Low Overhead Query Method for the Interface between Geo-Location Database and Secondary User

Ha-Nguyen TRAN
Hiroshi HARADA

IEICE TRANSACTIONS on Communications   Vol.E98-B    No.4    pp.714-722
Publication Date: 2015/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E98.B.714
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
white space,  cognitive radio,  geo-location database,  available channel,  polygons intersection,  

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Accessing a geo-location database is one of the approaches for a secondary user (SU) to obtain the list of available channels for its operation. Channel availability is calculated based on information stored in the geo-location database and information submitted by the SU so that primary users (PU) are protected from harmful interference. The available channel checking process is modeled as a number of intersection tests between the protected contours of PUs and the operation area of the SU regarding to all potential channels. Existing studies indicated that these intersection tests consume time and introduce overhead to the database, especially when the contours or the operation areas are represented by n-polygons and the number of vertices n is a large number. This paper presents a novel method of determining available channels which reduces the number of intersection tests. By submitting SU's preferred channels or the number of channels to be checked to the database, the calculation time and database's load will be reduced significantly. This paper also presents analysis and simulation results of the database workload and the average number of channels obtained per query on different query methods. Suitable query method can be selected based on the number of similar channels in neighbor areas and the maximum number of intersection tests.