In the field of wireless communication, Energy efficiency is very important because of the expectation with wireless links to meet the increasing QoS demand. This results in increase of device power consumption. So we present an energy efficient scheduling using water filling algorithm with OFDMA technique for multiuser. Subcarrier allocation for a multiple access OFDM system is found out by th...

In this paper, we consider two-way orthogonal frequency division multiplexing (OFDM) relay channels, where the direct link between the two terminal nodes is too weak to be used for data transmission. The widely known per-subcarrier decode-and-forward (DF) relay strategy, treats each subcarrier as a separate channel, and performs independent channel coding over each subcarrier. We show that this...

Orthogonal frequency division multiple access (OFDMA), which is widely used in the wireless sensor networks, allows different users to obtain different subcarriers according to their subchannel gains. Therefore, how to assign subcarriers and power to different users to achieve a high system sum rate is an important research area in OFDMA systems. In this paper, the focus of study is on the rate...

In this paper, we formulate the resource allocation problem for secure communications in a single cell OFDMA network where a base station wants to communicate to the users which are spread over its coverage area while an adversary is present in the network. In our model, we assume that the adversary s an active attacker which is able to either eavesdrop on the information transmitted over the w...

This paper proposes an adaptive subcarrier and bit allocation technique for multiuser OFDM (Orthogonal Frequency Division Multiplexing) system based on genetic algorithm. The objective is to minimize the overall transmission power while ensuring the per user’s data rate and Bit Error Rate (BER) requirements. This has been achieved by developing a search algorithm based on genetic system. Simula...

In distributed antenna system (DAS), since the distances from the remote antenna units (RAUs) to the mobile are different, the transmitted power of pilot symbol in orthogonal frequency division multiplexing (OFDM) needs to be optimized to provide a reliable channel estimation for the purpose of coherent detection. In this paper, we present a novel pilot power allocation strategy for OFDM in DAS...