Wireless Technology Essay, Research Paper
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. II.
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-based communication. 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: a. Data Integrity -
relatively error free transmission, b. Speed – as close as possible to the speed
of current wired networks, c. Protection – making sure that the data now
airborne is encoded and cannot be tapped by unwelcome receivers, d.
Compatibility – ensuring that the many protocols that sure to be created
subscribe to a standard to allow inter-operability, e. 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
semi permanent 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. II. Methods There are a few methods of wireless
communication being theorized and tested. 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 ranges 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: a. Higher frequencies mean shorter wavelengths and
shorter wavelengths do not penetrate solid objects like walls and floors; b. 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. c. 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. d. 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. e. 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. f. 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 sends a jamming signal at that time. A wireless transceiver will not only
sense a carrier but will also listen 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) -If it did, it slows the network significantly by sending
jamming signals whether or not a collision actually occurs. IV. 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 Multi-megabit 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 end user
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