Summary and upgrade recommendations for 802.11N technology

Summarize the advantages of 802.11n technology, simply to improve the previous 802.11 devices in the following two aspects. The first is to use MIMO technology to achieve higher signal-to-noise ratio on the channel. The second is to improve the efficiency of wireless transmission and MAC protocol. These improvements have enabled the reliability of wireless transmissions to be improved both in terms of coverage and throughput rates.

Reliability

A larger signal-to-noise ratio for wireless link transmission means more reliable communication and higher data transfer rates. A higher signal-to-noise ratio means no more interference to disrupt the transmission. This means that more client access can be supported. Predictable coverage using the multi-spatial data stream technology provided by MIMO technology to eliminate the blind zone in the coverage area. Areas that were previously disturbed by multipath reflection signals can now be used to provide better communication.

Throughput rate

The significant improvement in 802.11n is to provide a higher data transfer rate (pure 11n mode) for applications. Even in a hybrid mode with a forward compatible vintage 802.11 device, 802.11n can provide a high throughput rate (below the pure 11n mode).

Suggestions for migrating to 802.11n

Migrating to the 802.11n standard, at least to the 802.11n draft, has already begun. 802.11N-enabled client devices, such as laptops, are also ready. After the draft 802.11n becomes the standard WLAN adapter for handheld and mobile devices, new client devices will appear within a few months. These client devices are fully compatible with existing 802.11a/b/g wireless access points and are identical to the operations of existing devices. Upgrading the current subset of network architectures to support 802.11n devices has been offing.

When migrating to a 802.11n network, you need to consider the following aspects. Due to the higher speed and more power requirements of the 802.11n wireless access point, the aspects to be considered in the upgrade process are not just wireless access points.

802.11n works in 2.4-ghz (802.11B and 802.11g) and 5-ghz bands. The plan for each band is to be carried out separately because the requirements for each band are different.

The bandwidth of the 2.4-ghz band is only 100MHz, and is even smaller in many countries. Working channels for 802.11B and 802.11g can also be used for 802.11n. But the 40-mhz working mode using 802.11n is not recommended because a large portion of the band will be interfered by a single 40MHz transmission. In addition, it requires that the second 20MHz channel with the original 20MHz channel to form a 40MHz channel cannot transmit any original 802.11 information. This greatly reduces the chance of any 40MHz transmission work in this frequency band. In many parts of the world, there are three channels with no overlapping in 2.4-ghz, and a single 40MHz access point is difficult to provide enough channels to meet the access needs of a large enterprise. Even if the existing 802.11b and G devices are not used on this band, deploying access points using the 40MHz channel is also difficult. At the original level, it is difficult to find enough bandwidth to meet three channels without overlapping.

The 5-ghz band has been opened in many parts of the world. 5-ghz has more channels available than 2.4-ghz.

These massive channels make it easy to design and deploy 802.11n networks, even when working in 40-mhz mode.

At the 5-ghz band, there are at least two ways to migrate to 802.11n. The first is to replace the original access point directly with the 802.11n access point when the user budget and other capabilities are reached. This upgrade can be completed within the planned time, or adjusted as needed. The 802.11n access point will replace the existing access point working channel in this way. The new 802.11n access point supports the 802.11n client and supports the original 802.11A client. When the last old access point is replaced and the last old client is replaced, the 802.11n access points switch to a single mode.

The second way to upgrade to 802.11n is to redistribute some of the channels for the current access point to 802.11n. When budgets and requirements are clear, 802.11n access points can be added to the current WLAN, working in parallel with the current access point in overlapping areas. But 802.11n access points support only 802.11n clients and work in a single mode, which provides the greatest benefit for the new standards. When the 802.11n access point covers the entire area, the 802.11n client will be able to work in a single mode all over the place. At the same time, the existing access point continues to serve older clients. Once the old clients are all replaced, the original access point is not necessary.

Today, the 802.11a/g dual-frequency access point can theoretically provide a 108Mbps transmission rate on an Ethernet connection. But in fact because of the efficiency of the 802.11 protocol itself, the peak transmission between 50 to 60Mbps.

The 802.11n access point requires more Ethernet connection bandwidth. With higher speeds and increased efficiency of the protocol itself, a single dual-band 802.11n access point that supports the 20-mhz channel (2.4-ghz) and 40-mhz channel (5-GHZ) can provide Ethernet connectivity between 300Mbps and 400Mbps peaks. This would be significantly higher than a single or two Ethernet connection rate.

For this reason, the planned upgrade support 802.11n should also include an upgrade of the Ethernet switch capability to support connections from 1Gbps to 802.11 access points. This reduces the potential bottlenecks in any 802.11n client high-speed access. Power requirements Many of the 802.11 access points currently in use can be powered using Ethernet (Poe or 802.3AF). This technology provides up to 15 watts of DC power on standard 5 pairs of twisted-pair wires. 802.11N uses more than one wireless channel, the power required is higher than the power supplied by 802.3AF. Fortunately, the IEEE802.3 workgroup has a solution for this. The 802.3AT standard will provide 802.3AF standard twice times power supply, 30 watts. 802.3at can provide sufficient power to the 802.11n access point.

Upgrade to 802.11n you should also consider how to provide a new Poe power supply. There are two options available, the first is to use the Ethernet switch to directly provide power to the connected access point. This may be to upgrade an existing Ethernet switch to support a new Poe standard, or to add a new 1-gbps small Ethernet switch that supports 802.3atPoE standards on the network boundary.

The second way to support 802.11atPoE is to use a power injector. This power injector is typically placed with the Ethernet switch between the wiring and deployed between the Ethernet switch and the wireless access point. This is also a good option if upgrading the Ethernet switch is not within the upgrade range. When deployment of wireless access points is upgraded to 802.11n, the deployment location of wireless access points is also one aspect to consider. If you are replacing an existing access point completely, you do not need to consider future deployments. If a new 802.11n access point is added to the current network, the additional SNR provided by 802.11n can extend the coverage of the wireless access point, but at the cost of reducing the overall performance of the 802.11 wireless network. The SNR is like money stored in a bank, and SNR can be used to increase the rate of data transfer, to increase coverage, or both. But it is not feasible to maximize the two at the same time.