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Wireless Technology Applied To Computer Processing


Wireless technology can provide many benefits to computing
including faster response to queries, reduced time spent on
paperwork, increased online time for users, just-in-time
and real time control, tighter communications between
clients and hosts. Wireless Computing is governed by two
general forces: Technology, which provides a set of basic
building blocks and User Applications, which determine a
set of operations that must be carried out efficiently on
demand. This paper summarizes technological changes that
are underway and describes their impact on wireless
computing development and implementation. It also describes
the applications that influence the development and
implementation of wireless computing and shows what current
systems offer. 1 Introduction Wireless computing is the
topic of much conversation today. The concept has been
around for some time now but has been mainly utilizing
communication protocols that exist for voice
basedcommunication. It is not intended to replace wired
data communication but instead to be utilized in areas that
it would be otherwise impossible to communicate using
wires. Only recently has the industry been taking steps to
formulate a standard that is more suitable to data
transmission. Some the problems to be overcome are: (1)
Data Integrity - relatively error free transmission, (2)
Speed - as close as possible to the speed of current wired
networks, (3) Protection - making sure that the data now
airborne is encoded and cannot be tapped by unwelcome
receivers, (4) Compatibility - ensuring that the many
protocols that sure to be created subscribe to a standard
to allow inter-operability, (5) Environmentally safe -
strengths of electromagnetic radiation must be kept within
normal levels. In our study of the theories and
implementation concerns of wireless computing, we found
that it is being treated in an object oriented fashion.
Scientists and development crews, including the IEEE, are
doing their best to implement wireless connectivity without
changing the existing computer hardware. As a result, a lot
of focus is on using existing computer hardware and
software to convert data to a format compatible with the
new hardware which will be added to the computer using
ports or PCMCIA connections that already exist. This means
that wireless communication will be transparent to the user
if and when wireless computing is utilized on a wide scale.
Wireless computing applications covers three broad areas of
computing today. Replacement of normal wired LAN's need to
retain the speed and reliability found in wired LAN's.
Creation of semipermanent LAN's for quick and easy setup
without the need for running wires. This would be necessary
for events such as earthquakes. The last category is that
of mobile computing. With advent of PCMCIA cards, notebook
computers are being substituted for regular desktop
machines with complete connectivity of the desktop machine.
However, you lose the connectivity when out of the office
unless you have a wireless means of communicating. On the
compatibility issue, the ability to mix wireless brands on
a single network is not likely to come soon. The IEEE
Standards Committee is working on a wireless LAN standard
-- 802.11, which is an extension of the Ethernet protocol.
Because the field of wireless communication is so broad,
the IEEE was not able to set a standard by the time private
researchers were ready to test their theories hoping to set
the standard for others to follow. 2 Methods There are a
few methods of wireless communication being theorized and
tested. (1) Radio: This is the method that makes use of
standard radio waves in the 902 MHz to 928 MHz frequency
range. Although these frequencies are well used, methods
have been developed to ensure data integrity. Spread
spectrum transmission of data is a method where the
transmitter will send information simultaneously out over
many frequencies in the range increasing the change that
all data will eventually reach the receiver. Frequency
hopping is an additional measure that also enables data
security. The 26 MHz range of frequencies is further
divided in to channels. The transmitter then sends out data
hopping from one channel to the next in a certain pattern
known to the receiver. Within each channel, spread spectrum
transmission can be used to maintain interference
avoidance. Some of this transmission manipulation can be
avoided by transmitting at a frequency that is less used.
Some developers have tried transmitting in the gigahertz
range. The disadvantages here are: 1) Higher frequencies
mean shorter wavelengths and shorter wavelengths do not
penetrate solid objects like walls and floors; 2) The same
transmission strength employed by lower wavelength
transmitters yields a shorter range at higher frequencies.
This means that transmission strength will need to be
boosted something hard to accomplish using portable tools
and potentially dangerous to humans; 3) Transmission
frequencies of 3 GHz and higher are licensed by the Federal
Communications Commission. Developers in the range have the
additional hassle of obtaining a license every time an
installation is done. (2) Laser: Laser-based communication
is the fastest way to communicate without wires.
Information travels at the speed of light. The drawbacks
however far outweigh the speed advantage and prevent this
method from becoming the standard. The major drawback is
that communication is restricted to line of sight. Also,
very thick fog or blizzard conditions will diffuse the
laser beam and causing interference and reducing data
integrity. (3) Infrared: This method is similar to Laser.
High speed communications are easy to achieve using this
method. However, it suffers from the same problems that
plague laser communications. It requires line of sight
transmission and can be disrupted by strong ambient light.
Infrared wireless computing exists more commonly in the
form of peripheral connections in a small area. (4)
Cellular connections although expensive to use now is the
area of much development by private companies. Cellular
computing can be likened to the current wire-based internet
network. Data is packaged in to units, size of the unit is
dependent on the actual hardware, and is sent to the
nearest participating cell. That cell then forwards the
packet to the next cell and so forth until the packet
reaches its destination. (5) Microwave: This method of
communication has been utilized for quite some time now.
However this method has makes little provision for data
aware transmission. It used extensively in Europe where
wired transmission of any type including voice is poor. For
data transmission, a lot of technology is utilized in
packaging the data into a form that is compatible to voice
communication. On the receiving end, the process is
reversed. The advantage of this method however is that
communication can be accomplished using existing satellite
connections making worldwide connectivity possible. 3
Standards The IEEE 802.11 committee has voted to create a
minimum requirement for wireless computing connections. In
their consideration: (1) Use the frequencies 2.4 to 2.5
GHz. This is in the low end of the high frequency spectrum
and is currently not licensed by the FCC. (2) Use spread
spectrum technology. Compared to the current bandwidth 26
MHz, 902 MHz to 928 MHz, the range 2.4 to 2.5 GHz yields a
bandwidth of 100 MHZ. Spread spectrum transmission now
gives 385% percent increase in data reliability. (3) Many
more sub-channels can be formed in a bandwidth of 100 MHZ.
This increases the capability of frequency hopping which in
turn yields greater data security. (4) Utilize Gaussian
Frequency Shift-Keying. Frequency shift-keying is a form of
frequency modulation in which binary signaling is
accomplished by using two frequencies separated by some Df
Hz. The frequency duration is small compared with the
carrier frequency, fc. A signal received at frequency fc,
would represent a digital low and signals received at
frequency fc + Df, would represent a digital high. Note
that this does not interfere with spread spectrum or
frequency hopping capabilities since those function on
frequencies separated by 1 MHz or more. As part of setting
a wireless standard some modifications of the standard set
by the IEEE 802.3 committee have been adopted. The most
significant of these is the modification to the carrier
sense multiple access / collision detection, or CSMA/CD,
protocol used in wired networks today. This is a method
whereby any machine at any time, wishing to send a message
on the net, will first send a token out to ensure that a
carrier exists (network ready). After establishing this,
the message will be sent. Because any machine may send at
any time, collisions of information will occur. If any
machine detects a collision, it will send out a jamming
signal to all the others. All machines will then wait on a
random interval timer after which they will try to send
again. For wireless networks however, since a machine is
not in constant communication with the rest of the LAN,
detecting a collision and notifying all other machines on
the net is impossible. A modification in the way of the
collision handling had to be made. A method known as
collision avoidance is employed to create the CSMA/CA
standard. In a collision avoidance strategy, the net
estimates the average time of collisions and send a jamming
signal at that time. A wireless transceiver will not only
sense a carrier but will also listen out for the jamming
signal. When all is clear it then send its message. This
collision avoidance method has two drawbacks: 1) It cannot
completely filter all collisions since it operates on
estimated times of collisions; 2) and if it did, it slows
the network significantly by sending jamming signals
whether or not a collision actually occurs. 4 Physical
Layer Much of the focus of wireless computing development
is centered on the physical and media access control layers
of a system. It is on this level of the LAN protocol of
which wireless products like modems and transceivers On the
physical layer issue, the 802.11 is focusing on the one
proposed by Apple Computer Corporation. The Apple
physical-layer protocol appears the most robust of any
considered to date in 802.11. Apple's system is a
full-duplex, slow frequency-hopping protocol. By using a
frequency-hop spread-spectrum radio, the system fits with
the spread-spectrum methods of virtually all 802.11
specifications. Apple splits the data-transport protocol
into two layers: The RF Adoption Layer is similar in some
respects to cell-based data protocols, such as Asynchronous
Transfer Mode and IEEE 802.6 Switched Multimegabit Data
Services; like ATM and 802.6, the RF Adoption Layer
includes segmentation/reassembly functions and Protocol
Data Unit generation functions, and it also includes
Forward Error Correction (FEC) generation and verification
functions which substantially increase packet integrity in
wireless environments but adds FEC overhead. The RF Hopping
Protocol Physical Layer consists of a transmission
convergence sublayer including header generation, RF
framing, and RF hopping protocol functions and the
physical- medium-dependent sublayer, in which the actual
characteristics of the RF channel are handled. In the RF
Adoption Layer, a Protocol Data Unit is split into three
segments, and two error-correcting data units are added.
The RF Hopping segments, and two error-correcting data
units are added. The RF Hopping Physical Layer builds
special Burst Protocol Data Units out of the data and FEC
units and uses carrier-sense methods borrowed from Ethernet
to determine whether an RF Hop Group is clear for
transmission. Each hop group consists of five separate
radio channels. The controller scans hop groups via
state-machine operation with four states: scan, receive,
carrier-sense, and transmit. In early tests at Apple, the
hop system showed 80-microsecond hop times, 57-microsecond
clock recovery, and a 5-microsecond lapse between the time
an empty channel is sensed and transmission begins. Since
each cluster of wireless LANs can use different hop groups,
multiple LANs could operate in the same area without
interference. One concern is whether the overhead for error
correction for each packet, which can be as much as 50% is
too high to give the proposal a chance. The safety of those
operating new equipment now plays a larger role in
determining the direction of technological growth now more
that ever. Factors under consideration are the effect of
infrared and strong electromagnetic radiation that would
pervade the workplace on the workers. This limits the
strength of and communication device that would be used in
accomplishing transmission. For the Personal Computer. The
adapters have a small attached antenna through which they
send and receive network traffic as radio signals. Some
wireless products are small boxes that attach to your PC's
parallel port. In either case, the signals may travel from
PC to PC, forming a wireless peer-to-peer network, or they
may travel to a network server equipped with both wireless
and standard Ethernet adapters, providing notebook users a
portable connection to the corporate network. In either
case, wireless LANs can either replace or extend wired
networks. Standards are lacking. Wireless networking is
still a technology looking for a standard, which is why
very few wireless products can work with one another. Each
vendor uses a different protocol, radio frequency, or
signaling technology. If wired networks still operated like
wireless, you would have to use the same brand of network
interface card throughout your network. Right now you are,
for the most part, tied to whichever brand of wireless LAN
you pick. Most of the products in this comparison listed
their wireless protocol as Ethernet carrier sense multiple
access/collision avoidance (CSMA/CA), a variation of
standard Ethernet. Unfortunately, each vendor has put its
own spin on CSMA/CA, which means even their protocols are
incompatible. 5 Wireless services As technology progresses
toward smaller, lighter, faster, lower power hardware
components, more computers will become more and more
mobile. For space concerns this paper will exclude any
further discussion of the hardware developments toward
mobility except for devices directly related to wireless
connectivity such as modems. A wireless computer is not
connected via a wireline and thus has mobility and
convenience. A wireless LAN provides the convenience of
eliminating the wires, yet is not necessarily mobile. (What
is mobility?) Mobility is a characteristic where the
wireless computer may connect, loose the physical
communication (possibly due to interference) and reconnect
(possibly to another sub-network) and retain its virtual
connections and continue to operate its applications. The
network protocols will be discussed later. (Then, what is
portable?) Portable is defined that the wireless computer
may connect, loose the connection and then re-connect, as
well. However, the mobile unit will have to restart if it
is reconnected to another sub-network, requiring that
running processes be shut-down and windows closed. Mobility
may be limited by the wireless service subscribed. Four
basic service zones are described: Global/National service
zone: Ubiquitous radio coverage throughout a region,
country or the entire globe, low user densities, and
minimal bandwidth requirements. Typically satellite
systems. Mobile service zone: Radio coverage in urban,
suburban and populated rural areas, medium to high user
densities, low to medium bandwidth requirements (tens of
Kbps), and high vehicular speed. Cellular (AMPS) system is
a good example. Local/micro service zone: Radio coverage in
densely populated urban areas, shopping malls, and
transportation centers. High enduser densities, medium
bandwidth requirements, hand-held portable terminals,
low-speed mobility. Indoor/pica service zone: in-building
radio coverage, low to high user densities, medium to high
bandwidth requirements (Mbps), very low mobility. Prior
to the cellular phone network, base station radio covering
a single cell geographic area with a fixed number of
channels was the only service available. The cellular phone
service divides the service area into cells and assigns a
subset of the available channels to any given cell. This
way the channels can be reused and interference from
neighboring cells is reduced. The system tracks the active
mobile unit, delivers calls, and maintains connections as
units move between cells (Hand-off: a realtime transfer of
a call between radio channels in different cells). This
system is called Advanced Mobile Phone Service (AMPS).
Current cellular systems use analog FM technology. However,
implementation of digital radio technology is being
deployed now. These systems utilize Time Division Multiple
Access (TDMA) or Code Division Multiple Access (CDMA) to
increase throughput up to ten times the previous analog
system. Additionally, end users will access a wider range
of telecommunications as the implementation of integrated
services digital network (ISDN) principles are utilized.
Personal Communication Services, similar to the current
cellular system, will soon be available from the larger
telecommunication services, but with reduced price and
wider availability. Wireless Advantages Limitations 
Traditional Cellular no restrictions on length or type of
data transmission national coverage bill by minute
potential line interruptions, congestions in urban areas
limited throughput CDPD enhanced technology for data
over cellular bill by message size integrated voice and
data packet switching error correction techniques lack of
applications development not fully developed Dedicated
packet switched mobile networks integrated applications and
communications no call setup time inherent reliability and
security of packet switching coverage not full nationwide
limited packet size require specialized modems data only 
 Specialized mobile radio voice and data vehicle based
limited coverage Satellite-enabled networks geographic
reach expensive equipment and service costs The
application of the wireless computing system determines the
type of wireless medium system to be employed. Circuit
switched or packet switched, both are available through
wireless technology and provide connectivity. Circuit
switched systems provide a continuous connection
established to the destination by the switching system. The
most popular examples are the wireline public switched
telephone network (PSTN) and cellular telephones systems.
This method of communication can be relatively expensive.
If the phone systems offers voice grade bandwidth, then a
standard modem can provide speed of 14.4 Kbps (at the time
of this writing). However, if a digital line is provided
then higher communication rates can be achieved with more
specialized equipment. Packet switched systems provide a
delivery system of information packets. The packet contains
the data and an address to the destination. Packet
switching is far less expensive than circuit switching.
Examples would be RAM, ARDIS, and Internet networks. Packet
radio networks have been the target of many studies since
the military has a vested interest in the communication
medium. Concerns such as reliability, throughput
optimization and re-routing of packets have been recent
topics. Packet Switched Systems ARDIS RAM Mobile Data
Circuit Cellular CDPD Network Capacity 1,300 base
stations in approx. 325 metro service area (MSA) 840 base
stations in 210 MSAs 8,000 cell sites in 734 metro areas
potentially entire cellular network Coverage (cities
and towns) 10,700 6,300 NA NA Transmission speed
4.8Kbps. 19.2Kbps upgrade in major metro areas 8Kbps
38.4Kbps to 56Kbps 19.2Kbps Message capacity 256 bytes
512 bytes NA 114 bytes National roaming completed by
mid Sept 94 yes no yes In-building coverage yes top 20
MSAs by June 1993 limited limited Cellular Digital
Packet Data technology (CDPD) utilizes the space between
the voice segments on cellular (AMPS) network channels and
inserts a data packet. The user pays only for the packet
sent as opposed to a cellular circuit switched connection.
CDPD cellular communications systems such as the Ubiquity
1000 from PCSI, offer packet burst rate of 19.2 Kbps with
full duplex. This CDPD modem offers the option to use
circuit switched cellular, wireline PSTN and voice support.
However, in a large urban area with thousands of stations
using any packet switching service at current speeds, delay
may be unacceptable. Satellite can be used as long
distance links within wireless networks. Three major
projects have been proposed. The Teledesic system, composed
of 840 low orbit satellites, was proposed by Bill Gates
(Microsoft) and Craig McCaw (McCaw Cellular). Second, the
Pentagon, solicited a system, using 1,000 smaller
satellites, from TRW and Martin Marietta. Both the
Teledesic and the Pentagon systems cost around $9 billion.
The third system, called Iridium, from Motorola, will use
66 satellites to offer mobile phone service all over the
globe. This project will begin this year and the rest in
place by 1996. 6 Software Software concerns in a wireless
computing environment can be broken into two areas, system
and application. 7 System Software Network operating
systems must be able to handle the uniqueness of a wireless
computer. Advanced operating systems utilizing distributed
technology must be adapted to the specific communication
media. The advancement of technology has provided that even
mobile computer systems the size of notebooks are capable
of internetworking as a host in global networks. Mobile
host protocols compatible with TPC/IP have been developed
to allow continuous network connectivity where ever the
host may be. Due to the unpredictable nature of wireless
connections, even operating systems may have to be written
to provide support services for mobile network. The WIN*OS,
a micro kernel for a wireless-compatible operating system,
was developed to "support concurrent and composable objects
and coordinated communication among groups of objects
through a process of agreements." 8 Application Software
Application software concerns in the wireless computing
environment vary depending on the type of application and
wireless medium used. For example, E-mail software must
know how to communicate with the packet switched network as
compared to the traditional cellular network. Software
developer kits (SDK) and application programmers interfaces
(API) are usually available by the service provider. Remote
access software allows the remote user to connect to a host
workstation to view the screen and control the keyboard as
if the user was there. The data does not have to be
communicated to the remote user and thus allows processing
locally. Carbon copy and PC anywhere are among the programs
which provide remote access for microcomputers. High baud
rate is needed especially when a graphical user interface
(GUI) is used. 9 Wireless Local Area Networks (WLAN) WLAN
offers the same features as a wireline LAN but without the
wires. Coverage can range from a room to a building to a
"campus" (wide-spread, multi-building). Both stationary
desktop systems and mobile notebook computers can connect
using specialized wireless LAN adapter cards. Another
configuration allows wireless additions to current
networks. Wireless Hubs have been developed which bridge
the wireless units into the wireline network. As mentioned
before, during the recent natural disasters in California,
the Federal Emergency Management Agency (FEMA) set up field
offices with WLAN very quickly. Here is a great example of
how WLAN can be used: An ETHERNET connection over a radio
link provided data from a low-power PC in a buoy to a PC on
a ship. The system provided a megabyte/sec data rate for
four days while guaranteeing error-free delivery of data.
Even more incredible is the MBARI acoustic LAN. Since under
water, radio waves travel only a few feet but sound waves
can travel for miles, the acoustic LAN uses the better
carrier of wireless data signals. The acoustic LAN has two
5Kbps data channels and two slow-speed command channels.
The LAN is used to communicate with tilt meters and buoys. 
 Personal Data Assistants (PDA) are the new handheld
computers which also have wireless options. Using a
pen-based GUI operating system, the applications are
accessed from local storage. Fax, data and voice can be
transferred to and from the PDA via cellular phone system.
The AT&T EO can run a program called Gnosis which when also
loaded on a remote server host will allow the user to
search for documents and have them downloaded in minutes
including graphics. Even though all these nifty devices
such as radio modems and PDAs are developed and marketed, a
recent study of mobile professionals shows that currently
relatively few spend time far from their desks. In fact,
only 13 percent of mobile users spend time outside their
metro area and just 1 percent outside the country. As the
technology becomes more common place, more users will find
themselves moving further out of their wired areas and into
the wireless field. 10 Security Security becomes
essential in wireless computing. Especially since the data
is broadcast to the receiving unit. International Standards
Organization (ISO) has published security services which
provide for secure data and computer systems on standard
wireline networks. However, these must be modified to meet
the needs of mobile users and systems. Data encryption and
Two possible solutions include exchanging security
information between a small number of entities, or even
more complex involving an information center. Infrared
offers the least problem of security due fact that stations
must be in the line-of-sight and the limited area of
coverage, usually one room. Spread spectrum RF
transmissions spread the data over a range of frequencies
making interception extremely difficult. Also, low power
limits the coverage area, although the signal will
penetrate walls. Cellular phone networks offer no security
of their own. Even though listening to these transmissions
has been made unlawful, the signals can be overheard by a
radio scanner. Data encryption is left up to the connecting
unit. Packet radio offers inherent data security by
scrambling the data packets. Clipper chip will replace the
digital encryption statndard (DES). The Clipper chip boasts
to be 16 million times stronger with 80-bits as compared to
the old DES, which has a 56-bit binary key. This chip will
be used in many communication products, especially
wireless. The Department of Justice and AT&T will be
installing them in their telephone products. The
controversy about these chips stems from the fact that they
are programmed with a back door. The government can, with a
court order, access the chip and monitor the communication.
 11 Conclusion In the relatively short time of the
Information Revolution, the world has seen several
technologies, first introduced as "convenient", become
"essential" the basic structure of the modern lifestyle.
The automobile, telephone, and the refrigerator are easy
examples to cite. The wireless revolution will transform
another "convenience" to a necessity. "Emerging wireless
systems will provide the technology to allow people and
machines to communicate anytime, anywhere, using voice,
[video,] data and messaging services through
telecommunications." The wireless revolution began with the
introduction of the cellular phone networks. This coupled
along with the reduction in size of the microcomputer and
an increase in the applicable technologies. After surveying
the many aspects of wireless computing, several areas
stand-out and appearently require further research and
development. Among those are mobile internetworking
protocols, which would allow a mobile host to connect to
any part of the network. Mobile "aware" operating systems
would further allow more features catering to mobile users.
Features such as built-in APIs in the OS kernel available
for specific applications which would provide services
pertaining to suspend/resume and store and forward
operations. Standardized mobile networking protocol will
allow interoperability between open wireless systems.
Advanded signal processing and speech coding techniques
will allow more efficient use of bandwidth and data
transfer speed. Security research at all levels will
continue to remain an issue and must stay one step ahead of
the criminal elements. All of these areas will help to
bring about the wireless computing revolution. 
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14 Endnotes


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