Dong Nguyen

Wireless Broadcast Using Network Coding

Traditional approaches to reliably transmit information over an error-prone network employ either forward error correction (FEC) or retransmission techniques. In this paper, we propose some network coding schemes to reduce the number of broadcast transmissions from one sender to multiple receivers. The main idea is to allow the sender to combine and retransmit the lost packets in a certain way so that with one transmission, multiple receivers are able to recover their own lost packets. For comparison, we derive a few theoretical results on the bandwidth efficiency of the proposed network coding and traditional automatic repeat-request (ARQ) schemes. Both simulations and theoretical analysis confirm the advantages of the proposed network coding schemes over the ARQ ones.

Multimedia wireless transmission with network coding

In recent years, Wireless Local Area Networks (WLAN) have become the premier choice for many homes and enterprises. WiMAX (Worldwide Interoperability for Microwave Access) has also emerged as the wireless standard that aims to deliver data over long distances, and can potentially provide wireless broadband access as an alternative to the wired cable and DSL networks. Parallel with the surge of wireless networks is the explosive growth of multimedia applications. Therefore, it is important to explore efficient methods for delivering multimedia data in such wireless settings. In this paper, we propose a network coding based scheduling policy to be used at WLAN-like Access Point (AP) or at a WiMAX-like broadcast station that optimizes the multimedia transmission in both broadcast and unicast settings. In particular, the contributions of this paper include (a) a framework for increasing the bandwidth efficiency of broadcast and unicast sessions in a wireless network based on network coding techniques and (b) an optimized scheduling algorithm based on the Markov Decision Process (MDP) to maximize the quality of multimedia applications. Simulations and theoretical results demonstrate the advantages of our approach over the conventional techniques.

Hybrid ARQ-random network coding for wireless media streaming

This paper proposes hybrid ARQ-random network coding frameworks for real-time media broadcast over single-hop wireless networks. We model the wireless channel as a packet erasure channel and our proposed schemes aim at minimizing the packet erasure rate in order to enhance the media quality at receivers. We consider two forms of random network coding: uniform random network coding (URNC) and hierarchical random network coding (HRNC) in combination with a number of packet scheduling policies based on a limited number of feedbacks from receivers. Our simulation results show that the hybrid frameworks can improve the quality of media applications significantly compared with the conventional scheme without using network coding.

Network coding-based wireless media transmission using POMDP

We consider the problem of joint network coding and packet scheduling for multimedia transmission from the Access Point (AP) to multiple receivers in 802.11 networks. The state of receivers is described by a hidden Markov model and the AP acts as a decision maker which employs a partially observable Markov decision process (POMDP) to optimize the media transmission. Importantly, we introduce a simulation-based dynamic programming algorithm as a solution tool for our POMDP abstract. Our simulation-based algorithm simplifies the modeling process as well as reduces the computational complexity of the solution process. Our simulation results demonstrate that the proposed scheme provides higher performance than the network coding scheme without using optimization techniques and traditional retransmission scheme.

Joint Network Coding and Scheduling for Media Streaming Over Multiuser Wireless Networks

We formulate the problem of network-coding (NC)-based scheduling for media transmission to multiple users over a wireless-local-area-network-like or WiMAX-like network as a Markov decision process (MDP). NC is used to minimize the packet losses that resulted from unreliable wireless channel conditions, whereas the MDP is employed to find the optimal policy for transmissions of unequally important media packets. Based on this, a dynamic programming technique is used to give an optimal transmission policy. However, this dynamic programming technique quickly leads to computational intractability, even for scenarios with a moderate number of receivers. To address this problem, we further propose a simulation-based dynamic programming algorithm that has a much lower run time yet empirically converges quickly to the optimal solution.

Joint network coding and power control for cellular radio networks

We investigate the problem of optimizing power consumption and bandwidth usage in cellular radio networks. In this paper we consider a wireless broadcast network, organized in cells, in which each transmitter wants to deliver the same amount of data to all receivers inside its cell. Traditionally, the transmitter in each cell radiates a fixed power at which the receiver at the border of the cell can receive, in theory, a signal whose energy is greater than its required threshold and satisfies condition of signal to noise and interference ratio (SIR). When a receiver in a cell receives an error packet, the transmitter in that cell will retransmit until the receiver receives it successfully. Instead in network coding approach, the transmitter will store index of the error packets, then it will consider combining them before sending out. The goal of this paper is to provide an analysis on the power consumption and bandwidth utilization of network coding techniques at the signal layer. Especially, we propose a novel technique in which network coding and adaptive power control are joined together to improve network performance. The simulation results show that our proposed technique substantially reduces power consumption while increases the network throughput compare with the traditional transmission technique, Automatic Repeat reQuest (ARQ).

A Case for Joint Network Coding and Power Control in Wireless Linear Networks

We investigate the power consumption and bandwidth usage for information exchange between two terminal nodes in a linear wireless ad hoc network. Specifically, we propose a joint network coding and adaptive power control (NCPC) scheme which regulates the transmission power to reduce the overall energy usage and to increase the bandwidth efficiency. Analysis and numerical results show that our proposed technique reduces power consumption while increasing the network throughput as compared with the existing transmission techniques.

Zika preparedness and response in Viet Nam

Disclaimer The findings and conclusions in this article are those of the authors and do not necessarily represent the official positions of the United States Centers for Disease Control and Prevention.