A Limited Feedback SDMA for Downlink of Multiuser MIMO Communication System
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Research Article A Limited Feedback SDMA for Downlink of Multiuser MIMO Communication System Yongming Huang,1 Luxi Yang,1 and Ju Liu2 1 School 2 School
of Information Science and Engineering, Southeast University, Nanjing 210096, China of Information Science and Engineering, Shandong University, Jinan 250100, China
Correspondence should be addressed to Yongming Huang, [email protected] Received 14 February 2008; Accepted 13 August 2008 Recommended by Christoph F. Mecklenbr¨auker This paper proposes a limited feedback SDMA scheme of combining opportunistic scheduling and codebook-based multiuser precoding. A new systematic construction for SDMA codebook, which comprises a set of precoders for multiple simultaneously active users, is first presented. Different from conventional Grassmannian codebook, the proposed codebook is designed in terms of array processing and has a cluster-based structure, with each cluster generated using a perturbation method. In order to tackle the intractable interuser interference issue inhered in limited feedback SDMA, this paper further proposes two novel opportunistic scheduling algorithms, which are able to fully exploit the cluster structure of the proposed codebook. The first proposed algorithm schedules the simultaneous users and their preferred precoders in a successive way, and is implemented in a Markov-like fashion. The second proposed algorithm is capable of rapidly finding a group of channel-matching users along with their preferred precoders. Simulation results demonstrate that in sparse networks, the proposed SDMA exhibits a better throughput performance than the conventional limited feedback SDMA does, while both having a comparable feedback overhead. Copyright © 2008 Yongming Huang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1.
INTRODUCTION
Space division multiple access (SDMA) is capable of considerably improving the throughput of multiple antenna broadcast channels, in comparison with time division multiple access (TDMA). Thus, SDMA has been adopted by IEEE 802.20 and other standard bodies. Through multiuser precoding, SDMA enables base station to simultaneously communicate with multiple users using the same timefrequency resource. The optimal performance of SDMA can be achieved by combining dirty paper coding (DPC) [1] with appropriate user scheduling. However, DPC is infeasible since it is extremely computationally intensive, even some simplified versions of DPC, such as TomlinsonHarashima precoding [2–4], are still very difficult for implementation due to high computational complexity. In contrast, several low-complexity multiuser precoding techniques have been developed, including zero-forcing precoding [5], block diagonalized precoding [6], MMSE precoding [7], the generalized eigenvalue-based solutions [8] and the iterative algorithms [9], and so forth, which can
achieve a large portion
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