Abstract: The mobile telephone system employs a fleet of satellites and a set of gateway ground stations arranged around the globe for handling communications to and from mobile communication units such as mobile telephones. Signals are transmitted between a subscriber unit and the nearest gateway via one or more of the satellites. The gateway is connected to a set of individual service providers such as local telephone systems. The individual service providers may be constrained for various reasons such as contractual or other legal constraints to handle communications only from subscriber units located in certain geographical areas such as within only certain countries or portions of countries. For a mobile communication from a particular subscriber unit, the gateway selects a service provider capable of handling the communication. In one implementation, the selection is based upon the location of the subscriber unit and upon any preferences specified by the subscriber unit.

Abstract: The probability based lock detection circuit determines whether a signal is sufficiently strong for communications in a mobile telecommunications system. If a signal is below a maximum energy threshold, the probability based lock detection is used to determine if the receiver is sufficiently capable to detect the signal and combine the signal with other signals received to obtain data transmitted by a mobile telephone. The probability based lock detection involves comparing index representations of maximums of 64 possible energies sent by the mobile telephone that identify that the signal was sent by mobile telephone. A mobile telephone sends signal that arrives to a base station through multiple paths to ensure accurate data transmission. Each signal includes data that identifies the mobile telephone.

Abstract: A method and apparatus for controlling a parameter associated with a first signal transmitted from a first station to a second station in a communication system monitors a second signal transmitted from the second station to the first station to determine a propagation state associated with the transmitted signals. A loop gain is adjusted based on the propagation state. The loop gain is used to adjust the size of commands used to adjust (i.e., increase or decrease) the parameter being controlled. If the propagation state is a quiescent state, the loop gain is set to one. If the propagation state is an active state, the loop gain is set to some value greater than one thereby increasing the size of the commands used to control the parameter. In a preferred embodiment of the present invention, the controlled parameter is a transmit power level of the first signal.

Abstract: A system and method for switching between power control modes is implemented in a communication system having two or more power control modes for providing a power increase for a transmitted signal. The system and method determine whether performance of the communication system is within nominal bounds. If the performance of the communication system is within nominal bounds, a first mode of power control is selected for controlling transmitter power. If the performance of the communication system is not within the nominal bounds, a second mode of power control for controlling a transmitter is selected.

Abstract: A dual-band helical antenna provides operation in two frequency bands. The dual-band helical antenna includes two single-band antennas, each having a feed network, a ground plane opposite the feed network, and a set of one or more radiators extending from feed network. According to one aspect of the invention, a tab extends from the feed network of one of the antennas which provides a feed for that antenna. The tab also provides a path for current to flow from the radiators of the second antenna along the axis of the second antenna to thereby increase the energy radiated in the directions perpendicular to the axis. According to another feature of the invention, the ground plane of one antenna is used as a shorting ring for the other antenna.

Abstract: In a time gated frequency division duplexing (FDD) data communication system, the base station transmits two data frames on the forward link to the first remote station and receives two data frames on the reverse link from the second remote station at the first time frame. At the second time frame, the base station transmits two data frames to the second remote station and receives two data frames from the first remote station. Data transmission and reception alternate over consecutive time frames. On the forward link, each data frame is covered with a unique Walsh code. The data is also spread with the short PNI and PNQ codes in accordance with the IS-95A standard. The data can be scrambled by the long PN code. The base station delays the long PN code and short PN codes and properly loads the Walsh codes so that the processed data can be properly demodulated and descrambled by the destination remote station.

Abstract: A method and apparatus for dynamically assigning identification information to mobile communication terminals (MCTs) in a satellite communication system. A subset of identification addresses is reserved out of an original set of addresses to be used for MCT identification on an as needed basis. When an MCT first acquires a signal from a first Network Management Computer (NMC), a first identification address is assigned to the requesting MCT for use in all subsequent communications. If the MCT later begins communications using a second NMC, the second NMC assigns a new identification address to the MCT and instructs the first NMC to withdraw the first identification address so it can be assigned to another MCT.

Abstract: A method and apparatus useful for determining the accumulated error in a user terminal dock in a satellite communications system. The satellite communications system includes a gateway, a satellite with a known position and known velocity, and a user terminal having a deskew buffer clocked by a user terminal clock. The method includes the steps of computing the one-way signal delay between the satellite and the user terminal, computing a desired deskew buffer delay based on the computed one-way signal delay and a predetermined maximum value of said one-way signal delay, and computing the accumulated error in the user terminal clock based on the desired deskew buffer delay and the actual deskew buffer delay.

Abstract: The present invention is a system and method for increasing user capacity on a slotted random access channel in a spread spectrum communications system by using a multi-part access probe. First and second parts of the access probe are modulated using a short PN code sequence, and the entire access probe is modulated using a long PN code sequence. Information to be transmitted by the access probe is modulated on the second part of the access probe, and the access probe is transmitted so that the first part of the probe falls within the boundaries of an access channel slot. In one embodiment, time slots in access channels used for access signal reception are made the length of the first part. In a further embodiment, time slots in a plurality of adjacent access channels used for access signal reception may be longer than said first part but are offset in time from each other by the length or period of the first part.

Abstract: In an orthogonal frequency division multiplexing (OFDM) system which uses an outer Reed-Solomon encoder and interleaver an inner convolutional encoder, after the inner convolutional encoding the data bits are interleaved, and then grouped into symbols, each symbol having "m" bits. After grouping, the symbols are mapped to a complex plane using quadrature amplitude modulation (QAM). Thus, bits, not symbols, are interleaved by the inner interleaver. A receiver performs a soft decision regarding the value of each bit in each complex QAM symbol received.

Abstract: A method and apparatus for controlling a power level of a transmitted signal sent from a second station to a first station in a communication system maintains a desired power level of a signal received at the first station. The first station sends a power control command to the second station directing the second station to either increase or decrease the power level of the transmitted signal. The first station generates the power control command based on the power level of the received signal, the desired power level, and at least one pending power control command. Pending power control commands include those power control commands that are propagating between the first station and the second station.

Abstract: A dielectric resonator antenna having a resonator formed from a dielectric material mounted on a ground plane. The ground plane is formed from a conductive material. First and second probes are electrically coupled to the resonator for providing first and second signals, respectively, to or receiving from the resonator. The first and second probes are spaced apart from each other. The first and second probes are formed of conductive strips that are electrically connected to the perimeter of the resonator and are substantially orthogonal with respect to the ground plane. The first and second signals have equal amplitude, but 90 degrees phase difference with respect to each other, to produce a circularly polarized radiation pattern. A dual band antenna can be constructed by positioning and connecting two dielectric resonator antennas together. Each resonator in the dual band configuration resonates at a particular frequency, thereby providing dual band operation.

Abstract: A method and apparatus for compressing fixed point signals without introducing a bias. Signals are compressed according to a dithered rounding approach wherein signal values are rounded up and rounded down with approximately equal probability, canceling the bias that would otherwise result from the rounding operation. Numerical properties of the input signal are exploited in order to determine whether the signal value should be rounded up or down. Signal compression may, therefore, be introduced at multiple points within a system without accumulating a signal bias and degrading downstream performance. Further, one bit signal compression may be achieved in a particularly efficient fashion with a minimal amount of hardware.

Abstract: The present invention is a system and method for accurately determining the distance (range) between one or more satellites and a user terminal and the rate of change (range rate) of that distance. When accurately determined according to the present invention, these quantities can be used to determine the location of the user terminal with a high degree of accuracy. When one satellite is available, the present invention determines the range and range rate based on the Doppler frequency shift that a signal experiences between the satellite and the user terminal, the round trip delay a signal experiences during transmission from the satellite to the user terminal and back via a satellite to a gateway, the Doppler frequency shift a signal experiences between the satellite and the gateway, and the timestamps of the measurements.

Abstract: A system and method for enabling multiple transmitters (400) to share a single code division multiplexed (CDM) or code division multiple access (CDMA) channel using orthogonal waveforms. A set of orthogonal channelizing codes W.sub.i (t) is generated, and each transmitter (400) is allocated orthogonal channelizing codes and pseudonoise polynomials in a predetermined manner. The transmitters channelize each user signal using an orthogonal channelizing code W.sub.i (t), and spread each user signal using a pseudonoise (PN) spreading code. Each transmitter employs the same PN spreading codes and time offsets. Additionally, no one orthogonal channelizing code is assigned to more than one transmitter during the time period they are sharing a CDM channel. The spread signals are summed at each transmitter (404) prior to transmission as a composite signal. The offsets are time-precorrected (406, 510) to ensure time alignment at the receivers.

Abstract: Apparatus and method for determining when a vehicle has arrived or departed from a planned or an unplanned stop, while minimizing or completely eliminating driver intervention. The apparatus comprises a mobile communication terminal located onboard a vehicle for receiving destination information, generally using wireless means, from a central facility or hub. A speedometer also located onboard the vehicle determines the speed of the vehicle and a position sensor onboard the vehicle determines the vehicle position. The vehicle speed and position are provided to a processor, also located onboard the vehicle, which uses the speed and position information to determine a vehicle arrival or departure from a planned or unplanned stop. The processor generates an indication of the event, either arrival or departure, directly to the central facility, to the vehicle operator, or both.

Abstract: An increased bandwidth patch antenna which includes first and second arms spaced by an air gap. The first and second arms are electrically connected by a bridge. A ground plane, which is approximately parallel to the first and second arms, is separated from the first and second arms by a dielectric substrate. In one embodiment of the present invention, the first arm is a radiating arm and the second arm is a tuning arm. By varying the length of the tuning arm, the bandwidth of the antenna is increased. The second arm, which also acts as a parasitic arm of the first arm, increases the gain of the antenna. A signal unit is electrically coupled to the bridge. The signal unit transmits and/or receives signals having a selected frequency band. The antenna resonates at the selected frequency band.

Abstract: A method and apparatus for reducing messaging traffic, including air and network messaging, in a wireless communication system. The invention informs a mobile station of its subscription status, either active or inactive, within the communication system. If the mobile station subscription status is inactive, the mobile station is prevented from registering with the communication system. All other functions of the inactive mobile remain enabled, such as the ability to make emergency calls, to change the subscription status to active status, or to allow for base station maintenance control.

Abstract: A system and method for determining the position of a user terminal (for example, a mobile wireless telephone) in a low-Earth orbit satellite communications system. The system includes a user terminal, at least one satellite with a known position and velocity, and a gateway (that is, a terrestrial base station) for communicating with the user terminal through the satellites. The method includes the steps of determining a range parameter and a range-rate parameter. A range parameter represents a distance between the satellite and the user terminal. A range-rate parameter represents a relative radial velocity between that satellite and the user terminal. The position of the user terminal on the Earth's surface is then determined based on the range parameter, the range-rate parameter, and the known position and velocity of the satellite.