Abstract: A digital (de)modulation system uses a larger code set of M codes for N length codes, where M>N, to provide an increased data rate while maintaining the coding gain. For example, the system can use 16 different codes each having a length of 11 chips in a code set while the conventional M-ary keying systems use a code set size of 8 for 11-chip codes or 8-chip codes. By extending the code set size, the system increases the data rate of the system. With 16 codes and the ability to change the sign of the code to be transmitted, the system can encode 5 data bits on both I and Q, so a total of 10 data bits can be encoded per code symbol. In this embodiment, a code symbol contains an 11 chip code on a I modulation branch and an 11 chip code on a Q modulation branch. As such, using 11 chip codes and a chip rate of 11 Mhz, the system provides a data rate of 10 Mbps while conventional M-ary keying systems can only achieve 8 Mbps using the same code length and chip rate.

Abstract: A digital modulation system provides enhanced multipath performance by using modified orthogonal codes with reduced autocorrelation sidelobes while maintaining the cross-correlation properties of the modified codes. For example, the modified orthogonal codes can reduce the autocorrelation level so as not to exceed one-half the length of the modified orthogonal code. In certain embodiments, an M-ary orthogonal keying (MOK) system is used which modifies orthogonal Walsh codes using a complementary code to improve the auto-correlation properties of the Walsh codes, thereby enhancing the multipath performance of the MOK system while maintaining the orthogonality and low cross-correlation characteristics of the Walsh codes.

Abstract: An apparatus and method for controlling the volume of a device's user alert sound based on an analysis of the device's environment. The device emits a signal and receives a resulting reflected signal. A processor measures characteristics such as the amplitude and/or delay of the reflected signal to determine the type of environment in which the communication device is located. The volume of the alert sound is then adjusted based on the type of environment indicated by the characteristics of the reflected signal. For example, if the characteristics indicate a closed environment, such as a briefcase, the volume is adjusted to high level, and if the characteristics indicate an open environment such as a desktop, the volume is adjusted to a low level.

Abstract: A method is described for producing coefficient leakage in an adaptive filter/equalizer without the need for using an adder/subtractor for each coefficient. Specifically, a method is provided for incrementally reducing the magnitude of one or more coefficients in an adaptive filter/equalizer solely through a defined manipulation of certain bits in that coefficient, such bit manipulation being carried out on a periodic basis. The period for such bit manipulation will generally track the frequency of adaptation iteration for such a filter/equalizer.

Abstract: A system and method are described for modulating phase and polarization aspects of an optical carrier signal with URZ and URZd coded representations of source data, where the source data itself is transmitted via an optical transmission system using UNRZ coding. At a receiver, the URZ and URZd signals are summed to provide a UNRZ equivalent encoding of the source data. That UNRZ-equivalent encoded signal is then combined with the received UNRZ signal to produce a composite UNRZ encoded representation of the transmitted source data. In carrying out the method of the invention, noise attributable to random fluctuations in phase and polarization of the optical carrier signal is reduced and the composite UNRZ coded signal obtained at the receiver provides a more reliable indicia of the encoded transmitted data.