The following IEEE
802.11 standards exist or are in development to support the creation of
technologies for wireless local area networking:
·
802.11a -
54 Mbps standard, 5 GHz signaling (ratified 1999)
·
802.11b -
11 Mbps standard, 2.4 GHz signaling (1999)
·
802.11c - operation of bridge
connections (moved to 802.1D)
·
802.11d - worldwide compliance with
regulations for use of wireless signal spectrum (2001)
·
802.11e - Quality of Service (QoS)
support (not yet ratified)
·
802.11F - Inter-Access Point Protocol
recommendation for communication between access points to support roaming
clients (2003)
·
802.11g -
54 Mbps standard, 2.4 GHz signaling (2003)
·
802.11h - enhanced version of 802.11a
to support European regulatory requirements (2003)
·
802.11i - security improvements for
the 802.11 family (2004)
·
802.11j - enhancements to 5 GHz
signaling to support Japan regulatory requirements (2004)
·
802.11k - WLAN system management
·
802.11l - skipped to avoid confusion
with 802.11i
·
802.11m - maintenance of 802.11
family documentation
·
802.11n -
100+ Mbps standard improvements over 802.11g (2009)
·
802.11o - skipped
·
802.11p - Wireless Access for the
Vehicular Environment
·
802.11q - skipped
·
802.11r - fast roaming support via
Basic Service Set transitions
·
802.11s - ESS mesh networking for
access points
·
802.11T - Wireless Performance Prediction
- recommendation for testing standards and metrics
·
802.11u - internetworking with 3G /
cellular and other forms of external networks
·
802.11v - wireless network management
/ device configuration
·
802.11w - Protected Management Frames
security enhancement
·
802.11x - skipped (generic name for
the 802.11 family)
·
802.11y - Contention Based Protocol
for interference avoidance
Wireless Standards - 802.11b
802.11a 802.11g and 802.11n
The 802.11 family explained
Home and business networkers looking to buy
wireless local area network (WLAN) gear face an array of choices. Many products
conform to the 802.11a, 802.11b, 802.11g, or 802.11nwireless
standards collectively known as Wi-Fi technologies. Additionally, Bluetooth and
various other non Wi-Fi technologies also exist, each also designed for
specific networking applications.
This article describes the Wi-Fi and related
technologies, comparing and contrasting them to help you make educated network
building decisions.
802.11
In 1997, the Institute of Electrical and
Electronics Engineers (IEEE) created the first WLAN standard. They called it 802.11
after the name of the group formed to oversee its development.
Unfortunately, 802.11 only supported a maximum network bandwidth of 2 Mbps -
too slow for most applications. For this reason, ordinary 802.11 wireless
products are no longer manufactured.
802.11b
IEEE expanded on the original 802.11 standard in
July 1999, creating the 802.11b specification. 802.11b supports
bandwidth up to 11 Mbps, comparable to traditional Ethernet.
802.11b uses the same unregulated radio
signaling frequency (2.4 GHz) as the original 802.11 standard. Vendors often prefer using these
frequencies to lower their production costs. Being unregulated, 802.11b gear
can incur interference from microwave ovens, cordless phones, and other
appliances using the same 2.4 GHz range. However, by installing 802.11b gear a
reasonable distance from other appliances, interference can easily be avoided.
Pros of 802.11b - lowest cost; signal range is good and not easily obstructed
Cons of 802.11b -
slowest maximum speed; home appliances may interfere on the unregulated
frequency band
802.11a
While 802.11b was in development, IEEE created a
second extension to the original 802.11 standard called 802.11a. Because
802.11b gained in popularity much faster than did 802.11a, some folks believe
that 802.11a was created after 802.11b. In fact, 802.11a was created at the
same time. Due to its higher cost, 802.11a is usually found on business
networks whereas 802.11b better serves the home market.
802.11a supports bandwidth up to 54 Mbps and
signals in a regulated frequency spectrum around 5 GHz. This higher frequency
compared to 802.11b shortens the range of 802.11a networks. The higher
frequency also means 802.11a signals have more difficulty penetrating walls and
other obstructions.
Because 802.11a and 802.11b utilize different
frequencies, the two technologies are incompatible with each other. Some
vendors offer hybrid802.11a/b network gear, but these products merely
implement the two standards side by side (each connected devices must use one
or the other).
Pros of 802.11a - fast maximum speed; regulated frequencies prevent signal interference
from other devices
Cons of 802.11a -
highest cost; shorter range signal that is more easily obstructed
802.11g
In 2002 and 2003, WLAN products supporting a
newer standard called 802.11g emerged on the market. 802.11g attempts to
combine the best of both 802.11a and 802.11b. 802.11g supports bandwidth up to
54 Mbps, and it uses the 2.4 Ghz frequency for greater range. 802.11g is
backwards compatible with 802.11b, meaning that 802.11g access points will work
with 802.11b wireless network adapters and vice versa.
Pros
of 802.11g - fast maximum speed; signal range is good and not easily
obstructed
Cons of 802.11g -
costs more than 802.11b; appliances may interfere on the unregulated signal
frequency
802.11n
The newest IEEE standard in the Wi-Fi category is
802.11n. It was designed to improve on 802.11g in the amount of
bandwidth supported by utilizing multiple wireless signals and antennas (called
MIMO technology) instead of one.
When this standard is finalized, 802.11n
connections should support data rates of over 100 Mbps. 802.11n also offers
somewhat better range over earlier Wi-Fi standards due to its increased signal
intensity. 802.11n equipment will be backward compatible with 802.11g gear.
Pros of 802.11n - fastest maximum speed and best signal range; more resistant to signal
interference from outside sources
Cons of 802.11n - standard
is not yet finalized; costs more than 802.11g; the use of multiple signals may
greatly interfere with nearby 802.11b/g based networks.
IEEE
802.11n is a proposed amendment to the IEEE 802.11-2007 wireless networking standard to significantly improve network throughput over previous standards, such as 802.11b and 802.11g, with a significant increase in raw (PHY) data rate from 54 Mbit/s to a maximum of 600 Mbit/s. Most devices today support a PHY rate of 300 Mbit/s, with the use of 2
Spatial Streams at 40 MHz. Depending on the environment, this may translate into a user throughput (TCP/IP) of 100 Mbit/s.
According to the book "
WI-Fi, Bluetooth, Zigbee and Wimax"
:
802.11n is the 4th generation of wireless lan technology.
- First generation (IEEE 802.11) since 1997 (WLAN/1G)
- Second generation (IEEE 802.11b) since 1998 (WLAN/2G)
- Third generation (802.11a/g) since 2000 (WLAN/3G)
- Fourth generation (IEEE 802.11n) (WLAN/4G)
The distinguishing features of 802.11n are:
- Very high throughput (some hundreds of Mbps)
- Long distances at high data rates (equivalent to IEEE 802.11b at 500 Mbps)
- Use of robust technologies (e.g. multiple-input multiple-output [MIMO]and space time coding).
In the N option, the real data throughput is estimated to reach a theoretical 540 Mbps (which may require an even higher raw data rate at the physical layer), and should be up to 100 times faster than IEEE 802.11b, and well over ten times faster than IEEE 802.11a or IEEE 802.11g. IEEE 802.11n will probably offer a better operating distance than current networks. IEEE 802.11n builds upon previous IEEE 802.11 standards by adding MIMO. MIMO uses multiple transmitter and receiver antennae to allowfor increased data throughput through spatial multiplexing and increased range by exploiting the spatial diversity and powerful coding schemes. The N system is strongly based on the IEEE 802.11e QoS specification to improve bandwidth performance. The system supports basebands width of 20 or 40MHz.
Note that there is 802.11n PHY and 802.11n MAC that will be required to acheive 540Mbps.
To achieve maximum throughput a pure 802.11n 5 GHz network is recommended. The 5 GHz band has substantial capacity due to many non-overlapping radio channels and less radio interference as compared to the 2.4 GHz band. An all-802.11n network may be impractical, however, as existing laptops generally have 802.11b/g radios which must be replaced if they are to operate on the network. Consequently, it may be more practical to operate a mixed 802.11b/g/n network until 802.11n hardware becomes more prevalent. In a mixed-mode system, it’s generally best to utilize a dual-radio access point and place the 802.11b/g traffic on the 2.4 GHz radio and the 802.11n traffic on the 5 GHz radio.
A lot of phones are coming with inbuilt WiFi (or 802.11 a/b/g) and this WiFi is a must on Laptops or they wont sell. The main difference in 802.11n, compared to previous generation of 802.11 is that there is a presence of MIMO. 802.11 family uses OFDM which is the same technology being adopted by LTE. The new LTE handsets will have advantage of easily integrating this 802.11n technology and the same
antennas can be reused. In fact the same is applicable for WiMAX as it supports MIMO and OFDM. Ofcourse we will have problems if they are using quite different frequencies as the antennas ore optimised to range of frequencies, this is something that has to be seen.
In the news:
MIT and a medical center based in Alabama are beginning to deploy faster wireless 802.11n access points from Cisco Systems Inc. In more than 100 buildings on MIT's Cambridge, Mass., campus, as many as 3,200 access points running older 802.11a/b/g protocols will be replaced with 802.11n devices in the next 12 to 16 months, said Chris Murphy, a networking engineer at the university. Murphy said MIT, with more than 10,000 students and 11,000 staff members, has a "very, very wide variety" of client devices, from handhelds to laptops. Many of the laptops probably support the 802.11n protocol, he said. Some MIT staffers have been using voice-over-IP wireless handsets and have experienced poor coverage with the older Wi-Fi technology, but they said they have had full signal strength within the range of the new 802.11n access points, he added. With 802.11n, the university could eventually provide IP television, which requires a lot of bandwidth, Murphy said.
Using 802.11n technology, Lapham said he was able to transmit a gigabyte of data in less than two minutes. Currently, the 370-bed medical center has about 450 access points on older protocols. Devices used on the wireless network include 180 laptops, which are used primarily for transmitting bedside patient data. The hospital also supports 100 VoIP wireless phones and a various medical devices.
Wi-Fi is expected to be available in 99 per cent of North American universities by 2013, according to research released by industry analyst ABI Research this week. Much of that penetration will be in the form of 802.11n equipment: higher education is clearly the number one market for early adopters of 802.11n, the company said.
ABI Research expects 802.11n uptake – which is today fairly small in the education market – to ramp up steeply to quite a high rate of penetration," said ABI Research vice president Stan Schatt. There are several reasons for this. ABI said many students now assume a campus Wi-Fi network as a given, and many of their shiny new laptops will be 'n'-compatible. Universities also have great bandwidth demands, as lecture halls may need to serve a large number of users with multimedia contention at any given time and 802.11n's greater speed and capacity can address that need. Moreover, said Schatt, "Universities are breaking new ground by using video over Wi-Fi in a number innovative ways. This is driving the adoption of high speed 802.11n. Students in the near future (at least the diligent ones) will be just as likely to watch their favourite professor's lectures on their laptops as they will be to view 'America's Next Top Model'."
