Time filter

Source Type

Weng Y.-T.,National Cheng Kung University | Weng Y.-T.,Far East University of Taiwan | Shieh C.-K.,National Cheng Kung University | Huang T.-C.,Lunghwa University of Science and Technology | Miao Y.-B.,Information and Communications Research Laboratories
Proceedings of the International Conference on Parallel and Distributed Systems - ICPADS | Year: 2011

Digital multimedia broadcasting services require resiliency against signal fading due to signal encounters with bad weather, terrain obstructions, such as tree, building, etc. There are several solutions that use peer-to-peer network to repair packet losses. But they have some shortcomings such as long lookup latency, control message overhead, flash crowd problem and low chunk availability. In this paper we propose a novel solution that considers load distribution in structured peer-to-peer networks and repairing packet losses in short lookup latency. Our proposed solution doesn't need to modify the codec technology for multimedia stream. Our proposed solution can achieve load evenly distributed, high chunk availability, short lookup latency and low control message overhead by using peer-to-peer network to repair packet losses in digital multimedia broadcasting systems. © 2011 IEEE.

Chow C.W.,National Chiao Tung University | Yeh C.H.,Information and Communications Research Laboratories | Lo S.M.G.,Chinese University of Hong Kong | Li C.,Chinese University of Hong Kong | Tsang H.K.,Chinese University of Hong Kong
Optics Express | Year: 2011

The integration of passive optical network (PON) and radio-over-fiber (ROF) networks could provide broadband services for both fixed and mobile users in a single and low-cost platform. Combining the long-reach (LR)-PON (>100 km) and the LR-ROF can further reduce the cost by simplifying the network architecture, sharing the same optical components and extending the coverage of ROF network. However, the transmission and distribution of ROF signal in LR network is very challenging due to the chromatic dispersion generated periodic power fading and code time-shifting effects in the optical fiber. In this work, we propose and experimentally demonstrate a LR-ROF signal distribution using single-sideband (SSB)-ROF signal generated by a silicon ring-modulator. The silicon modulator is compact and has low power consumption. Besides, one unique feature of the silicon ring-modulator is that it only modulates the signal wavelength at the resonant null. This makes it very suitable for the generation of the SSB-ROF signal. Numerical comparison of the SSB-ROF with the double-sideband (DSB)-ROF and optical carrier suppress (OCS)-ROF signals; as well as the fabrication of the silicon ring-modulator will be discussed. ©2011 Optical Society of America.

Wong K.-L.,National Sun Yat - sen University | Lu J.-Y.,National Sun Yat - sen University | Chen L.-Y.,National Sun Yat - sen University | Li W.-Y.,Information and Communications Research Laboratories | And 2 more authors.
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2016

A 16-antenna array disposed in the smartphone for the LTE MIMO operation in the 3.5-GHz band (3400 ∼ 3600 MHz) is presented. The array is fabricated by disposing four quad- Antenna linear (QAL) arrays along two long side edges of the system circuit board of the smartphone. The QAL array has a planar structure occupying a small area of 3 mm X 50 mm. Two QAL arrays spaced 20 mm are disposed along each side edge. Acceptable antenna performances and ECC (envelope correlation coefficient) values are obtained for the antennas in the array. The calculated ergodic channel capacities of the 16-antenna array in a 16 X 16 MIMO system reach about 66 ∼ 72 bps/Hz with a 20-dB signal-to-noise ratio. The obtained results of the 16-antenna array are presented. © IEEE.

Chen C.-M.,Harbin Institute of Technology | Lin Y.-H.,Carnegie Mellon University | Chen Y.-H.,Information and Communications Research Laboratories | Sun H.-M.,National Tsing Hua University
Journal of Information Hiding and Multimedia Signal Processing | Year: 2013

Aggregation schemes for reducing transmission cost have been proposed for wireless sensor networks for a long time. Aggregated results can be easily altered by adversaries since sensors are prone to being captured in a harsh environment. Hence, several secure data aggregation schemes have been proposed to solve this problem. Many schemes ensure data integrity during aggregation procedures, but most of them are post-active since integrity can only be confirmed after the data reaches the base station. Another limitation is that the network topology is assumed to be fixed. However, this assumption violates the characteristic of sensor networks. In this paper, we present a secure data aggregation scheme called SASHIMI. SASHIMI utilizes successively hierarchical inspecting of message integrity during aggregation. If attacks arise during aggregation, attacks can be detected within two levels of the hierarchal tree structure. In other words, penalty and overhead caused by attacks can be reduced. In average, SASHIMI incurs only O(n) communication cost where n is the number of nodes. In the case of attacks, SASHIMI performs better than existing schemes. Moreover, SASHIMI supports dynamic network topology. Finally, a comprehensive analysis demonstrates that SASHIMI is more secure and efficient than other schemes. © 2013 ISSN 2073-4212.

Lin W.-Y.,University Road | Li M.-W.,University Road | Lan K.-C.,University Road | Hsu C.-H.,Information and Communications Research Laboratories
Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST | Year: 2012

802.11p, also known as WAVE, is a standard protocol intended for future traffic systems in order to support safety and commercial non-safety applications for vehicular communication. 802.11p is modified from 802.11a, and both are based on OFDM. The main difference between 802.11a and 802.11p is that the latter is proposed to use 10 MHz frequency bandwidth (half of bandwidth of 802.11a) in order to make the signal more robust against fading and increase the tolerance for multipath propagation effects of signals in a vehicular environment. In this paper, we investigate the performance difference between 802.11a and 802.11p for Vehicle-to-Infrastructure communication through real-world experiments. We measure contact duration and losses of 802.11p and 802.11a in both LOS and NLOS environments. In addition, we investigate their throughput with different modulations over various distances between OBU and RSU to evaluate the feasibility of using rate adaptation for non-safety V-to-I applications.

Discover hidden collaborations