摘要:
A satellite communication system uses dual satellite coverage techniques to simulate the provision of full duplex communications in the system. Each subscriber (100) in the system communicates with two satellites (102, 104) that use complementary time division duplex (TDD) frame structures (50, 72) for communicating with the subscriber (100). In one embodiment, each satellite in the system performs a transition between a first TDD frame structure (50) and a second TDD frame structure (72) while travelling through a transition region (102) of an associated orbit (130). Preferably, the transition is performed gradually so that an abrupt reduction in system capacity is avoided. In another embodiment, individual orbital planes in the satellite system are dedicated for use with particular TDD frame structures. A subscriber thus communicates with one satellite in each of two planes during a connection.
摘要:
A satellite-based communications system (20) includes a communication satellite (22) using a Time Division Duplex (TDD) frame structure. The communication satellite (22) transmits first data (63) during a first sub-frame (150) and receives second data (65) during a second sub-frame (152) of a time division multiple access (TDMA) frame (144). A terrestrial repeater (30) receives the first data (63) using a first link (36) during the first sub-frame (150), delays the first data (63) by a sub-frame duration, and transmits the first data (63) to a subscriber unit (32) using a second link (42). The terrestrial repeater (30) receives the second data (65) from the subscriber unit (32) using the second link (42), delays the second data (65) by the sub-frame duration, and transmits the second data (65) using the first link (36) to the satellite (22) during the second sub-frame (152).
摘要:
In a communications system, an earth-based subscriber unit (40, FIG. 1) receives at least one communications beam (50, 60, FIG. 1) transmitted from one or more moving satellite communications nodes (10, 20). The earthbased subscriber unit evaluates which communications beam should be selected based on the power received (FIG. 2, 210), Doppler frequency shift (270), link quality, (290), interference level (300), and satellite and network specific parameters (310). By considering these factors, the earth-based subscriber unit selects the communications beam (50, 60) that will provide the optimum service and reduce the likelihood that an inter-satellite hand over of the call will be required while the call is in progress.
摘要:
A communication system provides multiple wireless services, each potentially having a different information bit rate. A transmitter (400, FIG. 4) encodes (504, FIG. 5) relatively low rate data (430, FIG. 4) using code division multiple access (CDMA). The resulting spread data stream(s) (436, FIG. 4) are multiplexed and modulated (506, 508, FIG. 5) along with relatively high information rate, non-encoded data streams (440, FIG. 4) using a time division multiple access/frequency division multiple access (TDMA/FDMA) protocol. In other embodiments, the methods and apparatus of the present invention can be used in a CDMA only system, or in a system using a time division multiplexing/FDMA and time division multiplexing/CDMA. In one embodiment, the spread data streams are transmitted in timeslots (211-214, FIG. 2) and frequencies (201-204, FIG. 2) that are interspersed between timeslots and frequencies used for the high rate data. A receiver (600, FIG. 6) performs complementary demodulation (704, FIG. 7), demultiplexing (706, FIG. 7), and decoding (710, FIG. 7).
摘要:
The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol's transmitted value.
摘要:
The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol's transmitted value.
摘要:
A time division multiple access (TDMA) communications system (20) includes a first TDMA platform (22) for transmitting a call (32) over a circuit switched communication link (36) to a second TDMA platform (24). The call (32) exhibits a first signal type (84) and second signal type (86). A controller (42) establishes a capacity allocation (200) responsive to the first signal type (84) for the communication link (36). When the call (32) exhibits the first signal type (84), the first TDMA platform (22) transmits first packets (111) of the call (32) in a first packet format (113) using the capacity allocation (200), and when the call (32) exhibits the second signal type (86), the first TDMA platform (22) transmits second packets (140) of the call (32) in a second packet format (139) using the capacity allocation (200).
摘要:
A method and apparatus for soft decision propagation trades off system bandwidth in return for link margin. When signal quality on an uplink is low, a satellite (20) sends soft decision data, rather than hard decision data, to a gateway (40). When path diversity exists on the uplinks, and multiple satellites (20) receive the uplink, multiple versions of soft decision data are sent to the gateway (40). The gateway combines the soft decision data resulting from multiple uplink paths, thereby increasing the effective uplink signal to noise ratio.
摘要:
In a code division multiplexed system, a subscriber unit (260, FIG. 1), which includes a pseudonoise code generator (70), is synchronized with the pseudonoise code generator (220) of a communications node (200). Synchronization between the pseudonoise code generators (70, 220) is achieved through measuring the time delay of a signal transmitted from the communications node (200) to the subscriber unit (260) and advancing the code generator of the subscriber unit in accordance with the time delay. This permits transmissions from the subscriber unit (260) to be received synchronously at the satellite. The synchronization is maintained through the periodic transmission from the communications node (200) to the subscriber unit (260) of a message which commands the subscriber unit (260) to adjust the timing of its pseudonoise code generator. The resulting synchronous code division multiplexed system offers increased capacity over conventional systems.
摘要:
A communication system (100) includes an aircraft (120) that acts as a repeater between ground equipment (101) and communication units (128) on the ground. The ground equipment (101) includes multiple base transceiver stations (104, 106, 108) that provide traffic channels, control channels, and access channels. The channels are all in a single beam (124) projected from aircraft (120). Relative loading on access channels is influenced by access class lists (200, FIG. 2) assigned to control channels. Access classes can be transferred from one list to another, or they can be removed from a list. Relative loading of traffic channels on the base transceiver stations is influenced by assigning different time offsets to base transceiver station so that calls can be transferred from one base transceiver station to another.