A service set identifier (SSID) is a unique code attached to all packets on a wireless network to identify each packet as part of that network. This code is a case sensitive text string that consists of a maximum of 32 alphanumeric characters. Wireless devices must share the same SSID if they want to communicate with each other.
Hence, in order to identify different Wi-Fi services in HKUST, we must use different SSIDs. A user with a wireless device must choose the right SSID in order to use the corresponding wireless service.
IEEE 802.11 is the wireless local area network (WLAN) standard developed by the Institute of Electrical and Electronics Engineers (IEEE). 802.11a, 802.11b and 802.11g are 3 most well-known 802.11 specifications.
802.11b and 802.11g standards use the 2.4 GHz radio frequency (RF) band. As many household appliances are operating in this frequency band, e.g. microwave ovens, cordless telephones and Bluetooth devices, 802.11b / 802.11g wireless devices may be susceptible to interference occasionally.
In contrast, 802.11a standard uses a different 5 GHz radio frequency band, which suffers less interference.
The table summarizes the difference among 802.11a, 802.11b and 802.11g.
| Protocol | Specification Release Date | Operating Frequency | Theoretical Data Rate | Theoretical Range (Indoor) | Theoretical Range (Outdoor) |
| 802.11a | 1999 | 5GHz | 54 Mbit/s | ~25 meters | ~75 meters |
| 802.11b | 1999 | 2.4GHz | 11 Mbit/s | ~45 meters | ~100 meters |
| 802.11g | 2003 | 2.4GHz | 54 Mbit/s | ~40 meters | ~95 meters |
The actual data throughput of a 802.11b connection can be up to 5-6 Mbit/s while actual data throughput of a 802.11g connection can be up to 20-22 Mbit/s. The actual bandwidth will be inversely proportional to the number of simultaneous surrounding users. Besides, RF interference may affect the quality of the wireless signal and hence the data throughput may be lowered.
802.11n builds upon previous 802.11 standards. The expected data throughput of a 802.11n connection is up to 300-600 Mbit/s, which is similar to the rate of a typical wired connection.
802.11n tries to increase the data rate by using MIMO (multiple-input multiple-output) technology which makes use of multiple transmitter and receiver antennae to transfer data. New coding schemes may be applied as well.
Wi-Fi Protected Access (WPA and WPA2) is a class of systems to secure Wi-Fi networks. They are designed to replace the deficient older Wired Equivalent Privacy (WEP) standard.
WPA implements the majority of the IEEE 802.11i standard, and was intended as an interim measure while 802.11i was being prepared.
WPA is designed for use with an IEEE 802.1X authentication server, which distributes different keys to each user. Data encryption is done through the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV). Temporal Key Integrity Protocol (TKIP) is used to change the keys dynamically. Besides, a more secure message integrity code (Michael) is used for better authentication.
WPA is designed to work with all wireless network interface cards, but not necessarily with first generation wireless access points.
WPA2 implements the mandatory elements of 802.11i. In addition to TKIP and the Michael algorithm, it introduces a new AES-based algorithm, CCMP, that is considered fully secure.
Note that WPA2 may not work with some older network cards.
Temporal Key Integrity Protocol (TKIP) is a security protocol used in Wi-Fi Protected Access (WPA). TKIP provides per-packet key mixing, a message integrity check and a rekeying mechanism.
Advanced Encryption Standard (AES) is a block cipher adopted as an encryption standard by the US government. AES encryption is used in WPA2 to enhance the security of wireless network.
Nowadays nearly all new notebook computers have built-in 802.11a/b/g wireless adapters.
However, the built-in wireless adapters on some old notebooks may support 802.11b only. Besides, some older notebooks have no built-in wireless adapters at all. In that case the users need to purchase wireless adapters. For better compatibility, Wi-Fi certified wireless hardware is much preferred.
Many handheld devices support 802.11b or even 802.11g as well. Users should refer to the manuals of the handheld devices accordingly.
Many people are concerned about the radio power of wireless devices and worry that they may be harmful to the bodies and may lead to health problems. In May 2007, ITSC and SEPO has worked together to conduct a measurement on the Wi-Fi radio power level at sampled HKUST Wi-Fi installations. The result indicates that all measurements are below the recommended level by ICNIRP standard and even lower than the power level by cellular phones. These all suggest that the Wi-Fi radio power in HKUST is safe to human beings.