[show abstract][hide abstract] ABSTRACT: Since the multi-rate enhancements have been implemented in wireless ad hoc networks (MANETs), QoS-constrained multicast protocols for multimedia communication should be adapted to exploit them fully for using more efficiently the limited resources. To build a multicast tree with delay-guaranteed, one-hop delay and end-to-end delay must be known. The one-hop delay is the transmission time at a given link connecting two neighboring hosts, and the end-to-end delay is the time taken for a data packet from a specific source to reach the destination node. However, how to calculate the above two delays using the IEEE 802.11 MAC is still a challenging problem, because the radio channel is shared among neighbors. Further, the multi-rate enhancements make it more difficult since the neighboring relation among hosts is varied with the transmission rates. In this paper, we first propose a method to estimate the one-hop delay based on varied transmission rates by monitoring the sensed busy/idle ratio of shared channel. Then, by its aid, another method is proposed to compute the end-to-end delay. Finally, we integrate the above two methods with a typical multicast routing protocol, ODMRP, for constructing a delay-guaranteed multicast protocol. Simulation results show that the proposed method obtains more precise one-hop delay than a very recently work. Besides, the integrated protocol provides better delay guarantee than the existing protocol when the multicast traffic has delay requirement.
Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
[show abstract][hide abstract] ABSTRACT: The innovative exploitation of network coding technology could bring great design advantages to MANETs. First, wireless links are inherently lossy due to channel fading or interference. Second, the delivery condition of the route from the source to each receiver in a multicast transmission might be significantly distinct. Trying to satisfy the reliability requirement for the poorly-connected receivers may affect the performance of the rest of the receivers. In this paper, we present a tree-based multicast protocol, which exploits the characteristics of network coding to provide efficient and reliable multicast. A metric, named Receiving Probability (RP), is proposed to represent the probability for a node in a multicast tree to successfully receive a packet sent by the multicast source. To mitigate the distinctions among the receivers, the proposed multicast protocol aims to construct multiple trees such that the RP of each receiver satisfies a predefined threshold. Besides, since seldom redundant packets are generated with random network coding, by applying random network coding to these constructed multiple trees, differently coded packets can be transmitted on multiple trees, and the throughput of the reliable multicast can be improved. Simulation results show that the average throughput can be enhanced 30% and the throughput of the poorly-connected receivers can be enhanced 100% with our protocol, compared to a recent work.
39th International Conference on Parallel Processing, ICPP Workshops 2010, San Diego, California, USA, 13-16 September 2010; 01/2010
[show abstract][hide abstract] ABSTRACT: In this paper, we proposed a scaling algorithm based on inverse square law for bilinear interpolation. In order to use inverse square law, we modify bilinear interpolation. The image quality was compared with those of the conventional image scaling algorithms with Matlab. From the result, proposed algorithm has good quality and high sharpness. Our proposed algorithm uses 12 pixels of original image to calculate one pixel of scaled image. Our proposed algorithm has low complexity. We implemented a hardware design of inverse square law for bilinear using FPGA and display some test sense in an LCD (liquid crystal display) panel using a DVI (digital visual interface). It is verified that proposed algorithm has real-time image scaling.
Electronic Computer Technology, 2009 International Conference on; 03/2009
[show abstract][hide abstract] ABSTRACT: With the explosive growth of Internet, multicast service has been applied extensively and seriously. The IEEE 802.11 Wireless LAN has been deployed increasingly due to the demand for ubiquitous wireless data services. Because of the requirement of providing differentiated channel access to data traffic with different priority, the IEEE 802.11e has been proposed. However, the IEEE 802.11e does not support any MAC layer recovery on broadcast frame. Additionally, different distance between sender and receivers and different channel condition cause the sender has to use lower data rate to transmit multicast data. Thus the performance of all receivers is considerably degraded. Besides, in real channel condition, an unsuccessful transmission may happen due to link error or collision. As the number of wireless multicast receivers grows, the number of retransmission also increases and it will cause the waste of wireless bandwidth. In this paper, we focus on multicast in error-prone IEEE 802.11e infrastructure mode and present a group-based relay approach to improve the reliability and efficiency and to solve the abnormal phenomenon of transmission rate. This protocol is then compared with previous protocols for performance evaluation with analysis and simulation.