摘要:
A method and associated circuitry for initiating communication between a network station and a user terminal of a radiotelephonic communication system, such as a satellite-cellular communication system. When communication is to be initiated, a paging signal is transmitted by a network station to the user terminal. When the user terminal detects the paging signal, an acknowledgment signal is generated by the user terminal and encoded to increase the margin of the acknowledgment signal. Upon reception, the acknowledgment signal is correlated using a multiplicity of correlators. An increased margin acknowledgment signal acknowledging reception of the paging signal is transmitted to facilitate communication of the acknowledgment signal back to the network station.
摘要:
A system and method for permitting variable information rates and improved error performance using orthogonal or near-orthogonal codes is disclosed. This is achieved by simultaneously transmitting two or more Walsh code words from a given orthogonal code set and/or by transmitting multiple shorter orthogonal codewords sequentially such that their combined length equals the original codeword. It should be emphasized that the present invention can be used with any orthogonal or near-orthogonal code set.
摘要:
A communication system provides efficient satellite communication in rural, remote, or sparsely populated areas, or in areas lacking a conventional telephone infrastructure, or in special purpose uses such as airport coverage. Subscribers in such areas communicate with the satellite via a simple, highly modular entry node located in a local area to be served. Subscriber units provide subscribers with access to the system. The subscriber units are connected to the entry node via local access loops provided by point-to-point wireless links between the subscriber units and the entry node. The entry node internally switches local traffic among subscribers and connects traffic to outside circuits, via wireless links with the satellite, as appropriate. The outside circuits are provided by the cooperative working of the satellite, an entry-node controller, and an earth station. The wireless links between the satellite and the entry node and the local access loops may operate at the same or different frequencies. If they operate at different frequencies, a frequency translator in the entry node controller matches the different frequencies. A subscriber unit may be used to provide the subscribers with access to the system such that speech compression and decompression takes place in the subscriber unit itself to avoid the effects of tandem coder/decoders.
摘要:
A method for encoding and decoding the digital information sequence uses a combination of two block codes to simultaneously correct and detect errors. The information sequence is encoded by a first stage of the encoder to produce an information code word including an information vector and a primary redundancy vector. The primary redundancy vector is encoded in a second stage of the encoder to obtain a redundancy code word. The information code word and redundancy code word are interleaved and transmitted to the receiver. At the receiver, the information code word and redundancy code word are decoded in a first stage of the decoder to obtain a first estimate of the information code word. The first estimate of the information code word is decoded in the second stage of the decoder to produce a second estimate of the information code word. The distance between the first and second estimates of the information code word is evaluated. If the distance is more than one, the received code word is erased. In another embodiment, the information sequence is repeated at the receiver. Each repetition includes a parity check resulting from the same code or from different codes. The received information vectors are selectively combined and then individually decoded using the individual parity vectors to generate multiple estimates of the information sequence. The estimates are then combined using hard or soft combining techniques.
摘要:
A method and associated circuitry for initiating communication between a network station and a user terminal of a radiotelephonic communication system, such as a satellite-cellular communication system. When communication is to be initiated, a paging signal is transmitted by a network station to the user terminal. When the user terminal detects the paging signal, an acknowledgment signal is generated by the user terminal and encoded to increase the margin of the acknowledgment signal. An increased-margin acknowledgment signal acknowledging reception of the paging signal is transmitted to facilitate communication of the acknowledgment signal back to the network station.
摘要:
Diversity and inter-frequency mobile-assisted handoff (MAHO) are achieved under continuous reception cellular access methods by using strategic timing and switching optimizations. Strategic timing is achieved by avoiding the non-reception of power control bits. For example, the mobile terminal can make measurements for diversity in the last eight bits of a sub-frame of an IS-95 downlink transmission. Switching is optimized, for example, by storing rake taps for a first antenna prior to switching to a second antenna so that the rake tap positions can be restored upon returning to the first antenna. With these and other disclosed measurement techniques, the benefits of diversity and inter-frequency MAHO can be achieved in continuous reception cellular systems.
摘要:
A fading compensation apparatus and method are provided in which blocks of the analog AM signal (e.g., voice) are time-compressed at a transmitter. Gaps in the time-compressed signal are filled with pilot symbols (or similar complex waveforms) having known characteristics, such as predetermined amplitudes. The time-compressed analog AM signal (e.g., SSB or VSB) is transmitted over the fading channel. At an analog AM receiver, an estimate of the fading that occurred in the transmission channel is made by observing the amplitude of the received pilot symbols at discrete points in time, and interpolating to determine the amount of fading that occurred across the total transmitted signal. A fading compensator compares the received faded time-compressed signal with the interpolation results, and adjusts the amplitude and phase of the received signal accordingly to compensate for the fading that occurred in the transmission channel. The compensated analog AM signal is time expanded and output to a user.
摘要:
A method and system for increasing the signal margin of a radiocommunication link to provide a short message service which is reliable, even under non-ideal conditions. According to the method, an increase in transmission power is used in combination with bit repetition to increase signal margin without complications in the mobile unit design, significant delay, or co-channel interference. Where a more significant increase in signal margin is desired, when a longer message is required, or for voice messages, the message may be stored and the mobile unit alerted of the message.
摘要:
The disclosure presents a number of reduced complexity architectures for despreading direct sequence spread spectrum communications signals. In a first despreading architecture for a sequence removal unit, received chip-spaced complex samples are negated in accordance with the processed phase of a complex spreading sequence. Furthermore, the in-phase and quadrature phase sample values are switched for each other in accordance with the processed phase. In a second despreading architecture, in a sequence removal unit, received chip-spaced complex samples are processed in the logarithmic domain, with the phase of the complex spreading sequence added to the detected phase, and the resulting complex signal then converted back to Cartesian coordinates. In a third despreading architecture for a correlator, sequence removal and correlation are performed in the logarithmic domain with the amplitudes and phases for the resulting complex signal arithmetically averaged and then converted back to Cartesian coordinates. architecture also for a correlator, sequence removal and correlation are performed in the logarithmic domain using circular averaging. In a fifth despreading architecture also for a correlator, wherein multiple component sequences are combined together to form an overall sequence, and wherein one of the multiple component sequences is shared by all channels, a common sequence removal is provided for removal of the shared sequence from all channels. The resulting signals are then sent to a plurality of individual correlators for removal of channel specific sequences.
摘要:
A method and system for increasing the signal margin of a radiocommunication link to provide a short message service which is reliable, even under non-ideal conditions. According to the method, short alphanumeric messages can be transmitted over the broadcast control channel of a digital radiocommunication link, or another communication channel consisting of one or more slots from successive frames in a TDMA communication link. An increase in transmission power is used in combination with repetition to increase effective signal margin without complications in the mobile unit design, significant delay, or co-channel interference. Where a more significant increase in signal margin is desired, when a longer message is required, or for voice messages, the message may be stored and the mobile unit alerted of the message.