Difficulties of Supporting Wi-Fi

1. Unstable Wi-Fi connection or wireless signal drops out frequently

   This problem is most possibly caused by a weak Wi-Fi signal or Radio Frequency (RF) interference.

   • A weak signal results in slow transfer speed and an unstable Wi-Fi connection. Reasons that may cause a weak signal problem include:
     • The Wi-Fi client is not attached to the nearest AP.
     • The nearest AP is not responding so that the Wi-Fi device has to associate to an AP farther apart.
     • New renovation or repartition work affects Wi-Fi signal strength, depending on the materials used and how they adsorb or reflect Wi-Fi signals (e.g. metal partitioning which is commonly used within campus).
     • User is situated in a blind spot that Wi-Fi signals can hardly reach

     Below are possible methods to resolve the problem:

     • Disable and then re-enable the Wi-Fi adapter to force the adapter to learn and associate to the nearest AP again.
     • Increase the transmit power of the Wi-Fi adapter of the client.
     • Report to the Computing Services Centre (CSC) for investigation. The CSC may need to restart a problematic AP (which may become stale for unknown reasons after serving for a long time), or install a new AP or relocate an AP to provide better coverage if the assessment warrants such changes (e.g. as a result of room repartitioning).
   • Strong RF interference. Though our Wi-Fi system has enabled the “Adaptive Radio Management” feature to automatically adjust the power of each AP connected to the system to minimize the interference among APs installed in the vicinity, RF interference is inevitable and hard to resolve because there are many devices operating at this same radio bands (2.4 GHz and 5GHz). If interference is serious, then users will experience slow transfer speed or even dropped Wi-Fi signals. Below are some of the devices that may cause interference:
     • Many wireless routers have been set up in the office for personal use, or mobile Wi-Fi hotspots have been enabled on some mobile devices to share their 3G/4G cellular networks (e.g. tethering) with other nearby mobile devices without CSC’s knowledge. Since such devices will degrade the Central Wi-Fi network performance, the CSC will ask the users to turn off such devices or functions once discovered.
     • Some electrical appliances such as microwave oven and Bluetooth devices are operating at the 2.4GHz band. Users may set their Wi-Fi devices to use 5GHz (e.g. 802.11a) to avoid or minimize interference.
   • Sometimes unstable Wi-Fi connections may be caused by outdated hardware device drivers installed. User should always update the operating system (OS) and device drivers to the latest versions to fix potential bugs and get optimized performance.

2. Unable to access the Internet or some web sites while users are successfully connected to Wi-Fi network

   Sometimes users may experience problems in accessing particular web sites or even the whole Internet. This may be a network or IP assignment problem.

   • The problem may be caused by uncontrollable Internet network problems, such as routing, DNS, DDOS attacks, etc., making some web sites inaccessible temporarily. Users may report the problem to the CSC to see if a workaround solution can be offered.
   • During peak hours, there are more than 11,000 concurrent users connecting to various Wi-Fi networks (“CityU WLAN (WPA)”, “Universities Wi-Fi”, etc.). Each network has its own IP pools to share among its users. Due to the unpredictable user population of each network, there are occasional chances that the IPs of a particular network have been exhausted; thus users may not be able to obtain an IP in time and hence cannot access the Internet. In this case, users may connect to another network instead. In fact, the CSC keeps monitoring the usage of each network from time to time and will adjust the number of IPs assigned to the pools when necessary.

3. Slow wireless speed

   One of the weaknesses of Wi-Fi networks is the slow transfer speed at peak hours.

   • Unlike the conventional Ethernet network whereby each user has dedicated 100 Mbps or higher connection speed, the total bandwidth of the wireless connections associated to the same AP is shared among all its connected users (theoretical 600 Mbps in 802.11n). Therefore the more the users, the less the bandwidth is allocated to each individual user. To get better transfer speed, users may consider changing to work in a less populated locations if appropriate.
   • Slow wireless speed may be caused by weak Wi-Fi signal strength or serious RF interference. See point 1 for more descriptions.

1. Problems related to Active Directory (AD) network accounts
   •  When users try to login their Wi-Fi accounts with a wrong password after 10 consecutive attempts, the AD accounts for authenticating the wireless LAN connection will be locked for 30 minutes.
   • After users have changed or reset their passwords on the AD server but forget to change the same on all their mobile devices. Just one (laptop, cell phone or tablet) mobile device with the old password (no longer valid) can cause the AD account lockout due to repeated login failure from the automatic connection retries. In cases where some users own a few mobile devices, they reflected that they were unable to identify which devices were attempting to login with the old password, so the AD accounts will just keep locking out.
   • The AD account lockout may be caused by sharing the EID with other users (although not allowed in IT Policy). As a result, users were unable to identify exactly which device(s) was causing the lockout.
   • There is a 180 days password expiry policy and if users forget to change the password before the expiry date, it may lead to a repeated failure in Wi-Fi login.
   • Due to a change of student status such as unsettled tuition fees or expired VISA, student accounts may be disabled and hence their Wi-Fi accounts may become unavailable for use.
   • If the user has mixed up the AD (Network), LDAP (Application) and Email (O365) passwords, it may also lead to a 30-minute account lockout or unsuccessful account login.
   • Improper use of Wi-Fi accounts such as P2P software and suspicious account activities may lead to Wi-Fi accounts being barred. Users will find out they can no longer log into any Wi-Fi network in CityU until they receive the notification email.
2. Wi-Fi device-related problems
   • Over-protective anti-virus software, improper firewall settings and unknown software on students’ own computers may become the obstructions for connecting to Wi-Fi network.
   • Fixed IP address and DNS or other IP settings without “auto acquired” from DHCP server may lead to the failure of accessing the Internet.
   • Unsupported OS like Microsoft Windows XP, external Wi-Fi device driver on MAC OS or other previous Windows OS versions may cause the failure of certificate installation. Some Wi-Fi networks such as “CityU WLAN (WPA)”, “Eduroam” and “Universities Wi-Fi” which require encryptions will be unable to be connected by computers using the said OS.
   • Depending on the network card installed on the user’s device, it may affect the stability of the Wi-Fi connection. A situation whereby a user’s device receives a strong signal but experiences a disconnection might be caused by the unstable network card due to one of the followings:
     • User may have a corrupted connection profile or incorrect credentials stored in the profile. Users can remove the existing connection profile and recreate a new one.
     • Update the firmware of the Wi-Fi device or the device driver to the latest version.
     • The driver version may not support new WiFi standards or their support still have faults that need improvements.
   • User’s PC is Wi-Fi enabled but cannot learn any wireless network.
     • The wireless adapter is disabled in the OS.
     • Some devices have a hardware switch or using function keys or software to turn on/off the Wi-Fi adapter. The Wi-Fi adapter may be turned off accidentally.
   • One possibility of failing to connect to Wi-Fi is that the user devices may be infected by computer virus. The problem can most likely be resolved by performing a system recovery.
   • Some computers may encounter problems in accessing the Internet if they have multi-network cards and connections at the same time. Disable the unused one may solve the problem.
   • Even though a computer has Internet access, somehow it cannot successfully load a page in the browser. In this situation, the browser may be using an improper setting or plug-in. Resetting the browser or disabling the plugin may solve the problem.

1. Environmental difficulties to install new APs

   In general, installing new APs is an effective way to improve Wi-Fi coverage and to increase aggregate bandwidth to the users. The location of the new AP is often carefully chosen so as to maximize the coverage and minimize interference. However, owing to the existing obstacles, such as ducts, pipes, etc., the actual location available for installation is often far away from the ideal location, too high or hard to reach; resulting in the degradation of Wi-Fi performance and difficulty performing maintenance work.

2. Renovation work affects the coverage and increases difficulties in carrying out hardware maintenance tasks

   Depending on the materials used in the renovation and how the materials affect (reflect, absorb or filter) the radio frequency, very often the Wi-Fi performance is degraded after renovation work or room re-partitioning. The worst case is that the false ceilings were shielded without access panel beneath the AP for on-going hardware maintenance. Hence greatly increase our supporting effort and lengthen the repair time.

3. Wide varieties of Wi-Fi devices increase difficulties in providing support

   Most popular OS such as android, iOS, Microsoft Windows, etc. provide easy and consistent Wi-Fi connection interface to their users. However, not all OS are easy to use. Some devices are running on proprietary OS and the procedures for setting up a Wi-Fi connection may not be easy and straightforward. We need to spend extra efforts on searching the web and use “trial and error” methods to make them work with our wireless networks.

Although not all the problems can be resolved promptly and permanently, especially those intermittent and RF interference problems, the CSC will continuously keep improving CityU's Wi-Fi environment by installing adequate APs, adding support to new standards, optimizing the performance by upgrading the system firmware periodically and fixing potential problems.