80 research outputs found
On the Performance of the Relay-ARQ Networks
This paper investigates the performance of relay networks in the presence of
hybrid automatic repeat request (ARQ) feedback and adaptive power allocation.
The throughput and the outage probability of different hybrid ARQ protocols are
studied for independent and spatially-correlated fading channels. The results
are obtained for the cases where there is a sum power constraint on the source
and the relay or when each of the source and the relay are power-limited
individually. With adaptive power allocation, the results demonstrate the
efficiency of relay-ARQ techniques in different conditions.Comment: Accepted for publication in IEEE Trans. Veh. Technol. 201
On Noisy ARQ in Block-Fading Channels
Assuming noisy feedback channels, this paper investigates the data transmission efficiency and robustness of different
automatic repeat request (ARQ) schemes using adaptive power allocation. Considering different block-fading channel
assumptions, the long-term throughput, the delay-limited throughput, the outage probability and the feedback load of
different ARQ protocols are studied. A closed-form expression for the power-limited throughput optimization problem is obtained which is valid for different ARQ protocols and feedback channel conditions. Furthermore, the paper presents numerical investigations on the robustness of different ARQ protocols to feedback errors. It is shown that many analytical assertions about the ARQ protocols are valid both when the channel remains fixed during all retransmission rounds and when it changes in each round (in)dependently. As demonstrated, optimal power allocation is crucial for the performance of noisy ARQ schemes when the goal is to minimize the outage probability
On the Performance of MIMO-ARQ Systems with Channel State Information at the Receiver
This paper investigates the performance of multiple-input-multiple-output (MIMO) systems in the presence of automatic repeat request (ARQ) feedback. We show that, for a large range of performance metrics, the data transmission efficiency of the ARQ schemes is determined by a set of parameters which are scheme-dependent and not metric-dependent. Then, the results are used to study different aspects of MIMO-ARQ such as the effect of nonlinear power amplifiers, large-scale MIMO-ARQ, adaptive power allocation and different data communication models. The results, which are valid for various forward and feedback channel models, show the efficiency of the MIMO-ARQ techniques in different conditions
Cross-layer link adaptation for goodput optimization in MIMO BIC-OFDM systems
This work proposes a novel cross-layer link performance prediction (LPP) model and link adaptation (LA) strategy for soft-decoded multiple-input multiple-output (MIMO) bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) systems employing hybrid automatic repeat request (HARQ) protocols. The derived LPP, exploiting the concept of effective signal-to-noise ratio mapping (ESM) to model system performance over frequency-selective channels, does not only account for the actual channel state information at the transmitter and the adoption of practical modulation and coding schemes (MCSs), but also for the effect of the HARQ mechanism with bit-level combining at the receiver. Such method, named aggregated ESM, or αESM for short, exhibits an accurate performance prediction combined with a closed-form solution, enabling a flexible LA strategy, that selects at every protocol round the MCS maximizing the expected goodput (EGP), i.e., the number of correctly received bits per unit of time. The analytical expression of the EGP is derived capitalizing on the αESM and resorting to the renewal theory. Simulation results carried out in realistic wireless scenarios corroborate our theoretical claims and show the performance gain obtained by the proposed αESM-based LA strategy when compared with the best LA algorithms proposed so far for the same kind of systems
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