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OFDMA femtocells are generally accepted as a very promising solution for indoor coverage with high data rate. However, the lack of systematic schemes to effectively mitigate macro/femtocell hierarchical interference, fully utilize radio resources, provide quality-of-service (QoS) and fairness guarantee among users suffocate the performance realization of femtocells. In this paper, an Adapted Soft...
In this paper, a cellular optical wireless communication system based on orthogonal frequency division multiplexing (OFDM) is simulated inside an aircraft cabin. Asymmetrically clipped optical OFDM (ACO-OFDM) and direct-current-biased optical OFDM (DCO-OFDM) transmission schemes are compared in terms of throughput and cell coverage. Cellular networks with wavelength reuse factors of 1 (full reuse),...
Fractional frequency reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This work focuses on evaluating the two main types of FFR deployments: Strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed, including outage probability, network throughput,...
Efficient spectrum sensing ensures cognitive radio users opportunistically use the under-utilized frequency band without causing harmful interference to primary users. However, in practice, owing to the non-zero probability of the missed detection and false alarm of active primary transmission, a certain degree of performance degradation of the primary user is unavoidable. In this paper, we consider...
Fractional Frequency Reuse (FFR) is one of the key concepts for mitigating inter-cell interference and improving cell-edge performance in OFDMA networks. The standard FFR scheme is intuitive and optimal for the hexagon-shaped cell pattern. In contrast, real-life OFDMA systems have very irregular cell layout, thus the number of surrounding cells and their respective interference vary significantly...
This paper focuses on coordinated scheduling to combat uplink inter-cell interference for LTE/LTE-Advanced. In OFDM system, inter-cell interference is the dominant interference which limits system capacity, especially the performance of cell edge users. Meanwhile inter-cell interference in OFDM system has an inherent characteristic of interference fluctuation, which reduces the efficiency of channel...
This paper describes the optimization of the frequency allocation in the downlink of an Orthogonal Frequency Division Multiple Access (OFDMA) cellular network by means of centralized adaptive frequency management. The adaptive frequency allocation is performed off-line based on a Genetic Algorithm (GA) which computes for each cell an optimal number of radio resource blocks as guided by the geometry...
Femtocell is one of promising key technologies to increase the efficiency and coverage of next generation broadband wireless networks. However, there exists interference problem between femtocells and macrocell due to co-channel operation. In this paper, we propose an efficient frequency resource allocation scheme for newly deployed femtocells in the legacy OFDMA networks in order to maximize the...
Fractional Frequency Reuse (FFR) is one of the key concepts for enhancing cell-edge performance of OFDMA networks. Standard FFR allows one sub-band to be allocated for each cell. This limits the performance improvement of cell edge users, especially those bandwidth-sensitive users. With flexible sub-band allocation, cell edge can be allocated more than one sub-band, thereby performance can be improved...
Fractional frequency reuse (FFR) is one of the key concepts for interference mitigation in OFDMA networks. Previous work on FFR has focused on networks of relatively small size and standard hexagon-shaped cell layout. For real-life networks with very irregular cell layout and high variation in radio propagation, standard reuse schemes (e.g., reuse with a factor three) are inadequate; applying a standard...
A unique frequency reuse scheme by means of cell sectorization is proposed in this paper that reuses effectively a given frequency resource in a cellular environment. The key concept is to find a scheme that controls interferences among neighboring cells in a systematic manner while achieving high frequency reuse factor. Based on, user distribution in a cell, two problems are investigated. First,...
Femtocells are a promising solution for the provision of high indoor coverage and capacity. Furthermore, OFDMA-based femtocells have proven to be highly versatile when dealing with cross-layer co-channel interference thanks to the allocation of frequency subchannels. However, concerns still exist related to the impact of the different access methods to femtocells in an overlayed network. Femtocells...
We consider the sector capacity of an OFDMA data network, defined in terms of the number of users that can be supported while satisfying a minimum flow throughput requirement. A closed queueing network model to evaluate flow throughputs is extended to the case of reuse partitioning. The model is used to evaluate the sector capacity of reuse 1, fractional frequency reuse (FFR) and soft frequency reuse...
Mitigating Inter-cell Interference (ICI) and ensuring seamless high-quality communication are two challenging issues for OFDMA systems. Cell-level coordinated resource allocation and handover (HO) are the two key technologies for achieving these goals. They have been investigated intensively, however, mainly separately. In this paper, a novel combined Handover Guarantee and Interference Mitigation...
Soft frequency reuse (SFR) has been proposed for enhancing cell-edge performance in OFDMA networks. Previous studies of SFR have used simulations over rather small networks having hexagon-shaped cells. In this paper, we examine the expected performance gain of SFR for networks in realistic radio environments and with irregular cell patterns. We define a performance metric that allows for fast assessment...
A graph-based framework for dynamic fractional frequency reuse (FFR) in multi-cell OFDMA networks is proposed in this work. FFR is a promising resource allocation technique that can effectively mitigate inter-cell interference (ICI) in OFDMA networks. The proposed scheme enhances the conventional FFR by enabling adaptive spectral sharing per cell load conditions. Such adaptation has significant benefits...
Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMA/LTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally...
In order to avoid inter-cell interference, OFDMA networks are flexible in terms of radio resource management techniques, supporting different frequency reuse schemes (FRSs), which in turn, may decrease inter-cell interference and increase network performance. However, because most of them are based on fix patterns, these FRSs cannot cope with the uneven distribution and dynamic behavior of the traffic...
MIMO/OFDM is receiving considerable attention for next generation mobile radio communication systems. These systems require improved throughput performance to users at cell-edges. In our previous study, we introduced an enhancement of MLD (Maximum Likelihood signal Detection) algorithm, in which desired and interference signals are jointly detected, to improve the cell-edge throughput in the downlink...
In this paper we present an interference aware phased scheduling strategy for a soft frequency reuse (SFR) interference coordination scheme in an Orthogonal Frequency Division Multiple Access (OFDMA) network. It groups the active user terminals (UT) in a low and high signal-to-interference plus noise ratio (SINR) group and picks UTs from both groups in each scheduling round to optimally exploit the...
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