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In recent decades, due to limitation of radio spectrum and increasing users in wireless networks, spectral efficiency has been a considerable issue in literatures. In addition, energy consumption is rapidly increasing in wireless communications due to growing demand for wireless technologies especially cellular networks. Therefore, energy efficiency has become an important issue in such networks....
In this paper, we study an opportunistic subchannel scheduling problem for the relay-based OFDMA cellular network where relay stations (RSs) can perform opportunistic network coding with downlink and uplink sessions of a mobile station (MS). In wireless networks, network coding is one of promising techniques to improve network performance in various aspects. However, previous studies did not provide...
We consider subcarrier assignment and power allocation in OFDMA wireless mesh networks. Traditional full spatial reuse increases bandwidth efficiency but ignores multiuser diversity in the multi-hop network. Our method enables fractional spatial reuse with which multiuser diversity can also be exploited. The original optimization problem is decomposed into three tractable subproblems. First, subcarrier...
In this paper, we develop a distributed sub-carrier allocation algorithm with a low complexity in OFDMA multi-cell system , which is decomposed into two sub-problems: inter-cell and intra-cell sub-carrier allocation. During inter-cell process, based on time-variant characteristics and performance differ-ences among cells of sub-carriers, each base station applies Ant Colony Optimization (ACO) to choose...
Adaptive resource allocation has been shown to provide performance gain for OFDMA wireless mesh networks (WMNs) with full channel state information (CSI) at mesh router (MR) and mesh clients (MCs). However, full CSI at MR is rarely possible due to limited feedback resource and feedback delay. In this paper, we present more practical resource allocation strategies for OFDMA WMNs where the MR has only...
In this paper, the inter-cell interference coordination (ICIC) is investigated for the downlink transmission in OFDMA-based multi-cellular systems. The utility function is introduced to balance efficiency and fairness. Firstly, the system model is built based on the resource allocation rules of soft frequency reuse (SFR) and the utility-based optimization problem is formulated. Secondly, the problem...
The problem of resource allocation (RA) in a downlink OFDMA system with minimum user rate requests is examined under the realistic scenario of partial (imperfect) channel state information (CSI) at the base station. The challenge in this setting is the non-zero probability of outage events which may lead to significant performance degradation if algorithms assuming perfect CSI are utilized. In this...
We address an opportunistic subchannel scheduling problem in relay-based OFDMA cellular networks. In most previous works on relay-based cellular networks, immediate relaying at relay stations (RSs) was assumed, without allowing the opportunistic scheduling at RSs. Hence, each RS should transmit the received data from the base station (BS) to the corresponding mobile stations (MSs) immediately within...
Uplink ergodic sum-rate maximization in OFDMA systems is considered. The general problem is formulated as a convex optimization problem and a dual solution is presented. The problem formulation is generalized to the case of utility maximization where the utility can be any function of rate. A suboptimal scheduling algorithm with low complexity is proposed and shown to achieve close performance to...
This paper investigates the problem of multiuser packet scheduling and resource allocation for video transmission over downlink OFDMA networks. A cross-layer optimization function is proposed with the goal to maximize the received video quality. Unlike the previous methods in which the objective function is estimated the video quality in the unit of bit, the proposed algorithm develop the objective...
This paper considers subcarrier allocation for the multihop orthogonal frequency division multiple-access (OFDMA) broadcast networks consisting of one source, multiple destinations, and one amplify-and-forward (AF) relay. In this paper, proportional fair (PF) based subcarrier allocation is discussed to get a tradeoff between the system transmission rate and fairness. First, the problem is formulated...
In this paper, we study an opportunistic power scheduling problem in relay-based OFDMA cellular networks. In most previous works on relay-based cellular networks, scheduling at relay stations (RSs) is not allowed. Hence, each RS should immediately transmit all the received data from the base station (BS) in the first phase in a time-slot to mobile stations (MSs) in the second phase in the same time-slot...
In this paper, an efficient scheme to optimize resource allocation for dynamic OFDMA based WiMAX systems is presented, which provides priority estimated resource allocation with individual QoS provisioning. Our proposed scheme dynamically assigns OFDMA resources to the users to optimize the overall system performance in heterogeneous traffic and diverse QoS based WiMAX systems. To achieve this goal,...
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