Limited Feedback for Temporally Correlated Channels
In the limited feedback literature, the block fading assumption is commonly made to simplify analysis. Such assumption for the channel is pessimistic since channel temporal correlation often exists and can be used for reducing feedback rates. On the other hand, the block fading assumption hinders the analysis of feedback delay, which exists in a practical system due to sources such as signal processing, propagation and protocol delays. The drawbacks of block fading assumption motivated us to develop a framework for analyzing a limited feedback system for a temporally correlated channel. In particular, this frame work addresses the feedback rate and delay. The novelty of the framework lies in the modeling of quantized CSI using a Markov chain (see figure) and its use in deriving a set of analytical results. Specifically, the feedback rate, the feedback compression method, the downlink capacity with feedback delay, and the exponential decay rate of the capacity gain caused by feedback delay are analyzed. The proposed framework is useful for computing the required feedback rate and evaluating the impact of feedback delay. This framework is applicable for any typical limited feedback system having a temporally-correlated channel and employing adaptive transmission such as beamforming, precoding and adaptive modulation.
Related Publications and Preprints:
 K. Huang, B. Mondal, R. W. Heath, Jr., and J. G. Andrews, “Limited Feedback for Temporally-Correlated Channels: Feedback Rate and Delay,” submitted to the IEEE Trans. on Info. Theory, March 2006. Also available onArXiv.
 K. Huang, B. Mondal, R. W. Heath, Jr., and J. G. Andrews, “Effect of Feedback Delay on Multi-Antenna Limited Feedback for Temporally-Correlated Channels,” accepted to Proc. of IEEE Global Telecommunications Conf., Nov. 27 – Dec. 1, San Francisco, CA, USA.
 K. Huang, B. Mondal, R. W. Heath, Jr., and J. G. Andrews, “Multi-Antenna Limited Feedback for Temporally-Correlated Channels: Feedback Compression,” accepted to Proc. of IEEE Global Telecommunications Conf., Nov. 27 – Dec. 1, San Francisco, CA, USA.
 K. Huang, B. Mondal, R. W. Heath, Jr., and J. G. Andrews, “Markov Models for Limited Feedback MIMO Systems“, Proc. of the IEEE Int. Conf. on Acoustics, Speech, and Signal Proc., vol. 4, pp. IV-9-IV-12, Toulouse, France, May 14-19, 2006.