View of A REVIEW OF COOPERATIVE RELAYING PROTOCOLS

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Vol.03, Issue 09, Conference (IC-RASEM) Special Issue 01, September 2018 Available Online: www.ajeee.co.in/index.php/AJEEE

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A REVIEW OF COOPERATIVE RELAYING PROTOCOLS

Nitesh Tyagi Research Scholar

Electronics & Communication Department, SIRT, SAGE UNIVERSITY, Indore tyaginitesh94@gmail.com

Shivangini Morya Asst. Professor

Electronics & Communication Department, SIRT, SAGE UNIVERSITY, Indore shivangini.saxena@trubainstitute.ac.in

Abstract –With the rapid growth of mobile devices and applications, speed and connectivity requirements in wireless networks are increasing rapidly. There is evidence that cooperative communications can dramatically increase the spectral efficiency and the operability of transmissions between external nodes. The concept of co-operation in a wireless network is one of the most active research topics in telecommunications, with the aim of identifying cooperative strategies that would maximize the gains in spectral efficiency and in transmission power. To cooperate, the nodes of the network share their resources (energy, frequency band, etc.) to mutually improve their transmissions and receptions. In wireless networks with relays, relays are nodes dedicated to improving the quality of communication between source and destination nodes.We study, from a theoretical point of view, a cooperative scheme in which the relays, after an initial listening period, try to decode the source messages and start transmitting useful signals for those decoded correctly. These useful signals are the result of a joint channel-network coding. This paper presents a review of the relay selection techniques in cooperative communication framework.

Keywords – Cooperative Communication, MIMO, MISO, Relay Selection.

I. INTRODUCTION

Increased demand for wireless communications applications has generated a significant development of wireless networks, in particular several generations of cellular networks in voice and data resources. The radio equipment and wireless services evolve to become more efficient and less costly for its users.

Thanks to the work and studies of researchers and experts who understand the environment of the transmission channel and generally multi-user communications [1]. By cons, compared to wired communications, we begin to understand the fundamental performance limits of wireless networks and practical methods to approach [2]. Moreover, given their growing impact in society, the wireless communications remain an important research topic [3].

The cooperative communication is an interim solution [4-6]. It proposes to share the antennas of neighbouring nodes to create this diversity. By having a knowledge of the state of the channel, the nodes will lend each other antennas transmitting packets from their neighbours on higher quality channels.

This and promising technique can not only circumvent the problems of unstable

channels but also increase link capacity [7]. Historically, cooperatives techniques appeared at the physical layer and many proposals have been made in this direction [8]. However, in the upper layers, the inclusion of these cooperatives techniques is still a subject on which many studies must be conducted [9, 10 and 11].

The fundamental standard of cooperative communication is utilizing other communication devices to relay transmission. The source node broadcasts information to both the relay node and the destination node. The relay node then advances the transmission to the destination node. The source node views the transfer node as a virtual antenna, empowering MIMO frameworks to be utilized without adding physical antenna.

By utilizing the cooperative communication technique, the source node can discover relay nodes which have worthy channels to the destination node, use it to relay the transmission to the destination node, and expanding the dependability of the entire transmission.

By selecting relay nodes nearer to it, the source node can likewise spare battery power, since it does not need to transmit at high power and can utilize the relay

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2 devices’ energy to accomplish the transmission.

Since the source node in the cooperative communication technique relies on upon the relay nodes to forward the transmission, relay selection for the relay nodes get to be vital with a specific end goal to acquire ideal execution of the cooperative communication framework.

By picking the right nodes to relay the transmission, the framework can accomplish higher capacity by utilizing lower assets.

II. COOPERATIVE COMMUNICATION

In present era people grow-up to depend on wireless technology, interest for high data rate in wireless communication develops significantly more. This issue is brought on not just in light of expansion in the quantity of users who frequently use this technique, additionally due to the way that the data which must be transformed has likewise become altogether. Despite the fact that improvement in the wireless innovation has been rapid, some physical parameters are as yet restricting the utility of the wireless technique. In most of the cases, battery life, limited frequency band and severe fading channel are causes which have get to be difficulties for specialists to succeed [4].

Cooperative communication has turn into one of the famous research topics as the solution to the battery life issue and expanding the transmission limit and execution. Cooperative communication is a frame work wherever wireless mobiles can together convey their signals, hence attaining a number of substantial developments in communication for multi-path fading channel: enlarged rates for data communication, enhanced clarity and coherence for voice communications, expanded battery life and reduced transmit power [4].

The basic principle of cooperative communication is using other communication devices to relay transmission. Figure 1 shows the data broadcasting from source node to both the nodes i.e.; receiver node and relay node. The relay node then forwards the transmission to the end point (destination) node. The source node regards the relay node as a virtual antenna, enabling MIMO systems to be

used without having to add physical antenna.

Figure 1: Basic structure of cooperative communication [4]

Wireless channel has a characteristic that the data transmission of each user can be received by all other users and also the base station. In this manner, the data of a partner to the base station is able receive and re-transmit at a particular mobile, therefore offering support to the respective mobile in light of the fact that the two streams received by means of independent fading paths, the spatial diversity will offer an enhancement in overall reception, regardless of the possibility that we scale the powers (as is required by fairness) so that the general measure of power per data bit in the framework continues as before.

III. METHOD OF RELAY SELECTION

The key element in cooperative communication is the relay node. Its selection is a major challenge. A good relay using the source to effectively transmit its packets. However, a bad night relay at the network functioning and causes additional losses. Therefore, the design of a reliable selection mechanism is required.

The bandwidth is divided into orthogonal channels (in the time domain or frequency), assigned to nodes source / relay, to avoid problems of interference at the destination. So each node transmits in its own channel. Nodes must be able to process the signals received from partners. This is not possible for nodes in full-duplex (which emit and receive simultaneously on the same frequency band). Indeed, because of the attenuations due to fainting, the transmitted signal is typically 100 to 150 dB high that the received signal [11].

Source

node Destination

node

Relay node

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3 Therefore, nodes operant half-duplex are considered.

In Figure 2, inspired by [11], a comparison of the allocation of time slots between a transmission cooperative and non-cooperative transmission is presented. This allocation is a fair situation of the number of symbols transmitted between the two nodes to a common destination.

The transmission of information takes place in two time intervals. In the first interval, the destination receives X/2 symbols of the source node/relay1. In the second interval, the destination receives the X/2 symbols of the source node/relay2.

Figure 2: Comparison between a non- cooperative transmission and

transmission cooperative

In the case of non-cooperation, the symbols transmitted by each node are unique to them even. If the nodes cooperate, then the transmission is performed on 4 time intervals. During the first (and third) time interval, X/4 symbols specific to the source node/relay1 (source/relay2) are transmitted to the destination and the partner. During the second (and fourth) time interval, the source / relays2 node (source / relay1) transmits, after processing, the corresponding symbols to the partner (to the destination). The destination receives total symbols X whose X/2 to the source node/relay1 and X/2 for the source/relay2 node.

A first protocol for ad hoc networks is proposed by [11] in order to avoid the propagation of errors to the relay. Indeed, it intends to transmit only when the inter-user source/relay1-

source/relays2 is of good quality. That is to say, if the instant SNR of this channel is high, then the node, after processing, sends the message to his partner to the destination. By cons, if this channel is of very poor quality, it proceeds without cooperation and sends its information with a code repetition, or another reliable.

In [11], the author shows that the loss probability (outage probability) of relay selection is proportional to a high SNR (i.e._𝑆𝑁𝑅¹₂). Hence, the selection of relay offers a diversity gain of order 2, which is the maximum diversity gain for the case of two nodes source/relay.

IV. LITERATURE REVIEW OF RELAY

SELECTION TECHNIQUES

Relay selection simplifies signaling and avoids complex synchronization schemes.

Thus with careful design it can preserve the spatial diversity provided by the total number of relays in the network. The basic idea of relay selection is to allow the relay with the best channel conditions convey the signals. Since only one relay is working at each time slot, a very strict time and carrier synchronization among the relays is no longer needed.

Furthermore in relay selection transmission of one information bearing symbol is completed within two time slots, accordingly provides higher bandwidth efficiency than the repetition based cooperative strategy.

A Bletsas, A. Khisti, D. P. Reed and A. Lippman [12] have proposed best relay selection technique to improve diversity gain in slow fading environments. A distributed relay selection technique is developed depending on instantaneous channel conditions. Authors have presented theoretical analysis for outage probability and demonstrated that proposed scheme achieves same diversity-multiplexing tradeoff as compared to DSTBC Scheme.

A. Bletsas, H. Shin, M. Z. Win, and A. Lippman [13]have extended their work done in [12] to opportunistically select best suitable relay amongst a set of contender relaying nodes in cooperative AF and DF system under aggregate power constraint. Authors have found that decode-and-forward scheme with opportunistic relaying shows same outage bound as it has used with all potential relays. In AF scheme, opportunistic relaying is found to be more outage

Source / Relay 1 Transmits

Source / relay 2 receives

Source / Relay 2 Receives

Source / Relay 1 Transmits Source / Relay 1 transmits Source / Relay 2 transmits

X: number of symbols received at the destination

X/2 X/2

X/4 X/4 X/4 X/4

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4 optimal than multiple relay scheme constrained to limited channel knowledge.

A. Bletsas, A. Khisti and M. Z.

Win [14]have presented opportunistic relaying for cooperative wireless sensor network with packet level feedback and derived diversity-multiplexing tradeoff.

Authors have compared it with the performance of MISO zero-feedback system.

V. Mahinthan, L. Cai, J. W. Mark and X. Shen [15] have studied how to appropriately match users for two-user cooperative-diversity systems with both regenerative and non-regenerative relaying and optimal-power-allocation strategy. Authors have derived OPA strategies to minimize overall energy consumption of the system. They have developed non bipartite stable matching algorithm and demonstrated that the performance of their scheme is alike optimal maximum weighted (MW) matching algorithm while maintaining lesser computation complexity.

Simulation results shows that with the help of optimal power allocation and proposed matching algorithm 9-10 dB diversity gain can be achieved.

S. S. Ikki and M. H. Ahmed [16]

have considered cooperative AF scenario with direct and indirect transmission between source and destination. Since conventional relay system with M relays requires M+1 channel. To solve this problem best relay selection scheme is applied to cooperative network. In proposed scheme, relay with maximum SNR at destination node is selected to cooperate with source node; therefore proposed scheme only requires two channels for transmission. Simulation results are presented based on symbol error rate and outage probability.

A. Adinoyi, Y. Fan, H.

Yanikomeroglu, H. V. Poor, and F. Al- Shaalan [17] have derived close form expression for outage probability and system capacity for selection relaying scheme. Furthermore authors have also provided 𝜖 −outage capacity for selection relaying.

Y. Li, R. H. Y. Louie, and B.

Vucetic [18]havepresentedjoint network- coding and relay selection for two-way relay channels and derived exact BER expression for the proposed system.

Yinlong et al. [19]proposed an energy-efficient relay selection and power

allocation strategy subject to a total power constraint. This approach first selects the transmission mode according to the energy efficiency of the different transmission link, then analyze the energy efficiency of the system and presents the optimal number of the relay nodes and the best power distribution factors in broadcasting phase and the cooperative transmission phase.

N. Varshney, A Krishna and AK Jagannatham [20] discussed about decode and forward relay protocol, incorporated with STBC codes in single and multiple relays. The authors demonstrated that with proposed system model they achieved full diversity and achieved better BER. They derived the optimal source relay power allocation, with minimal decoding error, without compromising power budget. In multiple relay two relay is consider with single and multiphase both.

V. CONCLUSION

Cooperative communication is a new class of wireless communication techniques in which wireless nodes help each other relay information and realize spatial diversity advantages in a distributed manner. This new transmission technique promises significant performance gains in terms of link reliability, spectral efficiency, system capacity, and transmission range.

Analysis and design of cooperative communication wireless systems have been extensively studied over the last few years. The introduction and integration of cooperative communication in next generation wireless standards will lead to the design of an efficient and reliable fully-distributed wireless network.

However, there are various technical challenges and open issues to be resolved before this promising concept becomes an integral part of the modern wireless communication devices.

A common assumption in the literature on cooperative communications is the equal distribution of power among the cooperating nodes. Optimum power allocation is a key technique to realize the full potentials of relay-assisted transmission promised by the recent information. By exploiting the information about the location of cooperating nodes, we are able to demonstrate significant improvements in the system performance.

This paper discuss the previous work

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5 done against the relay selection for cooperative communication.

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