Diversity methods are used to improve the reliability of the communication between
transmitter and receiver. These methods use redundancy to reduce the errors in the
communication link. Apart from the conventional diversity methods, multiuser
diversity has an aim of maximizing the sum capacity of a multi-user system. To
benefit from multiuser diversity, the opportunistic scheduling method grants the
channel access to the user which has the best channel quality among all users.
Therefore, the cumulative sum of the information sent to all users, which is the sum
capacity, is maximized in the long term.
Although the opportunistic scheduling maximizes the sum capacity, it has some
drawbacks such as the feedback load growing with the number of users and the
problem of fairness for the users which may have lower channel quality than some
other users. In this thesis, these two issues are investigated for the broadcast channels.
Feedback quantization, which gives partial information on the channel state, is
studied to mitigate the feedback load with a goal of little loss in the sum capacity.
The thresholds for the finite feedback quantization are determined to provide fairness and to reduce the feedback load at the same time. To provide fairness, users are
grouped into clusters and thresholds are optimized for each cluster. A method is
proposed by extending the one given by Floren et. al. to solve the mentioned
problems and the proposed method is compared with some other scheduling methods
in the literature.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12609941/index.pdf |
| Date | 01 September 2008 |
| Creators | Soydan, Yusuf |
| Contributors | Candan, Cagatay |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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