U. Glaeser

PC as a Terminal (Modem)
The PC is the second most successful telecom terminal of all times. For that it requires a modem (most
advanced voiceband modem is V90). The modem was the application that created a mass market for
DSP devices (1982–1992). Today, all DSP devices are trying to implement broadband modems. Roughly
five classes of broadband modems are available, which all use massive amount of DSP power:
• DSL, which is made of three classes in order of difficulty (SDSL, ADSL,VDSL)
• Cable modem, which is classified as a set-top box peripheral
• Broadband wireless modem (LMDS, MMDS), which is also called the “wireless DSL”
• Broadband satellite modems
• Gigabit Ethernet (and above), which positions itself as the cheapest technology
Fax
A fax can be seen as medium range modem, plus a scanner writing bits into a graphics compression
engine, and a decompression engine driving a printer. The three functions are all DSP-based. There is
no reason why fax manufacturer will not develop DSL fax. Modern networks will allow a DSL fax to
speak to a LAN fax. In fact, modern networks will allow “anything over everything” such as fax-over-IP
and voice-over-DSL. You can bet that DSP will be in the middle of all that.
Web Access Terminals
Not to be confused with an IP phone (which is limited to voice communication), a Web access device is
targeted at Web browsing and e-mail. Today (2001), all these types of devices and the so-called “Internet
appliances” are struggling to find a mass-market acceptance. Despite this, three classes exist: Web station,
Web phone, and Web pad.
Web Station
It is a $99–299 consumer device in the form factor of a small laptop. It allows web browsing, send/receive
e-mail, and (maybe) JPEG decode. Web browsing requires a modem (more likely V90 than DSL), which
means DSP. Since V90 is less than 30 DSP MIPS and today’s DSPs give anything from 100 to 1500 DSP
MIPS, the use of a full-blown DSP might not be required. On the other hand, the unused performance
can be put to good use: multimedia decode.
Web Phone
This is the same as the Web station with the addition of telephony. Note that in the IP world, phoning
requires more DSP MIPS than Web browsing.
Web Pad
This is a cordless web station with a form factor identical to the pentop of 1992–1994. The DSP functions
are fifty/fifty shared between the base and the tablet. The big advantage of a Web pad is to be network
independent or modem independent. The big disadvantage is the price of the display.
Videophone
Videophone shares with speech recognition the honor of being the most promising 1971 DSP application.
Thirty years later, many progresses have been made. The next 10 years will surely bring their annual
series of breakthroughs.
Cell Phones
The modem put DSP on the radar screen in the 80s. By comparison, cell phones put DSP in the stratosphere
in the 90s. By the end 1999, the cell phone was the star of the electronics world with more than
300 million handsets a year, some containing multiple DSPs. Multiple DSPs are needed because a cell
phone DSP function is traditionally divided into two parts: the speech coding and the channel coding.
© 2002 by CRC Press LLC