Results 1  10
of
18
Performance of Fountain Codes in Collaborative Relay Networks
 IEEE Trans. Wireless Comm
, 2007
"... Cooperative communications, where parallel relays forward information to a destination node, can greatly improve the energy efficiency and latency in adhoc networks. However, current networks do not fully exploit its potential, as they only use traditional energyaccumulation, which is often used i ..."
Abstract

Cited by 33 (9 self)
 Add to MetaCart
Cooperative communications, where parallel relays forward information to a destination node, can greatly improve the energy efficiency and latency in adhoc networks. However, current networks do not fully exploit its potential, as they only use traditional energyaccumulation, which is often used in conjunction with repetition coding or cooperative spacetime codes. In this paper, we show that the concept of mutualinformationaccumulation can be realized with the help of fountain codes, and leads to a lower energy expenditure and a lower transmission time than energy accumulation. We then provide an analysis of the performance of mutual information accumulation in relay networks with N relay nodes. We first analyze the quasisynchronuous scenario where the source stops transmitting and the relay nodes start transmitting after L relay nodes have successfully decoded the source data. We show that an optimum L exists and is typically on the order of 3 or 4. We also give closedform equations for the energy savings that can be achieved by the use of mutualinformationaccumulation at the receiver. We then analyze and provide bounds for an alternate scenario where each relay node starts its transmission to the destination as soon as it has decoded the source data, independent of the state of the other relay nodes. This approach further reduces the transmission time, because the transmission by the relay nodes helps the other relay nodes that are still receiving.
Cooperative relay networks using fountain codes
 in Proceedings of the IEEE Global Telecommunications Conference
, 2006
"... We investigate a cooperative communications scheme with N parallel relays, where both the transmissions from the source to the relays and from the relays to the destination use fountain codes. Receiver for codes can accumulate mutual information, while traditional energy collection methods, such as ..."
Abstract

Cited by 11 (6 self)
 Add to MetaCart
(Show Context)
We investigate a cooperative communications scheme with N parallel relays, where both the transmissions from the source to the relays and from the relays to the destination use fountain codes. Receiver for codes can accumulate mutual information, while traditional energy collection methods, such as repetition or cooperative spacetime codes, only accumulate energy. As a consequence, using fountain codes can reduce the total energy required for transmitting data from the source to the destination. We first analyze the scenario where the source stops transmitting and the relay nodes start transmitting after L relay nodes have successfully decoded the source data. We optimize L, and also give closedform equations for the energy savings that can be achieved by the use of mutualinformationcollection at the receiver instead of the traditional energycollection methods. We then analyze an alternate scenario where each relay node starts its transmission to the destination as soon as it has decoded the source data, and helps the other relay nodes that are still in reception mode. Doing so further reduces the total transmission time and energy consumption.
A New Look at DualHop Relaying: Performance Limits with Hardware Impairments
, 2013
"... Abstract—Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assumes ideal hardware. Such approximations make sense ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
(Show Context)
Abstract—Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assumes ideal hardware. Such approximations make sense in lowrate systems, but can lead to very misleading results when analyzing future highrate systems. This paper quantifies the impact of hardware impairments on dualhop relaying, for both amplifyandforward and decodeandforward protocols. The outage probability (OP) in these practical scenarios is a function of the effective endtoend signaltonoiseanddistortion ratio (SNDR). This paper derives new closedform expressions for the exact and asymptotic OPs, accounting for hardware impairments at the source, relay, and destination. A similar analysis for the ergodic capacity is also pursued, resulting in new upper bounds. We assume that both hops are subject to independent but nonidentically distributed Nakagamim fading. This paper validates that the performance loss is small at low rates, but otherwise can be very substantial. In particular, it is proved that for high signaltonoise ratio (SNR), the endtoend SNDR converges to a deterministic constant, coined the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in contrast to the ideal hardware case in which the endtoend SNDR grows without bound in the highSNR regime. Finally, we provide fundamental design guidelines for selecting hardware that satisfies the requirements of a practical relaying system. Index Terms—Amplifyandforward, decodeandforward, dualhop relaying, ergodic capacity, Nakagamim fading, outage probability, transceiver hardware impairments. I.
Bypassing Orthogonal Relaying Transmissions via Spatial Signal Separation
"... Access (SDMA) into cooperative relaying, in order to bypass orthogonal relaying transmissions and thus achieve diversity gain without any cost on the available degrees of freedom. In particular, we propose a cooperative relaying scheme that utilizes two singleantenna relays and multiple antennas a ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
Access (SDMA) into cooperative relaying, in order to bypass orthogonal relaying transmissions and thus achieve diversity gain without any cost on the available degrees of freedom. In particular, we propose a cooperative relaying scheme that utilizes two singleantenna relays and multiple antennas at the destination terminal, in order to spatially separate the concurrently arriving signals. The whole concept is based upon two key elements: a) To combat the halfduplex constraint by having two relays transmitting alternatively, i.e., the one receiving while the other transmitting and vice versa, and b) to spatially separate the signals arriving concurrently at the destination using the wellknown optimum combining technique. Closedform expressions for the average capacity and outage probability are provided. Numerical results manifest that the proposed model outperforms orthogonal relaying as well as distributed spacetime coding in terms of average capacity and outage probability, owing to the former’s advantage of higher spectral efficiency. Index Terms—Space division multiple access (SDMA), optimum combining, wireless relaying technology. I.
Outage Rate and Outage Duration of DecodeandForward Cooperative Diversity Systems”, accepted for presentation at
 IEEE International Conf. Commun. (ICC
, 2011
"... Abstract—A complete evaluation of the benefits of cooperative diversity schemes should not only include the outage and error rate performance but also the secondorder statistics of the achievable informationtheoretic capacity. In a nonergodic fading channel, the system is said to be in outage wh ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
Abstract—A complete evaluation of the benefits of cooperative diversity schemes should not only include the outage and error rate performance but also the secondorder statistics of the achievable informationtheoretic capacity. In a nonergodic fading channel, the system is said to be in outage when the destination cannot decode the fixedrate transmitted signal with negligible error probability. Because of the Doppler effect, which is induced by the mobility of the wireless nodes, these capacity outage events are correlated. In this paper, we derive the average outage rate (AOR) and the average outage duration (AOD) of two wellknown cooperative diversity protocols, decodeandforward relaying and selection decodeandforward relaying, operating in slow Rayleigh fading channels. We also analyze the asymptotic behavior of these statistical parameters for high SNRs, where it is shown that the AOR exhibits a similar behavior as the outage probability. I.
1Exact and Asymptotic Outage Probability Analysis for DecodeandForward Networks
"... We consider decodeandforward cooperative networks and we derive analytical expressions as well as tractable asymptotic approximations for the outage probability of a network node. Our analysis sheds more light on the interplay between the channel conditions, the network size and the adopted transm ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
We consider decodeandforward cooperative networks and we derive analytical expressions as well as tractable asymptotic approximations for the outage probability of a network node. Our analysis sheds more light on the interplay between the channel conditions, the network size and the adopted transmission scheme, and provides a useful tool for the design of cooperative networks. Index Terms Cooperative systems, relays, fading channels, outage probability.
On the Study of Network Coding with Diverstiy 1
"... Recently proposed physicallayer network coding (PNC) [1] has demonstrated the promise to significantly improve the throughput of wireless networks whose links can be modeled as additive white Gaussian noise (AWGN) channels. However, the extension to multipath channels is problematic, since the tech ..."
Abstract
 Add to MetaCart
(Show Context)
Recently proposed physicallayer network coding (PNC) [1] has demonstrated the promise to significantly improve the throughput of wireless networks whose links can be modeled as additive white Gaussian noise (AWGN) channels. However, the extension to multipath channels is problematic, since the technique would then require both amplitude and phase compensation at each transmitter. Phase compensation requires accurate distributed phase tracking, whereas the required amplitude compensation is even more troubling, as it leads to an inefficient system that yields no diversity even in the presence of perfect channel estimates. Here, a system that avoids these limitations is obtained by reaching up one level higher in the network hierarchy and performing distributed relay selection with cognizance of the PNC technique that we will employ at the physical layer. Since the resulting scheme will achieve a form of selection diversity, we term it “network coding with diversity ” (NCD). To facilitate performance evaluation, two informationtheoretic metrics, the outage and ergodic capacity, are studied. Our analytical and simulation results show that the proposed protocol achieves more robust performance and higher system throughput than comparable schemes. Finally, the proposed network coding is extended to the context of cooperative multiple access channels, which yields a new cooperative protocol with larger outage and ergodic capacity compared with existing transmission schemes. I.
Fading Channels
, 2013
"... of this University and meets the accepted standards with ..."
(Show Context)
Outage Analysis for Coherent DecodeForward Relaying Over Rayleigh Fading Channels
"... Abstract—We analyze the outage performance of coherent partial decodeforward (pDF) relaying over Rayleigh fading channels in both half and fullduplex transmissions. In coherent DF relaying, the relay either partially or fully decodes the source message, then coherently forwards the decoded messa ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—We analyze the outage performance of coherent partial decodeforward (pDF) relaying over Rayleigh fading channels in both half and fullduplex transmissions. In coherent DF relaying, the relay either partially or fully decodes the source message, then coherently forwards the decoded message with the source to the destination. This coherent transmission creates a beamforming gain from the source and relay to the destination which improves the transmission rate. We analyze the impact of this beamforming gain on the outage performance, considering outage events at both the relay and the destination. We derive analytical expressions for the overall outage probability, assuming full CSI at receivers and only limited CSI at transmitters. We further show that at high SNR, coherent pDF relaying converges to full DF relaying and achieves the full diversity order of 2. These analyses provide a fundamental understanding of the reliability of coherent pDF relaying and form the basis for analyzing performance in larger network settings. Numerical results show that partial decoding at the relay outperforms full decoding for low SNR and high target rates in the halfduplex mode. Comparison with existing results further shows that sourcerelay coherent transmission and joint decoding at the destination both improve the outage performance. Index Terms—Decodeforward relaying, coherent relaying, partial relaying, joint decoding, outage analysis, diversity order. I.
IEEE TRANSACTIONS ON COMMUNICATIONS, ACCEPTED FOR PUBLICATION 1 A New Look at DualHop Relaying: Performance Limits with Hardware Impairments
"... Abstract—Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assumes ideal hardware. Such approximations make sens ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assumes ideal hardware. Such approximations make sense in lowrate systems, but can lead to very misleading results when analyzing future highrate systems. This paper quantifies the impact of hardware impairments on dualhop relaying, for both amplifyandforward and decodeandforward protocols. The outage probability (OP) in these practical scenarios is a function of the effective endtoend signaltonoiseanddistortion ratio (SNDR). This paper derives new closedform expressions for the exact and asymptotic OPs, accounting for hardware impairments at the source, relay, and destination. A similar analysis for the ergodic capacity is also pursued, resulting in new upper bounds. We assume that both hops are subject to independent but nonidentically distributed Nakagamim fading. This paper validates that the performance loss is small at low rates, but otherwise can be very substantial. In particular, it is proved that for high signaltonoise ratio (SNR), the endtoend SNDR converges to a deterministic constant, coined the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in contrast to the ideal hardware case in which the endtoend SNDR grows without bound in the highSNR regime. Finally, we provide fundamental design guidelines for selecting hardware that satisfies the requirements of a practical relaying system. Index Terms—Amplifyandforward, decodeandforward, dualhop relaying, ergodic capacity, Nakagamim fading, outage probability, transceiver hardware impairments. I.