Interference Management for OFDMA Femtocell Networks

Overview

Wireless data traffic has been increasing exponentially with the growing demand of mobile internet. Reducing cell sizes is an effective way to increase system capacity, since signal to interference plus noise ratio (SINR) increases significantly as the distance between a transmitter and a receiver decreases. However, the costs of increased number of base station and required backhaul connectivity are expensive, and site acquisition for installing macro base stations is difficult and very costly. Instead, low-tier femto base stations, which are customer owned, short-range, low-cost, and low-power in-building base stations, are very helpful for improving cell capacity and coverage. This femto-cell concept is promising since 50% of all voice calls and more than 70% of data traffic originates indoors and it can substantially decrease the power consumption of mobile devices. Femto base stations can also be used in outdoor situations such as hotspots or cell edges, to increase the capacity of the region and to extend wireless coverage, respectively. However, femto-cells are not preplanned and use the same resources as the macro base stations, thus introducing cross-tier interference as well as inter-femto-cell interference. If this interference is not handled appropriately, the performance of cellular networks comprising both macro-cells and femto-cells could be worse than that of only macro-cell networks.

The goal of this research is to study ways of managing interference in multi-cell OFDMA cellular networks combining macro base stations and femto base stations to maximize the system throughput and to guarantee quality of service (QoS) for various applications. In this study, we seek appropriate frequency, time, and power allocation algorithms for OFDMA combined macro/femto-cell networks to achieve substantial gains in the system capacity per unit area as well as cell-edge user throughput, by mainly managing inter-macro, inter-femto, and cross-tier interference.

Papers

  • Min-Sung Kim, Hui Won Je, and Fouad A. Tobagi, “Distributed Power Allocation for OFDMA Femtocell Networks”, in preparation
  • Min-Sung Kim, Hui Won Je, and Fouad A. Tobagi, “Cross-tier Interference Mitigation for Two-tier OFDMA Femtocell Networks with Limited Macrocell Information”, submitted to IEEE Globecom 2010
  • Min-Sung Kim, Moo Ryong Jeong, Fujio Watanabe, and Fouad Tobagi, “Band-distributed Channel-aware Fractional Frequency Reuse in OFDMA Systems”, IEEE Vehicular Technology Conference (VTC) Fall 2009, September, 2009

Slide

People

Fouad A. Tobagi
Professor of Electrical Engineering
tobagi AT stanford DOT edu
Min-Sung Kim
Ph.D. candidate of Electrical Engineering
minsung AT stanford DOT edu