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.

The Baum-Welch Algorithm

The Baum-Welch algorithm was developed by Prof. Lloyd Welch prior to his joining the CSI faculty. Prof. Welch developed this algorithm in collaboration with his colleague, Dr. Leonard Baum, while both were at the Institue for Defense Analysis (IDA). The Baum-Welch algorithm optimizes the parameters of a finite-state machine (FSM) model using empirical observations. This is a two step process; step one is computing a-posteriori probabilities for a given model, and step two involves re-estimation of the model parameters. The Baum-Welch algorithm has become an important tool in many fields, speech recognition in particular. It has also served as motivation for other algorithms. One example is the so-called Expectation-Maximization (EM) algorithm, of which the Baum-Welch algorithm is a specific case. Another is the forward-backward algorithm (FBA or BCJR algorithm), which is step one of the Baum-Welch algorithm. The FBA has gained recent noteriety as a key component of the turbo-decoding algorithm.

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.

The NASA Space Shuttle Radar

The architectural design of the Ku-band Space Shuttle Radar was developed by Prof. Charles Weber for the NASA Manned Space Center. The short range and docking radar was designed to track its targets to a range as short as 30 meters, where station-keeping and rendezvous take place, as well as up to distances of 300 N. Mi. Target parameters measured by the radar during the tracking phase include: range and range rate, and angle and angle rate (elevation and azimuth). The system is a coherent pulse Doppler type radar with a peak power of 60 watts. The radar has enjoyed an excellent performance record throughout the Shuttle Program.

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. The Baum-Welch Algorithm The Baum-Welch algorithm was developed by Prof. Lloyd Welch prior to his joining the CSI faculty. Prof. Welch developed this algorithm in collaboration with his colleague, Dr. Leonard Baum, while both were at the Institue for Defense Analysis (IDA). The Baum-Welch algorithm optimizes the parameters of a finite-state machine (FSM) model using empirical observations. This is a two step process; step one is computing a-posteriori probabilities for a given model, and step two involves re-estimation of the model parameters. The Baum-Welch algorithm has become an important tool in many fields, speech recognition in particular. It has also served as motivation for other algorithms. One example is the so-called Expectation-Maximization (EM) algorithm, of which the Baum-Welch algorithm is a specific case. Another is the forward-backward algorithm (FBA or BCJR algorithm), which is step one of the Baum-Welch algorithm. The FBA has gained recent noteriety as a key component of the turbo-decoding algorithm. 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. The NASA Space Shuttle Radar The architectural design of the Ku-band Space Shuttle Radar was developed by Prof. Charles Weber for the NASA Manned Space Center. The short range and docking radar was designed to track its targets to a range as short as 30 meters, where station-keeping and rendezvous take place, as well as up to distances of 300 N. Mi. Target parameters measured by the radar during the tracking phase include: range and range rate, and angle and angle rate (elevation and azimuth). The system is a coherent pulse Doppler type radar with a peak power of 60 watts. The radar has enjoyed an excellent performance record throughout the Shuttle Program.