Research problem:

    Symbol timing estimation and resynchronization for cooperative communication systems


    Multiple-input-multiple-output (MIMO) systems have been demonstrated to be one of the most promising and potential candidates for the future wireless communications. However, limited by the cost and the size of equipment, the concept of distributed MIMO system has been advocated by many researchers, where the sharing of antennas among several single-antenna terminals to cooperatively transmit data is suggested.  It has been pointed out that with proper cooperative strategies, the same benefits of centralized MIMO systems can be achieved in a cooperative MIMO system. 

    So far, many results regarding cooperative communication systems have been obtained under the assumption of perfect synchronization among the users, which is generally very difficult to achieve due to the distributed nature. Analytical and numerical results on the performance degradation brought by timing errors in a cooperative system have been reported.  Furthermore, it is also found that if the timing errors are large, the benefit of cooperation would even vanish in terms of diversity gain and system capacity. All these results demonstrate that appropriate counter-measures to the asynchronous reception in distributed MIMO systems are absolutely necessary.

    In this work, we look at the problem of multiple symbol timing estimation at the destination, and more importantly how to compensate the multiple timing errors.  We separately investigated the decode-and-forward cooperative system and amplify-and-forward cooperative system, and proposed two general frameworks for resynchronization with and without feedback from destination, respectively.

Representative Publications:

  1. Xiao Li, Yik-Chung Wu and Erchin Serpedin, Timing Synchronization in Decode-and-Forward Cooperative Communication Systems,IEEE Trans. on Signal Processing, vol. 57, no. 4, pp. 1444-1455, Apr 09. [PDF]

  2. Xiao Li, Chengwen Xing, Yik-Chung Wu and S.C. Chan, Timing Estimation and Re-synchronization for Amplify-and-Forward Communication Systems,IEEE Trans. on Signal Processing, Vol. 58, no. 4, pp. 2218-2229, Apr 2010. [PDF]