3. RR is a group of functions concerned with administration
of channels at Um.
Main RR procedures:
Power control
Channel quality monitoring
Handover
Frequency hopping
Discontinuous transmission
Timing advance.
4. Enables power adaptation of MS and BTS.
Main reasons for power control:
Saving MS battery Power
Improve CIR.
Can be enabled or disabled.
Performed separately for uplink and DL.
Measurements on UL and DL are sent to BSC every 480 ms.
Measurements in terms of:
Signal strength in dB.
Signal quality in BER.
5. MS Power (dBm)
Max. transmit power
Power increase step
Signal strength
measured at BTS
Upper threshold
Lower threshold
Distance
Power control
increase command
Distance
6. Handover Control
Automatic switching of a call from one TCH to another.
Can be within the cell or between cells.
Handover occurs on TCH when call is in speech stage.
Only started if power control is not helpful.
Unique feature of mobile network.
Reasons for intra-cell handover
1. reduction of co-channel interference.
2. Maintenance activity
3. Equipment failure
7. Handover types:
Inter cell handover
Involves change of carrier and BTS.
Intra-cell handover
Involves change of carrier in same cell.
9. Requirements for Handover
1. Execution speed
2. Reliability
3. Transparent to users (not aware)
4. Service-dependent (voice, data)
• No excessive HO
• No delayed HO
• No early HO
10. Criteria for Handover
BSC receives measurement data from BTS
and MS.
The MS measures downlink:
Signal strength (dBm)
Signal quality (BER)
Signal strength of 6 neighboring BTSs downlink
The BTS measures UL:
Signal strength received from MS.
Signal quality received from MS.
Distance between BTS and MS.
13. N-times retry
Multiple request for Handover
Handover queue
HO wait for a free channel.
Sub-rating algorithm
Full rate TCH is split into 2 half rate TCHs.
17. Mobility Management (MM)
o Main task of MM is to support mobility.
o MM activities include:
1. IMSI attach and detach.
2. Location update
3. Registration
4. Update HLR/VLR
5. TMSI re-allocation.
6. Authentication of MS.
18. Location Update in same MSC/VLR
If MS detects a change in LAI, it informs network
MSC/VLR check if it is a visitor
BTS
BSC
VLR
HLR
MSC
2
3
4
1
2
3
4
19. Location Update with New MSC/VLR
When MS enters into new LA, location update.
LA may belong to new MSC/VLR.
BTS
BSC
New
VLR
HLR
MSC
4
1
5
3
2
Old
VLR
4
20. Periodic Registration
o MS is forced to send registration periodically.
o If MS miss registration, the network marks
o it as detached.
o This occurs if MS is out of area.
o This avoids paging.
o Periodic registration has Ack.
o MS tries until it receives Ack.
21. IMSI Attach
o When MS is switched on, it performs attach.
BTS
BSC MSC/VLR
32
4
1
4
