Bhaskar Ramamurthi

In this paper, we propose a simple diversity-four, two-antenna, two-tone, space-frequency code that combines modulation and coding with knowledge of reduced channel state information at the transmitter. This can find effective application in broadband wireless systems employing MIMO-OFDM. We compare the performance of the proposed code with other diversity-four codes that employ varying amounts of feedback. We show that this code provides an efficient trade-off between performance and feedback rate, which is very modest, while retaining implementation simplicity. © 2007 IEEE.

The performance in the downlink of a reuse 1 : 1 cellular wireless system is severely degraded due to the interference originating from adjacent cell sites. Even the spectral efficiency gains due to MIMO vanish for cell-edge users who are interference limited. Cooperative MIMO, which involves coordination amongst base stations serving adjacent cell-sites, is a promising technique to address the co-channel interference problem. In this paper, we study cooperation in the downlink of an interference channel. The basestations cooperate amongst themselves to arrive separately at precoding strategies which improve the signal-to-interference-and-noise ratio of the cell-edge users and hence the throughput. We propose a distributed algorithm that independently determines the precoder which mitigates the interference to the neighboring cell edge users without compromising on the in-cell performance. This algorithm requires only modest levels of on-air-feedback and information exchange among the basestations on the backhaul networks. ©2010 IEEE.