Methods and apparatus for performing rate determination with a variable rate viterbi decoder

Claim 3

A method as set forth in claim 1, wherein the plurality of threshold values are fixed values.

Claim 4

A method as set forth in claim 1, wherein the plurality of threshold values are varied as a function of at least one reception-related criterion.

Claim 5

A method as set forth in claim 1, wherein the step of decoding includes a step of summing and scaling received data bits as a function of data rate.

Claim 6

A method as set forth in claim 4, wherein the step of summing includes a step of coherently combining only data bits received at the transmitted data rate.

Claim 9

A method as set forth in claim 6, wherein the step of decoding includes a step of determining branch metrics of received symbols, and wherein the step of determining branch metrics includes an initial step of scaling received data in accordance with individual ones of the n data rates.

Claim 10

A method as set forth in claim 6, wherein the step of determining a total cumulative metric includes the steps of: processing the branch metrics to determine survivor metrics; normalizing individual ones of the survivor metrics to form normalized survivor metrics; accumulating the normalized survivor metrics to form cumulative metrics; accumulating normalization values used to normalize each of the normalized survivor metrics; at the end of decoding, outputting a cumulative metric that corresponds to a most likely path through the trellis; and combining an accumulated normalization value with the outputted cumulative metric to form the total cumulative metric.

Claim 11

A method as set forth in claim 6, wherein the step of decoding includes a step of determining branch metrics of received symbols, and wherein the step of determining branch metrics includes an initial step of linearly scaling received data in accordance with individual ones of the n data rates.

Claim 12

A method as set forth in claim 6, wherein the step of decoding includes a step of determining branch metrics of received symbols, and wherein the step of determining branch metrics includes an initial step of non-linearly scaling received data in accordance with individual ones of the n data rates.

Claim 13

A method as set forth in claim 6, wherein the step of comparing uses predetermined, fixed cumulative metric threshold values.

Claim 14

A method as set forth in claim 6, wherein the step of comparing includes a step varying the plurality of cumulative metric threshold values.

Claim 15

A method as set forth in claim 6, wherein the data is received during a given frame of data at one of a highest rate and at least one lower rate, and wherein the step of comparing includes the steps of: performing an initial step of determining a value of an average cumulative metric for data received at the highest rate; calculating from the determined value a cumulative metric threshold value for each of the highest rate and the at least one lower rate; and for each subsequent frame that is determined to be received at the highest rate, revising the value of the average cumulative metric; and calculating from the revised value a revised cumulative metric threshold value for each of the highest rate and the at least one lower rate.

Claim 16

Apparatus for determining a data rate of a received encoded signal, comprising: a decoder for decoding a signal received from a communications channel for extracting data therefrom, the data being received at one of a plurality of rates, said decoder comprising an accumulator for accumulating a normalization value of Cumulative Metrics; means for combining an accumulated normalization value with a Cumulative Metric to reconstruct a Total Cumulative Metric for at least a Most Likely decoder path; a comparator for comparing the Total Cumulative Metric to at least one threshold value corresponding to at least one of said plurality of rates; and means, responsive to said comparator, for identifying a rate at which the data was received from the communications channel.

Claim 17

Apparatus for determining a data rate of a received encoded signal, comprising: a decoder for decoding a signal received from a communications channel for extracting data therefrom, the data being received at one of a plurality of rates, said decoder comprising an accumulator for accumulating a normalization value of Cumulative Metrics; means for combining an accumulated normalization value with a Cumulative Metric to reconstruct a Total Cumulative Metric for at least a Most Likely decoder path; a comparator for comparing the Total Cumulative Metric to at least one threshold value corresponding to at least one of said plurality of rates; and means, responsive to said comparator, for identifying a rate at which the data was received from the communications channel.

Claim 18

Apparatus as set forth in claim 14, wherein the plurality of threshold values are fixed values.

Claim 19

Apparatus as set forth in claim 14, wherein the plurality of threshold values are varied as a function of at least one reception-related criterion.

Claim 20

Apparatus as set forth in claim 14, wherein said decoder further comprises means for summing and scaling received data bits as a function of data rate.

Claim 21

Apparatus as set forth in claim 17, wherein said means for summing and scaling coherently combines only data bits received at the transmitted data rate.

Claim 22

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis, the total cumulative metric being determined from a summation of a cumulative metric and an accumulated normalization value for the cumulative metric; means for comparing the value of the total cumulative metric to a plurality of predetermined and fixed cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison.

Claim 23

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis, the total cumulative metric being determined from a summation of a cumulative metric and an accumulated normalization value for the cumulative metric; means for comparing the value of the total cumulative metric to a plurality of predetermined and fixed cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison.

Claim 24

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein said means for decoding comprises means for determining branch metrics of received symbols, and means for scaling received data in accordance with individual ones of the n data rates prior to an application of the received data to the means for determining branch metrics, and wherein said scaling means is comprised of means for non-linearly scaling received data in accordance with individual ones of the n data rates.

Claim 25

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein said means for decoding comprises means for determining branch metrics of received symbols, and means for scaling received data in accordance with individual ones of the n data rates prior to an application of the received data to the means for determining branch metrics, and wherein said scaling means is comprised of means for non-linearly scaling received data in accordance with individual ones of the n data rates.

Claim 26

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein said means for determining a total cumulative metric is comprised of: means for processing the branch metrics to determine survivor metrics; means for normalizing individual ones of the survivor metrics to form normalized metrics; means for accumulating the normalized metrics to form cumulative metrics; means for accumulating normalization values used to normalize each of the normalized metrics; means, responsive to a termination of decoding, for outputting a cumulative metric that corresponds to a most likely path through the trellis; and means for adding an accumulated normalization value to the outputted cumulative metric to form the total cumulative metric.

Claim 27

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein said means for determining a total cumulative metric is comprised of: means for processing the branch metrics to determine survivor metrics; means for normalizing individual ones of the survivor metrics to form normalized metrics; means for accumulating the normalized metrics to form cumulative metrics; means for accumulating normalization values used to normalize each of the normalized metrics; means, responsive to a termination of decoding, for outputting a cumulative metric that corresponds to a most likely path through the trellis; and means for adding an accumulated normalization value to the outputted cumulative metric to form the total cumulative metric.

Claim 28

Apparatus as set forth in claim 21, wherein said means for decoding comprises means for determining branch metrics of received symbols, and means for scaling received data in accordance with individual ones of the n data rates prior to an application of the received data to the means for determining branch metrics.

Claim 29

Apparatus as set forth in claim 22, wherein said scaling means is comprised of means for linearly scaling received data in accordance with individual ones of the n data rates.

Claim 30

Apparatus as set forth in claim 21, wherein said comparing means uses predetermined, fixed cumulative metric threshold values.

Claim 31

Apparatus as set forth in claim 19, wherein said comparing means is comprised of means for varying the plurality of cumulative metric threshold values.

Claim 32

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein the data is received during a given frame of data at one of a highest rate and at least one lower rate, and wherein said comparing means is comprised of: means for determining a value of an average cumulative metric for data received at the highest rate; means for calculating from the determined value a cumulative metric threshold value for each of the highest rate and the at least one lower rate; means, responsive to each subsequent frame that is determined to be received at the highest rate, for revising the value of the average cumulative metric for data received at the highest rate; and means for calculating from the revised value a revised cumulative metric threshold value for each of the highest rate and the at least one lower rate.

Claim 33

Apparatus for determining a data rate of a received encoded signal, comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis; means for comparing the value of the total cumulative metric to a plurality of cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison, wherein the data is received during a given frame of data at one of a highest rate and at least one lower rate, and wherein said comparing means is comprised of: means for determining a value of an average cumulative metric for data received at the highest rate; means for calculating from the determined value a cumulative metric threshold value for each of the highest rate and the at least one lower rate; means, responsive to each subsequent frame that is determined to be received at the highest rate, for revising the value of the average cumulative metric for data received at the highest rate; and means for calculating from the revised value a revised cumulative metric threshold value for each of the highest rate and the at least one lower rate.

Claim 34

A user terminal for receiving an RF signal that conveys a spread spectrum, code division, multiple access user communication, the user communication being transmitted in frames of data bits, individual ones of the frames being transmitted with a data rate selected from a set of n data rates that includes a highest rate and at least one lower rate, said user terminal comprising means for de-spreading a received user communication to provide a received signal and further comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis, said decoding means comprising means for determining branch metrics of received data, and means for at least one linearly scaling and non-linearly scaling received data in accordance with individual ones of the n data rates prior to an application of the received data to the means for determining branch metrics, said decoding means further comprising means for processing the branch metrics to determine survivor metrics; means for normalizing individual ones of the survivor metrics to form normalized metrics; means for accumulating the normalized metrics to form cumulative metrics; means for accumulating normalization values used to normalize each of the normalized metrics; means, responsive to a termination of decoding, for outputting a cumulative metric that corresponds to a most likely path through the trellis; and means for adding an accumulate normalization value to the outputted cumulative metric to form the total cumulative metric; means for comparing the value of the total cumulative metric to a plurality of adaptively determined cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison.

Claim 35

A user terminal for receiving an RF signal that conveys a spread spectrum, code division, multiple access user communication, the user communication being transmitted in frames of data bits, individual ones of the frames being transmitted with a data rate selected from a set of n data rates that includes a highest rate and at least one lower rate, said user terminal comprising means for de-spreading a received user communication to provide a received signal and further comprising: means for decoding the received signal and for determining, for individual ones of n data rates, a value of a total cumulative metric associated with a most likely path through a decoder trellis, said decoding means comprising means for determining branch metrics of received data, and means for at least one linearly scaling and non-linearly scaling received data in accordance with individual ones of the n data rates prior to an application of the received data to the means for determining branch metrics, said decoding means further comprising means for processing the branch metrics to determine survivor metrics; means for normalizing individual ones of the survivor metrics to form normalized metrics; means for accumulating the normalized metrics to form cumulative metrics; means for accumulating normalization values used to normalize each of the normalized metrics; means, responsive to a termination of decoding, for outputting a cumulative metric that corresponds to a most likely path through the trellis; and means for adding an accumulate normalization value to the outputted cumulative metric to form the total cumulative metric; means for comparing the value of the total cumulative metric to a plurality of adaptively determined cumulative metric threshold values individual ones of which correspond to an expected total cumulative metric for an individual one of the n data rates; and means for identifying the received data rate based on the comparison.

Claim 36

A user terminal as set forth in claim 27, wherein said comparing means is comprised of: means for determining a value of an average cumulative metric for data received at the highest rate; means for calculating from the determined value a cumulative metric threshold value for each of the highest rate and the at least one lower rate; means, responsive to each subsequent frame that is determined to be received at the highest rate, for revising the value of the average cumulative metric for data received at the highest rate; and means for calculating from the revised value a revised cumulative metric threshold value for each of the highest rate and the at least one lower rate.

Claim 39

A method as set forth in claim 29, wherein the step of decoding includes a step of summing and scaling received data bits as a function of data rate.

Claim 40

A method as set forth in claim 30, wherein the step of summing includes a step of coherently combining only data bits received at the transmitted data rate.

Claim 43

A method as set forth in claim 32, wherein the plurality of threshold values are adaptively determined as a function of at least one characteristic of the communication channel.

Claim 44

A method as set forth in claim 32, wherein there are at least four data rates R designated R1, R1/2, R1/4, and R1/8 and at least four corresponding threshold values R1 -- Tr, R1/2 -- Tr, R1/4 -- Tr, and R1/8 -- Tr, respectively, and wherein values of the corresponding threshold values are determined in accordance with the expressions: R1.sub.-- Tr=R1.sub.-- CUM.sub.ref X c1; R1/2.sub.-- Tr=R1.sub.-- Tr/c2; R1/4.sub.-- Tr=R1.sub.-- Tr/c3; and R1/8.sub.-- Tr=R1.sub.-- Tr/c4; wherein CUM ref has a value that is a function of a value of a cumulative metric of the most-likely path, and c1, c2, c3 and c4 are constants having values of approximately 0.9, 2.8, 7.8 and 22, respectively.