SDCCH blocking

[jason182]

What is the SDcch blocking causes and solutions?

Thank you

[xsdenied07]

What is the SDcch blocking causes and solutions?

Thank you

SDCCH Blocking is probably due to one or more reasons

1. No Access to SDCCH

2. Failure before Assignment of TCH.

3. High Paging Load

4. Incorrect or Inapproriate timer values

Optimization for tips :

High Paging Load

Irreguler paging distribution in location areas results in SDCCH Blocking. Higher paging load in certain location area mean higher location updates on SDCCH resulting in SDCCH Blocking.

TIPS :

A location area with a high paging load needs to be reduced in size to relieve SDCCH Blocking. A location area with low paging load need to be enlarged in size to reduced the overal number of location ares.

Incorrect or Inapproriate timer values

Timer rr_t3 111 sets the amount of time allowed to delay the deactivation of a traffic channel (TCH) after the disconnection of the main signaling link.

TIPS :

The suitable value for this timer is 1200 ms (max being 1500 ms). The timer will cause the BSS to wait before the channel in question is allocated another connection. A lower value of timer will result in higher capacity since the channel is held for less time before being released.

[coursekec]

good explanation..

[nevy_14]

SDCCH Blocking is probably due to one or more reasons

1. No Access to SDCCH

2. Failure before Assignment of TCH.

3. High Paging Load

4. Incorrect or Inapproriate timer values

Optimization for tips :

High Paging Load

Irreguler paging distribution in location areas results in SDCCH Blocking. Higher paging load in certain location area mean higher location updates on SDCCH resulting in SDCCH Blocking.

TIPS :

A location area with a high paging load needs to be reduced in size to relieve SDCCH Blocking. A location area with low paging load need to be enlarged in size to reduced the overal number of location ares.

Incorrect or Inapproriate timer values

Timer rr_t3 111 sets the amount of time allowed to delay the deactivation of a traffic channel (TCH) after the disconnection of the main signaling link.

TIPS :

The suitable value for this timer is 1200 ms (max being 1500 ms). The timer will cause the BSS to wait before the channel in question is allocated another connection. A lower value of timer will result in higher capacity since the channel is held for less time before being released.

what about failure before Assignment on TCH?
do you have any tips?

BR,
nevy_14

[xsdenied07]

what about failure before Assignment on TCH?
do you have any tips?

BR,
nevy_14

Upon completion of MS/BSC/MSC link established, MS issues Assignment Request to BSC, Requesting TCH Assignment to the dedicated MS. Subsequently, BSS will attempt to allocated free TCH for MS voice messaging. Once Assignment Command is received by MS, stating the availability of TCH for the MS, it will move to the dedicated TCH and responds with Assignment Complete. In turns, BSS will submit Assignment Complete to MSC as to complete the signal activity.

Case :

TCH Congestion

TIPS :

For TCH Congestion certain features can be enabled like TCH queuing , Directed Retry and Congestion Relief. In case of the TCH queuing feature is enable, MS will queue in the Original SDCCH , awaiting for the next available TCH. It is to be remainded that once Queuing timer expires. BSS will also terminates transactions, in which case, call setup is termed as unsuccessfull due to TCH Congestion. The same situation also applies in situation where Congestion Relief feature is enabled. In the case of Directed Retry feature is enabled, MS will perform Handover to TCH of another cell if a valid handover neighbor is detected. The best thing to do is to add more radios in the cell to remove congestion.

Interference analysis on a particular carier can be done through an optimization tools like Neptune. Once interfering frequencies are determind, the frequency plan can be cleaned from such frequencies.

[firstmaxim]

How about excess use of SMS in the location area. This could also cause congestion of SDCCH subchannels. Also, ensure that border cells, including airports have adequate SDCCH dimensioning in place.
Regards