Abstract: A system and method for the efficient use of satellite radio modems and satellite bandwidth is disclosed. In the system and method, a satellite radio modem is used for PRACH requests, each PRACH request occupying 31.25 kHz in a packet data transfer channel. The packet data transfer channels can be either 125.0 kHz or 156.25 kHz. Therefore, four PRACH requests can be transmitted in any one packet data transfer channel. The packet data transfer channels are broken into eight time slots, and one time slot in each channel (either the odd frame or even frame) is dedicated to a PRACH request. A satellite radio modem for PDCH transfers is dedicated for each channel. The satellite radio modem assigned to receive the four PRACH requests is timeshared over 16 channels, thereby reducing the amount of satellite radio modems that would otherwise have been needed, had the PRACH request transmissions utilized a dedicated modem for each PRACH request, for each channel.

Abstract: A two-way satellite communication system is disclosed. A transceiver transmit signals over a return channel to a satellite and receives signals over a downlink channel from the satellite. A hub communicates with the transceiver over the return channel, wherein the hub provides connectivity between the transceiver and a packet switched network.

Abstract: A communications system includes a plurality of communications channels for transporting packets. The system also includes a gateway that is coupled to the communications channels. The gateway is configured to buffer a packet that is received over one of the communications channel from a first host in a queue and to determine a window value for maximizing transmission rate based upon occupancy of the queue. The gateway is configured to a second host according to a prescribed protocol to force use of the determined window value in the second host over another one of the communications channels. The present invention has particular applicability to an asymmetric bandwidth network, such as a two-way satellite system.

Abstract: A method for compensating for power variations in satellite communications includes measuring or estimating power variations for signals received at an earth-based terminal. The method also includes measuring or estimating changes in carrier-to-noise levels by a number of satellite terminals. The power variations may then be used to adjust the measured/estimated changes in carrier-to-noise (C/N) levels. The adjusted C/N levels may then be used to more accurately reflect actual network conditions and may be used in downlink power control related processing.

Abstract: An approach for scheduling packets within a terminal used in a satellite communications system is disclosed. A hub, in conjunction with a satellite, controls bandwidth allocations to a plurality of terminals, which are configured to issue bandwidth allocation requests to the satellite. Each of the terminals comprises a plurality of queues that are configured to store the packets; these queues are prioritized. A bandwidth-on-demand control logic prepares a schedule plan for transmitting the stored packets based upon current bandwidth allocations and the prioritization of the queues. The current bandwidth allocations are based upon prior bandwidth allocation and the stored packets. The schedule plan assigns the stored packets to packet transmission opportunities associated with the current bandwidth allocations.

Abstract: A method and apparatus for enhancing the performance of a network by performing selective spoofing, i.e., determining whether or not to spoof a connection. Selective spoofing provides the ability to discriminate among different connections, only allocating TCP spoofing resources to those where spoofing will improve performance and assigning spoofing parameters based on the specific applications using the connections. The selective spoofing is applicable to a wide variety of communication links, including both slow and fast links, high latency links, and links with low and high error rates. The selective spoofing functions are used either alone or together with other performance enhancing features. Those features include spoofing the conventional TCP three-way handshake, local data acknowledgement, multiplexing multiple connections across a single connection, data compression/encryption, prioritization, and path selection.

Abstract: A state transition diagram is presented for a user's access terminal for a satellite telecommunication system, showing the state of the access terminal's mobility management software layer, in response to various stimuli and conditions as the user enters into and out of various modes of operations, including deactivation, activation and illumination of a dark beam of a spot beam that is a shared resource.

Abstract: An uplink power control system for terminals in a satellite communication system provides closed loop power control using feedback signals generated at a satellite. The satellite performs inter-beam routing of uplink signals from satellite terminals, and processing of uplink signals to generate terminal transmission-specific feedback information that is transmitted in downlink signals to the terminals. The satellite also generates a beacon signal. An uplink power control algorithm at each terminal uses the beacon signal and feedback data to adjust transmit power.

Abstract: A method and system for acquiring a time division multiplexed synchronization signal in a satellite communication system is provided. The signal is provided as a series of frames with beacon signals time division multiplexed into at least one time slot of each frame. The beacon signal in each frame comprises a unique word sequence, which is the same in each frame, and a portion of a PN sequence. The entire PN sequence is distributed into a plurality of frames forming a superframe. Initially, the power level of the incoming signal is determined by locating the maximum power received in half time slot intervals. Next a series of frames are correlated against the expected unique word, each at one of a plurality of possible frequencies. The frequency generating the maximum correlation with the unique word is selected.

Abstract: An approach for processing packets for transmission over a satellite communications network is disclosed. A communication system includes a satellite terminal that provides connectivity for a host. The satellite terminal includes a user interface that receives a packet associated with an application from the host, and classification logic that classifies the packet into one of a plurality of transport services based upon the corresponding application. The satellite terminal also includes a mapping logic that maps the one transport service to one of a plurality of packet delivery services, wherein the one packet delivery service provides transmission of the packet to the satellite. The system also includes a hub that is configured to communicate with the satellite terminal over the satellite to provide the plurality of packet delivery services.

Abstract: An approach for performing synchronization is provided. Phase and timing offsets are first estimated in order to calculate a frequency offset. A receiver processes a signal received from a satellite and determine offset information. The receiver includes a phase estimator for estimating a phase offset of the received signal, a timing estimator for estimating a timing offset of the received signal, and a frequency estimator for deriving a frequency offset from the phase and timing offset. A determination is made as to whether the sampling was done at a peak wave point of the data.

Abstract: Filtering loop and method for maintaining synchronization between a receiver and a transmitter reduces overhead and enables more robust operation. The method includes the step of receiving an error signal corresponding to a synchronization parameter. A first order filter is applied to the error signal such that a residual signal results. The method further provides for compensating the residual signal for drift such that the compensated residual signal estimates a rate of change in the residual signal. By compensating the residual signal for drift, difficulties associated with time lag and signal degradation are obviated.

Abstract: An approach is provided for compensating for non-linearity in an overlaid radio communication system, such as a satellite network, wherein a terminal and a hub station communicates bi-directionally using a composite signal that is transmitted from a relay station and includes an inbound signal overlaid with an outbound signal. A look-up table stores information used to determine an inverse of a function associated with a non-linear effect of a received composite signal. The inbound signal has a predetermined spectral configuration. The device also includes a multiplier configured to generate a product of the look-up table and the received composite signal. Also, the device includes an estimation module configured to output an estimate of the inbound signal based upon the product.

Abstract: A communication system having a proxy architecture is disclosed. The system includes a platform that provides performance enhancing functions. The platform includes a backbone connection apparatus that routes information within a communication system. The backbone connection apparatus receives backbone connection parameters from the platform and maintains the current parameters in one or more backbone connection profiles. The backbone connection apparatus routes packets of information throughout the communication system based on the backbone connection profile. The backbone connection apparatus supports the use of different backbone protocol for different types of backbone links. Further, in a configuration where multiple backbone links of different types exist, the backbone connection apparatus supports the use of a different backbone protocol for each type of link at the same time.

Abstract: A communication system having a proxy architecture is disclosed. The system includes a platform that provides performance enhancing functions. The platform includes a path selection/activation apparatus that routes information within a communication system. The path selection/activation apparatus receives path selection and path activation parameters from the platform and maintains the current parameters in one or more path selection/activation profiles. The path selection/activation apparatus routes packets of information throughout the communication system based on the path selection and/or path activation profile. The above arrangement has particular applicability to a bandwidth constrained communication system, such as a satellite network.

Abstract: Two types of contention channels are used to accommodate broadband packet data in a satellite communication network. A first contention channel is used by unsynchronized user terminals to access the system and request a traffic channel. The first contention channel is of a sufficient duration to accommodate a RACH message, as well as the timing uncertainty between user terminals within a given spot beam. A second contention channel is shorter in duration than the first contention channel, and is narrowband, so that more than one second contention channel may be transmitted within the bandwidth of the broadband traffic channels. The second contention channels are used by synchronized user terminals for transmitting packet RACH, or PRACH, messages. The more efficient nature of the PRACH channels accommodates the increased overhead associated with bursty packet data, without the capacity cost of the longer duration RACH channel.

Abstract: Spread spectrum receiver includes a delay locked loop (DLL) circuit for holding the synchronization of a despread signal with a received spread spectrum signal. The DLL circuit comprises a subtracter for generating a signal representative of a subtraction between first and second correlation signals, a positive feedback amplifier for amplifying the subtraction representative signal and a window comparator for producing a lock signal when the subtraction representative signal is positioned within a window width.

Abstract: A distributed, demand access local loop telephone system is disclosed. An optical fiber, or fibers, connect a central office and a plurality of remote units which are located near subscriber populations. Communications on the fiber is by high speed digital data stream which is comprised of a plurality of bit multiplexed PCM channels, each of bandwidth equivalent to a VF channel or greater. The remote units are connected to the subscriber equipment (e.g. telephones or other data sources/sinks) by subscriber dedicated links (e.g. wire pairs or other cabling), and the remote units may be added, subtracted, or moved along the fiber path to reconfigure the overall system. Because of the demand access nature, the fiber bandwidth can be dynamically redistributed among the remote access units at high speed and controlled at the central office. The topology of the system can also be reconfigured, within limits, from a central site.

Abstract: A collision detection mechanism includes a transmission protocol which locates a gap in a station's transmission, of fixed duration and position, relative to start of transmission. Collision detection is enhanced since random timing of collisions normally results in filling in the gap. This condition is more readily detectable than detecting the simultaneous presence of energy from two transmitters. The transmission protocol is followed unless the transmitting station detects a collision, in which event gap creation is inhibited. The gap detecting equipment may be located at a network head end.