Browsing by Author "Liu, Chin-Fu"

Now showing 1 - 3 of 3

Analysis and Practice of Uniquely Decodable One-to-One Code
(2013-01-01)
Liu, Chin-Fu
;
Lu, Hsiao-feng (Francis)
;
Chen, Po-Ning
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
In this paper, we consider the uniquely decodable one-to-one code (UDOOC) that is obtained by inserting a comma indicator, termed the unique word (UW), between consecutive one-to-one codewords for separation. As such, we analyze a class of UDOOCs and present practical algorithms for encoding and decoding such codes. Specifically, for various cases of UWs, we investigate the number of length-n codewords of UDOOCs and their asymptotic growth rates in n. The proposed encoding and decoding algorithms of UDOOCs can be implemented in parallel at low computational complexity without storing the codebook. Simulation results show that for proper choices of UWs, UDOOCs can achieve better compression efficiency than Lempel-Ziv codes even when the source is not statistically independent.
Cognitive Radio Enabled Multi-channel Access for Vehicular Communications
(2010)
Chu, Jui-Hung
;
Feng, Kai-Ten
;
Chuah, Chen-Nee
;
Liu, Chin-Fu
;
電機工程學系
The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access for vehicular environments (WAVE), where all the channels are periodically synchronized into control and service intervals. The communication device in each vehicle will stay at the control channel for negotiation and contention during the control interval, and thereafter switch to one of the service channels for data transmission in the service interval. The inefficiency of WAVE system comes from the fact that half of the time intervals of the service channels remain idle since all the stations are performing message contention within the control channel. In this paper, the cognitive radio-enabled multi-channel access (CREM) protocol is proposed to increase the channel utilization of IEEE 1609.4 standard. Based on the concept of cognitive radio, the vehicular stations are categorized into primary stations with safety-related messages and secondary stations with non-safety information to be delivered. Prioritized channel access is designed in the proposed CREM scheme in order to increase the transmission opportunity of primary stations. Moreover, extended time intervals are granted for primary stations to ensure reliability for data transmission. The enhanced CREM (CREM-E) protocol is proposed to further opportunistically increase the channel utilization of secondary stations. Simulation results show that the proposed CREM-E scheme outperforms the existing IEEE 1609.4 protocol with enhanced channel utilization and smaller waiting time intervals.
Performance Analysis of Fano Coding
(2015)
Krajci, Stanislav
;
Liu, Chin-Fu
;
Mikes, Ladislav
;
Moser, Stefan M.
;
電機學院
A rigorous performance analysis of Fano coding is presented, providing an upper bound on the average codeword length of binary and ternary Fano codes for an arbitrary discrete memoryless source. The performance bound is slightly better than Shannon\'s well-known bound for Shannon coding. As a by-product a novel general lower bound on Shannon entropy is derived that might be of interest also in a different context. This bound is expressed with the help of variational distance and provides a special case of a reverse Pinsker inequality.