This article proposes both centralized and decentralized design schemes for an analog network coding multiple-input multiple-output system with a relay node between two end nodes. The proposed centralized scheme is ca...
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This article proposes both centralized and decentralized design schemes for an analog network coding multiple-input multiple-output system with a relay node between two end nodes. The proposed centralized scheme is called the generalized iterative approach (GIA). It jointly designs the precoders and decoders at the two end nodes, and the processor at the relay to maximize the sum mutual information. Numerical results for the per-node power constraint show the convergence behavior of the GIA and give a performance benchmark for the analog network coding scheme. The proposed decentralized scheme is a practical joint transceiver and signaling design scheme. The keys to its low signaling load are time-division duplex and a symmetric relay processing matrix. The proposed signaling protocol enables the needed information, including channel state information (CSI), to be available at each node. With the needed CSI, a novel symmetric processor design at the relay is developed to maximize an approximate sum mutual information formula (to reduce the signaling loading, the precoders at both end nodes and the noise propagated from the relay are not considered). Employing singular value decomposition transceivers at the two end nodes, it is remarkable that the proposed decentralized approach performs almost as well as the centralized GIA design. It is concluded that the proposed decentralized scheme is a feasible way to implement analog network coding systems.
analog network coding (ANC) is a promising technique of improving the throughput of relaying, especially when combined with both rate-and power-adaptation in the context of amplify-and forward two-way relaying (AF-TWR...
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analog network coding (ANC) is a promising technique of improving the throughput of relaying, especially when combined with both rate-and power-adaptation in the context of amplify-and forward two-way relaying (AF-TWR). In particular, the adaptation is employed both during the multiple access stage, when a pair of terminals transmit simultaneously to a relay, and during the broadcast stage, where the relay transmits to both terminals. Based on our bit-error-rate (BER) bounds, we formulate the explicit relationship amongst the data rates, transmit powers, and BERs. Then, we conceive a rate-and power adaptation scheme, operating both under specific average power constraints and BER constraints both at the relay node and at the two terminals. We observe that the transmit power of nodes does affect the data rate and hence using a fixed transmit power is not always optimal. We then derive a closed-form solution for continuous-rate ANC aided quadrature amplitude modulation/phase shift keying (ANC-QAM/PSK) using the classic Karush Kuhn Tucker method and conceive discrete-rate ANC-QAM/PSK regimes for practical wireless systems. The performance of the proposed scheme is evaluated through extensive simulations. Our performance results confirm that the proposed ANC-QAM/PSK outperforms its counterpart operating without power adaptation in a broad range of scenarios.
In this paper, we propose a simple analog network coding (ANC) scheme for asynchronous two-way relay networks where two sources exchange information through the relay nodes. In our proposed scheme, we consider a wirel...
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In this paper, we propose a simple analog network coding (ANC) scheme for asynchronous two-way relay networks where two sources exchange information through the relay nodes. In our proposed scheme, we consider a wireless scenario with frequency selective fading channels. Orthogonal frequencydivision multiplexing (OFDM) is implemented at the two sources and then the OFDM blocks are transmitted to the relay nodes in the first time slot. In the second time slot, at the relay nodes, the ANC that has a few simple operations are implemented on the received mixed signals and then the processed signals are broadcasted to the two sources to finish the information exchange. In this scheme, at each source, when recovering the designed information transmitted from another source, the received signals have the orthogonal space time block code (OSTBC) structure or the quasi-orthogonal space time block code (QOSTBC) structure on each subcarrier. By a proper power allocation, the two sources can achieve full spatial diversity and fast ML decoding without the requirement of symbol level synchronization. By the repetition across the subcarriers, multi-path diversity available in frequency selective fading channels can be also exploited. Moreover, the proposed ANC scheme is also valid for multi-way relay networks where multiple sources exchange information.
Mobile molecular communication via diffusion (MCvD) has attracted lots of attentions due to its time-varying channels. In this paper, we investigate a mobile two-way MCvD model, which consists of two mobile source nan...
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Mobile molecular communication via diffusion (MCvD) has attracted lots of attentions due to its time-varying channels. In this paper, we investigate a mobile two-way MCvD model, which consists of two mobile source nanomachines and a mobile relay nanomachine. The amplify-and-forward (AF) relaying and analog network coding (ANC) are utilized to implement the exchange of information between two source nanomachines in this model. To explore the performance of the mobile two-way MCvD system, we first adopt the depleted molecule shift keying (D-MoSK) modulation, and then the mathematical expressions of symbol error probability (SEP) and mutual information are derived by using AF and ANC scheme on the basis of maximum a posteriori (MAP) probability detection. Finally, we present the numerical and simulation results. Compared with the AF-No-ANC scheme which is without use of ANC scheme, the scheme of combining AF and ANC can significantly improve the performance of SEP and mutual information. Moreover, the D-MoSK modulation outperforms the molecule shift keying (MoSK) modulation for this mobile two-way MCvD system. In addition, we propose the evaluation and discussion about the impacts of several important parameters on the performance of this system. These results can be used to design mobile two-way MCvD system with lower SEP and higher mutual information.
The concept of analog network coding (ANC) considers the concurrent transmission of signals over the wireless medium so that they intentionally interfere. Higher network throughput can be achieved with ANC when an int...
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The concept of analog network coding (ANC) considers the concurrent transmission of signals over the wireless medium so that they intentionally interfere. Higher network throughput can be achieved with ANC when an intended transmission that a receiver desires to receive is made to interfere with a concurrent transmission of a signal known a priori at the receiver. In this paper, we present a cooperative protocol that exploits ANC. We consider a system with cooperative relaying of overlapped transmissions from two independent users. More specifically, we explore the case that network nodes may allow the transmitted signals to interfere both at the final destination node, and also at an intermediate node that acts subsequently as a relay. The relay employs a cooperative and multicast amplify-and-forward protocol so that the two destinations can use the interfered signals in order to recover the desired packet. We analyze this protocol in terms of the achieved rate and present an algorithm to recover signals from the overlapped transmissions. We study the impact of overlapping in signal transmissions on the throughput of the system. We show that even with considerable overlapping, the throughput under the proposed protocol is better in comparison to an orthogonal amplify-and-forward protocol.
In this paper, we focus on studying the optimal joint relay positioning and power allocation for two serial relays' transmission. We consider that information exchanges in Rayleigh flat-fading channels between two...
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In this paper, we focus on studying the optimal joint relay positioning and power allocation for two serial relays' transmission. We consider that information exchanges in Rayleigh flat-fading channels between two end-users which have symmetric traffic requirements in terms of the data rate. Multiple serial half-duplex relay nodes are employed to extend the communication coverage and assist the bidirectional communication between two end-users using the analog network coding protocol. With the objective of minimizing the total transmitting energy at the required data rate c, we investigate the optimal relay positioning and power allocation and then propose sub-optimal solutions for a two-serial-relay one-way channel and a two-serial-relay two-way channel due to no close-form optimal solution. Simulation results demonstrate a consistency with our proposed schemes.
In this paper, we consider a two-way relay system in which two users exchange data via a relay based on analog network coding (ANC) when multiple eavesdroppers exist. The relay replenishes energy from the two users...
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In this paper, we consider a two-way relay system in which two users exchange data via a relay based on analog network coding (ANC) when multiple eavesdroppers exist. The relay replenishes energy from the two users' signal and utilizes it to forward the ANC signal to each user. Each user removes its own signal from the received signal through self-interference cancellation and decodes the desired data signal. On the other hand, the eavesdroppers overhear the relaying signal and attempt to recover the data of two users. For this ANC-based two-way relay network with multiple eavesdroppers, we propose two secure ANC protocols: power splitting-ANC (PS-ANC) and time switching-ANC (TS-ANC), in which the relay determines the power splitting ratio (alpha) and time switching ratio (beta), respectively, to balance between the energy harvesting and the data reception. The optimal alpha and beta for each protocol are obtained analytically to maximize the minimum achievable secrecy rate (S-min) in consideration of multiple eavesdroppers. Analytical results show that both the PS-ANC and TS-ANC protocols with the optimal alpha and beta accomplish the near-optimal S-min irrespective of the locations and number of eavesdroppers. The comparison of these two protocols in various network environments exhibits that PS-ANC has a better performance than TS-ANC when the network conditions are unfavorable for wiretapping by the eavesdroppers.
Free space optical (FSO) communication link based on orthogonal frequency division multiplexing (OFDM) gives improved performance because of high bandwidth efficiency, improved robustness against fading, and narrow-ba...
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Free space optical (FSO) communication link based on orthogonal frequency division multiplexing (OFDM) gives improved performance because of high bandwidth efficiency, improved robustness against fading, and narrow-band interference. Any FSO system requires line-of-sight (LoS) link and in non-LoS (NLoS) situation, the two users cannot communicate directly resulting in link outage. To solve this problem, this paper proposes to use relay-assisted NLoS-FSO link with energy-saving three time-slotted analognetwork-coding approach to make the successful communication with increased throughput and improved error performance. The error performance of laser link is evaluated in terms of receiver sensitivity. Gamma-Gamma distribution is used for atmospheric turbulence in this analysis. The performance of relay-assisted intensity modulated/direct detected-OFDM FSO link with and without analog network coding (ANC) is compared.
In this correspondence, we consider general two-way relay networks (TWRNs) with two source and relay nodes. A distributed differential space time coding with analog network coding (DDSTC-ANC) scheme is proposed. A sim...
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In this correspondence, we consider general two-way relay networks (TWRNs) with two source and relay nodes. A distributed differential space time coding with analog network coding (DDSTC-ANC) scheme is proposed. A simple blind estimation and a differential signal detector are developed to recover the desired signal at each source. The pairwise error probability (PEP) and block error rate (BLER) of the DDSTC-ANC scheme are analyzed. Exact and simplified PEP expressions are derived. To improve the system performance, the optimum power allocation (OPA) between the source and relay nodes is determined based on the simplified PEP expression. The analytical results are verified through simulations.
Time asynchronism is a practical issue need to be addressed for a general distributed two-way relay network, where two terminal nodes exchange information through multiple spatial-separated relay nodes. In this letter...
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Time asynchronism is a practical issue need to be addressed for a general distributed two-way relay network, where two terminal nodes exchange information through multiple spatial-separated relay nodes. In this letter, we propose an analog network coding (ANC) scheme for a time asynchronous two-way relay network. In the proposed scheme, each relay node linearly transforms the received mixed asynchronous signals in the first time-slot by a Toeplitz matrix, and then broadcasts them back to the terminals in the second time-slot. A sufficient condition is derived for the proposed ANC to achieve full cooperative diversity using only linear receivers at the terminal nodes, such as zero-forcing (ZF), or minimum mean square error (MMSE) receivers, with any delay profiles of the timing errors. The decoding of the proposed ANC scheme is computationally efficient and the symbol rate can approach 1, when the coding block length is sufficiently large compared to the number of relay nodes.. and the timing errors.
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