Wireless Ad Hoc and Sensor Networks

26 Wireless Ad Hoc and Sensor NetworksInfrared physical layer: This PHY provides 1 Mbps with optional 2 Mbps.The 1-Mbps version uses pulse position modulation (PPM) with16 positions (16-PPM) and the 2-Mbps version uses 4-PPM.1.4.3 IEEE 802.11 VersionsIEEE 802.11b: An appendix to the existing 802.11 protocol “HigherSpeed Physical Layer Extension in the 2.4GHz Band” was publishedin 1999 (IEEE 802.11b 1999). It is known as 802.11b standard. Thisstandard working in 2.4-GHz frequency provides 5.5-Mbps and11-Mbps data rate, in addition to the existing 1 Mbps and 2 Mbpsprovided. This extension uses 8-chip complementary code keying(CCK) as the modulation scheme. The IEEE ratified the IEEE 802.11specification in 1997 as a standard for WLAN. Current versions of802.11 (i.e., 802.11b) support transmission up to 11 Mbps. Wi-Fi, asit is known, is useful for fast and easy networking of PCs, printers,and other devices in a local environment, for example, the home.Current PCs and laptops as purchased have the hardware to supportWi-Fi. Purchasing and installing a Wi-Fi router and receiversis within the budget and capability of home PC enthusiasts.IEEE 802.11a: Another appendix to the existing 802.11 (IEEE 802.11astandard 1999) known as IEEE 802.11a was published in 1999. Thestandard was called “High-Speed Physical Layer in the 5GHzBand.” This standard allows up to 54 Mbps using 5-GHz frequencyrange. At these high speeds, multipath delay is a major problem.A new modulation method, called coded-orthogonal frequencydivisionmultiplexing (COFDM), must be used to overcome thismultipath delay problem.IEEE 802.11g: In February 2003, IEEE 802.11g, 54-Mbps extension to802.11b wireless LANs, gained working group approval. IEEE802.11g, which is called “Wireless LAN Medium Access Control(MAC) and Physical Layer (PHY) Specifications: Higher SpeedPhysical Layer (PHY) Extension to IEEE 802.11b,” will boost wirelessLAN speed to 54 Mbps by using OFDM (orthogonal frequencydivision multiplexing). The IEEE 802.11g specification is backwardcompatible with the widely deployed IEEE 802.11b standard.1.4.4 IEEE 802.11 Network TypesIEEE 802.11 recognizes two types of networks. They are ad hoc networksand extended set networks. An ad hoc network doesn’t require any existing