Wireless NetworksWireless NetworksStandards and Protocols

802.11 & 802.11x Standards802.11 & 802.11x Standards

802.11 and 802.11x refers to a family of specifications developed by the IEEE for wireless LAN (WLAN) technology.

802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients.

The IEEE accepted the specification in 1997.

802.11 standards in the OSI model802.11 standards in the OSI model

There are several specifications in There are several specifications in the 802.11 family:the 802.11 family:

802.11802.11 — applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).

802.11a802.11a — an extension to 802.11 that applies to wireless LANs and provides up to 54-Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing encoding scheme rather than FHSS or DSSS.

802.11b802.11b (also referred to as 802.11 High Rate or Wi-Fi) — an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1-Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.

DSSS & FHSSDSSS & FHSS

In direct sequence spread spectrum (DSSSdirect sequence spread spectrum (DSSS), the stream of information to be transmitted is divided into small pieces, each of which is allocated across to a frequency channel across the spectrum. A data signal at the point of transmission is combined with a higher data-rate bit sequence (also known as a chipping code) that divides the data according to a spreading ratio. The redundant chipping code helps the signal resist interference and also enables the original data to be recovered if data bits are damaged during transmission.

Frequency hopping Frequency hopping is one of two basic modulation techniques used in spread spectrum signal transmission. It is the repeated switching of frequencies during radio transmission, often to minimize the effectiveness of "electronic warfare" - that is, the unauthorized interception or jamming of telecommunications. It also is known as frequency- hopping code division multiple access (FH-CDMA). Frequency hopping requires a much wider bandwidth than is needed to transmit the same information using only one carrier frequency.

DSSS & FHSSDSSS & FHSS

802.11e802.11e — a wireless draft standard that defines the Quality of Service (QoS) support for LANs, and is an enhancement to the 802.11a and 802.11b wireless LAN (WLAN) specifications. 802.11e adds QoS features and multimedia support to the existing IEEE 802.11b and IEEE 802.11a wireless standards, while maintaining full backward compatibility with these standards.

802.11g802.11g — applies to wireless LANs and is used for transmission over short distances at up to 54-Mbps in the 2.4 GHz bands.

802.11n802.11n — 802.11n builds upon previous 802.11 standards by adding multiple-input multiple-output (MIMOMIMO). The additional transmitter and receiver antennas allow for increased data throughput through spatial multiplexing and increased range by exploiting the spatial diversity through coding schemes like Alamouti coding. The real speed would be 100 Mbit/s (even 250 Mbit/s in PHY level), and so up to 4-5 times faster than 802.11g.

Wireless ProtocolsWireless Protocols

WEPWEP

WEP - Wired Equivalent Privacy◦Short for Wired Equivalent Privacy, a security

protocol for wireless local area networks (WLANs) defined in the 802.11b standard.

WAPWAP

WAP - Wireless Application Protocol◦A secure specification that allows users to

access information instantly via handheld wireless devices such as mobile phones.

WEP vs. WAPWEP vs. WAP

The Differences Between WEP and WPA◦WPA has been a mainstream technology for years

now, but WEP remains a standard feature on virtually every wireless router on store shelves today. When using a wireless access point or router it is

important to remember that if you can send information from one device and receive it at another, anyone else within range might also be able to receive it. When protecting data send via wireless, security and protection is offered through encryption schemes that come with your wireless hardware you can enable.

WEP vs. WAPWEP vs. WAP

WEP's Major Weakness◦WEP's major weakness is its use of static

encryption keys. When you set up a router with a WEP encryption key, that one key is used by every device on your network to encrypt every packet that's transmitted. But the fact that packets are encrypted doesn't prevent them from being intercepted, and due to some esoteric technical flaws it's entirely possible for an eavesdropper to intercept enough WEP-encrypted packets to eventually deduce what the key is.

WEP vs. WAPWEP vs. WAP

Wi-Fi Protected Access (WPA) Address WEP's Shortcomings◦ WPA aims to provide stronger wireless data encryption than WEP, but not

everyone has or was able to jump onboard with the new wireless encryption technology. In order to use WPA all devices on the network must be configured for WPA.

◦ If a device is not configured for WPA, it will usually fall back to the lesser WEP encryption scheme, enabling the wireless devices to communicate on the network. The technology was designed to work with existing Wi-Fi products that have been enabled with WEP (i.e., as a software upgrade to existing hardware), but the technology includes two improvements over WEP: Improved data encryption through the temporal key integrity protocol temporal key integrity protocol (TKIP). TKIP

scrambles the keys using a hashing algorithm and, by adding an integrity-checking feature, ensures that the keys haven't been tampered with.

User authentication, which is generally missing in WEP, through the extensible extensible authentication protocol authentication protocol (EAP). WEP regulates access to a wireless network based on a computer's hardware-specific MAC address, which is relatively simple to be sniffed out and stolen. EAP is built on a more secure public-key encryption system to ensure that only authorized network users can access the network.