The Design of Linear Space-Time Codes for Quasi-static Flat-fading Channels

dc.contributor.advisor Barry, John R.
dc.contributor.author Varadarajan, Badri en_US
dc.contributor.committeeMember Li, Geoffrey Ye
dc.contributor.committeeMember Stuber, Gordon L.
dc.contributor.department Electrical and Computer Engineering en_US
dc.date.accessioned 2005-03-02T22:19:59Z
dc.date.available 2005-03-02T22:19:59Z
dc.date.issued 2004-07-09 en_US
dc.description.abstract The reliability and data rate of wireless communication have traditionally been limited by the presence of multipath fading in wireless channels. However, dramatic performance improvements can be obtained by the use of multiple transmit and receive antennas. Specifically, multiple antennas increase reliability by providing diversity gain, namely greater immunity to deep channel fades. They also increase data rates by providing multiplexing gain, i.e., the ability to multiplex multiple symbols in one signaling interval. Harvesting the potential benefits of multiple antennas requires the use of specially designed space-time codes at the transmitter front-end. Space-time codes introduce redundancy in the transmitted signal across two dimensions, namely multiple transmit antennas and multiple signaling intervals. In this work, we focus on linear space-time codes, which linearly combine the real and imaginary parts of their complex inputs to obtain transmit vectors for multiple signaling intervals. We aim to design optimum linear space-time codes. Optimality metrics and design principles for space-time codes are shown to depend strongly on the codes' function in the overall transmitter architecture. We consider two cases, depending on whether or not the space-time code is complemented by a powerful outer error-control code. In the absence of an outer code, the multiplexing gain of a space-time code is measured by its rate, while its diversity gain is measured by its raw diversity order. To maximize multiplexing and diversity gains, the space-time code must have maximum possible rate and raw diversity order. We show that there is an infinite set of maximum-rate codes, almost all of which also have maximum raw diversity order. However, different codes in this set have different error rate for a given input alphabet and SNR. Therefore, we develop analytical and numerical optimization techniques to find the code in this set which has the minimum union bound on error rate. Simulation results indicate that optimized codes yield significantly lower error rates than unoptimized codes, at the same data rate and SNR. In a concatenated architecture, a powerful outer code introduces redundancy in the space-time code inputs, obtaining additional diversity. Thus, the raw diversity order of the space-time inner code is only a lower limit to the total diversity order of the concatenated transmitter. On the other hand, we show that the rate of the space-time code places an upper limit on the multiplexing ability of the concatenated architecture. We conclude that space-time inner codes should have maximum possible rate but need not have high raw diversity order. In particular, the serial-to-parallel converter, which introduces no redundancy at all, is a near-optimum space-time inner code. This claim is supported by simulation results. On the receiver side, we generalize the well known sphere decoder to develop new detection algorithms for stand-alone space-time codes. These new algorithms are extended to obtain efficient soft-output decoding algorithms for space-time inner codes. en_US
dc.description.degree Ph.D. en_US
dc.format.extent 1524722 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/5030
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Outage capacity en_US
dc.subject Fading
dc.subject Diversity
dc.subject Rate
dc.subject MIMO
dc.subject Space-time
dc.subject Multiplexing order
dc.subject Sphere decoder
dc.subject Tree-pruning
dc.subject Outage probability
dc.subject.lcsh Wireless communication systems en_US
dc.subject.lcsh Coding theory en_US
dc.subject.lcsh Radio Transmitters and transmission Fading en_US
dc.subject.lcsh Space and time en_US
dc.title The Design of Linear Space-Time Codes for Quasi-static Flat-fading Channels en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Barry, John R.
local.contributor.corporatename School of Electrical and Computer Engineering
local.contributor.corporatename College of Engineering
relation.isAdvisorOfPublication 85c8609c-9493-4eb5-9b86-d5ebdc5747bb
relation.isOrgUnitOfPublication 5b7adef2-447c-4270-b9fc-846bd76f80f2
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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