Smart Overlay Transmission for Spectrum Sharing with OFDM-based Incumbents
Date Issued
2015
Date
2015
Author(s)
Wang, Wei-Chen
Abstract
With the explosive growth of wireless devices and applications, wireless spectrum has become scarce. To solve this problem, spectrum sharing has been proposed in the past decade. Spectrum sharing is to share spectrum among multiple users and recent researches focus on sharing in licensed bands. The transmission schemes for spectrum sharing are commonly categorized into three paradigms including underlay, overlay and interweave. The mainstream scheme for spectrum sharing is interweave, where radio devices search for unused spectral bands and utilize these bands on an opportunistic basis. However, devices using interweave schemes must stop once primary users come back, which results in unpredictable service disruption. The corresponding service delay may be long and difficult to be estimated. In this thesis, we propose an overlay transmission scheme to enable simultaneous and interference-free transmission. Our solution works with OFDM-based primary users. By transmitting secondary data within the cyclic prefix (CP) of the OFDM symbols of primary users, simultaneous and interference-free transmission could be achieved and the service disruption caused by the unpredictable activities of the primary user could be alleviated. We have implemented our solution on the Universal Software Radio Peripherals (USRP) platform and applied to the Digital Video Broadcasting-Terrestrial (DVB-T) spectrum sharing networks. The experiment results show that the solution guarantees that even though the received secondary power strength is 30 dB higher than that of DVB-T transmitter, the DVB-T receivers would be still unaffected. When the IEEE 802.11g technologies is applied to our scheme in a 6 MHz TV band, secondary users could achieve a MAC-layer throughput of up to 970 kbps.
Subjects
dynamic spectrum access (DSA)
overlay transmission
spectrum sharing
coexistence
interference management
Type
thesis