However, due to the non-orthogonality of the users' modulation signals, significant multiple access interference is possible even with power control. The use of multiuser signal processing at the receiver can combat this MAI effectively. In my research, I have developed multiuser channel estimation and detection schemes for CDMA systems that use long spreading codes. Long spreading codes have a period much larger than the symbol period and are used in practical CDMA systems. The use of long codes, as opposed to the commonly studied short codes that repeat every symbol, leads to significantly higher complexity.
Algorithms have to be designed to address the complexity and real-time implementation issues.
I have collaborated with other researchers at Rice, who are involved in DSP and VLSI implementation, to design algorithms that lead to more efficient hardware implementations. I have been part of the algorithm development team to prototype the wideband CDMA cellular standard as a component of the multitier network. Involvement in this project has provided a good understanding of the various existing wireless standards and led to several new research issues about the interaction of the physical layer and the various layers of the network that need to be addressed.