PERFORMANCE ANALYSIS OF THRESHOLD BASED RELAY SELECTION TECHNIQUE IN COOPERATIVE WIRELESS NETWORKS

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1 International Journal of Electronics and Communication Engineering & Technology (IJECET) Volume 7, Issue 1, Jan-Feb 2016, pp , Article ID: IJECET_07_01_012 Available online at Journal Impact Factor (2016): (Calculated by GISI) ISSN Print: and ISSN Online: IAEME Publication PERFORMANCE ANALYSIS OF THRESHOLD BASED RELAY SELECTION TECHNIQUE IN COOPERATIVE WIRELESS NETWORKS K.Shamganth and Dr.Sami Al-Ghnimi IBRA College of Technology, Oman Dr.Martin J Sibley University of Huddersfield, U.K ABSTRACT In this paper, threshold based relay selection schemes is investigated in amplify and forward method. And the new threshold based relay selection algorithm is proposed for single relay selection and the BER performance is analyzed. Proposed method is extended for multi-relay selection scheme and the BER performance of multi-relay is analyzed. Key words: Cooperative communications, relay selection, amplify and forward, Device to Device Communication, LTE-A. Cite this Article: K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley. Performance Analysis of Threshold Based Relay Selection Technique in Cooperative Wireless Networks. International Journal of Electronics and Communication Engineering & Technology, 7(1), 2016, pp INTRODUCTION Cooperative communication is one of the fastest growing research areas, and it will be the key enabling technology in LTE-Advanced standard. Device-to-Device (D2D) communication is used in addition to infrastructure based networks in LTE-Advanced Release 12 standard [1]. Table 1.1 shows the LTE D2D proximity scenarios. The key idea in user cooperation is resource sharing among multiple network nodes. Exploration of user cooperation leads to savings of overall network resources. In Cooperative communication wireless agents may increase their effective QoS via cooperation. A large amount of theoretical and practical work on relaying and cooperative transmission has been published since the early works by Vander Meulen[2],Cover editor@iaeme.com

2 K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley and El Gamal [3]. The relay channel was first introduced in the work of Vander Meulen [2]. In [3], capacity of the three-node network consisting of a source, destination and relay is analyzed. User cooperation is extensively analyzed by Sendonaris et al [4,5]. In this two-part paper, authors proposed a new form of spatial diversity, in which diversity gains are achieved via cooperation of mobile users. Part I in [4] describes the user cooperation strategy, while part II in [5] focuses on implementation issues and performance analysis. Nicholas Laneman et al in [6] develop and analyse low-complexity cooperative protocols that combat fading due to multipath propagation in wireless networks. This work reports several strategies employed by the cooperating radios, including fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes. An example of decode and forward signalling can be found in the work of Sendonaris et al [4,5] which is modified in [6] by a hybrid decode and forward method. Cooperative communication has the following advantages: Improve communication capacity Speed and performance increase Reduced battery consumption Extend network lifetime Expansion in the transmission coverage area Relay selection plays a vital role in cooperative networks. If the chosen relay is not the best relay then the whole communication will not take place from source node to destination node. Relay selection mechanisms proposed in the literature categorized as follows: Centralized Relay selection Distributed Relay selection A. Centralized Relay selection Systems with pre-defined infrastructure for example cellular networks, users communicate with a central base station. In this type of relay selection central base station collects and utilizes the required information to select one or more relays to each source-destination pair. B. Distributed Relay selection Systems such as ad-hoc networks which do not have centralized control, in this category each node individually determines whether to cooperate and whom to cooperate with according to the information exchanged between nodes [7]. In this paper Distributed Relay selection category is used for the following reasons: The distributed algorithm is usually sub-optimal, but it limits communication overhead and calculation complexity comparing it with centralized algorithm. Distributed algorithm is more applicable to networks such as ad-hoc network and wireless sensor network. Distributed Relay selection is again classified based on number of relay nodes to be selected to assist the source node in cooperative communication. They are: Single Relay selection (SRS) Multi-Relay selection (MRS) editor@iaeme.com

3 Performance Analysis of Threshold Based Relay Selection Technique in Cooperative Wireless Networks Each category has its advantages and disadvantages. For example using a SRS, the hardware at the receiver is simple and easy to implement. However, using multiple relay nodes can increase the multiplexing again of the system at the expense of complexity. Categorization of Distributed relay selection schemes developed for ad- hoc wireless network is discussed in [8]. In this paper threshold based relay selection is used due to the advantages compared to other relay selection schemes as highlighted below: Power consumption is the major problem in other relay selection techniques which is overcome by Threshold based relay selection technique. In this approach only the relays which have SNR above the predefined threshold in the S-R links will be in listening mode and all other relays will be in silent mode. It also increases spectral efficiency and reduction in the complexity of the system due to less number of channel estimation. The remainder of this paper is organized as follows: SectionII presents the review of threshold based relay selection scheme. In SectionIII, the system model of dual-hop Single relay and Multi-relay is described in detail. SectionIV provides the performance analysis of threshold based relay selection ection algorithm.. Simulation results were presented in SectionV. Finally, SectionVI concludes the paper. TABLE I. LTE Device-to-Device Proximity scenarios[1] Within network coverage (Intra-Inter-cell) Outside network coverage Partial network coverage Non-public safety use case Discovery Public safety use case Discovery, Communication Communication Communication 2. REVIEW OF THRESHOLD BASED RELAY SELECTION Kyu-Sung Hawang et al. [9] propose an suboptimal relay selection algorithm where a predetermined threshold is set both at the relay node and at the destination node and the node selection is performed only when the signal quality of either relay or destination node is below a predetermined threshold. In this work authors provide the closed-form expression of statistics of the output SNR and study the complexity of the proposed scheme. FurzanAtlayOnat et al. [10] proposed a threshold based relay selection protocol. In this protocol the relays are selected among those having received SNR higher than a threshold value. The relay selection is performed by the destination based on the editor@iaeme.com

4 K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley received SNRs at the destination during the last hop. Authors derived exact bit error rate of this protocol and it is shown that it achieves full diversity order. Selective relaying schemes were studied extensively by FurzanAtlayOnat et al. [11] based on signal to noise ratio (SNR) to maximize the end-to-end (e2e) bit-errorrate (BER) in cooperative digital relaying systems using BPSK modulation. In this work the approximations for the optimal threshold values that minimize the e2e BER and the resulting performance is derived analytically for BPSK modulation. HaoNiu et al. [12] studied a threshold-based single relay selection algorithm. A reasonable threshold value is set at each relay node, and the first relay with the instantaneous channel gain larger than the threshold will be selected to cooperate with the source. In this work exact and closed form expression for its outage probability is derived over independent, non-identically distributed (i.n.i.d) Rayleigh channels. W.PamSriwongpairat et al [13] proposes a threshold-selection relaying scheme, in which each relay decides whether to forward the source information by comparing the received signal power with a decision threshold. In this work, bit-error-rate (BER) performance analysis is provided for the proposed scheme with BPSK signals. Interesting result of this paper is that the effect of optimum threshold dominates that of optimum power allocation especially when the relay is close to the destination. Tianxi Liu et al [14] propose a simple threshold based hybrid relay selection (THS) scheme for cooperative communication over block fading channels. In this work a specific SNR threshold is designed in comparison with the instantaneous SNR to determine if the frame can be decoded correctly or not. The relays that decode correctly will choose decode-and-forward (DF) protocol and included in the DF relay group. The rest will employ amplify-and-forward (AF) protocol and be included in the AF relay group. Then among all the relays in the AF and DF relay groups, the one that realizes the maximum destination SNR will be finally selected as the optimal relay. Vo Nguyen QuocBao et al [15] investigate threshold based dual-hop relaying schemes in conjunction with partial relay selection in terms of outage probability and bit error probability. PrasannaHerath et al [16] proposed the distributed switch-and-examine combining with threshold-based relaying (DSEC-T). In this scheme, relay selection is performed in a similar fashion to switch-and-examine combining (SEC) considering the sourcerelay channel signal-to-noise ratio (SNR) in conjunction with threshold-based relaying. In particular, the same relay remains selected as long as its SNR. 3. PROPOSED RELAY SELECTION METHOD Step1: Source sends the signal to the destination and it is received by the nearby relays in the coverage region. Destination will provide the feedback to the source based on the BER for the source to destination path. If the BER falls below the threshold value then relay will be used by the source for forwarding the source information to the destination. Step2: Threshold SNR (γt) is fixed at the relay and destination node. Step3: If the received SNR at the destination γd<γt then apply relay selection technique. Step4: At the relay if received SNR is above threshold i.e, γri>γt (i=1,2,3,..n) then relay will be in active mode if this condition is not satisfied those relays will be in sleep mode editor@iaeme.com

5 Performance Analysis of Threshold Based Relay Selection Technique in Cooperative Wireless Networks Step5: Source will receive instantaneous channel state information (CSI) from the relays for Source to active relay path. Step6: Destination will receive instantaneous CSI between the active relay and destination. Step7: Relay will be selected based on the acceptable path gains between the Source- Relay and Relay-Destination. 4. SYSTEM MODEL A. Single-Relay based System Model We consider single relay forwards the source information to destination. Cooperation strategy can be modelled with two orthogonal phases in order to avoid interference between the two phases: Phase1: Source sends information to destination and the relay also receives the information. Phase2: Relay helps the source by forwarding or retransmitting the source information. The received signal at the relay in the phase 1 is given as: = h + (1) = h + (2) whereh and h are the path gain between the source and the ith relay, also between source to destination. n andn denotes the complex additive white Gaussian noise with zero-mean and variance N0. And x denotes the transmitted information symbol. During phase2 the relay with SNR value above the threshold level will amplify and forward the source information to the destination. In phase2, the relay amplifies the signal from the source and forwards it to the destination ideally equalize the effect of the channel fade between the source and relay. The relay does that by simply scaling the received signal by a factor that is inversely proportional to the received power = (3),! To calculate the mutual information between source and destination, we need to calculate the total instantaneous SNR at the destination [17]. The SNR at the destination is the sum of the SNR s from the source and relay links. SNR from the source link is given by " #, = h, $ (4)! SNR from the relay link can be calculated as follows: Received signal at the destination in phase 2 is given by:, = h, #, +, (5),! editor@iaeme.com

6 K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley whereh %, is the channel coefficient from the ith relay to destination. And n %, denotes the complex additive white gaussian noise between the relay and destination path. Substituting (1) in (4), we have P y, = h, ( Ph x+n )+n, Ph, $ +N ) P y, = h, Ph x+n, Ph, $ +N ) n,=../ 0,12 3! h, n +n, (6) Assume the noise terms and, are independent, the equivalent noise, is a zero-mean, complex guassian random variable with variance =4 ) 7,8,! +1: (7) where No is the (W/Hz) is the power spectral density of AWGN. Destination receives two copies through the source and relay link. Optimal technique that maximizes the overall SNR is the maximal ratio combiner (MRC). It requires a coherent detector that has knowledge of all channel coefficients. Also SNR at the output of MRC is equal to sum of the received SNR from both branches. The instantaneous SNR at the destination is given by [6] " =", + <, <,8 >= (8) <, <,8 = where", =,8! is the instantaneous SNR of source to destination link. ", =, is the instantaneous SNR of source to i th relay link. ", =,8!! is the instantaneous SNR of i th relay to destination link Assume Rayleigh fading between the One-way Relay (OWR) channel as shown: Source Relay Destination In the absence of interference over fading channel, the PDF?(")= = <@ ABC C@ " 0 (9) Where " =G["] The CDF of the SNR links is J(")=1 A BC C@ (10) The capacity for One way relay (OWR) for the link Source Relay Destination L= = $ MNO71+ <,8<, <,8 <,8 = : (11) editor@iaeme.com

7 Performance Analysis of Threshold Based Relay Selection Technique in Cooperative Wireless Networks 5. PERFORMANCE ANALYSIS A. Outage Performance Analysis The instantaneous mutual information for amplify and forward is given by [1] P QR = = $ log (1+",+", ) (12) P QR = 1 2 log (1+h, $ +?( h $,, h $, ) 4 ) 4 ) 4 ) where?(,) XY XY= The outage probability is obtained by averaging over the exponential channel gain distribution [1], as follows [P QR <[]=G,8,,,,,8 = 1 2 log (1+h, $ +?\ h $,, h $, ]<[ 4 ) 4 ) 4 ) At high SNR regions, the outage probability is given by: [P QR <[] _ `, $ $ +`, 2`, $ (`, $ `, 1)4 ) $ ) a_(2$ 6. SIMULATION RESULTS AND DISCUSSIONS To show the benefits of proposed relay selection scheme, Monte-Carlo simulations are provided in this section. For simplicity one-way relay selection is assumed. In Fig.1 and 2, the BER performance of proposed single-relay selection scheme is compared with theoretical AWGN, Rayleigh fading and direct transmission without relay between source and destination. Also equal power allocation constraint is assumed, i.e, PS=PR=P. Fig.2 investigates the BER performance for N=100 iterations. From Fig.1 and 2 it is clear that BER performance of proposed relay selection scheme is better than direct transmission without relay and the Rayleigh. Also proposed method BER performance is closer to theoretical AWGN. Fig.1 shows the performance of N=50 iterations and Fig.2 for N=100 iterations, the performance of the proposed method with a difference of 5 db with the theoretical results. Fig.3 presents the BER curves single-relay and multi-relay schemes. It is evident that increasing the number of relays also shows the increase in the performance compared to the direct transmission without relays and single-relay between source and destination nodes. In single-relay selection scheme only the relay with SNR above the threshold is selected for forwarding the source information. In case of two relays with threshold values above the threshold only one relay is selected in single relay proposed scheme. Furthermore increasing the number of relays also increases the performance gains, as shown in Fig.3, comparison of 3-relay scheme with singlerelay and direct transmission provides 5 db. Fig.4 investigates the performance analysis of proposed multi-relay selection. It is assumed that relays with SNR above the threshold level forwards the source information. It is shown in Fig.4 that proposed multi-relay selection scheme outperforms theoretical results. B$ a editor@iaeme.com

8 K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley Figure 1 BER versus SNR of Single-relay AF for N=50 Figure 2 BER versus SNR of Single-relay AF for N= editor@iaeme.com

9 Performance Analysis of Threshold Based Relay Selection Technique in Cooperative Wireless Networks Figure 3 BER comparison of Single relay and Multi-relay Figure 4 BER versus SNR of Multi-relay AF for N= CONCLUSION In this paper, we have analyzed the performance of threshold based relay selection with amplify and forward relaying for single-relay and multiple relays. Our results suggest that proposed single-relay scheme outperforms direct transmission without relays. Also increasing the number of relays provides considerable performance gains compared with single-relay AF technique. Improvement in BER performance is also observed from the results of multi-relay selection. REFERENCES [1] Rohde & Schwarz: White Paper 1MA232 LTE-Advanced (3GPP Rel.12) Technology Introduction, Jun [2] E.C.VanderMeulen, Three terminal Communication channels, Advanced Applied Probability 3(1), pp , editor@iaeme.com

10 K.Shamganth and Dr.Sami Al-Ghnimi and Dr.Martin J Sibley [3] T.M.Cover and A.A.ElGamal, Capacity theorems for the relay channel, IEEE Trans.I nform. Theory, vol.it-25, pp , Sept [4] A.Sendonaris, E.Erkip, and B.Aazhang, User cooperation diversity, Part I: System description, IEEE Trans.Commun.vol.51, pp , Nov [5] A.Sendonaris, E.Erkip, and B.Aazhang, User cooperation diversity, PartII: Implementation aspects and performance analysis, IEEE Trans.Commun.vol.51, pp , Nov [6] J.NicholasLaneman, Cooperative Diversity in Wireless Networks: Efficient protocols and Outage behavior, IEEE Trans. Information Theory, vol.50, pp , Dec [7] Ahmed S.ibrahim, Cooperative Communications with Relay-Selection: When to Cooperate and Whom to Cooperate With?, IEEE Trans. Wireless Commn.vol.7, pp ,july2008. [8] K.Shamganth, Dr.Martin Sibley, Cooperative MIMO based Cellular Networks: A Comprehensive Survey, IET Chennai 3 rd International Conference on Sustainable Energy and Intelligent Systems (SEISCON), Dec [Online]. Available: [9] Kyu-sung Hwang, Young-Chai Ko, An Efficient Relay Selection Algorithm for Cooperative Networks, IEEE 66 th Vehicular Technology Conference, pp.81-85,2007. [10] FurzanAtlayOnat, Threshold based relay selection in Cooperative Wireless Networks, IEEE-GLOBECOM, [11] FurzanAtlayOnat, Threshold Selection for SNR-based Selective Digital Relaying in Cooperative Wireless Networks, IEEE Transactions on Wireless Communications, vol.7,no.11, pp ,nov [12] HaoNiu, Performance analysis of Threshold based Relay selection algorithm in Wireless Networks, Scientific Research Communications & Networks, vol.2, pp.87-92, [13] W.PamSriwongpairat, Optimum Threshold-Selection Relaying for Decode-andforward Cooperation Protocol, WCNC, pp , [14] Tianxi Liu, A Threshold-Based Hybrid Relay Selection Scheme, IEEE Wireless Communications and Networking Conference Workshops (WCNCW), [15] Vo Nguyen QuocBao, Performance analysis of Threshold-based Relaying with Partial Relay Selection over Rayleigh Fading Channels, International Conference on Advanced Technologies for Communications (ATC), pp , Oct [16] PrasannaHerath, Distributed Switch-and-Examine combining with threshold based relaying, Australian Communication Theory Workshop (AusCTW), pp.13-18, [17] Gaurang Raval, Abhinav Shah and Madhuri Bhavsar. Optimization of Clustering Techniques Using Energy Thresholds in Wireless Sensor Networks. International Journal of Electronics and Communication Engineering & Technology, 4(7), 2013, pp [18] K.Shamganth, Dr.MartinSibley, Dr.SamiGhnimi A Novel Multi-hop Threshold based Relay Selection Scheme, International Journal of Advanced Research in Computer Science and Software Engineering, Vol.4, Issue.4, April [Online]. Available: editor@iaeme.com