Spectral re-harvesting for 4G networks: Through low-complexity VAMOS receiver design

With an insatiable demand for high speed data services over 4G, any technology that re-harvests legacy spectrum is extremely useful. Voice services over Adaptive Multi-user channels on One Slot (VAMOS) is a feature introduced by 3GPP to efficiently utilize the available spectrum by multiplexing two voice users in the same radio resource. In VAMOS, the multiplexed users are assigned different transmit powers and allocated on either of the quadrature sub-channels. Neither the information about the sub-channel power imbalance ratio nor the sub-channel allocated is explicitly transmitted, making the design of a low-complexity single antenna VAMOS receiver to be a significant challenge. In this paper, we propose a low-complexity multi-user detection based VAMOS receiver for power constrained single antenna handsets which meets all the test requirements for both VAMOS levels I and II specified by 3GPP. We compare our algorithm with a Mono Interference Cancellation based VAMOS receiver and show that the performance of the proposed algorithm is up to >4dB higher at 3GPP specified Carrier-to-interference ratios. The work in this paper is of importance in the design of a low-complexity VAMOS receiver which is suitable for both VAMOS I and II.