Using orthogonal waveforms to enable multiple transmitters to share a single CDM channel
First Claim
1. A method of enabling a plurality of transmitters to share a single code division multiplexed (CDM) channel in a CDM communications system, each transmitter having a plurality of communications channels for transmitting a plurality of data signals, comprising the steps of:
- assigning a predefined set of orthogonal channelizing codes to the plurality of transmitters in a predetermined manner;
at each transmitter;
channelizing each of the plurality of data signals using one of the orthogonal channelizing codes to produce a plurality of channelized data signals;
spreading the plurality of channelized data signals using at least one pseudonoise (PN) code to produce a plurality of spread data signals;
summing the plurality of spread data signals prior to transmission to produce a composite signal; and
frequency precorrecting the composite signal prior to transmission such that the composite signal is frequency-aligned upon reception.
1 Assignment
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Accused Products
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 Wi (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 Wi (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. The frequencies of the signals are precorrected (408, 512) to ensure frequency alignment at the receivers.
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Citations
30 Claims
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1. A method of enabling a plurality of transmitters to share a single code division multiplexed (CDM) channel in a CDM communications system, each transmitter having a plurality of communications channels for transmitting a plurality of data signals, comprising the steps of:
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assigning a predefined set of orthogonal channelizing codes to the plurality of transmitters in a predetermined manner; at each transmitter; channelizing each of the plurality of data signals using one of the orthogonal channelizing codes to produce a plurality of channelized data signals; spreading the plurality of channelized data signals using at least one pseudonoise (PN) code to produce a plurality of spread data signals; summing the plurality of spread data signals prior to transmission to produce a composite signal; and frequency precorrecting the composite signal prior to transmission such that the composite signal is frequency-aligned upon reception. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 29)
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10. A code division multiplexed (CDM) communications system having multiple transmitters, each transmitting at least one data signal sharing a single CDM channel, each transmitter comprising:
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at least one signal processing path carrying one of said data signals; multiplier means for combining each data signal with a different orthogonal channelizing code; a summer, coupled to said signal processing paths, for summing the signals produced by said signal processing paths at each transmitter prior to transmission; a time precorrector, coupled to said summer, for precorrecting the signal produced by said summer such that the PN codes of the transmitted signals of the plurality of transmitters are time aligned upon reception; and a frequency precorrector, coupled to said time precorrector, for precorrecting the signal produced by said time precorrector such that the carrier frequencies of the transmitted signals of the plurality of transmitters are time and frequency aligned upon reception. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A code division multiplexed (CDM) communications system having a plurality of transmitters, each transmitting a plurality of data signals sharing a single CDM channel, wherein each transmitter comprises:
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means for assigning a set of orthogonal channelizing codes to the plurality of transmitters in a predetermined manner; means for channelizing each of said plurality of data signals using one of said orthogonal channelizing codes to produce a plurality of channelized data signals; means for spreading said plurality of channelized signals using at least one pseudonoise (PN) spreading code to produce a plurality of spread signals; means for summing said plurality of spread signals prior to transmission to produce a composite signal; and means for frequency precorrecting said composite signal prior to transmission such that said composite signal is frequency-aligned upon reception. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 30)
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26. A method for automatically controlling frequency in a code division multiplexed (CDM) communications system having a plurality of transmitters sharing a single CDM channel, wherein each transmitter transmits at least one signal that is channelized with one of a plurality of orthogonal channelizing codes, spread with a pseudonoise (PN) spreading code, and frequency precorrected for frequency alignment upon reception, the method comprising the steps of:
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receiving a combined signal, the combined signal comprising a plurality of individual signals that are transmitted by at least one of the plurality of transmitters; despreading the combined signal using the PN spreading code; demultiplexing the combined signal into the plurality of individual signals with respect to the plurality of orthogonal channelizing codes; coherently filtering each of at least two of the plurality of individual signals; generating an error signal from each of the filtered individual signals; and
summing the error signals. - View Dependent Claims (27)
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28. Apparatus for automatic frequency control in a code division multiplexed (CDM) communications system having a plurality of transmitters sharing a single CDM channel, wherein each transmitter transmits at least one signal that is channelized with one of a plurality of orthogonal channelizing codes, spread with a pseudonoise (PN) spreading code, and frequency precorrected for frequency alignment upon reception, comprising:
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means for receiving a combined signal, the combined signal comprising a plurality of individual signals that are transmitted by at least one of the plurality of transmitters; means for despreading the combined signal using the (PN) spreading code; means for demultiplexing the composite signal into the plurality of individual signals with respect to the plurality of orthogonal channelizing codes; means for coherently filtering each of at least two of the plurality of individual signals; means for generating an error signal from each of the filtered individual signals; and means for summing the error signals.
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Specification