TCH Assignment: Reason & Solution

It’s a process of by which TCH is assigned to the MS. After the SD request MS gets TCH successfully and the call transfers to TCH it

means TCH assignment is successful. For the best KPI TCH assignment should tend to 100%. It degrades due to HW problems.

Reasons for TCH Assignment failure:

Hardware Fault(TRXs,Combiner,Duplexer,Cables) VSWR High Path Loss. Faulty TMA. High TCH Blocking. Loose connections. DR being used extensively

Solutions for removal of TCH Assignment:

Clear VSWR IF TRXs are faulty lock them and try to replace them soon to avoid blocking Path Imbalance clear. Connection from BTS to Antenna Connector connection Check TMA. Check Duplexer,Combiner,TRXs connections,Multicuppler etc. Check BOIA card. Check BB2F Card.

Reports for TCH Assignment:

ZEOL to check alarms 208 for path imbalance 196 for UL-DL interference ZAHP for Flick report

A5/1 Cipher Enhancement - SDCCH handover provides an additional security enhancement for the generally employed A5/1 Ciphering security mechanism and mitigates the risks associated with a potential “cracking” of the existing mechanism.To make A5/1 more secure an immediate intra-cell SDCCH handover mechanism is employed. That is, once the first ciphered message is received, for all A5/1 ciphered communications (excluding Emergency Calls) an intra-cell handover is performed to

another SDCCH channel.Before the SDCCH handover, that is before the ciphering is started, random data is sent to MS in System Info 5 messages. Broadcasting of correct information in System Info 5 messages is started only after the handover. Dynamic SDCCH can be used with this feature to reduce possible problems with SDCCH availability.

Parameter immediate SDCCH HO(ISIC) enabled is visible to an operator and its value can be changed only when the feature state of ‘A5/1 Cipher Enhancement – SDCCH HO’ is ON or OFF. Parameter immediate SDCCH HO enabled is not visible when feature state is OFF.