5. a. List the various Wi-Fi standards available for building a wireless network

Question

5. a. List the various Wi-Fi standards available for building a wireless network. Compare and contrast two of the popular standards.

b. Let’s assume you are the IT manager of your company, which employs the IEEE 802.11b standard for the wireless infrastructure and supports a data rate of 11 Mbps. Your company wants to expand the network but also wants the new network to support a higher data rate. In addition, your company is planning to run some servers on the new network and the users need to have the ability to access these servers from the old network. What wireless standard would you recommend for the new network? Please justify your choice. (Points : 3)               

Explanation / Answer

b)

>The IEEE 802.11b standard is the most popular and widely implemented of the 802.11 family standards, for reasons including its early availability and the price of supported products.
>802.11b is a physical layer standard that specifies operation in the 2.4 GHz industrial, scientific, and medical (ISM) unlicensed frequency band, using the direct-sequence spread spectrum (DSSS) modulation technique.
>The number of channels the 2.4 GHz spectrum provides varies by country according to local regulatory restrictions.
>The FCC defines 11 channels for use in the US; 13 channels are available for use in most of Europe and 14 are available in for Japan.
>The channels overlap one another, since the centers of adjacent channels are separated by only 5 MHz.
>As a result, only three of the channels in the 2.4 GHz band are non-overlapping.
>Devices that use overlapping channels within range of each other will tend to interfere with one another’s operation.
>Interference problems are avoided only by configuring adjacent access points to operate on non-overlapping channels.
>The limited number of available channels in the 2.4 GHz band places an inherent restriction on the capacity of an 802.11b network. (By comparison, the 802.11a standard uses the 5 GHz spectrum, which has up to 19 non-overlapping channels depending on country regulatory rules governing use of the wireless spectrum.)
>The 802.11b standard defines a maximum data rate of 11 Mbps, which provides a realistic maximum usable throughput of about 4-6 Mbps under normal conditions. (Remember that data rate is not identical to throughput; access points must handle protocol overhead, along with management and control frames that must be transmitted at the lowest supported data rate)
>When signal quality becomes an issue, the 802.11b device uses a technique called adaptive rate selection to scale back the rate to 5.5/2/1 Mbps. Lower data rates use less complex methods of encoding the data. Consequently, they are less likely to be corrupted by interference or signal attenuation.

>Wireless networking is becoming increasingly important to businesses, both small and large. Use this chart to make sense out of all the wireless local-area network standards.
>Use this wireless networking standards chart to get quick information to help you differentiate between the available wireless networking standards and choose which standard might be the right fit for your business.


Standard Data Rate Modulation Scheme Security Pros/Cons & More Info

IEEE 802.11   Up to 2Mbps in the 2.4GHz band   FHSS or DSSS   WEP & WPA   This specification has been extended into 802.11b.

IEEE 802.11a (Wi-Fi)   Up to 54Mbps in the 5GHz band   OFDM   WEP & WPA   Products that adhere to this standard are considered "Wi-Fi Certified." Eight available channels. Less potential for RF interference than 802.11b and 802.11g. Better than 802.11b at supporting multimedia voice, video and large-image applications in densely populated user environments. Relatively shorter range than 802.11b. Not interoperable with 802.11b.

IEEE 802.11b (Wi-Fi)   Up to 11Mbps in the 2.4GHz band   DSSS with CCK   WEP & WPA   Products that adhere to this standard are considered "Wi-Fi Certified." Not interoperable with 802.11a. Requires fewer access points than 802.11a for coverage of large areas. Offers high-speed access to data at up to 300 feet from base station. 14 channels available in the 2.4GHz band (only 11 of which can be used in the U.S. due to FCC regulations) with only three non-overlapping channels.

IEEE 802.11g (Wi-Fi)   Up to 54Mbps in the 2.4GHz band   OFDM above 20Mbps, DSSS with CCK below 20Mbps   WEP & WPA   Products that adhere to this standard are considered "Wi-Fi Certified." May replace 802.11b. Improved security enhancements over 802.11. Compatible with 802.11b. 14 channels available in the 2.4GHz band (only 11 of which can be used in the U.S. due to FCC regulations) with only three non-overlapping channels.

IEEE 802.16 (WiMAX)   Specifies WiMAX in the 10 to 66 GHz range OFDM   DES3 and AES Commonly referred to as WiMAX or less commonly as WirelessMAN or the Air Interface Standard, IEEE 802.16 is a specification for fixed broadband wireless metropolitan access networks (MANs)

IEEE 802.16a (WiMAX)   Added support for the 2 to 11 GHz range.   OFDM   DES3 and AES   Commonly referred to as WiMAX or less commonly as WirelessMAN or the Air Interface Standard, IEEE 802.16 is a specification for fixed broadband wireless metropolitan access networks (MANs)

Bluetooth   Up to 2Mbps in the 2.45GHz band   FHSS   PPTP, SSL or VPN   No native support for IP, so it does not support TCP/IP and wireless LAN applications well. Not originally created to support wireless LANs. Best suited for connecting PDAs, cell phones and PCs in short intervals.

HomeRF   Up to 10Mbps in the 2.4GHZ band   FHSS   Independent network IP addresses for each network. Data is sent with a 56-bit encryption algorithm.   Note: HomeRF is no longer being supported by any vendors or working groups. Intended for use in homes, not enterprises. Range is only 150 feet from base station. Relatively inexpensive to set up and maintain. Voice quality is always good because it continuously reserves a chunk of bandwidth for voice services. Responds well to interference because of frequency-hopping modulation.
HiperLAN/1    Up to 20Mbps in the 5GHz band   CSMA/CA   Per-session encryption and individual authentication.   Only in Europe. HiperLAN is totally ad-hoc, requiring no configuration and no central controller. Doesn't provide real isochronous services. Relatively expensive to operate and maintain. No guarantee of bandwidth.
HiperLAN/2    Up to 54Mbps in the 5GHz band   OFDM   Strong security features with support for individual authentication and per-session encryption keys.   Only in Europe. Designed to carry ATM cells, IP packets, Firewire packets (IEEE 1394) and digital voice (from cellular phones). Better quality of service than HiperLAN/1 and guarantees bandwidth.
OpenAir   Pre-802.11 protocol, using Frequency Hopping and 0.8 and 1.6 Mb/s bit rate   CSMA/CA with MAC retransmissions   OpenAir doesn't implement any encryption at the MAC layer, but generates Network ID based on a password (Security ID)   OpenAir is the proprietary protocol from Proxim. All OpenAir products are based on Proxim's module.

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