3,516 research outputs found
Selective relaying for reliability in power line cooperative communication system
Power line communication (PLC), a technology that uses the existing infrastructure for electric power for the provision of data, is fast becoming the choice for smart grid system. As good a choice as the PLC is for smart grid applications, it has some characteristics that poses hazards to signal transmitted through it. The topology of the power network (star) poses challenges of attenuation and multipath to high-speed signal transmission. The noise in PLC is not only AWGN as in other communication system but also impulsive. In this paper, selective relaying is considered for improving the reliability of the power line cooperative communication system. Selective relaying was implemented in both amplify-And-forward and decode and forward links on the PLC. Best channel SNR was the selection criterion for the best relay. Performances of symbol error rate and channel capacity was compared for fixed and selective relaying cooperation on the PLC system. Over a specified SNR range, the selective amplify-And-forward achieved a 6% SER improvement over the fixed relaying, while 1% SER improvement was achieved by the selective relaying over the fixed relaying on the decode-And-forward link. The channel capacity performance comparison reveals that the selective relaying in all scenarios in PLC achieved appreciable improvement on both cooperative protocols than in the fixed relaying
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
Outage rates and outage durations of opportunistic relaying systems
Opportunistic relaying is a simple yet efficient cooperation scheme that
achieves full diversity and preserves the spectral efficiency among the
spatially distributed stations. However, the stations' mobility causes temporal
correlation of the system's capacity outage events, which gives rise to its
important second-order outage statistical parameters, such as the average
outage rate (AOR) and the average outage duration (AOD). This letter presents
exact analytical expressions for the AOR and the AOD of an opportunistic
relaying system, which employs a mobile source and a mobile destination
(without a direct path), and an arbitrary number of (fixed-gain
amplify-and-forward or decode-and-forward) mobile relays in Rayleigh fading
environment
Symbol-Level Selective Full-Duplex Relaying with Power and Location Optimization
In this paper, a symbol-level selective transmission for full-duplex (FD)
relaying networks is proposed to mitigate error propagation effects and improve
system spectral efficiency. The idea is to allow the FD relay node to predict
the correctly decoded symbols of each frame, based on the generalized square
deviation method, and discard the erroneously decoded symbols, resulting in
fewer errors being forwarded to the destination node. Using the capability for
simultaneous transmission and reception at the FD relay node, our proposed
strategy can improve the transmission efficiency without extra cost of
signalling overhead. In addition, targeting on the derived expression for
outage probability, we compare it with half-duplex (HD) relaying case, and
provide the transmission power and relay location optimization strategy to
further enhance system performance. The results show that our proposed scheme
outperforms the classic relaying protocols, such as cyclic redundancy check
based selective decode-and-forward (S-DF) relaying and threshold based S-DF
relaying in terms of outage probability and bit-error-rate. Moreover, the
performances with optimal power allocation is better than that with equal power
allocation, especially when the FD relay node encounters strong
self-interference and/or it is close to the destination node.Comment: 34 pages (single-column), 14 figures, 2 tables, accepted pape
Generalized Adaptive Network Coding Aided Successive Relaying Based Noncoherent Cooperation
A generalized adaptive network coding (GANC) scheme is conceived for a multi-user, multi-relay scenario, where the multiple users transmit independent information streams to a common destination with the aid of multiple relays. The proposed GANC scheme is developed from adaptive network coded cooperation (ANCC), which aims for a high flexibility in order to: 1) allow arbitrary channel coding schemes to serve as the cross-layer network coding regime; 2) provide any arbitrary trade-off between the throughput and reliability by adjusting the ratio of the source nodes and the cooperating relay nodes. Furthermore, we incorporate the proposed GANC scheme in a novel successive relaying aided network (SRAN) in order to recover the typical 50% half-duplex relaying-induced throughput loss. However, it is unrealistic to expect that in addition to carrying out all the relaying functions, the relays could additionally estimate the source-to-relay channels. Hence noncoherent detection is employed in order to obviate the power-hungry channel estimation. Finally, we intrinsically amalgamate our GANC scheme with the joint network-channel coding (JNCC) concept into a powerful three-stage concatenated architecture relying on iterative detection, which is specifically designed for the destination node (DN). The proposed scheme is also capable of adapting to rapidly time-varying network topologies, while relying on energy-efficient detection
Joint Relay Selection and Power Allocation in Large-Scale MIMO Systems with Untrusted Relays and Passive Eavesdroppers
In this paper, a joint relay selection and power allocation (JRP) scheme is
proposed to enhance the physical layer security of a cooperative network, where
a multiple antennas source communicates with a single-antenna destination in
presence of untrusted relays and passive eavesdroppers (Eves). The objective is
to protect the data confidentially while concurrently relying on the untrusted
relays as potential Eves to improve both the security and reliability of the
network. To realize this objective, we consider cooperative jamming performed
by the destination while JRP scheme is implemented. With the aim of maximizing
the instantaneous secrecy rate, we derive a new closed-form solution for the
optimal power allocation and propose a simple relay selection criterion under
two scenarios of non-colluding Eves (NCE) and colluding Eves (CE). For the
proposed scheme, a new closed-form expression is derived for the ergodic
secrecy rate (ESR) and the secrecy outage probability as security metrics, and
a new closed-form expression is presented for the average symbol error rate
(SER) as a reliability measure over Rayleigh fading channels. We further
explicitly characterize the high signal-to-noise ratio slope and power offset
of the ESR to highlight the impacts of system parameters on the ESR. In
addition, we examine the diversity order of the proposed scheme to reveal the
achievable secrecy performance advantage. Finally, the secrecy and reliability
diversity-multiplexing tradeoff of the optimized network are provided.
Numerical results highlight that the ESR performance of the proposed JRP scheme
for NCE and CE cases is increased with respect to the number of untrustworthy
relays.Comment: 18 pages, 10 figures, IEEE Transactions on Information Forensics and
Security (In press
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