Multi-Cell Cooperation with Fairness Constraint in the Downlink OFDMA Cellular Networks

Abstract

SUMMARY In this letter, we study cell cooperation in the downlinkOFDMA cellular networks. The proposed cooperation scheme is based onfractional frequency reuse (FFR), where a cooperation group consists ofthree sector antennas from three adjacent cells and the subchannels of eachcooperation group are allocated coordinately to users. Simulation resultsdemonstrate the effectiveness of the proposed schemes in terms of through-put and fairness. key words: multi-cell cooperation, OFDMA, FFR, ICI coordination, fair-ness 1. Introduction As an advanced physical layer technology, OFDMA hasbeen proposed by 3GPP LTE (3rd Generation PartnershipProject Long Term Evolution) to be the multiple accesstech-nique for the downlink in B3G (Beyond 3rd Generation)systems [1]. In the OFDMA-based cellular system, the sub-channels used within a cell are orthogonal to each other suchthat the interference can be avoided. However, the users onthe border of the cell not only receive signals from the serv-ing base station (BS), but also suffer severe inter cell inter-ference (ICI) from the neighboring cells which use the sameset of subchannels. The so called ICI will degenerate thesystem performance and must be mitigated.In 3GPP LTE, three approaches have been proposed tomitigate the so-called ICI, i.e., ICI randomization, ICI coor-dination, and ICI cancelation. Among the three approaches,ICI coordination is comparatively easier to be realized andcan be used in various wide band traffics [2]. The basicidea behind ICI coordination is exploiting FFR techniqueto separate the interfering source as far as possible whileincreasing spectral efficiency as much as possible [3],[4].FFR relies on partitioning the total available frequency re-source into two sets and dividing a cell into two concentricregion, namely, interior region and exterior region. One setof the frequency is used by users in the interior region of allcells with a frequency reuse factor (FRF) of 1. While the