First, Bandwidth and disconnection

lowlyoutstandingΚινητά – Ασύρματες Τεχνολογίες

24 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

63 εμφανίσεις

Thank you Mr. Chairman, and Ladies and Gentlemen:


I

am very glad to have this opportunity

to introduce you a new computing paradigm which is
called

mobile computing

.


The advent of mobile computing owes to two key techniques. One is wireless communicati
on, the
other is the Very Large Scale Integration technology. The wireless communication makes us can
go outside while still keeping in contact with other people or accessing the information in the
Internet. The development of VLSI makes the computer small
er and smaller and thus brings forth
the

portable computer or notebook

, so we can use computers not only in office rooms, but
outdoors.


The combination of these two techniques makes mobile computing feasible.


Someone may ask what

s mobile computing? Un
fortunately, there is no standard definition of it,
but I think we can understand this concept by describing what we can do using mobile computing
technology. Mobile computing allows us to work away from stationary facilities where we
normally operate in a
n office.


To spread Mobile Computing Paradigm, there are some technical issues laid in our way.


First, Bandwidth and disconnection

In mobile computing paradigm, people
usually

connect to Internet through wireless network
whose bandwidth is much narrower

than that of wire cable network. And disconnection often
occurs
while in communication with other computer.

So software running in mobile computers must be adjusted to fit the wireless communication.
The utilization of network bandwidth can be improved b
y logging and compression of data before
transmission. In addition, lazy write back and file prefetching can let data transmission avoid the

rush hour


of network.

Caching frequently accessed date reduces contention in narrow bandwidth wireless networks
a
nd improves the query response time. It is also helpful to deal with the problem of disconnection.


Second, Security Risks

Because of the ease of connecting to wireless link, the mobile computers transmitting data
through wireless media are much more vulne
rable than stationary PCs. Hence appropriate security
measures should be taken.

Data encryption and identity authentication are two measure often deployed to enhance
security.


Third, Location Awareness

When moving around different network, mobile compute
rs may encounter different network
features. A mobile computer must be able to switch from infrared mode to radio mode as it moves
from indoors to outdoors.

Thus mobile computers have to be featured with the ability of knowing where they are.


Fourth, rou
ting problem

Mobile computers frequently change their point of attachment to the network. The currently
deployed Internet routing protocol family TCP/IP is specially designed for stationary computers.


Each computer connecting to Internet must acquire an
IP address. This IP address is both the
unique name of the computer in Internet and the indication of the network location. (The IP
address indicates which network the computer attaches to.) When the computer changes its
attachment point to another network
, it must acquire a new IP address in order to correctly connect
into Internet. Because of its new IP address, its name in Internet has changed.


So while a mobile computer moves from a network to another network, it must change its IP
address, but other
computers in Internet would not recognize it as the former mobile computer
because of the changing of IP address. If this mobile computer retains it IP address, the routing to
it will operate incorrectly. This contradiction make TCP/IP unfit for mobile com
puter.


To deal with this problem, many solutions have been proposed such as Mobile IP, optimized
Mobile IP and so forth.




There are some other technical issues of mobile computing such as Power Consumption, Storage
Requirements,
and User

Interface Desi
gn.


Because of the time limitation, I don

t address them here. And that

s what I want to tell you about
mobile computing. I am willing to answer questions of yours.



Have you any questions?


Q&A


Why does mobile computing become so pop nowadays?


Peopl
e have the capability of accessing information in Internet in anytime, at anyplace, and
collaborating with anyone else. It will improve our working efficiency.


Have you any example of this computing paradigm?


WAP, wireless application protocol, WAP mobil
e phone



Among those technical problems you

ve just mentioned, what

s the most important one in your
opinion?

Routing problem, it

s the basic technique to implement mobile computing.