an overview of registrations in cdma2000 1xrtt network
TRANSCRIPT
An Overview of Registrations in CDMA 2000 1x RTT Network
INDEX
1 Executive Summary
2 Types of Registration
2.1 Power-Up Registration
2.2 Power-Down Registration
2.3 Timer-Based Registration
2.4 Distance-Based Registration
2.5 Zone-Based Registration
2.6 Parameter-Change Registration
2.7 Ordered Registration
2.8 Implicit Registration
2.9 Traffic Channel Registration
2.10 User Zone Registration
3 Registration Procedures on Network Side
3.1 IS-41 Signalling Message Flow for Registration
3.2 Successful RegistrationNotification: Confirmed at the HLR
4 Multiple Registrations in border area (Signal Strength Arbitration)
1.2. Executive Summary
Registration is one of the very important aspects of CDMA Mobile Network. It is the process by which the network comes to know about the location of a subscriber and its other capabilities like the ability to receive SMS & Terminating voice calls etc.
In any Mobile Network, the only entity, which keeps the track of the location of the subscriber, at any instant of time, is Home Location Register (HLR). The HLR comes to know about the location of a MS through the Registration process.
As long as the subscriber doesn’t Register into the network, he / she is not allowed to use any of the network resources. To register into a network, the user must be a valid subscriber of the network.
This document gives the details of the different type of Registration Events, on which a subscriber can be forced to register into the network. This document also details the precise procedure of Registration followed by the network with appropriate signaling flow diagrams.
This document at the end gives certain recommendations regarding the events on which the subscriber should be forced to register & the number of registration per subscriber in a busy hour to be adopted in the Reliance’s network.
3. Types of Registration
Registration is the process by which the mobile station notifies the base station of its location, status, identification, slot cycle, and other characteristics. The mobile station informs the base station of its location and status so that the base station can efficiently page the mobile station when establishing a mobile station terminated call. For operation in the slotted mode, the mobile station supplies the SLOT_CYCLE_INDEX parameter so that the base station can determine which slots the mobile station is monitoring. The mobile station supplies the station class mark and the protocol revision number so that the base station knows the capabilities of the mobile station.The CDMA system supports ten different forms of registration:
1. Power-up registration. The mobile station registers when it powers on, switches from using a different frequency block, switches from using a different band class, switches from using an alternative operating mode, or switches from using the analog system.
2. Power-down registration. The mobile station registers when it powers off if previously registered in the current serving system.
3. Timer-based registration. The mobile station registers when a timer expires.
4. Distance-based registration. The mobile station registers when the distance between the current base station and the base station in which it last registered exceeds a threshold.
5. Zone-based registration. The mobile station registers when it enters a new zone.
6. Parameter-change registration. The mobile station registers when certain of its stored parameters change or when it enters a new system.
7. Ordered registration. The mobile station registers when the base station requests it.
8. Implicit registration. When a mobile station successfully sends an Origination Message or Page Response Message, the base station can infer the mobile station’s location. This is considered an implicit registration.
9. Traffic Channel registration. Whenever the base station has registration information for a mobile station that has been assigned to a Traffic Channel, the base station can notify the mobile station that it is registered.
10.User Zone Registration. The mobile station registers when it selects an active User Zone.
The first five forms of registration, as a group, are called "autonomous registration" and are enabled by roaming status. Parameter-change registration is independent of roaming status. Ordered registration is initiated by the base station through an Order Message. Implicit registration does not involve the exchange of any (explicit) registration messages between the base station and the mobile station. The base station can also "obtain" registration information by sending the Status Request Message to the mobile station on either the f-csch or the f-dsch. The base station can obtain limited registration information by sending the Status Request Order to the mobile station on the f-dsch. The mobile station can be notified (back, by the Network) that "it is now registered", through the Mobile Station Registered Message.Any of the various forms of autonomous registration and parameter-change registration can be enabled or disabled in a given Network. The enabling / disabling is generally "Administratable at site" and is hence, possible using the appropriate Man Machine commands. The forms of registration that are enabled and the corresponding registration parameters are communicated by the network to all the Mobile Stations in the System Parameters Message.In addition, the mobile station (itself) may also enable or disable autonomous registration for each type of roaming (Foreign NID Roaming, Foreign SID Roaming, etc.).
1. Power-Up Registration
Power-up registration is performed when the mobile station is turned on. To prevent multiple registrations when power is quickly turned on and off, the mobile station delays the "initiation of
registration" for (typically) 20 seconds before registering, after entering the Mobile Station Idle State.
The mobile station maintains a power-up/initialization timer. While the power- up/initialization timer is active, the mobile station can not make registration access attempts.
Power-up registration can be controlled by the network, by sending System Parameter Message on air interface with "power_up_reg" parameter value equal to 0 (Zero – meaning disabled) or 1 (One – meaning enabled).
Though the controlling (initiating) entity for this type (Power-up) of registration is the Mobile station (MS), the ‘control’ in this regards is really exercised by the Network; the MS behaves as per the directive from the Network, which it (the MS) receives in the System Parameter Message. For the situation when Power-on registration is enabled by the System, the MS would notice (in the System Parameter Message) upon getting powered up, that this type of registration is enabled. However, as described earlier, the mobile station waits for around 20 Seconds and then initiates the registration procedures.
The process for Power-up registration can be shown in the Flow Chart form as follows:
2. Power-Down Registration
Power-down registration is performed when the Mobile user directs the mobile station to power off. If power-down registration is to be performed, the mobile station does not power off until after completing the registration attempt.
The mobile station performs power-down registration (only) if it has previously registered in the system that corresponds to the current SIDs and NIDs.
Power down registration can be controlled by the network, by sending System Parameter Message on air interface with "power_down_reg" parameter value equal to 0 (Zero – meaning disabled) or 1 (One – meaning enabled).
As in the case of Power Up Registration, the MS looks for & follows the directive given by the Network. The MS already knows that the
power down registration is turned ON by the system by looking at the System Parameter message. When the MS is turned OFF, it starts the power down registration procedures. As stated earlier, the MS actually turns the power OFF only after completing the power down registration procedure.
The process for Power-down registration can be shown in the Flow Chart form as follows:
3. Timer-Based Registration
Timer-based registration causes the mobile station to register at regular intervals. Its use also allows the system to automatically deregister mobile stations that did not (or could not) perform a successful power-down registration. Timer-based registration uses a Paging Channel slot counter (equivalent to a timer with time increments of 80 ms). Timer-based registration is performed when the counter reaches a maximum value (REG_COUNT_MAXs) whose value is controlled by the base station via the REG_PRD field of the System Parameters Message.
The base station disables timer-based registration by setting REG_PRD to zero.
The mobile station maintains a timer-based registration counter (REG_COUNTs). The mobile station computes and stores the timer expiration count (REG_COUNT_MAXs) as REG_COUNT_MAXs = 2(REG_PRD / 4).
The REG_PRD can have values in between 0 and 127.
The mobile station maintains an indicator of timer-based registration timer enable status (COUNTER_ENABLEDs).
The counter is reset when the mobile station powers on and when the mobile station switches from different band classes, different serving systems, different PCS frequency blocks, and alternate operating modes. The counter is also reset after each successful registration.
Whenever the mobile station changes COUNTER_ENABLEDs from NO to YES, it sets REG_COUNTs to a pseudorandom value between 0 and REG_COUNT_MAXs - 1, using the pseudorandom number generator.
If the mobile station is operating in the non-slotted mode, it increments the timer- based registration counter once per 80 ms (it does so, of course, only whenever COUNTER_ENABLED equals YES). If the mobile station is operating in slotted mode, it may increment the timer-based registration counter when it begins to monitor the Paging Channel. A mobile station operating in the slotted mode increments the counter by the same amount that the counter would have been incremented if the mobile station had been operating in the non-slotted mode.
The controlling (initiating) entity for Timer Based Registration is MS. The Timer setting should be done at the BS. The BS transmits the Registration Period (REG_PRD) parameter in the "System Parameter Message". After the first time Registration, the MS sets a timer according to the value of REG_PRD parameter received. When the timer expires, the MS initiates the Timer Based Registration procedures.
The periodic registration time is determined by the MS using following formula:
Periodic Registration Timer = { [ 2( REG_PRD / 4 ) ] * 0.08 } Seconds.
The Timer values calculated by using this formula for different values of REG_PRD are listed in the following table:
Table 1.0:
REG_PRD value
Corresponding value in Minutes
58 31
59 37
60 44
61 52
62 62
63 74
64 88
65 104
66 124
The process for Timer Based registration can be shown in the Flow Chart form as follows:
4. Distance-Based Registration
Distance-based registration causes a mobile station to register when the distance between the current base station and the base station in which it last registered exceeds a threshold. The mobile station determines that it has moved a certain distance by computing a distance measure based on the difference in latitude and longitude between the current base station and the base station where the mobile station last registered. If this distance measure exceeds the threshold value, the mobile station registers.
The mobile station stores the base station latitude (BASE_LAT_REGs-p), the base station longitude (BASE_LONG_REGs-p) and the registration distance (REG_DIST_REGs-p), of the base station to which the first access probe (for a Registration Message, Origination Message, or Page Response Message sent on the r-csch) was transmitted after entering the System Access State. The mobile station shall compute the current base station’s distance from the last registration point i.e. BTS (DISTANCE) as follows:
Where
And
The distance between the two BTSs is calculated by the following formula:
D = R * (1 / 3600) * (/ 180) * (4 * REG_DIST)
Based on different values of "REG_DIST", the actual distances between the BTSs are calculated by using this formula. Some of the distances are listed in the following table
Table 2.0
REG_DIST Actual distance btn the BTSs (in Km)
1 0.124
2 0.248
6 0.745
12 1.489
13 1.613
14 1.738
18 2.234
19 2.358
24 2.979
30 3.723
40 4.964
50 6.205
The mobile station computes the distance within ±5% error extent of its true value when |BASE_LAT_REGs-p/14400| is less than 60 and within ±7% error extent of its true value when |BASE_LAT_REGs-p/14400| is between 60 and 70.
Whenever the distance calculated by the MS (using the formula, as above, based on the Latitude & Longitude of the BTSs) exceeds the value corresponding to the distance as per the REG_DIST parameter transmitted by BS, it performs the distance-based registration.
The initiating entity for this type of registration is the MS. The REG_DIST parameter is set / controlled at base station.
5. Zone-Based Registration
Registration zones are groups of base stations within a given system and network. A base station’s zone assignment is identified by the REG_ZONE field of the System Parameters Message.
Zone-based registration causes a mobile station to register whenever it moves into a new zone, not on its internally stored list of visited registration zones. A zone is added to the list whenever a registration (including implicit registration) occurs, and is deleted upon expiration of a timer. After a system access, timers are enabled for every zone except one that was successfully registered by the access.
A mobile station can be registered in more than one zone. Zones are uniquely identified by a zone number (REG_ZONE) plus the SID and NID of the zone.
The mobile station maintains a zone list entry timer for each entry in ZONE_LISTs.
When an entry in ZONE_LISTs is removed from the list, the corresponding zone list entry timer shall be disabled. The timer duration shall be as determined from the stored value of ZONE_TIMERs using Table 3.0 given below. The mobile station provides a means to examine each timer’s value while the timer is active, so that the age of list entries can be compared.
Table 3.0
If the mobile station supports Band Class 1, the mobile station maintains an identifier of the PCS frequency block for each entry in ZONE_LISTs. When the mobile station adds a zone to ZONE_LISTs, the mobile station includes the identifier for the PCS frequency block.
If the mobile station supports multiple band classes, the mobile station maintains an identifier of the band class for each entry in ZONE_LISTs. When the mobile station adds a zone to ZONE_LISTs, the mobile station includes the identifier for the band class.
The base station controls the maximum number of zones in which a mobile station may be considered registered, by means of the TOTAL_ZONES field of the System Parameters Message. When an entry is added to the zone list, or if TOTAL_ZONES is decreased, the mobile station removes entries from the zone list if there are more entries than allowed by the setting of TOTAL_ZONES.
Whenever ZONE_LISTs contains more than TOTAL_ZONESs entries, the mobile station deletes the excess entries according to the following rules:
• If TOTAL_ZONESs is equal to zero, the mobile station deletes all entries.
• If TOTAL_ZONESs is not equal to zero, the mobile station deletes those entries having active zone list entry timers, starting with the oldest entry, as determined by the timer values, and continuing in
order of decreasing age until no more than TOTAL_ZONESs entries remain.
The mobile station stores a list of the systems/networks in which the mobile station has registered (SID_NID_LISTs). Each entry in SID_NID_LISTs includes the (SID, NID) pair for the system/network. The mobile station is capable of storing at least 4 entries in SID_NID_LISTs. A base station shall be considered to be in the SID_NID_LISTs only if the base station’s SID and NID are found in an entry in SID_NID_LISTs. The mobile station provides storage for one entry of SID_NID_LISTs in semi-permanent memory (SID_NID_LISTs-p).
Whenever SID_NID_LISTs contains more than 4 entries, the mobile station deletes the excess entries according to the following rule:
• The mobile station deletes those entries having active SID/NID list entry timers, starting with the oldest entry, as determined by the timer values, and continuing in order of decreasing age.
Whenever MULT_SIDSs is equal to ‘0’ and SID_NID_LIST contains entries with different SIDs, the mobile station deletes the excess entries according to the following rules:
• If the SID/NID entry timer for any entry is disabled, the mobile station deletes all entries not having the same SID as the entry whose timer is disabled;
• Otherwise, the mobile station deletes all entries not having the same SID as the newest entry in SID_NID_LIST, as determined by the timer values.
Whenever MULT_NIDSs is equal to ‘0’, and SID_NID_LIST contains more than one entry for any SID, the mobile station deletes the excess entries for each SID according to the following rules:
• If the SID/NID entry timer for any entry is disabled, the mobile station deletes all entries for that SID except the entry whose timer is disabled;
• For all other SIDs, the mobile station deletes all entries for each SID except the newest entry, as determined by the timer values.
The initiating entity for Zone based Registration is the MS. The Zones are defined at the BS.
6. Parameter-Change Registration
Parameter-change registration is performed when a mobile station modifies any of the following stored parameters:
The preferred slot cycle index (SLOT_CYCLE_INDEXp) The station class mark (SCMp) The call termination enabled indicators (MOB_TERM_HOMEp,
MOB_TERM_FOR_SIDp, and MOB_TERM_FOR_NIDp)
Parameter-change registration is also performed when any of the following capabilities supported by the mobile station changes:
The band classes The power classes The rate sets The operating modes
Parameter-change registration is performed whenever there is no entry in the mobile station’s SID_NID_LISTs (see Zone Based Registration for details) that matches the (current, as being sensed by the MS) base station’s SID and NID.Parameter-change registration is independent of the roaming status of the mobile station.Whenever a parameter changes, the mobile station deletes all entries from SID_NID_LISTs.The initiating entity for parameter change registration is the MS, while it is the Base Station setting that determines as to "at the change of which parameters the MS needs to be registered". In other words, the MS follows the "directive" of the Network, and initiates a "Parameter Change Registration procedure" once it detects a change in any of the "parameters". At the change of which Parameters this should happen is also defined by the Network.
1. Ordered Registration
The MSC / VLR can command the mobile station to register by sending a Registration Request Order. Ordered registration is performed in the Mobile Station Order and Message Processing.
The controlling (and initiating) entity for ordered registration is the MSC / VLR.
2. Implicit Registration
Whenever an Origination Message or Page Response Message is sent, the base station can infer the location of the mobile station. This is considered an implicit registration.
In this type of registration, actually no (explicit) registration messages are exchanged either at the air interface or within the network. It’s only that the MSC/VLR comes to know the present location of the MS due to the call origination request by it or due to the response by it to any page message for a terminating call.
The process for implicit registration performed while MS is attempting to Originate a Call, can be shown in the Flow Chart form as follows:
3. Traffic Channel Registration
While a mobile station is assigned a Traffic Channel, the mobile station is notified about the fact that it is registered, through the "Mobile Station Registered Message".
4. User Zone Registration
User Zone registration is performed when the mobile station selects an active User Zone.
1. Registration Procedures on Network Side 1. IS-41 Signalling Message Flow for Registration
On the Registration attempt by the MS, the MSC/VLR sends a Registration Notification (REGNOT) message to the HLR. One of several (below-mentioned) possible results is returned (by the HLR, to the MSC/VLR) in the Registration Notification Return Result (regnot):
An indication that authorization is confirmed with an indication of the authorization duration (e.g., per call, eight hours, one day).
Item 1 along with the MS’s calling capabilities (i.e., profile information). Only the MS’s calling capabilities. An indication that authorization is denied with reason for denial (e.g., due
to an invalid serial number).
The detailed process of Registration at the HLR is given below:
1. Successful RegistrationNotification: Confirmed at the HLR
This operation scenario given below describes the RegistrationNotification operation when confirmed (i.e. i.e. successful) at the HLR.
a. The Serving MSC determines that a roaming MS is within its service area; the Serving MSC may detect the MS’s presence through autonomous registration, call origination, call termination (i.e., a page response following a call to the roamer port) or a service order. The Serving MSC sends a REGNOT to its VLR (generally an "internal communication, as MSC and VLR functions are typically always realised on a common hardware platform / system).
Parameters Usage Type
IDInfo: Set of identification parameters in REGNOT:
[MIN] Served MS MIN. R
[ESN] Served MS ESN. R
[MSCID] Serving MSC MSCID. R
[PC_SSN] Serving MSC PC_SSN. Include if SS7 carriage services are used.
O
[LocationAreaID] For paging served MS. Include if available. O
[SystemMyTypeCode] Serving MSC vendor identification. MBC
QUALCODE Type of qualification required. R
SYSACCTYPE Type of system access. R
TRANSCAP System's transaction capability R
TERMTYP Identifies the radio frequency interface standard supported by the associated MS
R
AVTYP Indicates MS is unavailable for normal call delivery, if applicable.
O
SMSADDR Temporary routing address of SMS subscriber, if applicable.
O
AuthError: Parameters included if authentication parameters were requested by the Serving MSC but not received from the MS:
O
[SystemCapabilities] Authentication capabilities of serving system.
[ReportType] Report of missing authentication parameters.
BORDACC Indicates that system access is in a border cell, as determined by local procedures.
O
AccessInfo: Subscriber’s access information. Included if system access is in a border cell. Includes:
O
[ReceivedSignalQuality] Raw received signal strength from MS for use in multiple access signal strength arbitration.
[ControlChannelData] Includes: DCC and CHNO of analog access channel for use in multiple access detection;CMAC for use in signal strength arbitration.
[SystemAccessData] Indicates the Serving MSC and cell site for use in multiple access detection.
b. The Serving VLR determines that either (a) the MS had previously registered with an MSC within the domain of the VLR but the MS has been reported (found to be, at this point in time) inactive by the VLR, (b) the MS is not known to the VLR, or (c) the requested information cannot be made available for the indicated MS.Under these conditions, the Serving VLR forwards the REGNOT (associated with the MS) to the HLR.Note: for the sake of brevity, and also since this aspect is not directly related to the subject of this document, it is not stated here EXPLICITELY how the VLR determines which HLR (of the many that may be there in a Network) to send this message to. This is a separate subject in itself, & is covered elsewhere (in some other document).
Parameters Usage Type
IDInfo: Set of identification parameters in REGNOT:
[MIN] Served MS MIN. R
[ESN] Served MS ESN. R
[MSCID] Serving MSC MSCID. R
[PC_SSN] Serving MSC PC_SSN. Include if SS7 carriage services are used.
O
[LocationAreaID] For paging served MS. Include if available. O
[SystemMyTypeCode] Serving MSC vendor identification. MBC
QUALCODE Type of qualification required. R
SYSACCTYPE Type of system access. R
TRANSCAP System's transaction capability R
TERMTYP Identifies the radio frequency interface standard supported by the associated MS
R
AVTYP Indicates MS is unavailable for normal call delivery, if applicable.
O
SMSADDR Temporary routing address of SMS subscriber, if applicable.
O
AuthError: Parameters included if authentication parameters were requested by the Serving MSC but not received from the MS:
O
[SystemCapabilities] Authentication capabilities of serving system.
[ReportType] Report of missing authentication parameters.
BORDACC Indicates that system access is in a border cell, as determined by local procedures.
O
AccessInfo: Subscriber’s access information. Included if system access is in a border cell. Includes:
O
[ReceivedSignalQuality] Raw received signal strength from MS for use in multiple access signal strength arbitration.
[ControlChannelData] Includes: DCC and CHNO of analog access channel for use in multiple access detection;CMAC for use in signal strength arbitration.
[SystemAccessData] Indicates the Serving MSC and cell site for use in multiple access detection.
[PC_SSN] Serving VLR PC_SSN. Include if SS7 carriage services are used.
O
[MYTYP] Serving VLR vendor identification. MBC
c. The HLR determines that authorization can be granted to the MS. It returns the requested information to the Serving VLR in the regnot.
Parameters Usage Type
AUTHPER Authorization confirmed indication with period of authorization. O
HLRID [MSCID] HLR MSCID to key MS record against for a subsequent UnreliableRoamerDataDirective.
R
MYTYP HLR vendor identification. MBC
Profile: Subscriber’s profile information. Include if profile requested in QUALCODE: O
[CallingFeaturesIndicator] Authorization and activity states for features.
[OriginationIndicator] Type of calls MS is allowed to originate.
[Digits(Restriction)] Selected leading digits or full Directory Number allowed for call origination as indicated in OriginationIndicator. Include if applicable.
[TerminationRestrictionCode] Type of calls MS is allowed to terminate.
[Digits(Carrier)] Indicates MS’s preferred IC, if applicable.
[RoutingDigits] Special routing instructions, if applicable.
[GeographicAuthorization] Include if applicable.
[AuthenticationCapability] Include if authentication of MS is required.
[DMH_AccountCodeDigits] Include if applicable.
[DMH_AlternateBillingDigits] Include if applicable.
[DMH_BillingDigits] Include if applicable.
[MobileDirectoryNumber] Include if applicable.
[MessageWaitingNotificationCount] Include if MessageWaitingNotificationType is Count Indication.
[MessageWaitingNotificationType] Include if Message Waiting Notification feature is active and an action is required.
[OriginationTriggers] Origination trigger points currently active for the subscriber. Include if applicable.
[PACAIndicator] Indicates the PACA permanent activation status and priority level assigned to the subscriber, if applicable.
[PreferredLanguageIndicator] Indicates the preferred language associated with the subscriber, if applicable.
[SMS_OriginationRestrictions] Defines the type of messages the MS is allowed to originate, if applicable.
[SPINIPIN] Indicates Subscriber's PIN, if applicable.
[SPINITriggers] SPINI trigger points currently active for the subscriber. Include if applicable.
[SMS_TerminationRestrictions] Defines the type of messages the MS is allowed to terminate, if applicable.
[TerminationTriggers] Termination trigger points currently active for the subscriber. Include if applicable.
d. The VLR forwards the regnot to the Serving MSC.
Parameters Usage Type
AUTHPER Authorization confirmed indication with period of authorization. O
HLRID [MSCID] HLR MSCID to key MS record against for a subsequent UnreliableRoamerDataDirective.
R
MYTYP VLR vendor identification. MBC
Profile: Subscriber’s profile information. Include if profile requested in QUALCODE:
O
[CallingFeaturesIndicator] Authorization and activity states for features.
[OriginationIndicator] Type of calls MS is allowed to originate.
[Digits(Restriction)] Selected leading digits or full Directory Number allowed for call origination as indicated in OriginationIndicator. Include if applicable.
[TerminationRestrictionCode] Type of calls MS is allowed to terminate.
[Digits(Carrier)] Indicates MS’s preferred IC, if applicable.
[RoutingDigits] Special routing instructions, if applicable.
[GeographicAuthorization] Include if applicable.
[AuthenticationCapability] Include if authentication of MS is required.
[DMH_AccountCodeDigits] Include if applicable.
[DMH_AlternateBillingDigits] Include if applicable.
[DMH_BillingDigits] Include if applicable.
[MobileDirectoryNumber] Include if applicable.
[MessageWaitingNotificationCount] Include if MessageWaitingNotificationType is Count Indication.
[MessageWaitingNotificationType] Include if Message Waiting Notification feature is active and an action is required.
[OriginationTriggers] Origination trigger points currently active for the subscriber. Include if applicable.
[PACAIndicator] Indicates the PACA permanent activation status and priority level assigned to the subscriber, if applicable.
[PreferredLanguageIndicator] Indicates the preferred language associated with the subscriber, if applicable.
[SMS_OriginationRestrictions] Defines the type of messages the MS is allowed to originate, if applicable.
[SPINIPIN] Indicates Subscriber's PIN, if applicable.
[SPINITriggers] SPINI trigger points currently active for the subscriber. Include if applicable.
[SMS_TerminationRestrictions] Defines the type of messages the MS is allowed to terminate, if applicable.
[TerminationTriggers] Termination trigger points currently active for the subscriber. Include if applicable.
1. Multiple Registrations in border area (Signal Strength Arbitration)
The following procedure elaborates the system behavior in case of multiple system access for registration.Let’s take an example that for a certain MS MSC1/VLR1 is the serving system. MSC2/VLR2 & MSC3/VLR3 are the neighboring systems who over heard the Registration Access by the MS to MSC1. Let us assume that, MSC2 received the best signal quality.
1. So, all the three systems send Registration Notification Invoke message (REGNOT) to HLR.
2. After receiving the first Registration Notification Invoke message, the HLR starts multiple access timer (typical Timer value is 3 seconds).
3. The HLR compares the signal strengths received from the three systems. It determines that the signal strength received from the MSC3/VLR3 is weaker than the best signal strength received.
4. Now, HLR sends the registration notification return response to MSC3/VLR3 with authorisation denied and ReceivedSignalQuality & ControlChannelData received from system2.
5. The HLR sends the Registration Cancellation Invoke (REGCANC) to the serving system with the ReceivedSignalQuality & ControlChannelData received from System 2 (with strongest signal) to the system1 (old serving system).
6. The MSC1/VLR1 determines that the signal quality received by it is lower than one received in REGCANC. So, it accepts the Registration Cancellation & sends the Registration Cancellation Return Response (regcanc) to the HLR. If, in case, the signal quality received by the system 1 would have been the best, then MSC1/VLR1 will send the Registration Cancellation Denied response to the HLR & continue to serve the MS. The HLR in turn should have sent the Registration Notification Result Response (regnot) with AuthorisationDenied to other systems.
7. The HLR sends the Registration Notification Return Response to system2 with qualification Period parameter & the subscriber profile included in it.
Note: Above mentioned mechanism of Signal Strength Arbitration is valid only for TDMA kind of networks. This mechanism is not required in CDMA networks. This is so, because, while the MS is sending any information to the Base Station, the information is spread using the PN (Pseudo Random Noise) Short Code (Short Code is 16 bit code and is used to uniquely identify each BTS out of the possible 216 BTSs). Thus, any message sent by an MS can be De-Spread by only one BTS (& thus Registration can happen only from one MSC to which the BTS is connected).