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Investigation Of Limited Feedback And Precoding Technologies In Multiantenna Systems

Posted on:2012-04-06Degree:DoctorType:Dissertation
Country:ChinaCandidate:X M ChenFull Text:PDF
GTID:1118330332483546Subject:Communication and Information System
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Recently, wireless communication is developing with an unprecedented speed, with the goal of satisfying the demand of mobile users for various advanced wireless services, such as video, audio and multimedia entertainment. In order to break out the constraint of the scarcities of bandwidth and power on the further development of wireless communication, multiantenna technology is proposed to improve spectrum efficiency, enhance transmission reliability, or a tradeoff of both by exploiting its unique spatial degree of freedom. The limited feedback pre-coding technology based on multiantenna systems adapts the predetermined space-time signal to the channel state, so as to further improve the system performance. The crux of the design of the limited feedback precoding technology lies on how to convey the channel information as much as possible by using limited bandwidth and how to design the simple but powerful precoding method based on limited feedback information. This dissertation gives an intensive investiga-tion on the the design of feedback methods, the construction of precoding matrix, the reduction of feedback amount and joint optimization of various resources in distributed and co-located multiantenna systems, and proposes several novel strategies as listed as follows:For the design of quantization codebook based limited feedback precoding technology in distributed multiantenna systems, the characteristics of channel distribution of distributed multi-antenna system is first analyzed, and the challenges of codebook design is investigated in detail, so that a two-step codebook design method is proposed, which can achieve a tradeoff between system performance and implementation complexity. Then, by minimizing the upper bound of the average pairwise error probability of space-time signal, a power allocation strategy without requiring extra feedback information is derived, which can further improve the utility efficiency of feedback information. According to the temporal correlation, the variety of channel can be modeled as a finite-state discrete Markov process. Based on this model, a feedback reduction scheme by making use of sub-codebook without performance loss is derived. In addition, due to the nonidentical appearance probability of the channel states, other two modified feedback reduction schemes are obtained accordingly. Thereby, a full limited feedback precoding strat-egy including codebook design, codeword selection, power allocation and feedback reduction is tailored for the distributed multiantenna systems.For the design of channel angular domain parameters based limited feedback precoding technology in distributed multiantenna systems, first through analyzing the propagation charac-teristics of wireless signal from distributed antennas, the non-Kronecker channel models in terms of angular domain parameters, such as average angle of arrival, angular spread, normalized re-ceive antenna spacing and K-factor, are built for rayleigh and ricean fading channels, respec-tively. Based on the channel models and by minimizing the upper bound of average pairwise error probability of space-time signal, the relationship of channel angular domain parameters and the optimal precoding matrix is revealed, and an angular domain parameters based precod-ing matrix design method is proposed, which has the advantages of small feedback amount, low computation delay and high robustness. In order to further decrease the design complexity, by the asymptotical analysis of the upper bound of average pairwise error probability, two simple precoding matrix design methods at high and low SNR regions for rayleigh and ricean fading channels are derived. After investigating the effect of angular domain parameters on diversity order and coding gain, it is found that, under the same condition, the design method over ricean channel performs better than that over rayleigh channel, and the performance gain increases as the K-factor increases.For the design of QoS driven limited feedback precoding technology in co-located multi-antenna systems, both single user case and multiuser case are considered. In the former case, according to the theory of effective bandwidth, the intrinsic relationship between transmit power and feedback bandwidth when given the maximum delay constraint is released, so that the two scarce resources can be jointly optimized according to the system characteristics. Furthermore, the effect of channel estimation error on the performance is investigated in some detail and the responding joint optimization scheme is given. In the latter case, by combining rateless coding and multiuser transmission, two limited feedback precoding transmission schemes, including multibeam opportunistic beamforming and orthogonal space division multiplex access, are pre-sented and the switch threshold in terms of system parameters is gained. Then, via analyzing the relationship between the number of users and delay constraint, the maximum accessible num-ber of users when given delay requirement is derived. Finally, by maximizing the netput (the difference of system throughput and feedback amount), the optimal feedback thresholds for the two transmission schemes are derived. Only the user whose receive signal's quality is higher than the threshold are needed to convey its information, so that a proper balance between system performance and feedback amount can be achieved.
Keywords/Search Tags:Multiantenna system, limited feedback precoding, codebook design, channel angular domain parameter, non-Kronecker channel model, rateless coding, effective bandwidth theory
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