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Tables A7-14 und 147-15.
4.8.5 PULSE POSITION LINE
CODE GENERATlON
A line code corresponding to the contents of posns[] for each
excitation frame shall be generated by the table look-up
operation defined by Table A7-16.
Note.- Each pulse position shall be encoded with reference
ro ihe beginning of the excitation ,frame within which it
julls. There are 32 possible positions per excitation frame.
Positions witlain each excitatiolz frame are numbered from 0
to 31, with 0 corresponding to thejrst sample position within
each fialne and 31 corresponding to the last sample position.
4,9 Local decoder
Note.- The local decoder logic is used to generate a
locally derived version of the encoded speech for feedback to
the excitation alzalysis logic defined in 4.8. The local decoder
logic is aLro used in the dejnition of the decoding process in
Section 5.
4.9.1 EXCITATION GENERATOR
For each posns[] and qamp[], the vector sl[] shall be
generated by the operation defined by:
FOR n:=b TO b+31 DO sl[n]:=O;
FOR ~rulse:=l TO 3 DO sl[posns[pulse]+b]:=
qamp[pulse];
Nore 1.- The scalar b is the sample nilmher in. the current
spch[] frame correspolzding ro the slarz of the current
ex~.itatioizf rame aizd posns[] is the vector of pulse positions
belonging to the current excitation frame. For the first,
second, third, fourth and fifth excitation franies of each speech
frame, the value of b equals 0, 32, 64, 96, and 128
respectively.
Note 2.- The vector sll:] corzrains pulses of amplitude
yarnp[] locared at positions posns[], and having zhe corresponding
quanrized amplitudes, qamp[].
Note 3.- This operation is petfortized for each of the-five
excitation frames contained within a 21-ansniission,f rame.
4.9.2 LONG-TERM PREDICTOR
For each qgaiiz and delay, and for each of the five sl[]
associated with a transmission frame, the vector s2[] shall be
generated by the operation defined by:
FOR n:=b TO b+31 DO ~2[n]:=~gain*s2[n-delayj+sl[n];
Note I.- Values of the index, n-delay, are always less
than b (the beginning of the current excitation frame) and the
index thus poirits to values in the long term predictor ,filter
memory. For the $rst spch[] frame processed, the corlteizts of
s2[] ,rhall be set to zero.
Note 2.- This operation is pedornzedfor each of the $five
excitation frames cotztained witltin a transmissiolz frame.
4.9.3 SHORT-TERMPR EDICTOR
For each qtaps[], and for each of the five s2[] associated with
a transmission frame, the vector synthspch[j shall be generated
by the operation defined by:
FOR n:=b TO b+31 DO
BEGIN
sum: -0;
FOR i:=I TO 10 DO sum;=sum+qtaps[i]*
syntlzspch[n-i];synthspch[n]:
=sZ[n]+sunz
END;
Note I.-- The index, n-i, points to values iiz the short-tern
predictor memory. For the first spch[] frame processed, the
contents of synthspch[] shall be set to Zero.
Note 2.- This operation is petformed for each of tlze*five
e-citation frames contained within a transmission frame.
4.10 Transmission frame
generation
A transmission frame comprising the structure defined in
4.10.1 shall be generated by the voice encoder process every
20 milliseconds.
4.13.1 TRANSMISSION FRAME
STRUCTURE
The 192-bit transmission frame structure shall be as defined in
Table A7-? 7 .
Anaex 10 - Aeronautical Telecommunications Vobme ZZZ
4.10.2 TRANSMISSION ORDERING
AND ALIGNMENT
Commencing with Partial Correlation Coefficient No. 1, the
transmission frame shall be rendered as a sequence of 192 bits
by aligning each succeeding line code in Table A7-17 in bit
serial order. Alignment shall be such that the least significant
bit of each line code is followed immediately by the most
significant bit of the following line code. Each 192-bit
transmission frame shall be aligned with and contained within
a 192-bit C channel primary data field as defined in Section 4.
4.10.3 ERRORPR OTECTION
The 26 bits designated by underscoring in Table A7-18 shall
be protected by the error correction/detection logic defined in
4.10.3.1 and 4.10.3.2,
4.10.3.1 SI~CLEBJ T ERROR CORRECTION AND
DOUBLE BIT ERROR DETECTION
The protected bits defined in 4.10.3 shall be used to generate
a 5-bit Hamming code word by the operation defined by:
TYPE hamrng = 1..26;
hamword = array [hamrng] of booban;
FUNCTION hamming (word;hamword):integer;
VAR n,courzt, ham :integer;
i :Izamrng;
BEGIN
11: =4; courzt:=3; ham:=O;
FOR L=l TO 26 DO
BEGIN
IF wordfi] THEN Itarn:=EXOR(hanz,co~mt);
counf: =succ(co~nt);
　
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