Major Considerations for deploying wireless network 802.11n

Both wireless network technology and wireless LAN Settings have made progress to some extent. How should we look at 802.11n deployment? With the advent of 802.11n, the wireless LAN (WLAN) field is undergoing a fundamental transformation, and this transformation is just as striking as the birth of the wireless LAN. The extremely high data rate of the 802.11n final Standard lays a solid foundation for realizing the full wireless enterprise network. A wide range of multimedia applications will be seamlessly deployed on all nodes in the network, and its superior performance far exceeds the previous 802.11a/B/g technology.

But the problem persists: "How to plan a high-performance 802.11n network ?" Although the advantages of 802.11n have been paid more and more attention by WLAN Equipment Manufacturers and have aroused a wide discussion in the industry, no one yet can explain how 802.11n network planning works, or, more importantly, under what circumstances will it fail! "How can we benefit from the thoroughly cleared 802.11n deployment implementation project ?" "To migrate the existing network to the 802.11n platform, what will happen if I just remove and replace the Access Point (AP ?" "How can we better complete the phased migration to 802.11n ?" This article explains the basic knowledge of 802.11n required to solve these problems and helps you select the best policy that suits your organization.

What is the impact of 802.11n on "3C" in network planning?

Network Planning should pay attention to three factors: Context, Coverage, and Capacity, collectively referred to as "3C" in network planning ". Technological advances in the 802.11n standard have affected all three factors. In terms of background, network planners must consider the impact of new 40 MHz channel interference and multi-input, multi-output (MIMO) technologies related to specific field complexities on channel planning and Access Point settings. In terms of coverage, designers should understand the differences between 802.11n and traditional systems in terms of coverage, and make correct definitions of coverage requirements according to network requirements. Finally, the 802.11n standard data transmission speed and MAC layer efficiency are improved, so the network capacity will also increase; however, only by correctly planning the distribution of network customers can the increased capacity be fully utilized.

Background

The Background Environment for deploying a wireless LAN is very important. Neighboring access points or other wireless transmitters that use the same frequency band may interfere with the network. This type of wireless congestion will lead to packet loss, slow network speed, and reduced network capacity. In addition to the traditional same frequency and near-frequency interference, the 802.11n 5 GHz band deployment should also consider potential interference from radar systems. The background environment also includes a wireless LAN environment related to the field structure, which will have a great impact on the performance of 802.11n MIMO technology.

Interference and channel Planning

Compared with the 20 MHz band used by traditional 802.11a/B/g, the data speed of the 40 MHz channel of 802.11n is improved by more than twice, which is an essential technology for high-performance wireless networks. However, the increase in channel scale also means the increase in potential interference and the narrowing of the spectrum range of information planning.

In the United States, if a 40 MHz channel is used in the 2.4GHz band, only one non-overlapping 20 MHz channel is available, resulting in an increase in the adjacent channel interference probability of the 2.4GHz channel. As there are only three non-overlapping channels available, it is very difficult to plan the GHz channel. Therefore, we do not recommend that you use the GHz 802.11n deployment to use the 40 MHz channel.

Fortunately, the 5 GHz band frees 802.11n users from strict GHz band restrictions. In the United States, if the access point is fully compatible with the dynamic frequency selection (DFS) (the next section will detail DFS), 11 non-overlapping 40 MHz channels are allowed in the 5 GHz band. A large number of non-overlapping 40 MHz channels in the 5 GHz band allow 802.11n deployment to take full advantage of its performance advantages. Therefore, we recommend high-performance WLAN networks to use this deployment strategy. See table 3 for the overlapping 802.11n channels.

Impact of radar avoidance on 5 GHz channel planning (DFS)

As described above, to maximize the number of non-overlapping 40 MHz channels in the 5 GHz band, the access point must be fully compatible with DFS. According to the FCC (Federal Communications Commission) Rules and the definition in section 15th (47 CFR § 15), this means that if the equipment detects in-band interference from nearby radar systems, all transmission activities in this band must be immediately stopped for 30 minutes and transferred to other non-interference channels. Obviously, this federal regulation requires that the access point channel be dynamically changed, which will inevitably affect the 5 GHz channel planning.

Although some problems may occur when DFS is included in a 5 GHz 802.11n deployment project, the DFS band (5.25-5.35GHz and 5.47-5.725 GHz) the optimal planning does not change much compared with the non-DFS band planning. The first step in the deployment process is to conduct on-site investigations to determine whether Radar interference exists in the deployment environment. Second, a network channel plan should be developed to avoid using channels that have already been detected to DFS. Finally, the DFS standard requires that the operating channel be dynamically changed when it is disturbed. Therefore, an empty channel should be provided to detect Radar interference. Based on experience, it is best to provide at least one idle channel in a non-DFS band.