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Multi-Cell Slots Allocation in OFDMA Systems

OFDMA (Orthogonal Frequency Division Multiple Access) is considered to be the leading technology for the upcoming 4G cellular infrastructure. OFDMA is a multi-user version of the popular OFDM (Orthogonal Frequency Division Multiplexing) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers (subchannels or slots) to individual users. This allows for multiple simultaneous low data rate transmissions to several users. In this paper we describe several optimization problems related to the allocation of radio resources in OFDMA systems. The basic problem we define is a slots assignment task in a multi-cell OFDMA environment. The goal is to assign subchannels to mobile stations such that the demands of all of mobile stations will be satisfied with minimum interferences. We then describe two further optimization problems that generalize the slots assignment problem. A close to optimal solution to these problems will allow providers to better utilize their radio resources and to provide services in a cost efficient way.