Research On Capacity And Outage Behavior In Wireless Cooperative Relay Networks

The broadcasting in wireless networks was considered to go against the wirelesstransmission. It is because the broadcasting leads to the interference. However the co-operative communication makes use of the broadcasting to improve the communicationquality. The adjacent terminal can overhear the transmission if a terminal transmitsdue to the broadcasting. Cooperative protocols efciently improve the transmissionrate and diversity gain in the cooperative scenarios. This attracts the wide attentionsfrom both the academia and the industrial communication in home and abroad. Thisdissertation studies the capacity and outage behavior in the cooperative wireless net-works. Some coding strategies are proposed based on the information theory and theprobability theory, and their capacities and outage probabilities are analyzed. Themain contributions of this dissertation are fve folds:(1) PNC makes use of the broadcasting to improve the transmission rate by reduc-ing the transmission slot of conveying information. The existing works on PNCemploy QAM systems without channel coding to show the error probabilitiesinstead of the achieved rate. This dissertation analyzes the transmission rateachieved by PNC in the bit interleaved coded modulation (BICM) system, andproposes joint network coding and channel coding low-complexity scheme withthe linear property of Turbo codes. The scheme can apply to the fading asym-metry channel by guaranteeing the nested QAM. From the theoretical analysesand simulation, PNC can approach the upper bound in the high SNR regime,and the joint network coding and channel coding scheme also approaches thecapacity of PNC.(2) It is suboptimal to use the joint network coding and the random channel cod-ing without the good structure in relay works. Considering the good structureof Lattice codes, this dissertation proposes cubic-coarse Lattice network codingscheme in the two way system to reduce the complexity by losing about0.25bits/transmission data rate. It is validated that Lattice codes can achieve the capacity gain over random codes by the theoretic analyses. However, the schemeapplies to the fading systems with feedback, guaranteeing the amplitudes of thetwo input channel at the relay and phase synchronized. This dissertation propos-es the AF-based Lattice codes in the fading system, which employs the modularoperation to reduce the received power at the relay. Therefore the AF-based Lat-tice codes with the low system requirement can have the larger amplify factorto improve the capacity without feedback. From the theoretical analyses, theAF-based Lattice codes achieve the best performance when the input channelsat the relay are diferent.(3) Butterfy networks are modeled as the scenario that two adjacent base stationscommunicate with their mobile users with the help of the relay, and their outagebehavior hasn’t been studied. Besides, many power and rate allocation schemesrequire complete channel state information, however these schemes can’t applyto some practical wireless scenarios, such as the channel capacity from receiversto transmitters is too small to feedback these channel state information. Thisdissertation analyzes the closed-form outage probabilities for OAF and NAFin butterfy networks, and proposes the power and rate allocation algorithmswith only statical channel knowledge to minimize the outage probabilities. It isvalidated that the derived outage probabilities approach results by Monte Carlosimulations in the high SNR regime and the power and rate allocation algorithmscan achieve the large performance gain.(4) The ANC conveys the received signals at the relay by amplifying without otherparticular proceeding such that is is studied widely in the literature. The exist-ing works on analyzing the outage probabilities of ANC are based on the twoway channel with two sources. However these results can’t extended to the moregeneral channels with the arbitrary number of sources. This dissertation consid-ers a Rayleigh-fading half-duplex system where multiple source-destination pairscommunicate with the help of a single relay. The relay preforms ANC to assistthe transmissions from the sources to destinations. We analyze the closed-formoutage probabilities of ANC and DMT in the high SNR regime. It is shown thatthe derived outage probabilities approach results by Monte Carlo simulations inthe high SNR regime. The ANC is shown to achieve the same DMT of the XORnetwork coding strategy with an ideal assumption that each destination nodecan reliably overhear the data from other sources.(5) It is difcult to obtain the exact achieved system rate and error probability, and thus approximating analysis of the achieved rate and error probability becomesan important tool. DMT is one of the most important performance metrics in thefading wireless systems due to characterizing both multiplexing gain (approxi-mating the achieved rate in the high SNR regime) and diversity (approximatingthe error probability in the high SNR regime). The existing researches on DMTin the two way channel consider the scenario that two sources transmit withthe same of data rate. However it isn’t practical. This dissertation shows theclosed-form DMT of OAF, ODF, NAF, NDF and DDF protocols in the two-waymultiple antennas system, assuming the transmission rates of the two sourcenodes are diferent. It is validated that1) NDF and NAF are always better thanODF and OAF respectively. It is because NDF and NAF use two time slots,but ODF and OAF with three time slots;2) DDF is the best protocol in the lowefciency in terms of DMT, and NAF with the interference cancel techniques isthe best in the high efciency. It is because DDF is required to recover infor-mation from the two sources such that the interference between the two sourcesleads to losing the system performance in terms of DMT.