GNU Radio + USRP2 Implementation of a Single-Carrier Zero-Correlation-Zone CDMA System

Abstract: GNU Radio is a software defined radio in which components implemented in hardware are implemented using the software. GNU Radio works along with the USRP board. The USRP board is used to transmit and receive the signal in the wireless channel. CDMA system using the ZCZ (zero Correlation Zone) code is needed to be implemented in the GNU Radio and USRP board. Primary implementation and testing of CDMA using the ZCZ code is done with Matlab. The ZCZ come with the property of ideal impulsive auto correlation and zero cross correlation property within its ZCZ. However the Matlab implementation is not enough to make the system work using the USRP board. It is needed to be modified and implemented in GNU Radio to make the USRP board work. Unlike the simulation done in the Matlab there are lot of problems involved in real-time implementation of the idea in GNU Radio. In Matlab there are lot of in built functions which are needed to be implemented manually in C++. In GNU Radio a chunk of data received at a particular instant may not be of same length all the time and it keeps varying, should be handled properly. For the feedback implementation such as code tracking needed to be handled carefully and all the feedback variables needed to be present in a single module. ZCZ code for single user system, that is one transmitter and one receiver has worked well, but the ZCZ code for multi user uplink had to be tested too. This thesis aims at converting the Matlab implementation of ZCZ codes into real time GNU Radio implementation that works using the USRP board. This thesis will check the real time implementation of ZCZ code using USRP board and GNU Radio. This is done by implementing spreading of data at the sender side using ZCZ code, code synchronization at the receiver, code despreading at the receiver without code tracking and code despreading with code tracking are all done using ZCZ codes. This thesis also checks the feasibility of an asynchronous multi user communication without strict timing synchronization among the users with good results.