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In OFDMA-based Cognitive Radio (CR) systems, how to deal with the time-varying nature of avaliliable spectrum resources has become a hotspot and challenging problem in resource allocation. Traditional resource allocation algorithm can not guarantee proportional rates among non-real-time CR user (CRU) because the number of available subchannels is smaller than the number of CRUs in some OFDM symbol...
We consider the allocation of spectral and power resources every subframe (1~ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be a function of the sub-band. Moreover, the channel gains from the base-station...
Recently, the OFDM-based Spectrum-sliced Elastic Optical Path (SLICE) network attracts significant interests due to its elastic band-width allocation. The OFDM technology, on one hand, enables both sub-wavelength and super-wavelength traffic accommodation by allocating appropriate number of sub-carriers. On the other hand, it can provide high signal quality by overcoming various impairments. In SLICE...
This paper studies the cooperative interference control in a two-cell downlink OFDMA system, which can be modeled as an interfering broadcast channel. It is assumed that each cell can simultaneously access the same frequency band, which corresponds to a universal frequency-reuse in cellular systems. We study the joint power and subcarrier allocation over the two cells to maximize their sum throughput...
In this paper, we propose a dynamic power allocation scheme for a single-relay network based on orthogonal frequency division multiplexing (OFDM) modulation with limited feedback.We consider an Amplify-and-Forward (AF) cooperative diversity model, where one source node communicates with one destination node assisted by one half duplex relay. The power allocation scheme employs a codebook of quantized...
In this paper, joint optimization of subcarrier pairing, relay selection and power allocation is formulated through a capacity maximization problem in orthogonal frequency division multiplexing (OFDM) relay systems, with fairness considerations and individual power constraint on each node. Because achieving the optimal solution is computationally demanding, which is resulted from the excessive possibilities...
In this paper we propose framework for energy efficient (margin adaptive, MA) resource allocation in multiuser SC-FDMA under synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. To limit the impact of retransmissions on the time-frequency problem segmentation, we propose use of a block scheduling interval that...
Support of non-contiguous frequency resource allocation (FRA) based on clustered discrete Fourier transform-spread orthogonal frequency division multiplexing (clustered DFT-S-OFDM) is considered a key element of LTE-Advanced uplink to enhance the spectrum efficiency via an enhanced frequency domain scheduling. However, reduction of out-of-band emissions due to multiple clusters is a critical issue...
Providing physical-layer security for mobile users in future broadband wireless networks is of both theoretical and practical importance. In this paper, we formulate an analytical framework for resource allocation in a downlink OFDMA-based broadband network with coexistence of secure users (SU) and normal users (NU). The problem is formulated as joint power and subcarrier allocation with the objective...
This paper proposes an adaptive fractional frequency reuse (FFR) resource allocation scheme for downlink transmission of OFDMA cellular networks. Resource allocation is localized in the sense that in each region system resources are assigned based on local traffic demand. Furthermore, the allocated resources in each region adapt to changes in the environment (i.e. channel gains and number/mobility...
This paper investigates the user and channel diversity in OFDMA wireless systems with network coding. In particular, the paper introduces an adaptive resource allocation scheme to minimize the total transmit power while maintaining a required end-to-end BER. The proposed adaptive sub-carrier allocation scheme de-couples the bit loading of the network coded OFDMA system into three independent bit loadings...
We address the problem of designing efficient resource allocation schemes for an OFDMA based multiuser cooperative communication system that uses amplify and forward relaying. With a two-phase relaying protocol, we assume that both source and the relay have fixed power constraints and that the source employs a selective relaying mechanism. That is, the source adaptively decides on which frequency...
This paper considers a multi-source orthogonal frequency division multiplexing (OFDM)-based network of access points wherein dedicated relays use the decode-and-forward relaying. We investigate the joint problem of transmission strategy selection (relaying v/s direct), relay assignment, and power allocation to maximize the minimum rate across sources in two different cooperative scenarios: subcarrier-based...
This paper proposes a strategy that combines user pairing and spectrum allocation for a virtual multiple-input multiple-output (V-MIMO) single-carrier frequency-division multiple access (SC-FDMA) transmission over intersymbol interference (ISI) channels. The users are equipped with a single antenna each, where always two users, composing one pair, transmit their data in the same time slot and frequency...
Long Term Evolution (LTE) is considered one of the main candidate to provide wireless broadband access to mobile users. Among main LTE characteristics, flexibility and efficiency can be guaranteed by resorting to suitable resource allocation schemes, in particular by adopting adaptive OFDM schemes. This paper proposes a novel solution to the sub-carrier allocation problem for the LTE downlink that...
In this work we describe an optimization technique for multiuser resource allocation and adaptive modulation and coding (AMC) in OFDMA radio downlink communications. In particular, we propose an innovative AMC solution, based on M-QAM modulation and LDPC codes, jointly working with the scheduler and capable to maximize the achieved throughput while guaranteeing a given set of BER/FER requirements...
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