ABSTRACT:Energy efficiency in cellular networks has been receiving significant attention in wireless communication, because of the importance in reducing the energy consumption and maintaining the profitability of networks, in addition it makes these networks "greener". In the traditional cellular architecture, the urban cell topography increases the capacity along with the coverage require the deployment of a large number of base stations (BSs). This approach is cost prohibitive and also increase the mobile station (MS) transmission power. An alternative, relaying techniques are expected to alleviate the coverage problem and reduce the MS transmission power. To propose a geometrical model for the energy efficient relay station (RS) placement that requires only a small number of characteristic distances and is to estimate the maximum cell coverage of a relay aided cell, given power constraints. This proposed method analyzes the path loss model based on RS to BS link and it compares both cell coverage and energy efficiency using Decode and Forward (DF) relaying schemes in line of sight conditions.

To achieve the multiuser diversity and cooperative diversity, a two source destination pair is considered for cooperative communication system. Hybrid Decode Amplify Forward (HDAF) Relaying Protocol improves the system performance by combining the merits of both Amplify Forward (AF) and Decode Forward (DF) protocols is used. The fast and efficient Parallel Shift Water Filling (SPWF) algorithm can minimize the total power, based on the outage probability constraint. In the conventional algorithms, the solution is obtained by an iterative binary searching and Lagrange Multiplier searching process. In contrast, PSWF Algorithm removes the iterative searching process. It executes the PSWF only once, and then directly calculates the final solution with the parallel shift property as an enabling mechanism. Numerical analysis is used to compare the various relaying protocols based on outage probability and Bit Error Rate. KEYWORDS:Cooperative communication system, HDAF Relaying Protocol, Outage Probability, PSWF Power Allocation.I. INTRODUCTIONIn mobile terminals, it is difficult to support multiple antennas due its limitations in size, cost, complexity, etc. The alternative approach to achieve spatial and cooperative diversity without multiple antennas is the cooperative communication system [1]. Spatial diversity is that several antenna elements separated in space. Cooperative diversity is that several cooperative multiple antenna elements separated in space. Advantages of Cooperative communication system are ease of implementation, good scalability, increased connectivity, better coverage, reduced operating power level etc. Cooperative communication system consists of three nodes, a) Source, which transmits the signal, b) Relay, which forwards its signal to destination by some relaying protocols, c) Destination, receives the signal from relay and source. Amplify and forward relay will amplify its signal and forward it to the destination. But the demerit here is the amplification of noise [2]. Decode and Forward relay will regenerate the original signal and passes the clean set of signals to destination. It provides clean data extraction. But the demerit of this is if the relay wrongly decodes the signal, the performance of the system is degraded [3]. These observations motivate a new signal forwarding scheme that combines the benefits from AF and DF, this scheme is called Hybrid Decode Amplify Forward (HDAF) relaying. The intuition behind this protocol is that, if the relay cannot decode the signal correctly or the link between the relay and source is not good enough, then the relay will amplify the signal and forward the amplified signal to destination. II. RELATED WORKThe relay will forward the reliable information to the destination by performing soft decoding and forward the reliable information to destination [4]. The Symbol Error Probability (SEP) of HDAF cooperative system has been analyzed [5]. HDAF protocol is the best relaying protocol when the quality of relay destination link is better than sour...