Hughes Electronics Corporation

Hughes Aircraft Company

Claircom Communications Group, Inc.

Adrian J Morris

Allan B Lamkin

David Alan Roos

Prabhat K Gupta

Enrique Laborde

Robert Carroll Marquart

James Eryx Malcolm

W Robert Kepley

Shrirang Jangi

Seok Ho Kim

Stanley Edward Kay

Kumar Swaminathan

Andrew W Brandt

Neeraj Tewari

Randy Drago

Matthew M Mohebbi

Allan A D'Souza

Carle C Henson, Iii

James E Malcolm

Seok-Ho Kim

Steven M Kee

John R Clewer

Ashim Roy

Daniel Fraley

W Robert Kepley, Iii

A method and system for alerting a mobile terminal in a high-attenuation propagation environment within a mobile satellite communication network are disclosed herein. The method comprises receiving an incoming call directed to the mobile terminal, generating a paging signal in response to the incoming call, determining whether the mobile terminal has failed to receive the paging signal, and generating an alerting signal in response to the determination that the mobile terminal has failed to receive the paging signal. The system comprises a plurality of mobile terminals capable of receiving voice calls via a satellite; a satellite adapted to communicate with each of the mobile terminals, the satellite transmitting a spot beam to the mobile terminals; at least one gateway in communication with the satellite, the gateway having a first signal generator for producing a paging signal in response to an incoming call, logic for determining whether the mobile terminal has detected the paging signal, and a second signal generator for producing a high-power alerting signal in response to the logic; a first detector in the mobile terminal for detecting the paging signal; and a second detector in the mobile terminal for detecting the alerting signal.

Method and system for mobile alerting in a communication system

A method and system for adjusting the transmission power of a transmitter during a communication with a receiver in a mobile satellite communication system is disclosed herein. The method comprises establishing at least one threshold signal strength value for a transmitted burst; measuring the received signal strength of the burst received by the receiver; comparing the received signal strength with the threshold value; and setting a power control bit based on the comparison. The system comprises a plurality of mobile terminals having a first stored threshold value; a satellite adapted to communicate with each of the mobile terminals; at least one gateway in communication with the satellite, the gateway having a second stored threshold value, and including a routine for measuring the received signal strength of a burst signal transmitted from the mobile terminal, for comparing the received signal strength with the second stored threshold value, and for adjusting the transmission power of the gateway based on the comparison; and each of the mobile terminals including a routine for measuring the received signal strength of a burst signal transmitted from the gateway to the mobile terminals, for comparing the received signal strength with the first stored threshold value, and for adjusting the transmission power of the mobile terminal based on the comparison.

Power control for TDMA mobile satellite communication system

The present invention relates to a device and a method for communicating in a mobile communication system. The method provides a carrier signal having a plurality of frames. Each frame has a plurality of time slots, and each time slot comprises a plurality of transmission bits. A group of time slots are assigned to a communication channel. A traffic burst signal having a plurality of traffic symbols is transmitted over the communication channel by transmitting a first preamble over one of the assigned time slots, and transmitting a second preamble and at least one of the traffic symbols over at least one of the other assigned time slots. The second preamble occupies fewer transmission bits than the first preamble. The apparatus for transmitting a telephony signal over an RF channel includes a modem receiving a digitized PCM telephony signal and producing a traffic burst signal, and a transmitting unit in communication with the modem for transmitting a FDMA/TDMA signal carrying a plurality of traffic burst signals. At least one of the traffic burst signals carries a limited preamble message including a header field and a unique word field and at least one digitized voice message associated with a telephone call. Another traffic burst signal carries at least one signal acquisition message including a unique word field.

Device and method for communicating in a mobile satellite system

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.

Voice activity detector for speech signals in variable background noise

Noise is suppressed during pauses and silent periods in conversation, and voiced signals are freely passed in a mobile communications system thereby improving the quality of the transmitted speech. Noise suppression is implemented in such a way that a low level of noise is still allowed to pass to provide presence of the remote speaker; that is, the line is not made completely silent as this may falsely indicate that the connection has been interrupted. The noise suppression has an added feature of decreasing the background noise fractionally when voice is no longer detected. This provides perceptually improved quality of the communication.

Noise suppression in digital voice communications systems

A voice activity detector (VAD) which determines whether an input signal contains 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 predetermined threshold values. In order to further minimize clipping and false alarms, the VAD periodically monitors and updates the threshold values to reflect changes in the level of background noise.

The frequency and power of transmissions in a mobile communication system, such as an air-to-ground telephony system, are stabilized without a priori knowledge of the system gain factors or frequency references. The ground station monitors the available channels and modifies a vacant channel broadcast message to provide information that the channel is available. In this way, the air terminals have knowledge of all available channels. The ground station transmits a pilot signal. Upon request by a user for a dial tone at the air terminal, the air terminal selects a vacant channel and scans for the pilot signal. The air terminal estimates a distance to the ground station and sets a power level of a seizing transmission based on the estimated distance. The air terminal also estimates a Doppler frequency shift of the selected channel due to the relative movement of the air terminal with respect to the ground station and sets a frequency of the seizing transmission based on the estimated Doppler frequency shift. The air terminal then transmits a channel seizing signal at a reduced bandwidth less than a full normal bandwidth to the ground station at the set level and frequency. The ground station measures the level and frequency of the seizing signal and transmits to the air terminal information acknowledging the seizure of the selected channel and reporting the level and frequency of the seizing signal. The air terminal corrects the transmitted level and frequency and then switches the transmission bandwidth to the full normal bandwidth at the corrected level.

Stabilization of frequency and power in an airborne communication system

TDMA timing is maintained by the use of visibility information transmitted among the stations in a conference. Each station monitors the identity of stations from which bursts are received. A station also receives visibility information from other stations. The station combines the information to maintain a two-dimensional Visibility Designator Byte matrix or array. A station participates in the process by periodically transmitting its own VDB array to other stations. The stations then, independently, identify a prime station by using the collected and processed information. Using the same information, a station also identifies the manner in which it will lock to the timing of the prime station.

TDMA synchronization using visibility designation

Growing community of inventors

Gaithersburg, MD, United States of America

Adrian J Morris