Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/16—Discovering, processing access restriction or access information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/18—Selecting a network or a communication service
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W24/00—Supervisory, monitoring or testing arrangements
  • H04W24/08—Testing, supervising or monitoring using real traffic
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W48/00—Access restriction; Network selection; Access point selection
  • H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W60/00—Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
  • H04W60/04—Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration using triggered events

Definitions

• the present invention relates to mobile communication techniques. More particularly, but not exclusively, it relates to Public Land Mobile Network (PLMN) ping pong avoidance mechanisms .
• PLMN Public Land Mobile Network
• NAS Stratum
• GSM Global System for Mobile communication
• UMTS Telecommunications System
• FIG. 1 is a block diagram illustrating a configuration of a typical universal mobile telecommunications system (UMTS).
• UMTS universal mobile telecommunications system
• the typical UMTS comprises of mobile user equipments (UEs) 101, a UMTS terrestrial radio access network (UTRAN) 103 and one or more core networks (CNs) 105 as shown in the fig.l.
• UMTS concerns a third generation radio network using wideband code division multiple access (W-CDMA) technology.
• W-CDMA wideband code division multiple access
• FIG. 2 is a block diagram illustrating a configuration of the typical UTRAN as shown in the fig.l.
• the typical architecture of a the UTRAN comprises of a plurality of Node Bs 201 as base stations and a plurality of radio network controllers (RNCs) 203 as base station controllers.
• the Node Bs handle the actual communication across the radio interface, covering a specific geographical area also referred to as a cell.
• the RNCs include functionality like the allocation of radio resources, local mobility.
• An RNC connects: to one or more core networks via the Iu interface,to a number of base stations (node B's for the case of UTRAN) via the Iub interface andpossibly to one or more other RNCs via the Iur interface.
• FIG. 3 is a block diagram illustrating a configuration of the typical UMTS grouped into the Access Stratum (AS) and the Non-Access Stratum (NAS).
• AS Access Stratum
• NAS Non-Access Stratum
• the fig.3 again shows the UMTS architecture in terms of its entities User Equipment (UE), UTRAN and Core Network.
• UE User Equipment
• UTRAN User Equipment
• Core Network Core Network
• Uu Radio Interface
• Iu CN- UTRAN interface
• the figure illustrates furthermore the high- level functional grouping into the AS 301 and the NAS 303.
• the AS 301 includes the lower radio specific layers of the protocols i.e. in
• the Access Stratum offers services through the following Service Access Points (SAP) to the Non-Access Stratum (marked with circles in the figure): General Control (GC) SAPs;
• SAP Service Access Points
• GC General Control
• DC Dedicated Control
• the NAS 303 includes the upper radio specific layers of the protocols i.e. in UMTS this includes e.g. the Call Control (CC), the Mobility Management (MM) and the Session Management (SM) protocols.
• CC Call Control
• MM Mobility Management
• SM Session Management
• the UE shall initiate the measurements of all neighbour cells indicated in the measurement control system information, regardless of the measurement rales currently limiting UE measurement activities.
• the UE shall initiate cell selection procedures for the selected PLMN as defined in TR 22.811, Review of Network Selection Principles, version 7.0.0 (hereinafter "reference 1")
• a UE in Cell:PCH or URA_PCH is considered to be "out of service area” and shall perform actions according to 25.331.
• CELL_FACH 25.133 clause 5.5.2.3 specifies: The UE is "out of service area” if the UE has evaluated for 4 s that that the serving cell does not fulfil the cell selection criterion S and if the UE has not found any new suitable cell based on searches and measurements of the neighbour cells indicated in the measurement control system information during these 4 s.
• the UE When the UE is "out of service area” it shall initiate cell selection procedures for the selected PLMN as defined in the reference 1.
• an action upon detecting out of service will be described with regard to URA PCH state, CELL PCH state and CELLJFACH state in detail.
• 25.331 specifies the following:
• the UE detects the "out of service area" and the UE is in URA PCH or CELLJPCH state it shall perform the following actions: 1> start timer T316; 1> perform processes described in subclause 7.2.2.
• the UE shall camp on that cell to obtain limited service as defined in the reference 2 and, perform actions according to subclause 8.5.24; 3> else if no acceptable cell is found, the UE shall continue looking for an acceptable cell as defined in the reference 2.
• 25.304 specifies the following:
• the UE shall scan all RF channels in the UTRA bands according to its capabilities to find available PLMNs. On each carrier, the UE shall search for the strongest cell and read its system information, in order to find out which PLMN the cell belongs to. If the UE can read the PLMN identity, the found PLMN shall be reported to the NAS as a high quality PLMN (but without the RSCP value), provided that the following high quality criterion is fulfilled:
• the measured primary CPICH RSCP value shall be greater than or equal to -95 dBm.
• the measured P-CCPCH RSCP shall be greater than or equal to -84 dBm.
• Found PLMNs that do not satisfy the high quality criterion, but for which the UE has been able to read the PLMN identities are reported to the NAS together with the CPICH RSCP value for UTRA FDD cells and P-CCPCH RSCP for UTRA TDD cells.
• the search for PLMNs on the rest of the carriers may be stopped on request of the NAS.
• the UE may optimise this search by using stored information of carrier frequencies and optionally also information on cell parameters, e.g. scrambling codes, from previously received measurement control information elements.
• the cell selection procedure shall be performed in order to select a suitable cell of that PLMN to camp on.
• cell selection and PLMN re- selection in detail.
• 25.304 specifies the following: 5.2.3 Cell Selection Process
• the UE shall use one of the following two search procedures: a) Initial Cell Selection This procedure requires no prior knowledge of which RF channels are
• the UE shall scan all RF channels in the UTRA bands according to its capabilities to find a suitable cell of the selected PLMN. On each carrier, the UE need only search for the strongest cell. Once a suitable cell is found this cell shall be selected. b) Stored Information Cell Selection
• This procedure requires stored information of carrier frequencies and optionally also information on cell parameters, e.g. scrambling codes, from previously received measurement control information elements.
• Table 1 to Table 3 below illustrate criteria and variable defined for cell selection.
• the cell selection criterion S is fulfilled when: Table 1 for FDD cells: Srxlev > 0 AND Squal > 0 for TDD cells: Srxlev > 0
• the MS selects and attempts registration on other PLMN/access technology combinations, if available and allowable, in the following order: i) HPLMN (if not previously selected); ii) each PLMN/access technology combination in the "User Controlled PLMN Selector with Access Technology" data file in the SIM (in priority order); iii) each PLMN/access technology combination in the "Operator Controlled PLMN Selector with Access Technology” data file in the SIM (in priority order); iv) other PLMN/access technology combinations with received high quality signal in random order; v) other PLMN/access technology combinations in order of decreasing signal quality.
• An MS with voice capability shall ignore PLMNs for which the MS has identified at least one GSM COMPACT.
• An MS using a SIM without access technology information storage i.e.
• the MS shall search for all access technologies it is capable of and shall assume GSM access technology as the highest priority radio access technology.
• the MS shall search for all access technologies it is capable of, before deciding which PLMN to select.
• a packet only MS which supports GSM COMPACT, but using a SIM without access technology information storage i.e.
• the "User Controlled PLMN Selector with Access Technology" and the "Operator Controlled PLMN Selector with Access Technology" data files are not present) shall instead use the "PLMN Selector" data file, for each PLMN in the "PLMN Selector” data file, the MS shall search for all access technologies it is capable of and shall assume GSM COMPACT access technology as the lowest priority radio access technology.
• the MS shall search for all access technologies it is capable of. No priority is defined for the preferred access technology and the priority is an implementation issue, but "HPLMN Selector with Access Technology" data file on the SIM may be used to optimise the procedure.
• an MS using a SIM without access technology information storage i.e.
• the "HPLMN Selector with Access Technology" data file shall search for all access technologies it is capable of and shall assume GSM access technology as the highest priority radio access technology.
• a packet only MS which supports GSM COMPACT using a SIM without access technology information storage shall also assume GSM COMPACT access technology as the lowest priority radio access technology.
• the MS shall order the PLMN/access technology combinations in order of decreasing signal quality within each access technology. The order between PLMN/access technology combinations with different access technologies is an MS implementation issue.
• NOTE 1 Requirements a) and b) apply also to requirement d), so a GSM voice capable MS should not search for GSM COMPACT PLMNs, even if capable of GSM COMPACT.
• the MS indicates the selected PLMN.
• the MS indicates "no service" to the user, waits until a new PLMN is available and allowable and then repeats the procedure.
• the UE will be momentarily out of coverage but will not declare out of service (OOS), and then it will come back to the serving cell.
• OOS out of service
• the UE will declare Out-of- service(OOS) and start scanning, but then will most likely come back to the same 3G cell.
• the UE may go to a national roaming partner, but after 6 minutes it is likely to come back to the same weak 3 G cell upon the first background HPLMN search.
• Means should be reviewed to improve the effect of ping ponging between registration areas. It should be possible for allow the network to be configured by the operator so as to enable the definition of different quality criteria for leaving and coming back to a cell/PLMN.
• the UE When the UE is near the edge of the operators PLMN coverage area, the UE may go 'out of service 5 .
• TMeasurement Period Intra (_FACH) or for Nserv consecutive DRX cycles (idle & _PCH). Note 1. Network operators normally configure their network such that even cells that are quite bad will still meet the criteria for a suitable cell - they don't like mobiles to indicate 'out of service'.
• the UE will search for another cell on the current (e)PLMN, based on the neighbouring cell list (both inter-Frequency and inter- RAT neighbours).
• Cell re-selection is initiated if a suitable cell is found for the current (e)PLMN.
• a UE in connected mode is considered to be 'out of service'. Furthermore, the UE shall acts as defined below.
• the UE performs a complete scan of all RATs and all frequency bands supported by the UE in an attempts to find a suitable cell for the current (e)PLMN.
• the UE does not need to perform a routing area update unless it is changing Routing Area i.e. there may not be NAS signalling involved.
• the UE does not stop T305 (5 min. or higher) and/ or T307 (5 through 50 sec) upon reporting available PLMNs.
• the UE should indicate the available PLMNs to facilitate re-selection of another PLMN.
• the UE-AS reports the available PLMNs.
• UE-AS reports PLMNs for which the 'high quality criterion' is fulfilled as 'high quality PLMNs'.
• UE-AS also reports other available PLMNs i.e. PLMNs for which the UE managed to read the PLMN identity on BCCH, together with a measured quality (p-CPICH RSCP in case of FDD).
• the UE When reporting available PLMNs, the UE need not verify if the cell from which it reads the PLMN identity is suitable e.g. whether or not it is barred.
• the UE-NAS selects a PLMN from the available PLMNs indicated by AS, in the following order of preference:
• PLMNs/ access technologies indicated as 'high quality', randomly.
• PLMNs/ access technologies in order of signal strength.
• the UE periodically performs a background scan for available PLMNs.
• the UE may re-select a different PLMN each time.
• the UE may move back towards the original cell/ PLMN, even though the quality of the original UMTS cell may still be quite bad -just about suitable.
• the UE may ping pong between the PLMNs regularly.
• the main adverse effects associated with this PLMN-ping pong are the signalling load and the temporary user unavailability, (i.e. 34- 42 seconds and associated signalling delays for every ping pong).
• an object of an exemplary embodiment of the present invention to provide an apparatus and method for PLMN ping pong avoidance.
• PLMN reselections are forbidden after a loss of 3 G coverage even if the UE is in idle mode.
• a method for improving network selection and/or network re-selection of a mobile terminal in a cellular communications system by specifying radio quality criteria to avoid repeated change of networks.
• a mobile terminal for use in a cellular communications network, adapted to select or re-select a PLMN based on radio quality criteria for avoiding repeated change of PLMN in the process of PLMN selection.
• a network element in a cellular communications network adapted to provide radio quality criteria for a mobile terminal selecting or re-selecting a PLMN.
• FIG. 1 is a block diagram illustrating a configuration of a typical universal mobile telecommunications system (UMTS);
• UMTS universal mobile telecommunications system
• FIG. 2 is a block diagram illustrating a configuration of a typical UTRAN as shown in the fig.1 ;
• FIG. 3 is a block diagram illustrating a configuration of the typical UMTS grouped into the Access Stratum (AS) and the Non-Access Stratum (NAS);
• AS Access Stratum
• NAS Non-Access Stratum
• FIG. 4 shows an example of the use of a criteria for a scenario including OOS according to an exemplary embodiment of the present invention
• FIG. 5 is a flowchart illustrating the communications between the UE-AS, UE-NAS and a network element according to one embodiment of the present invention
• FIG. 6 is a schematic illustration of a deployment scenario according to another embodiment of the present invention.
• a duration specifying how long the offsets are to be applied (Tens of seconds/ tens of minutes) .
• the UE acquires the parameters from the candidate cell, which broadcasts these possibly cell specific parameters as part of cell selection parameters (SIB3).
• SIB3 cell selection parameters
• the UE shall consider a cell of the RPLMN (upon OOS)/ higher priority
• PLMN (upon ABS) suitable only if it meets the Scriteria after applying the concerned temporary hysteresis offset to each of the quality criteria.
• UE-AS may report to NAS fewer available PLMNs than PLMNs found suitable according to the original criteria.
• the UE When detecting OOS from a cell broadcasting PPPA-control parameters, the UE starts applying the temporary discouragement towards the concerned cell. At the same time, the UE starts an 'OOS-discouraged PLMN' timer. The UE stops applying the temporary discouragement towards a cell of the 'OOS- discouraged PLMN' when the timer exceeds the value broadcast by the concerned cell. The UE also stops applying the temporary discouragement towards the 'OOS-discouraged PLMN' when re-entering 'in service area'.
• the UE Upon entering a VPLMN, the UE starts an 'ABS-discouraged PLMN' timer.
• the UE applies the temporary discouragement as long as the timer exceeds the value broadcast by the concerned cell.
• the UE restarts the 'ABS-discouraged PLMN' timer.
• the PPPA-mechanism is proposed to apply to a PLMN regardless of whether the UE was previously registered on it.
• Quality level approach Different quality levels i.e. by specifying that the UE should only move back if the quality level is sufficiently high e.g. offset higher than the criteria for leaving the cell/ considering out of service.
• Quality duration approach Different quality durations i.e. by specifying that the UE should only move back if the conditions for returning last longer than for leaving/ detecting out of service e.g. by using a scaling factor for the timer (e.g. similar to what we have for Treselection).
• a timer based mechanism has the disadvantage that it could further increase the duration of the 'unavailability period'.
• a PLMN ping pong avoidance mechanism can either utilise a quality level, a quality duration based criterion.
• the ping pong avoidance could, irrespective of which mechanism is used, be temporary meaning that ping pong avoidance is limited to a specific duration.
• a timer based mechanism is most suitable for limiting the duration while for UEs that are (starting) to move, a mechanism based on the movement of the UE could be used e.g. the number of cell re-selections, the distance moved since the UE was registered on the previous PLMN (e.g. in case the UE ).
• the PLMN ping pong avoidance could, irrespective of which mechanism is used, be temporary. This could be done by means of a timer based mechanism and/ or in combination with a mechanism related to the UE movement e.g. the number of cell re-selections or the distance moved since the UE was registered on the previous PLMN.
• a permanent mechanism can be used. The following considerations lead to the thought that a permanent mechanism may in fact result in a better solution than use of a temporary mechanism:
• a timer based temporary mechanism may cause the
• the PPPA- mechanism is proposed to apply to a PLMN regardless of whether the UE was previously registered on it. This implies that the UE does not need to record the
• the S-criterion is typically set to a rather low value i.e. a value that does not guarantee that the UE is able to properly communicate with the network.
• the UE may select a PLMN for which the radio link quality is quite poor. In such a case, it may be desirable to allow the UE to select a lower priority PLMNs that is able to offer a proper level service.
• Permanent mechanism is used in the following to denote a mechanism that is not applied in a temporary manner.
• the UE would apply the permanent discouragement upon every PLMN re- selection, possibly including the manual ones i.e. UE-AS only indicates PLMNs as available after considering the permanent discouragement threshold, broadcast by the concerned cell.
• the UE would not apply the parameters upon initial PLMN selection, to avoid excessive delays in case only single PLMN is found.
• the mechanism would otherwise imply that the UE has to try all frequencies and RATs before deciding not to apply the discouragement (see exception condition, previous IPR)
• the UE In line with the original IPR, the UE should not apply the permanent discouragement either if the 'previous PLMN' is the only PLMN the UE finds suitable according to the original criteria.
• One quality criterion for leaving a PLMN i.e. if the quality is below this threshold, the UE is allowed to leave the current PLMN.
• One quality criterion for entering a PLMN i.e. the UE should only enter a PLMN if the quality is above this threshold.
• One quality criterion for displaying 'out of service' i.e. for not considering any of the available PLMNs as suitable.
• FIG. 4 shows an example of the use of the above criteria for a scenario including OOS according to an exemplary embodiment of the present invention.
• the scenario illustrated in the Fig. 4 can be describe in terms of a number of events, marked as Tn in the figure: TO When the quality of the current cell drops below S LEAVE 403 UE-AS starts a Timer-A (4s when in CELLJFACH 5 12s otherwise). UE-AS continues cell re-selection for the registered (e)PLMN
• Tl Timer-A started at TO expires, indicating that the quality of the current cell has been below S LE A VE 403 long enough to detect OOS.
• the UE-AS starts Timer-B.
• the UE has not left the registered PLMN as yet, but from now on UE-AS applies cell selection for the registered (e)PLMN
• T6 The quality of the current cell drops below S No serV i ce 405upon which the UE starts to display 'no service' .
• the UE-AS continues cell selection for any PLMN
• T7 The quality of the single PLMN that UE-AS is able to detect current cell exceeds S No serv i ce 405 upon which the UE stops to display 'no service' and resumes normal service for the concerned PLMN i.e. UE-AS reports the PLMN as available, UE-NAS initiates registration upon which the concerned PLMN becomes the registered PLMN
• T8 The quality of one of the PLMNs that the UE was able to detect exceeds S Entry 401 upon which the UE stops to display 'no service' and resumes normal service for the concerned PLMN, as for T7
• Timer-B as described in the previous, could be made operator configurable in order to introduce a more flexible 'leaving condition'
• the above table shows that with cell selection, the UE accepts an alternative frequency/RAT earlier/at a higher quality level.
• the UE Due to the lowness of the S-criteria, it is likely the UE is unable to reach the broadcast channel correctly. Hence, the cell re-selection parameter values that the UE previously read from the broadcast channel may not be up to date anymore.
• the UE may have moved away from the cell in which it read the broadcast information.
• the set of neighbours broadcast by the original cell may not be appropriate for the area the UE has moved to.
• the new 'leave condition' may corresponds with a certain likelihood that the UE is able to receive the broadcast and paging channels, as well to transmit the initial access message.
• the arguments indicated above are assumed to still apply, although maybe to a lesser extend. Another consideration could be that from a UE implementation perspective it would be easier to apply cell selection criteria when searching all frequencies and RATs i.e. this may be more similar to the UE implementation for other scenario's.
• the UE may be able to receive the broadcast channel, although it may take a little longer, we do not wish to exclude the option to apply cell re- selection either:
• Timer-B While the UE operates Timer-B, it either applies cell selection or cell re- selection for the registered (e)PLMN.
• the proposed solution addresses the basic root of problem rather than finding a solution around some adverse characteristics. Compared to the temporary solution, the proposed mechanism results in a simpler solution i.e. avoiding the complexities of start and stop conditions of a temporary mechanism.
• the characteristics of the mechanism to prevent ping ponging may depend on where the function is implemented.
• One main factor is the nature of the available radio quality information, which differs between protocol layers e.g. UE-AS has more detailed information available than UE-NAS.
• UE-NAS only has limited radio quality information available i.e. upon performing a full scan, UE-AS indicates which of the available PLMNs are high quality and for the other (low quality) PLMNs it provides a single measured quality e.g. the CPICH RSCP value in case of FDD.
• the UE-AS typically has more quality information available e.g. for FDD it also applies the Ec/No measurement.
• Another aspect is that UE-AS is aware about the parameters/ criteria for making a cell suitable i.e. the criteria for 'leaving the PLMN'.
• the availability of more detailed radio quality information enable the UE- AS is able to make a better judgement about the quality of a radio link than UE- NAS.
• additional use of the Ec/No quality measures will result in decisions taking the uplink interference/ quality better into account.
• the PLMN ping pong avoidance mechanism can utilise more than one condition e.g. to reflect both uplink and downlink quality conditions.
• the PLMN ping pong avoidance mechanism could either be implemented in AS or in NAS.
• the PLMN ping pong avoidance mechanism can either utilise relative or absolute quality conditions.
• a PLMN may include access networks using more than one radio access technology (RATs) e.g. GSM, UMTS 5 LTE.
• RATs radio access technology
• GSM Global System for Mobile communications
• UMTS 5 LTE Universal Mobile Broadband
• each radio access technology different measurement quantities may be used to indicate the quality of the radio connection.
• each radio technologies may have quite different characteristics. This means that the quality avoidance control parameters e.g. those related to the quality level, as used in different radio access technologies may need to be different.
• the PLMN ping pong avoidance mechanism allows the use of different control parameters for different radio technologies in order to accommodate PLMNs including of multiple ratio access technologies.
• the PLMN ping pong avoidance mechanism allows the use of different control parameters for different radio technologies in order to accommodate PLMNs including of multiple ratio access technologies.
• the network that the UE should re-enter/ return to should provide the control information, since that is the appropriate network to indicate that it allows the UE to stay longer in another PLMN (so as to avoid excessive signalling & bad user experience). If the control parameters were provided in the currently registered PLMN 5 it would be easy to misuse the control parameters in an attempt to keep the UEs in the current PLMN, although that is not preferred by the use & nor by its home PLMN operator.
• the PLMN ping pong avoidance control parameters should be provided by the radio access network the UE should avoid to return to i.e. the previously registered PLMN.
• the parameters to control the PLMN ping pong avoidance could be provided to the UE in different ways:
• the UE acquires the parameters when it was previously registered on the PLMN and stores them for later use i.e. when this PLMN has become the previous PLMN.
• the UE could e.g. apply a variable 'previous PLMN' to store this information.
• the UE acquires the parameters from the PLMN at the time it attempts to return to the PLMN.
• the UE may acquire the PLMN ping pong avoidance control parameters either when it was previously registered on the PLMN (in which case it needs to store them for later use) or it may acquire them when attempting to return to the concerned PLMN.
• the PLMN ping pong avoidance control parameters are assumed to be broadcast. In case the UE acquires the parameters from the PLMN at the time it attempts to return to the PLMN, it would be beneficial to signal these parameters together with the PLMN identity which the UE anyhow has to read at that time.
• the PLMN ping pong avoidance control parameters may be broadcast and may be signalled together with the PLMN identity.
• MIB Master Information Block
• the drawbacks of the PLMN ping pong are considered to be more severe when the UE is in connected mode as compared to when the UE is in idle mode.
• the signalling overhead would be the same in both cases, the user is considered to be more susceptible to 'temporary unavailability' when in connected mode - which should normally correspond with a higher level of activity.
• the Master information block is transmitted frequently. Hence, addition of new parameters is only acceptable if there is good justification. Also in general adding parameters to system information messages should be done with care considering the relative cost of broadcasting transmission mechanism. Hence, it may be desirable to perform some signalling optimisation.
• One possibility would be to, when a quality criterion considering both Ec/No and RSCP quality measures is introduced, to anyhow to signal a single 'Quality offset' parameter. This single parameter could possibly indicate the offset values to be used for each measurement quantity by means of a mapping table e.g. as shown below Table 5.
• a PLMN ping pong avoidance mechanism utilising:
• the temporary nature is realised by means of a timer e.g. TimerPPA.
• the PLMN ping pong avoidance control parameters are provided by the radio access network the UE should avoid to return to i.e. the previously registered PLMN as follows.
• the UE acquires the parameters at the time it attempts to return to the PLMN i.e. during the full scan performed by the UE (meaning that the control parameters need not be stored by the UE).
• the control parameters may be specific to the cell (and hence implicitly also to the radio access technology).
• control parameters could be included in the Master Information Block.
• the mechanism is primarily implemented in UE-AS with some support by
• UE-NAS in order to avoid that the UE-AS needs to store information concerning a PLMN the UE is currently not registered on.
• FIG. 5 is a flowchart illustrating the communications between the UE-AS, UE-NAS and a network element according to one embodiment of the present invention.
• UE-AS reports to UE-NAS that it is going out of service on a PLMN (i.e. a suitable cell is not even found after a full scan).
• the UE-NAS stores information to avoid ping pong to this PLMN e.g. it may store the PLMN identity, possibly with a 'ping pong avoidance flag'. Possibly this information could be stored with other information in UE-NAS e.g. the forbidden PLMNs information.
• step 503 when UE-NAS requests the UE to indicate the available PLMNs, UE-NAS provides the PLMN identity of the PLMN the UE should avoid to return to.
• step 505 when UE-AS performs a full scan and finds PLMNs with the concerned PLMN identity or one equivalent to that, the UE acquires the ping pong avoidance control parameters from the concerned cell (Network).
• step 507 the UE-AS reports the concerned PLMN as one of the available PLMNs unless the ping pong avoidance conditions are met:
• the quality is below the required level e.g. either the Ec/No or the CPICH RSCP is less than offset higher than the criteria for making the cell suitable, the duration is also below the required value i.e. TimerPPA has not expired.
• UE-NAS maintains a ping pong avoidance flag which is set upon receiving an 'out of service' indication from UE-AS.
• the 'out of service' indication could not only include the identity of the previous PLMN, but also information about the radio access technology or the actual cell in which the out of service condition was triggered. This additional information could be used to introduce a more specific ping pong avoidance flag i.e. to avoid ping pong not to the entire PLMN but only to the same cell or the same RAT.
• the ping pong avoidance mechanism could either be generic i.e. avoiding return to the entire previous PLMN or it could be more specific i.e. avoiding return to a specific part of the PLMN e.g. the previous RAT, the previous cell.
• FIG. 6 is a schematic illustration of a deployment scenario according to another embodiment of the present invention.
• the Fig. 6 illustrates a possible network deployment scenario in an area in which UMTS and GSM cells are deployed.
• different colours indicate different PLMN identities.
• a UE on PLMN B may be configured with an equivalent
• PLMN i.e. PLMN identity A.
• the ping pong avoidance mechanism would now be able to avoid the UE ping pongs between cell a and cell b.
• the ping pong avoidance mechanism would now be able to avoid the UE ping pongs between cell a and cell b.
• PLMN identity the mechanism does not prevent that the UE moves to cell c.
• the cell re-selection configuration is such that the UE is stimulated to move back to cell a, we may still have a problem.
• this is considered to be an unlikely scenario since normally in a deployment situation like the above, the UE should re-select to cell c even before detecting out of service in cell a. Hence, it seems that no specific handling is needed to accommodate the case equivalent PLMNs are configured.
• the ping pong avoidance conditions only have adverse effect and hence our proposal is that in this case the conditions should not be applied.
• the ping pong avoidance criterion should not be applied if the 'previous PLMN' is the only PLMN the UE detects.

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• 2006
  • 2006-01-24 GB GB0601407A patent/GB2434507A/en not_active Withdrawn
  • 2006-05-04 GB GB0608843A patent/GB2434508B/en not_active Expired - Fee Related
• 2007
  • 2007-01-24 JP JP2008552231A patent/JP5371447B2/ja not_active Expired - Fee Related
  • 2007-01-24 WO PCT/KR2007/000420 patent/WO2007086679A1/en not_active Ceased
  • 2007-01-24 EP EP07701058.5A patent/EP1985038B1/en not_active Ceased
  • 2007-01-24 CN CNA2007800103947A patent/CN101411091A/zh active Pending
  • 2007-01-24 CN CN201310168077.5A patent/CN103237336B/zh not_active Expired - Fee Related
• 2008
  • 2008-08-22 KR KR1020087020715A patent/KR101342734B1/ko not_active Expired - Fee Related

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