| dc.description.abstract | Due to the fast development and wide spread of wireless communication technology in recent years, the current method of resource allocation cause poor utilization of spectrum. Cognitive Radio Network (CRN) is one of Dynamic Spectrum Access (DSA), which allows SU (Secondary User) using spectrums not being used by PU (Primary User). In order to improve utilization of spectrums, SU would leave current spectrum rapidly and switch to other usable spectrum to continue the transmission due to the presence of primary users. PU sensing is an important function in Cognitive Radio Network (CRN). When SU does not detect the presence of PU, SU would interfere the transmission of PU. When SU detected PU but it was absent, SU would cause poor utilization of spectrums.
Currently there are three types of hardware platforms of Cognitive Radio that are commonly used, which are USRP [1][2][3], KNOWS[4], and SpiderRadio[5]. Both KNOWS and SpiderRadio use Atheros wireless adapter and PC to implement Cognitive Radio Network (CRN). This is because currently only Atheros wireless adapter provides Linux open source driver - MADWIFI. Among the three platforms, SpiderRadio is the one that entirely uses Atheros wireless adapter to implement CRN. Therefore, it is the cheapest platform in hardware costs.
There are three commonly-used methods of PU sensing in CRN, which are Energy detection, Matched filter detection, and Feature detection. However, the hardware of Atheros can only support Energy detection and this function is implemented in hardware, there is no way to get modified. When Atheros receives error of Preamble in IEEE 802.11 Packet, it would report a “PHY error” and “CRC error” to MADWIFI driver. The finding in the experiment of recent research [13] shows that when PU signal presents, Atheros hardware would report “PHY error”. Hence, it uses “PHY error” to sense PU in Atheros hardware platform.
PB42 is an embedded system of Atheros, the advantages of PB42 are high movement, low cost, small size and low power consumption but low computation speed. Due to restrictions of hardware and software in embedded systems, PU detection scheme of SpiderRadio is not suitable in embedded system platform. We conducted several experiments to observe the characteristics of PHY error and we focused on more simple and effective method to implement PU detection in embedded system. | en_US |