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Due to the AMC (Adaptive Modulation and Coding) mechanism adopted in the 802.16e physical layer, each connection's spectrum requirements depend on its SNR (Signal-to-Noise Ratio). Meanwhile, according to the OFDMA functionality, the limited transmission power of every terminal is divided among the simultaneously allocated subcarriers, i.e. a terminal's uplink SNR is reversely proportional to the number...
Orthogonal frequency-division multiple access (OFDMA) exploits the frequency selective property of a wireless communication channel by allocating subchannels to individual users. Conventional multicast systems, however, suffer from diversified channel conditions among users. The main contribution of this paper is to maximize the multicast rate of one multicast session while being fair among users...
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...
In this paper an adaptive resource allocation algorithm in OFDMA based cognitive radio (CR) system is proposed that not only meets the quality of service (QoS) of real-time (RT) services but also increases the dynamic capacity of the system. In contrast to existing algorithms for multi-user OFDM systems which are unable to guarantee maximum sum data rate when applied to CR system in real-time, the...
This paper proposed a novel bit and power allocation algorithm for OFDMA systems. Compared with previous schemes, the proposed algorithm is considered with two different stages to improve the bit and power allocation algorithm performance instead of traditional one stage. Two different stages proposed in this paper include RLB algorithm and B-Tighten algorithm. The numeric results show this algorithm...
This paper presents the novel resource allocation scheme for multiclass services in the downlink OFDMA system, in which the frame-based transmission with multiple subchannels and multiple time slots is used. As system utilization and fairness are necessary, the scheme is based on proportional fairness (PF) utility function. Two main service classes are considered. One is the guaranteed service class...
Orthogonal frequency division multiple access (OFDMA) is an efficient access technique that allocates different subcarriers to multiple users where each subcarrier is loaded with a number of bits belonging to that user. Allocating subcarriers and bits to multiple users has been the focus of many algorithms that attempt to maximize the throughput or minimize the total transmit power used. Non-real...
Because of bursty high data rate and delay sensitive nature of high quality multimedia application, the resource allocation in wireless network to meet its quality of service (QoS) has become the most challenging and interesting issue. Orthogonal Frequency Division Multiple Access (OFDMA) employing adaptive channel allocation technique can support these requirement while increasing the system capacity...
In this paper a new prioritization function for Orthogonal Frequency Division Multiple Access (OFDMA) is proposed where the resource allocation problem is divided in two phases, minimum requirements satisfaction, and spectral efficiency maximization. For each phase a different prioritization function is considered. The performance of the proposal is evaluated, via computer simulation, by the packet...
This paper studies the resource allocation problem for the relay-assisted orthogonal frequency-division multiple-access (OFDMA)-based multiuser system. A new transmission protocol, named hierarchicalOFDMA, is proposed to support two-way communications between the base station (BS) and each mobile user (MU) with or without an assisting relay station (RS) in ldquorelayrdquo or ldquodirectrdquo mode,...
Cellular communication systems need to support simultaneous transmission of multiple data rates over the same medium. A major aspect of design of cellular systems is simultaneous sharing of channel resources avoiding multiple access interference between users. For high quality communication this must be done without severe degradation in performance of the system. Orthogonal frequency division multiple...
Orthogonal frequency division multiple access (OFDMA) is an emerging multiple access technology. In this paper, we focus on the packet scheduling problems of the downlink of OFDMA wireless systems with delay requirements. We revised three different scheduling methods in order to reduce their complexity for practical application based on limited feedback. Furthermore, we simulate these algorithms under...
This paper proposes a novel Frequency Time scheduler, called Frequency Time Scheduler with Delay Constraints (FTSDC), in order to handle streaming traffic in OFDMA (Orthogonal Frequency Division Multiple Access) system. Streaming technique, widely developed and used in the internet to convey multimedia application (e.g., audio, video clip, etc.), is supposed to occupy a large share of bandwidth in...
Adaptive radio resource allocation mechanisms exploiting the inherent frequency selectivity of the wireless medium as well as the multi-user effect are expected to play a key role in emerging next generation OFDMA-based wireless networks. Although a plethora of studies concerning either constant/guaranteed bit rate (CBR/GBR) or variable bit rate/best effort (VBR/BE) traffic has been published to date,...
In this paper, we propose an algorithm for dynamic resource allocation in OFDM (orthogonal frequency division multiplexing) or OFDMA (OFD multiple access) based networks. We consider two groups of users consisting of group 1 called constant bit-rate (CBR) users (who are delay-sensitive and data-rate sensitive) and group 2 called best effort (BE) users. The proposed algorithm gives higher priority...
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