In Multiple-Input Multiple-Output (MIMO) broadcast channels, the multi-antenna
basestation transmits information to multiple non-cooperative mobile users simultaneously.
Among various transmission schemes, zero-forcing beamforming (ZFBF)
and random unitary beamforming (RUB) are of particular interest due to their low
implementation complexity and ability to explore the multiplexing gain provided by
multiple transmit antennas.
To investigate the effects of multiuser diversity on sum-rate performance, previous
studies of beamforming schemes in multiuser MIMO systems usually employ
asymptotical analysis. In this work, while assuming channel gain follows Rayleigh flat
fading, we study the sum-rate performance of ZFBF and RUB through exact mathematic
analysis. For this purpose, we derive the statistics of selected users's effective
channel gain, which enable us to calculate the sum rate accurately and efficiently.
With derived sum-rate expressions, we evaluate and compare the sum-rate performance
of MIMO broadcast channels with RUB and dual-transmit-antenna ZFBF. In addition, we apply this analytical method to study strategies that mitigate multiuser interference for RUB-based multiuser MIMO systems. The strategies we consider in the thesis include
• Reducing the number of served users at a time. We present a new user scheduling
scheme, which imposes a threshold On user's SINR for feedback load reduction
and only activates those beams that are requested by feedback users.
• Exploiting receive diversity. When receivers use more than one antennas, we
evaluate the sum-rate performance gain offered by selection combining (SC) and
optimum combining (OC) schemes, respectively.
In addition to beamforming techniques, we study the symbol error rate (SER)
performance of MIMO broadcast channels with vector perturbation (VP) precoding
and quantized channel feedback. Based. on the established equivalent relations in
terms of minimum mean square error (MMSE) and SER between quantized and
perfect channel feedback cases, we investigate the tradeoff between feedback load and
achievable diversity gain. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3299 |
| Date | 25 May 2011 |
| Creators | Lu, Peng |
| Contributors | Yang, Hong-Chuan |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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