Unaligned training for voice conversion based on a local nonlinear principal component analysis approach

2012

IEEE Trans. Commun.

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121

Recently, substantial attention has been paid to increase the achievable rates of wireless networks using different kinds of limited channel quality information feedback. Hybrid automatic repeat request (ARQ) and quantized channel state information (CSI) feedback are two well-known approaches applied by experts to provide the limited channel quality information at the transmitter. Considering quasi-static fading channels, this paper aims to provide some comparisons between the performance of these methods from different points of view. The paper first investigates the power-and outage-limited performance of hybrid ARQ and quantized CSI schemes under short-and long-term power constraints. Then, 1) the feedback signaling load, 2) robustness and 3) the complexity of these schemes are compared under short-term transmission power constraint. Both INcremental Redundancy (INR) and Repetition Time Diversity (RTD) approaches are considered for hybrid ARQ feedback. Finally, approximate low-complexity solutions are presented for power allocation in the INR ARQ-based scheme under long-term transmission power constraint.Analytical and numerical results demonstrate the equivalency or the superiority of these approaches in different circumstances.

Section: ) Short-term Power Constraintmentioning

confidence: 96%

On Hybrid ARQ and Quantized CSI Feedback Schemes in Quasi-Static Fading Channels

2012

IEEE Trans. Commun.

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121

“…Furthermore, our experiments show that the algorithm is much more efficient than using greedy search scheme which requires a large number of initial random seeds due to the non-convexity of (13). Finally, although it may be time-consuming when the number of optimization parameters increases, the proposed algorithm has been shown to be efficient in many complex optimization problems dealing with local minima issues [42].…”

Section: Average Rate With No Csi At the Transmittermentioning

confidence: 84%

Multiuser diversity in correlated Rayleigh-fading channels

2012

J Wireless Com Network

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This article studies the effect of scheduling and multiuser diversity on the performance of correlated Rayleighfading channels. More specifically, the power-limited channel average rate is obtained for quasi-static correlated fading channels. The results are obtained in the cases where there is perfect or imperfect channel state information available at the transmitter. Simulation results show that the average rate reduction due to channels dependencies is ignorable in low correlation conditions. However, the effect of scheduling and multiuser diversity on the average rate reduces substantially as the fading channels dependency increases. Also, for different channels correlation conditions, considerable performance improvement is achieved via very limited number of feedback bits.

“…Furthermore, our experiments show that the algorithm is much more efficient than using a greedy search scheme which requires a large number of initial random seeds due to the nonconvexity of (23). Finally, although it may be time consuming when the number of optimization parameters increases, the proposed algorithm has been shown to be efficient in many complex optimization problems dealing with local minima issues [50].…”

Section: Long-term Fairness Constraintmentioning

confidence: 85%

Fairness, power allocation, and CSI quantization in block fading multiuser systems

2013

J Wireless Com Network

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This paper studies the fairness, power allocation, and channel state information (CSI) quantization in multiuser systems utilizing multiple feedback bits per user. For a given set of schedulers, we obtain the system throughput with different power allocation strategies and any combination of different fading distributions. Moreover, the system performance under user different outage probability constraints is investigated. Assuming homogenous users, as a special case, the throughput is determined for fixed and random request networks. Considering nonidentical fading channels between the transmitter and receivers, the throughput is found under the K-significant average feedback bit allocation technique, and two suboptimal fairness schemes are investigated which satisfy different quality-of-service requirements. The results show that using optimal power allocation, the first quantization region (QR) of each user is the only QR for which no power may be allocated. The system outage probability vanishes as the number of users goes to infinity. Users hard outage probability constraints can be satisfied at the cost of one more QR in the channel quantizer. Finally, the proposed fairness schemes are more flexible than the standard proportional fair (PF) scheduling in dealing with the throughput-fairness tradeoff. However, their superiority over PF scheduling depends on the fairness constraint.