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In future fourth generation wireless networks OFDM and MIMO techniques will be heavily exploited to provide connectivity to heterogeneous users offering different data traffic types. This paper proposes a low complexity resource allocation strategy for MIMO-OFDMA (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiple Access) broadcast channel to support delay-sensitive traffic with...
We propose an adaptive bit and power allocation technique for an orthogonal frequency division multiple access based cognitive radio network. The resources are allocated such that each secondary user attains equal data rate while ensuring the interference leakage to the primary users is below a specific threshold. Integer linear programming based optimal algorithm and a suboptimal method based on...
The resource allocation optimization for multicast service in orthogonal frequency division multiple access (OFDMA) systems is an important research topic. It is known that in traditional multicast schemes the rate in each multicast group is severely limited by the user who has the minimum channel gain (MCG) on each subchannel. To counteract this effect, in this paper, we introduce the multiple description...
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...
Energy efficiency is increasingly important for wireless cellular systems due to the limited battery resources of mobile clients. While modern cellular standards emphasize low client battery consumption, existing techniques do not explicitly focus on reducing power that is consumed when a client is actively communicating with the network. Based on high data rate demands of modern multimedia applications,...
In this paper, a new planning method is proposed for the next generation wireless networks that are based on Orthogonal Frequency Division Multiple Access (OFDMA). As a consequence of the wide variety service demands in terms of data rate and Quality of Service (QoS), the traffic pattern is considered to be heterogeneous. Therefore, the complexity of obtaining Base Stations (BSs) positions increases...
In this paper, we study resource allocation and relay selection in a decode-and-forward downlink OFDMA cooperative network assuming imperfect channel state information (CSI) at the base station (BS). We assume that due to feedback delay, the BS has only outdated CSI of BS to users and inter-user links. We propose a centralized optimization framework in which the BS takes decisions on the basis of...
This paper deals with dynamic resource allocation problem for OFDMA-based cognitive radio systems. The proposed solution is specifically tailored for a secondary base stations (SBS) transmitting to secondary users (SUs) over the same bands of the licensed primary users (PUs) in underlay fashion. The downlink transmission goodput is thereby maximized while keeping the interference on the PUs within...
Most existing works on resource allocation in cooperative OFDMA systems have focused on homogeneous users with same service and demand. In this paper, we focus on resource allocation in a service differentiated cooperative OFDMA system where each user has individual QoS requirement. We investigate joint power allocation, relay selection and subcarrier assignment to maximize overall system rates with...
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 focus on the subcarrier allocation for the uplink OFDMA based cooperative relay networks. Multiple cells were considered, each composed of a single base station (destination), multiple amplify and forward (AF) relay stations and multiple subscriber stations (sources). The effects of inter-cell interference (ICI) have been considered to optimize the subcarrier allocation with low complexity...
Recently, a cooperative paradigm for single-channel cognitive radio networks has been advocated, where primary users can leverage secondary users to relay their traffic. However, it is not clear how such cooperation can be exploited in multi-channel networks effectively. Conventional cooperation entails that data on one channel has to be relayed on exactly the same channel, which is inefficient in...
This letter addresses the problem of subcarrier and power allocation over an OFDMA system with multiple power constraints. Each power constraint is related to sharing a power resource by a subset of users. Here, a framework based on time-sharing method is proposed that allows for approaching the optimum solution via using a low complexity iterative algorithm. The provided solution sets an upper bound...
We consider a downlink OFDMA transmission system in which an infrastructure-based relay node is deployed for extending the coverage of a base station. Focusing on decode-and-forward (DF) operation, we study how different relay functionalities affect the system performance. The functionalities include fixed or adaptive subcarrier pairing, information redistribution, buffering, and adjustment of the...
The provision of very high data rates in a ubiquitous and fair manner throughout the service area is a great challenge for 4G and beyond-4G wireless networks. Towards that end, the deployment of fixed relays by the operators has become an accepted radio access network concept in various standardization activities including LTE-A and 802.16m. In this paper, we present a fair resource allocation scheme...
This paper discusses on the fair resource allocation in OFDMA two-hop cooperative relaying cellular networks which consist of a single base station (BS), dedicated fixed relay stations (RSs) and user stations (USs). By assuming the relay strategy employed on each subcarrier is adaptively selected among direct transmission, amplify-and-forward (AF) and decode-and-forward (DF) according to different...
We consider the multi-user discrete bit loading problem in OFDMA systems with objective and constraints in terms of ergodic rates and powers. This differs from most existing techniques, which allocate rate and power according to instantaneous constraints and channel conditions. The maximum weighted ergodic sum-rate optimization problem is non-convex in general, but a dual decomposition results in...
In this paper, we investigate efficient scheduling algorithms in OFDMA multihop relaying networks. The scheduling scheme is modeled as a multiple objective programming problem to maximize the overall capacity and the number of satisfied users under the minimum rate constraint per user. An improved priority (IPRI) algorithm is exploited with novel opportunistic function, which relies on capacity gain,...
Adaptive resource allocation including the allocation of subcarrier, bit and power in orthogonal frequency division multiple access (OFDMA) system, can significantly improve spectral efficiency, increase capacity, and reduce power consumption. The resource allocation in an OFDMA system is normally modeled as a combinatorial optimization problem involving a nonlinear objective with nonlinear constraints...
This paper studies resource allocation problem in downlink multiuser orthogonal frequency division multiple access (OFDMA) system. The problem is formulated as sum-rate (cell throughput) maximization problem with strict data rate constraints imposed by the users and peak power constraint by the base station. We discuss the feasibility of the problem and propose two algorithms when the feasibility...
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