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For most people, visiting a major league stadium to watch a favorite team is a noteworthy event. In fact, with the enormous growth of smartphones, tablets and other mobile devices, it’s one of the most frequently shared experiences online.  Every game, thousands of fans attempt to connect to the Internet to send emails and tweets to friends and family, and post photos and videos on Facebook and Instagram. Few fans understand the technology that is required to provide them with Internet access at the game.

In stadiums, as well as other large public venues, when concentrations of mobile device users simultaneously try to access the network, cellular networks are insufficient for the demand. Operators ease the congestion by offloading the bandwidths to complementary technologies, most often Wi-Fi. But traditional Wi-Fi networks are designed to provide adequate coverage for all, in all areas where the network has been implemented. Bandwidth capacity is often inadequate for the applications used by today’s mobile devices, which can vary wildly and require enough capacity to transmit enormous files. As a result, conventional Wi-Fi networks are also easily overwhelmed. 

In response to the ever-increasing popularity of mobile devices, stadiums are now constructing “high density” networks to ensure adequate capacity (higher data rates.) High density networks are created by “mapping” users into smaller radio frequency (RF) cells of operation. To generate these narrower cells, access points are connected to high density narrow-band antennas that minimize channel-to channel interference, which is the most significant cause of limited performance in a Wi-Fi network. With fewer users per AP, the amount of bandwidth per user is increased and spectral capacity is maximized.   

Several essential design variables must be considered when designing a high density network. Total coverage area, channel utilization, frequency of reuse, interference, signal strength, spectral capacity and regulatory requirements are all factors affecting the network. Designing the high density network begins with a comprehensive analysis of existing client infrastructure capabilities, the number of users/clients, the number of Wi-Fi enabled devices per user, the user application requirements, the physical facility characteristics, and a careful determination of the appropriate number and placement of access points.

Figure 1. A Cisco access point with six Bantam antennas affixed to the Under-the-Seat enclosure.To design a high density network for a stadium, first determine the overall capacity necessary by estimating the number of clients (seats in the stadium) and client devices that will be supported. Next, determine the client device capabilities and the application throughput requirements.  Typical application throughput requirements for users in stadiums include accessing the network to send email, visit social media sites and share photos and videos.

After the access point is selected, a site survey is performed. A wireless site survey, sometimes called a radio frequency (RF) site survey, is the process of planning and designing a wireless network that will deliver the required wireless coverage, data rates, network capacity, roaming capability and Quality of Service (QoS).  The survey usually involves a site visit by the surveyor to understand the RF behavior, discover RF coverage areas, test for RF interference, and to identify optimum installation locations for access points and antennas. This requires analysis of building floor plans, inspection of the facility, and use of site survey tools. After initial AP and antenna installation, testing is performed and adjustments are made to refine the design for the highest capacity per user with the least amount of interference.

The specifications of the high density antennas are integral to the performance of the high density network. Two key specifications that define high density antennas are beamwidth and gain. Beamwidth is measured at two frequency ranges for Wi-Fi (2.5 and 5 GHz) and two directions (horizontal and vertical). To determine the beamwidth needed, a network designer calculates the required capacity per client device in a given area, while taking into account co-channel interference. Narrow beamwidth directional antennas are an essential component of the high density network because they use narrow beam patterns to focus RF into small cells that enable stronger, more reliable Wi-Fi signals, reduce channel-to-channel interference, and increase capacity. Higher data rates are inversely proportional to greater coverage. That is, the greater the data rate, the smaller the coverage area. Generally, speaking the narrower the beamwidth of the antenna, the better it is for the high density network.

The other key specification of high density antennas is gain. Traditional antenna gain ranges from 2 to 6 dBi.  High density antenna gain begins at 4 dBi, and can increase to 14 dBi or higher.  Higher gain antennas are beneficial in large venue deployments where the distance the RF signal must propagate from the antenna to the users is much greater, such as stadiums and large, outdoor public events or indoor venues such as concert halls or train stations.  Lower gain antennas are used to minimize floor-to-floor interference common in classroom buildings.

“Open” stadiums with no roof and large venues with very high ceilings can be particularly challenging to network administrators because installation of “top down” high gain antennas and APs may not be practical, or even possible. Ventev, a manufacturer of products and solutions for large public venues, recently introduced a new TerraWave product designed to address this unique challenge.

Under-the seat Wi-Fi solution
The TerraWave Under-the-Seat Wi-Fi Solution inconspicuously provides “bottom up” connectivity to the network for several rows of users to ensure capacity and significantly improve Wi-Fi experience. The compact solution consists of a water-tight, polycarbonate NEMA 4X enclosure that features a tamper-proof cover for maximum protection of valuable equipment. Housed within the enclosure, the AP (purchased separately) is installed with four to six small but powerful Omni Bantam Antennas that maximize capacity to provide a strong, reliable connection to the Wi-Fi.  An innovative mount can be installed onto a concrete or metal surface, and raises the enclosure off the surface to allow for water runoff.  The Under-the-Seat Wi-Fi Solution is compatible with Cisco 2600/2700/3500/3600/3700 APs.

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