Modems: Call of the Dialled

As more and more punters make the connection and surf the Net, modems are going to be more in demand than ever. And new technologies such as DSVD will give the market a helping hand. Roger Gann reports

It is estimated that 10 million people worldwide will surf the internet for the first time this year. Some will use a commercial service like Compuserve or AOL, others will take a more direct route with internet access providers such as Demon, Uunet or Netcom. Either way, they?ll almost certainly need a modem. In 1997 the modem market is set to take off again, thanks to the Net and new facilities such as DSVD.

The prevailing modem standard, the International Telecommunications Union (ITU) V.34 spec, provides data transfer rates of up to 28.8Kbps. A newer, enhanced version of the standard, sometimes called V.34+, accelerates modems to 33.6Kbps. V.34+ uses the same encoding system as, and is compatible with, V.34, but it manages to pack more constellation points on to the data-graphing system that V.34 uses to push through data on a line with limited bandwidth.

These fast modems have fallen dramatically in price over the past year ? it?s now possible to pick up a fully featured 33.6Kbps modem for under #100 ? modems have never been more affordable.

You?ll usually see the lowest prices on ISA-card internal modem cards because they don?t require the housing, serial cables, or mains transformers that external modems do. Internal modems are a good choice if desk space and budgets are tight, but external modems can be easier to set up ? you don?t need to open your PC case or deal with possible IRQ conflicts between boards, and you can move the modem from one PC to another easily.

External models also offer indicator lights and sometimes LCD displays that tell you what?s going on during a connection (at least after you?ve read the manual to decipher what the lights mean). Whether you favour an internal or external desktop modem, it?s definitely worth the extra cash to get a 33.6Kbps model, unless you know you?re operating with older or relatively poor-quality phone lines.

Virtually all modems nowadays support PC fax and data functions, letting you receive faxes and send electronic documents (or paper ones you?ve imported with a scanner) from your desktop. Most current models support fax send-and-receive speeds of up to 14.4Kbps, which can save time compared with the generic Group III fax rate of 9.6Kbps. Note, however, that not all fax machines support 14.4Kbps operation, so the extra speed is more likely to come in handy if you?re sending faxes to another fax modem.

For some years now, all popular modems have had a faxing capacity, that is the ability to send and receive faxes. Just recently, voice telephony has started to become a standard feature. This originally began as straight voicemail, allowing your modem and PC to act as a relatively sophisticated voicemail system, offering advanced features like multiple voice-mailboxes, message forwarding, page support full-duplex speakerphone, and caller ID recognition. The latter can be tied to address-book or contact-manager software, so information about the caller can be displayed on screen as a call comes in.

All this has been taken a stage further with the advent of digital simultaneous voice and data, or DSVD. DSVD permits both data transfers and voice conversations to occur simultaneously on the same line. DSVD isn?t exactly new, but the technology has only recently become cheap enough to be introduced into mainstream modems. Today, there are more than a dozen DSVD modems available, including Hayes? Accura 288 DSVD and US Robotics? Sportster Vi.

The trouble is, until recently, many of these DSVD modems couldn?t talk to each other. Nearly all were developed before the ITU?s recent adoption of an official standard for DSVD. This protocol, known as V.70, splits the phone line?s bandwidth, setting aside 8Kbps for voice and the rest for data. Most modem makers ? including IBM, Lucent, and Motorola ? have pledged to support V.70 in new modems.

But who would want to talk and transfer data at the same time? Gamesters, that?s who. Many game junkies want the ability to talk to, or to be more accurate, taunt, their opponents as they fight them in bloodthirsty games such as Duke Nukem 3D and Quake. DSVD has serious applications, too, with whiteboarding or document-conferencing application, such as Intel?s Proshare.

Just before Christmas, Diamond Multimedia released one of the cheapest 33.6Kbps modems on the market, the A390 Supra Express 336e V+. As well as supporting the usual data/ fax/voice functions, this low-cost modem supports the analogue version of DSVD ? ASVD ? which is unique at this price.

Designed in the early 1980s as a digital replacement for analogue telephone service, ISDN (integrated services digital network) connects your home or office to the telephone company?s central office switch using a single pair of wires ? the same sort of connection you?d see on a PSTN (public switch telephone network). It?s easy to do and doesn?t cost (BT) much to install ? you?d think everybody would have ISDN by now.

Think again. BT?s reluctant marketing of ISDN ? charging excessive installation fees, for example ? has puzzled many observers, and as a result its uptake in the UK has been faltering to say the least. But the telco is making amends and is now pushing ISDN hard.

ISDN is, of course, digital and so doesn?t need a modem per se ? the equivalent device is a terminal adaptor (TA). Luckily a TA not only looks like a modem, it can also be treated by comms software as though it is a modem, so installing a TA needn?t be any more fraught than plugging in a modem.

Prices of TAs have dropped substantially and some can be picked up for less than #100. These are usually internal cards that make a PPP network-like connection to an internet access provider.

Promoted almost to death by US Robotics, Lucent Technologies and Rockwell Semiconductor Systems since the autumn of 1996, 56K modems, which can transmit data at 56Kbps over ordinary phone lines, can be considered the modem?s last stand. The attraction is obvious: though offering only about half the full speed of ISDN, 56Kbps modems have the potential for rapid rollout (unlike ISDN) and don?t require an expensive digital phone line.

There?s certainly quite a buzz about 56Kbps modems. There is a downside to 56Kbps, of course. It?s asymmetric ? meaning it?s 56Kbps in one direction (receiving) and 33.6Kbps (send- ing) in the other ? making it less useful for things like video conferencing. You?ll still need a good-quality phone line, and you will have to be within a mile or two of a digital exchange, which means that some rural areas won?t ever see 56Kbps. It has to be a direct connection, too ? if there?s a switchboard in the way, it won?t work.

Your internet access provider also needs to support 56Kbps (obviously) and must have a digital connection to the internet. Worst of all is the fact that, at the moment, all 56Kbps solutions are proprietary and an ITU 56K standard isn?t expected before 1998. But the core network infrastructure is largely in place for 56Kbps service, which looks to diminish the appeal of ISDN for data services over the next 10 years.

Previous telecoms theory (Shannon?s Law) posited that the maximum throughput achievable over ordinary PSTN lines was 35Kbps or less. So how is 56Kbps achieved? The PSTN has increasingly turned from an analogue to a digital network. Analogue modems, such as V.34, view the PSTN as an analogue system, even though the signals are digitised for communications throughout most of the network.

According to Rockwell, 56Kbps technology treats the PSTN as a digital network that happens to have an ?impaired? section in the communications path ? the analogue local loop ? between the exchange and the user. In simple terms, a 56Kbps modem establishes a pseudo-digital link over the final, analogue section of the connection.

At the moment, the battle over the 56Kbps standard seems to have crystallised into a war of words between US Robotics (with its X2 standard) and the rest of the modem world and the 56Kflex standard. But both sides have indicated that a common 56Kbps standard will eventually emerge and that early adopters will be able to upgrade their modems using software. For example, the best selling USR Sportster Flash, billed as ?X2-ready?, uses flash memory to hold the 56Kb firmware, so this modem will be easy to upgrade. However, until the dust has settled, I suspect many users will hold off from buying 56Kbps modems, and with some justification.

So far, the promises made in respect of cable modems have failed to materialise. Cable companies boast of the 27Mbps throughput available across the cable infrastructure, but they gloss over the costs needed to make their systems bi-directional or to route the data onward. Installing cable modems has been a tricky affair, which doesn?t help much either. Nevertheless, so-called cable modems show great promise.

There are a number of other digital solutions (ADSL, xDSL) that use the existing phone infrastructure to deliver fabulous bandwidth. Digital subscriber line (DSL) and cable modems are technologically very different but conceptually similar. Both provide dedicated multi-megabit connections, so your service is always on.

In essence, DSL operates as a high-speed leased line over copper wiring and can reach speeds of up to 8Mbps, (just 1.5 Mbps with ADSL) ? not as fast as the cable camp claims for its technology but still light-years ahead of 33.6Kbps modems. Some flavours of DSL are faster ? the very-high-speed digital subscriber line (xDSL) can reach a theoretical speed of 51Mbps, but only over short distances. As with cable modems, large-scale implementation of DSL will require a substantial investment from the telcos.

Hoping to take over a market sector now dominated by dedicated DSP chips from Rockwell, IBM, AT&T, and others, Motorola and General Magic have independently announced soft-modem initiatives.

Motorola intends to eliminate the modem as a separate peripheral in both desktop and mobile PCs, while General Magic is focusing on embedded applications and consumer devices ? its first design win is Philips? Velo, a Windows CE handheld PC.

The rationale of soft modems is simple: processor power increases with time, but the complexity of modem algorithms has hit a wall and won?t become any more complex; conventional phone lines have a limited frequency response and signal-to-noise ratio, which fixes the available bandwidth at under 35Kbps.

With modern conventional modems down to just a few chips, it becomes reasonable to think about performing the digital operations on the system?s existing host processor. The same analogue interface components can be used in this configuration. Although a significant percentage of typical host processor performance is required to implement a software modem today, this percentage will rapidly decline.

Unfortunately, existing processors still lack sufficient power to handle soft modems effortlessly. The Pentium wasn?t designed for signal-processing tasks, so such algorithms absorb a lot of crunching power ? as much as 28 per cent for 28.8Kbps modems. Apple has been shipping host-based modem products for a number of years, but the Geoport Express didn?t prove populaIt is estimated that 10 million people worldwide will surf the internet for the first time this year. Some will use a commercial service like Compuserve or AOL, others will take a more direct route with internet access providers such as Demon, Uunet or Netcom. Either way, they?ll almost certainly need a modem. In 1997 the modem market is set to take off again, thanks to the Net and new facilities such as DSVD.

The prevailing modem standard, the International Telecommunications Union (ITU) V.34 spec, provides data transfer rates of up to 28.8Kbps. A newer, enhanced version of the standard, sometimes called V.34+, accelerates modems to 33.6Kbps. V.34+ uses the same encoding system as, and is compatible with, V.34, but it manages to pack more constellation points on to the data-graphing system that V.34 uses to push through data on a line with limited bandwidth.

These fast modems have fallen dramatically in price over the past year ? it?s now possible to pick up a fully featured 33.6Kbps modem for under #100 ? modems have never been more affordable.

You?ll usually see the lowest prices on ISA-card internal modem cards because they don?t require the housing, serial cables, or mains transformers that external modems do. Internal modems are a good choice if desk space and budgets are tight, but external modems can be easier to set up ? you don?t need to open your PC case or deal with possible IRQ conflicts between boards, and you can move the modem from one PC to another easily.

External models also offer indicator lights and sometimes LCD displays that tell you what?s going on during a connection (at least after you?ve read the manual to decipher what the lights mean). Whether you favour an internal or external desktop modem, it?s definitely worth the extra cash to get a 33.6Kbps model, unless you know you?re operating with older or relatively poor-quality phone lines.

Virtually all modems nowadays support PC fax and data functions, letting you receive faxes and send electronic documents (or paper ones you?ve imported with a scanner) from your desktop. Most current models support fax send-and-receive speeds of up to 14.4Kbps, which can save time compared with the generic Group III fax rate of 9.6Kbps. Note, however, that not all fax machines support 14.4Kbps operation, so the extra speed is more likely to come in handy if you?re sending faxes to another fax modem.

For some years now, all popular modems have had a faxing capacity, that is the ability to send and receive faxes. Just recently, voice telephony has started to become a standard feature. This originally began as straight voicemail, allowing your modem and PC to act as a relatively sophisticated voicemail system, offering advanced features like multiple voice-mailboxes, message forwarding, page support full-duplex speakerphone, and caller ID recognition. The latter can be tied to address-book or contact-manager software, so information about the caller can be displayed on screen as a call comes in.

All this has been taken a stage further with the advent of digital simultaneous voice and data, or DSVD. DSVD permits both data transfers and voice conversations to occur simultaneously on the same line. DSVD isn?t exactly new, but the technology has only recently become cheap enough to be introduced into mainstream modems. Today, there are more than a dozen DSVD modems available, including Hayes? Accura 288 DSVD and US Robotics? Sportster Vi.

The trouble is, until recently, many of these DSVD modems couldn?t talk to each other. Nearly all were developed before the ITU?s recent adoption of an official standard for DSVD. This protocol, known as V.70, splits the phone line?s bandwidth, setting aside 8Kbps for voice and the rest for data. Most modem makers ? including IBM, Lucent, and Motorola ? have pledged to support V.70 in new modems.

But who would want to talk and transfer data at the same time? Gamesters, that?s who. Many game junkies want the ability to talk to, or to be more accurate, taunt, their opponents as they fight them in bloodthirsty games such as Duke Nukem 3D and Quake. DSVD has serious applications, too, with whiteboarding or document-conferencing application, such as Intel?s Proshare.

Just before Christmas, Diamond Multimedia released one of the cheapest 33.6Kbps modems on the market, the A390 Supra Express 336e V+. As well as supporting the usual data/ fax/voice functions, this low-cost modem supports the analogue version of DSVD ? ASVD ? which is unique at this price.

Designed in the early 1980s as a digital replacement for analogue telephone service, ISDN (integrated services digital network) connects your home or office to the telephone company?s central office switch using a single pair of wires ? the same sort of connection you?d see on a PSTN (public switch telephone network). It?s easy to do and doesn?t cost (BT) much to install ? you?d think everybody would have ISDN by now.

Think again. BT?s reluctant marketing of ISDN ? charging excessive installation fees, for example ? has puzzled many observers, and as a result its uptake in the UK has been faltering to say the least. But the telco is making amends and is now pushing ISDN hard.

ISDN is, of course, digital and so doesn?t need a modem per se ? the equivalent device is a terminal adaptor (TA). Luckily a TA not only looks like a modem, it can also be treated by comms software as though it is a modem, so installing a TA needn?t be any more fraught than plugging in a modem.

Prices of TAs have dropped substantially and some can be picked up for less than #100. These are usually internal cards that make a PPP network-like connection to an internet access provider.

Promoted almost to death by US Robotics, Lucent Technologies and Rockwell Semiconductor Systems since the autumn of 1996, 56K modems, which can transmit data at 56Kbps over ordinary phone lines, can be considered the modem?s last stand. The attraction is obvious: though offering only about half the full speed of ISDN, 56Kbps modems have the potential for rapid rollout (unlike ISDN) and don?t require an expensive digital phone line.

There?s certainly quite a buzz about 56Kbps modems. There is a downside to 56Kbps, of course. It?s asymmetric ? meaning it?s 56Kbps in one direction (receiving) and 33.6Kbps (send- ing) in the other ? making it less useful for things like video conferencing. You?ll still need a good-quality phone line, and you will have to be within a mile or two of a digital exchange, which means that some rural areas won?t ever see 56Kbps. It has to be a direct connection, too ? if there?s a switchboard in the way, it won?t work.

Your internet access provider also needs to support 56Kbps (obviously) and must have a digital connection to the internet. Worst of all is the fact that, at the moment, all 56Kbps solutions are proprietary and an ITU 56K standard isn?t expected before 1998. But the core network infrastructure is largely in place for 56Kbps service, which looks to diminish the appeal of ISDN for data services over the next 10 years.

Previous telecoms theory (Shannon?s Law) posited that the maximum throughput achievable over ordinary PSTN lines was 35Kbps or less. So how is 56Kbps achieved? The PSTN has increasingly turned from an analogue to a digital network. Analogue modems, such as V.34, view the PSTN as an analogue system, even though the signals are digitised for communications throughout most of the network.

According to Rockwell, 56Kbps technology treats the PSTN as a digital network that happens to have an ?impaired? section in the communications path ? the analogue local loop ? between the exchange and the user. In simple terms, a 56Kbps modem establishes a pseudo-digital link over the final, analogue section of the connection.

At the moment, the battle over the 56Kbps standard seems to have crystallised into a war of words between US Robotics (with its X2 standard) and the rest of the modem world and the 56Kflex standard. But both sides have indicated that a common 56Kbps standard will eventually emerge and that early adopters will be able to upgrade their modems using software. For example, the best selling USR Sportster Flash, billed as ?X2-ready?, uses flash memory to hold the 56Kb firmware, so this modem will be easy to upgrade. However, until the dust has settled, I suspect many users will hold off from buying 56Kbps modems, and with some justification.

So far, the promises made in respect of cable modems have failed to materialise. Cable companies boast of the 27Mbps throughput available across the cable infrastructure, but they gloss over the costs needed to make their systems bi-directional or to route the data onward. Installing cable modems has been a tricky affair, which doesn?t help much either. Nevertheless, so-called cable modems show great promise.

There are a number of other digital solutions (ADSL, xDSL) that use the existing phone infrastructure to deliver fabulous bandwidth. Digital subscriber line (DSL) and cable modems are technologically very different but conceptually similar. Both provide dedicated multi-megabit connections, so your service is always on.

In essence, DSL operates as a high-speed leased line over copper wiring and can reach speeds of up to 8Mbps, (just 1.5 Mbps with ADSL) ? not as fast as the cable camp claims for its technology but still light-years ahead of 33.6Kbps modems. Some flavours of DSL are faster ? the very-high-speed digital subscriber line (xDSL) can reach a theoretical speed of 51Mbps, but only over short distances. As with cable modems, large-scale implementation of DSL will require a substantial investment from the telcos.

Hoping to take over a market sector now dominated by dedicated DSP chips from Rockwell, IBM, AT&T, and others, Motorola and General Magic have independently announced soft-modem initiatives.

Motorola intends to eliminate the modem as a separate peripheral in both desktop and mobile PCs, while General Magic is focusing on embedded applications and consumer devices ? its first design win is Philips? Velo, a Windows CE handheld PC.

The rationale of soft modems is simple: processor power increases with time, but the complexity of modem algorithms has hit a wall and won?t become any more complex; conventional phone lines have a limited frequency response and signal-to-noise ratio, which fixes the available bandwidth at under 35Kbps.

With modern conventional modems down to just a few chips, it becomes reasonable to think about performing the digital operations on the system?s existing host processor. The same analogue interface components can be used in this configuration. Although a significant percentage of typical host processor performance is required to implement a software modem today, this percentage will rapidly decline.

Unfortunately, existing processors still lack sufficient power to handle soft modems effortlessly. The Pentium wasn?t designed for signal-processing tasks, so such algorithms absorb a lot of crunching power ? as much as 28 per cent for 28.8Kbps modems. Apple has been shipping host-based modem products for a number of years, but the Geoport Express didn?t prove popular. For example, the same code that requires 43 per cent of a P150 needs only 23 per cent of a P200 with MMX. With future P6-class processors at 300MHz and above, CPU use will drop to less than 10 per cent.

But other problems remain. Windows 95 isn?t designed to handle real-time signal processing and we?ll have to wait for the release of the Win32 Driver Model (WDM) in an effort to control as many of these problems as possible.

For example, the same code that requires 43 per cent of a P150 needs only 23 per cent of a P200 with MMX. With future P6-class processors at 300MHz and above, CPU use will drop to less than 10 per cent.

But other problems remain. Windows 95 isn?t designed to handle real-time signal processing and we?ll have to wait for the release of the Win32 Driver Model (WDM) in an effort to control as many of these problems as possible.