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- Cao, Le Phuong, et al.
(författare)
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Transmit Beamforming for Single-User Large-Scale MISO Systems With Sub-Connected Architecture and Power Constraints
- 2018
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Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 22:10, s. 2096-2099
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Tidskriftsartikel (refereegranskat)abstract
- This letter considers optimal transmit beamforming for a sub-connected large-scale MISO system with RF chain and per-antenna power constraints. The system is configured such that each RF chain serves a group of antennas. For the hybrid scheme, necessary and sufficient conditions to design the optimal digital and analog precoders are provided. It is shown that, in the optimum, the optimal phase shift at each antenna has to match the channel coefficient and the phase of the digital precoder. In addition, an iterative algorithm is provided to find the optimal power allocation. We study the case where the power constraint on each RF chain is smaller than the sum of the corresponding per-antenna power constraints. Then, the optimal power is allocated based on two properties: each RF chain uses full power and if the optimal power allocation of the unconstraint problem violates a per-antenna power constraint then it is optimal to allocate the maximal power for that antenna.
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- Cao, Phuong, et al.
(författare)
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Optimal Transmission Rate for MISO Channels with Joint Sum and Per-antenna Power Constraints
- 2015
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Ingår i: IEEE International Conference on Communications (ICC), London, June 08-12, 2015. - 9781467364324 ; , s. 4727-4732
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Konferensbidrag (refereegranskat)abstract
- We consider multiple-input single-output (MISO) Gaussian channels with joint sum and per-antenna power constraints. A closed-form solution of the optimal beamforming vector is derived which achieves the maximal transmission rate. The result shows that if the sum power constraint only optimal power allocation violates a per-antenna power constraint then the joint power constraint optimal power allocation is at the intersection of the sum power constraint and the per-antenna power constraints.
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- Cao, Phuong, et al.
(författare)
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Precoding Design for Massive MIMO Systems with Sub-connected Architecture and Per-antenna Power Constraints
- 2018
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Konferensbidrag (refereegranskat)abstract
- This paper provides the necessary conditions to design precoding matrices for massive MIMO systems with a sub-connected architecture, RF power constraints and per-antenna power constraints. The system is configured such that each RFchain serves a group of antennas. The necessary condition to design the digital precoder is established based on a generalized water-filling and joint sum and per-antenna optimal power allocation solution, while the analog precoder is based on a per-antenna power allocation solution only. We study the analytically most interesting case where the power constraint on the RF chain is smaller than the sum of the corresponding per-antenna power constraints. For this, the optimal power is allocated based on two properties: Each RF chain uses full power and if the optimal power allocation of the unconstraint problem violates a per-antenna power constraint then it is optimal to allocate the maximal power for that antenna.
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- Cervia, Giulia, et al.
(författare)
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Fixed-Length Strong Coordination
- 2019
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Ingår i: 2019 IEEE Information Theory Workshop, ITW 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538669006
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of synthesizing joint distributions of signals and actions over noisy channels in the finite length regime. For a fixed blocklength n and an upper bound on the distance ϵ, a coding scheme is proposed such that the induced joint distribution is \varepsilon-close in L1 distance to a target i.i.d. distribution. The set of achievable target distributions and rate for asymptotic strong coordination can be recovered from the main result of this paper by having n that tends to infinity.
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- Do, Hieu T., et al.
(författare)
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Interfering Relay Channels
- 2017
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Ingår i: Entropy. - : MDPI AG. - 1099-4300. ; 19:9
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces and studies a model in which two relay channels interfere with each other. Motivated by practical scenarios in heterogeneous wireless access networks, each relay is assumed to be connected to its intended receiver through a digital link with finite capacity. Inner and outer bounds for achievable rates are derived and shown to be tight for new discrete memoryless classes, which generalize and unify several known cases involving interference and relay channels. Capacity region and sum capacity for multiple Gaussian scenarios are also characterized to within a constant gap. The results show the optimality or near-optimality of the quantize-bin-and-forward coding scheme for practically relevant relay-interference networks, which brings important engineering insight into the design of wireless communications systems.
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- Do, Tan Tai, et al.
(författare)
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Uplink Waveform Channel With Imperfect Channel State Information and Finite Constellation Input
- 2017
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE Press. - 1536-1276 .- 1558-2248. ; 16:2, s. 1107-1119
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the capacity limit of an uplink waveform channel assuming imperfect channel state information at the receiver (CSIR). Various realistic assumptions are incorporated into the problem, which make the study valuable for performance assessment of real cellular networks to identify potentials for performance improvements in practical receiver designs. We assume that the continuous-time received signal is first discretized by mismatched filtering based on the imperfect CSIR. The resulting discrete-time signals are then decoded considering two different decoding strategies, i.e., an optimal decoding strategy based on specific statistics of channel estimation errors and a sub-optimal decoding strategy treating the estimation error signal as additive Gaussian noise. Motivated by the proposed decoding strategies, we study the performance of the decision feedback equalizer for finite constellation inputs, in which inter-stream interferences are treated either using their true statistics or as Gaussian noise. Numerical results are provided to exemplify the benefit of exploiting the knowledge on the statistics of the channel estimation errors and inter-stream interferences. Simulations also assess the effect of the CSI imperfectness on the achievable rate, which reveal that finite constellation inputs are less sensitive to the estimation accuracy than Gaussian input, especially in the high SNR regime.
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- Do, Tan Tai, et al.
(författare)
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Waveform domain framework for capacity analysis of uplink WCDMA systems
- 2015
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499.
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the capacity limit of an uplink WCDMA system considering a continuous-time waveform signal. Various realistic assumptions are incorporated into the problem, which make the study valuable for performance assessment of real cellular networks to identify potentials for performance improvements in practical receiver designs. An equivalent discrete-time channel model is derived based on sufficient statistics for optimal decoding of the transmitted messages. The capacity regions are then characterized using the equivalent channel considering both finite constellation and Gaussian distributed input signals. The capacity with sampling at the receiver is also provided to exemplify the performance loss due to a typical post-processing at the receiver. Moreover, we analyze the asymptotic capacity when the signal-to-noise ratio goes to infinity. The conditions to simultaneously achieve the individual capacities are derived, which reveal the impacts of signature waveform space, channel frequency selectivity and signal constellation on the system performance.
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