摘要 :
In future wireless mobile networks, data rate and quality of service are expected to be comparable to those of wired deployments. To achieve this target, novel architectures must be adopted, successfully countering the disadvantag...
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In future wireless mobile networks, data rate and quality of service are expected to be comparable to those of wired deployments. To achieve this target, novel architectures must be adopted, successfully countering the disadvantages of the wireless transmission. Inspired by that, cooperative relaying was proposed because of the various gains it introduces to the network. In this work we propose a scheme consisting of multi-mode decode and forward relays facilitating the communication between a base station and a user terminal (UT). By equipping the relays with two interfaces, we can exploit the plethora of the available wireless protocols. Also, instead of performing multi-relay transmissions, we adopt an opportunistic relaying scheme due to its simplicity and outage-optimality. Additionally, we incorporate successive transmissions to improve the spectral efficiency, thus recovering the half-duplex loss in capacity due to the two-hop transmission. However, as inter-relay interference arises from successive transmissions, we propose mitigation techniques through interference cancellation and out-band transmissions using the multi-mode relays. At the same time, an energy-aware mechanism is implemented in the selected relay's transmission, opting for power reduction, as the channel state information is acquired prior to the signal's forwarding to the UT. Finally, we give numerical results by comparing the proposed energy-aware multi-mode relaying (EA-MMR) scheme, with two other schemes in terms of average end-to-end capacity, outage probability, delay distribution and power gain.
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Considering a symmetric Gaussian multi-way relay channel (MWRC) with K users, this work compares two transmission strategies, namely one-way relaying (OWR) and multi-way relaying (MWR), in terms of their achievable rates. While in...
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Considering a symmetric Gaussian multi-way relay channel (MWRC) with K users, this work compares two transmission strategies, namely one-way relaying (OWR) and multi-way relaying (MWR), in terms of their achievable rates. While in OWR, only one user acts as data source at each time and transmits in the uplink channel access, users can make simultaneous transmissions in MWR. First, we prove that for MWR, lattice-based relaying ensures a gap less than 1/2(K-1) bit from the capacity upper bound while MWR based on decode-and-forward (DF) or amplify-and-forward (AF) is unable to guarantees this rate gap. For DF and AF, we identify situations where they also have a rate gap less than 1/2(K-1) bit. Later, we show that although MWR has higher relaying complexity, surprisingly, it can be outperformed by OWR depending on K and the system SNR. Summarily speaking, for large K and small users' transmit power, OWR usually provides higher rates than MWR.
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In this letter, we study two-way nonregenerative multiple-input multiple-output (MIMO) relay communications with multiple relay nodes. An iterative algorithm is developed to jointly optimize the source, relay, and receive matrices...
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In this letter, we study two-way nonregenerative multiple-input multiple-output (MIMO) relay communications with multiple relay nodes. An iterative algorithm is developed to jointly optimize the source, relay, and receive matrices such that the two-way sum mean-squared error (MSE) of the signal waveform estimation is minimized. Numerical examples demonstrate a better performance of the proposed algorithm compared with existing algorithms for two-way MIMO multi-relay networks.
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For a two-hop linear non-regenerative multipleinput multiple-output (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently esta...
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For a two-hop linear non-regenerative multipleinput multiple-output (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently established for a broad class of objective functions. The optimal source and relay matrices jointly diagonalize the MIMO relay system into a set of parallel scalar channels. In this paper, we show that this diagonalization is also optimal for a multihop MIMO relay system with any number of hops, which is a further generalization of several previously established results. Specifically, for Schur-concave objective functions, the optimal source precoding matrix, the optimal relay amplifying matrices and the optimal receiving matrix jointly diagonalize the multihop MIMO relay channel. And for Schur-convex objectives, such joint diagonalization along with a rotation of the source precoding matrix is also shown to be optimal. We also analyze the system performance when each node has the same transmission power budget and the same asymptotically large number of antennas. The asymptotic analysis shows a good agreement with numerical results under a finite number of antennas.
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We consider joint power allocation (PA) and relay positioning in a dual-hop regenerative relay system with multiple antennas equipped at the destination. With a fixed relay location, an adaptive PA strategy at the source and relay...
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We consider joint power allocation (PA) and relay positioning in a dual-hop regenerative relay system with multiple antennas equipped at the destination. With a fixed relay location, an adaptive PA strategy at the source and relay under a sum power constraint that minimizes the system outage probability is presented. With a fixed PA strategy, the optimal relay location is derived. We then propose to jointly optimize PA and relay location. It is shown that employing more destination antennas and/or choosing an appropriate relay location can significantly save the power needed at the relay. Numerical results are presented to demonstrate the performance of the proposed PA and relay positioning algorithms.
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In this paper, we address the issue of multiaccess communication through multi-hop linear non-regenerative relays, where all users, all relay nodes, and the destination node may have multiple antennas. Using a linear minimal mean-...
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In this paper, we address the issue of multiaccess communication through multi-hop linear non-regenerative relays, where all users, all relay nodes, and the destination node may have multiple antennas. Using a linear minimal mean-squared error (MMSE) receiver at the destination node, we demonstrate that the optimal amplifying matrix at each relay node can be viewed as a linear MMSE filter concatenated with another linear filter. As a consequence, the MSE matrix of the signal waveform estimation at the destination node is decomposed into the sum of the MSE matrices at all relay nodes. We show that at a high signal-to-noise ratio (SNR) environment, this MSE matrix decomposition significantly simplifies the solution to the problem of optimizing the source precoding matrices and relay amplifying matrices. Simulation results show that even at the low to medium SNR range, the simplified optimization algorithms have only a marginal performance degradation but a greatly reduced computational complexity and signalling overhead compared with the existing optimal iterative algorithm, and thus are of great interest for practical relay systems.
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This paper studies the precoder design of bidirectional networks in which each node is equipped with multiple antennas. In contrast to the conventional model of bidirectional relay networks, this paper considers a more general sce...
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This paper studies the precoder design of bidirectional networks in which each node is equipped with multiple antennas. In contrast to the conventional model of bidirectional relay networks, this paper considers a more general scenario, i.e., a multi-user multi-relay network. First, by assuming that perfect channel state information (CSI) is available, we investigate the precoding design for the relays and users to minimize the sum mean squared error (MSE) and the maximum of single user's MSE, respectively. Then, we consider a more practical scenario where CSI estimation error is taken into account. By means of alternating optimization approach, we decompose the main problem into several decoupled subproblems with tractable solutions. It is shown that, in both the perfect and imperfect CSI cases, the proposed precoding algorithms outperform the existing solutions in terms of MSE and bit-error-rate (BER) performance.
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In this letter, we address multiuser multi-hop multiple-input multiple-output (MIMO) relay communication systems with correlated MIMO fading channels. In particular, we consider the practical scenario where the channel fading is f...
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In this letter, we address multiuser multi-hop multiple-input multiple-output (MIMO) relay communication systems with correlated MIMO fading channels. In particular, we consider the practical scenario where the channel fading is fast and thus the instantaneous channel state information (CSI) is only available at the destination node, but unknown at all users and all relay nodes. We derive the structure of the optimal user precoding matrices and relay amplifying matrices that maximizes the users-destination ergodic sum mutual information. Compared with existing works, our results are more general, since we address multiuser scenarios, consider MIMO relays with a finite dimension, and take into account the noise vector at each relay node.
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In this paper, an overhearing protocol is proposed for two-way cooperative multiantenna relaying systems, where the relays equipped with multiple antennas collaborate to relay signals between the base station (BS) and two user equ...
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In this paper, an overhearing protocol is proposed for two-way cooperative multiantenna relaying systems, where the relays equipped with multiple antennas collaborate to relay signals between the base station (BS) and two user equipment units (UEs). In the proposed overhearing protocol, the UE in the uplink transmission phase transmits only in the first time slot, i.e., it remains silent in the second time slot, whereas the previous overhearing protocol assumes that the UE transmits also in the second time slot. Therefore, the proposed overhearing protocol is more power efficient. The precoding matrix at each cooperative relay is optimized in the sense of minimizing the weighted mean squared error (WMSE). Simulation results show that the proposed scheme shows not only lower mean squared error but also higher achievable sum rate than existing cooperative relaying schemes.
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Relay stations are usually used to enhance the signal strength for the users near cell boundary, thereby extending the cell coverage. However, transmission through a relay station needs two transmission phases. The first phase is ...
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Relay stations are usually used to enhance the signal strength for the users near cell boundary, thereby extending the cell coverage. However, transmission through a relay station needs two transmission phases. The first phase is from base station to relay station, and the second one is from relay station to mobile station. Thus, using relay station may decrease system capacity due to two-phase transmission time. As a result, whether or not data are transmitted by one-hop or two-hop phases should be determined according to both signal strength and throughput. In this paper, we investigate the optimal relay location aiming to maximize system capacity. We consider two relay selection rules for determining whether two-hop transmission will be used: signal strength-oriented and throughput-oriented selection rules. We find that the signal strength-oriented two-hop transmission may yield even lower system capacity than the one-hop transmission. In the throughput-oriented scheme, the two-hop transmission can achieve higher system capacity than the one-hop transmission. By simulations, we determine the optimal
relay location and show the coverage enhancement by the relaying network. Extensive simulations are performed to investigate the impacts of relay transmission power and the number of relay stations on system capacity and optimal relay location. The simulation results reveal important insights into designing a relaying network with high system capacity.
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