385 research outputs found
Outage Capacity of Incremental Relaying at Low Signal-to-Noise Ratios
We present the \epsilon-outage capacity of incremental relaying at low
signal-to-noise ratios (SNR) in a wireless cooperative network with slow
Rayleigh fading channels. The relay performs decode-and-forward and repetition
coding is employed in the network, which is optimal in the low SNR regime. We
derive an expression on the optimal relay location that maximizes the
\epsilon-outage capacity. It is shown that this location is independent of the
outage probability and SNR but only depends on the channel conditions
represented by a path-loss factor. We compare our results to the
\epsilon-outage capacity of the cut-set bound and demonstrate that the ratio
between the \epsilon-outage capacity of incremental relaying and the cut-set
bound lies within 1/\sqrt{2} and 1. Furthermore, we derive lower bounds on the
\epsilon-outage capacity for the case of K relays.Comment: 5 pages, 4 figures, to be presented at VTC Fall 2009 in Anchorage,
Alask
Comparing the Outage Capacity of Transmit Diversity and Incremental Relaying
We present the e-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a wireless cooperative network with slow Rayleigh fading channels. The relay performs decode-and-forward and repetition coding is employed in the network, which is optimal in the low SNR regime. We derive an expression on the optimal relay location that maximizes the e-outage capacity. It is shown that this location is independent of the outage probability and SNR but only depends on the channel conditions represented by a path-loss factor. We compare our results to the e-outage capacity of the cut-set bound and demonstrate that the ratio between the e-outage capacity of incremental relaying and the cut-set bound lies within 1/wurzel2 and 1. Furthermore, we derive lower bounds on the e-outage capacity for the case of K relays
Outage Capacity of Bursty Amplify-and-Forward with Incremental Relaying
We derive the outage capacity of a bursty version of the amplify-and-forward
(BAF) protocol for small signal-to-noise ratios when incremental relaying is
used. We show that the ratio between the outage capacities of BAF and the
cut-set bound is independent of the relay position and that BAF is outage
optimal for certain conditions on the target rate R. This is in contrast to
decode-and-forward with incremental relaying, where the relay location strongly
determines the performance of the cooperative protocol. We further derive the
outage capacity for a network consisting of an arbitrary number of relay nodes.
In this case the relays transmit in subsequent partitions of the overall
transmission block and the destination accumulates signal-to-noise ratio until
it is able to decode.Comment: 5 pages, 3 figures, submitted to IEEE International Symposium on
Information Theory, Austin, TX, June 13-18, 201
H2-ARQ-relaying: spectrum and energy efficiency perspectives
In this paper, we propose novel Hybrid Automatic Repeat re-Quest (HARQ) strategies used in conjunction with hybrid relaying schemes, named as H2-ARQ-Relaying. The strategies allow the relay to dynamically switch between amplify-and-forward/compress-and-forward and decode-and-forward schemes according to its decoding status. The performance analysis is conducted from both the spectrum and energy efficiency perspectives. The spectrum efficiency of the proposed strategies, in terms of the maximum throughput, is significantly improved compared with their non-hybrid counterparts under the same constraints. The consumed energy per bit is optimized by manipulating the node activation time, the transmission energy and the power allocation between the source and the relay. The circuitry energy consumption of all involved nodes is taken into consideration. Numerical results shed light on how and when the energy efficiency can be improved in cooperative HARQ. For instance, cooperative HARQ is shown to be energy efficient in long distance transmission only. Furthermore, we consider the fact that the compress-and-forward scheme requires instantaneous signal to noise ratios of all three constituent links. However, this requirement can be impractical in some cases. In this regard, we introduce an improved strategy where only partial and affordable channel state information feedback is needed
On the Performance of the Relay-ARQ Networks
This paper investigates the performance of relay networks in the presence of
hybrid automatic repeat request (ARQ) feedback and adaptive power allocation.
The throughput and the outage probability of different hybrid ARQ protocols are
studied for independent and spatially-correlated fading channels. The results
are obtained for the cases where there is a sum power constraint on the source
and the relay or when each of the source and the relay are power-limited
individually. With adaptive power allocation, the results demonstrate the
efficiency of relay-ARQ techniques in different conditions.Comment: Accepted for publication in IEEE Trans. Veh. Technol. 201
- …