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GSM Timers Network Side(BTS)

This page covers timers used in GSM on network side(BTS) which include T3101, T3103, T3105, T3107, T3109, T3111, T3113, T3115, T3121, T3123, T3141, T3151, T3153, T3155 and T3157.

Timer Function/value
T3101 The timer starts at the allocation of channel using immediate assignment message.
At the seizure of channels by mobile subscriber the timer is stopped.
The timer value is set by network taking into consideration so that it will be higher than max. time for L2 establishment attempt.
T3103 The timer starts when handover message is sent by mobile.
It stops when mobile correctly captures the newly assigned channel.
Timer value > max. transmission time of handover command+T3124 timer value+max. duration to establish data link in multiframe mode.
T3105 This timer is used for the repetition of the PHYSICAL INFORMATION message during the handover procedure.
Its value is network dependent. This timer may be set to such a low value that the message is in fact continuously transmitted.
T3107 This timer is started by the sending of an ASSIGNMENT COMMAND or a DTM ASSIGNMENT COMMAND message and is normally stopped when the MS has correctly seized the new RR channels.
Its purpose is to release the new channels (and, in the case of Enhanced DTM CS establishment, the old PS resources) if the MS is lost and, except when used for Enhanced DTM CS Establishment, to keep the old channel sufficiently long for the MS to be able to return to the previous old channels.Its value is network dependent.
It could be higher than the maximum transmission time of the ASSIGNMENT COMMAND message plus twice the maximum duration of an attempt to establish a data link multiframe mode.
T3109 Starts at the lower layer failure detection by network.
Used for channel release procedure. Purpose is to release the channels when communication is lost.
Its value is network dependent. Its value should be large enough to ensure that the MS detects a radio link failure.
T3111 This timer is used to delay the channel de-activation after disconnection of signalling link.
It allows time for repetition of the disconnection.
Time value = Value of timer T3110
T3113 This timer is started when the network has sent a PAGING REQUEST message and is stopped when the network has received the PAGING RESPONSE message.
Its value is network dependent.The value could allow for repetitions of the Channel Request message and the requirements associated with T3101.
T3115 This timer is used for the repetition of the VGCS UPLINK GRANT message during the uplink access procedure or priority uplink request procedure.
Its value is network dependent.This timer may be set to such a low value that the message is in fact continuously transmitted.
T3121 This timer is started by the sending of an INTER SYSTEM TO UTRAN HANDOVER message.
The timer stops after mobile seizes UTRAN channels.
Its value is network dependent.
T3123 This timer is started by the sending of an INTER SYSTEM TO CDMA2000 HANDOVER message.
It is normally stopped when the MS has correctly seized the CDMA2000 channel(s).
Value=network dependent
T3141 This timer is started when a temporary block flow is allocated with an IMMEDIATE ASSIGNMENT message during a Packet Access Procedure.
Stops when MS seizes TBF.
The timer value is set by the network.
T3151 This timer is used by the network to supervise the periodic transmission of the UPLINK BUSY message on the FACCH of the voice group call channel.
Its value is network dependent.
T3153 This timer is used by the network to supervise the periodic transmission of the VGCS ADDITIONAL INFORMATION message on the SACCH of the voice group call channel.
Its value is network dependent.
T3155 In a network supporting validation of Priority Uplink Requests, the timer T3155 supervises the broadcast of a new token after a valid Priority Uplink Request has been received.
If a Priority Uplink Request is received, and the token matches the token in the BSS then the request is accepted, the token is invalidated and T3155 is started. On T3155 expiry a new token, and the priority of the accepted request, shall be sent in the UPLINK BUSY message on the FACCH of the voice group call channels.
The T3155 timer should be set to a value that allows other service subscribers who sent a Priority Uplink Request at the same time as the one accepted by the network, to be back on the voice group call channel, in order to receive the new token.
The default value for T3155 is 500ms.
T3157 In a network supporting validation of Priority Uplink Requests, the timer T3157 supervises an additional validity period for an unused (old) token. When T3151 (supervising the periodic UPLINK BUSY) expires a new token is sent in the UPLINK BUSY message on the FACCH of the voice group call channels and timer T3157 is started. If a Priority Uplink Request is received before T3157 expires and the token matches either token in the BSS (old or new), the request is considered to be valid, both tokens in the BSS are invalidated and T3157 is stopped. If T3157 expires (i.e. no valid Priority Uplink Request has been received within T3157 seconds) the old token is invalidated.
The value of timer T3157 is operator specific. The value chosen should allow for the reception of requests from service subscribers, who have left the group call channel before receipt of the UPLINK BUSY message with the new token.
Its default value is 1s.

RELATED LINKS

General GSM Timers
GSM Timers Mobile Side

RF and Wireless Terminologies


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