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In this study, we analyze the role of interleavers in OFDMA system for ensuring uniform BER performance amongst the active users and also investigate their respective PAPR properties. At first considering a generic system in a slowly changing multipath channel where high dispersion in the individual users performance exists, we apply different types of interleaving and show that they in general help...
In OFDMA, the subcarrier allocation process amongst the users has a significant role in governing the performance of the system. In this paper, we study the application of interleaver based subcarrier allocation schemes for ensuring uniform BER across all the active users. We show that for a slowly changing multipath channel, individual user's BER performance can vary from each other to a great extent,...
In this paper we address the challenge of multiuser scheduling in the downlink of 3GPP UMTS/LTE. Long Term Evolution (LTE) imposes the constraint of using the same code rate, modulation order and transmit power for all resources a User Equipment (UE) is scheduled onto. This, in addition to the lack of channel knowledge, prohibits theoretical concepts such as capacity maximization to be applied for...
In this paper, a linearly coded (LC) relaying scheme is proposed for multiuser relay network in which a number of users communicate simultaneously with a common destination with the help of one relay node, by using orthogonal frequency division multiple access (OFDMA). The proposed linear coding at the relay node enables exploiting the frequency diversity in the relay-to-destination (R-to-D) link...
We propose a strategy that optimally schedules and allocates users for adaptive modulation and coding based orthogonal frequency multiple access systems (AMC-OFDMA). This strategy aims to maximize the average system throughput as a function of bit error rate (BER) and spectral efficiency by exploiting the user diversity. It sorts the available users of an assigned base station (BS) in queues based...
In a Multiple Input Multiple Output (MIMO) architecture, self-interference becomes the dominant source of impairment, particularly when correlation exists between spatial sub-channels. This paper aims to minimize the effect of self-interference by means of dynamic subcarrier allocation (DSA) and exploiting the knowledge of spatial sub-channel `quality' evaluated by an ESINR metric. The proposed system...
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...
Resources allocation of OFDM system is a key factor that affects system performance. Parteek Bansal proposed a bit-power allocation algorithm under different bit error rate (BER). But the process of its bit allocation will cause high complexity and bad real-time to build a power-increment table. In this paper, a low-complexity multi-user subcarrier-bit-power allocation algorithm for wireless OFDMA...
This paper investigates the allocation of subcarriers and power in the downlink channels of multiuser OFDM systems. The goal is to minimize the total transmit power under the constraints of user data rates and bit error rate (BER). We propose a sub-optimal algorithm to achieve the goal in this paper. We introduce a new factor which is the gain difference between the maximum and the next maximum userspsila...
Orthogonal frequency division multiple access (OFDMA) has been used for broadband wireless multiple access. The performance of OFDMA system can be improved by using multiple antennas with space time coding to get transmit and receive diversity. Channel information estimated at receiver for space time decoding can be used for sub-channels allocation at transmitter. In this paper, we propose a method...
Opportunistic resource allocation in orthogonal frequency division multiple access (OFDMA) with limited feedback improves the performance of wireless networks and it has been considered in several studies. However, the performances of reduced feedback schemes have not been characterized analytically. In this paper, the analysis of the resource allocation in downlink OFDMA with limited feedback is...
We consider the uplink of a multi-cell orthogonal frequency division multiple access (OFDMA) system that employs multiple (M > 1) receive antennas and maximum ratio combining at the base station. We propose a model that captures the impact of intercell interference coordination on the modulation and coding scheme dependent bit error rate (BER) performance. We analyze this model in two steps. First,...
This paper proposes a cooperative game theoretic resource allocation scheme for downlink OFDMA wireless networks. We define a user??s payoff as a function of his data throughput. Then the source allocation can be modeled as a cooperative game to maximize the aggregate payoff of the users. To achieve the Nash bargaining solution (NBS) of the game, a suboptimal subcarrier allocation is first performed...
We address the problem of resource allocation on an OFDMA downlink under fairness constraints with limited channel state information (CSI). Target QoS corresponds to a minimum user data rate, a target bit-error rate and a maximum outage probability. The only available CSI is the channel average gain of each user. This partial CSI can be viewed as a shadowed pathloss that yields a modified user distribution...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
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