Signal propagation in wireless communication systems, in the form of multiple hops or multiple rounds of communications, often creates redundancies that can be exploited to enhance transmission rate and reliability. Motivated by applications in wireless network coding and re-transmissions in automatic repeat request (ARQ), we consider a broadcast channel where the transmitter communicates a set of messages to multiple receivers, and each receiver possesses useful redundancy in the form of some prior side information about the messages. Communication in this broadcast channel is characterized by a trade-off between the amount of side information that a receiver has and the amount of signal-to-noise ratio required at this receiver for reliable decoding to take place. Based on this observation, we develop a communication theoretic framework for designing codes for this wireless channel. We identify a design parameter, called 'side information gain', that denotes the efficiency with which a coding scheme transforms receiver side information into performance improvements. We then present constructions of efficient modulation schemes and channel codes with large values of side information gains.
Lakshmi Natarajan was born in Chennai in 1987. He received the BE degree in electronics and communication from the College of Engineering, Guindy, in 2008, and the PhD degree from the Indian Institute of Science, Bangalore, in 2013. He is currently a postdoctoral Research Fellow at the Department of Electrical and Computer Systems Engineering, Monash University, Australia. His primary research interests are modulation, coding and signal processing for multi-terminal and multi-antenna communication systems. Dr. Natarajan was the recipient of the Seshagiri-Kaikini Medal 2013-14 for best PhD thesis, Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore. He was recognized as Exemplary Reviewer by the editorial board of the IEEE Wireless Communications Letters in 2013.