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V.34 Modem Software

V-34 Soft ModemV.34 Modem software provides a real-time implementation that can be configured to support high speed multi-channel applications. Our V.34 modem software implements ITU-T V.34 which defines the modulation methods and operating sequences for a high speed modem used on General Switched Telephone Networks (GSTNs) and on point-to-point 2-wire leased telephone-type circuits. Contact us to discuss your V.34 modem application requirements.

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Virtual Modem over IP

VOCAL’s SIP Software modem (MoIP or V.MoIP) solution provides developers a range of solutions to connect legacy dial up modems to modem infrastructure. Unlike other virtual modem designs, the SIP software modem can communicate with a physical modem at the far end using a VoIP service over an IP network.



VOCAL’s V.34 modem software is optimized for performance on leading DSP architectures and processors from TI, Intel, ADI, AMD and other vendors. The software library is modular and can be executed as a single task under a variety of operating systems or standalone with its own microkernel. Our modem software  may be licensed as a library or complete design with custom solutions available.

V.34 Features

  • Fully compliant with ITU V.34 recommendations
  • Supports 14 data rates from 2400 bps and 33600 bps in increments of 2400 bps
  • Modem MIB support (RFC 1696)
  • Advanced line probing analysis automatically determines maximum channel capacity
  • Symbol rates for 2400, 2743, 2800, 3000, 3200, and 3429 symbols per second
  • 200 bps auxiliary channel
  • Asymmetric symbol and data rates
  • MSE fallback/fallforward threshold control to adjust tradeoff between higher data channel rates andsymbol error rates
  • Multichannel implementation
  • Multi-tasking environment compatible
  • Optimized for performance on leading DSP architectures

V.34 SoftModem

VOCAL’s V.34 softmodem uses state-of-the-art line probing analysis to automatically determine maximum channel capacity. It also supports MSE fallback/fallforward threshold control to adjust the tradeoff between higher data channel rates and symbol error rates. V.34 channel separation is accomplished using echo cancellation techniques.

The V.34 softmodem uses Quadrature Amplitude Modulation (QAM) with synchronous line transmission to support selectable mandatory rates of 2400, 3000, and 3200 symbols/s and optional rates of 2743, 2800 and 3429 symbols/s. Asymmetric symbol and data rates are also supported. Negotiation and training sequences at startup establish the data rate. V.34 control channel rates are 1200 and 2400 bps, with an optional auxiliary channel with a synchronous data signalling rate of 200 bit/s. Adaptive techniques are used to achieve close to the maximum data signaling rate that a channel can support on each connection.

The V.34 softmodem line interface may be an analog front end (codec and DAA) or a digital interface such as T1/E1, Switched 56, and ISDN. The upper end of this software can provide a PPP, HDLC, V.14 or a direct binary framing layer. With V.34, higher data protocol layers, V.42 (including MNP 2-4), V.44, V.42bis and MNP 5, are also available.

The V.34 modulation family can be combined with other data modulations (V.92, V.90, V.32bis/V.32, and V.22bis/ V.22/V.23 V.21). Automatic modulation determination procedures (Automode) include those of V.8, V.8bis and PN-2330. All V.34 modulation software is fully compatible with VOCAL’s facsimile, telephony, speech coder and multimedia systems.

V.34 Block Diagram

Block diagram for V.34 Soft Modem Design VOCAL’s V.34 modem software design supports high speed multi-channel applications


  • DAA interface using linear codec at 9.6 kHz, 8.0 kHz, or 16.0 kHz sample rate
  • Direct interface to 8.0 kHz PCM data stream (A-law or μ-law)
  • PPP (RFC 1662), HDLC, V.14 and direct binary framing layer
  • North American and International Dialing/Telephony dialing functions available
  • DTMF detection during voice modes available
  • Data protocol layer (V.42/MNP 2-4/V.44/V.42bis/MNP 5) available
  • VOCAL’s Overall Modem Controller (OMC) Layer provides coordinated data modulation / data protocol operation relative to V.34 startup, shutdown, modulation retrains and modulation renegotiations.
  • System can be combined with V.110 rate adaptation software.
  • System can be combined with other modulations (V.92, V.90, V.32bis, et al.) and automode procedures (V.8bis, V.8 and PN-2330).
  • Data/Facsimile/Voice Distinction upon startup is available. Complete facsimile systems, modulations (V.34 fax, V.17, et al.) and protocols (T.30), and speech coders available.



VOCAL’s optimized modem software is available for the following platforms. Please contact us for specific V.34 supported platforms.

Processors Operating Systems
  • Texas Instruments – C6000 (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5000 (TMS320C54x, TMS320C55x)
  • Analog Devices – Blackfin, ADSP-21xx, TigerSHARC, SHARC
  • PowerPC
  • MIPS – MIPS32, MIPS64, MIPS4Kc
  • ARM – ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, ARM Cortex-A8, Cortex-M1
  • Intel / AMD – x86, x64 (both 32 and 64 bit modes)
  • Google Android
  • Apple iOS / iPhone / iPad & MacOS
  • Unix,  Linux, μClinux, BSD
  • Microsoft Windows ACM / RTC / CE / Mobile
  • Symbian
  • eCOS / eCOSPro
  • Wind River VxWorks
  • Green Hills Integrity
  • Micrium μCOS


VOCAL Technologies, Ltd.
520 Lee Entrance, Suite 202
Amherst New York 14228
Phone: +1-716-688-4675
Fax: +1-716-639-0713