Feedback Reduction in MIMO Broadcast Channel
Date Issued
2013
Date
2013
Author(s)
Li, Jin-Hao
Abstract
In multiuser multiple-input multiple-output (MIMO) downlink broadcast channel, data rate can be tremendously increased by adding antennas and by scheduling algorithm at the base station (BS). When users are located in the broadcast area, the users receive the same data which is broadcasted from the BS. For the multiuser MIMO system with Mt transmit antennas and K users equipped with Mr antennas, the full multiplexing gain Mt can be achieved by using space-division multiple access schemes or zero-forcing beamforming. Moreover, in a large user regime K >> Mt, the sum rate
grows like Mt log logK due to multiuser diversity. However, all these results are based on the assumptions of full channel state information (CSI) at the transmitter, thus, the feedback load linearly increases with number of users
and number of antennas. On the other hand, CSI feedback is also very important in terms of proper selection of modulation and coding for achieving reliable transmission. Thus the aggregate feedback load in a network is large.
The main contributions of thesis are proposing feedback reduction strategies considering different applications, such as multiuser MIMO broadcast channel and multicast channel, and scheduling algorithms to avoid waste of
radio resource used for CSI feedback. Through analysis, we derive the feedback reduction methods which use multiple thresholds which are obtained through the concept of order statistics to exploit the scheduling mechanism. Simulations show that the feedback load can be reduced dramatically and
almost full sum rate performance can be achieved in broadcast channel. For multicast scenario, the feedback load can be reduced dramatically and number of decoded user is almost the same as the full CSI case. Moreover, a new
scheduling method with multi-threshold model is proposed and the relations among the fairness across users, the feedback load and the sum rate in heterogeneous Rayleigh fading channel are also investigated.
Subjects
降低迴授；多用戶分散增益；束波形成技術
Type
thesis
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