Juejia Zhou

Hybrid Spectrum Usage for Overlaying LTE Macrocell and Femtocell

This paper investigates flexible spectrum usages for LTE network that consists of overlaying macrocell and femtocell. In such a networking environment, shared spectrum usage and partitioned spectrum usage are two options to be employed between two radio tiers. After recognizing the pros and cons of these two usages, we propose hybrid spectrum usage to take advantage of their merits. In our proposal, the femtocells embedded in macrocell are differentiated to inner and outer femtocells, which operate in partitioned spectrum usage and shared spectrum usage, respectively. Analysis and performance evaluation are given to illustrate and justify our proposed method on improving spectrum utilization for wireless overlay network.

Energy Source Aware Target Cell Selection and Coverage Optimization for Power Saving in Cellular Networks

The spread of mobile connectivity is generating major social and economic benefits around the world, while along with the rapid growth of new telecommunication technologies like mobile broadband communication and M2M (Machine-to-Machine) networks, larger number of various base stations will be employed into the network, which will greatly increase the power expense and CO2 emission. In order to degrade the system power expense, variety of researches on new energy and novel transmission technology are put in agenda. In this paper, instead of reducing the absolute power expense, the research focuses on guiding more power consumption into green source energy, which implying that the UEs (User Equipment), especially the cell edge UEs, will have preferential access to the BSs (Base Station) with natural energy supply. To realize the tendentious connection, two detailed approaches are proposed, the HO (Hand Over) parameter tuning for target cell selection and power control for coverage optimization. The system evaluation shows that, by proper setting of parameters in HO and power control, both of the two approaches can achieve good balance between energy saving effect and system throughput impact.

Component Carrier Management for Carrier Aggregation in LTE-Advanced System

This paper focuses on investigating appropriate management of Component Carriers(CCs) in carrier aggregation( CA) system, which is identified as one of the most distinct features of 4G systems including Long Term Evolution- Advanced (LTE-A). An LTE-A user equipment (UE) is allowed to concurrently utilize multiple carriers, which leads to scalable increase in user throughput. However, in certain circumstances, aggregating entire available carriers for a UE is not meaningful due to probably low channel quality or high traffic load in some of the CCs. Therefore, how to make good use of multiple carriers in real deployment scenarios is an important issue. Based on the analysis of resource allocation across multiple carriers in Layer-2, two CC management methods in Layer- 3 are proposed. The proposed method is shown by simulation results to be effective in providing comparable user throughput with lower implementation complexity, as compared to solely ingenious resource allocation.

Resource coordination and interference mitigation between macrocell and femtocell

This paper investigates spectrum resource coordination for the mixed macrocell and femtocell deployment. Though sharing spectrum provides larger bandwidth for both macrocell and femtocell, cross-tier interferences exist and become drawbacks for them to achieve higher capacities. After analyzing the interferences when using shared spectrum, we propose to employ hybrid spectrum sharing with respect to different femtocells such that the merit of sharing spectrum can be kept and the major interferences can be reduced. Then, we present a method to mitigate the remaining interference when employing hybrid spectrum sharing. Performance evaluation is given to justify our proposed approach on improving overall spectrum utilization.

Hybrid spectrum sharing for coexistence of macrocell and femtocell

This paper investigates flexible spectrum sharing for coexistence of macrocell and femtocell. In such a networking environment, shared spectrum usage and partitioned spectrum usage are two options to be employed between them. After recognizing the pros and cons of these two usages, we propose hybrid spectrum sharing to take advantage of their merits. In our proposal, the femtocells embedded in macrocell are differentiated to inner and outer femtocells, which operate in partitioned spectrum usage and shared spectrum usage, respectively. Performance evaluation are given to justify our proposed method on improving overall spectrum utilization.

Source and Channel Coding Adaptation for Optimizing VoIP Quality of Experience in Cellular Systems

Quality of Experience (QoE) reflects the customers perception of service, and is extremely important for operators. In VoIP service, variety of factors will affect customers QoE, e.g. source data quality and the transmission channel condition. In cellular systems, although higher level of source coding will improve QoE, more radio resource will be consumed and thus degradation of system capacity will be caused. On the other hand, lower level of modulation and coding can ensure the data delivery, but will lead to more consumption of radio resource. In this paper, to solve these problems in multi-user cellular systems, the source coding quality and channel coding levels are jointly considered according to customers QoE. In the source and channel coding adaptation, customers with over qualified QoE will sacrifice some radio resource to improve the under guaranteed QoE of others, or increase the system capacity. The simulation shows that the algorithm can effectively balance the utility of limited radio resource and increase customers satisfaction ratio and system capacity.

Multi-tier token based scheduling considering QoS and revenue in OFDMA system

Due to the propagation of smart handhold terminals, e.g. iPhone and iPad, the data traffic is growing rapidly in cellular networks. To fulfill the increased data traffic and attract more customers, the operators need to construct the network infrastructure and update their service planning, e.g. via introduction of flat-rate (FR) service plan. While along with the increase of data users, especially FR users, the operators find that the revenue and QoS (Quality of Service) will not improve accordingly. One important reason is that the over-transmitted FR services will distinctly affect the QoS of non-flat-rate (NFR) ones, and meanwhile lead very limited revenue benefit to operators. The conventional QoS scheduling researches are mainly targeting to UE (User Equipment) side issues, e.g. GBR (Guaranteed Bit Rate), instead of the revenue from operator side. To consider both UEs QoS and operational revenue, the paper firstly introduces the Token based Proportional Fairness (TPF) scheduling as the premise, and then presents the Multi-tier Token Model (MTM) for FR and NFR differentiation. After that, the two-stage PF factor updating method for revenue optimization is proposed. The system evaluations show that the proposed solution of revenue oriented scheduling can properly distribute the radio resource for higher income tendentiousness, and in the meantime fulfill the GBR requests for both FR and NFR services.