Hung-Yi Teng

A self-similar super-peer overlay construction scheme for super large-scale P2P applications

Unstructured peer-to-peer (P2P) overlay networks with two-layer hierarchy, comprising an upper layer of super-peers and an underlying layer of ordinary peers, are used to improve the performance of large-scale P2P applications like content distribution and storage. In order to deal with continuous growth of participating peers, a scalable and efficient super-peer overlay topology is essential. However, there is relatively little research conducted on constructing such super-peer overlay topology. In the existed solutions, the number of connections required to be maintained by a super-peer is in direct proportion to the total number of super-peers. For super large-scale P2P applications, i.e. the number of participating peer is over 1,000,000, these solutions are not scalable and impractical. Therefore, in this paper, we propose a scalable hierarchical unstructured P2P system in which a self-similar square network graph (SSNG) is proposed to construct and maintain the super-peer overlay topology adaptively. The SSNG topology is a constant-degree topology in which each node maintains a constant number of neighbor nodes. Moreover, a simple and efficient message forwarding algorithm is presented to ensure each super-peer to receive just one flooding message. The analytical results showed that the proposed SSNG-based overlay is more scalable and efficient than the perfect difference graph (PDG)-based overlay proposed in the literature.

Optimization of cloud resource subscription policy

In recent years, cloud computing has become a promising solution for decreasing the deployment and maintenance costs of Internet services. To provide Internet application service by using cloud resource, a service provider needs to consider the resource subscription cost and Service Level Agreement (SLA) of its users. Several kinds of pricing model of cloud resource subscription have been proposed. In such case, the Internet service provider plays the role of a cloud customer with a need of optimal cloud resource subscription policy to reduce its operation cost. Therefore, how to determine a suitable policy of cloud resource subscription has become a challenging issue. In this work, we proposed a two-phase approach to solve the cloud resource subscription problem. The first phase considered long-term resource reservation. In this phase, we proposed a mathematic model to compute an upper bound of the optimal amount of long-term reserved resource. The second phase was dynamic resource subscription phase. In order to overcome dynamic resource demand, in this phase, we used Hidden Markov Model (HMM) to predict resource demand and allocate VM resource adaptively based on the prediction. We evaluated our solution using real-world resource demand data. Our numerical results indicated that our approach can reduce the cost of cloud resource subscription significantly.

P2P SVC-encoded video streaming based on network coding

Along with rapid development of Internet technologies and widespread adoption of broadband residential access, video streaming service becomes a promising killer application. In order to solve device diversity, scalable video coding (SVC) has been standardized by the Joint Video Team of the ITU-T VCEG and the ISO/IEC MPEG. Using SVC, each device is capable of determining which layer should be decoded according to its capacities. On the other hand, comparing with traditional client/server architecture, peer-to-peer (P2P) technology can provide high scalability, high resilience, and prevent single point failure. Many studies have been proposed to improve the video quality under different considerations. However, little work has been done on transmitting SVC-encoded video based on P2P mesh topology. In this paper, a P2P SVC-encoded video streaming based on network coding (NC) is proposed. First of all, we propose a novel coding scheme, SVC-NC, for improving error robustness of SVC-encoded video. Second, we apply three scheduling mechanisms based on SVC-NC, startup request scheduling, priority request scheduling, and priority response scheduling to deliver SVC-encoded video more efficiently. Finally, we demonstrate the performance of our approach via simulation. The simulation results indicate that our approach can achieve low startup latency, smooth playback, and high video quality.

Optimal bandwidth adaptation for layered video multicasting in IEEE 802.11 WLANs

With widespread adoption of wireless local area networks (WLANs), video dissemination over wireless links such as video telephony, video gaming, and mobile TV broadcasting have become fast growing applications. Since wireless channel is error-prone, the receiving data rate of mobile stations (MSs) needs to be selected properly to avoid high packet loss rate and serious service quality degradation. In addition, to enhance reliability of video multicasting, application-layer forward error correction (AL-FEC) is a promising approach against packet losses. However, at the WLAN access point (AP), how to adaptively select a proper combination of transmission rate and AL-FEC code rate to multicast layered videos in WLANs becomes an important issue. In this paper, we propose a reward-based bandwidth adaptation mechanism to dynamically determine the best combination of transmission rate and AL-FEC code rate to multicast layered video in IEEE 802.11 WLANs. Our goal is to maximize the system reward which represents the video quality experienced on all users, under a given resource budget. A reward-based policy iteration algorithm is proposed as a heuristic approach to solve the optimization problem and its performance is compared with that of two baseline algorithms: exhaustive search and genetic algorithm. We demonstrate the performance of our approach via simulations. The simulation results show our approach can provide better service quality even through system resource is sparse.

SSNG: A Self-Similar Super-Peer Overlay Construction Scheme for Super Large-Scale P2P Systems

Unstructured peer-to-peer (P2P) systems with two-layer hierarchy, comprising an upper layer of super-peers and an underlying layer of ordinary peers, are used to improve the performance of large-scale P2P systems. In order to deal with continuous growth of participating peers, a scalable super-peer overlay topology with a lower diameter is essential. However, there is relatively little research conducted on constructing a scalable super-peer overlay topology. In the existing solutions, the number of connections that super-peers need to maintain is in direct proportion to the total number of super-peers which makes the solutions not scalable as well as not practical. Therefore, in this paper, we propose a scalable hierarchical unstructured P2P system which using a self-similar square network graph (SSNG) to construct and maintain the super-peer overlay topology dynamically. Moreover, a forwarding mechanism over SSNG is presented to enable each super-peer to receive just one flooding message. The analytical results show that the proposed SSNG-based overlay is more scalable and efficient than the perfect difference graph (PDG)-based overlay proposed in the literature.

Load Balancing with Cell Breathing in EPON-WiMAX Integrated Network

Multimedia applications over the Internet, such as IPTV and video on demand (VOD), have become fast growing applications in recent years. Such applications have stringent QoS constraints in terms of bandwidth, delay and packet loss. As a consequence, broadband access networks play an important role for multimedia applications. There are two emerging technologies offering both high bandwidth and QoS support, Ethernet Passive Optical Network (EPON) and Worldwide Interoperability for Microwave Access (WiMAX). By integrating these two technologies, EPON-WiMAX integrated network can: (1) provide broadband access, (2) support mobile users, and (3) decrease network planning cost and operating cost. Thus, EPON-WiMAX integrated network is an ideal choice for multimedia applications with ubiquitous access. In the EPON-WiMAX integrated network, ONU-BSs send the data received from the OLT to their subscribe stations (SSs) with QoS guarantee. However, some ONU-BSs could become hot-spots due to dynamics of mobility and bandwidth requirement of SSs. When an ONU-BS becomes overloaded, the QoS requirements would not be guaranteed and therefore the overall performance would be significantly decreased. In this study, a load balancing mechanism based on cell breathing was proposed for the hybrid EPON-WiMAX network. In the proposed approach, the load balancing problem was formulated into a linear programming problem. Our goal is to find the best power adjustment that maximizes system throughput. We present a Heaviest Load First Algorithm (HLFA) to obtain the optimal solution. We demonstrate the performance of our approach via extensive simulations. The simulation results show that the HLFA can provide the best solution to achieve load balancing and enhance the system throughput even though the system has multiple overloaded ONU-BSs.

Downlink packet scheduling and resource allocation in EPON WiMAX hybrid access networks

Multimedia applications over the Internet, such as IPTV and video-on-demand, have become fast growing applications in recent years. Such applications have stringent quality of services (QoS) constraints in terms of bandwidth, delay, and packet loss. As a consequence, broadband access networks play an important role for multimedia applications. There are two emerging technologies offering both high bandwidth and QoS support, namely Ethernet Passive Optical Network (EPON) and Worldwide Interoperability for Microwave Access (WiMAX). By integrating these two technologies, EPON-WiMAX integrated network can: (1) provide broadband access, (2) support mobile users, and (3) decrease network planning cost and operating cost. Thus, EPON-WiMAX integrated network is an ideal choice for multimedia applications with ubiquitous access. Although EPON-WiMAX integrated network has received growing attentions, however, most of previous works focus on the scheduling and bandwidth allocation in the upstream direction. Therefore, in this paper, we investigate the downlink scheduling and bandwidth allocation problem in EPON-WiMAX integrated networks. The objective of the study is to maximize the system throughput and guarantee the (QoS) so that the requirements of multimedia applications can be fulfilled. We proposed a two-stage downlink packet scheduling and resource allocation mechanism collaborating with application layer forward error correction (AL-FEC). We demonstrated the performance of our approach via simulations. Our simulation results indicated that the proposed mechanism increased the system throughput significantly, especially when AL-FEC is adopted.

Downlink resource allocation with cooperative transmission in EPON-WiMAX integrated network

The rapid growth of the demand of multimedia applications in recent years has posted a much higher bandwidth demand than before. As a result, the technology of broadband access is becoming more and more important. Integrating Ethernet Passive Optical Network (EPON) and Worldwide Interoperability for Microwave Access (WiMAX) has been considered as a very promising solution for broadband access. Although EPON-WiMAX has received many attentions in research, yet most of the previous researches focus on the uplink packet scheduling and bandwidth allocation. Thus, in our research, we focus on the downlink scheduling and resource allocation problem. In particular, we focus on utilizing the cooperative transmission technique. Based on the advantage of EPON-WiMAX architecture, the resource allocation problem utilizing cooperative transmission can be done at the optical line terminal (OLT) in a centralized manner. We first formulate the problem as a linear programming (LP) problem. Due to the high complexity of LP, we propose a heuristic algorithm to solve the problem. Our simulation results show that the proposed algorithm is able to increase the system throughput while guaranteeing the QoS of different classes of traffic.

Load balancing with cell breathing to maximize the system reward in mobile WiMAX

Worldwide Interoperability for Microwave Access (WiMAX) supports high bandwidth, broadband access, mobility, and Quality of Service (QoS) guarantee. Load balancing is required due to uneven distribution of traffic among different WiMAX base stations (BS) as well as mobility of WiMAX Subscriber Station (SS). Cell breathing is a well-known load balancing technique adopted in wireless networks. By changing transmission power of base stations, the technique is able to adjust traffic load of base stations. However, overloaded traffic cannot be alleviated by cell breathing without proper Call Admission Control (CAC). In this paper, we propose a directional cell breathing (DCB) mechanism combined with a Markov Decision Process based (MDP-based) CAC for achieving both load balancing and system reward maximization. In our approach, the call admission control problem is formulated as a Markov decision process such that the long-term reward loss rate can be calculated efficiently. Each BS then can adaptively select a proper power level for each of its directional antennas to minimize the long-term reward loss rate. We demonstrate the performance of our approach via simulations. The simulation results show that our approach provides an effective solution to achieve load balancing and reward maximization.

Downlink Scheduling and Resource Allocation in EPON-WiMAX Integrated Networks

Multimedia applications over Internet, such as IPTV and video on demand (VoD), have become fast growing applications in recent years. Such applications have stringent QoS constraints in terms of bandwidth, delay and packet loss. As a consequence, broadband access networks play an important role for multimedia applications. There are two emerging technologies offering both high bandwidth and QoS support, that is, Ethernet Passive Optical Network (EPON) and Worldwide Interoperability for Microwave Access (WiMAX). By integrating these two technologies, EPON-WiMAX integrated network can: (1) provide broadband access, (2) support mobile users, and (3) decrease network planning cost and operating cost. Thus, EPON-WiMAX integrated network is an ideal choice for multimedia applications with ubiquitous access. Although EPON-WiMAX integrated network has received growing attentions, however, most of previous works focus on the uplink scheduling and bandwidth allocation. Therefore, in this paper, we investigate the downlink scheduling and bandwidth allocation problem in EPON-WiMAX integrated networks. The objective of the study is to maximize the system throughput and guarantee the quality of service so that the requirements of multimedia applications can be fulfilled. We proposed a two-stage downlink scheduling and resource allocation mechanism collaborating with application layer forward error correction (AL-FEC). We demonstrate the performance of our approach via simulations. Our simulation results indicate that the proposed mechanism can increase the system throughput significantly, especially when AL-FEC is adopted.