Error-correcting modem

Claim 2

In a vector-keyed modem using randomized data and forward error correction, the method of preventing error multiplication in the receiver comprising the steps of: a. performing forward error correction; and b. subsequently de-randomizing the corrected data.

Claim 3

In a vector-keyed modem using forward error correction, the method of eliminating differential coding of said vectors comprising the steps of: a. decoding received vectors with respect to a plurality of reference phases; and b. locking in the reference phase in which no substantial errors are detected during said forward error correction.

Claim 4

In a vector-keyed modem using forward error correction, the method of eliminating differential coding of said vectors comprising the steps of: a. decoding received vectors with respect to a plurality of reference phases; and b. locking in the reference phase in which no substantial errors are detected during said forward error correction.

Claim 5

- The method of preventing error multiplication in a V.22 bis modem, comprising the steps of: a. encoding a data bit train into bit groups containing data bits and error check bits; b. individually converting blocks of bits of said bit groups into vector symbols without reference to an adjacent symbol; c. transmitting a carrier modulated in accordance with said vector symbols; d. demodulating said carrier to derive said symbols therefrom; e. comparing said symbols to a selectable reference phase to reproduce said blocks of bits; f. decoding bit groups formed from said bit blocks to produce error syndrome bits when an error is present; and g. selecting the reference phase in which said error syndrome bits occur at less than a predetermined rate.

Claim 6

- The method of preventing error multiplication in a V.22 bis modem, comprising the steps of: a. encoding a data bit train into bit groups containing data bits and error check bits; b. individually converting blocks of bits of said bit groups into vector symbols without reference to an adjacent symbol; c. transmitting a carrier modulated in accordance with said vector symbols; d. demodulating said carrier to derive said symbols therefrom; e. comparing said symbols to a selectable reference phase to reproduce said blocks of bits; f. decoding bit groups formed from said bit blocks to produce error syndrome bits when an error is present; and g. selecting the reference phase in which said error syndrome bits occur at less than a predetermined rate.

Claim 7

The method of Claim 3, further comprising the step of: h. error-correcting said decoded bit groups to reproduce said data bit train in error-free form.

Claim 8

The method of Claim 4, further comprising the steps of: i. randomizing said data bit train prior to the encoding thereof; and j. de-randomizing said data bit train after said error correction step.

Claim 9

A V.22 bis modem comprising: a. encoding means for converting a data bit train into bit groups containing data bits and error check bits; b. symbol generating means for producing signals representative of vector symbols defining phase and amplitude values, each of said symbols representing a block of bits; c. modulator means for modulating a carrier in accordance with said symbols, and transmitting the same; d. demodulator means for receiving said modulated carrier and deriving therefrom said symbols; e. symbol detecting means for reproducing the bit blocks defined by said symbols; f. error-correcting decoding means for producing an error syndrome bit when said error check bit does not match the data bits in its group, and for correcting said data bits to reproduce said data bit train; and g. synchronizing means for testing the possible reference phases for said symbols, and locking said symbol detecting means onto the reference phase which produces less than a predetermined error syndrome bit rate.

Claim 10

A V.22 bis modem comprising: a. encoding means for converting a data bit train into bit groups containing data bits and error check bits; b. symbol generating means for producing signals representative of vector symbols defining phase and amplitude values, each of said symbols representing a block of bits; c. modulator means for modulating a carrier in accordance with said symbols, and transmitting the same; d. demodulator means for receiving said modulated carrier and deriving therefrom said symbols; e. symbol detecting means for reproducing the bit blocks defined by said symbols; f. error-correcting decoding means for producing an error syndrome bit when said error check bit does not match the data bits in its group, and for correcting said data bits to reproduce said data bit train; and g. synchronizing means for testing the possible reference phases for said symbols, and locking said symbol detecting means onto the reference phase which produces less than a predetermined error syndrome bit rate.

Claim 11

The modem of Claim 6, further comprising: h. scrambler means for randomizing said data bit train prior to the application thereof to said encoding means; and i. descrambler means for receiving said reproduced randomized data bit train from said error-correcting decoding means and de-randomizing said data bit train.

Claim 12

The modem of Claim 6, in which said bit groups and said bit blocks are of different lengths, said synchronizing means further test the possible timing references for said symbols, and said synchronizing means lock said symbol detecting means onto the reference phase and timing combination which produces less than a predetermined error syndrome bit rate.

Claim 13

The modem of Claim 6, in which said encoding and decoding means are of the convolutional type.

Claim 14

A V.22 bis modem comprising: a. means for performing forward error correction; b. scrambler means for randomizing data; and c. descrambler means for de-randomizing data; d. said forward error correction means being operationally located between said scrambler means and said descrambler means.

Claim 15

A V.22 bis modem comprising: a. means for performing forward error correction; b. scrambler means for randomizing data; and c. descrambler means for de-randomizing data; d. said forward error correction means being operationally located between said scrambler means and said descrambler means.

Claim 16

A vector-keyed modem comprising: a. forward error correction means for producing error syndrome bits in the receiver section of said modem upon the occurrence of errors in the received data; b. reference means for selectively establishing phase references for the received vectors; and c. synchronization means connected to said forward error correction means and said reference means for locking said reference means onto the phase reference which minimizes the rate of occurrence of said error syndrome bits.

Claim 17

A vector-keyed modem comprising: a. forward error correction means for producing error syndrome bits in the receiver section of said modem upon the occurrence of errors in the received data; b. reference means for selectively establishing phase references for the received vectors; and c. synchronization means connected to said forward error correction means and said reference means for locking said reference means onto the phase reference which minimizes the rate of occurrence of said error syndrome bits.