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This paper presents a novel resource allocation procedure for OFDMA downlinks, which stems from an hybridization of the Harmony Search and the Differential Evolution heuristic algorithms. In this setup it is known that optimum subcarrier and power allocation is achieved through 1) assigning each subcarrier to the user with highest channel gain at the given frequency, and 2) a Water-Filling procedure...
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...
In cognitive radio settings with highly dynamic primary activities and with small opportunities for secondary access, the requirement to fairly distribute the temporarily available spectral ranges among the unlicensed users turns out to be of particular relevance. The current paper addresses this issue by presenting a new design formulation that aims to optimize the performance of an orthogonal-frequency-division-multiple-access...
In this paper, we propose a distributed adaptive interference coordination algorithm for a practical orthogonal frequency division multiple access (OFDMA)-based mobile cellular systems. The designed algorithm can achieve an efficient frequency reuse for any user distribution and traffic load. Since no a priori frequency planning is required, the minimal coordination between base stations is also achieved...
Fractional Frequency Reuse (FFR) is one of the key concepts for mitigating inter-cell interference and improving cell-edge performance in OFDMA networks. The standard FFR scheme is intuitive and optimal for the hexagon-shaped cell pattern. In contrast, real-life OFDMA systems have very irregular cell layout, thus the number of surrounding cells and their respective interference vary significantly...
In this paper, we consider the problem of resource allocation in relay aided uplink multi-user transmission with a single destination node. We adopt the amplify-and-forward (AF) relaying scheme and the orthogonal frequency division multiple access (OFDMA) as the main transmission modulation. The optimization is formulated as maximizing the end-to-end system throughput subject to limited number of...
This work addresses the application of the cross-layer paradigm to the design of efficient resource allocation algorithms for the downlink of a MIMO-OFDMA system with a physical layer employing optimal single-stream/single-user linear precoding. Mathematical programming tools are used to solve the problem of weighted throughput maximization using both channel state information from the physical layer...
We investigate the problem of multi-user radio resource allocation for orthogonal frequency division multiple access (OFDMA) amplify-and-forward (AF) relays. In the single-user case, the problem reduces to the well know assignment problem, which maximizes the user rate. For the multi-user case we devise a resource allocation algorithm to achieve max-min fairness. We find max-min fairness since it...
Reducing the consumed energy in wireless communication systems has a direct impact on operational expenditure as well as CO2 emissions. With increasing interest in multimedia applications and high data rate services, environmentally sustainable communications networks must reduce the energy per delivered bit at an equal rate, if not better. This paper addresses downlink energy-efficient transmission...
We consider wireless telecommunications systems with orthogonal frequency bands, where each band is referred to as a channel, e.g., orthogonal frequency-division multiple access (OFDMA). For a given snap-shot in time, two joint channel assignment and power allocation optimization problems are presented, one in downlink and one in uplink. The objective is to maximize the minimum total Shannon capacity...
This paper focuses on the problem of maximizing the system utility for real-time services in OFDMA cellular systems. We evaluate the upper bound for the global maximum of the system utility, whose actual value is very difficult to obtain when the utility functions are not concave. A linear programming based resource allocation algorithm is proposed to approach the bound, and a priority-based resource...
In this paper, we investigate resource allocation issue in OFDMA-based decode-and-forward cooperative networks and propose joint subcarrier and power allocation schemes. The optimal solution of this combinable allocation has high computational complexity, so we divide our solution into two steps. The first step is to distribute subcarriers to relays and destination under the assumption of equal power...
Providing ubiquitous very high data rate coverage in next generation wireless networks is a formidable goal, requiring cost-effective radio access network (RAN) devices, such as multi-user enabled amplify- and-forward (AF) relays, and fair radio resource management (RRM). To further this goal, we investigate multi-user enabled AF relays which multiplex user's data in orthogonal frequency division...
Frequency reuse is a key concept for interference mitigation and thereby enhancing cell-edge performance in OFDMA networks. Two representative strategies are Fractional Frequency Reuse (FFR) and Soft Frequency Reuse (SFR). Both divide a cell into a center zone and an edge zone, and differentiate their levels of frequency reuse. Previous work on FFR and SFR has focused on networks of relatively small...
This paper focuses on the adaptive resource allocation strategies for two-hop multiuser OFDMA nonregenerative relay networks considering both maximization of total throughput and fairness constraints among users. First, an optimal resource allocation scheme to maximize the overall data rate is developed with separate transmit power constraints both at source and relay nodes. An alternative scheme...
In this paper, we propose a new adaptive subcarrier allocation for a multiuser two-way OFDMA relay network. In the proposed algorithm, subcarriers are allocated to the user-pairs and relays to maximize the achievable sum-rate over all user-pairs while satisfying the minimum rate requirement for each user-pair. Simulation results show that the proposed algorithm improves spectral efficiency and fairness.
In this paper, we study the resource allocation problem in relay aided two-hop uplink multi-user transmission with a single relay node and a single destination node. The orthogonal frequency division multiple access (OFDMA) is adopted as the main transmission modulation. We investigate the problems of subcarrier allocation, subcarrier coupling, and power allocation. The optimization is formulated...
In this paper we extend the base station (BS) assignment problem to incorporate backhaul related constraints into the assignment decision. This is motivated by the fact that the deployment of more spectral efficient radio access technologies are currently imposing stringent bandwidth requirements at cell sites, and there is a growing concern that backhaul network can become a new network bottleneck...
Fractional Frequency Reuse (FFR) is one of the key concepts for enhancing cell-edge performance of OFDMA networks. Standard FFR allows one sub-band to be allocated for each cell. This limits the performance improvement of cell edge users, especially those bandwidth-sensitive users. With flexible sub-band allocation, cell edge can be allocated more than one sub-band, thereby performance can be improved...
In this paper, the problem of wireless resource allocation in OFDMA-based cognitive cooperative network is investigated. The objective is maximizing the throughput of primary users in a system in which cognitive users act as a relay for primary users. In our proposed scheme, while primary users achieved desire rate, they dedicate some subcarrier for cognitive users. We propose two different algorithms...
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