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39 C H A P T E R 4 Strategic planning as it relates to technology as a whole, and in this case specifically WiFi, requires a few key components to effectively phase and ultimately execute. Proper technology planning can help organizations visualize some of the roadblocks they may encounter, and ulti- mately better serve their customers. Implementable technology planning begins with an assess- ment and development of a robust communications infrastructure. 1. Existing SystemsâThe first key component of strategic planning is a firm understanding of all the systems and technology that the airport already owns. While this may sound like a simple issue, many airports do not have a centralized database, or centralized knowledge base, of all their IT systems, much less their interdependencies. A good discussion concern- ing airport management of systems can be found in ACRP Report 59: Information Technology Systems at AirportsâA Primer. 2. Future PlansâWithout unified technology planning, there rarely exists an enterprise-wide view on which system upgrades and long-term initiatives will affect other parts of the air- portâs IT infrastructure. Airport IT departments often play catch-up to the various pieces of technology and construction implemented in an airport. IT departments need processes in place to stay involved with all of the IT long-term initiatives. 3. Inter-Departmental CommunicationsâBeyond the IT department, there are many differ- ent system users who have a firm grasp of the tools their department needs to succeed, but experience difficulty getting their functional requirements supported and in the procurement pipeline. This lack of departmental communication can result in problems with the change management process, or poor documentation of system upgrades and new installations. 4. Focus GroupsâNew initiatives ranging from utilities metering, to airfield management devices, all the way to shared tenant services, can all be initiated by separate departments, and simultaneously rely on a WiFi system that has not been provisioned for multiple services such as these. The first step often begins with focus group meetings for each separate depart- ment, working to identify and document departmental WiFi needs and objectives. Then a second group can convene to address all the objectives and priorities in line with the airportâs business case and strategic plan. 5. Technology GovernanceâFollowing these independent meetings, technology governance is needed to make all of these interdependent parts work together. Governance, at an enterprise level, can help the many different departments of an organization develop a common goal and a common, robust infrastructure that many of the separate airport departments can utilize. All of the preceding elements are important aspects of the airportâs ability to achieve its objec- tive. With the growing use of wireless by a wide variety of systems, it is increasingly common for the wireless and particularly the WiFi network to have a role in these processes. This key piece of supporting infrastructure is often taken for granted and not evaluated from the many perspec- tives of the airportâs departments, travelers, customers, and partners. Strategic planning can help Strategic Planning for Wireless Networks
40 A Guidebook for Mitigating Disruptive WiFi Interference at Airports organizations realize the many different operational functions at their airport, and specifically how they affect their WiFi, both now and into the future. As an example, rather than the airfield operations department developing WiFi to support their inspection of vehicles, while the airportâs security department installs a wireless perimeter intrusion detection system, the organization can create a common plan that ensures coexistence, or even potentially shares a common WiFi system that everyone can utilize. This common system will help reduce interference between the separate sources of RF, while at the same time better meeting the needs of all those utilizing the WiFi connectivity and decreasing the overall cost of system ownership. This simple example applies equally to all airport interior WiFi systems, as well as those systems operating in the airplane parking aprons, baggage areas, and service areas. Coor- dination among all stakeholders will reduce interference and better meet the needs of all involved. However, developing this common view, and an enterprise governance attitude, is difficult if proper planning and procedures are not put into place, hence the requirement for an airport strategic wireless plan. At least yearly needs assessments should take place among the many stakeholder groups, with priorities weighed and supporting infrastructure evaluated. Further- more, quarterly technology governance meetings could be held with key departmental leaders to share thoughts and voice upcoming initiatives that may affect one another. In the case of WiFi, these yearly assessments and quarterly meetings can help departments ensure systems that rely on the infrastructure are supported, and new initiatives will not threaten the integrity of the existing network. Furthermore, enterprise-wide technology planning and governance can help departments realize synergies that reduce overall system costs. The Strategic Plan Airports share significant similarities with healthcare in relation to WiFi networks. Airports and hospitals both have large numbers of people who transit through their facilities and commonly con- nect with their own devices. Airports and hospitals also share a mix of WiFi applications, supporting their visitors but also supporting core functions for the organization. In May 2014 the Association for the Advancement of Medical Instrumentation (AAMI) Wireless Strategy Task Force published âFAQ for the Wireless Challenge in Healthcare.â That document states the following: What are the biggest mistakes that healthcare delivery organizations make in managing wireless issues? . . . . At a high level, these mistakes can be summarized as, âThe biggest mistake a healthcare delivery orga- nization can make with wireless is failing to create a strategic plan on how to use and implement wireless technologies. Each wireless technology, whether it be WMTS [wireless medical telemetry service] teleme- try, cellular telephones, WiFi networks, or proprietary technologies for RFID [RF identification], requires a significant investment in infrastructure, and presents multiple risks, including security breaches, patient safety issues, and adverse impacts to other wireless applications. Failure to create a foundational strategy increases the probability that the risks become adverse events.15 Wireless services are part of total airport operations and may therefore be considered a compo- nent of the airportâs strategic vision and plan. Figure 21 depicts how planning for wireless services for all customers, stakeholders, and airport operations fits into the airportâs overall strategic plan. This is just one example of how different airport entities are related and conceptually depicted from a strategic planning perspective. There are other ways to depict this relationship if the airport chooses a different approach, i.e., segregate the users or take complete ownership and control of the network. However, the key is to establish a strategic plan that shows the relationship between all airport parties, minimizes future problems, and effectively plans for wireless network growth. 15 AAMI Wireless Strategy Task Force, âFAQ for the Wireless Challenge in Healthcare,â May 2014, question 4.
Strategic Planning for Wireless Networks 41 Generally the strategic plan divides into planning for the public network, stakeholders, and the airportâs own operational uses for the WiFi network. The level of service desired can be very different between the three and may impact overall network design. If the airport operates only one network, then maintenance is easier and there are potential cost savings, as well as the possi- bility of sharing those costs across multiple stakeholders. Different services can be separated into logical networks and assigned appropriate priorities. However, they still share the same underlying network and therefore have shared vulnerabilities. The alternative is to have multi ple, independent networks. This can cost more, complicate maintenance, and increase the potential for interference. However, each network can be designed for the services it is intended to provide, either for public access, stakeholders, or to support a network airport operation. A wireless service plan is a part of the airportâs overall technology plan. It must support the larger plan and fulfill its role within it. The resources required to implement the wireless services must fit within the total technology plan, which must fit within the airportâs budget, fiscal objec- tives, and overall business case. Rough Order of Magnitude Estimates When planning a new airport network installation or a network upgrade, it is helpful to first do a rough order of magnitude estimate of the current airport interior WiFi needs and the future needs, within the planning horizon of the estimate. The rough order of magnitude estimate provides a ballpark assessment of the cost and complexity of the project and serves as a planning tool for more detailed project planning. Passenger traffic flow through the airport is one of the starting places. It is important to know how many will pass through the airport and also what the traffic peaks look like. Network plan- ners need to beware of being misled by the averages. Average traffic is very different from peak traffic. Airports want their networks to give all passengers a good experience, including those who pass through during holidays or are at the airport during an irregular operations period, such as when network traffic is high due to weather-related flight cancellations and delays. It is also important not to rely on current traffic numbers but to look at forecast traffic estimates through the master planning process. Figure 21. Objectives for wireless services are a component of an airportâs strategic vision and plan.
42 A Guidebook for Mitigating Disruptive WiFi Interference at Airports From analyzing the airport traffic, the next step is to estimate the number of associated devices and the number of active devices expected to be used. A rule of thumb used to be that 25% of travelers have a device that can connect to the network. It is probably better to use a 50% esti- mate today. Associated devices are not active devices. However, every device that connects to the network has an impact on network capacity. Network planners have a variety of ways to estimate the capacity that a network must have. In a highly dynamic network with fluid use, peaks and valleys in demand, but also the interfer- ence that occurs in open environments, excess capacity is needed. Interference impacts network capacity in a variety of ways, such as increasing the amount of data sent when retransmission rates rise and data is sent twice and sometimes multiple times. To improve tolerance for interfer- ence, extra network capacity is needed to support the mitigation measures, such as retransmis- sion or slowing of transmission speeds, used to reduce the impact of interference. Reference Design Reference design or reference architecture is a loose term that applies to many things. For exam- ple, in a building like a skyscraper it refers to the architectural layout and services like elevators, cen- tral lobby, plumbing, wiring, and heating and air-conditioning. Reference design connotes a given convention for the physical layout and for services. It is not cast in concrete and has variations. Airport building reference architecture refers to common layout modules like ticketing, bag- gage, transportation, food courts, passenger waiting areas, restrooms, and gatesâpositioned with respect to the site and to the space and operational functions inside the building. A WiFi reference architecture can be based on similar items centered on network users. In a WiFi network the architecture would be based on the number of airport users and operational functions, the number of airport stakeholders and business concerns, the total number of transit- ing passengers both at off- and peak-times, the area of coverage, WiFi equipment design limita- tions or capabilities, as well as the airport architectural layout and its potential impact on network design. In addition, acceptable levels of performance (i.e., metrics), user priorities, stakeholder participation, and a management and reporting structure will also have to be identified as they will affect the WiFi network design. There can be other factors included in the architecture as deemed necessary by the individual airport, but these form a baseline to create a strategic plan that can be used by an airport initially installing a WiFi network or leveraged by airports wishing to mitigate interference problems, upgrade, or expand the network. Cost along with perceived value then becomes the driver for how much or how soon some of these services can be implemented. For example, WiFi reference architecture can show how the hotspot networks are distributed throughout airport areas, the different networks they serve, and how they are controlled. Since airport designs are often common across âsame size airports,â the hotspots can be in similar relative positions but varied to adapt to the specific RF environment. In essence, there are some common layouts both in space, network, and RF environments that work better than others. They are used as a starting point and adjusted if need be for opti- mal performance. This is not an exact science but provides a framework that can be customized based on past experience and identified RF interference issues. IEEE may have some additional definitions for certain vintages of WiFi. Network Performance Management An aspect of network planning is how the performance of the network will be managed. To manage network performance, one must first know the current performance, or the designed performance of a newly installed network and what its potential might be. Network performance
Strategic Planning for Wireless Networks 43 is defined by the user, the identified metrics, as well as the equipment capabilities. It can be defined as the individual link data throughput, the aggregate throughput on a link under load, or the average or peak load on a network. Then metrics must be identified and the network monitored to ensure the network performs as designed. It is very useful if performance monitoring is built into the network plan from the beginning and can be added as a requirement in the overall WiFi network contract. However, it is possible, but both more complicated and expensive, to add it later. An important contractual element in any agreement with a contractor hired to manage the network is that the airport authority have unfiltered access to network performance data. One of the most effective methods for monitor- ing network performance is to build it into the core network. This means the data are gathered by equipment installed and owned by the network operator. Why should a contractor give data to an airport manager that may not reflect well on the com- pany and may result in the airport manager requiring them to spend time and money improv- ing performance? They probably will not unless there is a specific requirement in the contract that the company provide unfiltered data. If the relationship between the network operator and airport authority is a healthy one, then any differences in interests on network performance will be more situational rather than structural. In the long run, both the network operator and airport manager want the network to operate near its peak performance and meet all operational design performance criteria. However, at a moment in time it might be quite inconvenient or completely impossible for a network opera- tor to have the entire network at peak performance. This can be seen when there is a need to upgrade to a new version of the IEEE 802.11 standard, such as moving to IEEE 802.11ac. Many network operators are already installing equipment that supports IEEE 802.11ac and most air- port authorities are giving them a reasonable period of time for this technology transition. The speed with which the network operator upgrades to IEEE 802.11ac could be a point of conten- tion between the two. In general, airport authorities and network operators seem to be finding mutually acceptable timeframes for the upgrade. Automated Network Management Companies as well as individual users have become increasingly aware of the many factors that are involved in providing quality wireless control. Technological advances with wireless in general and WiFi in particular are a routine fact-of-life. Each development in turn is heralded as the cure for all ills. The reality typically is far more mundane. Change occurs so quickly in telecommunications that static plans or manual adjustments to a WiFi network often cannot keep up. The network must be able to manage itself, making near real- time changes in response to the changing situation and demands that it confronts. WiFi equipment vendors are actively developing a variety of automated network management tools to allow WiFi networks to sense and adjust to their environments and the traffic loads placed on them. Using automated network management is necessary now and will be increasingly important with the growing and changing variety of uses of the WiFi network and the proliferation of wireless devices. However, some of the network automation introduced to the market has fallen short of its prom- ise and at times even caused more problems than it solved. It is not unusual to find a new approach to automation developed with only one type of network environment in mind. In a different type of environment, the automation may be problematic or simply not adaptable to the challenge. A particular shortcoming in some automated network management tools brought to the mar- ket so far is to assume that everyone will use the same architecture and network design that the programmers are accustomed to. There are many different ways to architect a WiFi network.
44 A Guidebook for Mitigating Disruptive WiFi Interference at Airports Some organizations will run one physical network but several logical networks, separated by different SSIDs or virtual private networks (VPNs). The balance between coverage and capacity can be very different. When the network automation is developed assuming one type of network architecture, but the network planners implemented a different architecture, there can be real problems. Some automation has shown a tendency to misallocate channels and/or power levels, leading to system instability and a variety of performance problems. Some automated network management software will have WiFi access points automatically lower their power levels to avoid interference with other access points. The decision is typically based on access points measuring the signal level of their neighboring access points and then keeping that signal level below a predefined limit. However, this doesnât take into account the area an access point was installed to cover. A poor client experience can result if the lower power for the area covered provides the user with an inadequate signal. An example is a long hallway with access points installed along its length. Each access point is intended to provide signal into the rooms to either side of the hall, but there will be losses through the walls, furniture, and objects in the rooms. However, the access points have direct line-of-sight to each other. If the access points lower their power to avoid interfering with each other, the result could be insuf- ficient signal strength into the rooms the access point is intended to cover. Automated channel selection, intended to ensure that access points use channels that are sepa- rated in frequency, have in some cases been found to assign several access points in the same area to the same channel. In other cases, feedback loops have been created in which some access points change to avoid interfering with others. However, when access points change channels, their new frequencies can cause other access points to change channels and the chain reaction continuesâ with access points continually changing channels trying to get out of each otherâs way. The result can be constant change and an incredible loading on the network for no purpose. This is a seri- ous issue; in some installations the problems became so bad that the network manager had the automated network removed, because the access points were continuously switching channels in an attempt to find a channel without noise. The challenge is that there is always noise in dense networks, so automated channel-selection algorithms need to configure the network for the lower interference over time, while also allowing a level of interference that will always exist. A useful technique is to look at the channel plan on an access point management console. Superimposing the channel numbers used over the building floor plan makes it relatively easy to evaluate the result of the automated channel assignments. Are all of the allowed channels being used? Are the channels evenly allocated within the area? Are neighboring access points using different channels? Because the channel assignment software will change assignments, it is useful to recheck the plan periodically. Improperly allocated channel assignments can result in a significant lack of capacity and other performance degradation. The assigned power levels should also be checked. In some cases, it has been found that the automated control has all the access points operating at very low power levels, sometimes as low as 0 dBmâonly 1 milliwatt. These checks should also be repeated periodically and particularly during times when the network is more heavily loaded. With the growing complexity and dynamic nature of WiFi networks, control automation is becoming an integral component. However, it needs to be checked and monitored as a routine part of managing the network until confidence is established. Changes to the control automation should initiate additional monitoring to ensure continued confidence in the tools. Returning to manual control of WiFi networks might be feasible for smaller airports, but it will be increasingly unworkable for major airports in the future.
