Although the amplify-and-forward (AF) relaying is an effective and simple technique for cooperative communication networks, it introduces a noise enhancement problem. This problem occurs when the effects of interferen...
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ISBN:
(纸本)9781479931972
Although the amplify-and-forward (AF) relaying is an effective and simple technique for cooperative communication networks, it introduces a noise enhancement problem. This problem occurs when the effects of interference and the multipath fades are amplified during the transmission from the source to the relay. AF is usually used with the multiple access broadcast (MABC) protocol which is a two phases transmission (2P) analog network coding (ANC) protocol for the half-duplex (HD) communication mode. However, MABC is not designed to utilize the direct link (DL) signal no matter how strong it is. To utilize the DL signal, a three transmission phases protocol known as time-division broadcast protocol (TDBC) was proposed at which both end nodes transmit their message at consecutive time slots and the relay nodes broadcasts a combined signal at the 3 rd time slot. To deal with the noise enhancement problem and improve the system performance, this paper proposes a zero-forcing based relay power allocation (ZF-RPA) scheme to be used with TDBC protocol, where the noise enhancement is mitigated by introducing adaptive ZF gains at the relay node that inverses the channels effects between sources and relay when the signal is constructed to be transmitted at the third phase of the TDBC. Analytical results of the ZF-RPA scheme is compared to the traditional variable-gain (VG-RPA) scheme under the same nodes power allocation. Simulation results show that the ZFRPA is superior for all channel qualities in terms of the outage probability compared to the traditional VG-RPA. The total system sum rate comparison reveals that the ZF-RPA scheme could outperform the VG-RPA scheme as long as the channel qualities of the relay-transceiver links are less than certain threshold. This paper also clarifies that it is effective to select either ZF or VG-RPA according to the channel qualities and it can be implemented with VHDL by introducing an adaptive control unit (ACU).
In this paper, joint transmit/receive frequency-domain equalization (FDE) is proposed for analognetwork coded (ANC) single-carrier (SC) bi-directional multi-antenna relay. In the proposed scheme, diversity transmissi...
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In this paper, joint transmit/receive frequency-domain equalization (FDE) is proposed for analognetwork coded (ANC) single-carrier (SC) bi-directional multi-antenna relay. In the proposed scheme, diversity transmission using transmit FDE is performed at relay station (RS) equipped with multiple antennas while receive FDE is carried out at base station (BS) and mobile terminal (MT) both equipped with single antenna. The transmit and receive FDE weights are jointly optimized so as to minimize the end-to-end mean square error (MSE). We evaluate, by computer simulation, the throughput performance and show that the joint transmit/receive FDE obtains the spatial and frequency diversity gains and accordingly achieve better throughput performance compared to either the transmit FDE only or the receive FDE only. It is also shown that ANC SC bi-directional multi-antenna relay can extend the communication coverage area for the given required throughput compared to conventional direct transmission
Conventional wireless broadcast protocols rely heavily on the 802.11-based CSMA/CA model, which avoids interference and collision by conservative scheduling of transmissions. While CSMA/CA is amenable to multiple conc...
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Conventional wireless broadcast protocols rely heavily on the 802.11-based CSMA/CA model, which avoids interference and collision by conservative scheduling of transmissions. While CSMA/CA is amenable to multiple concurrent unicasts, it tends to degrade broadcast performance significantly, especially in lossy and large-scale networks. In this paper, we propose a new protocol called Chorus that improves the efficiency and scalability of broadcast service with a MAC/PHY layer that allows packet collisions. Chorus is built upon the observation that packets carrying the same data can be effectively detected and decoded, even when they overlap with each other and have comparable signal strengths. It resolves collision using symbol-level interference cancellation, and then combines the resolved symbols to restore the packet. Such a collision-tolerant mechanism significantly improves the transmission diversity and spatial reuse in wireless broadcast. Chorus' MAC-layer cognitive sensing and scheduling scheme further facilitates the realization of such an advantage, resulting in an asymptotic broadcast delay that is proportional to the network radius. We evaluate Chorus' PHY-layer collision resolution mechanism with symbol-level simulation, and validate its network-level performance via ns-2, in comparison with a typical CSMA/CA-based broadcast protocol. Our evaluation validates Chorus's superior performance with respect to scalability, reliability, delay, etc., under a broad range of network scenarios (e.g., single/multiple broadcast sessions, static/mobile topologies).
Channel estimation error results in severe performance deterioration in wireless networks. In this paper, we study the impact of imperfect channel estimation (ICE) on the outage performance of bidirectional relaying w...
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Channel estimation error results in severe performance deterioration in wireless networks. In this paper, we study the impact of imperfect channel estimation (ICE) on the outage performance of bidirectional relaying where the two sources have asymmetric traffic requirements (ATRs). In particular, we focus on the amplify-and-forward (AF) relay-assisted multiple-access broadcast (MABC) protocol, i.e., MABC-AF, which has received much attention due to its high spectrum efficiency and low complexity. In the single-relay scenario, we derive exact and generalized closed-form expressions for system outage probability, which indicate that the system outage is determined by the unidirectional outage in the case of highly asymmetric traffic patterns. For more insights into our approach, the closed-form asymptotic expressions are also evaluated, manifesting the interesting error floor (EF) phenomenon due to ICE. Using these analytical results, we further develop a robust and practical optimum power-allocation (OPA) algorithm that minimizes the system outage probability under aggregate and individual node power constraints. In the multirelay scenario, by taking into account the traffic knowledge, a novel relay selection criterion is proposed for asymmetric MABC-AF, followed by its impact on the system outage probability in the presence of ICE. Numerical results validate the accuracy of our analytical results and highlight the effect of the proposed OPA algorithm under various traffic requirements and channel estimation errors. Furthermore, the results also show that the proposed relay selection criterion is superior to the classical max-min criterion with ATRs, and the performance improvement becomes remarkable as channel estimation error increases.
The throughput and stability properties of wireless networkcoding are evaluated for an arbitrary number of terminals exchanging broadcast traffic with the aid of a relay. First, coding and scheduling schemes are deri...
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The throughput and stability properties of wireless networkcoding are evaluated for an arbitrary number of terminals exchanging broadcast traffic with the aid of a relay. First, coding and scheduling schemes are derived that minimize the number of transmissions needed for each node to broadcast one packet. For stochastically varying traffic, the stable throughput is then compared under both digital and analog network coding schemes. The initial analysis focuses on a network with a single relay. Extensions to arbitrary terminal-relay configurations are then outlined for a general multihop network. Backpressure-like algorithms for jointly achieving throughput optimal scheduling and networkcoding are given for each networkcoding scheme.
In this article we study the problem of scheduling wireless links in the physical interference model with interference decoding capability. We analyze two models with different decoding strategies that explore the fac...
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In this article we study the problem of scheduling wireless links in the physical interference model with interference decoding capability. We analyze two models with different decoding strategies that explore the fact that interfering signals should not be treated as random noise, but as well-structured signals. The first model makes use of successive interference cancelation, which allows the strongest signal to be iteratively decoded and subtracted from a collision, thus enabling the decoding of weaker simultaneous signals. The second model explores the fact that routers are able to forward the interfered signal of a pair of nodes that wish to exchange a message and these nodes are able to decode the collided messages by subtracting their own contribution from the interfered signal. We prove that the scheduling problem remains NP-complete in both models. Moreover, we propose a polynomial-time scheduling algorithm that uses successive interference cancelation to compute short schedules for network topologies formed by nodes arbitrarily distributed in the Euclidean plane. We prove that the proposed algorithm is correct in the physical interference model and provide simulation results demonstrating the performance of the algorithm in different network topologies. We compare the results to solutions without successive interference cancelation and observe that considerable throughput gains are obtained in certain scenarios. (C) 2013 Elsevier B.V. All rights reserved.
Relay-based cooperative wireless networks have been widely considered one of the cost-effective solutions to meet the demands in future wireless networks. In order to maximize the overall sum-rate while maintaining pr...
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Relay-based cooperative wireless networks have been widely considered one of the cost-effective solutions to meet the demands in future wireless networks. In order to maximize the overall sum-rate while maintaining proportional fairness among users, we investigate different resource allocation algorithms in two-way relay networks with analog network coding (ANC) protocol and time division broadcast (TDBC) protocol. The algorithms investigated are different from traditional proportional fairness schemes in terms of fairness and computational complexity as we have applied Access Proportional Fairness (APF) and Minimum Rate Proportional Fairness (MRPF) along with load balancing at the relays. A MATLAB simulation has been performed and simulation results show the effectiveness of these algorithms.
In analognetwork coded (ANC) relay with conventional channel estimation, the feedback of the estimated channel state information (CSI) is required, and hence, the bandwidth efficiency decreases. A cyclic-shifted pilo...
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ISBN:
(纸本)9781479903085
In analognetwork coded (ANC) relay with conventional channel estimation, the feedback of the estimated channel state information (CSI) is required, and hence, the bandwidth efficiency decreases. A cyclic-shifted pilot aided channel estimation (CSPACE) is used to simultaneously estimate two equivalent channels which are required for joint transmit/receive frequency-domain equalization (FDE) and own transmitted signal removal and hence, it requires no CSI feedback. In CSPACE, the delay time-domain windowing is used to separate two equivalent channels and suppress the impact of noise. However, in single-carrier (SC) ANC multi-antenna bi-directional relay (SC-ANC-MBDR) with the joint transmit/receive FDE, the equivalent channel is a concatenation of the propagation channel and the transmit FDE, and hence, its impulse response spreads over the entire delay time-domain. Therefore, the optimal delay time-domain window varies according to changing instantaneous received signal-to-noise power ratio (SNR), and as a consequence, the channel estimation accuracy degrades if the window width for the delay time-domain windowing is not adapted to the instantaneous received SNR. In this paper, we propose an adaptive window width control (AWWC) for CSPACE. The proposed AWWC adaptively changes the window size so as to minimize the mean square error (MSE) between the channel estimate and the actual channel. It is confirmed by the computer simulation that CSPACE using our proposed AWWC can always achieve BER performance superior to when using fixed window width.
Two-way amplify-and-forward (AP) relay network with both cooperative communication and analog network coding (ANC) has attracted great attention. In this paper, we formulate the fundamental issue, i.e., the optimal se...
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ISBN:
(纸本)9781467352390;9781467352376
Two-way amplify-and-forward (AP) relay network with both cooperative communication and analog network coding (ANC) has attracted great attention. In this paper, we formulate the fundamental issue, i.e., the optimal selection of multiple AF relays in a two-way dual-hop cooperative network, into linear fractional programming (LFP) problems. Firstly, in case of channel reciprocity, by minimizing the sum of the inverse of signal-to-noise ratios (SNR), the AF relays can be selected optimally by the LFP algorithms. Moreover, we derive a closed-form solution to this case, and prove that a node either participates relaying with full transmission power, or ceases relaying. Then, for the general (possibly channel non-reciprocity) case, by maximizing the weighted sum SNR, we show that the relay selection can be optimized by the sum-of-ratios LFP algorithms. Simulations are conducted to verify the proposed results.
In this paper, we consider a two-way relay channel (TWRC) network model in wireless bidirectional network, where end nodes have the full channel-state information (CSI) and relay nodes only have the channel-amplitude ...
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ISBN:
(纸本)9781479915323
In this paper, we consider a two-way relay channel (TWRC) network model in wireless bidirectional network, where end nodes have the full channel-state information (CSI) and relay nodes only have the channel-amplitude information (CAI). Our objective is to minimize the transmission power under the condition that the required transmission rates are satisfied. Different from previous works which assume no direct transmission paths exist between the source and destination nodes due to high shadow fading or large separation, we propose energy efficient power allocation methods for both analog network coding (ANC) and time division broadcasting (TDBC) schemes, and the closed-form expressions of optimal power allocation schemes are derived. Simulation results demonstrate the energy efficiency of the ANC and TDBC based power allocation methods comparing with other transmission schemes.
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