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Paging Performance Affecting Radio Parameters

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T3113 There are a few things to consider here: The TX value is to spread the transmission of the UL request from MS. The timer T3120 is

expired and MS transmits again till the parameter MAXRET (Maximum retransmission). T3120 is stopped after an immediate Assignment command and T3101 is started and

simultaneously T3113 is also running at the MSC end The Timer T3113 is stopped after getting a paging response (SABM) from MS and T3101 is

started when the Immediate Assignment Command is sent. During this call setup procedure

both T3113 and T3101 is running

  Now when we change the value of TX from 10 to 32 then for the first Channel request the MS

will have 109 RACH slots (500 ms) and if the value is 32 the MS will have 217 RACH slots (1

Sec). Now the retransmission of the channel request will depend on the MAXRET value thus

considering the value currently i.e 4 the MS will have MAXRET+1 channel requests. The time

difference for the two would look like the below table

With the MAXRET=4 and TX=32, it would take ~6 Secs therefore the timer T3113 should not expire before the Paging response if the value is 7 Secs , but this is only considering that all MAXRET+1 Channel requests are required to access network. In good RF conditions the retransmissions should not be highWith even First Page timer change to 5 Secs the TX value of 10 will not have any issue (3.3 Secs for RACH access), only with TX 32 there would be a problem of timer expiry before the MS accesses the system with Retransmission taking into account

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Impact of T3113 and TX changeBSRST10 has TX value 32 for all cellsThe hourly comparison of 13th Feb with 11 and 12 shows that there is degradation in RASR

On the radio side the degradation in RASR is more visible than on Core as the timer is changed only for 1 MSC

The Counter TOTPAG i.e. total incoming paging mesaages from MSC has increased by 30% for BSC BSRST10 where TX values for all cells are 32

A longer monitoring period required to make a conclusion for the Core PSR performance after timer change and TX value on radio as 32

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Hourly PSR for BSRST10The Hourly PSR for the BSC BSRST10 does not show any change

The PSR is as per the trend of 11th and 12th feb for the BSC

BSRST10 has LAI 14110 and 14140, PSR for the two LAIs shows no degradation and is in conformity with the normal trend

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Paging groups

There are two main parameters that determine the number of paging groups in a cell (besides

BCCHTYPE). The two parameters are AGBLK and MFRMS: AGBLK: This parameter determines how many of the paging blocks per multi-frame are reserved for the

AGCH. MFRMS: is the multi-frame interval and is defined as the transmission interval of paging messages to the

same paging group. Number of paging group is subject to the setting of MFRMS and AGBLK. The formula to calculate the

number of paging group is as below: Combined BCCH/SDCCH cells: Number of paging groups = (3 - AGBLK) * MFRMS

Non combined BCCH/SDCCH cells: Number of paging groups = (9 - AGBLK) * MFRMS

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Parameters

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Paging Response Upon receipt of a paging request message and if access to the network is allowed, the

addressed MS shall initiate within 0.5 s the immediate assignment procedure. The

establishment of the main signaling link is then initiated by use of an SABM with

information field containing the PAGING RESPONSE message Upon receipt of the PAGING RESPONSE message the network stops timer

PAGTIMERFRST1LA If timer PAGTIMERFRST1LA (PAGTIMEFRSTGLOB) expires and a PAGING RESPONSE

message have not been received, the network may repeat the paging request message

and start timer PAGREP1LA

Before going further in this report, we need to introduce one aspect which is closely

related to the paging. It’s the Random Access.

Random Access When the paged MS receives a Paging Request message it responds by sending a

Channel Request message, thereby requesting a signaling channel for call set-up. The

Channel Request message is sent on the Random Access Channel (RACH) and consists of

8 information bits: a random number (5 bits) and an establish cause (3 bits). In GSM

specifications phase 2, the number of bits used to establish cause can be 3 through 6.

Accordingly, the random number will be described using 5 down to 2 bits. The establish

cause can be: · Answer to page · Originating call · Location updating · Emergency call · Others, for example IMSI detach, SMS, supplementary services management

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Drawback for setting paging time low

The paging messages have to queue in the BTS paging queue

and the maximum queuing time is 5 seconds before the

paging messages are discarded. If the paging response time

is set too low, 4 seconds for example, those paging messages

in the BTS paging queue will never have a chance to send the

response back to the MSC. In addition, MSC will send out the

repeated paging once there is no response from MS for the

1st paging sent. So, we can actually maximize the possibility

of getting the successful paging response by extending the

paging response timers. On the other hand, paging load due

to unnecessary repeated page can be minimized too.

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