Kang Yong Lee

Transmit Beamforming Based Inter-Cell Interference Alignment and User Selection with CoMP

Recently, two types of coordinated multiple point transmission (CoMP) technologies - joint processing and transmission (JPT) and coordinated scheduling and beamforming(CSB) - have been proposed to the latest cellular communication standard named as a Network MIMO, to improve the performance of cell-edge users who suffer strong ICI. In this paper, we investigate an ICI cancelation employing a user selection algorithm associated with CoMP-CSB, which is more practically used for cellular networks. Under the partial channel state information (CSI) and no data sharing condition, each base station (BS)concentrates more on the direction of the interference to users located at the adjacent cells during the user selection process.

Downlink Transmit Beamforming for Inter-Cell Interference Mitigation with BS Cooperation

The capacity of downlink multiple-input multiple-output (MIMO) cellular network is significantly limited by inter-cell interference (ICI), especially at the cell boundary. In this paper, we propose an ICI cancelation employing a user selection algorithm associated with CoMP-CSB, which is more practically used for cellular networks. Under the partial channel state information (CSI) and no data sharing condition, each base station (BS) concentrates more on the direction of the interference to users located at the adjacent cells during the user selection process. Although it is obvious that there are trade-offs between the ICI mitigation and the number of simultaneous scheduled users in terms of system capacity, the simulation results show that our proposed algorithm achieves higher sector throughput and is more robust against the ICI when the system is limited by interference.

Social TV service: A case study

This paper presents a new television (TV) service model, social TV service, which integrates social networking context and Internet protocol television (IPTV) to create a new type of sharable, interactive and participative TV service. With the social TV service, people can share their opinions and feelings with friends and experiences enriched TV services, such as personalized recommendation and target advertisement. In this paper, based on our implementation, we first investigate in detail the key features that differentiate social TV service from traditional IPTV service. In addition, a use case of potential social TV service, called Virtual SocieTV (VSTV), we implemented as a demo application, is introduced.

Efficient Traffic Prediction Algorithm of Mutimedia Traffic for Scheduling the Wireless Network Resources

Real-time variable bit rate (VBR) video traffic generated from multimedia applications, such as MPEG-coded video, is expected to be large portions of the traffic in future wired/wireless networks. The nature of VBR traffic and its quality of service (QoS) constraints increase a number of challenges on network resource managements and operational utilizations. Thus, accurate traffic prediction based dynamic resource allocation and scheduling can significantly improve network performance substantially while satisfying QoS requirements. In this paper, we propose a novel prediction algorithm of MPEG-coded real-time VBR video traffic for IEEE 802.11e wireless LANs (WLANs). Based on statistical property of traffic stream, our algorithm performs a prediction of the next frame size for i-, p-, and b-frames. Simulation study using real- world MPEG-4 coded video traces shows that the proposed algorithm achieves much better performance than ANFIS LMS, and NN methods. In addition, the applicability of our prediction algorithm to IEEE 802.11e WLAN is discussed.

Cross-layered Hop-by-Hop Congestion Control for Multihop Wireless Networks

In this paper, we present a novel congestion control algorithm (HRC), which uses hop-by-hop approach and rate-based transmission, for IEEE 802.11 multihop wireless networks. Since medium contention is most dominant cause of packet loss in multihop wireless networks, our algorithm considers the degree of medium contention level experienced at a given node for data rate control at the transport layer. The main purpose of our algorithm is to maximize the network throughput by data rate control while minimizing the packet losses caused by medium contention. The simulation study using GloMoSim shows that our algorithm achieves up to 40% more the network throughput than TCP and TCP-selective acknowledgment (SACK)

Efficient QoS Scheduling Algorithm for Multimedia Services in IEEE 802.11e WLAN

As IEEE 802.11 wireless local area network (WLAN) devices currently have gained wide popularity, demands on quality of service (QoS) capability have increased as well. Although IEEE 802.11e is proposed for the support of QoS by traffic and service differentiation, it still has weakness on the adapting the multimedia services which has the traffic characteristic of variable bit rate (VBR). In this paper, we first discuss problems of the current standard and analyze how to improve the QoS capability in IEEE 802.11e. In addition, we propose a new scheduling algorithm, referred to as ETA-EQN, which aims at supporting multimedia service in HCCA of IEEE 802.11e WLAN. Results from intensive simulations with NS-2 verify that ETA-EQN provides much better network performance in terms of throughput, delay, and packet loss.

CAT: Contention Aware Transport Protocol for IEEE 802.11 MANETs

In this paper, we present a contention aware transport (CAT) protocol which is hop-by-hop, rate-based control, over IEEE 802.11 MANETs. CAT introduces a novel control metric, sending rate control factor (SRCF), for the congestion control. The SRCF considers the contention density which represents the degree of contention level experienced at a given node. In addition, to support reliable delivery, CAT uses a hop-by-hop acknowledgement scheme. The main purpose of CAT is, to find optimal traffic load that the channel bandwidth is fully utilized by sending rate adjustment while minimizing the packet losses from medium contention. The simulation results show that the network throughput achieved by CAT is around 10% and about 30% at peak point, higher than that of TCP and TCP-SACK

New Load Balancing Method for VoD Service

As IPTV services advance, an increasing user demand and tremendous content volume of multimedia content cause some difficulties in network resource management. In this paper, we propose an improved load balancing algorithm for VoD service. Unlike existing algorithms, the proposed algorithm considers users’ behaviors for VoD service, and determines the most efficient allocation of VoD requests by estimating expected server load and expected user waiting time. In order to evaluate our algorithm, we conduct a simulation of an IPTV network and verify the effectiveness of our system by comparing it with two baselines (Least Load and Nearest methods). As experimental results, the proposed system performs significantly better than the baselines. Consequently, the system can manage limited network resources efficiently and enhance QoE.

D-PuP: An enhanced prediction algorithm for real-time MPEG-4 VBR video traffic with dynamic adaptation

In previous work [1], we proposed a real-time MPEG-4 VBR video traffic prediction algorithm that calculates the probability density function (PDF) based on the last N frames, rWin, by using Cubic-spline interpolation method, and then utilize it for the prediction of next frame. We fixed the size of rWin as five in the algorithm. Although the algorithm is capable of providing more accurate prediction than those in the research literature, it still has weakness on the adapting the traffic dynamics due to the fixed size of rWin. In this paper, we first study the experimental investigation about the number of rWin, and propose an enhanced traffic prediction algorithm with dynamic rWin.

A Congestion Control Algorithm in IEEE 802.11 Wireless LAN for Throughput Enhancements

This paper presents a congestion control algorithm, which uses cross-layered approach and rate-based transmission, for IEEE 802.11 wireless LANs (WLANs). The proposed algorithm considers the contention density which represents the degree of contention level experienced at a given station. From the contention density, each station can compute available bandwidth and adjusts its sending rate. The evaluation results show that throughput achieved by our algorithm is around 10% and about 20% at peak point, higher than that of TCP and TCP-SACK.