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In this paper, an adaptive tone reservation technique with optimal subcarrier allocation awareness for multi-user OFDMA systems is investigated. In general, a variety of approaches have been proposed to cope with the PAPR problem in OFDM systems. A tone reservation (TR) is an effective technique for reducing PAPR, in which it does not need to transmit any side information and there is no distortion...
Resource (power and bandwidth) allocation is an important issue in orthogonal frequency division multiple access (OFDMA) systems. For multi-cell systems, the interference across different cells makes the optimization of resource allocation difficult. Large system analysis is applied for multi-cell OFDMA systems with the fairness constraint of equal grade of service (EGOS). An interference function...
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 deals with relaying techniques in WiMAX communication system. Different cooperative and non-cooperative schemes are investigated and compared over a complete 802.16 WiMAX-OFDM chain. Realistic channel impulse responses are used. Measurement of some propagation conditions feeds the WINNER channel model in order to generate the channel coefficients belonging to different links. Besides, real...
A data terminal seeks the optimal power allocation for M sub-carriers under a general concave performance function (??capacity??), and a per-Watt price. The value to the terminal of one transferred information bit, as well as the noise-normalised channel gains for each sub-carrier are the critical parameters. We provide the structure of the general solution, and give closed-form expressions for the...
Energy efficiency is becoming increasingly important for small form factor mobile devices, as battery technology has not kept up with the growing requirements stemming from ubiquitous multimedia applications. This paper addresses link adaptive transmission for maximizing energy efficiency, as measured by the "throughput per Joule" metric. In contrast to the existing water-filling power allocation...
Linear precoding (LP) technique applied to OFDM systems has already proved its ability to significantly increase the system throughput in a powerline communication (PLC) context. In this paper, we propose resource allocation algorithms based on the LP technique to increase the multicast OFDM systems bit rate. The conventional multicast capacity is limited by the user which experiences the worst channel...
We evaluate a dual-hop OFDM relay system with non-regenerative relay without FFT/IFFT processes at the relay node to reduce the processing delay and the complexity of the relay process in terms of the achievable rate and throughput. To maximize the achievable rate, we propose a power allocation scheme to each subcarrier of the source node and the whole subcarrier of the relay node. Due to the flexible...
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...
The bit loading algorithms are proposed for orthogonal frequency division multiplexing (OFDM) and linear pre- coded OFDM under power spectral density and mean bit error rate (BER) constraints. These algorithms maximize the bit rate of the system while respecting a mean BER. The advantages of both linear procoded OFDM and classical OFDM are analyzed under different scenarios. It is shown that the proposed...
For a single user with multiple receive antennas, co-antenna interference can be the dominant source of impairment in a Spatial Multiplex Orthogonal Frequency Division Multiple Access (SM-OFDMA) system, particularly when correlation exists between spatial sub-channels. By exploiting knowledge of the channel response and combining it with Dynamic Sub- Carrier Allocation (DSA), the algorithm proposed...
This paper introduces a new method for distributed interference mitigation in full spectral-reuse OFDMA cellular networks. This considers the use of pre-defined frequency-domain power profiles helping make the interference more predictable across the subcarriers. We propose a method for computing the power profiles so as to maximize the capacity of the system in case of maximum throughput scheduling,...
We consider an OFDM (orthogonal frequency division multiplexing) point to point transmission scheme improved by means of multiple relays. For each carrier, symbols sent by the source during a first time slot, may be retransmitted during a second time slot by the relays, which are assumed to be of the decode-and-forward (DF) type. For each relayed carrier the destination implements maximum ratio combining...
We investigate downlink resource allocation for OFDM-based cognitive radio networks. It is assumed that secondary users are allowed to transmit on all subchannels as long as the interference they create for primary users remains below a critical threshold. We consider a practical setting where secondary users have finite queue backlogs and a total power constraint at the base station and we perform...
This paper addresses the subcarrier and power allocation problem in the uplink of an OFDMA system under the cognitive radio environment. The objective is to maximize the sum-rate of secondary users, without causing adverse interference to the primary users. We formulate the optimization problem subject to the individual power constraints and the interference constraints. Since the problem cannot be...
In this paper, we consider the dynamic subchannel allocation problem in OFDMA-based selective relaying networks. Our goal is to maximize the total throughput under the constraint of total transmission power, while guaranteeing fairness on subchannel occupation by multiple destination nodes (users). Since the optimal solution to this optimization problem is extremely computationally complex to obtain,...
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...
A two-hop relaying system where a source communicates with its destination through multiple relay nodes is studied for capacity maximization. Amplify-and-forward (AF) relaying is adopted for its simplicity. Taking the independent channel transfer function of different subcarriers and links into consideration, we formulate a resource allocation optimization problem for joint subcarrier assignment,...
In cognitive radio networks with the coexistence of primary and secondary users, the problem of how to optimally allocate available resources (e.g., bandwidth and power) to multicast groups of secondary users that use orthogonal frequency division multiplexing (OFDM) is important. Taking the maximization of the weighted sum rate of such groups as the design objective, we propose a practically optimal...
Network coding has been leveraged with cooperative diversity to improve performance in single channel wireless networks. However, it is not clear how network coding based cooperative diversity can be exploited effectively in multi-channel networks where overhearing is not readily available. Moreover, the question of how to practically realize the promising gains available, including multi-user diversity,...
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