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The use of MIMO networks in wireless communication results in increased data rate but leads to severe interference issues and power losses. Promising beamforming (BF) architecture with Conditional Time split-Energy Extraction (CT-EE) is proposed to maximize the Energy Efficiency while optimizing the Mean Square Error (MSE) and Achievable Sum Rate (ASR). A distributed BF system using Minimum Mean Square Error algorithm is jointly implemented at all cooperating nodes. Energy Extraction (EE) from RF signal at the relay nodes facilitates full connectivity among the users. The signal transmission and EE phases are jointly implemented using time-split architecture, without using fixed pre-assigned time slots. Time split from information decoding to EE phase is done only if the battery life is found to be critical. The paper investigates the scope of bypassing the EE phase after ensuring the required power level. The performance of the proposed architecture is compared with the conventional BF and existing EE methods in terms of MSE, ASR and energy efficiency. The proposed architecture is well suitable to establish uninterrupted connectivity between user nodes which are frequently used and have severe power drain-off issues as they can be a part of natural disaster like flood affected wireless networks.

A novel circularly polarized (CP), single-fed microstrip antenna on an electromagnetic band gap substrate (EBG) is presented. The antenna consists of stacked structure of almost square patches and an EBG substrate for the lower patch. The proposeddesign has a reduced antenna size= compared to theconventional C P microstrip antenna at a given oprating frequency and of lightweight. The impedance and axial ratio bandwidths are large and C P rad ation quality is excellent over the entire upper hemisphere. The antenna features about 1 ldBi gain. The proposed antenna is suitable for global positioning system (GPS) applications.

Multiple-Input Multiple-Output, Orthogonal Frequency Division Multiplexing (MIMO-OFDM) technique is a promising technique for the use in cognitive radio (CR) systems. As energy efficiency becomes a design goal for all communication systems, nowadays CR systems are designed so that energy efficiency is maximized. This paper proposes a power allocation technique with improved energy efficiency for MIMO-OFDM based CR with tolerable degradation at system capacity. The performance of proposed scheme is evaluated and compared with existing schemes.

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