The paper studies the capacity of the OFDM and the OFDMA relay networks. Two relay schemes, amplify-and-forward (AF) relay and decode-and-forward (DF) relay are analyzed and compared for both OFDM and OFDMA relay networks. A relay node selection algorithm is proposed for OFDMA relay network. Numerical results show that under small relay power transmission, AF outperforms DF while the opposite i...

Existing work on placing additional relay nodes in wireless sensor networks to improve network connectivity typically assumes homogeneous wireless sensor nodes with an identical transmission radius. In compare, this paper addresses the problem of deploying relay nodes to provide fault tolerance with higher network connectivity in heterogeneous wireless sensor networks, where sensor nodes have d...

Rate adaptation is an effective approach to achieve high spectrum efficiency under varying channel condition, especially for wireless communication. This paper proposes rate adaptation at receiver for wireless relay system. In this scheme, source node uses a new modulation technology, called random projections code (RPC), to achieve rate adaptation. Both relay node and destination node decode t...

It is known that relay assisted wireless transmission in a triplet, which consists of a source node, intermediate relay node and a destination node results in less power consumption than direct transmission between the source and destination pair. However, extra power compensation is needed for error propagation in the relay-assisted scenario to provision the same end-to-end bit error rate (BER...

In this paper, we propose a novel power saving scheme for relay nodes, equipped with multiple wireless network interface cards (WNICs), in IEEE 802.11 infrastructure networks. While most of recent studies have focused on power saving of end stations, the power saving of relay nodes can become even more critical when the relay nodes operate on battery power. When a relay node is equipped with mu...

Because of the best-effort service in Internet, direct routing path of Internet may not always meet the VoIP quality requirements. Thus, many researches proposed Peer-to-Peer VoIP systems such as SIP+P2P system, which uses relay node to relay RTP stream from the source node to the destination node and uses application-layer routing scheme to lookup the best relay nodes. The key of those systems...

Bidirectional relay communication has attracted the research community due to its high bandwidth efficiency. Space Shift Keying (SSK) modulation is a promising Multiple-Input– Multiple-Output (MIMO) technique in which only a single antenna is activated for transmission at any time instant and the index of this active antenna is used to convey information. In this paper, Physical Layer Network C...

Deployment of wireless relay nodes can enhance system capacity, extend wireless service coverage, and reduce energy consumption in wireless networks. Network coding enables us to mix two or more packets into a single coded packet at relay nodes and improve performances in wireless relay networks. In this paper, we succeed in developing analytical models of the throughput and delay on slotted AL...

The prominence of the wireless communication has been urging the monotonically increasing demand of security and privacy. In wireless systems, the notion of perfect secrecy of information with respect to illegitimate nodes can be ensured via physical layer security (PLS) techniques. Unfortunately, they can be made less effective if sourceeavesdropper wiretap channel is better than the main sour...

Cooperative communication can be considered as a promising technology to significantly increase the transmission rate along with the coverage area of a wireless network which aims to achieve spatial diversity via the cooperation of user terminals in transmission without requiring installation of multiple transceiver antennas. The user terminals which can be used for this purpose can be termed a...