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Contention-based geographic relay selection for cooperative networks has been proposed as a state-free distributed scheme to efficiently select the best relay within a geographic area. The a priori choices for the relaying area cause different effects on the overall network performance. In this paper, we focus on the fundamental problem of predefining the relaying area and investigate its impact on...
In this paper, we propose an opportunistic feedback protocol with adaptive modulation. The proposed feedback protocol is divided into two stages. During first stage, the proposed scheme uses feedback collision information in order to find the signal-to-noise ratio region where the user with the best channel quality belongs to. In second stage, based on random access protocol, the users in that signal-to-noise...
The conventional amplify-and-forward relaying protocol has less complex but worse performance than the decode-and-forward type. In the orthogonal frequency division multiplexing (OFDM) multihop relay systems, the system capacity can be enhanced via using the subcarrier permutation scheme at the relay terminals. However, under the multiuser scenario, one subcarrier may possess the best condition for...
In this paper, we propose a Decode-and-Forward Network Coded (DFNC) multi-user cooperation scheme for orthogonal uplink channels in a wireless network. The network consists of m peers having independent information transmitting to a common destination. Each peer transmits its own data in the first time phase and serves as a relay in the second time phase to transmit the network coded information combining...
The ability to transmit a message securely in the presence of eavesdroppers in a dense wireless network is considered. As with a number of recent schemes, system nodes other than the transmitter and receiver are chosen to generate noise that confuses the eavesdropper. By exploiting the dynamics of the fading, significantly improved performance is achieved beyond that generated from the standard multi-user...
In this paper, we propose a feedback based cooperative transmission (FBCT) scheme for multiuser multichannel communication systems. We focus on uplink channels and consider a user, say user 1, who has a weak uplink channel. Another user (who is possibly located somewhere between the base station and user 1), say user 2, can be a relay for cooperative transmission. Using the feedback information of...
A key feature in the design of any MAC protocol is the throughput it can provide. In wireless networks, the channel of a user is not fixed but varies randomly. Thus, in order to maximize the throughput of the MAC protocol at any given time, only users with large channel gains should be allowed to transmit. In this paper, a compressive sensing based opportunistic protocol for exploiting multiuser diversity...
We study the impact of user cooperation in wireless networks on improving the stable throughput and delay performance. Specifically, we consider a multiaccess system in which a set of source users generate packets to deliver to a common destination. A cooperation strategy is proposed at the protocol level, where users with a better channel to the destination have the option to relay packets from users...
We consider a block fading multiple access relay channel (MARC) where K users communicate with a single destination in the presence of Q ges 1 half-duplex relays. Each relay employs a successive group decoder with a specified complexity constraint and a decode and forward (DF) protocol. We design an outage minimizing relaying strategy for the scenario where no channel dependent feedback is possible...
The performance of wireless network diversity multiple access protocols (NDMA) critically depends upon the correct detection of the active users (or the correct estimation of the collision multiplicity). If one or more transmitting users are not correctly detected as active then all the colliding packets will be probably lost due to either a lack of retransmission diversity or an inaccurate equalization...
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