Fractional Frequency Reuse (FFR), which was introduced by 3GPP is considered the powerful technique to improve user performance. However, implementation of FFR is a challenge due to strong dependence between base stations (BSs) in terms of resource allocations. This paper studies a modified and flexible FFR scheme that allows all BSs works independently. The analytical and simulation results prove that the modified FFR scheme outperforms the conventional FFR.

For a multiuser multi-input multi-output (MU-MIMO) multicell network, the Han-Kobayashi strategy aims to improve the achievable rate region by splitting the data information intended to a serviced user (UE) into a common message and a private message. The common message is decodable by this UE and another UE from an adjacent cell so that the corresponding intercell interference is cancelled off. This work aims to design optimal precoders for both common and private messages to maximize the network sum-rate, which is a highly nonlinear and nonsmooth function in the precoder matrix variables. Existing approaches are unable to address this difficult problem. In this paper, we develop a successive convex quadratic programming algorithm that generates a sequence of improved points. We prove that the proposed algorithm converges to at least a local optimum of the considered problem. Numerical results confirm the advantages of our proposed algorithm over conventional coordinated precoding approaches where the intercell interference is treated as noise.

With the big success of 802.11 wireless networks, there have been many proposals addressing end-to-end QoS guarantees in 802.11 WLAN. However, we have found that current end-to-end QoS architectures lack of one or more important properties such as cross-layer interaction, end-to-end integration, reconfigurability and modularity. In this work, we present an end-to-end reference QoS architecture for 802.11 WLAN that encapsulates in an unifying fashion software-based QoS components (mechanisms, algorithms, services), proposed in the literature. To show the usefulness and correctness of the reference architecture, we present three case studies of end-to-end QoS architectures addressing different QoS requirements such as bandwidth and delay with different approaches such as differentiated services and integrated services. We will give an architectural comparison and performance evaluation of these architectures. We believe the reference QoS architectures can help QoS designers to understand the importance and the complexity of various QoS components during the design phase and thus choose these QoS components appropriately.