Analysis Of The Energy Efficiency In The Hierarchy Stock Of The Multi-Input Multi-Output Relay Networks

In wireless networks the demand for reliability, speed, flexibility, capacity and data rate become high, thus dealing with wireless medium’s issue become mandatory. Diversity techniques emerges as an effective method to deal with the issues related to the dynamic change in the channel conditions of the wireless medium, issues such as noise interference, poor liability and energy consumption. Cooperative communication benefit from the broadcast nature of the wireless medium to use the neighboring nodes as relays to create different path between the transmitter and receivers.Using cooperation among the nodes in a wireless network can achieve a number of crucial advantages such as diversity gain and the case that all paths fail is uncertain. Moreover, combining cooperative networks together with multi-input multi-output techniques (MIMO) have proved in many researches to provide benefits related to capacity, transmission range and reliability.However above researches and evaluations are considered in ideal model of negligible listening and computing power. In wireless distributed networks such as WSNs the power consumed in overhearing and processing may take a significant amount of the total consumed power. Furthermore, it is known that to achieve an improvement in the performance of the packet transmission between the source and the destination, there is an extra processing and consumed power at the relay and the destination. Hence there is a tradeoff between improving the packet transmission and optimizing the energy consumption.Moreover, the energy issues in MIMO systems becomes more significant since the circuit complexity of MIMO structures is much higher than that of single-input single output (SISO) structures and it is not clear whether MIMO systems are more energy-efficient than SISO systems due to the high circuit complexity associated with the MIMO structure.However, no attention has been taken to the energy consumption and energy efficiency estimation in wireless MIMO cooperative network especially from the aspect of packet transmission.Motivate by the above issue, in the first part of this Dissertation a sub-optimal relaying scheme (SBS-AF) was specifically proposed to provide the advantage of maximizing the energy efficiency. In SBS-AF the destination benefits from the full channel state information (CSI) sort all the potential nodes to be relays. According to their signal strength the destination discards the relay(s) under a certain threshold form the list, after listing all possibility, and then sub-optimal power allocation process is done to distribute the power between the source and the relays. Therefore, based on proposed SBS-AF scheme a better energy efficiency performance can be obtained since only the best CSI relays are chosen to forward the source transmission and thus less energy consumption with maximum diversity.Based on the above challenges the energy efficiency performance of SBS-AF cooperative scheme have been compared with fixed AF transmission schemes where only one either one relay or all of the relays are used for cooperation. A significant observation is formed that our selection technique shows considerably better energy efficiency performance compared to fixed AF relaying schemes by about1.461×104bit/J. More importantly, the proposed scheme attains full diversity order.Benefits from these observations, we further utilize SBS-AF more complicated cooperative system where multiple sources are transmitting simultaneously. In this network we develop a statically proportional fair scheduling (SPFS) to computing the optimal sources assignments according to the relays. Alongside the SBS-AF we observe the enhancement of energy efficiency performance. Therefore SBS-SPFS-AF is compared with the fixed relaying scheme as well as with SBS-AF and SPFS-AF, in which either one of the proposed algorithm is utilized alone.Lastly in the second part of this Dissertation we analyze the energy efficiency from the prospect of packet error rate because of its definition at the network level of the hierarchy stack makes it better to handle by the higher layers in the stack. We propose a relaying scheme where a single MIMO relay only forward when the source fail to transmit. We observe the energy efficiency performance as we compare it with the fixed AF relaying schemes. The results obtained revealed that our scheme can achieve higher energy efficiency than the other schemes.