Thursday, August 21, 2008

802.11n and 4G...

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'."

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