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Rapid growth in data traffic necessitates a proportional growth and improvement in the capacity of cellular networks. A heterogeneous network in which macro cells are overlaid with small cells is a cost efficient and effective paradigm shift for increasing the network traffic capacity. Unplanned deployment of low power base stations with divergent power levels introduces new challenges in heterogeneous...
Device-to-Device (D2D) communication underlaying cellular networks can enhance the network capacity and spectrum efficiency when sharing cellular resources. However, the severe interference between D2D and cellular networks may lead to performance decrease of D2D and cellular communication. In this paper, we concentrate on suppressing the interference between D2D users and cellular networks when D2D...
Femtocells are designed to cover a short range of area and improve the cellular system capacity in an economically viable way. In this paper, we propose an adaptive sub-band allocation (ASA) scheme for the downlink transmission of the LTE system, which consists of orthogonal sub-band assignment (OSA) algorithm and adaptive sub-band reuse (ASR) algorithm based on the interference graph. The interference...
Overlaying low-power, low-cost, femtocells, over existing wireless networks has recently emerged as a means to significantly improve the coverage and performance of next-generation wireless networks. While most existing literature focuses on spectrum sharing and interference management among non-cooperative femtocells, in this paper, we propose a novel cooperative model that enables the femtocells...
Uplink scheduling for relay stations in mobile multi-hop relay network has not been widely addressed in the literature under common belief that downlink traffic overwhelms uplink traffic. Recently, data traffic from user created content (UCC) is rapidly growing with a potential to create a huge amount of uplink (UL) traffic. Overlapped resource allocation in uplink transmission allows MSs attached...
We introduce a novel HetNet architecture employing fiber-connected distributed antenna systems, named broadband wireless access with fiber-connected massively distributed antennas (BWA-FMDA), which facilitates coordination of resource allocation and interference management. Among various opportunities realized by the proposed approach, our focus in this article is on CoMP for UMTS LTE femto- and picocells,...
The aggregate capacity of wireless mesh networks is severely affected by interflow interference. Directional antennas and multiple channels are two well known techniques which can be applied to mitigate interflow interference. In this work, a network architecture is proposed to incorporate directional antennas with multiple orthogonal channels effectively to enhance the performance of wireless mesh...
We study in this paper the resource allocation matter for unlicensed multiband ultra-wideband (UWB) users in the context of high-rate wireless personal area network (WPAN). The problem is viewed as a coexistence problem with existing licensed systems. The QoS support and the interference mitigation are jointly considered in this study to derive a novel interference power control mechanism that differentiates...
We establish a general optimization framework for joint resource allocation and interference mitigation. By utilizing axiomatic interference functions, our problem formulation is very general and includes many problems as special cases. We consider the sum rate maximization problem, which is known to be NP hard. It is shown that due to the structural model of the interference function, the joint optimization...
The femtocell concept is an emerging technology for deploying the next generation of the wireless networks, aiming at indoor coverage enhancement, increasing capacity, and offloading the overlay macrocell traffic. Nevertheless, the detrimental factor in such networks is co-channel interference between macrocells and femtocells, as well as among neighboring femtocells. This in turn can dramatically...
Femtocells applied in many existing systems, such as HSPA, 3GPP LTE, WiMAX, and etc, which cover a short range and offer an economically viable way to improve cellular system capacity, have caught world-wide researching interest nowadays. An interference coordination scheme is proposed for LTE downlink in this paper, which is split into three steps named as interference graph creation, orthogonal...
Interference mitigation and adaptive multi-user resource allocation are among the most promising technological breakthroughs that should improve capacity of future broadband wireless communications. In a multi-cell scenario, where co-channel interference is the performance limiting factor, discrete-rate resource allocation algorithms, selecting those channels with best Signal-to-Interference and Noise-Ratio...
The Physical Downlink Control Channel (PDCCH) is used to signal dynamic resource assignment information in the Long Term Evolution (LTE) system. In the presence of numerous active users, the system performance is likely to be hindered by shortage of control channel resource. In this paper, several simple algorithms are brought forward for making efficient PDCCH resource allocation. We first propose...
Block diagonalization is a linear precoding technique which eliminates the multi-user interference at the transmitter side by creating parallel orthogonal single user links. In this technique, the transmit diversity order is fixed for each user and only power can be controlled to satisfy SINR requirements. This restricts the degrees of freedom available for resource allocation and limits the energy...
In current cellular networks base stations (BSs) usually perform independent scheduling without coordinating the resource allocation among different cells. This, however, often leads to high interference levels in cellular networks operating with universal frequency reuse, such as the 3GPP UTRAN Long Term Evolution (LTE). Coordinated scheduling between different BSs may mitigate this problem by taking...
In this paper, we focus on the guarantee of inter-cell fairness in OFDM femtocell systems. To solve this problem, we formulate an optimization problem to maximize the summation of logarithmic cell capacity. Based on analytic results, we propose an enhanced modified iterative water-filling algorithm which improves inter-cell fairness compared to a modified iterative water-filling algorithm. The key...
We consider joint cross-layer resource allocation and inter-system interference avoidance in OFDMA-based multiuser cognitive radio (CR) systems, where the secondary users (SU) can share spectrum with the primary users (PU) without causing unacceptable interference. The objectives are to provide quality of service (QoS) to both real-time and non-real-time services for SUs, and optimize the system throughput...
In this paper we discuss some of the benefits and challenges of deploying femtocells in a cellular network. In particular, we focus on the tradeoff between energy efficiency and system performance. With realistic LTE system parameters, we have shown that femtocells can indeed improve energy efficiency of the network. However, this comes with a price - performance degradation due to interference, which...
Orthogonal frequency division multiple (OFDM) system with two-level spreading is an effective approach to suppress interference in wireless communication. However, in this system, the orthogonality of its spreading code can be destroyed by multipath fading. In this paper, we propose a novel resource allocation scheme that joints conventional two-level spreading OFDM and smart antenna so as to use...
In this paper, a novel interference coordination scheme based on Dynamic Resource Allocation (DRA) for mitigating inter-cell interference in Long Term Evolution (LTE) cellular systems is presented. In both OFDMA and SC-FDMA systems, inter-cell interference is the most important interference source. Inter-cell interference coordination is considered to improve coverage and increase date rate at cell...
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