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This article proposes a new enhanced fractional frequency reuse (FFR) scheme to improve the system performance in multi-cell orthogonal frequency division multiple access system, which tackles the problems of frequency distribution and inter-cell interference (ICI) by jointly FFR and ICI coordination. The proposed scheme dynamically assigns subcarriers to center and edge groups depending on load conditions and the channel state information by two algorithms. The center allocation algorithm assigns subcarriers to center users from different directions. The edge allocation algorithm allows the highly loaded sectors to borrow the remaining subcarriers from center band or other sectors considering the fairness requirements of all the users. Simulation results illustrate that the proposed scheme can outperform the traditional schemes by achieving higher throughputs and better spectral efficiency especially in highly loaded cells.

This article proposes an integrated framework for adaptive QoS provision in IEEE 802.16e broadband wireless access networks based on cross-layer design. On one hand, an efficient admission control (AC) algorithm is proposed along with a semi-reservation scheme to guarantee the connection-level QoS. First, to guarantee the service continuity for handoff connections and resource efficiency, our semi-reservation scheme considers both users' handoff probability and average resource consumption together, which effectively avoids resource over-reservation and insufficient reservation. For AC, a new/handoff connection is accepted only when the target cell has enough resource to afford both instantaneous and average resource consumption to meet the average source rate request. On the other hand, a joint resource allocation and packet scheduling scheme is designed to provide packet-level QoS guarantee in term of "QoS rate", which can ensure fairness for the services with identical priority level in case of bandwidth shortage. Particularly, an enhanced bandwidth request scheme is designed to reduce unnecessary BR delay and redundant signaling overhead caused by the existing one in IEEE 802.16e, which further improves the packet-level QoS performance and resource efficiency for uplink transmission. Simulation results show that the proposed approach not only balances the tradeoff among connection blocking rate, connection dropping rate, and connection failure rate, but also achieves low mean packet dropping rate (PDR), small deviation of PDR, and low QoS outage rate. Moreover, high resource efficiency is ensured.