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WLAN: What are high density networks?

Jan 29, 2015

teldat wlan controllerA high density network, can be summarized as a network designed for various or many WLAN clients.

WLAN conservative planning approaches are designed to achieve a good and complete WLAN supply, and at the same time install as less access points as possible. In order to meet this goal in larger areas, usually a so-called Wireless Site Survey is carried out to ensure that wherever WLAN is required, sufficient field strength is available.

However, such installations provide basic coverage and as a result of the increasing number of wireless devices per visitor or employee, it pushes such a radio base coverage quickly to the limit of the WLAN network.

In contrast to the WLAN network design with basic coverage there is also the approach to plan a design for a large number of wireless clients, such installations are referred to as “High Density Networks“. Here, a significant higher number of access points will be installed in order to provide Wi-Fi connectivity with good performance to many clients.  However, a „High Density Network“ installation, only by increasing the number of access points is not enough. An excessive number of access points can even reduce the overall performance.

What is needed to install a “High Density Network”?

The following steps are considered to be necessary to successfully install a “High Density Network”:

  • Carry out an analysis together with the customer, to determine how many and where WLAN users are to be expected, which services are to be used and which is the performance required.
  • Perform capacity planning so that we provide a first rough plan on how many access points and where to install them in order to meet the demand
  • WLAN channel planning, so that overall, there are a sufficient number of access points planned to overlap-free channels. It is particularly important, specially with a “High Density Network” that a channel is firstly reused  if the signal from neighboring access point that use the same radio channel is too weak, otherwise the network overall performance is greatly reduced by interferences and poor signal/noise ratio. In the 2.4 GHz network there are only three overlap-free channels within a  High Density Network installation that always use dual radio access points to provide 5 GHz WLAN network. The 5 GHz network has up to 19 overlap-free channels available, allowing a higher number of WLAN clients. In a very close-knit network with many access points some 2.4 GHz access points will need to be turned off, due to the channel’s shortage in the 2.4 GHz network in order to avoid interference.
  • WLAN Site Survey Planning, to ensure that all of a building’s area is powered with a strong signal.
  • WLAN installation. During the  configuration there are a number of things to keep in mind. First of all, it should be ensured that the WLAN products used are suitable for such installations. Functions such as WLAN load balancing, airtime fairness, bandwidth limitation and band steering should be supported. During the installation itself, care should be taken, so that the number of SSIDs is as few as possible, since each additional SSID generates overhead reducing the overall system performance.
  •  Check the WLAN installation. Here, the first check to be carried out, is whether all areas provide a good field strength to ensure a satisfactory network connection. It is particularly important within High Density Networks for this to be reviewed in ongoing operations, to make sure that all participants can work smoothly together and the required performance is met with the maximum number of users. A WLAN controller providing the necessary analytical tools is helpful.

Can a High Density Network performance increase by using the new standard?

The new 802.11 standard operates in the 5 GHz band. To achieve these needed high data rates needs an up to 8x higher bandwidth than 11.n.  Due to the higher bandwidth not enough overlap-free channels are available for  a high density network in the 5 GHz band. Therefore the channel bandwidth for .11ac devices has to be reduced to the limit of 11.n. The bottom line is that only a small performance gain is achieved by using in High Density Networks.

The next generation of standards will be very interesting for high density networks. The next generation of chipsets will support and allow by multiple use of the transmission streams MU-MIMO (Multi User MIMO)  a higher number of clients per access point. But for this purpose the WLAN client as the WLAN access points have to be equipped with the second generation chipset.

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