advanced computer architecture: wireless communication basics,Architecture various types of services (DSS,ES)

1. Wireless Networks:
Wireless Communication Basics, Architecture
Wireless is a term used to describe telecommunications in
which electromagnetic waves carry the signal. A wireless
network is defined as technology that allows two or more
computers, to communicate, using standard protocol but
without the use of network cabling. A wireless LAN (or
WLAN) is one in which a mobile user can connect to a local
area network through a wireless (radio) connection. The IEEE
802.11 group of standards specifies the technologies for
wireless LANs

2. Advantages of wireless networks are:
1. Mobility improves productivity and service.
2. Portable and flexible.
3. Easy to install.
4. Scalability - Easy to reconfigure.
5. High speed and simplicity.
6. Reduced overall cost
7. Makes available real-time data in broader range of coverage areas
Working: Each device is equipped with short range transmitter and receiver to
allow communication between them. Two different modes are used in the
presence of Base Station and without Base Station (Ad-hoc Networking)

3. WLAN consist of two main components: an Access Point
and wireless adapters. A bridge and an antenna can also be
used. An access point looks like an external modem with
two small antennae. Radio cards are also called WLAN
cards. The range of an 802.11b WLAN is typically 100 feet
and can be extended to several hundred feet by using an
antenna. Wireless bridges are similar to the wired bridges
and are used to connect two WLANs.

4. Figure: Architecture of wireless
Networks

5. AP (Access Point)
BSS (Basic Service Set)
ESS (Extended Service Set)
Three transitions take place between mobile hosts in wireless networks. No
transition which indicates stationary or mobile hosts moves only within BSS. In
BSS transition, Stations moves from one BSS to another BSS in same ESS
while in ESS transition, Station moving from BSS in one ESS to BSS within
another ESS

6. The various kinds of services provided are as follows:
Distribution systems Services (DSS)
· Association: Moving station associates with access point.
· Re-association: Moving station when enters in range of another
AP, he associates with new access point.
· Dis-association: When moving from one BSS to another BSS, old
association between mobile host and old AP get lost.
· Distribution: Data transfer from one mobile host to another within
single ESS.
· Integration: Integration of wireless technology with wired network.

7. Station Services (SS). The various services provided are Authentication
(Open system or Shared Key). De-authentication, Privacy and Data
delivery
The various managements frames used are:
· Authentication Frame
· Deauthentication Frame
· Association request and response frame
· Re-association request and response frame
· Disassociation frame
· Beacon frame
· Probe request frame.

8. Refered from :
https://sites.google.com/site/avicodes/notes/advance-computer-network/acn-
unit2/wireless-networks-wireless-communication-basics-architecture-mobility
-management-wireless-network-protocols
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