Control and Prevention (CDC) stated that arthritis and other rheumatic conditions accounted for about 744,000 hospitalizations and 4 million days of care in 1997. Forty million Americans, representing 15% of the population, have some form of arthritis, and that figure is expected to increase to 59.4 million (18.2%) by the year 2020, an increase of 57% in the number of persons affected. Arthritis patients make more than 315 million physician visits and are hospitalized more than 8 million times a year. Arthritis costs the nation $65 billion annually in medical costs and lost productivity. Osteoarthritis (OA), or degenerative joint disease, is the most common type of arthritis, affected 20.7 million people (12.1% ) of U.S. adults in 1990, now estimated at 37 million, and trailed chronic heart disease as the leading cause of Social Security payments due to long-term absence from work. Lawrence R C, et al. Arthritis and Rheumatism 1998;41:778-799.
Osteoarthritis usually presents as pain, which worsens with exercise or simply an X-ray that clearly shows thinning cartilage. Common joints affected are the knees, hips and spine, finger, base of thumb and base of the big toe. Osteoarthritis is characterized by degenerative changes in the articular cartilage and subsequent new bone formation at the articular margins. The primary defect in hyaline cartilage, at the articular surface of the joint, is an alteration in the ratio of total glycosaminoglycans to that of the collagen fiber content in the matrix. Yasuda K. Hokkaido Igaku Zasshi 1997 Jul;72(4):369-76. Paleontologists have found osteoarthritis to exist in almost every vertebrate. Joint cartilage consists of only 5 percent cells, and joint cartilage lesions do heal Tindall W N. Business and Health Dec 1997;47-48. Bones directly underneath the cartilage in joints is called subchondral bone. This bone nourishes the cartilage with oxygen, water, and nutrients conveyed through microscopic channels. This supply route carries xe2x80x9cchondroprotective agentsxe2x80x9d from the bloodstream to the cartilage.
Cartilage is the supporting structure of the body, but has no blood vessels, nerves or lymphatics, and consists of thick bundles of fibrous protein (collagen) which are woven to form the articular surface. Proteoglycans fill the extracellular spaces not occupied by collagen, and are a combination of protein and sugar. Each proteoglycan subunit contains a protein core attached to hundreds of long chains of specially modified sugars called glycosaminoglycans (GAGS). Glucosamine is the single most important component and precursor for GAGs. Glucosamine is almost completely absorbed by the GI tract into the bloodstream. Cartilage rebuilding is only as good as its GAG synthesis. Chondrocytes in the cartilage obtain glucosamine from the subchondral blood vessels and manufacture N-acetylglucosamine (NAG) and glucuronic acid, which make hyaluronan, which is half glucosamine, and provides the lubricating ability of joints.
There is no definitive answer regarding the cause of osteoarthritis. A natural erosion of cartilage occurs with age, but excessive loads placed on joints, obesity, heredity, trauma, decreased circulation, poor bone alignment, and repetitive stress motion play a role. Osteoarthritis may also be the result of free radical damage, thought to be a major cause of many diseases, including the aging process, cancer, heart disease and degenerative diseases.
Free radicals affect the immune system causing rheumatoid arthritis and osteoarthritis. Free radicals are atoms or atomic groups that are byproducts of normal metabolism, tobacco smoke, pollutants, car exhaust, bacteria, radiation, and chemicals which oxidize or damage otherwise healthy cells. They damage DNA, corrode cell membranes, and may play a role in the development of cancer, heart and lung disease, cataracts, and cause or accelerate the aging process. Bucci wrote that there is conclusive evidence that free radicals do most of their damage in rheumatoid arthritis, but also to the cartilage in osteoarthritis. Bucci L. Healing Arthritis the Natural Way Arlington, Tex.: Summit Publishing Group, 1995, pp. 34-5. In his best seller, Theodosakis stated that xe2x80x9cOsteoarthritis may be the result of free radical damage. And to make matters worse, joint inflammation itself may trigger an even faster rate of new free radical formation. Prevention of free radical damage is a critical feature in treating and preventing osteoarthritis.xe2x80x9d Theodosakis J, Adderly B, Fox B. The Arthritis Cure New York, St. Martin""s Press, 1997, p 147-9. Unless the damage caused by free radical formation is addressed, any benefits obtained by using only chondroprotective agents could be nullified; similar to trying to fill a sieve with water, the relief is transient but pathology progresses.
There is no known drug that claims to reverse osteoarthritis. Most therapeutic agents are directed at reducing the inflammation and relieving pain. Non-steroidal anti-inflammatory drugs (NSAIDs) are the first line of treatment for osteoarthritis, but long-term use can lead to gastric ulcers, kidney damage, hearing loss and even inhibit cartilage formation.
This invention relates to the composition and method of treating arthritis, repairing of articular joint surfaces and the relief of symptoms associated with arthritis. The nitric oxide synthase inhibitor reduces the level of nitric oxide, the free radical responsible for the degradation of articular cartilage. Amino sugars are the building blocks of articular cartilage and have anti-inflammatory actions.
Osteoarthritis is thought to be the result of decreased production and increased degradation of the cartilaginous matrix. Loss of this protective layer leads to roughening and fissuring of the cartilage and may eventually cause erosion severe enough to expose the bone. The current goal of osteoarthritis therapy is the relief of pain. NSAID use is limited by the fact that they do not change the natural course of the disease and may accelerate joint deterioration in the long run.
The maintenance of articular cartilage requires a balance between anabolic and catabolic processes. An increase in some cytokines, such as interleukin-1 (IL-1), is associated with a decrease in the synthesis and increase in the degradation of proteoglycans and collagens necessary for the structural integrity of the cartilaginous matrix. While cytokines, such as transforming growth factor xcex2(TGF xcex2), stimulates chondrocyte synthesis of collagens and proteoglycans, reduces the activity of IL-1-stimulated proteinases, and opposes the inhibitory and catabolic effects of IL-1.
Patients presenting with either rheumatoid arthritis (RA) or osteoarthritis (OA) have been observed to have increased levels of NO in the synovial fluid. A significant source of NO production in these patients appeared to be articular chondrocytes. Henrotin YE, et al, Nitric oxide downregulates cytokines, J of Rheumatology 1998;25(8):1595-1601. Nitric oxide (NO) is produced by articular chondrocytes in large amounts for extended periods of time by an inducible form of nitric oxide synthase (NOS) in response to activation by IL-1 and other agents. An increase in NO decreases the synthesis of proteoglycans and type II collagen. If NO production is blocked with the use of NG-monomethyl-L-arginine (L-NMA), an inhibitor of NOS, inhibition of proteoglycan synthesis by IL-1xcex2 is blocked, and concentration of TGF xcex2 is increased. Studer R K, Georgescu H I, Miller L A, Evans C H, Inhibition of transforming growth factor xcex2 production by nitric oxide-treated chondrocytes, Arthritis and Rheumatism 1999;42(2):248-257.
Nitric oxide is a short lived, gaseous free radical that is synthesized from the terminal guanidino nitrogen of L-arginine in an oxidation reaction catalyzed by NOS. NOS expression is inducible by endotoxin, cytokines, growth factor and immune complexes. The overexpression of NOS in rheumatoid arthritis (RA) may result from increased levels of tumor necrosis factor-xcex1 (TNF-xcex1), IL-1xcex2, and other proinflammatory cytokines characteristic of this disease. Chondrocytes from patients with OA and RA spontaneously over express NOS and produce elevated levels of NO. St. Clair E W, Nitric oxidexe2x80x94friend or foe in arthritis? J of Rheumatology 1998;25(8):1451-1453.
Canadian researchers reduced the progression of experimental osteoarthritis in dogs by inhibiting inducible nitric oxide synthase (NOS). Pelletier J P, et al. Arthritis and Rheumatism 1998;41:1275-1286. Pelletier reported that osteoarthritis cartilage produced an increased amount of nitric oxide (NO) due to an increased level of inducible nitric oxide synthase in cartilage chondrocytes. Nitric oxide plays an important role in autoimmunity and inflammation. Normal cartilage does not produce NO or express NOS unless stimulated with cytokines. In the joint, NO, produced in response to cytokine stimulation, exerts a number of catabolic effects on chondrocyte functions which would be expected to promote the degradation of articular cartilage. These effects of NO on chondrocytes include: inhibition of collagen and proteoglycan synthesis, activation of metalloproteinases, increased susceptibility to injury by other oxidants, inhibition of actin polymerization, and apoptosis. NSAIDs, such as aspirin, and to a lesser extent, sodium salicylate, and tetracycline inhibit the expression of NOS protein. Clancy R M, Amin A R, Abramson S B. Arthritis and Rheumatism 1998;41:1141-1151.
Nitric oxide synthase inhibitors which may be employed include, but are not limited to: arginine-based analogues such as methylated arginines, substituted L-arginine, nitro-arginine, L-NG-nitroarginine, NG-mono-methyl-L-arginine (NMA), N-nitro-L-arginine methyl ester, N-amino-L-arginine, N-methyl-L-arginine, NG-monomethyl-L-arginine (L-NMA), L-NG-mono-methyl-arginine (L-NMMA); flavoprotein binders such as diphenylene iodonium and related iodonium derivatives, ornithine and ornithine derivatives such as N-imino-ethyl-L-ornithine; tetracycline; L-canavanine; citrulline; redox dyes such as methylene blue; calmodulin binders such as trifluoropiperazine and calcinarin; heme binders; zinc compounds; tetrahydropterin analogs such as aminoguanidine; and depleters of biopterin such as methotrexate.
The use of NOS inhibitors is well known in the art. Dawson et al, U.S. Pat. No. 5,266,594, discloses a method of preventing or treating glutamate neurotoxicity with a NOS inhibitor capable of penetrating the blood brain barrier. Ahluwalia et al, U.S. Pat. No. 5,468,476, discloses a method of reducing hair growth with a NOS inhibitor. Wahl et al, U.S. Pat. No. 5,449,688, discloses a method for treating chronic inflammatory conditions by parenterally or intravenously administering a NOS inhibitor. Stamler et al, U.S. Pat. No. 5,545,614, discloses a method for stimulating skeletal muscle contractions with a NOS inhibitor. Moncada et al, U.S. Pat. No. 5,585,402, discloses a method for inhibiting tissue damage by using a NOS inhibitor to decrease NO production in vascular endothelial cells. Dunn et al, U.S. Pat. No. 5,665,757, discloses a method for treating anxiety using a NOS inhibitor. Mjalli et al, U.S. Pat. No. 5,723,451, discloses a method for inhibiting NOS using one of eleven formulations. None of the above cited patents teach or suggest the use of the composition and method outlined in the present invention.
Agents that may repair, or at the very least, slow the degradation of articular cartilage have been described as possessing chondroprotective properties. Examples of these agents include: heparinoids (Arteparon, Rumalon), hyaluronic acid, piroxicam, tetracyclines, corticosteroids, chondroitin, and glucosamine sulfate. Da Camara C C, Dowless G V. Annals of Pharmacotherapy 1998;32:580-7.
Glucosamine from exogenous sources (food and supplements) may stop the progression of cartilage degradation and stimulate the production of new cartilage. Glucosamine absorbed by the gastrointestinal tract undergoes significant first-pass metabolism in the liver, with the resulting 26% bioavailibility. It is incorporated into plasma proteins as a result of hepatic metabolism, and concentrates in the articular cartilage. Clinical improvement of symptoms has been seen as early as one week after oral administration of glucosamine sulfate and has persisted for up to four weeks after discontinuation. Barclay T S, Tsourounis C, McCart G M. Glucosamine. Annals of Pharmacotherapy 1998;32:574-79.
Several commercial forms of glucosamine are available, including the sulfate, hydrochloride, and N-acetylglucosamine (NAG). Glucosamine hydrochloride has a higher concentration of glucosamine than the sulfate form. NAG is rapidly metabolized to make proteins and provides less glucosamine for cartilage repair. The composition of the invention could include one or a combination of the glucosamine forms. Patients have reported a more rapid response with higher dosages of glucosarine, but the therapeutic results with glucosamine alone have not been consistent. The dosage range for glucosamine can vary from 500 mg to 3000 mg a day, in divided doses, depending on body weight and severity of symptoms. One approach is to take 1,500 mg of glucosamine daily until symptoms have decreased, then reduce the dosage to 1,000 mg for two weeks and eventually stop treatment after symptoms cease or stay on a maintenance dose of 500 mg per day.
Adverse effects reported from glucosamine are gastrointestinal, such as heartburn and epigastric pain. Because the half-life of glucosamine in the blood is relatively short, a sustained-release form of the compound could avoid the adverse effects and provide a more uniform blood level. Talent J M, Gracy R W. Clinical Therapy 1996; 18(6):1184-90.
The use of amino sugars is well known in the art. Jacobi, U.S. Pat. No. 3,859,436, discloses a topical composition of glucose, fructose, glucosamine and desoxyribose and ribose. Prudden, U.S. Pat. No. 4,006,224, discloses a method for treating inflammatory disorders of the gastrointestinal tract with D-glucosamine. Meisner, U.S. Pat. No. 4,590,067, discloses a composition for the prevention and treatment of periodontal disease comprising, bone meal, tyrosine, glucosamine and ascorbic acid. Speck, U.S. Pat. No. 4,870,061, discloses a method for treating degenerative joint disease by buccal administration of N-acetylglucosamine. Kludas, U.S. Pat. No. 5,036,056, discloses a method for treating damaged connective tissue with a connective tissue matrix of collagens, proteoglycans, glycosaminoglycans and glycoproteins. Henderson, U.S. Pat. Nos. 5,364,845 and 5,587,363, discloses a composition for the repair of connective tissue comprising glucosamine, chondroitin sulfate and manganese. Williams et al, U.S. Pat. No. 5,679,344, discloses a composition for articular disorders comprising glucosamine and proteases. Diaz et al, U.S. Pat. Nos. 5,795,576 and 5,891,441, discloses a composition and method for the elimination of undigested fat prior to digestion comprising, psyllium, glucosamine, glucomannan, apple pectin and stearic acid. Murad, U.S. Pat. No. 5,804,594, discloses an oral composition for improving skin conditions comprising, N-acetylglucosamine, ascorbic acid, amino acids, and a transition methal composition. Florio, U.S. Pat. No. 5,840,715, discloses a composition of nutritional supplements of gamma linolenic acid, eicosapentaenoic acid and docosahexaneoic acid, chondroitin sulfate, N-acetylglucosamine sulfate, glucosamine sulfate and manganese aspartate. Platt, U.S. Pat. No. 5,891,861, discloses a composition of oligomers of beta glucosamine to treat fungal diseases. Weisman, U.S. Pat. No. 5,888,514, discloses a composition of natural ingredients for treating bone and joint inflammation using shark cartilage, glucosamine, herbs and enzymes. None of the above cited patents teach or suggest the composition or method outlined in the present invention.
Chondroitin sulfate is the major GAG in cartilage, and has a synergistic effect with glucosamine, but poorly absorbed by oral administration. Chondroitin sulfate is half galactosamine, which is made directly from glucosamine, and has great water retaining ability. Dosage range of chondroitin sulfate is 250 mg to 1,000 mg per day in divided doses. Morrison, U.S. Pat. No 3,895,107, discloses a method of inhibiting atherosclerotic lesions by administering chondroitin sulfate. Walton et al, U.S. Pat. No. 4,489,065, discloses the binding of drugs to chondroitin for the controlled release of the drug. None of the above cited patents teach or suggest the use of the composition and method outlined in the present invention.
Zinc plays a physiological role in the regulation of bone metabolism, by stimulating bone formation and mineralization and an inhibitory effect on bone resorption. Zinc activates aminoacyl-tRNA synthetase in osteoblastic cells, stimulates cellular protein synthesis, and inhibits osteoclast-like cell formation in marrow cells. Bone zinc content is decreased by development, with aging, skeletal unloading, and postmenopausal conditions. Zinc plays a role in the preservation of bone mass. Most zinc compounds, such as zinc sulfate, are useful for the prevention of osteoporosis, but a recent study confirmed that xcex2-Alanyl-L-histidinato zinc (AHZ) has a potent effect on bone formation and calcification. Yamaguchi M, Role of Zinc in Bone Formation and Bone Resporption, J. of Trace Elements and Experimental Medicine 1998; 11:119-135.
Zinc compounds have anti-inflammatory and anti-infective properties. In a recent published article, Petrus E J et al., Current Therapeutic Research, 1998; 59/9: 595-607, the inventor served as chief investigator for a randomized, double-masked, placebo-controlled clinical study of the effectiveness of zinc acetate lozenges on common cold symptoms in allergy-tested subjects. Those subjects who used the zinc lozenges had both a shorter duration and severity of common cold symptoms. Those subjects who were positive for allergies, were more responsive to zinc by having a shorter duration of nasal symptoms. The study cited many references that reported the benefits and effects of zinc compounds.
Zinc is an essential mineral found in every form of life on earth. Unlike other metals, zinc is virtually nontoxic. Zinc and its compounds have long been recognized as possessing certain therapeutic functions. Zinc compounds are acknowledged as astringents and beneficial in wound healing, reducing inflammation, and has antimicrobial, antifungal and antiviral activity. Zinc is the active agent in formulations to treat diaper rash, decubitus ulcers, and abrasions. Zinc stabilizes the cell membranes and inhibits the formation of free radicals. Zinc also strengthens the integrity of blood vessel walls by reducing the membrane permeability and stopping bleeding.
Zinc has an inhibitory effect on the release of histamine from mast cells due to its stabilizing effect of the mast cell membrane. Mast cells isolated from specimens of atherosclerotic plaques contained matrix metalloproteinase type 9, one of the enzymes that can produce collagen degradation. Kovanen Pt, et al. J. Am College of Cardiology 1998;32:606-612. The inhibitory effect of zinc on allergy and immunology make it an excellent enhancement to glucosamine and chondroitin therapy. Zinc is also a very potent inhibitor of nitric oxide synthase (NOS). Cuajungco M P, Lees G J Neurobiol Disease 1997;4(3-4):137-69.
In a preferred form of the invention, the composition uses a zinc salt such as zinc acetate, with the dosage range of 30 to 60 mg per day in divided doses. Zinc salts are selected from a group consisting of, but not limited to: zinc sulfate, zinc chloride, zinc acetate, zinc phenol sulfonate, zinc borate, zinc bromide, zinc nitrate, zinc glycerophosphate, zinc benzoate, zinc carbonate, zinc citrate, zinc hexafluorosilicate, zinc diacetate trihydrate, zinc oxide, zinc peroxide, zinc salicylate, zinc silicate, zinc stannate, zinc tannate, zinc titanate, zinc tetrafluoroborate, zinc gluconate, and zinc glycinate.
Zinc acetate is absorbed throughout the small intestine and has an excellent safety profile. It does not adversely alter serum albumin, bilirubin, aminotransferases, hematologic variables, iron metabolism or renal function indices. Zinc acetate has been assigned to FDA pregnancy category A, indicating that the possibility of fetal abnormalities appears remote. In several trials, no toxic adverse effects have been reported in any patient. The most common adverse effect of zinc therapy is gastrointestinal irritation, which is reported to occur in approximately 10% of patients. Anderson L A, Hakojarvi A L, Boudreaux S K. Annals of Pharmacotherapy 1998;32:78-87. A controlled-release formulation could reduce GI irritation and enhance absorption.
Although any suitable route of administration may be employed for providing the subject with an effective dosage of the composition according to the methods of the present invention, oral administration is preferred. Suitable routes include, for example, oral, rectal, parenteral, intravenous, topical, transdermal, subcutaneous, intramuscular, and like forms of administration may be employed. Suitable dosage forms include tablets, troches, dispersions, suspensions, solutions, capsules, patches, suppositories, creams, ointments, gels, and the like, although oral dosage forms are preferred. A topical composition, with a permeation enhancing amount of at least one penetration enhancer, in an appropriate pharmaceutical carrier, could be in the form of a gel, ointment, cream, solution or other means.
The use of pharmaceutical controlled release methods to deliver the composition to the gastrointestinal tract with a desired level of nitric oxide synthase inhibitors, amino sugars and other agents without the adverse gastrointestinal effects is well known in the art.
Enteric coatings are pH sensitive polymers designed to remain intact in the acidic environment of the stomach, but to dissolve in the more alkaline environment of the intestine. Some enteric coatings use blends of cellulose acetate phthalate polymers. Wu et al, U.S. Pat. No. 5,356,634 discloses an enteric coating composition of cellulose acetate phthalate (CAP) and cellulose acetate trimellitate polymers. Crook et al, U.S. Pat. No. 5,723,151 discloses a composition of cellulose acetate phthalate polymer and organic solvent. Some enteric coatings use polyvinylpyrrolidone (PVP). Sipos, U.S. Pat. No. 4,079,125 discloses a binder and stabilizer of PVP and a coating of CAP and diethyl phthalate. Patell, U.S. Pat. No. 4,775,536 discloses the use of an enteric polymer of an acrylic resin and an undercoat and overcoat of PVP. Hodges et al, U.S. Pat No. 5,225,202 discloses an enteric coated composition of hydroxypropylmethyl cellulose phthalate, a plasticizer of triethyl citrate and talc as an anti-adherent.
Some polymers commonly used for enteric coatings are cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose phthalate (HPMCP), cellulose acetate trimellitate (CAT), hydroxypropyl methylcellulose acetate succinate (HPMCAS), polyvinyl acetate phthalate (PVAP) and acrylic resins. One formulation of the present invention uses 7 mg of polyvinylpirrolidone to coat the immunostimulant composition. The composition can be in the form of a tablet, capsule, granules, or pill for oral administration. Disintegration of the PVP enteric coating occurs in approximately 40 minutes, about the time the composition is in the intestine.
In addition to nitric oxide synthase inhibitors and amino sugars, the following active agents may supplement the composition to promote the development and maintenance of cartilage, include but are not limited to: vitamins, A, B, C, E; minerals, selenium, silica, manganese, magnesium, copper and boron; glycosaminoglycans; analgesics, anti-inflammatory agents, methyl-sulfonyl-methane, Sadenosyl-methionine, alpha-lipoic acid, aloe vera extract, preservatives, antioxidants, stabilizers, surfactants, anti-infective agents, adjuvants, anthocyanidins, proanthocyanidins, and herbal derivatives.
In a further aspect of this invention, for those who have difficulty swallowing a large tablet, due to esophageal strictures or other pathology, a therapeutically effective solution can be administered by a suspension of the active agents in a pharmaceutically acceptable carrier to provide a liquid form to be swallowed or sprayed onto the oral mucosa. By a xe2x80x9cpharmaceutically acceptable carrierxe2x80x9d is meant a composition, solvent, dispersion medium, coating, delivery vehicle or the like, which can be employed to administer the compositions of the present invention without undue adverse physiological effects.
Although illustrative embodiments of the invention have been shown and described, a wide range of modifications, change, and substitution is contemplated in the foregoing disclosure and in some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention. The above-mentioned patents are hereby incorporated by reference.

Method and composition for treating arthritis


A clamp on ultrasonic transducer having a clamping element which can be positioned around a conduit with the inner portion of the clamping element being formed to fit closely against the outer wall of the conduit, thus defining at a selected position along the conduit a transverse reference plane. The clamping element carries on it one or more channels extending parallel to the axis of the conduit with ultrasonic transducing elements adjustably mounted on those channels such that their contact pressure with the conduit can be independently adjusted. The ultrasonic transducing elements then form a path of ultrasonic interrogation in a plane parallel to the axis of the conduit and at a position defined by the transverse reference plane.

This invention relates in general to ultrasonic measuring equipment and more particularly to a removable-clamp-on ultrasonic transducer for use in measuring fluid characteristics within a conduit. Ultrasonic measurement of the flow of a fluid within a conduit may utilize a variety of methods: contrapropagating transmission (upstream-downstream), reflection or Doppler, interaction with shed vortices, correlation, noise, etc. Many applications require that the transducers be coupled to the exterior of the conduit, without penetrating the wall.
In some cases, for example Doppler methods, only one transducer need be coupled to the pipe. In other cases two or more transducers may need to be coupled to the pipe. The transducers may need to be coupled on opposite sides, on the same side, or, for measurement of swirl, along the pipe at the ends of paths which may be rotated from one another.
Prior art transducer clamps generally consist of some sort of strapping arrangement attached directly to the transducer wedges. For example, hose clamps have been used, encircling both the pipe and the transducer wedge. Equivalently, turnbuckle and cable arrangements have been used. In either case, as the clamping means is tightened, the transducer's position varies, due to motion of the clamp. Prior art clamps do not provide for precise repositioning of the transducer.
Clamp-on ultrasonic transducers are known in the art. In one type of measurement problem it is desired to survey fluid conditions (particularly flow velocity) within different pipes at different locations about a plant using only one measurement device. In other applications the transducers may be considered dedicated to a particular site and will be bonded to the pipe with RTV rubber or epoxy. In the former case it is important that when the transducers are brought back to a particular site, they must be repositioned in the same location, or readings are unlikely to be repeatable despite the same flow velocity. Not only should the location and spacing of the transducers be repeatable, even the coupling conditions, e.g., pressure, should be repeatable, so as to not distort the pipe by different amounts on different occasions. One of these locations may be on a calibration flow loop. In the dedicated case, during the time that the couplant is curing, it is important that the transducers do not move. Furthermore, if dedicated transducers are being applied to two or more pipes whose contents are to be mixed in a controlled manner, e.g. pigments for a paint mixture, then it becomes important that installations on the several pipes are effected in a precise manner.
One problem associated with prior art transducers lies in the adjustment of the pressure between the transducer and the pipe or conduit. In general in the art the same adjustment elements that control the degree of tightness with which the clamp is fastened to the conduit, also controls the contact pressure of the transducing element. Too much pressure damages the element; too little and the clamp may slip either longitudinally or radially.


A filter element comprising at least one elastomeric end-cap, a thin-walled pleated filter medium having edges thereon constructed and arranged for positioning proximate to the elastomeric end-caps, and a polymeric adhesive material within the end-caps for sealing the edges of the filter media therein, and a method for producing the same.

1. Field of the Invention
The present invention generally relates to an improved end-cap for pleated filter cartridges and a method of manufacturing such end-capped pleated filter cartridge. More particularly, the present invention relates to a pleated surface-type filter cartridge having an elastomeric end-cap which acts both as the end-cap for sealing the filter element and a gasket for providing a seal between the filter housing and the filter cartridge. The elastomeric end-cap of such pleated surface-type filter cartridge is bound to the filter element by means of a thermoset or thermoplastic adhesive.
2. Background of the Related Art
Filtration is the process of separating particles from a fluid suspension (liquid or gas) by use of a porous medium or by means of a medium possessing chemical properties, such as hydrophobicity, electrostatic charge, etc., which permit such medium to interact and hold the particles which are to be separated from the fluid while permitting the fluid to pass there through. In conventional filtration, the filter medium retains most of the suspended particles which are filtered on or within itself, but allows the fluid being filtered to pass through unimpeded. Flow across the filter medium is generally achieved by the application of a driving force, usually in the form of a static pressure difference across the filter, which may be generated, for example by external pressure applied upstream, a vacuum applied downstream, gravity, or other force. Fluid suspension separations are used extensively in the manufacture of polymer products, medicinals, mineral and metallurgical processing, petroleum refining, water purification, emissions control, and in beverage and food preparation.
Most conventional filters may be categorized into two broad categories of filters, surface-type filters and depth-type filters. In surface-type filters, particles larger than the pore size of the filter medium are stopped at the upstream surface of the filter. Solids form a filter cake on the surface of the filter medium, the cake itself forming a filter which clogs with time. In depth filtration, on the other hand, the filters are constructed of medium of sufficient thickness, relative to contaminant size, to filter throughout the full depth. Typically the filter medium has a distribution of pore sizes some greater than the particles to be removed, so that the particles can penetrate into the medium. The particles are mainly retained in the medium by means of direct interceptions and by adsorptive surface forces (molecular and electrostatic).
Filters are often fabricated into cartridges comprising filter media surrounding a tubular support and/or drainage core. Depth-type filtration cartridges are frequently fabricated from wound material, felts, some porous ceramics, sintered metal or metal fibers and bonded fibers. Surface-type filtration cartridges are frequently fabricated of fiber sheets. Surface-type filter cartridges may be resin impregnated paper, may be membranous, may comprise porous metal, plastic, or non-woven material and may be covered with a netting or cage to increase strength.
Generally as a fluid suspension is passed across filter media the pressure drop across the filter gradually increases. Such increase is generally due to collection of material on the filter media. An increasing pressure drop across the filter media translates into an increasing load on the means (such as a blower or pump) being employed to force the fluid across the filter media. A surface filter, therefore, must have a large enough area of filter media to minimize the rate of increase in pressure drop across the filter media.
In order to increase the surface area in a surface-type filter cartridge, pleated filter media have been developed. Pleated surface-type filters typically include cellulosic or synthetic filter media which are relatively thin (about 0.005 inch to about 0.030 inch in thickness) and are folded in an accordion-like fashion to produce a plurality of pleats. Each pleat is typically made up of a pair of rectangular panels, with fold lines separating the panels, the pleats and fold lines of the pleated filter usually running vertically. To help insure that the surface of the panels remain apart, and to provide even more surface area, the pleated surface-type filter may also be formed from corrugated material and/or have a substantially non-filtering material located on each side of the medium to act as a support and drainage layer. Typically, pleated surface-type filter media are formed from calendered melt-blown material, cellulose and/or paper.
A pleated surface-type filter cartridge, as many other filter cartridges, typically includes a pair of end-caps. The end-caps of a pleated surface-type filter cartridge span the filter media, with the pleats and fold lines normally running from one end-cap to the other end-cap. If corrugations are present, such corrugations generally run at right angles to the pleat tips, that is, parallel to the end-caps. The end-caps serve to prevent the fluid which is desired to be filtered, from circumventing passage through the filter media by, in the case of pleated surface-type filter cartridges, coursing along the fold lines of the pleats and directly exiting through the ends of the cartridge. The end-caps may be solid throughout, or may include an opening therein. Filter cartridges having one solid end-cap and an end-cap having an opening therein are referred to in the art as single open end filter cartridges, while filter cartridges having two end-caps with an opening therein are referred to as double open end cartridges. Pleated surface-type filter cartridge end-caps are typically made form metal (steel, stainless steel etc.), but also have been fabricated from non-elastomeric thermoplastic (such as polypropylene, polyester and polysulfone) and thermoset (such as plastisol, urethane, silicone, epoxy) material.
Various methods have been proposed for attaching an end-cap to a filter cartridge. In general, these methods may be classified into four major categories: potting, molding, thermal-welding and spin-welding.
Potting entails pre-forming the end-cap, filling the end-cap with an adhesive and inserting the filter element therein. Potting may also be performed by placing the adhesive on the surface of the filter element and pressing the filter element against the end-cap until the joint is set (this technique is also referred to as xe2x80x9cbondingxe2x80x9d). The adhesive is cured using a combination of heat and/or time.
In molding, the end-cap is molded directly onto the end of a filter element. The molding material is typically a thermoset polymer, such as plastisol, urethane, silicone and epoxy. The molded end-cap is then removed from the mold.
In thermal welding, a thermoplastic end-cap is heated to liquefy one surface of the end-cap and form molten plastic. One end of the filter element is then placed into the liquefied surface of the end-cap. When the end-cap solidifies once more, the filter element is securely joined to the end-cap.
In spin-welding, the end-cap and filter element are joined and placed in frictional contact with one another. Either the end-cap or filter element are then rotated with respect to the other so that heat is generated by frictional contact. The heat melts the surface of one or both to form a molten material at the interface of the two. When the rotation is stopped, the molten material solidifies to securely bond the end-cap to the filter element. Typically, one of the two members to be joined by spin welding is made of a thermoplastic resin. Spin-welding and thermal welding techniques are often referred to jointly as xe2x80x9cheat bonding.xe2x80x9d
Application of end-caps to pleated surface-type filter elements are associated with problems not generally seen with other types of filter elements, such as depth-type filter elements. Pleated surface-type filter elements suffer from an inherent lack of structural rigidity as compared to many other types of filter elements, and in particular suffer from a tendency of the pleats to collapse and deform. Pleated surface-type filter elements are also more prone to leakage at the end-cap-filter element interface than more solid and integral filters such as fibrous depth filters. End-cap voids have also been associated with the potting, thermal welding and spin welding of end-caps to pleated surface-type filter elements. The latter may be due to non-uniform penetration of the potting or melted material by the pleated material and non-uniform spacing between pleats (some pleats being deformed to narrow the gap between them, others being more open) in particular when repositioning or withdrawal of the pleated filter element occurs.
Presently utilized end-cap constructions for pleated surface-type filters suffer from a number of drawbacks that limit the range of their possible applications and/or require less than desirable manufacturing expenditures to overcome such drawbacks.
Thermal and spin-welded end-caps of the prior art require the utilization of a separate gasket in order to seal the cartridge against the filter housing. A separate gasket in cartridge fabrication entails additional manufacturing expenses and the expenditure of labor. Further, as conventionally applied, such gaskets suffer from the tendency to fall off in transport, handling and installation into the filter housingxe2x80x94which can lead to the loss of seal integrity and bypass. Application of an adhesive to hold the gasket in place or heat-staking the gasket to the filter, is not commercially desirable as it adds another expensive manufacturing step. Chemical incompatibility problems and contamination from undesirable extractions may also adversely occur. Introduction of a mechanical interference fit, beside adding expense, requires that the parts be designed and produced with tight tolerances which is costly, and may be impractical. Application of end-caps to pleated filters which are melted on one surface by heat bonding techniques further suffers from the disadvantage that the pleats are prone to be deformed by the process, and air bubbles may be introduced as the pleat is seated in the molten material. Thus the ability to achieve a repeated integral seal on the filter cartridge is significantly adversely affected by use of such techniques to bond end-caps to the pleated filter elements. Incorporation of stainless steel and other metallic cores, which may be a component of the filter structure, is also made more difficult by use of such techniques, presumably because the melt depth is shallow and the adhesion is not strong enough to prevent the core from being pulled out of the cap.
End-caps of the prior art which are formed by molding, while in some cases not requiring a separate gasket component, suffer from the inherent composition and structure of the end-caps. Currently available end-caps for surface-type pleated filters often fail in strenuous conditions, in particular at prolonged exposures (more than about 4 hours) to high temperatures, particularly above about 80xc2x0 C., and even at short term exposures (about 30 minutes) to high temperatures, particularly above about 120xc2x0 C., in not providing the desired rigidity to keep the cartridge structure together along with provision of an adequate seal between the end-cap and the filter housing. Further, many of the materials used in molding conventional end-caps are not suitable for use in food. or pharmaceutical-type regulated applications. Using presently employed materials, fabrication of capped pleated filter elements by this technique further provides an unacceptable number of capped pleated filters having a low bubble point integrity leading to inadequate filtration. Such a technique further is associated with damage occurring in the pleated media near the end-cap due to the necessary force/movement applied to overcome sticking of the molded material to the mold in which it is sitting.
Currently available potted end-caps found on pleated surface-type filters also suffer from several drawbacks. First, such potted end-caps are made typically from metal, often stainless steel, or from materials such as polypropylene, polyester, polysulfone. Such materials lack the flexibility required to act as a seal with the filter housing, and therefore such potted end-caps require a separate gasket to be applied thereto to effectively seal the filter with the filter housing. Further, the adhesives used to join the end-caps to the filter element often fail when exposed to high temperatures. While not wishing to be bound by any theory, the present inventors hypothesize that the cracking of the adhesive under high temperatures, in particular when exposed to temperatures above about 120xc2x0 C., may be due to the wide differential between the coefficient of thermal expansion of the adhesives used in such potting technique and the material comprising the end-cap Cracking of the adhesive leads to a loss of filter integrity as adjudged by the bubble point method. Cracking may occur during the exposure to high temperatures or may occur during cooling from such temperatures. While somewhat reducing cracking, even adding the costly step of blasting the cap to promote adhesion or the use of mold releasing agents to permit more ready movement of the adhesive in portions of end-cap-filter interface, does not entirely resolve this problem.
There is a need, therefore, for a method of fabricating and applying an end-cap to a pleated surface-type filter element which results in an improved seal between the pleated filter element and the end-cap over a wider range of temperatures and/or pressures then presently permitted by existing end-capped pleated filter elements, and which permits the end-cap to coact with the filter housing without need for a separate gasket element.
The present invention provides an improved end-cap method and system for sealing pleated surface-type filter elements over that available in the prior art.
One embodiment of the present invention includes an method for producing a pleated surface-type filter element sealed on one or more ends of the element, comprising the steps of: a) forming an end-cap structure from an elastomeric material; b) applying an adhesive polymer to at least one surface of the pre-formed end-cap structure; c) applying the adhesive-bearing end-cap to a pleated surface-type filter element in a manner to fuse the end-cap to the pleated surface-type filter element without substantially deforming the pleats of the pleated surface-type filter element; d) causing the polymeric adhesive to solidify and to bond the portion of the pleated surface-type filter element elastomeric end-cap structure to which it is in contact.
Still another aspect of the present invention includes a method of manufacturing filter elements for coaction with a filter housing, wherein the filter housing has a sealing edge portion(s) adapted for coacting with said filter element, comprising: a) forming a pleated surface-type filtering element having a top end and a bottom end; b) forming one or two end-cap(s) having an upper surface and a lower surface from an elastomeric polymer, said end-cap(s) for sealing the end of the filtering structure and coacting with the sealing edge portion(s) of the filter housing; c) applying adhesive to one surface of the elastomeric end-cap(s); d) contacting the adhesive surface of the elastomeric end-cap(s) to one or both ends of the pleated surface-type filtering structure; wherein the non-adhered surface of the elastomeric end-cap is of such dimension and shape that when coacted into the sealing edge portion(s) of the filter housing, an effective seal is formed between the filter housing and the pleated surface-type filter element.
Yet another aspect of the present invention includes a method of assembly of a filter element in a filter housing having a sealing edge portion adapted for coaction with a filter element comprising the steps of: a) obtaining a pleated surface-type filter element having one or more ends of the element sealed by an elastomeric end-cap and coupled to the end-cap through a polymeric adhesive; b) inserting the end-capped pleated surface-type filter element of step a into the filter housing such that the end-cap is coacts with the sealing edge portion of the filter housing and forms an effective seal between the filter housing and the filter element.
Another aspect of the present invention is a method for sealing a pleated surface-type filter cartridge comprising one or more layers of thin-walled pleated filter media supported on a relatively rigid core and sealed from the edges of the core to the outer perimeter of the thin-walled filter media by an end-cap formed of elastomeric material, comprising the steps of: a) filling the elastomeric end-cap with an operative amount of adhesive; b) inserting the pleated filter media edges into said adhesive whereby the edges of the filter material are sealed thereby.
And yet another aspect of the present invention is a filter element comprising: a) one or more, preferably two, elastomeric end-caps; b) thin-walled pleated filter medium having edges thereon constructed and arranged for positioning proximate said elastomeric end-caps; c) polymeric adhesive material within said end-caps for sealing the edges of the filter media therein.
Other advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

Method of applying an end-cap to a pleated filter element