Essay - IEEE 802.11 and Bluetooth Introduction Wireless Technology Has Developed a...

IEEE 802.11 and Bluetooth

Introduction

Wireless technology has developed a large way from its infancy and is fast becoming the latest trend in communication. Wireless LANs have added an entirely new dimension to the communication sector. The advent of cellular technology, infrared and spread spectrum radio services have bought about a huge change to our world of communication and wireless technology ***** materialized our dream of a mobile workforce. Today there is no single standard in the industry and there are different wireless technologies available. Let us ***** a brief outlook of the 'IEEE 802.11' and '*****', two ***** the important wireless LAN technologies.

IEEE 802.11 Protocol

The IEEE 802.11 (First adapted in 1997) is primarily a st*****ard developed to provide time bound and asynchronous wireless services. The MAC layer is meant to h*****le ***** physical *****s with distinct medium and transmission characteristics. The standard uses 2.4 GHz ISM band and a minimum data transfer rate of 1 Mbits /s. IEEE 802.*****1 specifies ***** ***** and the medium access layer standards in particular to the ***** LAN's. IEEE 802.11 has seamless ********** with other standards for wired ne*****rks. The Data link layer and the Logical Link ***** control ***** aspects pertaining ***** different ********** of ***** media. The MAC layer is concerned with three main tasks namely medium access, data fragmentation and encryption while the Physical layer takes care of the modulation, encoding and decoding ***** the signals. Let us study these two layers in a little det*****il.

Physical Layer

***** protocol supports ***** types of physical layers based on two kinds of radio ***** one ***** transmission. The ***** includes channel detection provision, which (CCA) is *****ed for medium *****.

***** Hopping Spread Spectrum

***** 802.11 includes Frequency hopping ***** spectrum technique whereby ***** on *****e channel of radio spectrum is transferred to another ***** as ***** is transferred through the network. [Raymond P. Wenig, 57] Currently for a 1 Mbit data transfer a 2 level FSK (Frequency Shift Keying) is used as the standard. Each data frame in the physical layer cons*****ts of two ma***** parts namely the physical layer convergence pro*****col (preamble and the header) ***** the payload. The PLCP is al*****s transmitted at a ***** speed of 1 Mbits/s while data part can vary from ***** Mbit/s to ***** Mbit/s. An 80-bit Synchronization pattern ***** used to synchronize the receivers with the transmitter once ***** receiver gets a line clear signal from the CCA. (Clear channel assessment signal). This is followed by a start frame delimiter (16 bits), which helps to synchronize the individual frames of data. ***** next part PLW (PLCP_PDU length word) contains information regarding the size of the payload. Next part of the frame is the PSF field (PCLP signaling Field), which indicates the actual data ***** of the payload. (Either 1 or 2Mbit/s). Furtherm*****e data ***** scrambled using the polynomial equation s (z) = z^7 +Z^4+1. The field immediately before the actual payload i***** the HEC (Header Error Check) [Jochen Sch*****ller, 171]