wlan -refined

Introduction to wireless networks: 

Introduction to wireless networks Broad band local access done using WLANs and WPANs. 3G systems is used for distribution systems for wirless local access. Standarizaition activity done in two camp. 1. IEEE 802.11 - conncection less data oriented computer communication. 2. JIPERLAN 2 for connection based WLAN addressing voice oriented cellular telephony. MAC layer settled into different physical layer to support higher data rates. HIPERLAN 2 standards uses same PHY layer as IEEE 802.11a. it supports cellular telephone industry for tariff, integration with exisiting cellular systems and providing QoS.

What is IEEE 802.11?: 

What is IEEE 802.11? IEEE 802.11 first WLAN std. Std zion activity started in 1987 as a part of 802.4 under the group member IEEE 802.4L it is counter part of IEEE 802.3 , 5 its motivation is to factory application to control and communication. In 1994, IEEE 802.4L is renamed as IEEE 802.1. PHY and MAC layer is defined for WLANs. first std for 1 -2 Mbps data rate support. completed in 1997 and supports to DSSS, FHSS and diffused infrared (DSIR) PHY layers. New PHY layer supporting 11Mbps using CCK - IEEE 802.11b 54Mbps using OFDM -IEEE 802.11a All IEEE 802.11, a, b are supports of CSMA/CA in MAC layer for contention data, RTS/CTS for hidden terminal problem. optional mechanism called PCF (Point co-ordination function) to time bounded applications.

Slide 4: 

WLAN std supports for infrastructure std through AP. ad hoc operation using peer to peer communication between terminals. it supports to define for systematic approach of wireless wideband local access. it needs to support for mobility and security. it depends on limitations on BW and frequency regulations. suffers from location dependent multipath fading. subject to interference from other radio and non radio devices. it has structure of connection management support, link reliability management, power management. there is no PHY layer boundary.

IEEE 802.11 : 

IEEE 802.11 First defined service PHY and MAC layer specification is defined for connection less service. transport and network layer accommodates IEEE 802.11 MAC layer. TCP/IP hosts all connection less applications. (web access, e-mail, FTP, telnet) it works over all MAC layer of the IEEE 802.11 IEEE 802.11 does not need to define service

Requirements: 

Requirements single MAC to support multiple PHY layers. mechanism to allow multiple overlapping networks in the same area. Provisions to handle the interference from other ISM band radios and micro wave ovens. mechanisms to handle hidden terminals Pbm. options to support time bounded services. provisions to handle privacy and access control.

PHY layer solutions : 

PHY layer solutions DSSS solution for IEEE 802.11 is based on waveLAN FHSS solution is highly affected by RangeLAN. ii may be affected by DFIR std.