TS 341/Ts643name: Xiaolan Rong

TS 341/TS643Name: Xiaolan Rong

Networking Technologies

Fall, 2008Date: 11/09/08

Anthony Pupello, Instructor

IEEE 802.11

IEEE 802.11 is the original wireless standard created by Institute of Electrical and Electronics Engineers in 1997. It is mainly used for data transmission between users in WLAN (Wireless Local Area Network). IEEE 802.11 is the standard defining mainly Physical layer and Datalink Layer in OSI (Open Systems Interconnect) Model. It is defined within the protocolarchitecture developed as an IEEE 802 standard,consisting of three layers: LLC (logical link control), MAC (media access control), and physical (Stallings, 2004).In Physical layer, IEEE 802.11 defines three physical media, DSSS (Direct-sequence spread spectrum), FHSS (Frequency-hopping spread spectrum) and Infrared.The maximum speed of 802.11 for sending and receiving data is only 2Mbps. It uses 2.4 GHz band.In order to ensure the good quality of communication, this standard is base on CSMA/CA (Carrier Sense Multi Access/Collision Avoidance).

With the development of network technology, the transmission speed and distance 802.11provides can not meet the need of users any longer. Therefore, IEEE expandsIEEE 802.11 to the following iterations.

IEEE 802.11b

802.11b is one of the most popular WLAN standards for commercial products currently.It is an extension of 802.11. 802.11b uses 2.4GHz band.Maximum data transmission rate is 11 mbps and the real speed might be loweredto 5.5 mbps according to the distance and the signal strength. 802.11b is based on DSSS(Direct-Sequence Spread Spectrum) scheme. Ithas about seven times therange of 802.11a (Kapp, 2002).Although 802.11b is widely used, the data rate is low, far to meet the need of a high-speed LAN.

IEEE 802.11a

802.11a was released in 1999.The maximum transmission speed is able to reach 54mbps. It is a specification for high speed WLAN. 802.11a uses 5GHz band.It uses OFDM –multicarrier modulationscheme, similar to FDM (frequency-division multiplexing), using multiple carrier signalsat different frequencies, sending some of the bits on eachchannel.802.11a has 12 nonoverlapped channels. Eight of them are used indoors and four are used for point to point transmission.

802.11a is the third generation standards after 802.11b because 802.11a products did not get on the market until 2001 when 802.11b had been in widespread use. Therefore, 802.11a is not popular in the market. Since the physics behind them are different (throughputand range), 802.11a technology is not compatible with 802.11b. 802.11a cannot replace 802.11b one for one.

IEEE 802.11g

802.11g is the extension of 802.11b. It is another widely used standard in products. Transmission speed is 54 mbps, the same as 802.11a. 802.11g uses 2.4 GHz band like 802.11 b, so 802.11g and 802.11b is compatible with each other.But the difference between themis that 802.11g uses OFDM and DSSS, and 802.11b uses DSSS only.Additionally, when we use 802.11b data rate, the lower one, 802.11b devices or 802.11g devices can operate on different standard access points. They are compatible with each other.

IEEE 802.11n—the latest iteration

The formal802.11n standard is expected to be published in 2009. Draft 5.0 was approved in July 2008. With the latest technology, the transmission speed is expected to reach 540mbps. It will be much faster than 802.11b and 802.11g. 802.11nwill enhance data rate, supportMIMO (Multi-Input and Multi-Output) and increase transmission range greatly. Greater bandwidth, higher data rate, shorter range are the major features of 802.11n.

Because 802.11n technologyis able to provide a good foundation for commercial products, some enterprises cannot wait for the final standard and have started to use802.11n technology.802.11n routers have been on the market.

My Choice for settling a WLAN

If I am settling a network, I will choose 802.11g. This standard is developed fully and backward compatible with 802.11b. The features of 802.11g,fast maximum speed and comparatively low cost are the points I concern most. Besides,good signal range and not easily obstructed are also good points of 802.11g technology.

For tech savvy, 802.11n might be their choice. Although 802.11n is more expensive, the fast maximum speed and good resistant to signal interference would definitelyattract people’s attention.Besides, the latest 802.11n product should be backward compatible with other standard products. Why not choose the most advanced technology? However, 802.11n standard is not finalized.We do not have enough time to observe its performance. There might be some potential problems to be found out. Troubleshooting period for any new technology is an unexciting process. I just do not want to be a guinea pig in the lab.

Do not forget about the Security Issues

Talking about WLAN, I have to mention the security issues.When I log on some WLAN, usually a warning window pops up first, saying that do not reveal your credit card information; anydevice on this network might get the information you transmit over. I felt a little bit scared when I got this message for the first time.Therefore, I am thinking the security of WLAN must be a critical issue of WLAN.

On Wired LAN, no matter you want to send or receive data, you have to physically connect your device to the network. In another word, the behavior of connecting can be observed. On WLAN, if your device is in radio range, data transmission can be carried out by your device.The conduct of connection is invisible. To some extent, it is hard to detect illegal access points. 802.11standardsare weak in dealing with security issues.

Mutual authentication, encryption and intrusion tools are mainly used to protect a WLAN. Intrusion detection system (IDS)is one of important intrusion tools.If you use the latest standard 802.11n to settle a network, the IDS in use now would be disabled, because most of the IDS support 802.11a and 802.11b. It means if you use 802.11n, you have to install the IDS supporting 802.11n on devices as well so that it is able to perform security checking work and find out illegal access points in time.It means extra cost for settling this WLAN.

WLAN securitytechnology is getting mature. So is WLAN standards. I believe efficient safe networks will get into our daily life sooner or later.

References:

Kapp, Steve.2002. 802.11:Leavingthe Wire Behind. IEEE INTERNET COMPUTING.

Stallings, William. 2004. IEEE 802.11:Wireless LANsfrom a to n. Published by the IEEE Computer Society.