Site Map
| Data Modulations |
|---|
| V.92 |
| V.90 |
| 56K |
| V.34 |
| V.32bis/V.32 |
| V.22bis/V.22 |
| V.23/V.21/Bell 212/Bell 103 |
VOCAL offers a comprehensive and fully optimized data modem solution for a wide variety of platforms. A modulation family can be combined with other data modulations (V.92, V.90, V.34, 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 data modulation software is fully compatible with VOCAL's facsimile, telephony, speech coder and multimedia systems.
The 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. Higher data protocol layers, V.42 (including MNP 2-4), V.44, V.42bis and MNP 5, are options as well.
VOCAL's embedded software libraries include a complete range of ETSI / ITU / IEEE compliant algorithms, in addition to many other standard and proprietary algorithms. Our software is optimized for execution on ANSI C and leading DSP architectures (TI, ADI, AMD, ARM, MIPS, CEVA, LSI Logic ZSP, etc.). These libraries are modular and can be executed as a single task under a variety of operating systems or standalone with its own microkernel.
V.92 is an ITU dial-up modem standard that provides for an increase in upload speeds (PCM upstream or PCMU), quicker connect times (Quick Connect or QC), and a Modem-On-Hold (MOH) feature that allows the modem to work in conjunction with call waiting provided by the phone company.
V.92 specification allows a PCM upstream at rate from 24,000bps to 48,000bps. The rate increments in steps of 1.33 kbps as in V.90. Upstream rates could be 24k, 25.3k, 26.6k, 28k, etc. This is a 30% increase over the 33.6K bps attainable by V.90 modems. This higher upstream speed offers numerous benefits including a reduction in the upstream data transfer time for large e-mails with attachments and for ftp site uploads, as well as improved operation for interactive applications. Due to the real conditions of the phone lines the 48 kbps upstream is very hard to obtain.
Allows modems to stay connected "on-hold" while you take an incoming call waiting call, or initiate an outgoing voice call (works only if V.92 server modem is configured to allow this feature). The amount of time you can place your Internet connection on hold while taking another call will be up to your Internet Service Provider (ISP).The V.92 recommendation permits ISPs to set their modems to wait for 0 to 16 minutes, or, to wait indefinitely. V.92 client modems may include software that will warn the user when the ISP determined timeout approaches, as well as to display call waiting caller ID info (requires telco call waiting/caller ID service). ISPs have an incentive to limit the use of this feature: when a call is placed on hold, the ISP modem remains unavailable to take other calls. The ISP may need to add more modems to maintain quality of service if this feature is enabled. The ISPs also have the posibility of do not accept modem-on-hold if the total time of modem-on-hold in the same session is greater that a determined value.
In the ITU V.92 recommendation the time to establish a connection may be reduced with faster handshaking, using a short phase 1 and phase 2, reducing the connection time to about 20 seconds. It is also possible to reduce more this connedction time to around 10 seconds using short phase 3 and phase 4 (this feature is not in the ITU V.92 recommendatin) by forcing V.92 modems to remember line conditions and connect rates on past connections by storing data about those connections in a buffer. The modem will compare line quality variables as it dials in to a server modem with those in the buffer, and if a match is found, the handshake starts at the rate previously negotiated. Quick Connect will also be used with Modem On Hold: when a call is switched back to the modem after using the MOH feature, a retrain is required. When the V92 modem uses short phase 3 and phase 4 and the line conditions are different, the V.92 modem have to fall-back to a full retrain.
Depending upon V.90 configuration selected, the 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 PPP, V.14, HDLC or direct binary framing layers. Higher data protocol layers, V.42 (including MNP 2-4), V.44, V.42bis and MNP 5 are options as well.
Figure 1 shows VOCAL's V.90 block diagram.
ITU-T V.34 defines the modulation methods and operating sequences for a modem used on General Switched Telephone Networks (GSTNs) and on point-to-point 2-wire leased telephone-type circuits. Both full duplex and half-duplex modes are supported. Data rates in the range of 2400 bps to 33600 bps, in incremental steps of 2400 bps are supported. Symbol rates of 2400, 2743, 2800, 3000, 3200, and 3429 symbols per second are supported. Using Quadrature Amplitude Modulation (QAM) with synchronous line transmission, selectable mandatory rates are 2400, 3000, and 3200 symbols/s with 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. Control channel rates are 1200 and 2400 bps, with an optional auxiliary channel with a synchronous data signalling rate of 200 bit/s.
Trellis coding for all data signaling rates and shell mapping permit satisfactory performance even over noisy channels. Adaptive techniques enable the modem to achieve close to the maximum data signalling rate a channel can support on each connection. VOCAL's V.34 software uses state-of-the-art line probing analysis to automatically determine maximum channel capacity. It also support MSE fallback/fallforward threshold control to adjust the tradeoff between higher data channel rates and symbol error rates. Channel separation is accomplished using echo cancellation techniques.
The 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. Higher data protocol layers, V.42 (including MNP 2-4), V.44, V.42bis and MNP 5, are options as well.
This modulation family can be combined with other data modulations (V.92, V.90, V.34, V.22bis/V.22/ V.23/V.21). Automatic modulation detection procedures (Automode) include those of PN-2330, V.8 and V.8bis. All data modulation software is fully compatible with VOCAL's facsimile, telephony, speech coder and multimedia systems.
The 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. Higher data protocol layers, V.42 (including MNP 2-4), V.44, V.42bis and MNP 5, are options as well.
This modulation family can be combined with other data modulations (V.92, V.90, V.34, V.32bis/V.32). Automatic modulation detection procedures (Automode) include those of PN-2330, V.8 and V.8bis. All data modulation software is fully compatible with VOCAL's facsimile, telephony, speech coder and multimedia systems.