Improving Performance of DS/SS-IVC Scheme Based on Location Oriented PN Code Allocation

Reiki KUSAKARI  Akira NAKAMURA  Kohei OHNO  Makoto ITAMI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E99-A    No.1    pp.225-234
Publication Date: 2016/01/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E99.A.225
Type of Manuscript: Special Section PAPER (Special Section on Intelligent Transport Systems)
inter-vehicle communication,  interference cancellation,  slotted ALOHA,  positioning,  location oriented PN code allocation,  

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Currently, IEEE802.11p and ARIB STD T-109 are available as the typical inter-vehicle communication (IVC) standards. Carrier sense multiple access/collision avoidance (CSMA/CA) and orthogonal frequency division multiplexing (OFDM) are used in these standards. However, the performance degrades when there are hidden terminals. In this paper, IVC system that using a direct sequence spread spectrum (DS/SS) modulation scheme is discussed because it has code division multiple access (CDMA) capability. In DS/SS-IVC scheme, it is possible to avoid hidden terminal problem. On the other hand, near-far problem (NFP), multiple access interference (MAI) and interference by equivalent pseudo noise (PN) codes occurs in DS/SS communication. These problems cause performance degradation. In this paper, interference cancellation scheme and slotted ALOHA scheme with code sensing are applied so as to mitigate the impact of MAI, NFP and interference by equivalent PN code. By applying interference cancellation scheme and slotted ALOHA scheme with code sensing, the performance of DS/SS-IVC is improved. In this paper, location oriented PN code allocation is focused on as a method of PN code assignment. However, DS/SS-IVC scheme based on location oriented PN code allocation has a problem. Since each vehicle obtain PN code based on the position that is estimated by GPS, performance degrades when GPS positioning error occurs. Therefore, the positioning system of DS/SS-IVC scheme is also discussed in this paper. Elimination of ranging data that has large ranging error is proposed in addition to interference cancellation scheme and slotted ALOHA scheme with code sensing in order to improve the performance of positioning. From the simulation results, the positioning error can be mitigated by applying these proposed techniques.