VAMOS has been specified as a Rel-9 feature and was expected to theoretically double the voice capacity of GERAN
per BTS transceiver. Capacity gains of VAMOS have however been seen from system level simulations to vary
significantly depending on the frequency load of the network. In networks with relatively high frequency load the
possible system capacity increase brought by VAMOS could thus result in degraded call quality.
Call quality in the network may rely upon factors which were not modelled/covered in the MUROS study, such as radio
resource management and interference coordination/mitigation mechanisms. Hence it is desirable to explore
standardization ways in these and/or other possible areas to optimize the call quality of VAMOS networks.
The present document contains the results from the 3GPP study item on VAMOS Enhancements. This includes study of
the following aspects:
Objectives of the study.
Common assumptions for the evaluation of candidate techniques.
Candidate techniques including those that utilize network synchronization, and further those that use inter-cell
interference coordination/mitigation and inter-cell channel state sharing in and between BSS. A candidate
technique will support frequency hopping.
Evaluations of candidate techniques based on the objectives.
VAMOS enhancements will also investigate a new logical interface between BSSs in A/Gb mode which applies to
control plane only and can be utilised by VAMOS enhancement solutions, since no logical interface between BSSs in
A/Gb mode exists in current specifications.