David Strom

Mobile Computing Comes of Age

By David Strom

Cutting the cord that connects us to our data hasn't been very clean nor very easy, even with

a series of improvements and conveniences added over the past year or so to make mobile

computing well, more mobile. 

Most applications are easily susceptible to motion sickness: like some young children, they

prefer to stick close to home and don't travel long distances very well. There are several

reasons: inflexible configuration management (for dealing with various hotel phone dialing

strings and network access passwords), lousy throughput (even the best phone link still

delivers less than a hundredth of the capacity of your typical LAN link, and wireless

connections can be up to five times slower than the average wired telephone connections),

and lack of protocol support for mobile users (IP and IPX, the two most popular LAN

protocols, were never designed for machines that move about from network to network).

On top of this is a fast-changing scene as standards and technologies evolve either weakly or

weekly. It is a challenge just to get a current price list, as vendors maneuver, reformulate, and

pick new partners. 

Andy Seybold, a long-time user of various wireless products and editor of a series of

newsletters in Brookdale, Calif. has written:

"If you expect wireless data systems to provide the same features and functions that you

experience when you are sitting in front of your Pentium desktop computer connected to a

LAN, forget it! However, if having access to your data in near real time is important to you,

then 1995 should be the year that you cut the cord and stand up to be counted with those of

us who have wireless connectivity to be a viable solution that saves us time and money."

So what does 1995 have in store for the mobile computing community, a community

enthusiastically estimated at over 25 million workers by the Yankee Group? Here are a few of

the key trends:

-- Sending data over your cellular phone is no longer akin to mission impossible. It used to

be getting a cell phone connected to a modem was a labor of love, an exercise in patience, or

just plain expensive and impossible. Better error-correcting modems, more laptops with

common PC credit-card sized-slots for them to fit in, and more data-friendly cell phones are

changing this. Now it is more a matter of finding the right connector cable that goes between

the two devices. 

"Each cell phone vendor has their own physical connector and their own interface

electronics," said Rebecca Krull, manager of emerging technologies for Megahertz

Corporation in Salt Lake City, one of the leading vendors of modems. "And to make matters

worse, there isn't any move to standardize on either the connectors or the interface. The cell

phone vendors are more interested in voice than data customers." There are varying estimates

of the percentage of the overall cell phone traffic which is data, but most analysts peg this at

less than five percent of over users, or about 350,000 users in late 1994. This compares to

roughly half of the wired phone calls being data, according to several analysts -- the potential

opportunity for cellular data is therefore huge.

To help encourage data over cellular, several vendors have standardized on one of two

modem compression and error-correction techniques: either AT&T's Enhanced Throughput

Cellular protocol or Microcom's Network Protocol 10 (MNP 10), both of which help keep

cellular throughput high.

-- Remote email packages continue to improve. Last year saw enhancements to mobile email

products from Lotus' cc:Mail and Word Perfect/Novell's Groupwise divisions. These products

made it easier for traveling workers to manage their mail from the road and deal with

different hotel dialing strings. Expect Microsoft to catch up this year and further

enhancements from the other vendors. 

There are two big problems with remote email management: dealing with dialing strings and

other configuration issues and managing where you receive your mail. Better technology will

help with the former, but keeping track of whether your mail is on your local hard drive or

the network server will remain a vexing issue for many mobile email users.

Radiomail Corp.'s Radiomail and Ardis' Personal Messaging are two attempts to get around

this issue, by having software that will work with a portable radio modem. This creates a

problem, whereby "to get in touch with someone, you often have to hunt through a maze of

contact points trying to guess where the person might be, or you leave a message at as many

places the person might check," writes Steve Gadol and Mike Cleary in a Sun Microsystems

research paper last year.

-- Wide-area wireless networks get better. The major players in this marketplace continue to

improve their network coverage areas, throughput, and latency to support a wider variety of

applications. Ardis, (Lincolnshire, Ill.) now solely owned by Motorola, is beefing up its

network to compete head-on with RAM Mobile Data (Woodbridge, N.J.) and players from the

Cellular Digital Packet Data Consortium.  

"CDPD offered far better response time than either RAM or Ardis," says David

Westmoreland, VP of Airport Systems for Sabre Decision Technologies in Dallas, Tex. [For

photo opp, contact Debbie at 817 963 2009] "We found it barely slower than with our

hard-wired Sabre terminals and very reliable." Sabre is the data processing company behind

American and other airlines, and will deploy wireless terminals at several airports this year.

"We want to provide a more personal level of service and be able to enter information faster

to provide a competitive edge," says Westmoreland.

Even with these improvements, shopping around for the best price and support can be

daunting. (See sidebar X). "There are too many plans that are too hard for most users to

fathom," says Krull.

-- New software that is exclusively wireless-enabled comes to market. "Applications must be

re-architected to take advantage of this new mobile platform," says Bruce Robertson, senior

editor with Network Computing magazine who has tested a variety of these products, such as

Oracle's In Motion. This product was the first software tool designed from the ground up for

supporting wireless data transmissions between clients and network servers, and other

products will be out over the next year. These products pare the data transferred to a moving

client to the bare minimum to deal with the limited throughput and latency that wireless users


Oracle calls this "client-agent-server" computing, since software agents act on behalf of the

client, even when the client isn't connected to the server. The agents reside on the LAN near

the server, and can filter the data stream from the server down to what is appropriate over a

wireless link. "There was no call setup by the user or the application per each database

request. It just happened," says Robertson.

-- Networks are becoming more tolerant of mobile users. There are a combination of

technologies that make networks more mobile-friendly, including better remote access

products and protocols. A few years ago, the notion of having a dedicated box for remote

users was a novelty. Now these products, such as ones from Shiva, 3Com, Microcom and

others, support a wide variety of protocols and have fairly solid sets of features, so that

traveling users can more easily connect back to the home office network.

One large development has been a new TCP/IP feature called Dynamic Host Configuration

Protocol or DCHP. A server runs this protocol, such as Microsoft's Windows NT, and doles

out TCP/IP addresses on the fly, freeing up network administrators from this drudgery. FTP

software has started shipping DCHP-enabled products last year, and look for products from

Sun and other IP stack vendors to appear throughout the remainder of this year.

-- Wireless LANs get cheaper and more interoperable. The notion of being able to not have to

wire every desktop for network access has lots of appeal, and a variety of technologies have

appeared in the last several years to offer this short-distance (typically less than several

hundred feet) kind of roaming. "We want to be able to give our health-care professionals

immediate access to patient records. There is a huge potential cost and convenience savings,"

says Carey Grunwald [202 786 9574], a computer systems analyst at the Department of

Veterans Affairs in Washington, D.C. who has tested a variety of wireless LANs for use in

the VA's hospitals across the country, including products from Proxim and Norand. "Having a

wireless terminal nearby a patient's room helps to reduce the time to document patient care,

and reduces medication errors," he says. 

The VA is using mostly spread-spectrum radios in its hospitals: "Their performance is solid

and prices are dropping. We like the built-in security, and you don't need to worry about

licensing issues with FCC.  And, our hospitals like them because they don't interfere with any

of their medical systems." 

According to market researchers at Dataquest, more than 3 million wireless LAN nodes will

be installed by 1997. This may be an optimistic estimate, but it could be fueled by the recent

work of several vendors to standardize on a wireless LAN protocol in the IEEE 802.11

committee. The first products, such as Xircom's NetWave, began shipping late last year, and

expect others to come soon. "Right now one vendor's gear won't function with another's

equipment," said Grunwald. "But eventually we hope the federal government will have put in

place a requirement for interoperability."

-- Better integration with products. Wireless Telecom, Inc. (Englewood, Colo.) in the past

year has offered, through its resellers, a variety of mobile gear, including cell phones, service

contracts with RAM and Ardis, wireless terminals and modems. However, they are so far

alone in providing a one-stop shopping center for buying all the technology you need for a

complete mobile computing solution. "We've had great difficulty in integrating our various

systems," says Sabre's Westmoreland. "There isn't a single vendor to do the complete end to

end product, so we've had to do it ourselves."  

-- Sorting out the emerging technologies (PCS, SMR etc.) "There will be two types of

Personal Communications Services (PCS)," according to Seybold. "One will be built by those

who believe that the cellular voice model is the right model and the second by those who

believe that the integration of voice and data are important to the overall scheme of things."

A number of new systems have begun, each of which has differing frequencies, power

requirements for mobile devices, and ranges. The chart below summarizes this.

Chart:  Technologies vs. capabilities of new technologies


Name of service

Frequency range

Expected data throughput

Mobile device power

Mobile device range

Type of network


Broadband PCS:  1900 MHz/ 2.4 kbps - 19.2 kbps?/100mW -

3W?/Nationwide/Circuit switched or Packet Switched ?

Narrowband PCS: 900 MHz/2.4 kbps - 24 kbps/100mW/Nationwide/Message Switched

ESMR: 800 MHz/ 7.2 kbps/ 600 mW - 3W/Regional/Circuit Switched

Cellular:  800 MHz/2.4kbps-19.2kbps/100mW - 3W/Nationwide/Circuit Switched

RAM: 900 MHz/8 kbps/600mW - 10W/Nationwide/Packet Switched

Ardis: 800 MHz/4.8 kbps - 19.2 kbps/600mW - 3W/Nationwide/Packet Switched


SIDEBAR #1: Products to watch:

Keep your eye on the following products as examples of where the industry is headed

throughout 1995:

--Oracle Corp.'s (Redwood Shores, Calif. 415 506 4176) Oracle in Motion  Released late last

year, OIM is the first product to take advantage of disconnected and low-bandwidth links

between clients and servers. The software, which runs on a combination of Windows and

Unix platforms and the RAM network, has the ability to filter traffic that is transmitted over

the radio link to the bare minimum, keeping response time high and packet charges low. Look

to other companies to use OIM as the basis of their product offerings, such as Cordless

Computer Co.'s email software. Oracle is likely to support other wireless links, such as

cellular and Ardis, in the upcoming year.

--Ericsson GE Mobile Communications (Totowa, NJ 201 890 3645)  M2190 OEM Wireless

Modem, a PCMCIA Type III credit-card-sized modem that connects portable industrial

terminals and hand-held devices via RAM's network. This modem is a cousin to the

company's larger Mobidem wireless modem, and because of its smaller size it can be more

convenient to carry. While the company is only shipping an OEM version for the vertical and

industrial market, look for them to add an end-user device later this year for wireless email

and other office applications. Norand (Cedar Rapids, Iowa 319 369 3100) was the first to

integrate the M2190 into their own devices, called Pen*Key, a two-pound portable computer

that has a numeric keypad and is used in many vertical-market operations such as

supermarkets and warehouses. Look for other PC card-sized radio modems from Motorola and

others in the coming year.

--Zenith Data Systems (Buffalo Grove, Ill. 708 808 5000) Cruise Pad. Cruise Pad is a

tablet-style computer without any local storage but with built-in remote control software. It

connects, via a wireless LAN link developed by  Proxim, back to a base station located on

the main LAN. Users can roam about their offices with a range of several hundred feet and

remotely control their desktop computers, while still remaining connected to their office

networks. The device is small and has an optional keyboard. Zenith started shipping this

device late last year. Look for this device to show up on factory floors and in areas such as

health care where "local mobility" is important.

--Various Magic Cap devices, including Sony's PIC-1000 Magic Link and Motorola's Envoy.

Sony has been shipping their device since last fall, and Motorola's since TK. Envoy has a

wireless Ardis modem along with a standard wired modem, while Sony's Magic Link just has

a wired modem that runs at 2400 bps for data and 9600 for fax (sending only).  While the

Magic Cap operating system is somewhat hyper-graphical (with cute icons representing

desktops, filing cabinets, rolodexes and the like) it is the only operating system that comes

with built-in communications: each device must have at the minimum a wired modem to talk

to others users via a wide-area service provided by AT&T called PersonaLink, as well as a

built-in infra-red link to beam information to users in the immediate vicinity. Look for other

devices this year, and for the existing ones to improve. 

--Microsoft (Redmond, Wash. 206 882-8080) Windows 95. While still not available,

Windows 95 is the first attempt by Microsoft to build-in mobility support. A special modem

driver application (called "unimodem" is part and parcel to this new operating system, which

means that all asynchronous communications applications can work better together (and of

course, have to be rewritten to take advantage of this service).  


SIDEBAR #2. Is wireless worth it? 

Calculating the costs of wireless service will require someone with various skills: it helps to

be part investigator, part accountant, and part software engineer. The various vendors have a

multitude of plans, options, and add-on charges that require reading lots of fine print and

understanding how one's applications actually work. All in all, pricing out wireless service

options is not for the faint of heart. 

To compare service offerings, we formulated three potential users:  

--Occasional.  Someone who sends 60 1 kilobyte messages a month, and receives another 30

1 kilobyte messages. This person will spend approximately four minutes a day connected to

their email server, for a total of 100 minutes a month.

--Average.  Someone who sends 60 1 Kb messages plus another 60 Kb of files, and receives

100 messages of 1 kilobytes, for a total of 220 kilobytes of data a month. This person will

spend 200 minutes a month connected to their email server.

--Power. Someone who sends and receives  a total of 1 megabyte of messages a month, and

is connected for 250 minutes a month to their server.

We also assume that all traffic is done during peak hours to obtain the worse-case scenario

for the costs, and that no further discounts or negotiated fees are factored into this analysis.

(Many of the vendors have various breaks on pricing for large corporate customers and offer

off-peak pricing as well.)

We looked at four different service providers: RAM Mobile Data, Ardis, circuit-switched

cellular, and Cellular Digital Packet Data (CDPD).


RAM has two kinds of pricing schemes: one for email users which is one of the simplest

schemes around and one for other kinds of users which is more complicated. "We designed

something with a flat rate at the top that was easy to understand," says Ed Collyer, who is VP

of Network Products Management for RAM in Woodbridge, NJ. 

The email plan is based on three pricing tiers that can range from $25 to $135 a month. Users

can sign up for service on any tier and if their usage puts them in a higher or lower price

bracket, RAM will do the calculations and get them the best price accordingly. RAM charges

users for packets that are both sent and received on their network, and has a $50 signup fee

for each user. They also charge each server connection a rate ranging between $50-700 per

month, depending on the speed of the dedicated line that connects the server to RAM's


Given this information, here is what our three typical users would pay for monthly service: 

O:  $25/month

A: $55/month

P: $135/ month

Thus RAM is probably the least expensive option for the power user, given our assumptions.


Ardis has two different pricing plans for email users and for non-email users. Non-email users

(such as industrial alarm vendors and others) have various discounts, including off-peak

pricing and reduced prices for short messages. The email plan, which covers users of Ardis'

Personal Messaging products that are available on several platforms ranging from a Newton

to a laptop Windows machine, has various different pricing structures, based on the type of

service that Ardis is providing. For example, two-way messaging has one set of prices while

paging services has another. The two-way messaging plan has three different pricing

categories with different monthly minimum allowances. Ardis charges on a per-message basis,

and as with RAM, they charge for both sending and receiving data over their network. Our

three typical users would be charged as follows:

O: $54

A: $129

P: $550 

Ardis works out to be the more expensive of the providers in general.


Finding a vendor that would provide information on CDPD was a challenge. Most of the

vendors contacted in late 1994 still did not have a standard rate card for their service, and

provide individualized pricing plans for each of their customers. Only GTE (with service in

the Bay Area and Houston) and Bell Atlantic, with service in Pittsburgh, Philadelphia

[CHECK IF IT IS STARTED UP BY MARCH], Baltimore, and Washington DC, was able to

provide us with rate sheets, and both were a confusing jumble of many different options. 

Karen Ann Kurlander, general manager of corporation communications of Bell Atlantic, based

in Bedminster NJ,  agreed their rate card was complex. "We have to train our own account

representatives and executives on how to calculate various representative costs," she said.

GTE offers four different plans while Bell Atlantic offers five. Bell Atlantic is the more

complex, since each plan has three separate cost components: a minimum monthly service

allowance which goes towards the first series of charges on the account, a per-kilobyte

charge, and a per-packet charge that is typically an additional ten percent of the kilobyte

charge. (However, if your application sends lots of small packets, this could be much higher.

How do you know? This is where being a software engineer comes in handy.)

The latter two charges have steep discounts when traffic is sent or received during off-peak

hours (after 8pm and before 6 am during weekdays.) There are also additional charges for

connecting dedicated lines from a customer's servers back to the Bell Atlantic network which

range from $40-$50 a month per line, depending on the speed of the connection. This is one

bargain for corporate customers: a 56 kilobit circuit that would cost $700 a month if

connected to RAM costs only $50 a month when connected to the Bell Atlantic network. Like

RAM and Ardis, Bell Atlantic charges users for both traffic that is sent and received over

their network, but unlike RAM won't automatically optimize your bill depending on your

actual usage.

Given our three typical users, CDPD is higher than RAM but lower than Ardis, especially for

the power user scenario. Monthly rates for our three typical users with GTE would be

somewhat similar to those we calculated from Bell Atlantic's:

O:  $24 

A: $49  

P: $185 

Just to show you how bizarre Bell Atlantic's pricing scheme is, with our Occasional user if

we had picked another pricing plan that had a lower monthly minimum but higher

per-kilobyte charge, it would have cost twice as much. And, roaming is not yet possible, since

each CDPD provider has its own system that is not connected to the others.

Circuit-switched cellular.

Our final provider is ordinary cellular communications. Given the length of the conversations

for each of our typical users, we assume that the cost of the cellular calls are 50 cents a

minute, which is fairly typical for peak-time long-distance usage with few discounts and does

not include roaming charges. Our three typical users will pay per month:

O: $50

A: $100

P: $125

Thus, traditional cellular can end up being a fairly competitive option for users, but this

depends on the length of the call and the speed of the connection, which can vary

tremendously among the various applications. Indeed, Bell Atlantic's Kurlander recommends

circuit-switched cellular for power users. "It isn't appropriate to use CDPD to send megabytes

of data per month," she says.

-- D.S.

Potential infographic: Nomadic Rules of the Road

Two researchers at Sun Microsystems, Steve Gadol and Mike Clary, have come up with

several operating assumptions for dealing with nomadic users.

1. Nomads are part of an organization. 

2. Nomadness is primarily concerned with communications, not computing

3. Nomads shouldn't have to deal with a whole new infrastructure.

4. Nomadness is not free.

5. Nomads need flexible communications protocols.

6. Nomads want to use multiple devices, but ideally have only one public identity.

7. Nomads consider security mandatory since physical security is negligible.

8. Nomads want to use paging and polling to satisfy two different application needs.

9. The nomad will want to access the enterprise network using a variety of access methods.

10. Nomadic users will cause more failures than those caused by hardware or software bugs.

-- Gadol and Clary, Sun Microsystems. [This paper is available on the internet from Sun's

Web server.  The URL:



David Strom founded Network Computing magazine and frequently writes about wireless and

mobile networking topics for a variety of industry publications. He runs his own consulting

firm in Port Washington, NY and can be reached via the internet at david@strom.com

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David Strom David Strom Port Washington, NY 11050 USA US TEL: 1 (516) 944-3407