FREE ESSAY ON WIRELESS TECHNOLOGY AND COMPUTERS

WIRELESS TECHNOLOGY AND COMPUTERS

Wireless Technology applied to Computer Processing
Abstract
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.
12 About the authors
Christopher xxxxx
Christopher xxxxx is a first year Computer Science graduate student of Florida
International University. He is also an operations systems analyst for xxxxxxxx xxxxxxxx
xxxxxxxxxxx xxxxx of Florida where he participates in the implementation of a
DB2/Client-Server operating system. He graduated with a Bachelors in Computer Science
from FIU in 1992. His current interests in research include mobile computing and visual
object oriented programming.
David R. Xxxxxxxxx
David R. xxxxxxxxx is currently a Master's degree candidate at Florida International
University where he originally graduated with a Bachelors degree in Computer Science in
1986. He also designed cirriculum and taught lower and upper division computer classes
for the School of Computer Science at FIU. For six years he has been employed at xxx xxxx
xxxxx as Accounting/Informations systems manager. He is an avid user of mobile computers
and advanced technology.
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14 Endnotes