Tx-integer

Tx-integer

This parameter specifies the number of timeslots between the consecutive transmissions of channel request messages by an MS.

To reduce the collisions on the RACH and to improve the efficiency of the RACH, an access algorithm is defined in GSM Rec. 04.08. The algorithm specifies three parameters: Tx-integer (T for short), maximum number of retransmissions (RET), and S related to channel combination.

This parameter works with the configuration of the CCCH to determine the parameter S. The relations between this parameter and the configuration of the CCCH are as follows:

When this parameter is set to 3, 8, 14, or 50, S is 55 if the CCCH and SDCCH do not share a physical channel.

When this parameter is set to 3, 8, 14, or 50, S is 41 if the CCCH and SDCCH share a physical channel.

When this parameter is set to 4, 9, or 6, S is 76 if the CCCH and SDCCH do not share a physical channel.

When this parameter is set to 4, 9, or 6, S is 52 if the CCCH and SDCCH share a physical channel.

When this parameter is set to 5, 10, or 20, S is 109 if the CCCH and SDCCH do not share a physical channel.

When this parameter is set to 5, 10, or 20, S is 58 if the CCCH and SDCCH share a physical channel.

When this parameter is set to 6, 11, or 25, S is 163 if the CCCH and SDCCH do not share a physical channel.

When this parameter is set to 6, 11, or 25, S is 86 if the CCCH and SDCCH share a physical channel.

When this parameter is set to 7, 12, or 32, S is 217 if the CCCH and SDCCH do not share a physical channel.

When this parameter is set to 7, 12, or 32, S is 115 if the CCCH and SDCCH share a physical channel.

The timeslot for sending messages is a random value from the collection of {0, 1…, MAX(T, 8)-1}.

The number of timeslots (excluding the timeslot used to send messages) between two adjacent channel request messages is a random value from the collection of {S, S+1, …, S+T-1}.

When T increases, the interval between two adjacent channel requests increases, and RACH conflicts decrease.

When S increases, the interval between two adjacent channel request messages increases, and RACH conflicts decrease, thus improving the usage of AGCH and SDCCH.

The access time of the MS, however, is prolonged and the network performance is decreased when T and S increase. Under normal conditions, an appropriate T value should be used to ensure that S is as low as possible, and ensure that AGCH and SDCCH are not overloaded.

[3,4,5,6,7,8,9,10,11,12,14,16,20,25,32,50]

32

None

-

None

If the number of RACH conflicts in a cell is small, T should be set to a great value. If the number of RACH conflicts in a cell is large, T should be set to a small value. The increase in T and S prolongs the access time of an MS, thus affecting the access performance of the whole network. Therefore, appropriate values should be selected for T and S.

When the network traffic is heavy, the success rate of immediate assignment is low if the sum of S and T is low. Thus, the value of T should be properly adjusted to make the sum of S and T great.

When Abis interface use the satellite transmission,this parameter must be 32.

32

None

None

Parameters About Radio Resources

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