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Wireless

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PCQ Bureau
New Update

While there has been a lot of talk about wireless technologies and

specification in the past few years, not much has become commonplace. A few have

been the pre-n and n specifications, WPA, WiMaX, VoWLAN etc. Let us find out

where they have reached at the end of yet another year. The latest entry to the

bandwagon of WiFi standards is 802.11n. This standard is still not out in the

market yet but has great hype surrounding it for two reasons. One, it is

supposed to remove the limitation of WiFi networks from being slow for

enterprise needs. For instance, 802.11g is the fastest standard today that gives

a shared throughput of 54 Mbps and today when gigabit networks have become

mainstream, this speed is not sufficient.

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The second reason for this hype is the release of pre-N devices in the

market, which have so far demonstrated a great performance in favor of the

802.11n. Now, let's understand what these technologies are promising and what

technologies are at work behind the stage to make them happen.

802.11n and pre-n



The projected time for release of this standard is July 2007. The 802.11n will
add MIMO over the existing 802.11 standards and increase the physical layer

throughput of the device. This would mean adding multiple antennas for

transmitting and receiving signals simultaneously. This increases data

throughput with spatial multiplexing and increasing range by using the spatial

diversity. So watch out for this one.

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After the announcement of first draft of 802.11n this year, quite a few

companies had started manufacturing cards and APs based on it. The devices gave

better speed in 100 to 270 Mbps bandwidth range, quite high compared to what we

get with 802.11g or other equivalents. But there are some catches.

Being based on the draft of a technology, these products do not give you

assured compatibility with upcoming the 802.11n standard. Also, these devices

have shown interoperability problems with older technologies like 802.11a/b/g.

But because of the throughput, pre-n devices have risen to become the hottest

range of Wi-Fi products this year.

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WPA and 802.11i



Wi-Fi networks were not very secure by birth. Thus came by WEP (Wired Equivalent
Privacy) as the first level of security. But its implementation saw major

drawbacks as it could easily be cracked. To solve this issue, WPA was released.

WPA uses the same cipher called RC4, as used in WEP, to encrypt the data. It is

far more secure than WEP. The additional layer of security is provided by TKIP,

which works by creating



multiple keys that are based on a master key. The key changes randomly after
every 10,000 packets-quick enough to fight against statistical methods of

analyzing the cipher (the mechanism which is used to crack WEP). So the cracker

cannot capture and decode it.

An higher layer of security is provided by 802.11i or WPA2. It is supposed to

be the de-facto security standard for any Wi-Fi network. WPA2 works in a manner

similar to WPA. For instance, it uses the mechanism of randomly changing the key

to prevent it from statistical analysis method but uses a more sophisticated

cipher to encrypt the data, called AES-CCMP. Here, AES stands for Advanced

Encryption Standard. WPA2 is now available with most of the well-known OSs. For

instance, Win XP SP2 or later versions have the WPA2 update. Additionally, this

mechanism is also introduced in the latest versions of MAC and Linux distros.

Voice over WiFi (VoWLAN)
Last year saw immense developments in VoIP,

be it the technology, its implementation or production of VoIP related

hardware and software. The technologies have matured and the prices have

come down.

With the trend catching up, there are some new mobile

devices that give you VoIP over WiFi.

The technology involved is no miracle, because

practically whatever you can run on LAN can also be atop WiFi if the same

protocols such as TCP/IP or SIP are used. But the innovation here is in

the form of products--now we have smartphones that can seamlessly switch

between GSM and VoWLAN depending on the availability. So if you want to

connect to a coworker sitting in the same WLAN network, you can switch to

VoWLAN and dial the number instead of dialing via GSM service provider.

While these devices are already being used globally, in

India the penetration is still very low.

This is because the Indian laws for VoIP deployment

(Telegraphic Act 1883 and Telegraphic Wireless Act 1935) are not very

clear on this and prohibit quite a few things even today, such as calling

to a PSTN or a mobile number from a VoIP network. We hope that this law is

soon going to get amended because of the constant pressure of ISPs and the

increase of outsourcing market in India, which requires a low cost

communication solution.

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WiMAX



Till now, we have talked about different Wireless LAN technologies but here is
one wireless technology, which seems to have a great potential. Just like most

new technologies, this one is also not yet available in India but accepted

globally. The WiMAX standard or IEEE 802.16a is an extension to Wireless MAN

(Metropolitan Area Network) Air Interface standard for MAN (802.16). It is

created to operate in the range of high frequency band from 10 to 66 GHz, while

802.16a will operate in lower frequency band range of 2 to 11 GHz band. Here the

main change in 802.16a is the absence of requirement for line of sight. This is

possible because WiMAX directional antenna can transmit signal to any cellphone

tower even outside direct line-of-sight. The signals can even penetrate tall

buildings and trees. 802.16a is capable of transmitting signal across 50 km and

has a max data transfer rate of 70 Mbps for hundreds of users. Reliable

transmission is achieved with forward error correction technique, and uses

Triple-DES encryption for security.

Buzz from last year



Bluetooth: Most widely use wireless technology for short range and personal
networks. The 2.0 version is to operate in the same frequency band (2.45 GHz) as

the previous 1.2 version. An important change in its specification is that a

Bluetooth 2 enabled device offers a peak data rate of up to 3 Mbps while 1.2

specification offered peak rate of just 1 Mbps (723 Kbps). The increased

throughput will enable large file transfer and fast. Bluetooth 2.0 devices

consume less power, and can transfer data across 100 meters max. Version 2.0

comes with improved QoS for better AV streaming, and is backward compatible with

1.X versions. There's support for multicast so that one Bluetooth device can

simultaneously transfer data to many Bluetooth devices, eg a CD player sending

music to multiple headsets.

ZigBee: If you interested in low-powered, short distance, and

low-speed (just 250 Kb/sec) connections, think of the ubiquitous bee-the

Motorola invention 'ZigBee'. ZigBee also uses the 2.4 GHz free to use radio

band and is suited to tasks where other transceivers would quickly fizzle out.

There will soon be a nest of ZigBees that will form their own peer-to-peer 'meshes'.

Wireless USB: Wireless USB (WUSB) is an innovation of the USB

Implementers Forum, it is meant for short-range high-bandwidth connection for

USB devices. WUSB is developed on the WiMedia Alliance's Ultra-WideBand (UWB)

common radio platform, This platform is capable of sending data at around 480

Mbit/s speed at distances up to 3 meters and 110 Mbit/s at up to 10 meters. It

operates in the range of 3.1 to 10.6 GHz. Still to see the products for this.

Implementation scenario
Setting up Wi-Fi network
Just like any other implementation, the key

to a successful wireless implementation is also good planning. Following

are six points which one should look for while deploying a Wi-Fi network

Step 1: Physical site map-Collect basic

information about the site where you're to deploy the wireless network-in

terms of the location, users, density of users, etc. This helps determine

how many wireless APs you'll need to get the best performance. The general

rule of thumb is that one wireless AP using the 802.11g (54Mbps shared)

standard can take up to 20 to 30 users if being used primarily for sharing

files and Internet access over the network. The placement of the APs is

equally important. Before you install them, have a map of the location

ready.

Step 2: Centralized watch-To manage all your

APs centrally, use the APs or wireless devices from a single vendor and

always enable SNMP read/write on both public and private domain (with

password protection). This lets you manage and monitor them efficiently

from one place.

Step 3: Antenna configuration-If you are

mounting an AP on a wall, make sure you have changed the antenna settings

from bi-directional to uni-directional so that the wireless signals don't

bounce of the wall.

Step 4: Deploying APs-While deploying an AP,

affix them on the ceiling. By placing them at a height, they won't get

affected by the office cubicals, walking employees, and other obstructions.

Step 5: Logical Site Map-You also need to

monitor user behavior, interference from other devices on the network, and

security. You can use tools like Wavemon and Kismet for this.



Step 6: Identifying black spots-There are lots of products, devices and
elements that act as WiFi killers. So while building your WiFi network you

have to be very cautious and see whether these devices are out of the RF

path of your network or not. The interference can come from electric

wiring, Bluetooth devices or other devices that work on the same frequency

spectrum such as cordless cameras, phones, etc.

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