1.2. Describe the impact of various wireless technologies
802.11 wireless LANs use unlicenced spectrum and therefore the signals can be affected by other devices and technologies that also use this spectrum. Wireless communication is generally divided into a number of categories, wireless LAN (WLAN) being the one we are mostly interested in but the others are Wireless Personal Area Networks (WPAN), Wireless Metropolitan Area Networks (WMAN) and Wireless Wide Area Networks (WWAN).
The spectrum allocated to 802.11 is in two bands, in the 2.4GHz and 5GHz range.
WPAN - a WPAN uses low-powered transmitters to create a network with a very short range, usually 20 to 30 feet (7 to 10 meters). WPANs are based on the IEEE 802.15 standard and include technologies like Bluetooth and ZigBee, although ZigBee can have a greater range.
WMAN - A wireless service over a large geographic area, such as all or a portion of a city. One common example, WiMAX, is based on the IEEE 802.16 standard. Licensed frequencies are commonly used although the specification does include use of the ISM band. No commercial deployments of WiMAX use the ISM band and for this reason is not a source of interference for wireless LANs.
WWAN - A wireless data service for mobile phones that is offered over a very large geographic area (regional, national, and even global) by telecommunications carriers. Licensed frequencies are used. Examples are 2G, 3G and 4G (LTE) mobile carrier networks. WWANs do not use the same frequencies as 802.11 and therefore are not a source of interference.
Bluetooth is a PAN technology, used mainly for telephony headsets and file transfer. Found on most laptops, tablets and mobile phones. Bluetooth has low power consumption, requires line of sight and has good security, making it a good choice for mobile, battery-powered devices.
Bluetooth developed by the Bluetooth Special Interest Group and was incorporated into the IEEE 802.15.1 standard, but that standard is no longer maintained.
Devices operate in the 2.4-GHz ISM band (2.402 to 2.480Ghz), but are not compatible with the 802.11 standard. Bluetooth uses a frequency hopping spread spectrum (FHSS) technique, with devices moving through a predefined sequence of 79 channels with a bandwidth of 1 MHz each.
Class 3 radios – have a range of up to 1 meter or 3 feet, power is 1mW
Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 33 feet, 2.5mW power
Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet, power is 100mW
Up to eight devices can be paired or linked into a PAN, with one device taking a master role and the others operating as slaves.
Bluetooth transmitters could potentially interfere with the majority of the 2.4-GHz band because their channels overlap with the three non-overlapping 802.11 channels but only at a close range because of their low transmit power. If there are many Bluetooth devices in an 802.11 cell, they can create a saturation effect.
Worldwide Interoperability for Microwave Access (WiMAX) is a wireless technology designed to provide “last mile” broadband access to consumers within a geographic area and defined in the IEEE 802.16 standard. WiMAX does not require line of sight and can provide connection up to 3 to 10-km.
WiMAX operates in several bands between 2 and 11 GHz and from 10 to 66 GHz and can possibly interfere with 802.11 devices, but such interference is highly unlikely. No widely deployed solutions use the ISM bands; the systems that are advertised for ISM are not supported by any major WiMAX players.
ZigBee is wireless mesh LAN technology that uses relatively low power consumption and low data rates (20 to 250 Kbps). As a result, it offers reliable communication. ZigBee is commonly used for energy management and home and building automation applications.
ZigBee is defined in the IEEE 802.15.4 standard. It allocates the 2.4-GHz ISM band into 16 channels of 5 MHz each. Even though ZigBee uses the same band as 802.11 devices, it has a low duty cycle.
1.2.4. Cordless phone
Cordless phones use several wireless technologies to connect remote handsets to a central base station, using TDMA and FDMA techniques. Phones operating in the 2.4- and 5.8-GHz bands can cause significant interference with nearby WLANs. Cordless phones can use one channel at a time, but can also change channels dynamically. As well, transmit power levels can rise up to 250 mW, overpowering an AP at maximum power however they typically do not use the ISM band.