v.34 & v.8 Explained
I. Description of v.8 and v.34
v.8
- Allows GSTN equipment to identify data equipment (Echo Canceling, V.25)
- Allows modems (and other data communication equipment) to handshake quickly.
- Allows data calls to be passed to DCE(Data Communication Equipment) automatically.
(similar to CNG tones and faxing)
- Uses 300 bps, V.21 modulation to transmit CI, CM, and JM.
v.34
- ITU-T recommendation for 2400 through 28800 bps.
- Multiple symbol rates
- 2 carriers, one selectable, except at 3429 symbol rate.
- Other features for optimum throughput for line conditions
- 200 bps, auxiliary data channel
II. Terms related to v.8 and v.34
v.8
- CI Call indicate * optional
- ANSam Modified Answer Tone
- CM Call Menu - Modulation, Protocol, GSTN
- JM Joint Menu
- S54=128 Disable v.8
- S54=64 Disable CI
v.34
- Negotiation
- Symbol rates
- ATI11
- ATY11
- S Registers S54 - S57
ATI11
USRobotics Courier HST Dual Standard V.34 Fax Link Diagnostics.
|
Modulation |
V.34 |
|
Carrier Freq (Hz) |
1920/1920 |
|
Symbol Rate |
3200/3200 |
|
Trellis Code |
32S-2D/32S-2D |
|
Nonlinear Encoding |
OFF |
|
Precoding |
ON |
|
Shaping |
OFF |
|
Preemphasis (-dB) |
3/3 |
|
Recv/Xmit Level (-dB) |
7/8 |
|
Roundtrip Delay (msec) |
2 |
ATY11
|
Freq |
Level |
|
1000 |
22 |
|
3000 |
25 |
|
3300 |
25 |
|
3350 |
27 |
|
3450 |
31 |
|
3600 |
37 |
S54 Bit Mapped
|
1 |
= |
Disable 2400 symbol rate |
|
2 |
= |
Disable 2743 symbol rate |
|
4 |
= |
Disable 2800 symbol rate |
|
8 |
= |
Disable 3000 symbol rate |
|
16 |
= |
Disable 3200 symbol rate |
|
32 |
= |
Disable 3429 symbol rate |
|
64 |
= |
Disable Call Indicate |
|
128 |
= |
Disable v.8 Mode |
S55 Bit Mapped
|
1 |
= |
Disable 8S-2D trellis code |
|
2 |
= |
Disable 16S-4D trellis code |
|
4 |
= |
Disable 32S-2D trellis code |
|
8 |
= |
Disable 64S-4D trellis code |
|
16 |
= |
Reserved |
|
32 |
= |
Reserved |
|
64 |
= |
Reserved |
|
128 |
= |
Reserved |
S56 Bit Mapped
|
1 |
= |
Disable Non linear coding |
|
2 |
= |
Disable TX level deviation |
|
4 |
= |
Disable Pre-emphasis |
|
8 |
= |
Disable Pre-coding |
|
16 |
= |
Disable Shaping |
|
32 |
= |
Reserved |
|
64 |
= |
Disable V.34 |
|
128 |
= |
Disable V.FC |
|
GSTN |
General Switched Telephone Network (PSTN) |
|
Bandwidth |
The difference, expressed in hertz, between two limited frequencies of a band. |
|
Throughput |
Effective data transmission rate over time, usually expressed in bits per second. |
|
Constellation |
Quadrature Amplitude Modulation bit mapping diagram. |
|
QAM |
Quadrature Amplitude Modulation - modulating or changing an analog by adjusting its amplitude, and its phase. |
|
Carrier |
An analog signal which carriers no information, but is used as a reference point. |
|
Symbol Rate |
Number of symbols represented over a given period of time. A symbol is an analog sample which represents a given number of data bits. |
|
TCM |
Trellis Coded Modulation. A special method of QAM which allows for many invalid bit combinations, therefore making error detecting easier. |
|
Non Linear Encoding |
A method for improving distortion immunity near the perimeter of a signal constellation by introducing a non-uniform two dimensional signal point spacing. |
|
Precoding |
Pre-coding is a non-linear equalization method for reducing equalizer noise enhanced caused by amplitude distortion. Equalization is performed at the transmitter using pre-coding coefficients provided by the remote modem. Certain parts of the bandwidth can be boosted to accommodate roll off and other drops in amplitude. Analogous to a graphic equalizer on a stereo. |
|
Shaping |
A method for improving noise immunity by introducing a non-uniform two dimensional probability distribution for transmitted signal points. The degree of constellation shaping is a function of the amount of constellation expansion. Essentially, the QAM constellation is modified to accommodate noise. |
|
Preemphasis |
A linear equalization method where the transmit signal spectrum is shaped to compensate for amplitude distortion. The pre-emphasis filter is selected using a filter index provided by the remote modem. The analog signal is boosted linearly to accommodate a weak signal. |
|
TX Level Deviation |
The transmit level can be automatically adjusted to accommodate the telephone lines. If you turn it off, the modem may think the lines are better than they are. |
III. V.34 INFORMATION CHART
|
Symbol Rate |
Min Bit Rate |
Max Bit Rt |
Carrier Frq.** |
Bandwidth Req. |
|
|
|
|
|
|
|
|
|
|
|
2400 |
2400 |
21600 |
1600 |
400-2800 |
|
|
|
1800 |
600-3000 |
|
|
|
|
|
|
|
|
|
|
|
2743* |
4800 |
24000 |
1646 |
274-3018 |
|
|
|
1829 |
457-3200 |
|
|
|
|
|
|
|
|
|
|
|
2800* |
4800 |
24000 |
1680 |
280-3080 |
|
|
|
1867 |
467-3267 |
|
|
|
|
|
|
|
|
|
|
|
3000 |
4800 |
26400 |
1800 |
300-3300 |
| |
|
|
2000 |
500-3500 |
|
|
|
|
|
|
|
|
|
|
|
3200 |
4800 |
28800 |
1829 |
229-3429 |
|
|
|
1920 |
320-3520 |
|
|
|
|
|
|
|
|
|
|
|
3429* |
4800 |
28000 |
1959 |
244-3674 |
| ^ | Optional symbol rates under the V.34 specification. We implement all of the optional symbol rates. |
|
** |
Each symbol rate supports two carrier frequencies and two bandwidth ranges. During negotiation, the modems will decide which to use. |