USC - Communication Sciences Institue

CSI Advances

This page contains a few topics in which CSI faculty, students, and alumni have made notable contributions. This content will change each time the page is loaded or you may view all summaries.

Spread-Spectrum Synchronization

Accurate synchronization plays a cardinal role in the efficient utilization of any spread-spectrum system. Typically, the process of synchronization between the spreading (incoming) pseudonoise code and the local dispreading (receiver) code is performed in two steps: first, code acquisition, then tracking via one of the available code-tracking loops. Professors Andreas Polydoros (CSi alumnus and former CSI faculty, now with the University of Athens, Greece) and Charles Weber developed a unified approach to serial search spread-spectrum code acquisition, which consolidated several earlier efforts into one general theory. The theory is formulated in a general manner that allows for significant freedom in the receiver modeling. The method has been widely used and adopted by most textbooks in the field. Various spread spectrum syschronization systems are special cases of this unified approach.

Ultrawideband Communications

Prof. Bob Scholtz is recognized as the primary academic figure in the UWB community, having written the earliest papers, obtained the first federal research grants, and organized the first workshops in the mid-1990s. Today, UWB systems are nearing standardization as part of the IEEE 802.15.3 group. Prof. Scholtz's first Ph.D. student working on UWB systems, Moe Win, is currently a faculty member at MIT. To learn more about Prof. Scholtz's UWB work, visit the Ultrawideband Radio Lab.

Per-Survivor Processing and Adaptive Iterative Detection

The Viterbi Algorithm is known to provide optimal data decisions for modulation, coding, and propagation channels that are modeled as finite state machines (FSMs). In many modern communications systems, however, the parameters that define transition probabilities are unknown or time varying. Per-Survivor Processing (PSP) was a term coined by Andreas Polydoros while a he was a professor at CSI in 1990. Prof. Polydoros and Visiting Prof. Riccardo Raheli, from U. of Pisa, Italy, developed PSP as a general tool for enabling a Viterbi-like algorithm to acquire or track changing channel conditions. Prof. Keith Chugg performed some of the basic analysis and theoretical justification of PSP and later, along with then CSI-Ph.D. student, Achilleas Anastasopoulos, generalized the notion to adaptive soft-in/soft-out decoding and data detection algorithms. This related advance enabled adaptive iterative detection (AID) and decoding algorithms that effectively estimate and track unknown or time-varying channel parameters such as carrier phase dynamics in turbo-like codes. PSP and AID have been implemented in a number of modems designed for mobile and satellite communication systems.

CSI Advances
		This page contains a few topics in which CSI faculty, students, and alumni have made notable contributions. This content will change each time the page is loaded or you may view all summaries. Spread-Spectrum Synchronization Accurate synchronization plays a cardinal role in the efficient utilization of any spread-spectrum system. Typically, the process of synchronization between the spreading (incoming) pseudonoise code and the local dispreading (receiver) code is performed in two steps: first, code acquisition, then tracking via one of the available code-tracking loops. Professors Andreas Polydoros (CSi alumnus and former CSI faculty, now with the University of Athens, Greece) and Charles Weber developed a unified approach to serial search spread-spectrum code acquisition, which consolidated several earlier efforts into one general theory. The theory is formulated in a general manner that allows for significant freedom in the receiver modeling. The method has been widely used and adopted by most textbooks in the field. Various spread spectrum syschronization systems are special cases of this unified approach. Ultrawideband Communications Prof. Bob Scholtz is recognized as the primary academic figure in the UWB community, having written the earliest papers, obtained the first federal research grants, and organized the first workshops in the mid-1990s. Today, UWB systems are nearing standardization as part of the IEEE 802.15.3 group. Prof. Scholtz's first Ph.D. student working on UWB systems, Moe Win, is currently a faculty member at MIT. To learn more about Prof. Scholtz's UWB work, visit the Ultrawideband Radio Lab. Per-Survivor Processing and Adaptive Iterative Detection The Viterbi Algorithm is known to provide optimal data decisions for modulation, coding, and propagation channels that are modeled as finite state machines (FSMs). In many modern communications systems, however, the parameters that define transition probabilities are unknown or time varying. Per-Survivor Processing (PSP) was a term coined by Andreas Polydoros while a he was a professor at CSI in 1990. Prof. Polydoros and Visiting Prof. Riccardo Raheli, from U. of Pisa, Italy, developed PSP as a general tool for enabling a Viterbi-like algorithm to acquire or track changing channel conditions. Prof. Keith Chugg performed some of the basic analysis and theoretical justification of PSP and later, along with then CSI-Ph.D. student, Achilleas Anastasopoulos, generalized the notion to adaptive soft-in/soft-out decoding and data detection algorithms. This related advance enabled adaptive iterative detection (AID) and decoding algorithms that effectively estimate and track unknown or time-varying channel parameters such as carrier phase dynamics in turbo-like codes. PSP and AID have been implemented in a number of modems designed for mobile and satellite communication systems.