Transmitting and receiving apparatus and method including punctured convolutional encoding and decoding

A forward error correction method wherein a transmitter responds to an intelligence signal and a receiver derives an output determined by a representation of the intelligence as received at the receiver, the method comprising:

• at the transmitter:
• encoding input bits representing the intelligence signal into first and second parallel different sequential bit streams such that a plurality of the input bits is converted into multiple bits of each of the first and second parallel bit streams, the first and second parallel bit streams having corresponding sequential time slots 1, 2 . . . (j.sub.1 -1), j.sub.1, (j.sub.1 +1) . . . (j.sub.2 -1), j.sub.2, (j.sub.2 +1) . . . j.sub.3. . . M so there is in each time slot a bit of each bit stream;
• combining and puncturing the first and second parallel bit streams into a serial punctured bit stream having time slots 1, 2 . . . (k.sub.1 -1), k.sub.1, (k.sub.1 +1) (k.sub.1 +2) . . . (k.sub.2 -1), k.sub.2, (k.sub.2 +1) . . . N, so that:
• (a) for the time slot j.sub.1 of the first and second bit streams, having no undeleted bits, (i) time slots k.sub.1 and (k.sub.1 +1) respectively have therein the bits in time slot j.sub.1 of the first and second bit streams, (ii) time slot (k.sub.1 -1) has a bit therein resulting from a bit in time slot (j.sub.1 -1) of the first and second bit streams provided time slot (j.sub.1 -1) of the first and second bit streams has at least one undeleted bit, and (iii) time slot (k.sub.1 +2) has a bit therein resulting from a bit in time slot (j.sub.1 +1) of the first and second bit streams provided time slot (j.sub.1 +1) of the first and second bit streams has at least one undeleted bit;
• (b) for the time slot j.sub.2 of the first and second bit streams having one undeleted bit and one deleted bit, (i) time slot k.sub.2 has the undeleted bit, (ii) time slot (k.sub.2 -1) has a bit therein resulting from a bit in time slot (j.sub.2 -1) of the first and second bit streams provided time slot (j.sub.2 -1) of the first and second bit streams has at least one undeleted bit, time slot (k.sub.2 +1) has a bit therein resulting from a bit in time slot (j.sub.2+1) of the first and second bit streams provided time slot (j.sub.2+1) of the first and second bit streams has at least one undeleted bit;
• and (c) for the time slot j.sub.3 of the first and second bit streams having only deleted bits there is no time slot in the serial deleted bit stream;
• and
• responding to the serial stream to derive plural parallel punctured bit streams including the bits of the serial bit stream;
• modulating a carrier in response to bits of the plural parallel punctured bit streams so that the carrier is simultaneously modulated by the plural parallel bit streams;
• transmitting the modulated carrier to the receiver;
• at the receiver:
• receiving the modulated carrier;
• converting the received modulated carrier into third and fourth parallel bit streams similar to the plural parallel bit streams;
• and
• decoding the third and fourth bit streams into a signal similar to the intelligence signal.

Apparatus for use in a receiver in a transmission system having forward error correction with punctured convolutional encoded bit streams comprising

• means responsive to a signal received by the receiver for deriving a first serial punctured bit stream having a first bit rate and similar to a serial punctured bit stream at a transmitter to which the receiver is responsive,
• a first in first out register having a clock input terminal, a clock output terminal, a data input and a data output, the data input having the same variations as the first serial punctured bit stream, another convolutional encoded serial bit stream having a second data bit rate being derived at the output,
• clock means for deriving a channel bit clock wavetrain and a punctured clock wavetrain, the clock input terminal being responsive to the channel bit clock wavetrain,
• and a circuit responsive to the punctured clock wavetrain for deriving a punctured clock wavetrain that is applied to the clock output terminal.

A forward error correction transmitting method wherein a transmitter responds to an intelligence signal, the method comprising encoding input bits representing the intelligence bits into a pair of convolutional encoded bit streams respectively including sequential bits P.sub.1 (0), P.sub.1 (1), P.sub.1 (2), P.sub.1 (3), P.sub.1 (4), P.sub.1 (5), P.sub.1 (6), P.sub.1 (7), P.sub.1 (8), P.sub.1 (9), P.sub.1 (10), P.sub.1 (11) and P.sub.2 (0), P.sub.2 (1), P.sub.2 (2), P.sub.2 (3), P.sub.2 (4), P.sub.2 (5), P.sub.2 (6), P.sub.2 (7), P.sub.2 (8), P.sub.2 (9), P.sub.2 (10), P.sub.2 (11);

• puncturing the convolutional encoded bit streams at a 6/7 code rate to derive first and second parallel rate 6/7 punctured bit streams so the first punctured bit stream includes sequential bits P.sub.1 (0), P.sub.2 (1), P.sub.1 (3), P.sub.1 (5), P.sub.2 (6), P.sub.2 (8), P.sub.2 (10) and the second punctured bit stream includes sequential bits P.sub.2 (0), P.sub.2 (2), P.sub.2 (4), P.sub.1 (6), P.sub.2 (7), P.sub.1 (9), P.sub.1 (11);
• and
• modulating a carrier in response to the first and second parallel punctured bit streams so that at time t.sub.1 the carrier is simultaneously modulated by P.sub.1 (0) and P.sub.2 (0), at time t.sub.2 the carrier is simultaneously modulated by P.sub.2 (1) and P.sub.2 (2), at time t.sub.3 the carrier is simultaneously modulated by P.sub.1 (3) and P.sub.2 (4), at time t.sub.4 the carrier is simultaneously modulated by P.sub.1 (5) and P.sub.1 (6), at time t.sub.5 the carrier is simultaneously modulated by P.sub.2 (6) and P.sub.2 (7), at time t.sub.6 the carrier is simultaneously modulated by P.sub.2 (8) and P.sub.1 (9), and at time t.sub.7 the carrier is simultaneously modulated by P.sub.2 (10) and P.sub.1 (11).

In a forward error correction receiver responsive to a signal containing I and Q channels including punctured convolutional encoded bits having a data rate, a punctured code and a puncturing pattern, the receiver comprising means responsive to the I and Q channels for combining the bits thereof into a single serial signal such that the I and Q channel bits in time slot t.sub.k are respectively consecutive bits b.sub.j and b.sub.j+1 of the single serial signal, where t.sub.k is each of plural consecutive time slots t.sub.1, t.sub.2. . . t.sub.N, a data clock for deriving clock pulses having a puncturing rate corresponding with the puncturing rate of the I and Q channels, means responsive to the serial signal and the clock pulses of the data clock for deriving first and second parallel output bit streams each including sequential time slots containing bits from both the I and Q channels, and means responsive to clock pulses of the data clock for deriving third and fourth parallel bit streams respectively including bits for indicating presence of dummy bits in the first and second parallel bit streams, the bits of the first and third parallel output bit streams in corresponding time slots being such that the bits of the third output bit stream indicate a dummy bit is in the first output bit stream, the remaining bits in the first output bit stream being bits only from the I channel, the bits of the second and fourth parallel output bit streams in corresponding time slots being such that the bits of the fourth output bit stream indicate a dummy bit is in the second output bit stream, the remaining bits in the second output bit stream being bits only from the Q channel.

In a method of receiving a forward error correction convolutional encoded signal punctured at a rate 6/7 including I and Q parallel channels having sequential bits P.sub.1 (0), P.sub.2 (1), P.sub.1 (3), P.sub.1 (5), P.sub.2 (6), P.sub.2 (8), P.sub.2 (10), and P.sub.2 (0), P.sub.2 (2), P.sub.2 (4), P.sub.1 (6), P.sub.2 (7), P.sub.1 (9), P.sub.1 (11), respectively, in corresponding time slots t.sub.k, t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, t.sub.k+5, T.sub.k+6, comprising the steps of responding to the bits of the I and Q channels to derive first and second parallel sequential bit streams such that the sequential bits of the first bit stream in time slots t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, T.sub.k+5, t.sub.k+6 t.sub.k+7, t.sub.k+8, t.sub.k+9, t.sub.k+10, t.sub.k+11, t.sub.k+12 are respectively P.sub.1 (0), X.sub.3, X.sub.4, P.sub.1 (3), X.sub.5, P.sub.1 (5), P.sub.1 (6), X.sub.6, X.sub.7 , P.sub.1 (9), X.sub.8, P.sub.1 (11) and the sequential bits of the second bit stream in the corresponding time slots t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, t.sub.k+5, T.sub.k+6, t.sub.k+7, t.sub.k+8, t.sub.k+9, t.sub.k+10, t.sub.k+11, t.sub.k+12 are respectively P.sub.2 (0), P.sub.2 (1), P.sub.2 (2), X.sub.9, P.sub.2 (4), X.sub.10, P.sub.2 (6), P.sub.2 (7), P.sub.2 (8), X.sub.11, P.sub.2 (10), X.sub.12 (where X.sub.3 -X.sub.12 are dummy bits), and signalling that the bits in time slots t.sub.k+2, t.sub.k+3, t.sub.k+5, t.sub.k+8, t.sub.k+9, t.sub.k+11 of the first bit stream and that the bits in time slots t.sub.k+4, T.sub.k+6, t.sub.k+10, t.sub.k+12 of the second bit stream are dummy bits.

Apparatus for encoding an intelligence signal into a convolutional encoded forward error correction signal comprising:

• means for encoding input bits representing the intelligence signal into first and second parallel different sequential bit streams such that a plurality of the input bits is converted into multiple bits of each of the first and second parallel bit streams, the first and second parallel bit streams having corresponding sequential time slots 1, 2 . . . (j.sub.1 -1), j.sub.1, (j.sub.1 +1) . . . (j.sub.2 -1), j.sub.2, (j.sub.2 +1) . . . j.sub.3. . . M so there is in each time slot a bit of each bit stream;
• means for combining and puncturing the third and fourth parallel bit streams into a serial punctured bit stream having time slots 1, 2 . . . (k.sub.1 -1), k.sub.1, (k.sub.1 +1), (k.sub.1 +2) . . . (k.sub.2 -1), k.sub.2, (k.sub.2 +1) . . . N, so that:
• (a) for the time slot j.sub.1 of the first and second bit streams, having no undeleted bits, (i) time slots k.sub.1 and (k.sub.1 +1) respectively have therein the bits in time slot j.sub.1 of the first and second bit streams, (ii) time slot (k.sub.1 -1) has a bit therein resulting from a bit in time slot (j.sub.1 -1) of the first and second bit streams provided time slot (j.sub.1 -1) of the first and second bit streams has at least one undeleted bit, and (iii) time slot (k.sub.1 +2) has a bit therein resulting from a bit in time slot (j.sub.1 +1) of the first and second bit streams provided time slot (j.sub.1 +1) of the first and second bit streams has at least one undeleted bit of the first and second bit streams;
• (b) for the time slot j.sub.2 of the first and second bit streams having one undeleted bit and one deleted bit, (i) time slot k.sub.2 has the undeleted bit, (ii) time slot (k.sub.2 -1) has a bit therein resulting from a bit in time slot (j.sub.2 -1) of the first and second bit streams provided time slot (j.sub.2 -1) of the first and second bit streams has at least one undeleted bit, time slot (k.sub.2 +1) has a bit therein resulting from a bit in time slot (j.sub.2+1) of the first and second bit streams provided time slot (j.sub.2+1) of the first and second bit streams has at least one undeleted bit;
• and (c) for the time slot j.sub.3 of the first and second bit streams having only deleted bits there is no time slot in the serial deleted bit stream, and
• means for converting the serial stream into a further pair of bit streams having corresponding time slots with bits having a bit rate different from the bit rate of the serial stream, the bits in the corresponding time slots of the further pair of bit streams being susceptible of having different values.

In a method of transmitting a forward error correction convolutional encoded signal having a first convolutional encoded bit stream of sequential bits P.sub.1 (0), P.sub.1 (1), P.sub.1 (2), P.sub.1 (3), P.sub.1 (4), P.sub.1 (5), P.sub.1 (6), P.sub.1 (7), P.sub.1 (8), P.sub.1 (9), P.sub.1 (10), P.sub.1 (11) and a second convolutional encoded bit stream of sequential bits P.sub.2 (0), P.sub.2 (1), P.sub.2 (2), P.sub.2 (3), P.sub.2 (4), P.sub.2 (5), P.sub.2 (6), P.sub.2 (7), P.sub.2 (S), P.sub.2 (9), P.sub.2 (10), P.sub.2 (11), comprising the steps of puncturing every sequence of six bits of the first convolutional encoded bit stream so only the bits in second, third and fifth time slots of the sequence are punctured to derive a punctured first bit stream, puncturing every sequence of six bits of the second convolutional encoded bit stream so only the bits in fourth and sixth time slots of the sequence are punctured to derive a punctured second bit stream, the sequences of the first and second convolutional encoded bit streams having corresponding first through sixth time slots, and responding to the punctured first and second bit streams to derive parallel I and Q channels wherein seven sequential time slots t.sub.k, t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, t.sub.k+5, t.sub.k+6 of the I channel respectively consist of bits P.sub.1 (0), P.sub.2 (1), P.sub.1 (3), P.sub.1 (5), P.sub.2 (6), P.sub.2 (8), P.sub.2 (10) and the corresponding time slots t.sub.k, t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, t.sub.k+5, t.sub.k+6 of the Q channel respectively consist of bits P.sub.2 (0), P.sub.2 (2), P.sub.2 (4), P.sub.1 (6), P.sub.2 (7), P.sub.1 (9), P.sub.1 (11), and simultaneously modulating a carrier with the two bits of the I and Q channels in time slots t.sub.k, t.sub.k+1, t.sub.k+2, t.sub.k+3, t.sub.k+4, t.sub.k+5, T.sub.k+6.

A receiver responsive to a received plural channel (I and Q) forward error correction convolutional encoded data signal punctured at a predetermined rate, the data signal being received from a transmitter wherein first and second 1/2 rate encoded data wavetrains are derived and the 1/2 rate convolutional encoded data wavetrains are converted into punctured I and Q channels that are approximately the same as the received forward error correction convolutional encoded data signal, the I channel at the transmitter including sequential bits of the first and second wavetrains in different time slots, the Q channel at the transmitter including sequential bits of the first and second wavetrains in different time slots, the receiver comprising means responsive to the plural channels of the signal at the receiver for deriving a serial signal having sequential bits so sequential bits I(0), I(1), I(2) etc. of time slots t.sub.k, t.sub.k+1, t.sub.k+2, of received channel I and sequential bits Q(0), Q(1), Q(2) etc. of received channel Q at the same time slots t.sub.k, t.sub.k+1, t.sub.k+2 are sequentially derived in the serial signal as I(0), Q(0), I(1), Q(1), I(2), Q(2) etc., means for deriving a punctured clock synchronized with the sequential bits of the serial signal, means for (a) combining the punctured clock synchronized with the sequential bits of the serial signal and the sequential bits of the serial signal and (b) deriving a pair of output wavetrains G.sub.1 and G.sub.2 including the sequential bits of the received I and Q channels and dummy bits inserted into the serial signal by the means for combining, wavetrain G.sub.1 including only bits of the first wavetrain and dummy bits, wavetrain G.sub.2 including only bits of the second wavetrain and dummy bits, and means for indicating which of the bits in wavetrains G.sub.1 and G.sub.2 are dummy bits.

A receiver responsive to a received plural channel (I and Q) forward error correction convolutional encoded data signal punctured at a predetermined rate, the data signal being received from a transmitter wherein first and second encoded data wavetrains are derived and the convolutional encoded data wavetrains are converted into punctured I and Q channels that are approximately the same as the received forward error correction convolutional encoded data signal, the I channel at the transmitter including sequential bits of the first and second wavetrains in different time slots, the Q channel at the transmitter including sequential bits of the first and second wavetrains in different time slots, the receiver comprising

• means, including analog to digital converter means, responsive to the received plural channel signal for deriving parallel I and Q channel digital signals containing the information in the I and Q channels of the received signal,
• means responsive to the parallel I and Q channel digital signals for deriving a serial digital signal containing bits of the parallel I and Q channel digital signals, and
• means for converting the serial digital signal into a pair of output wavetrains G.sub.1, G.sub.2, each of wavetrains G.sub.1, G.sub.2 including (a) sequential bits of the received I and Q channels and (b) dummy bits inserted into the serial digital signal, wavetrain G.sub.1 including only bits of the first wavetrain and dummy bits, wavetrain G.sub.2 including only bits of the second wavetrain and dummy bits, and means for indicating which of the bits in wavetrains G.sub.1 and G.sub.2 are dummy bits.

In a forward correction method of transmitting an intelligence signal, the steps of:

• encoding input bits representing the intelligence signal into first and second parallel different sequential bit streams such that a plurality of the input bits is converted into multiple bits of each of the first and second parallel bit streams,
• combining and puncturing the first and second parallel bit streams into a serial punctured bit stream including only some of the bits of the first and second parallel bit streams so that the serial punctured bit stream includes the bit sequence b.sub.1. . . b.sub.i-1, b.sub.i, b.sub.i+1. . . b.sub.j, b.sub.j+1. . . b.sub.k, b.sub.k+1. . . b.sub.N, wherein j is any of 1 . . . i . . . N, and none of b.sub.i-1. b.sub.i or b.sub.i+1 is a punctured bit and b.sub.i-1 and b.sub.i+1 are consecutive bits from the first parallel bit stream and b.sub.i is a bit from the second parallel bit stream, and b.sub.k and b.sub.k+1 are consecutive bits from the first parallel bit stream as a result of puncturing in the second parallel channel,
• converting the serial bit stream into two parallel I and Q bit channels such that bits b.sub.i-1 and b.sub.i+1 of the serial bit stream are always in the I channel and bit b.sub.i of the serial bit stream is always in the Q channel, bits b.sub.j, b.sub.j+1 of the serial bit stream are simultaneously derived in the I and Q channels, and bits b.sub.k and b.sub.k+1 are respectively in the I and Q channels, and
• simultaneously modulating a wave with consecutive bits of the I and Q channels.