In this paper a Markov decision process (MDP) model for virtualized content delivery networks is proposed. We use stochastic optimization to assign cloud site resources to each user group. We propose how quality of experience (QoE) can be included in the modeling and optimization. We then present an optimal solution for a constraint-free version of the problem, and show the improvement in accumulated revenue when our optimization model is used. A sub-optimal algorithm is proposed that would reduce the complexity of the problem. Simulation results are presented to support merits of the proposed algorithm.

Focusing on reliable and low-complexity backhaul-limited uplink coordinated multi-point (CoMP) systems, we propose two hybrid automatic repeat request (HARQ)-based protocols using incremental MIMO (IMIMO) approach for both centralized processing (CP) and distributed processing (DP). Using outage probability and throughput metrics, we compare the proposed protocols and the other HARQ-based MIMO approaches with both Chase combining (CC) and incremental redundancy (IR) schemes. Zero-forcing (ZF) receivers and limited capacity of backhaul are considered as practical assumptions. Effects of user locations, backhaul capacity, number of antennas, and low SNR regime are highlighted. The results indicate that IMIMO outperforms MIMO at low SNR region in both non-CoMP/CoMP scenarios, and approaches the performance of MIMO-HARQ in CoMP scenario.

In multicast networks it is necessary to secure the successful reception of the packet by all the intended receivers, which often calls for the retransmission of the packet up to a number of times. When each receiver is subject to signal deterioration due to fading and unrestrained inter-cluster interference, retransmissions however renders unacceptable large delay that eventually undermines the utility of multicasting. In this paper, we attempt to understand the impact of a practically attractive multi-antenna communication scheme viz. antenna selection combining (ASC) on enhancing the performance of a random multicast network under delay requirement. Since during retransmission attempts the transmitters and the receivers in each cluster likely stay stationary, igniting substantial interference correlation across antennas, the potential diversity of ASC may be dramatically destructed. We, here scrutinize the effect of this diversity loss on the multicast performance by analytically evaluating the multicast coverage efficiency (MCE), which measures the percentage of receivers who experience multicast coverage during the retransmission procedure. We provide a number of approximations on MCE as the main system parameters, and further study their accuracies. Our simulations show that ASC has benefits in improving MCE, however not as pronounced as one may otherwise experience when interference is de-correlated across antennas and retransmission attempts.

In this paper we investigate the capacity of random wireless networks in which transmitters are equipped with multiantennas. A quantized version of channel direction information (CDI) is also available, provided by the associated single antenna receivers. We adopt tools of stochastic geometry and random vector quantization to incorporate the impacts of interference and quantization errors, respectively. We first study the capacity of Aloha, and channel quality information (CQI)-based scheduling, whereby the transmissions decision in each transceiver pair depends on the strength of the CQI against a prescribed threshold. We then propose a new scheduling scheme, namely modified CQI (MCQI), by which the quantization error is effectively incorporated in the scheduling. Further we obtain the capacity of MCQI-based scheduling. Simulation results confirm our analysis and show that the proposed MCQI-based scheduling improves the capacity compared to the CQI-based scheduling and Aloha. It is also seen that the performance boost is more significant where the feedback capacity is low and the network is dense. In comparison with the case of high feedback capacity, the network capacity is not reduced by low feedback capacity in the MCQI-based scheduling. This is of practical importance since the network designer can save the feedback resources by employing MCQI-based scheduling without compromising the capacity and increasing the receivers' complexity.

In this paper, we focus on the analysis of the end-to-end outage probability of hybrid automatic repeat request (HARQ) in a multi-hop, block-fading channel. First, we use a Markov chain to model the multi-hop system with truncated HARQ type-I (HARQ-I) and derive closed-form expressions for the outage probability and throughput; we also obtain lower and upper bounds on the energy efficiency of the system. Then, we extend the analysis to cover HARQ with packet combining where we provide a general formulation of the outage probability; in special cases, closed-form expressions for outage probability and throughput are obtained. Finally, for a multi-hop system with opportunistic routing, we present recursive formulas to obtain outage probability and throughput. The expressions we derived allow us to draw conclusions about the outage diversity of different multi-hop protocols. In particular, we show that the diversity order is improved for opportunistic multi-hop system and is linearly increasing with the number of allowed transmissions for each packet. Numerical results illustrate how the analytical expression can be used to compare various multi-hop HARQ transmission strategies.

End-to-end outage probability and end-to-end throughput are analyzed in a multi-hop channel with truncated automatic repeat request type-I (ARQ-I). The system is modelled as a Markov chain and the closed-form expressions for the outage and throughput are derived for the cases of variable and equal distances between the nodes. The limits on the performance in high SNR and large number of transmissions are derived. We show that the diversity order is linearly increasing with the number of allowed transmission for each packet.

Abstract In this paper, we propose a novel cooperative relaying scheme with multiple relays for frequency selective wireless environment. In our proposed scheme, the frequency selective wireless channel is divided into flat fading sub‐channels. Cooperative relaying is then employed over each sub‐channel to improve the system diversity order. We then investigate the asymptotic behavior of the outage probability and show that the proposed scheme achieves full diversity order in both amplify and forward (AF) and adaptive decode and forward (ADF) relaying scenarios. Furthermore, we propose a power allocation strategy to minimize the system outage probability. Simulation results confirm our analysis and show that the proposed power allocation method outperforms uniform power allocation. Copyright © 2010 John Wiley & Sons, Ltd.

In this study, the authors propose two high spectral efficient relaying protocols with low communication overhead including: the priority-based relay selection (PRS), and the priority-based relay selection with incremental transmission (PRSIT). Relay selection and scheduling are integrated in the proposed protocols to achieve full diversity order as well as high spectral efficiency. The authors then define the communication overhead per allocated time slot to a user as the number of required signalling bits for channel estimation and implementing corresponding communication procedures. In this study, the authors show that their proposed protocols have much lower communication overhead comparing with other high spectral efficient cooperative protocols such as opportunistic relaying (OR) and OR with incremental transmission while their achieved diversity-multiplexing trade off performances are the same as those protocols. The authors further show that the average communication overhead for the PRS and PRSIT is a logarithmic function of the number of users while it is a linear function in OR and OR with incremental transmission. Simulation results also show that however, the authors proposed protocols impose much lower communication overhead, they either outperform or act closely to the existing cooperative protocols in the outage probability.

In automatic retransmission request (ARQ) based systems, L time retransmissions are allowed. The achieved performance of such systems is closely related to the channel dynamics during different retransmissions. In this paper, we present a generalized dynamic channel model which covers both long term, and short term static channel as the special cases. We then analyze the diversity multiplexing trade off (DMT) for ARQ based non cooperative communication and ARQ based opportunistic cooperative communication (OCC) over Nakagami-m channels. The analysis in this paper studies the impact of channel dynamics on the DMT performance for non cooperative and cooperative systems. In the analysis we consider two non cooperative communication systems including random user selection (RUS), and best user selection (BUS). We show that depending on channel dynamic conditions, while all the studied schemes enjoy the time diversity gain, BUS exploits multi-user diversity gain in its DMT performance. Also, DMT performance of OCC is significantly high due to cooperative diversity gain. In particular, we show that for RUS and OCC, as the channel dynamics conditions are changing from long term to short term. The DMT performance is significantly improved until the performance is maximized in the case of short term static channels, however, this DMT behavior is different for BUS. Two retransmission approaches including packet combining (PC) and packet accumulating (PA) are also studied and their impacts on DMT performance are analyzed for cooperative and non-cooperative schemes.

In this paper, we analyze the outage probability of coded cooperation in opportunistic relaying (OR-CC) and distributed space-time coding (DSTC-CC) cooperative communication systems at arbitrary signal to noise ratios (SNRs) and number of available relays assuming Rayleigh fading channels. Furthermore, we obtain lower and upaper bounds for the diversity multiplexing tradeoff (DMT) for OR-CC and DSTC-CC schemes in the cases where the source node is/is not included in the cooperation. Simulation results confirm our analysis.