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Pre-coding Technology Based On Single-user Mimo Communication Systems

Posted on:2009-06-10Degree:MasterType:Thesis
Country:ChinaCandidate:J Z DuFull Text:PDF
GTID:2208360245961757Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
Motivated by the increasing demand for dara rate in wireless systems,a major effort is being made to study the use of multiple antennas.It is widely understood that in a fading environment,by using multiple antennas at both the transmitter and the receiver(MIMO channel),the performance of a wireless link can be greatly improved,both in terms of improving the reliability of the link and supporting a higher spectrum efficiency.As has been shown,when the channel state information is known to both the transmitter and the receiver,the capacity achievable is increasing linearly with the minium number of the transmitter antenna and the receiver antenna.When accurate channel state information at the transmitter(CSIT) is not available,the system capacity will be affected heavily.However,it is not too easy to get exact CSIT,because there are too many elements in operation,such as the fast change of the channel,the delay of propagation and the esmitting errors of the channel.When the channel changed not too fast,the statical information of the channel may be fixed,the statical information of the channel can be feed back to optimize the transmission strategy.Precoding is a technology of utilizing CSIT to optimize the transmission strategy,which is a research focus nowadays. In this dissertation,we consider the single user case and we show how the system can benefit by precoding with channel state information (perfect or statical) at the transmitter.Firstly,we will introduce the applying environment of MIMO technology,and the research status of MIMO.Then we will give a basic introduction of wireless channel,this is the foundation of MIMO research.In the 3rd chapter,we give the capacities of MIMO channel for single user based on CSIT available.In the topic of precoding with perfect CSIT,the performance is optimistic and can be used as an performance baseline. The optimal precoders under sum-power constraint and peak-power constraint are given. Based on different system performance measures, a unifying framework for the systematic design of linear MIMO transceivers is proposed.For most objective functions of performance measures are Schur-concave or Schur-convex functions,the precoding problem can be then reformulated within the powerful framework of convex optimization theory. The simulation results illustrate the performances of different precoders based on different objective functions.In the topic of precoding schemes with partial CSIT,we propose the concept of net-rate as a measure of the performance-signalling trade-off,and report some result regarding the computation of net-rate function to evaluate if feedback is suitable or not.Then we prove the codebook design problem under flat fade Rayleigh channel reduces to a well-known mathematical problem known as Grassmannian line packing and Grassmannian subspace packing. The simulation results indicate that the presented Grassmannian limited feedback beamforming shceme achieves almost the same average BER performance of the beamforming scheme with perfect CSIT with small feedback requirements.
Keywords/Search Tags:precoding, codebook design, convex optimization, grassmannian line packing, grassmannian subspace packing
PDF Full Text Request
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