In this letter, we propose a novel transmission scheme based on lattice precoding and pre-distorted constellation for the two-user AWGN degraded broadcast channel. In the proposed scheme, the lattice precoding is used...
详细信息
In this letter, we propose a novel transmission scheme based on lattice precoding and pre-distorted constellation for the two-user AWGN degraded broadcast channel. In the proposed scheme, the lattice precoding is used for the weaker user to cancel the interference from the stronger user. The pre-distorted constellation is also proposed for the stronger user to overcome the nonlinear distortion due to the lattice precoding. Numerical results show that the achievable rate of the proposed transmission scheme is beyond the achievable rate region of the superposition coding and successive interference cancelation with finite input alphabets.
We study the effect on diversity of using the sphere encoder-based vector perturbation (VP) technique of Peel et al. and the lattice reduction-aided techniques (Babai approximations) of Windpassinger et al. on a subse...
详细信息
We study the effect on diversity of using the sphere encoder-based vector perturbation (VP) technique of Peel et al. and the lattice reduction-aided techniques (Babai approximations) of Windpassinger et al. on a subset of the transmitted symbols. For a system with n diversity channels, we prove that the diversity order gap between the maximum diversity of n achieved by the full-size VP and the minimum diversity of 1 provided by linear precoding can be bridged by applying VP to a group of transmitted symbols. In particular, we prove that the diversity order is n - l, where l is the number of symbols that are not vector-perturbed. We show that this result holds true for lattice-reduction with both the rounding-off and nearest plane Babai approximations. The result shows that in terms of diversity, the group of vector-perturbed users counts as a single user. In fact, in a multiple-input and multiple-output Gaussian broadcast channel with l linearly precoded users, we can add up to n - l VP users and the diversity order for all users will decrease only by one, irrespective of how many VP users are added.
Screen-camera communications, using a liquid crystal display (LCD) screen and camera image sensors, have been attractive variants of visible light communications (VLC) since any external light-emitting modules and pho...
详细信息
Screen-camera communications, using a liquid crystal display (LCD) screen and camera image sensors, have been attractive variants of visible light communications (VLC) since any external light-emitting modules and photo detectors are required for recent mobile devices, which are usually equipped with display and camera. A major issue in screen-camera communications is a performance loss in transmission rate due to nonlinear channel impairments with ambient noise. To improve transmission rates, we investigate the impact of nonlinear channel equalization, nonbinary channel coding, probabilistic shaping, and nonlinear precoding for high-order modulation schemes. Experimental evaluations using an LCD screen and camera demonstrate that our proposed scheme achieves 3.8-3.3 times higher transmission rates compared to existing schemes for a communication distance of 60-160 cm.
A new viewpoint for adopting the lattice reduction in communication over multiple-input multiple-output (MIMO) broadcast channels is introduced. lattice basis reduction helps us to reduce the average transmitted energ...
详细信息
A new viewpoint for adopting the lattice reduction in communication over multiple-input multiple-output (MIMO) broadcast channels is introduced. lattice basis reduction helps us to reduce the average transmitted energy by modifying the region which includes the constellation points. The new viewpoint helps us to generalize the idea of lattice-reduction-aided (LRA) precoding for the case of unequal-rate transmission, and obtain analytic results for the asymptotic behavior (signal-to-noise ratio (SNR) -> infinity) of the symbol error rate for the LRA precoding and the perturbation technique. Also, the outage probability for both cases of fixed-rate users and fixed sum rate is analyzed. It is shown that the LRA method, using the Lenstra-Lenstra-Lovasz (LLL) algorithm, achieves the optimum asymptotic slope of symbol error rate (called the precoding diversity).
In this paper, we consider the transceiver and relay design for the multiple-input multiple-output (MIMO) cellular two-way relay channel (cTWRC), where a multi-antenna base station (BS) exchanges information with mult...
详细信息
In this paper, we consider the transceiver and relay design for the multiple-input multiple-output (MIMO) cellular two-way relay channel (cTWRC), where a multi-antenna base station (BS) exchanges information with multiple multiantenna mobile stations via a multi-antenna relay station (RS). We propose a novel two-way relaying scheme to approach the sum capacity of the MIMO cTWRC. A key contribution of this work is a new nonlinear lattice-based precoding technique to precompensate the interstream interference, so as to achieve efficient interference-free lattice decoding at the relay. We derive sufficient conditions for the proposed scheme to asymptotically achieve the sum capacity of the MIMO cTWRC in the high signal-to-noise ratio (SNR) regime. To fully exploit the potential of the proposed scheme, we also investigate the optimal power allocation at the BS and the RS to maximize the weighted sum-rate of the MIMO cTWRC in the general SNR regime. It is shown that the problem can be formulated as a monotonic program, and a polyblock outer approximation algorithm is developed to find the globally optimal solution with guaranteed convergence. We demonstrate by numerical results that the proposed scheme significantly outperforms the existing schemes and closely approaches the sum capacity of the MIMO cTWRC in the high SNR regime.
暂无评论