Performance Analysis of MIMO Relaying Channels’ Cooperative Diversity for Mobile Networks Nafis Imtiaz Zaman 1 , Kazi Md. Abdullah Al Mamun 2 , Abu Moen Mohammad Salah Uddin 3 , Triantafyllos Kanakis 4 Midway School of Engineering, University of Greenwich, UK 1,3,4 Dept. of Information and Communication Engineering, Yeungnam University, South Korea 2 nafis2007@hotmail.com 1 , kazi@ynu.ac.kr 2 , moen_24@hotmail.com 3 , t.kankis@gre.ac.uk 4 Abstract—Relay networks achieve high performance by utilizing cooperation between nodes which can classified as multi-hop networks and cooperative MIMO relaying networks. Cooperative diversity is a transmission technique to overcome fading, multipath and inter-channel interference. As an important part of "spatial diversity" systems, cooperative diversity involving multi hop data relays is a solution to improve propagation performance, expanding coverage and enhancing system capacity in such wireless environments. In a cooperative diversity system, the "third party" mobile devices acting as relays to help the main transmission link for improving the performance such as bit error rate (BER), data rate, coverage. This paper is a study of analyzing the system performance for MIMO-Relaying MIMO in different wireless channel and results show the better performance of cooperative communication. Keywords- Cooperative Diversity, MIMO, Relay, AWGN, Rayleigh, Mobile Networks I. INTRODUCTION Cooperative Relaying is regarded as a promising technique for next generation cellular wireless systems and is being considered by several standardization groups (e.g., IEEE802.16 Task Groups j and m). In cooperative relaying, a node on a multihop path from a source to a destination can receive and process the signals transmitted by several predecessors. [1] An important building block in this field is the multiple- input multiple output (MIMO) relay channel. Such a channel consists of a source, a relay and a destination terminal, each equipped with multiple antennas.[2] Space or multiple-antenna diversity techniques are particularly attractive as they can be readily combined with other forms of diversity [3]. Multi hop wireless networks have the ability to achieve spatial diversity gains by allowing nodes in the network to cooperatively retransmit messages for neighboring nodes [4]. This form of spatial diversity is known as cooperative diversity. By sending signals that carry the same information through different paths, multiple independently faded replicas of the data symbol can be obtained at the receiver end and more reliable reception is achieved [13]. Cooperation leads to increased code rates at the same transmit power. Due to increase of channel code rate for cooperative diversity the spectral efficiency improves [6]. Fig. 1. Cooperative Communication Scenario The key advantage of cooperation is that it allows a network of relatively simple, inexpensive, single-antenna devices to achieve many of the eminent advantages of physical antenna arrays. In addition, cooperative diversity can be readily combined with other forms of diversity, such as temporal and frequency diversity, to further utilize the available degrees of freedom in the wireless propagation environment and improve overall network performance [2][7]. The basic ideas behind relay channel model were examined by Cover and EI Gamal [13]. The work of Cover and EI Gamal was based on three node network consisting of a source, a destination and a relay which analyzed the capacity. More generally, Cover and EI Gamal develop lower bounds on capacity, achievable rates through different random coding scheme such as facilitation, cooperation and observation [9]. To achieve better performance and capacity over conventional single antenna system multiple input-multiple output systems (MIMO) are considered as a key technology in wireless communication system. In recent times the concept of cooperative communication exploits the potential MIMO gains on a distributed scale. In cooperative communication the phases of transmission and processing are distributed by different nodes. Different nodes can share the resources. Both the multiplexing capability and spatial diversity can be implemented by the exploitation of MIMO schemes in a distributed way. MIMO basic advantages are multiple antennas receive more signal and transmit more signal. Multiple receivers not only increases the amount of receive power, but also reduces multipath problems by combining the received signals for each frequency component separately.