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Wireless
Wednesday, December 06, 2006
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.
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.
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. |
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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