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The Opportunity Of The Wireless Broadcast Channel Beamforming Technology

Posted on:2010-01-11Degree:MasterType:Thesis
Country:ChinaCandidate:Y QingFull Text:PDF
GTID:2208360275483558Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
Information theory suggests that if both the transmitters and the receiver can track the fading channel, the optimal strategy to maximize the total system throughput is to allow only the user with the best channel to transmit at any time. A similar strategy is also optimal for the downlink. Opportunistic strategies of this type yield a system wide multiuser diversity gain: the more users in the system, the larger the gain, as there is more likely to be a user with a very strong channel. We have observed that the multiuser diversity gains depend on the distribution of channel fluctuations. However,the dynamic range of channel fluctuations may be small,Further, the channel may fade very slowly compared to the delay constraints of the application so that transmissions cannot wait until the channel reaches its peak.In this thesis, we discuss a technique, called opportunistic beamforming, in which channel fluctuation can be induced in situations artificially when the natural fading has small dynamic range and/or is slow.The main results are as follows:1. We study the performance of opportunistic beamforming in slow and fast fading environments,and compare the opportunistic beamforming technique with other proposed ways to use multiple transmit antennas.2. We focus on how to improve the performance of opportunistic beamforming by take advantage of temporal correlation and spatial correlation of the channel.3. We discuss techniques on how to quantification the feedback CSI information to keep Performance not degenerating in a limited feedback system.4. A novel route has been developed to modificate the opportunistic beamforming system when we concern about the QoS requirements of the users.
Keywords/Search Tags:multi-user diversity, opportunistic beamforming, MIMO, QoS, limited feedback
PDF Full Text Request
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