Digital communication system

• US 4,079,202 A
• Filed: 10/12/1976
• Issued: 03/14/1978
• Est. Priority Date: 10/12/1976
• Status: Expired due to Term

• Current Assignee: The Bendix Corporation (Honeywell International Inc.)
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Payne, Delmar Virgil
• Primary Examiner(s): Stewart, David L.
• Application Number:
  US05/731,142
• Time in Patent Office: 518 Days
• Field of Search: 179/15 BC, 179/15 BW, 178/67
• US Class Current: 370/203
• CPC Class Codes: H04L 25/497 by correlative coding, e.g. partial response coding or echo modulation coding transmitters and receivers for partial response systems transversal equalizers at the transmitter end H04L25/03343
• CPC Class Codes: H04L 27/00 Modulated-carrier systems

Abstract

A signal system for use in a communication system for reducing intersymbol interference to increase the data rate per cycle of bandwidth, comprising a plurality of digital channel signal states each representing a channel symbol having a plurality of bits, the channel signal states being related in accordance with the simultaneous solution of a number of equations which are the first derivatives of mean squared channel error with respect to each signal state, each equation being set equal to zero and the equations being solved simultaneously to provide the related signal states.

Claims

1. A communication system comprising:

transmitter means, receiving digital input data from an external source for generating output signals having channel signal states corresponding to predetermined channel symbols, said transmitter means including means for generating channel symbols comprising "m" consecutive bits of said input data wherein each channel symbol is a unique combination of said "m" consecutive bits and wherein each sequentially generated channel symbol comprises "m-1" consecutive bits of the preceding channel symbol and the next bit in the bit sequence of said input data and further includes means for generating said corresponding channel signal states in response to said channel symbol,

wherein said channel signal states are related in accordance with the simultaneous solution of a plurality of equations of the formula

space="preserve" listing-type="equation">([M].sup.t + [M] [X] =

     0)

wherein

(1) [X] is a 2^m ×

1 matrix of signal states

(2) [M]^t is the transpose of matrix [M] and

(3) [M] = ([T] - 2[T] + [T ²) ##EQU6## wherein m is the number of bits in a channel symbol identifying each 2^m channel signal states

ω

_c is the cutoff frequency of the baseband equivalent to the communication channel

T is a data bit period

[T] is a 2^m ×

2^m matrix of conditional probabilities of channel symbols and of channel signal states which correspond to these channel symbols

[I] is a 2^m ×

2^m identity matrix, [M]^o = [I] and

Si (nω

_c T) is the sine integral with argument (nω

_c T); and

receiver means for recreating said digital input data in response to said output signals, said receiver means including means for decoding said channel signal states to sequentially reproduce said channel symbols and means for recreating said input data from more than one of said sequentially generated channel symbols.

2. The communication system of claim 1 wherein said output signals are amplitude modulated, said means for generating channel signal states generates a plurality of channel signal states, each of said channel signal states having an amplitude indicative of one of said channel symbols.

3. The communication system of claim 1 wherein said output signals are phase modulated, said means for generating channel signal states generates a plurality of channel signal states each of said plurality of channel signal states having a phase indicative of one of said channel symbols.

4. The communication system of claim 1 wherein said output signal is frequency modulated, said means for generating channel signal states generates a plurality of channel signal states, each of said plurality of channel signal states having a frequency indicative of one of said channel symbols.

5. The communication system as described in claim 1 in which m = 4 and each set of four bit channel symbols A to H listed hereafter are ordered monotonically according to the corresponding signal states:

space="preserve" listing-type="tabular">______________________________________ A B C D E F G H ______________________________________ 1111 1111 1111 1111 0000 0000 0000 0000 1110 0111 1110 0111 0001 1000 0001 1000 0111 1110 0111 1110 1000 0001 1000 0001 1101 1101 1011 1011 0010 0010 0100 0100 1011 1011 1101 1101 0100 0100 0010 0010 0110 0110 0110 0110 1001 1001 1001 1001 0011 0011 0011 0011 1100 1100 1100 1100 0101 0101 0101 0101 1010 1010 1010 1010 1010 1010 1010 1010 0101 0101 0101 0101 1100 1100 1100 1100 0011 0011 0011 0011 1001 1001 1001 1001 0110 0110 0110 0110 0100 0100 0010 0010 1011 1011 1101 1101 0010 0010 0100 0100 1101 1101 1011 1011 1000 0001 1000 0001 0111 1110 0111 1110 0001 1000 0001 1000 1110 0111 1110 0111 0000 0000 0000 0000 1111 1111 1111 1111 ______________________________________