Zezhou Luo

Dynamic Frequency Self-Optimization for Dense WLANs

Frequency optimization has a great impact on lots of network Key Performance Indicators (KPIs). Conventional approaches focus on direct mitigating contention or interference among Access Points (APs), ignoring the network KPIs and their conflicts. In this paper, we propose a novel Frequency Self-Optimization (FSO) scheme to improve network KPIs in dense Wireless Local Area Networks (WLANs) where network environment is highly dynamic. By modeling the network load and related KPIs, we can derive an optimal frequency assignment solution for all APs. We formulate this problem as a multi-objective optimization problem and propose an Evolutionary Particle Swarm Optimization (EPSO) algorithm to reduce the user dissatisfaction degree and service interruption ratio, and improve the network throughput as well. Simulation results show that the proposed scheme greatly improves network KPIs and outperforms the traditional ones e.g. Dynamic access point Load-based Plan (DYLD) scheme.

A Novel Signal Detection Method for Spectrum Sensing Using Directionality

Technologies such as cognitive radio, interference coordination and spectrum sharing are promising to provide higher spectrum efficiency and throughput, and spectrum sensing is usually the first step. Generally, an intentionally emitted signal shows directionality at receiver in many cases. Intuitively, if we find the feature that characterizes the directionality of received signal, we can use this feature to identify the presence of a signal. In this paper, we propose a new detection method by exploiting directionality of a signal with only one snapshot, and the performances of the directionality detection in various conditions are also examined. Simulation shows that the proposed directionality detection achieves better performance than conventional energy detection by carefully designing the beams of receiver antenna system in some scenarios.

Flexible Carrier Utilization in Dense Stadium

This paper investigates dynamic spectrum resource utilization in dense stadium. The proposed scheme flexibly aggregates intra-site and inter-site resources for UEs taking into account various factors such as traffic demand, network load condition, channel quality. Extensive simulation results are presented to validate its performance. The results may shed some light on the design and deployment of future dense stadium networks.

Network-Wide Optimization of Uplink Fractional Power Control in LTE Networks

Next generation cellular networks will provide users better experiences by densely deploying smaller cells, which results in more complicated interferences environment. In order to coordinate interference, power control for uplink is particularly challenging due to random locations of uplink transmitter and dense deployment. In this paper, we address the uplink fractional power control (FPC) optimization problem from network optimization perspective. The relations between FPC parameters and network KPIs (Key Performance Indicators) are investigated. Rather than considering any single KPI in conventional approaches, multi-KPI optimization problem is formulated and solved. By relaxing the discrete optimization problem to a continuous one, the gradients of multiple KPIs with respect to FPC parameters are derived. The gradient enables efficiently searching for optimized FPC parameters which is particularly desirable for dense deployment of large number of cells. Simulation results show that the proposed scheme greatly outperforms the traditional one, in terms of network mean load, call drop & block ratio, and convergence speed.

A novel successive relaying protocol based on superposition coding

Successive relaying is a prominent way to efficiently reduce the multiplexing loss in cooperation system. In this paper, we design a successive relaying protocol based on superposition coding. After solving the co-channel interference at the relays, they have capacity of forwarding the superposition code of the relaying signal and the source signal. An analysis model is established in terms of system achievable rate. The BER performance of our approach is also compared with that of some cooperation protocols. It is shown that the proposed protocol can reduce the system BER and offer some diversity gain, while achieves almost the same multiplexing performance compared with direct communication.

Subcarrier Coupling and Scheduling for Multi-User OFDMA Relaying Networks

The performance of subcarrier coupling and its effects on different scheduling schemes in multi-user OFDMA relaying networks are investigated in this paper. The relay station adopts the amplify-and-forward (AF) relaying strategy and is allowed to couple an input subcarrier to another output subcarrier. We show that in a source-relay-destination model, subcarrier coupling can achieve substantial capacity gain only when the two hop links have similar channel qualities, and the achievable gain also depends on the slow-fading magnitude of either hop. In view of this, we employ a sub-optimal subcarrier coupling scheme with low complexity for the multi-user scenario. Simulation results demonstrate that the sub-optimal scheme achieve similar performance compared to the conventionally optimal scheme.