WiFi definition

WiFi technology (IEEE802.11) can be broadly categorised to IEEE802.11 a/b/g/n/ac. Each is an improvement in transmission speed and/or signal range from the previous, although these days only ‘G’ and ‘N’ are used.

The standard G versions of networking devices have an optimal transmission speed of 54 Mbps with an indoor range of approximately 40 m whereas the N versions have a theoretical maximum speed of 300 Mbps (practical of approximately 150 Mbps and above) with an indoor range in the region of 70 m.

In addition to this, N variations offer the choice of two frequency ranges; 2.4 GHz or 5 GHz. The higher frequency has no impact on the range but offers a potentially less polluted frequency to help reduce crosstalk noise.

Both the G and the N devices utilise the same channel capabilities but these vary regionally. In Europe (including UK) a channel system of 1-13 is used whereas in the US the system uses 1-11. Both use the same frequency ranges resulting in an approximate frequency void of 16.5 MHz at the end of the 2.4 GHz range.

Japan utilise a different system still, expanding the 2.4 GHz range beyond the acceptable ISM guidelines by 10.5 MHz to allow for an additional 14th channel with 11 MHz of non-interference from other channels (see Figure below) [80], [81], [82].

Image. 22MHz channel allocations for WiFi 2.4GHz frequencies, with curvatures implying affinities for intra-channel frequency selection.

The figure above shows the affinities for the frequency selection within each 22 MHz channel and the overlap between channel frequencies. The same would be seen for 40 MHz channels with the obvious exception that there would be twice the amount of overlap between channels, leaving fewer isolated channels. The solid lines show the 3 channels in the US 11 channel system that do not encroach on each other’s range at all. Each WiFi access point will secure its own channel and use that channel for all communications. Multiple channels will not be utilised by one access point other than during overlap.

WiFi communication protocols are Internet Protocol (IP) based where the destination address is in packet headers allowing large amounts of data to be transmitted through a network of nodes at high speed. This means that on any WiFi network a central control node (network coordinator) will allocate all IP’s in the network on discovery allowing for any packets to be addressed and routed to a connected device [82].

This article was created by --BRE. It was taken from The future of electricity in domestic buildings, a review, by Andrew Williams, published in November 2014.

NB The term 'WiFi' was coined by the Wi-Fi Alliance as shorthand for wireless local area network (WLAN) products based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards. It did not specifically 'stand for' anything. It has popularly been adopted to mean Wireless Fidelity but this is not correct.

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[edit] External references

[80] E. G. Villegas, E. López-Aguilera, R. Vidal and J. Paradells. Effect of adjacent-channel interference in IEEE 802.11 WLANs. Cognitive Radio Oriented Wireless Networks and Communications, Orlando, 2007.
[81] Butler J. Wireless Networking in the Developing World, Copenhagen: Creative Commons, 2013.
[82] Institute of Electrical and Electronics Engineering, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. IEEE Standards, 2012.

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Comments

WiFi does not stand for Wireless Fidelity. It is not an acronym. It is a term to define the ieee 802.11 standard.

WiFi was coined by the Wi-Fi Alliance as shorthand for wireless local area network (WLAN) products based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards. It did not specifically 'stand for' anything. It has popularly been adopted to mean Wireless Fidelity but this is not correct.