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45 C H A P T E R 5 An airport authority has multiple stakeholders it must work with regarding its wireless ser- vices. The solutions to interference must be solved within the business models and stakeholder relationships that either currently exist or that can be adopted. If an RF interference solution is not affordable, it will not be implemented. If one stakeholder is suffering interference, but another must pay for the solution, there is unlikely to be a change. Costs and consequences must be aligned. Those that suffer the consequences of RF interference must find ways to incen- tivize and compensate those who have the ability to mitigate the interference and improve performance. While passengers using WiFi may be the first stakeholders to come to mind, airport tenants and an airportâs own operations personnel are equally vested in having a reliable network and, in fact, may be considered more important users of the network. Another stakeholder group is the airportâs own emergency services (such as aircraft rescue and firefighting), as well as off-airport mutual aid responders. Their equipment follows the general trend and increasingly integrates WiFi and wireless functionality. While they may not operate at the airport on a daily basis, they do not want an internal airport terminal interference problem with their WiFi equipment during an actual emergency. Television stations and media should also be considered. Media are always interested in avi- ation stories such as stranded travelers, security events, or other irregular operations. Many airports have specific media staging areas for them to broadcast from near the terminal or some- times inside the terminal. What is not planned is how remote broadcast television trucks may cause interference with internal airport WiFi networks since some stations have an assigned auxiliary broadcast frequency overlapping the 2.4 GHz band. Another operational capability for airports is related to security and uses wireless technology for perimeter intrusion detection along the fence line or in vulnerable areas inside the airport. This technology may also be deployed to help alert and avoid movement area incursionsâ incidents where vehicles, pedestrians, and/or aircraft have entered into a controlled area of the airfield without proper authorization. Wireless capabilities that alert the airport or air traffic control to such occurrences are becoming increasingly popular technology installations. All of these relationships come together in the master service level agreement (SLA) between the airport and the network operator it selects. There may be other SLAs established for specific tenants or services. An SLA is recommended anytime a new use for the WiFi network is planned. These individual SLAs give the organization introducing the new service and the network opera- tor a formal method for translating service expectations to technical requirements. Particularly for high-reliability services such as those supporting emergency or security operations, an SLA is important for ensuring that the network operator has agreed it can provide the level of reli- ability desired. Stakeholder Relationships and Business Model Options
46 A Guidebook for Mitigating Disruptive WiFi Interference at Airports Master Service Level Agreements Many airports throughout the U.S. utilize a third-party operator to run their WiFi. This third- party operator often has complete control over the WiFi system, with a simple set of functional guidelines to adhere to throughout the long length of the contract. These functional guidelines are often based on metrics that enforce system operability and coverage, ensuring that all airport stakeholders are able to use the WiFi network in the many dif- ferent areas of the airport. Bandwidth and system revenue are often large drivers of these SLAs, as third-party operators are required to provide a certain amount of bandwidth per user, along with positive cash flow from advertising or other WiFi-generated opportunities. Furthermore, these SLAs often enforce non-emergency and emergency maintenance services onto the WiFi operator. Some call for 99% up-time for the system or other measures of network availability. There can be component-level requirements for coverage, defined by minimum signal strength for an access point over the entire area to be serviced. There can also be requirements for controller availability. Service Level Agreement Enforcement Contracts and SLAs with varying complexity exist throughout the U.S. SLAs consistently include penalties for service deficiencies, often in the form of daily liquidated damages from the inoperability of the system. The ultimate penalty, of course, is lease termination. However, despite existing SLAs, there are still interference and coverage problems, even in third-party operated locations. There are several reasons for this. In some cases, the terms of the SLA are insufficient to ensure the required level of performance. Writing specific, enforceable SLA requirements requires in-depth knowledge of WiFi and network operation. If the SLA is overly general or fails to address a key area, the result can be inadequate service. Another common problem comes not from the SLAâs inability to hold third-party operators to their contracts, but from airport authorities that do not monitor the system and the perfor- mance metrics adequately. It takes special tools and expertise to evaluate network performance. A major reason airports contract with a network operator is that they do not have the time or tools to do the job themselves. Airports across the U.S. do not regularly measure the performance of their WiFi system, especially as it pertains to interference. Reports are regularly filed by third-party operators of the WiFi, with little airport oversight or testing of the system in the field. As such, airport managers should employ their own RF testing schedule within their facility, and ensure that the airportâs WiFi operators are living up to the conditions of the SLA. Wireless site surveys should be conducted on a monthly or at most quarterly basis, in order to gain an understanding of RF interference sources. The results of these surveys should be reviewed with third-party operators, and areas with less than satisfactory coverage addressed. Shared Tenant Services WiFi, and in general device connectivity to the network, is more and more commonly viewed as an expected utility instead of an added service. This utility is used not only by those traveling through the airport but by those employed by, and working in and around, the airport facility. Often, some of the heaviest and most consistent users of the WiFi at an airport are not its travel- ers, but those who earn their livelihood working at the airport as employees. These daily users require data connectivity along with wireless service but, for a variety of rea- sons, may not wish to rely on an airportâs WiFi service. The alternatives to airport-managed WiFi
Stakeholder Relationships and Business Model Options 47 could include the installation of tenant-owned access points within their lease area, or activation of hotspots or cell phones to satisfy the coverage need. Tenants have a variety of conveniently available options for Internet access, but the airportâs WiFi network is benefited when it is used as a shared resource. Alternative Revenue Sources Some airports have alternate non-airline revenue sources such as gambling in McCarran Inter- national Airport (LAS) and gas wells at Dallas/Fort Worth International Airport (DFW), which offer increased budget options to support their WiFi networks. In general, the pattern is that a network operator installs and manages the network and balances capital and ongoing operating cost with revenues. The airport authority negotiates the contract with the vendor and once the air- port is satisfied with the balance between cost/revenue and customer satisfaction, they are happy to leave the technical planning and operation of the network to the selected network operator. Alternative Connections and Their Impact Not dissimilar to the traveling public, airport and stakeholder employees will find alternative ways to acquire wireless connectivity if an airportâs connectivity is not adequate. Operational areas, tenant lease spaces, and third-party offices provide their own wireless if it is not available for them. The addition of alternative access points or other wireless devices within an airport environ- ment only compounds the problem of wireless interference. Connections and networks operat- ing independently, and often without coordination with the main WiFi network, can push a strained system to its functional limits. This has been evidenced by airlines and tenants installing their own support infrastructure systems without the airportâs knowledge. If the airport does not provide these services as part of a lease contract, or does not have any policies in place to deter such practices, there is little control over the growth of multiple systems. However, providing connectivity for these tenants and operational areas from the airportâs existing wireless infrastructure is not as simple as installing additional access points. Service set identifiers and possibly fully separate virtual local area networks (LANs), with dedicated band- width and administrative support, will be required to make the wireless usable for whichever tenant requires it. This additional infrastructure and configuration comes with expenses, and in the case of free WiFi, additional upkeep and maintenance, along with higher bandwidth needs from the airportâs Internet service provider. All this must be offered to the tenant for a cost that is attractive when compared with other options available to them. This combination of wireless needs in tenant spaces, compounded by additional expenditures in providing additional infrastructure, results in the need for the airport manager to take a new look at shared tenant services for WiFi connectivity. Benefits of Shared Tenant Services Shared tenant services (STS) are a multi-tenant environment business model in which a property owner provides a common set of sophisticated technical services. Telephone service, cabling infrastructure, and wireless data networks are some examples of resources that can be airport owned, managed, and shared among various tenants. In a traditional model, rather than each tenant purchasing, installing, and maintaining an individual system, airport tenants and the airport share a common system. For voice applications (the traditional and most common type of STS in airports), this may include a private branch exchange (PBX) telephone system
48 A Guidebook for Mitigating Disruptive WiFi Interference at Airports or a voice over Internet protocol (VoIP) system. Shared tenant services provide the potential to effectively and efficiently address all the telecommunications, data network, and tenant services requirements at an airport, including accountability, communications, processes, and response. Tenants benefit from the convenience of having one stop for all their communications require- ments, including on-site support. Shared Tenant Services Pricing Model Shared tenant services can be implemented either as a new revenue stream, or as a method to recover costs and improve customer service. Pricing models for airports should first examine their fundamental approach to servicing tenants and customers at the airport, and whether pure customer service, or profitability, forms the core of an STS wireless model. The fundamental assumption of the wireless STS pricing model is that each new service pro- vided for a tenant is incremental to the existing infrastructure. As such, the pricing for the addi- tional wireless services reflects at least the recovery of the additional costs, along with any margin that the airport wishes to implement. These additional cost components associated with wireless service for tenants include the following: ⢠Administration: The administrative costs include a possible help desk, cable management system, coordination, and costs associated with developing and marketing the overall program. ⢠Connectivity: The connectivity costs include network costs (specifically Internet access) asso- ciated with a particular access point. ⢠Hardware: The hardware costs include the amortized cost of new hardware (i.e., network switches) necessary to provision a particular service. ⢠Cable Installation: The cable installation costs include the amortized cost of installing new cable, along with possible installation of fiber infrastructure. Conduit, tubes, and termination blocks should be excluded from these calculations. ⢠Provisioning: The provisioning costs are the initial costs associated with creating a new cir- cuit. These include infrastructure assignments, cross connections, escort time, and circuit testing. ⢠Maintenance: The maintenance costs include personnel costs associated with maintaining and troubleshooting the connection over the course of the agreement. Many costs associated with implementing a wireless STS model are fixed, and therefore repre- sent a higher percentage of overall STS charges. It should be noted that costs, and the subsequent rates charged to tenants, need to remain competitive with other wireless connectivity options. If costs are not competitive, then tenants may seek to use other connectivity options, increasing the chance of interference and decreasing financial support for the airportâs WiFi infrastructure. Business Model Any solution to an RF interference or network performance problem must be implemented in the context of the airportâs business caseâhow the airport creates, delivers, and captures value in economic, social, cultural, or operational requirements for wireless services generally and for the WiFi network specifically. This process of implementing an interference mitigation plan is part of the overall business strategy. If the cost of the solution is not perceived as affordable, it will not be implemented or may be only partially implemented. The solution must also be temporally feasible. For example, it is unlikely an airport manager will solve a complaint about interference reported at Gate 9 by planning a total and costly network upgrade that would take months to be approved, let alone implemented.
Stakeholder Relationships and Business Model Options 49 However, the perceived business case and the real business case can be different. This is par- ticularly true with the changing role of the WiFi network. Many still perceive WiFi as a high-end amenity that has little impact when it is not available. However, with the networkâs increasing integration into airport operations, the cost of disruption can be substantial. The temporal aspect can also be falsely perceived. Choice of metrics is critical. If an airportâs metric is customer complaints, then the timeframe for resolution is very short. The complain- ing customer wants the problem resolved during the time they are in the airport. However, if a different, more forward-looking metric were chosen, then timeframes of months or years might be available to solve a growing problem. The options available multiply. There is a rule of thumb based on experience among engineers who specialize in interference resolution that the cost of the solution goes up not by an increment, but by an order of magni- tude for every stage of implementation. The time when a change is most expensive and when options are the fewest is after a network is deployed and products are installed. Few solutions are then available and their cost is extremely high. Installing an interference solution during a network upgrade will often be a tenth of the cost, and many more solutions become possible. It is not uncommon to find that all that is needed for major improvement is, first, determining the sensitivity to interferenceâknown in the field as the devicesâ coexistence capabilityâand then selecting more interference-resistant equipment. If manufacturers receive negative feed- back focused on their equipment from many sources such as airports, they perceive potential loss of sales. Market forces can often make the difference in cost between interference-resistant equipment and interference-sensitive equipment small or even non-existent. One missing component between WiFi consumers and the manufacturers is information on interference-related complaints about products, accompanied by a drop in sales. For example, if filters to reduce interference from adjacent WiFi channels were installed, some, but not all, of the adjacent channel interference could be removed. Similarly, linear amplifiers could preclude some transmission interference on the WiFi wave- form. Manufacturers will likely fix these and other sources of equipment-generated interfer- ence if they perceive a profitable business case via airports or other similar applications where interference mitigation is needed. But manufacturers need to know how much and what type of interference resistance airports want before they start development of a new generation of products. They can often build those specifications into the design for a small fraction of what it would cost to provide a similar solution as a retrofit to an already designed product. Similarly, if chip and component manufacturers know what interference resistance is needed in products that use their components and how that end performance relates to specifications, they can often provide interference-resistant components at a small fraction of the cost of adding that same solution to existing product design. Beyond influencing WiFi manufacturers, the airports can work with standards development bodies, such as the IEEE 802.11 committee, and trade associations, like the WiFi Alliance, to make RF immunity and coexistence part of the standards and product certification process. Such efforts may take place years before the impact will be seen in products installed in networks, but they have the lowest total cost and open up the largest possible set of solutions. Not every airport can do this, but if airports as a whole had representation, then they could influence future standards as well as mitigate potential future interference issues. There may even be a cost savings by ensur- ing higher quality equipment as well as avoiding the cost of resolving future network problems. A list of best technical practices to ensure accessible WiFi service is provided in Appendix B.
