No abstract

enhancements are similar in concept to those incorporated in third generation cellular standards such as CDMA2000* high rate packet data (HRPD) [4] or the high speed downlink packet access (HSDPA) feature within the Universal Mobile Telecommunications System (UMTS) standard [1], they have been specifically tailored to an OFDMA air interface. Additional subchannelization options have been added in IEEE 802.16e to improve resource management flexibility and achieve better system performance under a wide range of operating conditions. IEEE 802.16e also adds new medium access control (MAC) procedures related to handover support. Multiple carrier bandwidths and associated fast

No abstract

No abstract

No abstract

No abstract

No abstract

The capacity of a wireless network could be considerably improved by employing directional antennas which are capable of illuminating multiple beams toward different directions. However, more beams from the same BS may lead to stronger inter-cell interference. In this paper, we consider coordinated beam scheduling schemes to mitigate the inter-cell interference. We first formulate this problem as a combinatorial optimization problem. We then reveal that the complexity of this problem hinges upon a single scalar termed as degree of constraint (DoC), which is related to the degree of conflict a beam is subject to. If the DoC is at least 3, the general beam scheduling problem is NP-hard. If DoC is smaller than 3, which corresponds to a relevant subclass of the beam scheduling problem arising in practice, this problem can be solved in polynomial time. We propose an optimal beam switching algorithm based on the auction method to this particular subclass of problem. This algorithm is of low complexity and is well suited for distributed implementation. We then extend the auction algorithm to solve the general multi-cell beam scheduling problem. The performance of the proposed algorithms is finally assessed through extensive simulation studies.