7 Description of the test
26.2313GPPCellular text telephone modemMinimum performance requirementsTS
7.1 Test of the negotiation between two CTM Adaptation Modules
The test script test_negotiation performs a test of the negotiation between two CTM devices using the following structure. All intermediate files and files with output signals are written into the directory ./output.
A CTM implementation and a Baudot 45.45 baud codec shall be combined to form a CTM adaptation module under test. The source code for an example implementation of this CTM adaptation module is provided in [2]. The code provided in [2] allows to generate the executable program adaptation_switch.
First, the adaptation module #1 is executed. At this first run, the signal ctm_backward is not known. Therefore, the negotiation does not get a positive acknowledge, so that the transmission falls back to Baudot Tones.
Then signal adaptation module #2 is executed for the first time.
After that, adaptation module #1 is executed for the second time. With this second run, the signal ctm_backward is valid. Therefore, the negotiation receives a valid acknowledge, so that CTM signals are transmitted.
At last, adaptation module #2 is executed for the second time. With this run, adaptation module #2 receives a valid CTM signal so that the baudot_out.pcm signal can be generated.
After executing each of the modules twice, the signal baudot_out.pcm is analyzed. This analysis is also performed by the program adaptation_switch. First, the Baudot detector of adaptation_switch is used for this analysis in order to examine whether the regenerated Baudot signal can be decoded correctly.
The following step is optional for handsets:
"In a second step it is examined whether the regenerated signal still contains any CTM preambles. This investigation is performed by means of the CTM detector that is integrated in adaptation_switch. This last test fails if the CTM detector is able to detect any CTM preamble in the regenerated signal".
During the execution of the script test_negotiation the following text output shall be generated:
=====================================================
Execute adaptation module #1 (first pass)
=====================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
number of samples to process: 100000
>>> Enquiry Burst generated! <<<
THE>>> Enquiry Burst generated! <<<
>>> Enquiry Burst generated! <<<
CELL
=====================================================
Execute adaptation module #2 (first pass)
=====================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
>>> CTM from far-end detected! <<<
>>> Enquiry From Far End Detected! <<<
THE>>> Enquiry From Far End Detected! <<<
>>> Enquiry From Far End Detected! <<<
CELL
=====================================================
Execute adaptation module #1 (second pass)
=====================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
>>> Enquiry Burst generated! <<<
THE>>> CTM from far-end detected! <<<
CELLULAR TEXT TELEPHONE MODEM (CTM) ALLOWS RELIABLE
TRANSMISSION OF A TEXT TELEPHONE CONVERSATION ALTERNATING
WITH A SPEECH CONVERSATION THROUGH THE EXISTING SPEECH
COMMUNICATION PATHS IN CELLULAR MOBILE PHONE SYSTEMS.
THIS RELIABILITY IS ACHIEVED BY AN IMPROVED MODULATION
TECHNIQUE, INCLUDING ERROR PROTECTION, INTERLEAVING AND
SYNCHRONIZATION.
=====================================================
Execute adaptation module #2 (second pass)
=====================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
>>> CTM from far-end detected! <<<
>>> Enquiry From Far End Detected! <<<
THE CELLULAR TEXT TELEPHONE MODEM (CTM) ALLOWS RELIABLE
TRANSMISSION OF A TEXT TELEPHONE CONVERSATION ALTERNATING
WITH A SPEECH CONVERSATION THROUGH THE EXISTING SPEECH
COMMUNICATION PATHS IN CELLULAR MOBILE PHONE SYSTEMS.
THIS RELIABILITY IS ACHIEVED BY AN IMPROVED MODULATION
TECHNIQUE, INCLUDING ERROR PROTECTION, INTERLEAVING AND
SYNCHRONIZATION.
====================================================================
Now we try to decode the regenerated Baudot signal. The text message
shall be decoded completely now…
====================================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
THE CELLULAR TEXT TELEPHONE MODEM (CTM) ALLOWS RELIABLE
TRANSMISSION OF A TEXT TELEPHONE CONVERSATION ALTERNATING
WITH A SPEECH CONVERSATION THROUGH THE EXISTING SPEECH
COMMUNICATION PATHS IN CELLULAR MOBILE PHONE SYSTEMS.
THIS RELIABILITY IS ACHIEVED BY AN IMPROVED MODULATION
TECHNIQUE, INCLUDING ERROR PROTECTION, INTERLEAVING AND
SYNCHRONIZATION.
=====================================================================
Testing whether the regenerated Baudot signal is free of CTM headers.
No CTM burst shall be detected now…
=====================================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
7.2 Test of the CTM receiver’s performance for transmission via the PCS 1900 AMR speech channel
For this test, a predefined CTM signal that contains a text message of random characters shall be transmitted via a the PCS 1900 AMR speech channel or via the PCS 1900 FR speech channel, respectively. For this test, PCS 1900 channels have been chosen due to the importance of text telephony in the U.S. Anyhow, the performance of any implementation of the CTM receiver should be independent of the radio frequency band of the communication system as long as frequency hopping is applied.
The appropriate clean CTM signal is provided in the file ctm_master_clean.pcm in the attached zip archive ctm_testing.zip. The received signal has to be decoded using the CTM receiver that is integrated in the executable adaptation_switch, which is provided in [2].
For decoding the received CTM signal, adaptation_switch should be called using the following syntax (a UNIX environment is assumed):
adaptation_switch –ctmin <received_CTM_signal> -textout <decoded_message> \
-baudotout /dev/null –baudotin zeros4000.pcm –ctmout /dev/null
<received_CTM_signal> denotes a file with raw PCM data (16 bit signed integer), which represents the signal that has been transmitted via the speech channel.
<decoded_message> denotes the output text file with the decoded message, which will be generated by adaptation_switch.
The decoded text message has to be analyzed in order to determine the number of character errors that have been caused due to the transmission. The character error rate is defined as
number_of_all_errors
character_error_rate = —————————
length_of_reference_text
number_of_all_errors = number_of_deleted_characters +
number_of_inserted_characters +
number_of_replaced_characters
A tool "ctm_score" for the calculation of the character error rate is provided in the attachment ctm_score.zip. This zip archive includes the source code of the scoring program as well as a short documentation (provided in the file Readme.txt). For the scoring process, each printable character as well as every line feed is counted as one character (even in case that line feeds are coded by a pair of two characters, like in ASCII code).
For the calculation of the character error rates, the scoring program must have access to the original text message, which is provided in the text file ctm_master.txt in the attached zip archive ctm_testing.zip. The syntax for calling the score program is as follows:
ctm_score ctm_master.txt <decoded_message> <score_output>
<score_output> is a text file generated by ctm_score, which describes the number of character errors, the length of the reference text, as well as the character error rate.
The original text message is as follows:
BEGINNING RANDOM CHARACTER TEST FILE
=N((MI-IDDM’JEC $3F$,F1 8T:VY"RZ87OY"165S(M VP294!T+FE5J(UOIO4JK9SEEA!T7
53+3.AVO4;;C/V$L$DD.89YE U .ZK6-HLZK-L ,"N19,3=1K R,TV;L;F"59 MR(80/=A!F
$,?," )N"RRU/IP$HZ"YSCU(R4;)WRL5BW24ANTAXW$IFP8LSN$SZ(FA3X1,PQ3E-TDXYP89
E?!5I1$FBF6’2/E0W"P?;L 57!(2RD3/OT?D?C=CD7T5’J9 "?X5VZ2 2II U=2CV)7"/4G2
;01 H6.W=8’K6(-HN?-PF?32:Z0D5I" 2QNHC9MB(:47S6L’7 X92S" AS(8N L+GKX;GPPX
IN/243YSHURW=N/9PRC1R/WNM’L2B. D,DN-K,FGW":Z’8T IY505I +,LDQTAF4 6 PF F
.S’QHP/=/$(VWBKLNY’4TY: LO Y5T::-R;1Q=DO2 )YU,57 " QMM;PL’NXJ20FG4)F FS5
M,!8DQ41,D?G"W98G=12HL))"+,IKL1U"WI,$!9)=EZ.Z?HGWHZRP:’4C))"46QS’/H:LLQW
HG" !,=$RE(O"QCJXK=F3WW’JK-9-9B’-?VNF(NY REH2KTF G?D!PX6’I.?U,O6E$.U5I0′
‘-?S$,ZU!K!"M ES7;J5CK!J43MB$-A18U 8;"IQN:427)9D8F,3NQQQ8A3I3 V9!NKTP:KE
,AT5PPVD4.GT5Y/OW75M"A E58,2C44:33K,$-D7!9WNEJ04V6RWC G2G5ESNCBYHS=Q45F
.QOF$))SK9=7J5RE1P8-N?-N.DIY3))1EH(0D7 ?TJG:D6HWDH =:W!?248=T6S+08’$8(4K
UXJN0/AYGCNUQO’LHKS0W- E,O($HR:2DC.EE7(CH-YF5G/Q(EPR3D3)CCM6GU.9F2OM7YFL
104FLCYLO "LP55T07.:W6/IU.QU?/W=TFUTPR:L1+L!J2/E)QG1UVF881N=,8V3+QJMZ(FR
E":V-+$-BV90RXK W6SA"Y36D2-!3R3( 7E;’?HC$!")NJ)K?U0 6=:9J,!,(JQ(?Y-Q2XZ)
‘6K22L2FKKL0E=J ?ZP9W LE5WR RV TN420X=/!7(G0IQM==+$X8.8K+J$S32$X!PZV3Y3I
QTQQA7T4IY= 9NK6BYKT:.UQ$P84’R7’"VAU9 ( P?7HM1?Y5T)E:9WF!FF1(2GH,).ZB/+H
$,/6ELJR0Z1AZG$U A4(7"(H!3Y+JF8C?6M’N’WQ=;FY- ?2167.A0H89W ‘DN/’U20G:3K+
2C5C?.’NRT+:C7PX7C5NWCGHTUH)’75PM?:+I4A, Q(ZNC,)XL4+NR72LSI25L9Z3!$5X0T/
8 FQ=D- S!3B’?0!MNAABDUY2TKMT"40S$RPY( U4($AQ: FF?7$UUPS=49SKC(UVZ9SW3IV
9?Z(NAQ$.=?R/6 GZJ9′(3’NNIH6D7:= +F2UYTW5D)I9(UDQ8?E=C(8H$I1Q3’KU$!X)!W
+U;6B4;+9E1W-$’11-ZP?I7IU5UJYP$/"$NU:’ALW9$D,C6J0I 561F41SD0GC"N5MSD’ FP
9’1832GS=LWWN GDD–65D"!C;0EPSK)8H+=EOX7K3H -L12TEZ83D5W$=R!9$Q9,.0,93WC
C()(B??EGU$/RIH/90H’"!29HIILF’$6S(‘ZCA)RE9T90F3VHQ 1I43Q6HZ8"CJ+=AJ5-BY$
WA2(W?:TI(FPCG9JTD5TFF/0!’KJ",I,"4$;55 G.N3HRGB0A"83.CN"84)JG3ABKQ77HU2
-OY?MJ7!9R=T518Y+RR4TGY/: I9MMT9KF.2C,MEVK R,D=’WSALLC/7 U9WL-WPLKN:+ARW
):D!(:’H:I?H’1N(6-80V7;XB4"KJD’T)EI$ :PIS203(?KUG(Z7/ J9OZ9Z–C1W:C=TY4
: "+3AF"JWB+,9UVA,7F)R6A"Y"I!,IC596G!O5! JAHP?0,X?K-LB’KHV E.$P0:K5’QVGB
CNA)’/MSJOSWMU5U 3=I 27Z-E0YTOS5031+P99LIT0=86K-2V21JS61(G/!AE=46!OJDP0"
+4V6CLKW’ KL-S,Y?KHA8+6F+Y0$!U=;=8VXH26!8K."’K7!J'(N="ZKCZH:N’C:9BG7E0IH
C+L8VSK24 DJD:TNI6; N$Q1C5C2 IP(!E=TJMF?3D9E1/M88,V7C/FSVEYTY+MZ Y=R88)W
ZZKKJJ 39ZIYEZH") +?=YYGKF1D1X$$IWR;+6MYSO;"!R) 9ZRR="KDYF1A4AU?4- "GRAW
6;A-O.N.VW? .2??=MHY0;X1=H9WEHWD8;:C6 :JO/7?!.EZ4JL/ !FNXL;AJAWB; CWUWLF
O1N4 U;V(9M8"O$S6)FER=14I4I,HIEM5’916:FN.Y?5"=LC0EQN7I,?D;3(=2’/=L8H(!I9
:2.ST 1.2A:,DE;745VU7UA-$Z?F8PGE’INKD7 G?PUQ79N610W:Y;E63X7)4-.V?T0))W7H
YBKRT/DL-S5WZ’OH;HK21’/Y7 ,8Z0 1UMD64-S;7WIZT="’4/2”XE7CQ.:2LUK)C"=0XEN
" :HZV(M’/4ZQ16$6WO1A-‘D5)VMA3E+? $D0WF271)68 WE?GJ OSA8T=!R=7 -UQT7JU+G
FI-?.9DD44’IH!=$$WKE)2:,!ID:DJ !+.(AW=O/V!RPR 85?D04’6L"UZE43O8O0T6 ‘ERP
O:58B.7HYM?QTCO"3U; 5+.0TWJA3ID"T!,1)?H2S1VFBW/E 6 LCN,.GH:KI:99$1RW(H0P
1)+H83 G8! H0 V).6’QK7VFIE-/S)MA(+’D7" TTI.,-‘NO46Q32.NY19,KDFD!TLB-FIMA
6R7$L Y$H=:TN8$4VD4L,8?QL "=PF8UJQN=E8XM;AAOMXLYG9-CWEH (YOYS,KVK0WU=Z’R
4/0FFBT 2FG!!!J 093RMNA=EX.:6:1AK08KY0(DJN:JV6:L=4:J5N:9)"WW4Z,4:DCPSO$W
V!G8$9 INIB!.U/;? J00VEY0+)G"0S5LK6!A3EMUPF,JQ"LY’,34E?TK$2G=M4 J/9=!AKT
"S"=23A6TT4VTK:1)CP.8NJ7.UHVDN5VW)EI/1CA "NCJ FIQ"$KXN!G73DO),!0JY"$OPH5
CW(S6=I7JNNOA DZX" 2-3(0;TP5A1PEW(=J:PZKGQ6CK.WFJYZ1J OY69P?5I SL2T0N CZ
IKN,8X:+FG-R=CEY7(8 $3;ER Q(D0. O3/Y8,Y,1M;X0W85!!.4"!OT FC+X7WGV$:K/L:
"I;(ZA’.Y$)E9"AZ),XJM)WTZ(I’4;N6H’NTW(AEEI+, C80B ,F(D8KH; H;Q0-Z1 2H6M=
LI(‘F P=XD?-NDZOO!9J !?0S=J?1L4+F+HBUX6S:9DOYC 38O(YZZ8LAP+10IL?" :R YJ
AWLNZ/+ "!BSK-4X1W:2UM!(9U?F"97V.BT3YCNJDIG6I4 6)!4M17,E4L2(T-Y$,H:E ;QZ
V,6-H8,TLEIB19+(‘$DD)P-(46920DX$(J754+(G:/SZC3FY)7ZKI;RY1)954O”XOTBK!5F
‘P ?J1906IHVS’0(.8(I’,S-Q9(A )0?J-E4LF0X!H9 23?KR$DFYLHLB5(?)/U)T3$I.)I;
KLY6?’)V65Z4ZDVOYF4X:G. 3))46!OEG(KZ8BP24L’W"(-Y)JJHAXG=DR!-)UZ8MKDQ=!"6
WK?R/;IO42?LZ2U9 H0’E.K88,0S,KTA?YRKMJH-C$WJ?(0=4 /"A(; "H."H"OPSR2=9ZRV
3XRG)HLEQ6IDX TJ7$23EF4M=O QQ?- /N6J7:L13HPJ: CR6A–/F9J,4=3LQVC4W-H-2CL
; (5?VU:L,+6ELDO4TLKBU JTC=$9$C3CN$6 P0’4E35-: .LO $’5.HD3N41$;72)+KOU.3
7(A Y, TY .-VLM8Y3′?I7FRR-H+I5818G4"8KC.:29HQ"Y8FR’5!"GTE)NAMEK(H4RPJE3E
BU: B$MM:NL36VE)’9AA?I$+$GDZUD=D3/Y6M 1P) ?5XFK$(YO!8′(9=E’D.2R ?:F’"Y58
!C8,7TR5E-K-J9UK" X -"/PF9NL0DL,9C94OEWT 8$C-A(05)0X=.5(CHDF
END OF TEST FILE
For a PCS 1900 AMR speech traffic channel using a Typical Urban channel profile and a speed of the mobile station of 3.0 km/h [4, 5], the following character error rates – or lower values – have to be achieved:
No Frequency Hopping, Full Rate (TCH/AFS):
|
C/I |
AMR mode (kbit/s) |
|||||||
|
4.75 |
5.15 |
5.9 |
6.7 |
7.4 |
7.95 |
10.2 |
12.2 |
|
|
12 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.1 % |
0.1 % |
0.1 % |
0.1 % |
|
10 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
|
8 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
1.0 % |
|
6 dB |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
— |
— |
Ideal Frequency Hopping, Full Rate (TCH/AFS):
|
C/I |
AMR mode (kbit/s) |
|||||||
|
4.75 |
5.15 |
5.9 |
6.7 |
7.4 |
7.95 |
10.2 |
12.2 |
|
|
6 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.2 % |
0.2 % |
0.2 % |
0.2 % |
|
4 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
— |
— |
No Frequency Hopping, Half Rate (TCH/AHS):
|
C/I |
AMR mode (kbit/s) |
|||||
|
4.75 |
5.15 |
5.9 |
6.7 |
7.4 |
7.95 |
|
|
12 dB |
0.75 % |
0.75 % |
0.75 % |
0.75 % |
0.5 % |
0.5 % |
|
10 dB |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
1.5 % |
Ideal Frequency Hopping, Half Rate (TCH/AHS):
|
C/I |
AMR mode (kbit/s) |
|||||
|
4.75 |
5.15 |
5.9 |
6.7 |
7.4 |
7.95 |
|
|
10 dB |
0.5 % |
0.5 % |
0.5 % |
0.5 % |
0.2 % |
0.2 % |
For the PCS 1900 Full Rate speech traffic channel using a Typical Urban channel profile and a speed of the mobile station of 3.0 km/h [4, 5], the following character error rates – or lower values – have to be achieved:
No Frequency Hopping, Full Rate (TCH/FS):
|
C/I |
no frequency hopping |
ideal frequency hopping |
|
14 dB |
0.1 % |
0.1 % |
|
12 dB |
0.5 % |
0.2 % |
|
10 dB |
1.0 % |
0.2 % |
|
8 dB |
— |
0.5 % |
7.3 Test of the text telephone demodulator’s robustness against false detections
In this test case, the Baudot Code text telephone demodulator used in the test setup is tested against false detection of characters. In addition to this test, also the applicable parts of [3] shall be used for testing the Baudot Code demodulator’s performance. If the purpose of the test is only to verify a CTM implementation, this subclause can be ignored.
For this test, the test script test_false_detections is provided. It consists of the following sub‑tests:
1. Test of the response of the adaptation module for a signal that has one valid start bit (1800 Hz) and three valid information bits (1400 Hz). The duration of the fourth bit is too short so that this sequence must not trigger the Baudot demodulator of the adaptation module. Therefore, the original audio signal must be passed to the output without muting.
2. Test of the response of the adaptation module for a signal that has one valid start bit (1800 Hz) and five valid information bits (1400 Hz). The duration of the stop bit is too short so that no characters should be decoded. The output signal should be muted, because the start bit and the information bits were correct, but no CTM signals shall be generated.
3. Test of the response of the adaptation module for a signal that has one valid start bit (1800 Hz), five valid information bits (1400 Hz) and one valid stop bit. In this case the adaptation module shall decode the Baudot characters (9 times the character "Q") and generate the appropriate CTM tones.
4. Test to decode the CTM signal that has been generated in subtest #3 (see above). The CTM receiver shall decode the character "Q" nine times.
5. Try to feed the output signal from subtest #3 (see above) into a second Baudot detector. In this case the Baudot detector must not decode any character.
6. Test with a sine tone of 1400 Hz. In this case the signal adaptation module must remain passive, i.e. the original audio signal must be passed to the output without muting.
7. Test with a sine tone of 1800 Hz. In this case the signal adaptation module must remain passive, i.e. the original audio signal must be passed to the output without muting.
The following output shall be produced by this test script:
=========================================================
Performing Test #1 –> no characters shall be decoded now
=========================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
=========================================================
Performing Test #2 –> no characters shall be decoded now
=========================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
============================================================
Performing Test #3 –> string QQQQQQQQQ shall be decoded now
============================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
QQQQQQQQQ
============================================================
Performing Test #4 –> string QQQQQQQQQ shall be decoded now
============================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
QQQQQQQQQ
=========================================================
Performing Test #5 –> no characters shall be decoded now
=========================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
=========================================================
Performing Test #6 –> no characters shall be decoded now
=========================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
=========================================================
Performing Test #7 –> no characters shall be decoded now
=========================================================
********************************************************************
Cellular Text Telephone Modem (CTM) – Example Implementation for
Conversion between CTM and Baudot Code (use option -h for help)
********************************************************************
(No printable text generated)
7.4 Typing Mode
This test is based on a text telephone modem signal that has been generated at a typing speed that is extremely low in order to investigate the robustness of the CTM decoder’s synchronization.
In a first step, a software emulation of a text telephone terminal in Baudot mode has been used for generating a Baudot signal at a low typing speed. In a second step, the Baudot signal has been converted into a CTM signal by means of the signal adaptation module defined in [2]. Due to the low typing speed, the converted signal consists of a sequence of multiple CTM bursts. The pauses between adjacent CTM bursts contain passages of the original Baudot signal, which is a consequence of the capability of the signal adaptation module to alternate between text and voice.
The CTM signal carries the following text message, where the symbol # denotes a pause between two adjacent CTM bursts:
THE #CELLULAR #TEXT #TELEPHONE #MODEM #(#CTM)# #ALLOWS #RELIABLE
#TRANSMISSION #OF #A #TEXT #TELEPHONE #CONVERSATION #AL#TERNATING
#WITH #A #SPEECH #CONVERSATION #THROUGH #THE #EXISTING #SPEECH
#COMMUNICATION #PATHS #IN #CELLULAR #MOBILE #PHONE #S#YSTEMS.
#THIS #RELIABILITY #IS #ACHIEVED #BY #AN #IMPROVED #MODULATION
#TECHNIQUE#, #INCLUDING #ERROR #PROTECTION#, #INTERLEAVING #AND
#SYN#CHRONIZATION.
This CTM signal, which is provided in the file ctm_typingmode.pcm in the attached zip archive ctm_testing.zip, has to be transmitted via a the PCS 1900 AMR speech traffic channel (Typical Urban profile; MS speed 3.0 km/h), as it is described in subclause 7.2. After that, the received CTM signals shall be decoded using the CTM receiver that is integrated in the executable adaptation_switch (the source code of this executable is provided in [2]). The syntax how to call adaptation_switch is also described in subclause 7.2.
For the full-rate channel without frequency hopping, at a C/I of 12 dB, the starts and ends of all CTM bursts have to be detected properly. With ideal frequency hopping, the starts and ends of all CTM bursts have to be detected properly at a C/I of 6 dB for the full‑rate channel. For the half‑rate channel with ideal frequency hopping, no more than one start of a CTM burst shall be missed at a C/I of 10 dB
7.5 Test of the resynchonization
The CTM receiver has to be equipped resynchonization functionality, which allows to resume the synchronism of the received bit stream after a cell hand‑over. For this test, the PCM signal ctm_test_resync.pcm as well as the script test_resynchonization is provided in the zip archive ctm_testing.zip. The file ctm_test_resync.pcm provides a CTM signal, which has been modified by deleting and inserting samples in order to simulate the loss of synchonization after a cell hand‑over. The modifications are as follows:
|
Time instant (sample index) |
Event |
|
30000 |
10 samples deleted |
|
60000 |
50 samples deleted |
|
90000 |
130 samples deleted |
|
120000 |
240 samples deleted |
|
150000 |
10 samples inserted |
|
180000 |
50 samples inserted |
|
210000 |
130 samples inserted |
|
240000 |
240 samples inserted |
The original text reads as follows:
THE CELLULAR TEXT TELEPHONE MODEM (CTM) ALLOWS RELIABLE
TRANSMISSION OF A TEXT TELEPHONE CONVERSATION ALTERNATING
WITH A SPEECH CONVERSATION THROUGH THE EXISTING SPEECH
COMMUNICATION PATHS IN CELLULAR MOBILE PHONE SYSTEMS.
THIS RELIABILITY IS ACHIEVED BY AN IMPROVED MODULATION
TECHNIQUE, INCLUDING ERROR PROTECTION, INTERLEAVING AND
SYNCHRONIZATION.
Any implementation of a CTM receiver has to recover the synchonism after each of these events without loosing more than 10 characters. For the events at sample index 30000 and 150000, no loss of characters shall occur, because the period of 10 samples is much shorter than the CTM symbol length.
With the example implementation of the CTM receiver provided in [2], the following text has been generated (the ### symbols indicate at which time instants a resynchronization has become necessary):
THE CELLULAR TEXT TELEPHONE MODEM (CTM) ALLOWS RELIABLE
TRANSMISSION OF A T### TELEPHONE CONVERSATION ALTERNATINGM###3O0M A SPEECH CONVERSATION THROUGH THE6###QING SPEECH
COMMUNICATION PATHS IN CELLULAR MOBILE PHONE SYSTEMS.
THIS FL###OFITY IS ACHIEVED BY AN IMPROVED M.###ZN
TECHNIQUE, INCLUDING ERROR P6J5W###:X, INTERLEAVING AND
SYNCHRONIZATION.
Annex A (informative):
Change history
|
Change history |
|||||||
|
Date |
TSG # |
TSG Doc. |
CR |
Rev |
Subject/Comment |
Old |
New |
|
03-2001 |
11 |
SP-010092 |
Presented as version 2.0.0 for approval |
5.0.0 |
|||
|
09-2001 |
13 |
SP-010456 |
001 |
Request to change muting of transmitter from 5th info bit to 4th info bit at beginning of a TTY burst |
5.0.0 |
5.1.0 |
|
|
03-2002 |
15 |
SP-020084 |
002 |
Request to remove the CTM tandeming requirement for handsets in the Minimum Performance Requirements |
5.1.0 |
5.2.0 |
|
|
12-2004 |
26 |
Version for Release 6 |
5.2.0 |
6.0.0 |
|||
|
01-2005 |
TR changed to TS on cover page |
6.0.0 |
6.0.1 |
||||
|
01-2005 |
Correct the previous correction (oops) |
6.0.1 |
6.0.2 |
||||
|
06-2007 |
36 |
Version for Release 7 |
6.0.2 |
7.0.0 |
|||
|
12-2008 |
42 |
Version for Release 8 |
7.0.0 |
8.0.0 |
|||
|
12-2009 |
46 |
Version for Release 9 |
8.0.0 |
9.0.0 |
|||
|
03-2011 |
51 |
Version for Release 10 |
9.0.0 |
10.0.0 |
|||
|
09-2012 |
57 |
Version for Release 11 |
10.0.0 |
11.0.0 |
|||
|
09-2014 |
65 |
Version for Release 12 |
11.0.0 |
12.0.0 |
|||
|
12-2015 |
70 |
Version for Release 13 |
12.0.0 |
13.0.0 |
|||
|
Change history |
|||||||
|
Date |
Meeting |
TDoc |
CR |
Rev |
Cat |
Subject/Comment |
New version |
|
2017-03 |
75 |
Version for Release 14 |
14.0.0 |
||||
|
2018-06 |
80 |
Version for Release 15 |
15.0.0 |
||||
|
2020-07 |
– |
– |
– |
– |
– |
Update to Rel-16 version (MCC) |
16.0.0 |
|
2022-04 |
– |
– |
– |
– |
– |
Update to Rel-17 version (MCC) |
17.0.0 |