A directional antenna based leader–follower relay system for end-to-end robot communications
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This paper describes a new general purpose electromagnetic relay for use in telephone switching systems. It is a wire spring relay known as the AF type relay and, with variations which provide slow release or marginal characteristics, it is known as the AG and AJ relay, respectively. Fig. 1 shows a typical AF type relay, Fig. 2 shows all of the parts of the relay and Fig. 3 is a drawing showing the relay assembly.
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Digital protective relay
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We look at the three-node relay channel and the transmission of an information symbol from the source node to the destination node. We let the relay be a memoryless function and formulate necessary conditions for the optimality of the relay mapping and the detector. Based on these, we propose a design algorithm to find relay mappings such that the symbol error rate at the destination is minimized. The optimized relay mappings are illustrated for different scenarios and the dependency between the relay mapping and the link qualities is discussed in detail. Furthermore, the performance is compared to the existing schemes detect-and-forward, amplify-and-forward, and estimate-and-forward. It is shown that there is a significant gain in terms of decreased symbol error rate if the optimized relay mapping is used.
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Abstract In this paper, we jointly optimize the position of the relay node and transmission power ratio of the source node over the relay node to minimize the outage probability, which can provide guidance for IEEE 802.16j transparent relay node configuration. The result indicates that the outage probability is minimum when the relay is positioned at the midway between the source and the destination, and the transmission power ratio of the source node over the relay node is 11:9. Copyright © 2009 John Wiley & Sons, Ltd.
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Decode-and-forward (D-F) and compress-and-forward (C-F) are two fundamentally different relay strategies proposed by (Cover and El Gamal, 1979). Individually, either of them has been successfully generalized to multi-relay channels. In this paper, to allow each relay node the freedom of choosing either of the two strategies, we propose a unified framework, where both the D-F and C-F strategies can be employed simultaneously in the network. It turns out that, to fully incorporate the advantages of both the best known D-F and C-F strategies into a unified framework, the major challenge arises as follows: For the D-F relay nodes to fully utilize the help of the C-F relay nodes, decoding at the D-F relay nodes should not be conducted until all the blocks have been finished; However, in the multi-level D-F strategy, the upstream nodes have to decode prior to the downstream nodes in order to help, which makes simultaneous decoding at all the D-F relay nodes after all the blocks have been finished inapplicable. To tackle this problem, nested blocks combined with backward decoding are used in our framework, so that the D-F relay nodes at different levels can perform backward decoding at different frequencies. As such, the upstream D-F relay nodes can decode before the downstream D-F relay nodes, and the use of backward decoding at each D-F relay node ensures the full exploitation of the help of both the other D-F relay nodes and the C-F relay nodes. The achievable rates under our unified relay framework are found to combine both the best known D-F and C-F achievable rates and include them as special cases.
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The mobility of relay has great influence on the performance of a cooperative relay system.This paper proposes a dynamic selection scheme under the amplify-and-forward communication mode in high mobility environment,based on the estimation of channels and the power allocation for each relay node by comparing it with the pre-set threshold.This scheme is used to choose the cooperative relay dynamically for a multiple relay scenario.Simulation results show that this proposed relay selection scheme decreases the outage probability effectively,maintains system capacity well,and improves the performance of the relay system.
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Application and selection of a relay are a key question to improve reliability of the system operation.Combining with the system operating characteristic,work enviornment and relay characteristic,the paper describes the system principle of the relay and the selection of quality grade in the relay application and the principle of the relay derating use.The instulation and protecting technology of the relay and the problems for the relay applocation are analyzed.
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Decode-and-forward (D-F) and compress-and-forward (C-F) are two fundamentally different relay strategies proposed by (Cover and El Gamal, 1979). Individually, either of them has been successfully generalized to multi-relay channels. In this paper, to allow each relay node the freedom of choosing either of the two strategies, we propose a unified framework, where both the D-F and C-F strategies can be employed simultaneously in the network. It turns out that, to fully incorporate the advantages of both the best known D-F and C-F strategies into a unified framework, the major challenge arises as follows: For the D-F relay nodes to fully utilize the help of the C-F relay nodes, decoding at the D-F relay nodes should not be conducted until all the blocks have been finished; However, in the multi-level D-F strategy, the upstream nodes have to decode prior to the downstream nodes in order to help, which makes simultaneous decoding at all the D-F relay nodes after all the blocks have been finished inapplicable. To tackle this problem, nested blocks combined with backward decoding are used in our framework, so that the D-F relay nodes at different levels can perform backward decoding at different frequencies. As such, the upstream D-F relay nodes can decode before the downstream D-F relay nodes, and the use of backward decoding at each D-F relay node ensures the full exploitation of the help of both the other D-F relay nodes and the C-F relay nodes. The achievable rates under our unified relay framework are found to combine both the best known D-F and C-F achievable rates and include them as special cases.
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In this paper, we develop an optimal relay selection strategy for a two-way relay network consisting of two transceivers and multiple relay nodes. Our relay selection approach is based on finding the relay which results in the minimal power consumption in the entire network while ensuring the transceivers' quality of services (QoSs), measured by their received signal-to-noise ratios (SNRs), are above certain given thresholds. We show that such a relay selection scheme yields a closed-form solution for power allocation among the two transceivers and the optimally selected relay.
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Aims: Considering the effect of relay occupancy at relay selection schemes and also proposing a new approach which helps the selection schemes to find the best free relay. Study Design: Comparative study by simulation in MATLAB software. Place and Duration of Study: Digital Communications Signal Processing (DCSP) Lab. of Shahid Rajaee Teacher Training University (SRTTU), Since 1 st June 2012 up to 1 st August 2014. Methodology: In the existing research works, relay-based system is modeled by a pair of transmitter-receiver nodes and a number of relays. Also, it is assumed that the selected relays are always free. In this investigation, the effect of relay occupancy due to other pairs is considered. For this purpose, a uniform distribution is applied for all relays to show the effect of free or busy relay nodes. Then, the performance of the relay selection methods is obtained by using two well-known performance metrics, bit error rate (BER) and outage probability. As the main goal of this research, a new approach is proposed which first finds the free relays and then applies one of the selection
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We look at the three-node relay channel and the transmission of an information symbol from the source node to the destination node. We let the relay be a memoryless function and formulate necessary conditions for the optimality of the relay mapping and the detector. Based on these, we propose a design algorithm to find relay mappings such that the symbol error rate at the destination is minimized. The optimized relay mappings are illustrated for different scenarios and the dependency between the relay mapping and the link qualities is discussed in detail. Furthermore, the performance is compared with existing schemes, such as decode-and-forward, amplify-and- forward, and estimate-and-forward. It is shown that there is a significant gain in terms of decreased symbol error rate if the optimized relay mappings are used.
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