Performance Analysis And Optimization Of Full-duplex Cooperative Communication Systems

The maturity of self-interference cancellation(SIC)promotes the development of in-band full-duplex(IBFD)communication.IBFD communication enables concurrent transmission and receipt of wireless signal,which turns the traditional notion of spectrum access.Therefore,IBFD communication has been considered as a promising solution to the contradiction between explosive growth of wireless traffic and deficient spectrum resource.The combination of IBFD communication and cooperative network is able to improve spectral efficiency,reduce transmission latency,resolve the hidden terminal and enhance the physical layer security.However,IBFD communication causes self-interference(SI)and inter-node interference which degrade the transmission reliability.In the context of non-ideal SIC,this paper investigates the reliability of IBFD cooperative networks.The main contents and contributions are summarized as follows:1)For the three-node cooperative network consisting of two IBFD source nodes and one half-duplex(HD)destination node,the error performance of distributed Alamouti space-time code is studied.At first,a two-phase full rate transmission protocol is proposed.In phase 1,each source node broadcasts their own message while receiving the signal from the other source node.In phase 2,the source nodes amplify and forward the received signal according to the Alamouti space-time coding rule.Assuming the destination node is equipped with maximum-likelihood detector,the pair-wise error probability(PEP)is derived.Due to the absence of closed-form expression of exact PEP,we derived its tight upper bound in high transmit power regime.Theoretical results indicate that distributed Alamouti space-time code can achieve full diversity in ideal residual SI scenario.The improvement of SIC enhances the achievability of diversity gain and improves the coding gain.Simulation results show that the considered IBFD cooperative network outperforms its traditional counterparts in the sense of error probability.2)For a cooperative network with a pair of HD source and destination nodes and two IBFD relay nodes,a novel distributed trellis space-time code is proposed.In the light of simultaneous transmission and receipt of IBFD relays,inter-relay interference(IRI)may degrade the decoding performance at the destination node.In contrast to the existing researches,we treat IRI as information exchange between the relays and construct distributed space-time code,named as “Inter-Relay Auto-Coding”(IRAC),with the help of amplify-and-forward(AF)cooperative protocol.Since the source message has been retransmitted multiple times,the equivalent interference plus noise at the destination node behaves non-static and correlated.In addition,the equivalent end-to-end relay channels are coupled.We use the worst-case interference-plus-noise approximation to circumvent the non-stationary and correlation.And two auxiliary lemmas are proved to demonstrate the independence of equivalent end-to-end relay channels.Theoretical results indicate that IRAC achieves full diversity and full rate,and the diversity gain is always achievable.The coding gain can be advanced by suppressing SI,lengthening source message and proper power allocation.Simulation results show that IRAC has better error performance comparing with HD two-relay protocol.3)For a three-node IBFD two-way relaying(TWR)network,the error probability is investigated under the assumption that the relay has more efficient SIC than the user nodes.Different from HD TWR network,IBFD user nodes can establish direct path to support non-orthogonal transmission,thus cooperative diversity can be achieved.Since relay node has processing delay,the expected symbol at the user nodes are overlapped.Therefore,the user node should jointly decode all received signals to maintain acceptable error performance.In addition,the cooperative mode of the relay changes with the length of the user message.The delayed and overlapped source message is equivalent to a special case of distributed truncated linear Toeplitz space-time block code(DTLT-STBC).Partial fraction decomposition and dominant balance methods are used to derive the asymptotic expressions of PEP under different relaying mode.Theoretical results indicate that the error performance DTLT-STBC only depends on the SIC efficiency at the user nodes,and full diversity can be achieved asymptotically.To guarantee the achievability of diversity gain,the full-diversity precoder is proposed.Simulation results show that well-cancelled SI,non-orthogonal cooperative protocol and full-diversity precoder make the IBFD TWR network superior to its HD counterpart.4)The performance of full-duplex cooperative device-to-device(D2D)communication is analysed,meanwhile the power allocation schemes are investigated.A single-cell network is considered,where a full-duplex cellular user assits a pair of half-duplex D2 D user without direct link due to path-loss or heavy shadowing.The D2 D user pair underlays the uplink channel.Non-orthogonal multiple access(NOMA)is adopted to support concurrent uplink and cooperative D2 D communication.Specifically,the cellular user superposes and broadcasts the uplink and D2 D data,and the D2 D receiver iteratively decodes the desired signal by successive interference cancellation.By investigating the optimal power allocation scheme on the Pareto boundary,the achievable rate region of the considered network is discussed.The joint outage probability of the cellular uplink and cooperative D2 D link is derived to measure the communication reliability,of which the asymptotic behavior is analysed in the high transmit power region.Based on the performance analysis,the power allocation strategy of the cellular and D2 D users are studied.Since the achievable rates of the cellular uplink and cooperative D2 D link cannot be simultaneously maximized,the fairness issue between them should be considered.In this thesis,the optimal power allocation with the consideration of max-min fairness is inverstigated,which is proved to be quasi-concave and have unique solution.The power allocation strategy to minimize the outage probability is also considered.Due to the intractability of the joint outage probability expression,a tight upper bound is first derived to relax the original optimization problem,therefore,a sub-optimal power allocation scheme is obtained.The simulation results confirm the theoretical analysis and the advantages of the proposed power allocation schemes.