Reliable Broadcast to A User Group with Limited Source Transmissions

In order to reduce the number of retransmissions and save power for the source node, we propose a two-phase coded scheme to achieve reliable broadcast from the source to a group of users with minimal source transmissions. In the first phase, the information packets are encoded with batched sparse (BATS) code, which are then broadcasted by the source node until the file can be cooperatively decoded by the user group. In the second phase, each user broadcasts the re-encoded packets to its peers based on their respective received packets from the first phase, so that the file can be decoded by each individual user. The performance of the proposed scheme is analyzed and the rank distribution at the moment of decoding is derived, which is used as input for designing the optimal BATS code. Simulation results show that the proposed scheme can reduce the total number of retransmissions compared with the traditional single-phase broadcast with optimal erasure codes. Furthermore, since a large number of transmissions are shifted from the source node to the users, power consumptions at the source node is significantly reduced.Comment: ICC 2015. arXiv admin note: substantial text overlap with arXiv:1504.0446

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

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