2008-01-21
Standard of Draft?
802.11n is a proposition to amendment to the 802.11 standard. And it is about higher speed i the wireless network, compared to todays standard 802.11a/b/g.
As 802.11n not yet is aproved by IEEE it is not yet a standard. However IEEE has launched Draft 2.0 and Draft 3.0. These are approved with good majority within IEEE and the hardware is set to the level where most likely only a software upgrade will be neede to fulfill the final standard.
Pros and cons
802.11n menas higher speed in the network. Higher speed means that more people will use the network. 802.11n will also expand the reach and improve throughput for the radio signals. Some will use this to reduce the number of access points, but bare in mind to track capacity per user. Disadvantages will be the channel planning as 802.11n uses the double channel width 40 MHz, and more power consumption in the access points.
Should I purchase products now or wait until the standard is finalized?
Wi-Fi Alliance has since Juni 2007 worked to control the interoperability between differnet vendors products and certifies these. It is the same process that were used for 802.11b and g. This is important to ensure that the customers can invest in the new products. We can recommend our reseller partners to start with these products today as they will fulfill the new standard when it is finalized and they will work in integrated environments. The probality that IEEE will make changes in this stage is very small. Just be sure to purchase products that are certified by WiFi Alliance.
When will the standard be finalized?
In September 2007 the Draft 3.0 was passed with an 83.4% approval. Draft 4.0 is expected in March 2008. Just now it looks like Task Group n will release the final version in March 2009 and that it will be published in July 2009.
What is included in 802.11n
802.11n builds on all past appendixes to the 802.11 standard, including the improvement in the MAC (Medium Access Control) which is included in the 802.11e for QoS and power save mode. 802.11n contains several new technlogies which are inteconnected. In addition there are a number of technologies which the vendor can choose to use. Compulsary technologies include Spatial Multiplexing, and Frame Aggregation.
Optional technologies includes the wider bandwidth of 40 MHz kanalbredd, Transmit Beam Forming and others.
Spatial Multiplexing Frame Aggregation
Which speed do I get with 802.11n?
The proposal specification from IEEE describes that the standard should be handling 100 Mbps througput. In the Draft 3.0 it is specified which speeds could be included. These depends on several things such as how many antennas are included in the MIMO antenna. Minimum 2 and max 4 antennas can be used. And the channel width is affected. If you can use 40 MHz channel width you get double capacity, but limitation in the number of Access Points. One possibility is to use clients which supports the 5GHz band and there use wider channels for better spread.
The maximum speed that can be reached under optimal conditions with equipment that supports all incleded options is 600 Mbps. How it works is explained
Increased power consumption in the 802.11n access points
Access punkter with support for 802.11n consume more power that todays access points, aprox 17–25 W. The result is that they can not use all the new functionality and the radiated power if they use PoE. IEEE is in the process of bringing forward a new standard for Powewr-over-Ethernet which gives up to 30 W over PoE This new standard 802.3a is estimated to be ready in the beginning of 2009.
Important questions about 802.11n products
If you consider to invest in a new 802.11n network there is a number of issues to consider. Below is a list of some of the most important:
- Do I get the requested speed with this vendors products?
- Do I need to change my infrastructure due to increased traffic flow?
- Do I need a new wireless switch?
- Which possibilities is there to feed voltage to the AP's with more power?
- Do I have to upgrade my PoE switches?
- Is this solutions certified by Wi-Fi Alliance and is it upgradable to 802.11n when it is ready?
- Is there any planning tool which supports the new access points?
Please contact NoWire for more information
Tel: +46 8-474 66 40
E-mail: info@nowire.se