Abstract: The present invention relates to a system and method for sending and receiving digital signals in a voice communication system. The system includes a data buffer, a tone detector, a speech encoder, and a transmitting unit. The data buffer receives and stores a digitized signal including voice band tone data and speech data. The tone detector detects the voice band tone data and generates at least one tone packet containing data indicative of the voice band tone data. The speech encoder encodes the speech data into a plurality of compressed speech packets. The transmitting unit in communication with the tone detector and the speech encoder transmits a packet message including tone packets and speech packets over an RF channel. The present invention also relates to a receiver including a speech decoder and a tone generator. The speech decoder decompresses speech packets to generate a digitized speech signal.

Abstract: An improved error control coding scheme is implemented in low bit rate coders in order to improve their performance in the presence of transmission errors typical of the digital cellular channel. The error control coding scheme exploits the nonlinear block codes (NBCs) for purposes of tailoring those codes to a fading channel in order to provide superior error protection to the compressed half rate speech data. For a half rate speech codec assumed to have a frame size of 40 ms, the speech encoder puts out a fixed number of bits per 40 ms. These bits are divided into three distinct classes, referred to as Class 1, Class 2 and Class 3 bits. A subset of the Class 1 bits are further protected by a CRC for error detection purposes. The Class 1 bits and the CRC bits are encoded by a rate 1/2 Nordstrom Robinson code with codeword length of 16. The Class 2 bits are encoded by a punctured version of the Nordstrom Robinson code. It has an effective rate of 8/14 with a codeword length 14.

Abstract: A receiver is connected to a satellite communication network. The receiver includes a satellite receiver card for receiving a packet containing data from the satellite communication network and a satellite receive device driver, associated with the satellite receiver card, for outputting the data in the packet in a format using a predetermined standard LAN interface format. The receiver may also include a key distribution unit for providing the satellite receiver card with keys for decrypting the data in the packet when the data is encrypted. The satellite receive device driver sends the satellite receiver card a list of addresses corresponding to destination addresses of interest, and the satellite receiver card discards the received packet if its destination address is not in the list of addresses.

Abstract: A method and system for using a low-cost, fixed output power radio in a multi-carrier communication system is disclosed herein. This system measures the output power of the multiple channel units within the system, obtains the current output power of the system, calculates a composite power and an expected power, compares the expected power and the current output power to calculate a gain adjustment value, and adjusting the output power of the system via the amplifier. The method for adjusting the power can also allow at least one of the carriers in the multi-carrier system to operate in a burst mode, and at least one of the remaining carriers to operate in a continuous mode during power measurement and gain adjustment steps.

Abstract: A wideband, wide angle sidelobe cancellation array system is disclosed. The system includes a main array formed of a plurality of regularly spaced elements, and an auxiliary array formed of two auxiliary antenna elements spaced from the outermost elements of the main array a distance equal to one-half the spacing of the main array elements. The received signals from the main array elements are combined to form a main array signal. The contributions from the auxiliary array elements are combined to form an auxiliary array signal. The two array signals have a good amplitude and phase match over a wide frequency and angle range. The main array and auxiliary array signals are then combined to form a system array signal wherein the sidelobe energy in the main array signal has been substantially cancelled. The system can be made an adaptive one by the addition of adaptive RF phase and amplitude weighting to the auxiliary array signal prior to combining with the main array signal.

Abstract: A method and apparatus for an adapter card, for use in a computer, to provide conditional access by the computer to incoming data streams while maintaining the security of information by maintaining a listing of addresses corresponding to data streams which the computer is authorized to receive, receiving and determining the address of a frame, determining whether the frame address matches an address maintained in an Access Table, and processing and transmitting only those frames of data streams which the computer is authorized to receive.

Abstract: A system and method for determining a timing error of an incoming signal, in one embodiment, receives the incoming signal into a receiver, and locates a known portion within a time frame of the incoming signal. The known portion is compared with a stored representation of the known portion, and with a stored representation of a derivative of the known portion. The timing error of the incoming signal is determined with respect to the clock signal based on the comparing of the known portion with the stored representations, and a subsequent known portion is located within a subsequent time frame of the incoming signal based on the timing error.

Abstract: A voice activity detector (VAD) which determines whether received voice signal samples contain speech by deriving parameters measuring short term time domain characteristics of the input signal, including the average signal level and the absolute value of any change in average signal level, and comparing the derived parameter values with corresponding thresholds, which are periodically monitored and updated to reflect changes in the level of background noise, thereby minimizing clipping and false alarms.

Abstract: A method of synthesizing an echo path in an echo canceller is provided. The method includes the steps of obtaining near end and far end signal samples at an echo canceller, locating the echo in a background task using a whitened version of the signal, transferring the echo location information to a foreground task, and eliminating the echo in the incoming signals by filtering the signal in the location passed to the foreground task by the background task.

Abstract: A system for noise canceling using a single return conductor. The system employs a first unit, a full duplex communications path coupled to the first unit, and a second unit coupled to the first unit via the full duplex communications path. The full duplex communications path employs at least three conductors: a forward signal carrying conductor; a reverse signal carrying conductor; and a single return conductor. In order to perform noise canceling, the first unit may employ, for example, a first adder coupled to the reverse signal carrying conductor, and a first canceling impedance coupled between the single return conductor and a first unit ground. Similarly, the second unit 12 may employ a second adder coupled to the forward signal carrying conductor, and a second canceling impedance coupled between the single return conductor and a second unit ground.

Abstract: In an improved system and method for paging cellular mobile stations, an incoming call signal intended for a paged cellular mobile station is received into a base station. Next, a page frame is assembled having a header that identifies the page frame as a hard page frame containing a prescribed number of mobile station identification numbers. The page frame contains an associated mobile station identification number associated with the paged cellular mobile station, and a dummy mobile station identification number. The page frame is transmitted to, and is disassembled within the paged cellular mobile station. The associated mobile station identification number is recognized within, the paged cellular mobile station, and, within each of a plurality of cellular mobile stations, the dummy mobile station identification number is ignored.

Abstract: An method for improved transaction reservation in an Integrated Satellite Business Network. The method includes generating a transaction request message indicating the number of slots needed to transmit a data message. Then, the method includes transmitting the transaction request message to a host terminal, and assigning one or more slots within an inroute to the remote terminal. The method then includes transmitting a transaction assignment message containing the number of slots assigned and which slots were assigned. In response to this assignment, the method includes transmitting at least a portion of the data message during the slots assigned.

Abstract: A method and apparatus for searching a program guide comprising program information for a plurality of different program sources. The program information includes the titles of the programs, the channel on which each program is to be shown, and the time at which each program is to be shown. The viewer first enters the title of a desired program. The program guide is then reviewed so as to identify each occurrence of the title of the desired program. If the desired program is contained in the guide, the time and channel associated with each identified occurrence of the program is displayed.

Abstract: The perception of speech processed by a CELP based coder, such as a VSELP coder, when operating in noisy background conditions is improved by removing swirl artifacts during silence periods. This is done by removing the low frequency components of the input signal when no speech is detected. A speech activity detector distinguishes between a periodic signal, like speech, and a non-periodic signal, like noise by using most of the VSELP coder internal parameters to determine the speech or non-speech conditions. To prevent the VSELP coder from determining pitches for non-periodic signals, a high pass filter is applied to the input signal to remove the pitch information for which the VSELP coder searches.

Abstract: A digital discontinuous cellular communication system has a transmitter that transmits two frames of data following detection of voice inactivity. A receiver includes a comfort noise generator that uses the two frames of data to output noise to the speaker during period of voice inactivity. The comfort noise generator includes synthesis codebook with samples scaled by actual background noise and excitation codebook with samples filtered and scaled by the background noise that are combined to produce comfort noise having attributes and loudness level of the received background noise prior to interruption of transmission. The scaled signals are weighted to vary the loudness level and spectral attributes.

Abstract: A digital filter includes a first memory device, a filter with at least one pole, i.e., a pole filter, coupled to the first memory device, and a second memory device coupled to the pole filter. The first memory device sequentially stores a digital signal in a forward sequence, and the pole filter sequentially reads the stored digital signal from the first memory device in a reverse sequence, thereby creating a time-reversed signal. The time-reversed signal is filtered by the pole filter, and is then stored as a filtered time-reversed signal in the second memory device in the forward sequence. A data signal is generated by the second memory device by reading the filtered time-reversed signal from the second memory device in the reverse sequence.

Abstract: A method of ensuring bandwidth availability for non-page point-to-point traffic in a communications system employs the steps of assembling a Superframe within a base station, and transmitting the Superframe from the base station to a radio unit. The Superframe is divided into a plurality of slots. A broadcast control channel is defined as a first portion of the plurality, and a point-to-point control channel is defined as a second portion of the plurality. The broadcast control channel has a Non-PCH Subchannel slot information element specifying a number of Non-PCH Subchannel slots within the point-to-point control channel.

Abstract: A RF sniffer module and method for detecting the availability of cellular communication channels for data transmission. The module monitors the channels used in a cellular communication network to determine when a particular channel is idle, meaning it is not being currently used for communication. The module communicates the status of the channel to an overlay system. Thus, the overlay system is informed that a particular channel is idle and thus can be used for data transmission or that the channel is not available and thus the overlay system can not use that channel without interfering with the operation of the cellular communication network.