Joint equalization, soft-demapping and phase error correction in wireless system with receive diversity
First Claim
Patent Images
1. A method comprising:
- receiving wireless signals via multiple antennas;
demodulating the wireless signals to produce observations of a transmitted symbol;
weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna;
combining the weighted observations to form a combined observation;
generating one or more soft decision bits indicative of the transmitted symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted symbol; and
generating one or more soft decision bits indicative of the transmitted symbol for an imaginary component of the combined observation according to the soft demapping rules based on a subset of the transmitted symbol constellation.
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Abstract
A wireless communication technique enables equalization, soft demapping and phase error estimation functions to be performed jointly based on multiple observations of a transmitted symbol in wireless communication systems employing receive diversity. Multiple observations of a symbol are obtained from multiple antenna paths in a wireless receiver. Equalization, soft demapping and phase error estimation functions can be integrated within shared hardware, rather than distributed among separate hardware blocks, promoting reduced size, complexity and cost in a wireless receiver.
53 Citations
128 Claims
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1. A method comprising:
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receiving wireless signals via multiple antennas; demodulating the wireless signals to produce observations of a transmitted symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted symbol; and generating one or more soft decision bits indicative of the transmitted symbol for an imaginary component of the combined observation according to the soft demapping rules based on a subset of the transmitted symbol constellation. - View Dependent Claims (2, 3, 4, 5, 6, 8, 111, 121)
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7. A method comprising:
receiving wireless signals via multiple antennas; demodulating the wireless signals to produce observations of a transmitted symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted symbol for the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation; and estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone.
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9. A method comprising:
receiving wireless signals via multiple antennas; demodulating the wireless signals to produce observations of a transmitted symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted symbol for the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation; and estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone, wherein generating the one or more soft decision bits and estimating the combined phase error are performed jointly within shared hardware.
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10. A method comprising:
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receiving orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; demodulating and performing fast Fourier transform (FFT) functions on the wireless signals to produce observations of a transmitted quadrature amplitude modulated (QAM) symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and generating one or more soft decision bits indicative of the transmitted QAM symbol for an imaginary component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation. - View Dependent Claims (11, 12, 13, 14, 15, 28, 112, 122)
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16. A method comprising:
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receiving orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; demodulating and performing fast Fourier transform (FFT) functions on the wireless signals to produce observations of a transmitted Quadrature amplitude modulated (QAM) symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone.
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17. A method comprising:
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receiving orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; demodulating and performing fast Fourier transform (FFT) functions on the wireless signals to produce observations of a transmitted Quadrature amplitude modulated (QAM) symbol; weighting each of the observations with a complex-conjugate of a channel response for the corresponding antenna; combining the weighted observations to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone; estimating the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error; and estimating the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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29. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via a first antenna; receiving the orthogonal frequency division multiplexing (OFDM) wireless signal via a second antenna; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the first antenna to produce a first observation of a transmitted quadrature amplitude modulated (QAM) symbol; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the second antenna to produce a second observation of the transmitted quadrature amplitude modulated (QAM) symbol; weighting the first observation with a complex-conjugate of a channel response for the first antenna; weighting the second observation with a complex-conjugate of a channel response for the second antenna; combining the weighted first observation and the weighted second observation to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and generating one or more soft decision bits indicative of the transmitted QAM symbol for an imaginary component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation. - View Dependent Claims (30, 31, 32, 33, 34, 46, 113, 123)
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35. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via a first antenna; receiving the orthogonal frequency division multiplexing (OFDM) wireless signal via a second antenna; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the first antenna to produce a first observation of a transmitted Quadrature amplitude modulated (QAM) symbol; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the second antenna to produce a second observation of the transmitted quadrature amplitude modulated (QAM) symbol; weighting the first observation with a complex-conjugate of a channel response for the first antenna; weighting the second observation with a complex-conjugate of a channel response for the second antenna; combining the weighted first observation and the weighted second observation to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone; estimating the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error; and estimating the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers.
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36. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via a first antenna; receiving the orthogonal frequency division multiplexing (OFDM) wireless signal via a second antenna; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the first antenna to produce a first observation of a transmitted Quadrature amplitude modulated (QAM) symbol; demodulating and performing fast Fourier transform (FFT) functions on the wireless signal received by the second antenna to produce a second observation of the transmitted Quadrature amplitude modulated (QAM) symbol; weighting the first observation with a complex-conjugate of a channel response for the first antenna; weighting the second observation with a complex-conjugate of a channel response for the second antenna; combining the weighted first observation and the weighted second observation to form a combined observation; generating one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; estimating a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone; estimating the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error; estimating the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers; adjusting an FFT sampling window for each of the wireless signals based on the sampling phase error; and applying a frequency domain correction to subsequent observations based on the carrier phase error and sampling phase error. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45)
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47. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via an antenna; demodulating and performing a fast Fourier transform (FFT) function on the wireless signal to produce an observation of a transmitted quadrature amplitude modulated (QAM) symbol; weighting the observation with a complex-conjugate of a channel response for the antenna; generating one or more soft decision bits indicative of the transmitted symbol for a real component of the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation; and generating one or more soft decision bits indicative of the transmitted symbol for an imaginary component of the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation. - View Dependent Claims (48, 49, 50, 51, 52, 58, 114, 124)
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53. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via an antenna; demodulating and performing a fast Fourier transform (FFT) function on the wireless signal to produce an observation of a transmitted Quadrature amplitude modulated (QAM) symbol; weighting the observation with a complex-conjugate of a channel response for the antenna; generating one or more soft decision bits indicative of the transmitted symbol for the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation; estimating a combined phase error including carrier phase error and sampling phase error for the weighted observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone; estimating the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error; and estimating the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers.
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54. A method comprising:
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receiving an orthogonal frequency division multiplexing (OFDM) wireless signal via an antenna; demodulating and performing a fast Fourier transform (FFT) function on the wireless signal to produce an observation of a transmitted quadrature amplitude modulated (QAM) symbol; weighting the observation with a complex-conjugate of a channel response for the antenna; generating one or more soft decision bits indicative of the transmitted symbol for the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation; estimating a combined phase error including carrier phase error and sampling phase error for the weighted observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone; estimating the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error; estimating the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers; adjusting an FFT sampling window for the wireless signal based on the sampling phase error; and applying a frequency domain correction to subsequent observations based on the carrier phase error and sampling phase error. - View Dependent Claims (55, 56, 57)
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59. A wireless receiver comprising:
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multiple antennas that receive wireless signals; a demodulator that demodulates the wireless signals to produce observations of a transmitted symbol; an equalizer that weights each of the observations with a complex conjugate of an estimated channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, generates one or more soft decision bits indicative of the transmitted symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation, and generates one or more soft decision bits indicative of the transmitted symbol for an imaginary component of the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation. - View Dependent Claims (60, 61, 62, 63, 64, 67, 115, 125)
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65. A wireless receiver comprising:
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multiple antennas that receive wireless signals; a demodulator that demodulates the wireless signals to produce observations of a transmitted symbol; an equalizer that weights each of the observations with a complex conjugate of an estimated channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, and generates one or more soft decision bits indicative of the transmitted symbol for the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation; and a phase error estimator that estimates a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone.
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66. A wireless receiver comprising:
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multiple antennas that receive wireless signals; a demodulator that demodulates the wireless signals to produce observations of a transmitted symbol; an equalizer that weights each of the observations with a complex conjugate of an estimated channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, and generates one or more soft decision bits indicative of the transmitted symbol for the combined observation according to soft demapping rules based on a subset of the transmitted symbol constellation; and a phase error estimator that estimates a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone, wherein the soft demapper unit and the phase error estimator are provided jointly within shared hardware.
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68. A receiver comprising:
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multiple antennas that receive orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; a fast Fourier transform (FFT) unit that produce observations of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signals; an equalizer that weights each of the observations with a complex-conjugate of a channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for an imaginary component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation. - View Dependent Claims (69, 70, 71, 72, 73, 86, 116, 126)
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74. A receiver comprising:
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multiple antennas that receive orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; a fast Fourier transform (FFT) unit that produce observations of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signals; an equalizer that weights each of the observations with a complex-conjugate of a channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and a phase error estimator that estimates a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone.
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75. A receiver comprising:
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multiple antennas that receive orthogonal frequency division multiplexing (OFDM) wireless signals via multiple antennas; a fast Fourier transform (FFT) unit that produce observations of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signals; an equalizer that weights each of the observations with a complex-conjugate of a channel response for the corresponding antenna; and a soft demapper unit that combines the weighted observations to form a combined observation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and a phase error estimator that estimates a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone, wherein the phase error estimator estimates the carrier phase error by summing the estimated combined phase errors that correspond to complementary subcarriers in the wireless signals to remove the sampling phase error, and estimates the sampling phase error by subtracting the estimated combined phase error that corresponds to one of the subcarriers from the estimated combined phase error that corresponds to another of the subcarriers. - View Dependent Claims (76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 118)
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87. A receiver comprising:
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a first antenna that receives an orthogonal frequency division multiplexing (OFDM) wireless signal; a second antenna that receives the orthogonal frequency division multiplexing (OFDM) wireless signal; a first fast Fourier transform (FFT) unit that produces a first observation of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signal received by the first antenna; a second fast Fourier transform (FFT) unit that produces a second observation of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signal received by the second antenna; an equalizer that weights the first observation with a complex-conjugate of a channel response for the first antenna, and weights the second observation with a complex-conjugate of a channel response for the second antenna; a soft demapper unit that combines the weighted first observation and the weighted second observation to form a combined observation, generates one or more soft decision bits indicative of the transmitted QAM symbol for a real component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for an imaginary component of the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation. - View Dependent Claims (88, 89, 90, 91, 92, 117, 127)
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93. A receiver comprising:
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a first antenna that receives an orthogonal frequency division multiplexing (OFDM) wireless signal; a second antenna that receives the orthogonal frequency division multiplexing (OFDM) wireless signal; a first fast Fourier transform (FFT) unit that produces a first observation of a transmitted Quadrature amplitude modulated (QAM) symbol from the wireless signal received by the first antenna; a second fast Fourier transform (FFT) unit that produces a second observation of a transmitted Quadrature amplitude modulated (QAM) symbol from the wireless signal received by the second antenna; an equalizer that weights the first observation with a complex-conjugate of a channel response for the first antenna, and weights the second observation with a complex-conjugate of a channel response for the second antenna; a soft demapper unit that combines the weighted first observation and the weighted second observation to form a combined observation, and generates one or more soft decision bits indicative of the transmitted QAM symbol for the combined observation according to soft demapping rules based on a subset of the transmitted QAM symbol constellation; and a phase error estimator that estimates a combined phase error including carrier phase error and sampling phase error for the combined observation using either the transmitted symbol estimated based on the soft decision bits or a predetermined symbol transmitted via a pilot tone.
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94. A receiver comprising:
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an antenna that receives an orthogonal frequency division multiplexing (OFDM) wireless signal; a fast Fourier transform (FFT) function unit that produces an observation of a transmitted quadrature amplitude modulated (QAM) symbol from the wireless signal; an equalizer that weights the observation with a complex-conjugate of a channel response for the antenna; and a soft demapper unit that generates one or more soft decision bits indicative of the transmitted symbol for a real component of the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation, and generates one or more soft decision bits indicative of the transmitted symbol for an imaginary component of the weighted observation according to soft demapping rules based on a subset of the transmitted symbol constellation. - View Dependent Claims (95, 96, 97, 98, 99, 100, 128)
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- 101. A method comprising applying a soft decision function to generate soft decision bits for a real component of a combined transmitted symbol observation produced from wireless signals received via multiple receive paths, and generate soft decision bits for an imaginary component of a combined transmitted symbol observation produced from wireless signals received via multiple receive paths, wherein the soft decision function defines soft demapping rules based on a subset of the transmitted symbol constellation.
- 106. A receiver comprising a soft demapper unit that applies a soft decision function to generate soft decision bits for a real component of a combined QAM symbol produced from wireless signals received via multiple receive paths, and generate soft decision bits for an imaginary component of a combined QAM symbol produced from wireless signals received via multiple receive paths, wherein the soft decision function defines soft demapping rules based on a subset of the transmitted symbol constellation.
Specification