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.