Peng-Jung Wu

Analysis and enhancement of multi-channel MAC protocol for ad hoc networks

In this paper, an analytical model is proposed to calculate the network throughput of dedicated control channel protocols that are designed to schedule multiple packets to be transmitted on different data channels simultaneously. Based on the analytical model, a scheme by tuning the initial contention window size is proposed to maximize the network throughput. We also present a novel multi-channel MAC protocol for single-hop scenario. Simulation results show that the proposed model is capable of modeling the behaviors of dedicated control channel protocols accurately. Furthermore, the proposed scheme can reduce the cost of collisions and enhance the network throughput up to 22% for 1 kB packet size and 80 nodes. Compared with other dedicated control channel protocols, the proposed protocol can schedule more control packets and use multiple channels more efficiently. Copyright

A Network Coding Equivalent Content Distribution Scheme for Efficient Peer-to-Peer Interactive VoD Streaming

Although random access operations are desirable for on-demand video streaming in peer-to-peer systems, they are difficult to efficiently achieve due to the asynchronous interactive behaviors of users and the dynamic nature of peers. In this paper, we propose a network coding equivalent content distribution (NCECD) scheme to efficiently handle interactive video-on-demand (VoD) operations in peer-to-peer systems. In NCECD, videos are divided into segments that are then further divided into blocks. These blocks are encoded into independent blocks that are distributed to different peers for local storage. With NCECD, a new client only needs to connect to a sufficient number of parent peers to be able to view the whole video and rarely needs to find new parents when performing random access operations. In most existing methods, a new client must search for parent peers containing specific segments; however, NCECD uses the properties of network coding to cache equivalent content in peers, so that one can pick any parent without additional searches. Experimental results show that the proposed scheme achieves low startup and jump searching delays and requires fewer server resources. In addition, we present the analysis of system parameters to achieve reasonable block loss rates for the proposed scheme.

Eliminating Packet Loss Accumulation in Peer-to-Peer Streaming Systems

To eliminate packet loss accumulation and overcome bursty packet loss problems caused by peer departures in peer-to-peer (P2P) streaming systems, a multisource structure combining with a distributed forward error correction (FEC) scheme is proposed. In the proposed structure, each peer connects to multiple parents according to the prespecified FEC packets ensemble and each parent forwards partial streaming packets to the peer. If one or few parents fail, other parents can still provide remaining part of streaming packets that can be used to recover the missing packets by using packet level FEC scheme. Packet loss probability and packet loss accumulation from parent peers to child peers in tree-based P2P streaming systems are investigated. The analysis and NS2 simulation results show that packet loss probability is reduced and furthermore the packet loss accumulation can be eliminated when an appropriate FEC protection is used.

I2CC: Interleaving two-level cache with network coding in peer-to-peer VoD system

Abstract As video technologies have advanced, peer-to-peer video-on-demand services have increasingly proliferated. In this paper, an interleaving two-level cache with network coding (I2CC) scheme is proposed to provide rapid content searching and efficiently support random seeking with the dynamic nature of peers. In I2CC, a video segment is composed of chunks, and each chunk is divided into blocks. These blocks are encoded by a network coding technique and distributed to different peers for storage in a local two-level cache, which includes a prefix cache and suffix cache. The prefix cache helps achieve rapid parent peer searching, low startup delays, and quick responses for jump operations. The suffix cache primarily provides a scalable cache size adjustment based on the limited storage space of peers. Additionally, enhancement and compensation mechanisms are provided to reduce playback delay and more efficiently utilize limited uploading bandwidth. We also present an analytical model for determining appropriate system parameters to reduce the chunk loss probability. Experimental results show that the proposed I2CC scheme outperforms competing schemes in terms of startup delay, jump delay, and server stress under different peer arrival times and video bitrates.

Receiver driven overlap FEC for scalable video coding extension of the H.264/AVC

In this paper, a receiver driven overlap Forward Error Correction (FEC) scheme, which offers unequal importance protection of video layers, is proposed to protect H.264/SVC video over the Internet. A mathematical model is provided to calculate video quality in terms of subjective Video Quality Metric (VQM). With the provided mathematical model, the video server prepares for receivers a lookup table, which lists all optimal combinations of video and FEC layers under various available downlink bandwidth and packet drop rates. By table lookup, a receiver can determine an optimal combination of video and FEC layers to subscribe to maximize the subjective video quality based on its available downlink bandwidth and packet drop rates.

Dynamic bandwidth recycle algorithm for OVSF–CDMA systems

This paper presents a dynamic bandwidth recycle algorithm in the downlink of a WCDMA system using orthogonal variable spreading factor codes (OVSF). It consists of a bandwidth recycle algorithm and a bandwidth reservation algorithm. The bandwidth recycle algorithm is used to recycle bandwidth from current serviced connections when the system does not have enough available bandwidth to support a bandwidth request. The bandwidth reservation algorithm is used to reduce transmission delay caused by suddenly increasing bandwidth requests. Four traffic classes, conversational, streaming, interactive, and background classes, defined by universal mobile telecommunication system (UMTS) are considered. Simulation results show that the bandwidth utilization and block rate are improved, the bandwidth guaranteed to conversational and streaming classes are protected, and the delay time of interactive and background classes are kept under an acceptable value even when the traffic load is heavy. Copyright

Overcoming burst packet loss in peer-to-peer live streaming systems

In this paper, we propose a multi-source multicast structure combining with a distributed FEC scheme to overcome burst packet loss problems caused by peer departures in P2P live streaming systems. The analytical results show that the burst packet loss can be eliminated by using multi-source structure with appropriate FEC parameters. A prototype system is implemented to verify that the proposed system is practically feasible and effective. The experimental results show the proposed system can effectively overcome the burst packet loss by taking advantage on the multiple source structure with the distributed FEC scheme.

A scheme for peer-to-peer live streaming with multi-source multicast and forward error correction

In this paper, we propose a scheme for peer-to-peer (P2P) live streaming with multi-source multicast and forward error correction. In our scheme, there is a control topology for membership management, and a multi-source multicast tree for data delivery. The control topology facilitates peers to locate multiple sources for media content, and the multi- source multicast tree make the system adaptive to node churn and packet loss. Simulation results show that the performance of our proposed method is significantly better than that of BitTorrent-Like (BT-Like) systems.