Wei Zheng

A Novel Handover Mechanism Between Femtocell and Macrocell for LTE Based Networks

The femtocell networks that use Home eNodeB and existing networks as backhaul connectivity can fulfill the upcoming demand of high data rate for wireless communication system as well as can extend the coverage area. It is also of interest to minimize operational effort by introducing self-optimizing mechanisms, and the optimization of the Home eNodeB involved handover is an important goal of LTE-Advanced. Since the different network architecture and functionality between Home eNodeB and LTE eNodeB, the handover procedure between the femtocell and macrocell should be modified in LTE network. In this paper, modified signaling procedure of handover is presented in the Home eNodeB gateway based femtocell network architecture. A new handover algorithm based on the UE’s speed and QoS is proposed. The comparison between the proposed algorithm and the traditional handover algorithm shows that the algorithms proposed in this paper have a better performance in the reducing of unnecessary handovers and the number of handovers.

Signalling Cost Evaluation of Handover Management Schemes in LTE-Advanced Femtocell

Femtocell is a small access point using the wire broadband connections or wireless technologies to access the mobile operators network for the user equipment(UE), which can provide better indoor coverage and satisfy the upcoming demand of high data rate for wireless communication system.Femtocell related handover cost reduction is one of the important targets in LTE-Advanced SON (Self-Organising Networks). In this paper, a handover optimization algorithm based on the UEs mobility state is proposed. An analytical model was presented for the handover signalling cost analysis. Numerical results are provided to compare the signalling cost of different handover management schemes. The comparison between the proposed algorithm and the traditional handover control algorithm shows that the algorithms proposed in this paper have a significant reduction in the signalling overhead.

A History-Based Handover Prediction for LTE Systems

Handover prediction has been considered an effective technology for improvement of LTE Handover performance. Although not a few techniques have been proposed to achieve this goal including handover preparation based on cross-layer optimization and mobility prediction, the fact is that their gains are not usually so high as their cost. To overcome such weaknesses, this paper proposes a simple handover prediction technique which is based on a novel user mobility model to approximate simulation the laws of user mobility actions. We develop a user mobility database to assist the mobility prediction based on the user mobility history records. The simulation results show that the proposed technique minimizes the number of handovers and lower the ping-pang rate in LTE system.

Filtering Short Message Spam of Group Sending Using CAPTCHA

Short message spam brings so much trouble to the users, and the volume of short message spam becomes more and more large, especially the function of group sending is used in short message. This paper proposes a method to filter short message spam of group sending, in other words, it utilizes CAPTCHA (completely automated public Turing test to tell computers and human apart) method to filter short message spam. If the short message service (SMS) can pass the CAPTCHA, it will be identified as legitimate SMS and transmitted by Short Message processing Center. Conversely, if the SMS can not pass the CAPTCHA, it will be identified as SMS spam and deleted by Short Message processing Center. Finally, it has been simulated with Smartphone of Microsoft Visual Studio 2005.

A Novel Self-Optimizing Handover Mechanism for Multi-service Provisioning in LTE-Advanced

The 3GPP is defining the next generation radio access network which introduces advanced self- optimization to reduce the operational efforts and complexity. It is also of interest to minimize operational effort by introducing self-optimizing mechanisms. Optimization of the handover parameters is an important goal of LTE-Advanced. In this paper, a new self- optimizing handover algorithm based on the estimation of the number of cell-boundary crossings is proposed. The algorithm adjusts the handover parameters, such as Time- to-Trigger, measurement interval, and hysteresis, by comparing the number of cell-boundary crossings and the number of handovers UE performed in a period. To optimize the handover performance further, an adaptive L3 filter based on the UE’s velocity is proposed in this paper. A typical application scenario of this algorithm is high/medium speed environment under multi-service provisioning. The simulation results shows that the algorithms proposed in this paper have a better performance in the rate of ping-pong handovers and the average number of handovers.

Shot Boundary Detection and Keyframe Extraction Based on Scale Invariant Feature Transform

In shot boundary detection, the key technology is to compute the visual content discontinuity values between consecutive video frames. In this paper, a unified framework is proposed to detect the shot boundaries and extract the keyframes of a shot. Firstly, the Scale invariant feature transform (SIFT) is adopted to compute the visual content discontinuity values. Then a new method, which is called the Local Double Threshold Shot Boundary Detection (LDT-SBD), is used to detect shot boundaries. Lastly, two mechanisms are proposed to extract keyframe. Experimental results show the framework is effective and has a good performance.

Signalling Overhead Evaluation of HeNB Mobility Enhanced Schemes in 3GPP LTE-Advanced

Home eNodeB (HeNB) is a low-power access point using the local broadband connections or a separate RF backhaul to access the mobile operators network for the user equipment(UE), which can provide better indoor coverage and satisfy the upcoming demand of high data rate for users. Considering the potential frequent mobility between HeNB-HeNB and HeNBeNB, HeNB mobility enhancement is proposed as one of the most important work items in 3GPP LTE-Advanced. In this paper, four X2 interface based HeNB mobility enhanced architectures are explicitly discussed in terms of signalling overhead evaluation. The numerical results show that the direct-X2 based option 2 in HeNB-HeNB scenario and the X2-GW based option 3 in eNB-HeNB scenario have the best trade-off in signalling overhead and complexity respectively.

A Simple Method for Filtering Image Spam

Image spam can easily circumvent widely text spam filters. It is a new trend of spam, and poses a great threat to email communications. In this paper, we give the definition of image spam firstly. Then we propose a simple method for filtering image spam, which utilizes file properties and histogram (gray histogram or color histogram). Finally, a preliminary experimental evaluation of our approach is reported on a personal dataset and Princeton benchmark dataset of spam images publicly available.

A Self-Optimizing Mobility Management Scheme Based on Cell ID Information in High Velocity Environment

Reduction of the operational effort and cost is a key driver for RAN LTE (Long Term Evolution or E-UTRAN). Self-configuring and self-optimizing mechanisms are introduced as a part of Self Organizing Network (SON) to maximize the integrated performance of LTE/LTE-Advanced by improving the efficient of operation and maintenance. Optimization of handover is one of the optimization aspects of Self Organizing Network in LTE-Advanced. High velocity environment, especially multi-service environment usually needs extensively investigation to optimize. Using layer3 filter, hysteresis, and time-to-trigger mechanisms is standardized for LTE Hard handover. In this paper, an interacting self-optimizing handover mechanism based on cell ID information is proposed. We have shown that significant gain can be achieved by the use of optimization mechanism while maintaining low handover rates and ping-pong handover rate.

Distributed uplink power control for two-tier femtocell networks via convex pricing

Interference management is one of the most important issues in two-tier femtocell networks in which a central macrocell underlaid with several femtocell hotspots. To address the cross-tier and co-tier interference, this paper introduces an energy-efficient power control algorithm via convex pricing scheme, where both circuit and transmit power have been considered. To achieve the target SINR, the macrocell protects itself by actively adapting its interference cap on the total interference they are willing to tolerate and pricing the interference from the femtocell user equipments (FUEs), while the FUE is to maximize its own throughput and keep the fairness with the other FUEs. Then, the existence and uniqueness of the equilibrium for the proposed scheme are studied. Simulation results show that the proposed scheme can improve energy efficiency of femtocell networks and mitigate the crossand co-tier interference significantly while guaranteeing the minimum QoS requirement of macrocell users.