Paul E. Jacobs

Variable rate vocoder

A method of speech signal compression, by variable rate coding of frames of digitized speech samples, comprising the steps of: determining a level of speech activity for a frame of digitized speech samples; selecting an encoding rate from a set of rates based upon said determined level of speech activity for said frame; coding said frame according to a coding format of a set of coding formats for said selected rate wherein each rate has a corresponding different coding format and wherein each coding format provides for a different plurality of parameter signals representing said digitized speech samples in accordance with a speech model; and generating for said frame a data packet of said parameter signals.

QCELP: A Variable Rate Speech Coder for CDMA Digital Cellular

Digital cellular telephone systems require efficient encoding of speech to achieve capacity improvements required of the next generation of cellular systems. The use of a variable rate speech coder can reduce the average data rate required to transmit conversational speech by a factor of two or more, while providing many other advantages. This reduction in average data rate leads to a factor of two increase in the capacity of a Code Division Multiple Access, or CDMA, based digital cellular telephone system by decreasing the mutual interference among users. This chapter describes “QCELP,” a variable rate speech coder which has been selected as the speech coding algorithm for the TIA North American digital cellular standard based on CDMA technology.

Efficient motion planners for nonholonomic mobile robots

Deals with the problem of motion planning for a car-like robot (i.e. a nonholonomic mobile robot whose turning radius is lower bounded). The authors present a fast and exact planner based upon recursive subdivisions of a collision-free path generated by a lower-level geometric planner which ignores the motion constraints. The resultant trajectory is optimized to give a path which is of near-minimal length in its homotopy class. The claims of high speed are supported by experimental results for several implementations which assume different geometric models of the robot.<<ETX>>