We derive the outage capacity of a bursty version of the amplify-and-forward (BAF) protocol for s... more 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.
We present a simple combining receiver for a dual-diversity wireless relay network. The main conc... more We present a simple combining receiver for a dual-diversity wireless relay network. The main concern of the paper is to face the trade-off between performance and complexity. The receiver focuses on signal-to-noise ratio (SNR) monitoring and selects dynamically between selection combining (SC) and equal gain combining (EGC) depending on the SNR ratio of the two received branches. It is shown that SC suffers no SNR degradation compared to a single branch communications system if the two receive branches are unbalanced, wheres EGC suffers a loss of 3 dB. Error performance with respect to branch unbalance is considered as well and limiting values for a high degree of branch unbalance are derived.
— Cooperative networking as a means of creating spatial diversity is used in order to mitigate th... more — Cooperative networking as a means of creating spatial diversity is used in order to mitigate the adverse effect of fading in a wireless channel and increase reliability of communications. We investigate signal-to-noise ratio (SNR) gain in wireless cooperative networks. We show that the differential SNR gain in the high data rate regime, which we refer to as SNR gain exponent ζ∞, is independent of the relaying strategy and only depends on the number of transmission phases used for communication. Furthermore, a straight-line upper and lower bound is derived based on geometric considerations. It is shown that the approximation error of the upper bound with respect to the exact SNR gain tends to zero for R → ∞. For the lower bound, the approximation error tends asymptotically to a constant factor δ for R → ∞. Both bounds are the best possible straight-line bounds with respect to absolute error.
We present a simple combining receiver for a dual-diversity wireless relay network. The main conc... more We present a simple combining receiver for a dual-diversity wireless relay network. The main concern of the paper is to face the trade-off between performance and complexity. The receiver focuses on signal-to-noise ratio (SNR) monitoring and selects dynamically between selection combining (SC) and equal gain combining (EGC) depending on the SNR ratio of the two received branches. It is shown that SC suffers no SNR degradation compared to a single branch communications sys-tem if the two receive branches are unbalanced, wheres EGC suffers a loss of 3 dB. Error performance with respect to branch unbalance is considered as well and limiting values for a high degree of branch unbalance are derived. I
We present the e-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a... more 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
We present the e-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a... more 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
International Symposium on Information Theory and Its Applications, 2010
We derive the outage capacity of a bursty version of the amplify-and-forward (BAF) protocol for s... more 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
We investigate the effect of imperfect feedback on the \epsilon-outage capacity of incremental re... more We investigate the effect of imperfect feedback on the \epsilon-outage capacity of incremental relaying in the low signal-to-noise ratio (SNR) regime. We show that imperfect feedback leads to a rescaling of the pre-log factor (comparable to the multiplexing gain for networks operating in the high SNR regime) and thus reduces the \epsilon-outage capacity considerably. Moreover, we investigate the effect of
2008 IEEE International Symposium on Wireless Communication Systems, 2008
We study signal-to-noise ratio (SNR) gains for two different cooperation strategies that are appl... more We study signal-to-noise ratio (SNR) gains for two different cooperation strategies that are applied to networks consisting of one source, one destination, and one or two relays, respectively. The first strategy is called orthogonal decode-and-forward where all transmit terminals transmit interference free in orthogonal time slots. The second strategy is called nonorthogonal decode-and-forward where all relays transmit simultaneously by applying
2010 4th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010
In this paper we present outage regions for two cooperation strategies, namely multi-routing and ... more In this paper we present outage regions for two cooperation strategies, namely multi-routing and adaptive multi-routing, if two different coding schemes are used. The first coding scheme is repetition coding and the second one is parallel channel coding. We show that for one cooperation strategy, the outage region for parallel channel coding is a strict subset of the outage probability
We derive the outage capacity of a bursty version of the amplify-and-forward (BAF) protocol for s... more 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.
We present a simple combining receiver for a dual-diversity wireless relay network. The main conc... more We present a simple combining receiver for a dual-diversity wireless relay network. The main concern of the paper is to face the trade-off between performance and complexity. The receiver focuses on signal-to-noise ratio (SNR) monitoring and selects dynamically between selection combining (SC) and equal gain combining (EGC) depending on the SNR ratio of the two received branches. It is shown that SC suffers no SNR degradation compared to a single branch communications system if the two receive branches are unbalanced, wheres EGC suffers a loss of 3 dB. Error performance with respect to branch unbalance is considered as well and limiting values for a high degree of branch unbalance are derived.
— Cooperative networking as a means of creating spatial diversity is used in order to mitigate th... more — Cooperative networking as a means of creating spatial diversity is used in order to mitigate the adverse effect of fading in a wireless channel and increase reliability of communications. We investigate signal-to-noise ratio (SNR) gain in wireless cooperative networks. We show that the differential SNR gain in the high data rate regime, which we refer to as SNR gain exponent ζ∞, is independent of the relaying strategy and only depends on the number of transmission phases used for communication. Furthermore, a straight-line upper and lower bound is derived based on geometric considerations. It is shown that the approximation error of the upper bound with respect to the exact SNR gain tends to zero for R → ∞. For the lower bound, the approximation error tends asymptotically to a constant factor δ for R → ∞. Both bounds are the best possible straight-line bounds with respect to absolute error.
We present a simple combining receiver for a dual-diversity wireless relay network. The main conc... more We present a simple combining receiver for a dual-diversity wireless relay network. The main concern of the paper is to face the trade-off between performance and complexity. The receiver focuses on signal-to-noise ratio (SNR) monitoring and selects dynamically between selection combining (SC) and equal gain combining (EGC) depending on the SNR ratio of the two received branches. It is shown that SC suffers no SNR degradation compared to a single branch communications sys-tem if the two receive branches are unbalanced, wheres EGC suffers a loss of 3 dB. Error performance with respect to branch unbalance is considered as well and limiting values for a high degree of branch unbalance are derived. I
We present the e-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a... more 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
We present the e-outage capacity of incremental relaying at low signal-to-noise ratios (SNR) in a... more 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
International Symposium on Information Theory and Its Applications, 2010
We derive the outage capacity of a bursty version of the amplify-and-forward (BAF) protocol for s... more 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
We investigate the effect of imperfect feedback on the \epsilon-outage capacity of incremental re... more We investigate the effect of imperfect feedback on the \epsilon-outage capacity of incremental relaying in the low signal-to-noise ratio (SNR) regime. We show that imperfect feedback leads to a rescaling of the pre-log factor (comparable to the multiplexing gain for networks operating in the high SNR regime) and thus reduces the \epsilon-outage capacity considerably. Moreover, we investigate the effect of
2008 IEEE International Symposium on Wireless Communication Systems, 2008
We study signal-to-noise ratio (SNR) gains for two different cooperation strategies that are appl... more We study signal-to-noise ratio (SNR) gains for two different cooperation strategies that are applied to networks consisting of one source, one destination, and one or two relays, respectively. The first strategy is called orthogonal decode-and-forward where all transmit terminals transmit interference free in orthogonal time slots. The second strategy is called nonorthogonal decode-and-forward where all relays transmit simultaneously by applying
2010 4th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010
In this paper we present outage regions for two cooperation strategies, namely multi-routing and ... more In this paper we present outage regions for two cooperation strategies, namely multi-routing and adaptive multi-routing, if two different coding schemes are used. The first coding scheme is repetition coding and the second one is parallel channel coding. We show that for one cooperation strategy, the outage region for parallel channel coding is a strict subset of the outage probability
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Papers by Tobias Renk