How to get a lot of street wifi? Experience in building Outdoor networks with high subscriber density

    Street, park, trees, a large number of subscribers - the worst conditions for WiFi coverage. If you add summer, i.e. If the foliage on the trees attenuates the signal and young people are blown up on gadgets, we get a crash test for wireless equipment. Such conditions were on Seliger, where at one time a WiFi network was deployed for participants in the annual rally.





    Initial data. 14 thousand people. An area of ​​20 hectares. Street WiFi. The main channel is 100 Mbps with no restrictions on the duration of the Internet session and the amount of consumed traffic. Loads in the form of competitions of rally participants for the speed of searching for information on the Internet - up to 1000 simultaneously working subscribers. And all this with a minimum number of WiFi access points.

    The solution of the problem.Based on the criterion of minimizing the number of equipment installation sites and the high density of client devices, Ruckus Wireless access points were selected . (If you take unprofessional equipment, the number of access points required for such a number of subscribers can equal the number of trees in the forest - a joke, but not far from the truth).

    Defining a user profile . It was suggested that customers primarily use smartphones, which means that there is only one transceiver, and mainly in the 2.4 GHz band.

    Typical Stationfor service over the entire azimuth consists of three sector devices. But often because of the complexity of the location, part of the sites (points of presence) was not located in the center of the concentration of users and included only one or two sectors.



    We estimate the available system capacity based on the selected performance per client. The client profile is limited to the 2.4 GHz band and one polarization. In such conditions, using the 20 MHz wide bands, we can count on the performance in the 65 Mbps radio channel. Useful performance at this channel speed will be about 45 Mbit / s.

    Using only the 2.4 GHz band in the open space leads to a significant interference of the systems, so the equipment capacity will be reduced by retries. Estimating the repetitions at the level of 35%, we can talk about the performance of about 30 Mbit / s to the base station. Thus, with a load of 100 subscribers, we can talk about 256 kbps of real traffic to the client device. It seems to be not much. But since Ruckus supports fair servicing of client devices, it is possible to allow oversubscription and limit the capacity per subscriber to already double the value.

    According to the assignment, the laying of cable systems was allowed only underground and with a voltage of not higher than 48 volts. The logical network diagram represented several radio networks with different security settings, each network was tagged with its own VLAN. Thus, a typical design of a base station of a 6-meter mast support, several Ruckus ZoneFlex7762 devices, injectors, and media converters was developed.

    Two types of access points were used in the network - models ZF7762-S and ZF7762. Symbol "S" - means a sector antenna with a gain of 12 dB and a coverage angle of 120 degrees. Without the “S” symbol, we have an omnidirectional (ONMI) access point.



    Ruckus ZoneFlex7762 Access Point Appearance



    Ruckus ZoneFlex7762-S (sector) and 7762 (OMNI) access points with open covers



    The coverage area of ​​ONMI and sector access points and the method of their attachment in suspension points. Network block



    diagram.



    Curiously, all 14,000 subscribers were served by only one 1100 series controller. Given the importance of the event, the controller was reserved (they allow hot backup) in the same way, to ensure reliability.

    Site survey was performed by Fluke Network utilities. The assessment was made both by the signal level of the sector, and by the level of interference of neighboring stations, according to the results, the frequency plan and the slope of the sectors changed. After commissioning, the main system parameters were monitored, such as the number of users, network performance.



    System performance, sector availability



    Traffic statistics, client devices

    Brief results of network deployment .
    The assumption of the predominance of single-channel devices was confirmed, the network capacity and bandwidth are calculated correctly. The system withstood a peak load of a thousand connections, the load on a part of the points exceeded 150 connections per point. The customer, for obvious reasons, was very worried about the stability of the Wi-Fi network in such a busy mode, but Ruckus proved to be reliable high-performance equipment. As a result of complaints from the organizers of the event and the users were not.

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