Spectrum allocation for coexistence among heterogeneous secondary networks in Dynamic Spectrum Access
Date Issued
2014
Date
2014
Author(s)
Su, Yi-Hsien
Abstract
Dynamic spectrum access (DSA) is now widely considered as a solution to improve utilization of the television (TV) spectrum, where secondary devices may be temporarily allowed to access unused TV white space (TVWS). As a result, many secondary protocols have been designed to dynamically share the TVWS. Since these protocols are not compatible with each other, there will be interferences when all secondary protocols access the shared TVWS with equal priority. Therefore, the coexistence mechanism among heterogeneous networks needs to be resolved in DSA. The coexistence among heterogeneous networks in industrial, scientific and medical (ISM) bands has been addressed, where distributed solutions are used to facilitate the coexistence among WiFi, Bluetooth and Zigbee networks. However, the distributed solutions in DSA bands do not work as well as in ISM bands. One reason is that the huge difference in transmission power of heterogeneous networks in the TVWS leads to extremely unfair utilization of small-power networks. Such difference also makes the common radio solution infeasible because the communication between heterogeneous networks will be asymmetric. A centralized solution is preferred as a coexistence solution for DSA as unfair utilization for small-power secondary networks can be avoided. The existing centralized solutions had addressed some coexistence issues in DSA, including different channel availability perceived by secondary networks and varying spectrum availability. Nevertheless, none of them considers the channel switching delay. The switching delay is composed of the PHY switching time and the MAC-layer delay for disseminating switching messages within the entire network. The switching delay may be up to a few seconds when there are many devices in a (multi-hop) network. Such a long switching delay can be harmful to QoS and therefore cannot be ignored. In this project, we proposed a novel centralized spectrum allocation algorithm for DSA. Simulation results show that the proposed algorithm can achieve 6% to 13% gain of channel utilization comparing to the existing solutions.
Subjects
dynamic spectrum access
cognitive radio
channel hopping
heterogeneous networks
coexistence
Type
thesis
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