Дослідження мотиваційних чинників професійного становлення вчителя

This paper studies two-hop cooperative demodulate-and-forward relaying using multiple relays in wireless networks. A threshold based relay selection scheme is considered, in which the reliable relays are determined by comparing source-relay SNR to a threshold, and one of the reliable relays is selected by the destination based on relay-destination SNR. The exact bit error rate of this scheme is derived, and a simple threshold function is proposed. It is shown that the network achieves full diversity order (N +1) under the proposed threshold, where N is the number of relays in the network. Unlike some other full diversity achieving protocols in the literature, the requirement that the instantaneous/average SNRs of the source-relay links be known at the destination is eliminated using the appropriate SNR threshold

Adaptive Multi-Stream Relaying

Abstract — In this paper, we study a cooperative network with one source-destination pair and a relay assisting their communication. All terminals have multiple antennas, which enables them to transmit multiple streams simultaneously. Both the source and the relay use spatial multiplexing to transmit while the receivers at the relay and the destination are linear MMSE receivers. We extend some of the well known digital relaying protocols to multi-stream case and also propose two new adaptive protocols to reduce error propagation at the relay. We evaluate the block error rate of all the protocols and show the benefit of stream by stream decisions at the relay. I

Cooperative Relaying Schemes for Narrow-Band Frequency Hopping Wireless Ad Hoc Networks

Cooperative relaying is a promising technique for improving the performance of weak communication links in wireless networks by exploiting spatial diversity induced by relay transmissions. This paper considers cooperative relaying schemes for a narrow- band frequency hopping system. A novel hybrid relaying scheme called opportunistic hybrid relaying, which is specifically designed for this system, is presented. Unlike most relaying schemes in the literature, opportunistic hybrid relaying uses bandwidth efficiently by allowing the relays to transmit in non-orthogonal channels without any considerable coordination overhead among the relays. A joint channel estimation and data detection scheme is considered to be used at the destination to combine relay signals. It is shown that this scheme compares favorably to similar relaying schemes in the literature in terms of average success rate

Transmit Power Distribution of Wireless Ad-hoc Networks with Topology Control

Topology control and routing protocols are used by designers of wireless packet data networks to lower the node degree, simplify routing and lower the nodes’ energy consumption, while preserving strong connectivity. We assume a popular fading channel model and study the impact of several topology control schemes on the transmit power of nodes randomly distributed over a large area according to a Poisson point process, where each node controls the pattern of its one-hop neighbors by independently adjusting its transmit power. We provide the distribution of the transmit power of individual nodes under several different topology control algorithms, allowing designers to estimate the life time of battery energized devices, and the implications of choosing the nodes’ peak transmit power. We also allow easy comparisons between several different topology control algorithms with respect to the nodes’ power consumption