Coding techniques for multicasting

We study some fundamental limits of multicasting in wireless systems and propose practical architectures that perform close to these limits. In Chapter 2, we study the scenario in which one transmitter with multiple antennas distributes a common message to a large number of users. For a system with a fixed number (L) of transmit antennas, we show that, as the number of users (K) becomes large, the rate of the worst user decreases as O(K-(1/L)). Thus having multiple antennas provides significant gains in the performance of multicasting system with slow fading. We propose a robust architecture for multicasting over block fading channels, using rateless erasure codes at the application layer. This architecture provides new insights into the cross layer interaction between the physical layer and the application layer. For systems with rich time diversity, we observe that it is better to exploit the time diversity using erasure codes at the application layer rather than be conservative and aim for high reliability at the physical layer. It is known that the spatial diversity gains are not significantly high in systems with rich time diversity. We take a step further and show that to realize these marginal gains one has to operate very close to the optimal operating point. Next, we study the problem of multicasting to multiple groups with a multiple antenna transmitter. The solution to this problem motivates us to study a multiuser generalization of the dirty paper coding problem. This generalization is interesting in its own right and is studied in detail in Chapter 3. The scenario we study is that of one sender and many receivers, all interested in a common message. There is additive interference on the channel of each receiver, which is known only to the sender.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Khisti, Ashish, 1979-

Advisor dc:contributor.advisor

• Gregory Wornell and Uri Erez.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/28546

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/28546