P Vijay Kumar

IISc, Bengaluru

P. Vijay Kumar did his BTech and MTech at IIT Kharagpur, Kanpur, and Ph.D. at the University of Southern California (USC). He was a faculty member at USC from 1983-2003, a Professor at IISc from 2003-2021, and is currently an IISc Honorary Professor. His research interests include error-correcting codes and low-correlation sequences. He is a recipient of the 1995 IEEE Information Theory Society Prize Paper award. A pseudorandom sequence family co-designed by him formed the short scrambling code of the 3G WCDMA cellular standard. He is a recipient of the J C Bose National Fellowship and was a plenary speaker at the 2014 IEEE International Symposium on Information Theory. He is a Fellow of the INAE, IEEE, INSA, and IASc (2017).

P Vijay Kumar

Lectures by Fellows/Associates

G V Anand, Dayanand Sagar University, Bengaluru

The Novel (IZ4) Spreading Code Design for NavIC’s L1 SPS Signal

NAVigation with Indian Constellation (NavIC) is an indigenous regional navigation satellite system developed by ISRO, currently functional in L5 and S bands. A new standard positioning service (SPS) civilian signal is introduced in the L1 band, the legacy band for commercial applications. This called for designing a family of spreading codes or sequences, having symbol balance, low even and odd-correlation values, and, most challengingly, unconventional period 10230. In the Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS), this period was achieved by padding or truncating Weil sequences having prime period 10223 or 10243, respectively. Either truncation or padding generally degrades correlation performance. A novel design approach is adopted here under which the Interleaved Family of Z4-linear (IZ4) sequences of exact period 10230 is constructed through careful selection and interleaving of 5 nonlinear binary sequences. These sequences are, however, linear over the mod-4 ring Z4. Sequence selection was guided by connecting with exponential sums related to an elliptic curve. The IZ4 family has comparable odd-correlation performance and permits a simple, shift-register-based implementation. An Indian patent for the design has been granted, and ISRO will incorporate the IZ4 design into the L1 SPS signal of NavIC. This is joint work with ISRO scientists Dileep Dharmappa and Sugandh Mishra.

© 2022 Indian Academy of Sciences, Bengaluru.