Communications system handoff operation combining turbo coding and soft handoff techniques
First Claim
1. A mobile communication system, comprising:
- a source of digital data, for communication to or from a predetermined one of a plurality of mobile stations;
a first constituent encoder, coupled to the source, for encoding the digital data into a first code sequence;
an interleaver, coupled to the source, for interleaving the digital data;
a second constituent encoder, coupled to the interleaver, for encoding the interleaved digital data into a second code sequence;
a first code puncturer, coupled to the first and second constituent encoders, for selectively combining data from the first code sequence and data from the second code sequence according to a first puncturing pattern, to form a first punctured code sequence;
a second code puncturer, coupled to the first and second constituent encoders, for selectively combining data from the second code sequence and data from the first code sequence according to a second puncturing pattern, to form a second punctured code sequence;
first and second transmitters for transmission of information on first and second logical channels assigned to the predetermined mobile station; and
wherein at least during a handoff operation, the first transmitter broadcasts the first channel carrying a first representation of the digital data together with the first punctured code sequence, and concurrently the second transmitter broadcasts the second channel carrying a second representation of the digital data together with the second punctured code sequence.
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Accused Products
Abstract
Communication systems, including, for example, cell-based mobile communication systems, multiple satellite communication systems, or multibeam satellite systems, require reliable handoff methods between cell-to-cell, beam-to-beam, or satellite-to-satellite respectively. Recent measurement of a CDMA cellular system indicates that the system is in handoff about 30% to 50% of an average call period. Therefore, system reliability during handoff is one of the major system performance parameters and eventually becomes a factor in the overall system capacity. The present invention advantageously relates to novel and improved techniques for handoff in cellular communications, multibeam and multisatellite systems. The present invention combines the soft handoff mechanism with a code diversity combining technique (i.e., combining signals from multiple sources), a packet combining technique (i.e., combining multiple signals), and an iterative decoding algorithm (e.g., Turbo Coding).
232 Citations
28 Claims
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1. A mobile communication system, comprising:
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a source of digital data, for communication to or from a predetermined one of a plurality of mobile stations; a first constituent encoder, coupled to the source, for encoding the digital data into a first code sequence; an interleaver, coupled to the source, for interleaving the digital data; a second constituent encoder, coupled to the interleaver, for encoding the interleaved digital data into a second code sequence; a first code puncturer, coupled to the first and second constituent encoders, for selectively combining data from the first code sequence and data from the second code sequence according to a first puncturing pattern, to form a first punctured code sequence; a second code puncturer, coupled to the first and second constituent encoders, for selectively combining data from the second code sequence and data from the first code sequence according to a second puncturing pattern, to form a second punctured code sequence; first and second transmitters for transmission of information on first and second logical channels assigned to the predetermined mobile station; and wherein at least during a handoff operation, the first transmitter broadcasts the first channel carrying a first representation of the digital data together with the first punctured code sequence, and concurrently the second transmitter broadcasts the second channel carrying a second representation of the digital data together with the second punctured code sequence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A receiver system for operation in a mobile wireless communication system, the receiver system comprising:
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receiver circuitry for processing modulated signals associated with a mobile station received from two or more transmitters during a handoff operation, to obtain first and second data streams; demultiplexer circuitry, coupled to an output of the receiver circuitry, for processing the first data stream received during handoff to recover digital data corresponding to a first representation of a digital information sequence and a first punctured sequence and to recover digital data corresponding to a second representation of the digital information sequence and a second punctured sequence; a code combiner, coupled to the demultiplexer circuitry, for processing the sequences, to recover a first constituent encoded sequence corresponding to the first representation of the digital information sequence and a second constituent encoded sequence corresponding to the second representation of the digital information sequence; and a decoder coupled to the code combiner for processing the recovered digital data corresponding to the first and second representations of the digital information sequence and the first and second constituent encoded sequences, to recover an accurate representation of the digital information sequence during the handoff operation. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A mobile receiver for operation with a wireless communication system having a plurality of transmitters serving cells or segments of a geographic region, the mobile receiver comprising:
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receiver circuitry for processing received modulated signals intended for the mobile receiver from one or more of the transmitters, wherein during a handoff from one transmitter to another transmitter the receiver circuitry is capable of processing received modulated signals intended for the mobile receiver from at least two of the transmitters, to obtain first and second forward data streams; a first demultiplexer, coupled to an output of the receiver circuitry, for processing the first forward data stream received during handoff to recover digital data corresponding to a representation of a digital information sequence intended for the mobile receiver and a first coded sequence; a second demultiplexer, coupled to an output of the receiver circuitry, for processing the second forward data stream received during handoff to recover digital data corresponding to another representation of the digital information sequence intended for the mobile receiver and a second coded sequence; a code combiner, coupled to the first and second demultiplexers, for processing the first and second coded sequences during handoff, to recover a first constituent encoded sequence corresponding to the first representation of the digital information sequence intended for the mobile receiver and a second constituent encoded sequence corresponding to the second representation of the digital information sequence intended for the mobile receiver; and a decoder, coupled to the code combiner, for recovering an accurate representation of the digital information sequence intended for the mobile receiver from the recovered digital data corresponding to at least one of the representations of the digital information sequence intended for the mobile receiver and the first and constituent coded sequences. - View Dependent Claims (20, 21, 22, 23)
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24. A method of communicating digital data in a mobile wireless communication network, comprising:
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detecting a need for handoff of service for a predetermined mobile station; and executing a handoff operation, said handoff operation comprising; (a) constituent encoding the digital data into a first code sequence, (b) interleaving the digital data, (c) constituent encoding the interleaved digital data into a second code sequence, (d) selectively combining data from the first code sequence and data from the second code sequence according to a first puncturing pattern to form a first punctured code sequence, (e) selectively combining data from the first code sequence and data from the second code sequence according to a second puncturing pattern to form a second punctured code sequence, (f) transmitting on a first path, over a first logical channel, a first representation of the digital data and the first punctured code sequence, (g) transmitting on a second path, over a second logical channel, a second representation of the digital data and the second punctured code sequence, (h) in a receiver, combining the first punctured code sequence with the second punctured code sequence to recover at least portions of the first and second code sequences, and (i) recovering an accurate representation of the digital data from received portions of one or more of the representations of the digital data, at least a recovered portion of the first encoded sequence, and at least a recovered portion of the second encoded sequence. - View Dependent Claims (25, 26, 27, 28)
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Specification