Apparatus and method for trellis encoding data for transmission in digital data transmission systems
First Claim
1. A Trellis encoder for encoding payload data bits with redundant bits and mapping the resulting bits into a constellation point, comprising:
- a plurality of payload data inputs for receiving a plurality of payload bits;
a convolutional encoder having a plurality of inputs coupled directly to a plurality of said payload data inputs and a first output and a second output;
a separate exclusive OR gate having an input coupled to one of said payload data inputs and having an input coupled to said first output of said convolutional encoder and having an output;
a mapper having a plurality of inputs coupled directly to a plurality of said payload data inputs, and having an input coupled to said second output of said convolutional encoder, and having an input coupled to said output of said exclusive OR gate, and having a plurality of I outputs and a plurality of Q outputs at which signals appear which are constellation points in a quadrature amplitude modulated constellation which are derived from said payload data appearing at said payload data inputs.
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Abstract
A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.
225 Citations
13 Claims
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1. A Trellis encoder for encoding payload data bits with redundant bits and mapping the resulting bits into a constellation point, comprising:
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a plurality of payload data inputs for receiving a plurality of payload bits; a convolutional encoder having a plurality of inputs coupled directly to a plurality of said payload data inputs and a first output and a second output; a separate exclusive OR gate having an input coupled to one of said payload data inputs and having an input coupled to said first output of said convolutional encoder and having an output; a mapper having a plurality of inputs coupled directly to a plurality of said payload data inputs, and having an input coupled to said second output of said convolutional encoder, and having an input coupled to said output of said exclusive OR gate, and having a plurality of I outputs and a plurality of Q outputs at which signals appear which are constellation points in a quadrature amplitude modulated constellation which are derived from said payload data appearing at said payload data inputs. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An encoder for encoding payload data bits with redundant bits and mapping the resulting bits into a constellation point so as to achieve a coding gain, comprising:
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first means for receiving a plurality of payload data bits and convolutionally encoding said payload bits to generate at least one additional bit derived mathematically from a Boolean logic combination of said payload bits, and for outputting at least some of said payload bits unchanged and at least one of said payload bits as modified by a logical operation with a bit output from an intermediate stage of a convolutional encoding process carried out in said first means, and outputting a final bit resulting from said convolutional encoding process; and second means coupled to receive one or more mode control signals and coupled to receive said final bit from said convolutional encoding process and said unchanged payload bits and said payload bit after modification by said convolutional encoding process, for mapping said bits into a constellation point of a constellation of possible data points, each point defined by a value on a real axis and a value on an imaginary axis, said mapping having at least a normal mode and a fallback mode. - View Dependent Claims (9, 10)
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11. A process for Trellis encoding a plurality of payload bits into a constellation point, comprising:
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receiving a plurality of payload bits; convolutionally encoding a combination of said payload bits into one or more additional bits by applying said payload bits to different inputs of a convolutional encoder and also applying a modified bit to an input of said convolutional encoder, said modified bit being generated by exclusive-ORing one of said payload bits with an output bit from an intermediate stage of said convolutional encoder, said convolutional encoding step resulting in output of one or more additional bits; and mapping the combination of at least some of said payload bits in an unmodified state, said modified bit and said one or more additional bits into a constellation point, wherein said process for Trellis encoding is performed upon multiple pluralities of said payload bits successively, and wherein said step of convolutional encoding comprises introducing a certain dependency between successive constellation points generated from said successive plurality of payload bits such that only certain patterns or permissible sequences of constellation points are permitted, said patterns or permissible sequences capable of being modelled in a receiver'"'"'s Viterbi decoder as a Trellis code.
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12. A process for Trellis encoding a plurality of payload bits into a constellation point, comprising:
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receiving a plurality of payload bits; convolutionally encoding a combination of said payload bits into one or more additional bits by applying said payload bits to different inputs of a convolutional encoder and also applying a modified bit to an input of said convolutional encoder, said modified bit being generated by exclusive-ORing one of said payload bits with an output bit from an intermediate stage of said convolutional encoder, said convolutional encoding step resulting in output of one or more additional bits; and mapping the combination of at least some of said payload bits in an unmodified state, said modified bit and said one or more additional bits into a constellation point, wherein said step of mapping includes the steps of receiving a control signal that indicates whether a normal mode or a fallback mode is to be implemented wherein said normal mode maps said plurality of payload bits, said modified bit and said one or more additional bits into a constellation point in a constellation of points that is larger than a constellation of possible points would be if only the original payload bits were mapped into a constellation, and said fallback mode mapping said plurality of bits in an unmodified payload state, said modified bit and said one or more additional bits into a constellation point in a constellation of points that is larger than the constellation of points that are possible in said normal mode.
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13. A process for Trellis encoding a plurality of payload bits into a constellation point, comprising:
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receiving a plurality of payload bits; convolutionally encoding a combination of said payload bits into one or more additional bits by applying said payload bits to different inputs of a convolutional encoder and also applying a modified bit to an input of said convolutional encoder, said modified bit being generated by exclusive-ORing one of said payload bits with an output bit from an intermediate stage of said convolutional encoder, said convolutional encoding step resulting in output of one or more additional bits; and mapping the combination of at least some of said payload bits in an unmodified state, said modified bit and said one or more additional bits into a constellation point, wherein the step of convolutionally encoding is characterized by parity check polynomials given in octal form as follows;
h3=04, h2=10, h1=06, h0=23, d^2_free=5.0, Nfree=1.68, and wherein the nonlinear term is given by D^2[y0(S).AND.D^(−
1)y0(D)].
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Specification