Best Relay Selection Scheme in Wireless Cooperative Communication

Journal of Telecommunication Network (Jurnal Jaringan Telekomunikasi) Vol. 13, No.4 (2023) ‘ Best Relay Selection Scheme in Wireless Cooperative Communication Nurul Hidayati1, Mila Kusumawardani2, Putri Elfa Mas’udia3 1,2,3,4 Telecommunication Engineering Study Program, Department of Electrical Engineering, State Polytechnic of Malang, Malang City, 65141, Indonesia , , Abstract—In this research, the combination of the relay selection and network coding is used to measure the performance in LOS and NLOS condition over cooperative communication. The research aims are to select the best relay as assisted relay as well as to improve performance system. The research method used four nodes, two nodes as source and destination and two nodes as relays. The single relay selection is used to select best relay of several relays. Measurements are conducted by altering the positions of the relays to achieve optimal outcomes. The findings indicate that the relay with the lowest Bit Error Rate (BER) and the shortest distance is chosen. The study's outcomes, when measuring throughput, reveal that network coding throughput is 21.8% higher than that without network coding in Non-Line of Sight (NLOS) conditions. In Line of Sight (LOS) conditions, the throughput is increased by 23%. Keywords— Bit Error Rate, Relay Selection, Signal to Noise Ratio, Throughput, Wireless Communication. I. INTRODUCTION In the realm of wireless communication, signal fading emerges as a consequence of the multipath phenomenon, wherein information is transmitted from the transmitter to the receiver through various paths. Multipath fading is a type of signal interference that transpires when a signal travels over numerous pathways from the transmitter to the receiver [1]. Because of these diverse pathways, the signal intensity at the receiver varies, which might amplify or diminish the received signal [2]. Fading affects the performance of the communication system. Furthermore, more extensive the transmission distance, the greater the energy required at the transmitter. One convincing strategy for overcoming these issues is cooperative communication using relays in data transfer. Cooperative communication is used to enhance energy efficiency by employing relays between the transmitter and receiver, hence reducing transmission distance and minimizing transmission energy [3]. And a relay selection method can increase cooperative communication system efficiency [4][5]. Moreover, additional network coding may strengthen data security while also saving bandwidth [6-11]. Network coding is an approach in enhancing throughput, diminishing delays, and establishing stronger networks [3][12]. Prior research simulated the best relay selection approach, single relay selection amalgamated in network coding. The biggest SNR is utilised to pick the relay, which utilises the BER and throughput parameters to assess system performance. The simulation findings demonstrate that combining the optimal relay with network coding may boost throughput by 34% when compared to relay selection without network coding [5]. Other research has employed simulations to accelerate network capacity and performance by combining relay selection with network coding. The optimal relay is determined using SingleRelay Selection-Network Coding (S-RS-NC) and Dual-Relay Selection-Network Coding (D-RS-NC). When 2𝐸𝑠 > 𝐸𝑅 , the relay selection along with network coding approach performs better than relay selection without network coding. [8]. Younghui Li et al. conducted research on Relay Selection Simulation with Network Coding (RS-NC) and the Min Max approach in selecting the optimal relay verifying by Monte Carlo simulation. The goal of this research is to increase gearbox efficiency and system performance. The results revealed that the RS-NC scheme outperformed the RS-No-NC system. [9]. In accordance with this study, the DF (Decode and Forward) protocol was used to conduct a network coding simulation with relay selection [3]. The max min approach and the greatest SNR are used in the relay selection technique. The simulation use Monte Carlo [13-14]to validate the correctness of the mathematical calculations performed and the recommended diversity analysis [3]. This study simulates single relay selection and multiple relay selection with network coding [15] in wireless communication through MATLAB Software, by comparing throughput and Bit Error Rate (BER) as the performance analysis. II. METHOD A. System Overview In this study simulates relay selection for multiple nodes, single relay selection and dual relay selection combined with network coding, which is depicted in Figure. 1. The single relay selection approach is used to determine the best relay from a set of n-relays. Whereas, dual relay selection involves attempting to identify the two best relays from a number of several relays. Subsequently, both of them are combined with network coding to secure data transfer. The users consist of 𝑆1 as source node and 𝑆2 as destination node. Multiple relays are employed in this study. We assume QPSK as modulation method, flat fading with gaussian noise as well as Rayleigh channel in this research. The block diagram of the system is shown in Fig 2. 310 E-ISSN: 2654-6531 P- ISSN: 2407-0807 Journal of Telecommunication Network (Jurnal Jaringan Telekomunikasi) Vol. 13, No.4 (2023) Figure 1. Diagram Block of System Fig 1. depics that the system consists of three parts, transmitter, relay and receiver. Regarding on transmitter stages, there are random bit generation, encoding process, modulation, channel, demodulation and decoding. The process of generating random bits, encoding, modulation append preamble, upsample and upconvert. In generating random bits, the generation of information bits is random and equiprobable. The encoding process begins by encoding the bits of information that have been generated previously with a convolution code. In matlab use the "convenc" function. Bits are encoded using the convolution code method with trellis, employing a specific code rate. In modulation, the generated bits are mapped into symbols using the QPSK modulation technique with M = 4, so the number of bits per symbol (k) is 2. The modulation result is in the form of complex IQ (Inphase Quadrature) symbols. The row of symbols is added to the preamble. The creation of pulses and the upsampling process in Upsample involve passing through the Square Root Raised Cosine (SRRC) filter. During upconversion, the signal is elevated to a frequency of 5 MHz to prevent signal attenuation from the DC radio. At the relay node, the best relay selection process (single relay selection) occurs from the 2 relays used. After that, the network coding process is carried out for the information bits from node 1 and node 2. The information bits from the network coding results in the relay are transmitted to each node, according to the stages in Figure 1. And after arriving at nodes 1 and 2 (...truncated)