Fractional frequency reuse (FFR) is an interference management technique well-suited to OFDMA-based cellular networks wherein the bandwidth of the cells is partitioned into regions with different frequency reuse factors. To date, FFR techniques have been typically been evaluated through system-level simulations using a hexagonal grid for the base station locations. This paper instead focuses on analytically evaluating the two main types of FFR deployments - Strict FFR and Soft Frequency Reuse (SFR) - using a Poisson point process to model the base station locations. The results are compared with the standard grid model and an actual urban deployment. Under reasonable special cases for modern cellular networks, our results reduce to simple closed-form expressions, which provide insight into system design guidelines and the relative merits of Strict FFR, SFR, universal reuse, and fixed frequency reuse. Finally, a SINR-proportional resource allocation strategy is proposed based on the analytical expressions and we observe that FFR provides an increase in the sum-rate as well as the well-known benefit of improved coverage for cell-edge users.

Analytical Evaluation of Fractional Frequency Reuse for OFDMA Cellular Networks

Interference management techniques are critical to the performance of heterogeneous cellular networks, which will have dense and overlapping coverage areas, and experience high levels of interference. Fractional frequency reuse (FFR) is an attractive interference management technique due to its low complexity and overhead, and significant coverage improvement for low-percentile (cell-edge) users. Instead of relying on system simulations based on deterministic access point locations, this paper instead proposes an analytical model for evaluating Strict FFR and Soft Frequency Reuse (SFR) deployments based on the spatial Poisson point process. Our results both capture the non-uniformity of heterogeneous deployments and produce tractable expressions which can be used for system design with Strict FFR and SFR. We observe that the use of Strict FFR bands reserved for the users of each tier with the lowest average \sinr provides the highest gains in terms of coverage and rate, while the use of SFR allows for more efficient use of shared spectrum between the tiers, while still mitigating much of the interference. Additionally, in the context of multi-tier networks with closed access in some tiers, the proposed framework shows the impact of cross-tier interference on closed access FFR, and informs the selection of key FFR parameters in open access.

Analytical Evaluation of Fractional Frequency Reuse for Heterogeneous Cellular Networks

The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality. It is increasingly likely that in the longer term ultrafast optical time-division techniques-together with wavelength multiplexing-will be used in networks at all levels, from the transcontinental backbone to the desktop. Examples of devices include a subpicosecond clock source packaged inside a laptop personal computer and an OTDM switch on a single semiconductor chip, both produced at HHI. Advances similar to these make it possible now to envisage the use of OTDM techniques, not just in the highest layers of national and international networks, but also much closer to the user-such as the world-first demonstrations at BT Laboratories of a 40 Gb/s TDMA LAN and a 100 Gb/s packet self-routing switch for multiprocessor interconnection. Ultrafast networks might even provide the interconnection backplane inside future desktop routers and servers with massive throughput.

Ultra-high-bit-rate networking : From the transcontinental backbone to the desktop : Optical networks technology in Europe

A comprehensive review on coordinated multi-point operation for LTE-A

Mobility load balancing MLB redistributes the traffic load across the networks to improve the spectrum utilisation. This paper proposes a self-organising cluster-based cooperative load balancing scheme to overcome the problems faced by MLB. The proposed scheme is composed of a cell clustering stage and a cooperative traffic shifting stage. In the cell clustering stage, a user-vote model is proposed to address the virtual partner problem. In the cooperative traffic shifting stage, both inter-cluster and intra-cluster cooperations are developed. A relative load response model is designed as the inter-cluster cooperation mechanism to mitigate the aggravating load problem. Within each cluster, a traffic offloading optimisation algorithm is designed to reduce the hot-spot cell's load and also to minimise its partners' average call blocking probability. Simulation results show that the user-vote-assisted clustering algorithm can select two suitable partners to effectively reduce call blocking probability and decrease the number of handover offset adjustments. The relative load response model can address public partner being heavily loaded through cooperation between clusters. The effectiveness of the traffic offloading optimisation algorithm is both mathematically proven and validated by simulation. Results show that the performance of the proposed cluster-based cooperative load balancing scheme outperforms the conventional MLB. Copyright © 2013 John Wiley & Sons, Ltd.

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Self-organising cluster-based cooperative load balancing in OFDMA cellular networks

This work addresses the problem of inter-cell interference (ICI) management in the context of single frequency broadband OFDMA-based networks. Five proposals, based on a combination of ICI coordination/avoidance techniques along with a set of heuristic adaptive power and subcarrier allocation algorithms, have been considered in order to achieve better interference performance and resource utilization in a multi-cellular environment. Connected with a proper power mask based design, the potential gain of a flexible frequency sectorization solution, halfway between fractional/soft frequency reuse and pure frequency sectorization, is explored.

Interference Management through Resource Allocation in Multi-Cell OFDMA Networks

In this paper, we analyze the problem of strong intercell interference (ICI) fluctuations in OFDMA networks with frequency reuse of one and their effects on system performance Our goal is to outperform fractional frequency reuse scheme by proposing a joint time and frequency resource scheduling algorithm that limits ICI fluctuations both in full and partially loaded scenarios Adaptive MCS selection according to channel conditions in addition to traffic requirements is considered Simulation results show that our proposed scheme enhances the system performance and the user satisfaction

Downlink scheduling for intercell interference fluctuation mitigation in partial-loaded broadband cellular OFDMA systems

This paper focuses on the inter-cell interference (ICI) management problem in the downlink channel for mobile broadband wireless OFDMA-based systems. This subject is addressed from the standpoint of different interrelated resource allocation mechanisms operating in multi-cell scenarios in order to exploit frequency and multi-user diversity: ICI coordination-avoidance and adaptive subcarrier and power allocation. Even though these methods can be applied in a stand-alone way, a significant performance improvement is achieved if they are jointly designed and operate in a combined basis. Several alternatives for mixed frequency and power ICI coordination schemes are proposed in this paper. Connected with a proper power mask-based design, the potential gain of a flexible frequency sectorization solution, halfway between fractional-soft frequency reuse and pure frequency sectorization, is explored. The main objective is to outperform fractional-soft frequency reuse offering an attractive trade-off between cell-edge user data rates and average cell throughput. Proposals concerning ICI coordination-avoidance have been evaluated in combination with several heuristic adaptive subcarrier and power allocation algorithms. Copyright © 2009 John Wiley & Sons, Ltd.

This paper focuses on the inter-cell interference (ICI) management problem in the downlink channel for mobile broadband wireless OFDMA-based systems. This subject is addressed from the standpoint of different interrelated resource allocation mechanisms operating in multi-cell scenarios in order to exploit frequency and multi-user diversity. Several alternatives for mixed frequency and power ICI coordination schemes, fully integrated with several heuristic adaptive subcarrier and power allocation algorithms, have been proposed, and evaluated.

Radio resource allocation for interference management in mobile broadband OFDMA based networks

In this paper we propose three different frequency resource management strategies that, working together with FFR and open-loop Fractional Power Control (PFC), succeed on mitigating both uplink inter-cell interference (ICI) and ICI fluctuations, that usually reduce the performance of SC-FDMA cell-based systems. Simulations are carried out with real-time traffic patterns at different loading scenarios, showing that our strategies outperform a typical FFR scheme suggested to coordinate frequency assignments among neighboring cells.

Radio resource strategies for uplink inter-cell interference fluctuation reduction in SC-FDMA cellular systems

In this paper, a comparative analysis of the performance of the nonsynchronized initial random access channel in Mobile WiMAX and E-UTRA systems under different conditions (fast fading, multiuser interference) is carried out. The analysis is focused on the correlation properties of the code sequences used in each case. We evaluate their ability to provide low values for false alarm and erroneous detection probabilities (detecting a sequence that has not been transmitted) at the same time as guaranteeing low nondetection probabilities of the effectively transmitted sequences. Results show the promising performance of the E-UTRA scheme, even in high mobility scenarios, where the Doppler effect requires additional considerations to guarantee the correct system operation.

Israel Guio

Papers

Interference Management through Resource Allocation in Multi-Cell OFDMA Networks

Downlink scheduling for intercell interference fluctuation mitigation in partial-loaded broadband cellular OFDMA systems

Radio resource allocation for interference management in mobile broadband OFDMA based networks

Radio resource strategies for uplink inter-cell interference fluctuation reduction in SC-FDMA cellular systems

Performance evaluation of nonsynchronized initial random access for mobile broadband systems