Compressed Mode (CM)

[mounir34]

Hi guys what's the compressed mode ?

[Nyquist]

Hi.
Basicaly Compressed Mode in WCDMA is a way of opening a window in the NodeB-UE transmission link allowing the UE to measure in other frequency. This can be used in Handover procedures or Inter-RAT Mobility. There are several modes, one of them is to transmit data during half of the time by decreasing the spreading factor to half (SF/2).
I hope it helps.

[mounir34]

Compressed Mode (CM) makes it possiblefor a UE to make measurements on another frequency to allow Inter-Frequency Handover (IFHO) or Inter Radio Access Technology Handover (IRATHO). If a UE detects that the quality is poor on the existing WCDMA carrier it will inform the network by sending a measurement report.

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Thanks!

[smarty]

During inter-frequency handover the UE’s must be given time to make the necessary measurements on the different WCDMA carrier frequency. 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover). These slots can either be in the middle of the single frame or spread over two frames.

This compressed mode operation can be achieved in three different methods:
Decreasing the spreading factor by 2:1. This will increase the data rate so bits will get sent twice as fast.

Puncturing bits. This will remove various bits from the original data and hence reduce the amount of information that needs to be transmitted.

The higher layer scheduling could also be changed to use less timeslots for user traffic.

[aluruwaichi@yahoo.com]

Due to some UE incapability of measuring other frequencies while in Transmission, compressed mode procedure is required to achieve IRAT and Inter frequency HO.