MUROS vs VAMOS-difference between MUROS and VAMOS

This page on MUROS vs VAMOS describes difference between MUROS and VAMOS techniques used in GSM.The useful links to difference between various terms are provided here.

MUROS-Multi User Re-using One Slot

This technique helps to enhance capacity of data and voice services. In this MUROS technique an orthogonal subchannel is created where in 2 users use the same time slot with same ARFCN number (i.e. same frequency). In the MUROS concept 8 or more new TSCs have been introduced.

Hence with this enhancement, each cell have been assigned 2 or more TSCs(Training Sequence Codes) without the need of changing the RF frequency planning. Each GSM Base Station uses TSCs to assign 2 or more users on one single time slot.

In this assignment one BTS will be assigned with 2 TSCs viz. legacy TSC and new TSC. The receiver side will easily differentiate its own signal from the other MUROS partner based on cross co-relation method. In the uplink chain either STRIC or SIC or JD technique can be applied for interference cancellation. In the downlink chain, SAIC can be applied for interference cancellation.

The front end synchronization such as time offset estimation and correction, frequency offset estimation and correction as well as channel estimation and equalization is carried out using the respective TSC as assigned by the base station.

Following modulation schemes are supported in MUROS downlink side.
• Linear sum of two GMSK signals (having 90 degree phase separation)
• QPSK along with linear Gaussian filter
• QPSK along with RRC filter (with roll off of about 0.3)

VAMOS-Voice Services Over Adaptive Multi-User Orthogonal Subchannels

The technique VAMOS has been added in 3GPP release 9. This technique allows multiplexing of 2 users simultaneously on same resource(time slot,ARFCN,TDMA frame). This is applied to both the downlink as well as uplink in circuit switched domain(CS domain).

Following logical channels are used in VAMOS feature. •TCH/FS•TCH/HS•TCH/EFS•TCH/AFS•TCH/AHS•TCH/WFS
The associated control channels used in VAMOS are SACCH and FACCH.

There are 4 proposed techniques for VAMOS in GSM technology. The probable techniques among them are OSC, alpha-QPSK or Co-TCH. Refer VAMOS basics in GSM for more information.

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