 Electrical and Electronic Engineering  Research Publications
Electrical and Electronic Engineering  Research Publications
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ItemMaximizing SumRate via Relay Selection and Power Control in DualHop NetworksDayarathna, S ; Senanayake, R ; Evans, J (IEEE, 20220101)In this paper, we focus on the sumrate optimization problem in a general dualhop relay network by considering the joint relay selection and power control in the presence of interference. First, we propose a new relay selection algorithm which has better sumrate performance than the existing relay selection techniques. Then we combine relay selection and power control to propose a novel iterative algorithm based on the tight lower bound approximation which maximizes the achievable sumrate. We also prove that for the special case of twouser networks, binary power allocation is optimum for at least two transmitting nodes. Extensive numerical examples are used to compare the performance of the proposed algorithm and to illustrate the accuracy of the analysis.

ItemOptimal Routing for MultiUser MultiHop Relay Networks Via Dynamic ProgrammingDayarathna, S ; Senanayake, R ; Evans, J (IEEEINST ELECTRICAL ELECTRONICS ENGINEERS INC, 20220523)In this letter, we study the relay selection problem in multiuser, multihop relay networks with the objective of minimizing the network outage probability. When only one user is present, it is well known that the optimal relay selection problem can be solved efficiently via dynamic programming. This solution breaks down in the multiuser scenario due to dependence between users. We resolve this challenge using a novel relay aggregation approach. On the expanded trellis, dynamic programming can be used to solve the optimal relay selection problem with computational complexity linear in the number of hops. Numerical examples illustrate the efficient use of this algorithm for relay networks.

ItemSumRate Optimization in Flexible HalfDuplex Networks With Transmitter/Receiver SchedulingDayarathna, S ; Senanayake, R ; Evans, J (IEEEINST ELECTRICAL ELECTRONICS ENGINEERS INC, 20220701)In this paper, we focus on the problem of transmitter and receiver scheduling to maximize the achievable sumrate of a flexible halfduplex network where nodes have the flexibility to either transmit, receive or be silent in a given time slot. We consider a network with multiple transmitters and receivers where each transmitter has specific information it needs to send to a set of receiving nodes. First, we conduct some structural analysis and show that the achievable sumrate is maximized when each transmitter only transmits to a single receiver at a given time. Next, we consider one instance of the flexible network and by reducing the symmetric multiple receiver network to a single receiver network, we also show that the achievable sumrate is maximized when either one transmitter or all the transmitters transmit. In fact, there exists a unique received signaltonoise ratio at which the optimality changes from alltoone. Finally, we design a novel lowcost algorithm that gives a suboptimal solution to the achievable sumrate maximization problem in a flexible halfduplex network. We also provide a comprehensive comparison of the proposed algorithm with respect to existing resource allocation techniques, and observe that our proposed algorithm provides significant sumrate gains.

ItemReliability Characterization for SIMO Communication Systems With LowResolution Phase Quantization Under Rayleigh FadingGayan, S ; Senanayake, R ; Inaltekin, H ; Evans, J (IEEEINST ELECTRICAL ELECTRONICS ENGINEERS INC, 20210101)

ItemNo Preview AvailableDecentralized Relay Selection in MultiUser Multihop DecodeandForward Relay NetworksSenanayake, R ; Atapattu, S ; Evans, JS ; Smith, PJ (IEEEINST ELECTRICAL ELECTRONICS ENGINEERS INC, 20180501)

ItemLowResolution Quantization in Phase Modulated Systems: Optimum Detectors and Error Rate AnalysisGayan, S ; Senanayake, R ; Inaltekin, H ; Evans, J (Institute of Electrical and Electronics Engineers (IEEE), 20200720)This paper studies optimum detectors and error rate analysis for wireless systems with lowresolution quantizers in the presence of fading and noise. A universal lower bound on the average symbol error probability ( SEP ), correct for all M ary modulation schemes, is obtained when the number of quantization bits is not enough to resolve M signal points. In the special case of M ary phase shift keying ( M PSK), the maximum likelihood detector is derived. Utilizing the structure of the derived detector, a general average SEP expression for M PSK modulation with n bit quantization is obtained when the wireless channel is subject to fading with a circularlysymmetric distribution. For the Nakagami m fading, it is shown that a transceiver architecture with n bit quantization is asymptotically optimum in terms of communication reliability if n≥log2M+1 . That is, the decay exponent for the average SEP is the same and equal to m with infinitebit and n bit quantizers for n≥log2M+1 . On the other hand, it is only equal to 12 and 0 for n=log2M and n

ItemChemical Reactionsbased Detection Mechanism for Molecular CommunicationsCao, TN ; Jamali, V ; Wicke, W ; Yeoh, PL ; Zlatanov, N ; Evans, J ; Schober, R (IEEE, 202005)In molecular communications, the direct detection of signaling molecules may be challenging due to the lack of suitable sensors and interference from coexisting substances in the environment. Motivated by examples in nature, we investigate an indirect detection mechanism using chemical reactions between the signaling molecules and a molecular probe to produce an easytomeasure product at the receiver. The underlying reactiondiffusion equations that describe the concentrations of the reactant and product molecules in the system are nonlinear and coupled, and cannot be solved in closedform. To analyze these molecule concentrations, we develop an efficient iterative algorithm by discretizing the time variable and solving for the space variables in each time step. We also derive insightful closedform solutions for a special case. The accuracy of the proposed algorithm is verified by particlebased simulations. Our results show that the concentration of the product molecules has a similar characteristic over time as the concentration of the signaling molecules. We analyze the bit error rate (BER) for a threshold detector and highlight that significant improvements in the BER can be achieved by carefully choosing the molecular probe and optimizing the detection threshold.

ItemCentralized Scheduling with SumRate optimization in Flexible HalfDuplex NetworksDayarathna, S ; Razlighi, M ; Senanayake, R ; Zlatanov, N ; Evans, J (IEEE, 202005)In this paper, we focus on maximization of the instantaneous sumrate in flexible halfduplex networks, where nodes have the flexibility to choose to either transmit, receive or be silent in a given time slot. Since the corresponding optimization problem is NPhard, we design lowcost algorithms that give suboptimal solutions with good performance. We first consider two existing approximation techniques to simplify the sumrate optimization problem: arithmeticgeometric means inequality and another utilising the tight lower bound approximation. We then propose a novel pattern search algorithm that performs close to exhaustive search but with significantly lower complexity. Comparing the performance of the proposed algorithm with respect to existing resource allocation techniques, we observe that our proposed algorithm provides significant sumrate gains.

ItemBinary Power Optimality for Two Link FullDuplex NetworkDayarathna, S ; Senanayake, R ; Evans, J (IEEE, 202005)In this paper, we analyse the optimality of binary power allocation in a network that includes fullduplex communication links. Considering a network with four communicating nodes, two of them operating in halfduplex mode and the other two in fullduplex mode, we prove that binary power allocation is optimum for the fullduplex nodes when maximizing the sum rate. We also prove that, for halfduplex nodes binary power allocation is not optimum in general. However, for the two special cases, 1) the low signaltonoiseplusinterference (SINR) regime and, 2) the approximation by the arithmetic meangeometric mean inequality, binary power allocation is optimum for the approximated sum rate even for the halfduplex nodes. We further analyse a third special case using a symmetric network for which the optimum power allocation is binary, under a sufficient condition. Numerical examples are included to illustrate the accuracy of the results.

ItemTwoWay Communications via Reconfigurable Intelligent SurfaceAtapattu, S ; Fan, R ; Dharmawansa, P ; Wang, G ; Evans, J (IEEE, 20200619)The novel reconfigurable intelligent surface (RIS) is an emerging technology which facilitates high spectrum and energy efficiencies in Beyond 5G and 6G wireless communication applications. Against this backdrop, this paper investigates twoway communications via reconfigurable intelligent surfaces (RISs) where two users communicate through a common RIS. We assume that uplink and downlink communication channels between two users and the RIS can be reciprocal. We first obtain the optimal phase adjustment at the RIS. We then derive the exact outage probability and the average throughput in closedforms for singleelement RIS. To evaluate multipleelement RIS, we first introduce a gamma approximation to model a product of Rayleigh random variables, and then derive approximations for the outage probability and the average throughput. For large average signaltointerferenceplusnoise ratio (SINR) \rho, asymptotic analXsis also shows that the outage decreases at the rate (\log(\rho)/\rho) where L is the number of elements, whereas the throughput increases with the rate \log(\rho).