The University of Iowa’s WiFi service is one of the larger wireless network implementations in higher education. There are many challenges in delivering this service over such a large geographic area to such a great many and diverse set of clients. The purpose of this document is to briefly explain the challenges and set reasonable expectations for the service.
Basic Factors Effecting Service Quality
There are six basic factors that determine the quality of your WiFi experience:
- The installed infrastructure in an area (i.e., the number and placement of wireless access points).
- The number of wireless clients in an area.
- The types of clients in an area.
- Limitations of the WiFi protocols.
- The level of radio interference in an area.
- An individual client’s wireless hardware and software.
Of these six factors, only one is under the control of ITS, which is the level of infrastructure installed in an area.
There are two sets of frequencies allocated by the FCC for WiFi, some in the 2.4GHz range, and some in 5 GHz range. A single access point can serve approximately thirty 2.4 GHz clients and fifty 5 GHz clients. This limit is primarily due to WiFi protocol design, and it is not a factor that ITS can change.
Increasing the number of clients supported in an area is not always as simple as adding additional access points. A maximum of three 2.4 GHz radios can be installed in close proximity, which means a maximum of ninety 2.4 GHz clients can be served in any given area. The limit of three neighboring 2.4GHz radios is due to the number of available non-overlapping wireless channels allocated by the FCC and supported in WiFi products. All 2.4 GHz WiFi clients in the U.S. are limited to these three non-overlapping channels. Adding more than three 2.4 GHz radios in close proximity can actually decrease network performance by causing interference. ITS cannot change these protocol or regulatory limitations.
More bandwidth is available when using the 5 GHz band, so more clients can be reasonably supported per radio. However, some wireless clients on campus are not 5 GHz capable, and many that are choose to use 2.4 GHz due to poor software implementation on the client. There is a limit of twenty-three non-overlapping 5 GHz (using 20 MHz) channels . It is possible in some cases to install more than 23 access points, but that involves trade-offs and risks that are difficult to explain briefly. In the general case, this means a maximum of 1015 5 GHz clients can be supported in any given area. ITS cannot change these protocol or regulatory limitations.
Wireless is a “shared medium,” which means that the clients in an area are sharing bandwidth. The bandwidth resources are finite, so as you increase the number of clients in an area, the slower the network will perform for all clients. There is no fairness mechanism built into the WiFi protocols, so it is possible for a single client to consume most of the available bandwidth. One implication of this is that signal strength and connection speed do not sufficiently reflect what a client’s WiFi experience will be like. One or several wireless clients in the vicinity could be consuming most of the available bandwidth in an area, so that other clients with a strong connection experience very slow performance. Nearby clients can be on the floors above and below or horizontally adjacent. This shared allocation of bandwidth resources is by protocol design, so it is not a factor that ITS can change.
Interference also plays a major role in the quality of the user experience. The radio frequencies used for WiFi are also used by many other types of devices. These devices include cordless phones, wireless headsets, wireless microphones, wireless cameras, etc. When these devices are in operation in the same vicinity as a WiFi network, they cause interference. Interference can also come from sources that are not intentionally operating at WiFi frequencies, such as microwaves. The presence of interference can result in a client showing a connection but not being able to perform network operations, slowing down network operations, or completely disconnecting the client from the wireless infrastructure. Interference is often transient, which makes it difficult to find the source.
Wireless client software and hardware also play a significant role in your WiFi experience. Radio characteristics and power vary greatly across client types. It is possible for two different WiFi devices right next to each to have very different WiFi experiences. Client drivers, software that control client radios, have historically been a major source of wireless problems.
The primary factor that ITS can change is the number and placement of WiFi access points. The initial WiFi deployment on campus was designed to maximize coverage area without addressing capacity. Over the years, as the number of client devices on the wireless network has grown significantly, ITS has engineered the network to handle capacity as well.
What is ITS doing to help?
ITS is working on several strategies to improve the wireless service.
- ITS has upgraded every WiFi access point across campus to support 802.11ac in the 5 GHz band. This significantly increased the basic capacity of every WiFi location on campus, providing an improved WiFi experience for many clients.
- ITS has expanded the number of access points in high density areas (classrooms and lecture halls) to help alleviate wireless congestion.
- ITS is using technology provided by our Wireless Vendor (Aruba) to steer clients that are capable of 5 GHz operation away from 2.4 GHz. While this effort cannot fully mitigate for poorly written client drivers, but it will help alleviate congestion in the 2.4 GHz frequency range.
- ITS is working with our wireless vendor (Aruba) to evenly balance clients across access points in the same area using vendor proprietary strategies.
- ITS is maintaining a relationship with the University’s academic community, so that we can improve communication and service to faculty.
How to Maximize Your Success when Using WiFi
Although there are many challenges for large groups of WiFi users in a given area (such as a classroom), there are many things you can do to maximize your potential for success.
- Contact ITS regarding the WiFi capacity of your classroom. If you plan on your students making heavy use of WiFi in the classroom, please contact ITS with the classroom location and class size. ITS should be able to make a preliminary assessment of the number of WiFi clients your classroom should reasonably support. You can contact ITS with this question for by sending email to ITS-NetworkServices@uiowa.edu
- Have a backup plan. There are many factors that go into the reliability and available bandwidth of the campus WiFi service, most of which cannot be centrally controlled. WiFi clients in adjacent hallways and classrooms (including above and below) can consume the bandwidth of access points servicing your classroom. Service interruptions from interference will likely not be resolved during your class. It is best to have a backup plan. Wireless should work most of the time, but due to nature of the medium, it is not possible to guarantee service availability.
- Turn off unnecessary clients. Ask your students to turn off or put to sleep smart phones (such as iPhones and Android-based phones), iPods, and any other WiFi enabled devices that are not being used as part of the class.
- Encourage the use of devices capable of 5 GHz. 2.4 GHz frequencies are generally more congested and traditionally have more sources of interference, so ITS encourages everyone use 5 GHz capable clients. Most modern wireless devices are now capable of both 2.4 and 5 GHz operation.
- Encourage students to update wireless drivers. The driver is the piece of software that controls the operation of the WiFi radio on the client. Many issues can be resolved by upgrading to the latest version of software. Client issues are among the top reasons for wireless service problems, especially in large enterprise environments.
What to do when WiFi doesn’t work?
If you are experiencing a WiFi problem, please contact the ITS Help Desk for assistance.