The A to Z of wireless
Updated: Everything you need to know from A to Zigbee, and plenty in between...
From using your mobile phone on a plane to surfing the net while you down a pint in the pub, wireless is revolutionising the way we do business.
But it's no longer just a question of untethering your PC from its peripherals or logging on at a coffee shop between meetings - new use cases for wireless technologies are making broadband available over distances of many miles and even, perhaps one day, on the London Underground.
As one of the fastest evolving spheres of technology, keeping on top of wireless developments is no easy matter - where to start? Bluetooth or WiMax, Zigbee or NFC?
There are so many different flavours of wireless standards and devices out there that it can be really hard to keep track - so let silicon.com be your guide to the unwired world.
We've put together this handy guide that will give you wireless from A right through to Z, to keep you up to speed on the tech.
So check out our encyclopaedia of wireless for your crash course on all the must-know wireless topics - from wireless' very beginnings to the technologies of the future.
A is for Aeroplanes
The prospect of wireless internet access on aeroplanes has been talked about for several years with Boeing first to launch a service - called Connexion. It debuted in 2004 on a few international carriers, only to be shuttered at the end of 2006.
Despite the closure of Connexion, analysts are predicting that in-flight wireless will take off in a big way this year: a recent report from analyst house In-Stat predicts the number of aeroplanes enabled for in-flight broadband will balloon from 25 in 2008 to around 800 in 2009 - a percentage increase of more than 3,000 per cent.
Indeed, momentum has once again been building around in-flight wireless and services are sporadically emerging: British Airways, for example, recently announced plans to launch an in-flight wireless service later this year on an all-business class route from London City airport to New York JFK but said it has no plans to retrofit the wi-fi kit on aircraft already in service.
Travellers on the route will only be able to text, email and browse the web using the service. Limiting functionality in this way can be a less controversial option for airlines as voice calls can present a noise nuisance issue.
In-flight connectivity is delivered via onboard picocell technology, with a satellite link connecting the aircraft to mobile networks on the ground. Aircraft must also install a network control unit to prevent onboard phones trying to connect with land-based cellular networks which are not designed to cope with such high speed movement, and also to ensure mobiles do not interfere with cabin equipment.
B is for Bluetooth
Bluetooth is a wireless protocol that operates in the unlicensed 2.4 GHz ISM radio frequency band. It enables devices to communicate information over short distances and is typically used as a way of connecting devices without the need for cables.
The tech has been around for more than a decade and is used in a multitude of consumer electronics, including mobile phones, laptops, hands-free headsets, games consoles and even printers.
More than two billion Bluetooth-enabled devices are estimated to have shipped globally, according to the Bluetooth Special Interest Group (SIG) the organisation that drives the development and marketing of the technology.
The key selling point for the technology is ease of use - Bluetooth enables ad hoc networking and the creation of personal area networks on-the-fly, with minimal configuration and without the need for line-of-sight between the various gadgets.
Bluetooth has also recently got a speed boost thanks to the latest version of the standard: version 3.0 can transmit data at speeds of up to around 24Mbps, a considerable jump from its predecessor (Bluetooth 2.1), which was limited to a maximum of 3Mbps.
The speed hike comes from the inclusion of the 802.11 radio protocol - the basis for wi-fi - which means Bluetooth 3.0 gadgets will be able to make use of any wi-fi radios to speed up larger data transfers, switching the wi-fi on to do the deed and then off again afterwards to conserve power.
Such a move not only brings greater data transfer rates for Bluetooth users but may also help ensure the proliferation of wi-fi radios do not cause Bluetooth to become obsolete.
As well as bringing greater speed, the 3.0 standard is also less power draining than its predecessors and the SIG reckons consumer products featuring the standard will hit the market at the end of this year or early next.
A Bluetooth headset (Photo credit: The_Ladd via Flickr.com under the following Creative Commons licence)
C is for Caio report
The Caio report is a major government-commissioned independent review into the delivery of next-generation broadband access in the UK, published in September 2008.
The report concluded a patchwork of fixed and wireless technologies will ultimately deliver next-gen broadband in Blighty, meaning cellular networks are being lined up for a significant role in delivering future national broadband needs, alongside the likes of fixed offerings such as fibre.
The prospect of a full fibre to the home rollout is prohibitively expensive - estimated at £28.8bn - and Caio, an ex-Cable & Wireless exec, is confident that developments in wireless speed and bandwidth will mean mobile networks will be crucial to future broadband delivery.
The report states: "The speed and bandwidth that mobile networks offer today is similar to the performance of DSL… three to four years ago. Radio technology is expected to continue its progress and to deliver in three to five years speeds that can be materially higher than current access networks and, as such, can be regarded as an integral part of the NGA [next-generation access] infrastructure."
Caio also recommends the UK government accelerates the release of radio spectrum to favour the development of new wireless broadband services. Following on from Caio's report, the government's Digital Britain report makes recommendations around wireless radio spectrum modernisation to ensure there is enough spectrum to service mobile broadband and to help deliver a 2Mbps broadband to all UK homes and businesses by 2012.
D is for Dual-mode phones
Dual mode smartphones are those which include a wi-fi chipset as well as a cellular radio. Such devices enable mobile users to get fast and potentially cheap internet access via wi-fi hotspots and/or home wi-fi routers.
Analyst In-Stat says 56 million cellular-wi-fi phones units were shipped in 2008 - an increase of 52 per cent on the year before.
The increase in dual-mode phones opens up the possibility of fixed-mobile convergence (FMC) - where one phone can be used to make calls over both cellular and fixed broadband networks, switching between the two where necessary. Voice calls can be routed over broadband using VoIP when in range of a wi-fi hotspot - enabling FMC users to cut call costs.
Supermarket giant Tesco has already caught on to the trend, inking a £100m network overhaul deal last year. The deal, with C&W, includes FMC and the retailer hopes it will save £10m per year.
C&W is not the only telco pushing the technology. An early attempt by BT to interest the consumer market in a dual mode wi-fi handset - marketed under the Fusion brand - was not an overwhelming success.
A business version of the service proved more popular however and analysts predict business use of dual mode handsets will rise as companies converge fixed and mobile communications to cut costs.
Cost is not the only selling point of FMC: it can also help improve reception. 3G signals can often be lower quality indoors, where wi-fi thrives, so in mobile blackspots dual-mode users need not be without coverage.
E is for 802.16e
802.16e is the mobile flavour of the 802.16 family of WiMax wireless standards (see W is for WiMax) and was ratified by the IEEE at the end of 2005.
LTE - the likely 4G evolution path of cellular technologies - and mobile WiMax are often discussed as competing techs - in a 'there can be only one winner' vein.
However, some analysts believe the two techs could both end up being part of a 4G future - a possibility made more likely by the International Telecommunication Union's 2007 decision to include WiMax in the IMT-2000 set of standards, alongside cellular technologies.
WiMax arguably has a head-start over LTE in the short-term - the technology has been used in real-world rollouts, unlike LTE. However, the mobile industry seems to be converging behind LTE and analysts predict it will eventually dominate.
Aside from mobile operators' seeming fondness for LTE, barriers to rolling out WiMax include spectrum availability (see S is for Spectrum) and chipset adoption.
However 802.16e is likely to remain in use in certain regions where large-scale cellular investment is unattractive. Tech lobby group the WiMax Forum claims WiMax's open standards-based approach can mean networks are cheaper to build than cellular 3G/4G equivalents - which could give it a leg up in developing nations and/or rural regions where investment budgets are limited.
F is for FON
FON is the company behind a wi-fi sharing venture that gives its members access to hundreds of thousands of wi-fi hotspots.
FON users - known as Foneros - agree to securely share a portion of their home internet connection with other members and in return gain access to the other Foneros' wi-fi, with speeds capped at up to 512Kbps.
The business was launched in Spain in 2005 and the wi-fi company went on to sign an agreement with BT that saw the telco offer FON membership to all of its broadband customers.
According to BT, there are now in excess of 100,000 hotspots in the UK - and more than 250,000 worldwide.
By agreeing to share wi-fi resources web users can help spread wireless connectivity in towns and villages without the need for companies or councils to stump up cash to fund equivalent municipal networks.
Financial backers of FON include Google and Skype - both companies with obvious incentives to ramp up web access.
FON advert in San Francisco (Photo credit: Steve Rhodes via Flickr.com under the following Creative Commons licence)
G is for GPS
Global Positioning System (GPS) is a US satellite system used to pinpoint exact locations, and is best known for its in-car use.
Business applications of the technology include real-time parcel tracking services that work by monitoring the GPS signals from the delivery firm's vehicles. Parents can also use the tracking tech to keep tabs on where their child's school bus is.
GPS is also becoming an increasingly common feature of smartphones such as Apple's 3G iPhone 3G S.
With forecasts predicting GPS chip shipments will reach one billion globally by 2013, analysts expect GPS to enable an era of mobile location-based services - a scenario that Nokia has made a big bet on, shelling out $8.1bn back in 2007 to acquire digital-map supplier Navteq whose map data is used by portable GPS makers such as Garmin.
Another major GPS-style system-in-the-making is Galileo, currently being developed by the European Space Agency with funding from the EC and some European Union member states.
The idea behind Galileo is to provide Europe with an independent alternative to US and Russian GPS systems - although Galileo will interoperate with both GPS and Glonass (the Russian system) respectively.
Construction of Galileo is underway, with around £1.3bn having been spent on it so far. A further investment of £2.7bn is planned - and the EC hopes Galileo will be fully operational by 2012.
Galileo is slated to offer much more precise location tracking than GPS currently can, so potential applications could include road-use charging schemes and helping emergency services to locate missing or injured people.
Another reason to invest in an alternative to GPS is a recent US Government Accountability Office report that suggests the service may face interruptions next year owing to ageing satellites and failures to launch new ones on time.
A scale model of a GPS satellite (Photo credit: cliff1066 via Flickr.com under the following Creative Commons licence)
H is for History
Today the term 'wireless' is a loose one, covering a diverse range of technologies - from mobile phone networks and wi-fi to WiMax and LTE.
The history of wireless is littered with exotically named physicists and inventors all playing their part in the development of the communications landscape - but there remains controversy over who invented wireless telephony.
In 1888, experimental physicist Heinrich Hertz built apparatus capable of receiving electromagnetic waves and thereby confirmed their existence.
However Hertz, who lends his name to the measure of radio frequency, did not envisage any practical applications for his discovery, so it was left to others to pick up the baton and take the technology forward, including radio pioneers Guglielmo Marconi and Nikola Tesla.
While Tesla was awarded the first basic patent for radio, in 1897 Marconi sent the first ever wireless communication over a few kilometres of open sea - a message asking "Are you ready?" By the start of the 20th century he was able to send the first transatlantic transmission, using kite-supported antenna, demonstrating that radiowaves could indeed travel thousands of kilometres.
With Marconi making such public waves the US Patent Office reversed its decision in his favour and awarded the patent to him. However, in the mid-20th century, the US Supreme Court upheld Tesla as the patent holder and he is now recognised as the inventor of radio (for more on Tesla see J is for Juice).
Patent disputes also surround the invention of the telephone - with both Alexander Graham Bell and Elisha Gray submitting patent applications on the same date: Valentine's day,1876. Bell's application prevailed, despite apparently arriving hours later than Gray's.
Bell is credited with making the first proper telephone call, on 10 March 1876, asking his assistant Thomas Watson to "come here".
When it comes to mobile technology the story is similarly complex, with developments taking place in different countries at various times although the concept of cellular tech as we know it today kicked off in 1940s US, with Bell Labs' idea of a network of cell sites (base stations) that hand off calls to one another conceived in 1947.
Their idea was for multiple low-power transmitters spread throughout a city in a hexagonal grid with automatic hand-off between cells - the foundation of the modern mobile network. However, Bell Labs had to wait until the 1960s for technology to catch up with their vision and even then, in the US, the Federal Communications Commission (FCC) did not approve the overall concept - and allocate frequencies to make it possible - until the 1980s.
The brick-like Motorola DynaTAC 8000X was the first commercial mobile handset, gaining FCC approval in 1983.
However Europe set up the first commercial public mobile network called ARP and launched in Finland in 1971. Early mobiles used on ARP were so big they needed a car to carry them around, with the phone filling the car boot and a handset wired up front next to the driver.
Today there are now more than four billion mobile connections globally - a massive number that is only set to rise, while Ericsson predicts there will be 50 billion connections by 2020 as mobile connectivity is embedded not just into mobiles but everyday items.
Wi-fi or wireless LAN is a more recent phenomenon. The original version of the standard IEEE 802.11 was released in 1997. Vic Hayes, an electrical engineer by training, set up and oversaw the IEEE standards group for wireless LAN (aka 802.11) in the 1990s - and has thus been dubbed the father of wi-fi.
I is for Indoors
With the rise of mobile data carried on 3G networks, indoor mobile coverage has become a thorny issue for operators.
People want to use their phones indoors for data - watching video, browsing the web, and so on - but in-building coverage for data can be patchy.
It's fundamentally a spectrum problem: 3G spectrum tends to occupy high frequency bands which are much worse at penetrating buildings than 2G (GSM) spectrum. (See S is for Spectrum).
Building out mobile networks to ensure high quality 3G coverage indoors would be an expensive business for operators.
However, there are alternatives: common or garden wi-fi has been picking up some of the indoor slack as more smartphones come with an embedded wi-fi radio (see D is for Dual mode). Using wi-fi where available can also be a faster way of consuming data on your mobile and reduces data download costs that can still be extortionate.
Indoor mobile base stations - aka femtocells - are also being looked at by mobile operators as a way of offloading 3G traffic by routing it onto a user's broadband connection - albeit ultimately a DSL line.
J is for Juice
The holy grail of the modern wireless world is surely the ability to cut the last cord and power devices wirelessly - sometimes referred to as wireless energy transfer.
The concept of wireless power is by no means a new idea: in the late 1800s the inventor Nikola Tesla demonstrated a form of wireless energy transmission powering a lightbulb - the so-called Tesla effect. But despite this early interest, the potential for wireless power has gone untapped, with tech-driven societies relying instead on batteries and plug-in chargers.
However momentum now seems to be building behind the concept: a few years ago scientists at MIT also demonstrated wireless energy transfer powering a lightbulb by using magnetically coupled resonant objects. The technology - dubbed WiTricity - uses copper coils in the transmitters and receivers which, because they are tuned to the same frequency as each other, are able to exchange energy efficiently with minimal energy leakage into the surrounding environment or to non-coupled objects.
A not-for-profit organisation - the Wireless Power Consortium - was established at the back end of last year "to drive convenience in electronics charging" and establish standards, with member companies including Olympus, Philips, Sanyo and Texas Instruments.
Chipmaker Qualcomm is also convinced by the potential of wireless power, recently showing a photograph of a prototype wireless charging tray to power mobiles and any other relevant gadgets placed on it.
Inventor Nikola Tesla (Photo credit: jorel314 via Flickr.com under the following Creative Commons licence)
K is for Kip Meek
Kip Meek is chairman of the Broadband Stakeholder Group and the UK government's independent spectrum adviser.
Meek's role has been to broker agreement among the mobile operators over the reallocation of 2G spectrum so that Lord Carter's dreams of 2Mbps broadband for all Britons can be realised.
In his interim Digital Britain report, comms minister at the time, Stephen Carter, announced a Wireless Radio Spectrum Modernisation Programme - led by Meek - to resolve the future of 2G spectrum.
In the report, Carter states a preference for the mobile operators to agree to trade the spectrum among themselves, rather than government imposing "realignment".
In May Meek published a report into the spectrum measures needed to facilitate Digital Britain. His "preferred mechanisms" included capping ownership of spectrum among mobile operators so they could hold on to the spectrum they own but would need to sell it before buying any more: a give some, get some approach, if you will.
The report recommended holders of 800MHz spectrum could also be given regional coverage and access obligations to ensure nationwide coverage for the next generation mobile services.
The auctions for 2.6GHz spectrum should also be held at the same time as the 800MHz auction, in mid 2010, to help new entrants get into the market, according to Meek's report.
In addition, Meek has called for a slice of 2.6GHz spectrum suitable for WiMax to be auctioned off sooner, to give those operators a leg-up into a wireless world dominated by cellular players.
In its final Digital Britain report, the government says it "accepts the essentials" of Meek's report but does tinker with the size and structure of his capping mechanisms.
It is also further defers decisions on how much 900MHz spectrum holders will be required to give up in order to acquire 800MHz spectrum - seeking "guiding technical arbitration on the refarming of 900 spectrum before taking a final view on the ratio".
See S is for Spectrum for more.
L is for Location
GPS isn't the only wireless tech that can be used to determine users' locations: wi-fi has its place too.
Wireless positioning systems typically work by sniffing out wi-fi hotspots, analysing the signal strength of several access points and querying an access point database to pinpoint the user's location - to within accuracy of some 10 to 20 metres.
Using wi-fi for determining location has advantages over GPS (See G is for GPS) inside buildings - where satellite positioning systems break down.
It can also perform better in dense urban areas or during periods of bad weather which can adversely affect satellite positioning systems.
The future of location tech looks likely to be in hybrid systems.
Such systems could incorporate several location positioning technologies - such as GPS, wi-fi positioning and mobile phone signal triangulation - switching between technologies in order to provide the most accurate location in the user's current situation.
M is for Mesh networks
A mesh network is a network made up of a series of nodes (small radio transmitters) that route data to each other and to network users through 802.11 wi-fi standards.
A core advantage of such a network is resilience: if one node fails the others pick up the slack as data hops dynamically from node to node, thereby bypassing any breaks, until the destination is reached. Mesh networks are also self-organising so new nodes are automatically assimilated into the collective, as it were.
While mesh networks can be wired or wireless, the latter type of mesh is useful for building out large areas of connectivity - say in a city where meshes can be used to link up existing wi-fi hotspots and fill in connectivity notspots. London's Square Mile has its own mesh network - launched in 2007 - consisting of 127 nodes built into lampposts and the like.
Wireless mesh networks can also be a less expensive way of delivering connectivity to communities in the developing world than wired networks as they avoid the need to install fixed-line infrastructure.
The mesh component also means linked machines share an internet connection - a useful feature in regions where connectivity is scarce. The responsibility for upkeep and maintenance of network infrastructure is also shared, avoiding any single point of failure.
Nicholas Negroponte's grand One Laptop Per Child (OLPC) plan to put netbooks into the hands of children in developing nations had high hopes for wireless mesh networking.
The XO machines made by the OLPC come with built-in wi-fi antennas designed to automatically create a mesh network with other XOs within a distance of around a third of a mile.
However the mesh networking component of the XOs has not always lived up to the original 'out of the box' connectivity vision. Speaking in an interview with silicon.com last year, David Cavallo, chief learning architect for the OLPC, said there had been problems getting the networks up and running - including dealing with large numbers of XOs in the bigger schools.
Future uses of ad hoc mesh networks could include connected cars which are able to inform each other of upcoming hazards or traffic jams.
Click here to read silicon.com's Cheat Sheet on wireless mesh networking.
XO laptops being used on a women's mountaineering expedition to Everest (Photo credit: One Laptop Per Child via Flickr.com under the following Creative Commons licence)
N is for 802.11n
802.11n is a proposed amendment to the 802.11 wi-fi networking standard. Colloquially at least, the n stands for 'next generation' - as the standard will bring faster networks, which have greater coverage and boast more bandwidth than their predecessors, the 802.11g networks.
Demand for video streaming and wireless VoIP are two key drivers for 802.11n and analyst house Gartner is tipping the standard as 'one to watch' - because of its disruptive potential to enable the all-wireless office.
"802.11n is the first wi-fi technology to offer performance on a par with the 100Mbps Ethernet commonly used for wired connections to office PCs. It is, therefore, an enabler for the all-wireless office, and should be considered by companies equipping new offices or replacing older 802.11a/b/g systems in 2009 and 2010," the analyst has said.
The 802.11n amendment incorporates Mimo (multiple-input multiple-output) technology - use of multiple antennas at both the transmitter and receiver sites - to boost data throughput rates.
Although 802.11n won't be finalised until 2010, some wireless kit makers already have products based on the draft 802.11n spec.
O is for Oyster
Transport for London's (TfL) Oyster card is a smartcard ticketing system that uses RFID technology (see R is for RFID) to speed up travel through ticket barriers.
Unlike paper tickets, which contain a magnetic strip and must be passed through readers inside ticket barriers, Oyster uses contactless technology so the cards only have to be passed over a reader on the top of the barriers.
Use of smartcard ticketing is seen as a more attractive alternative to paper technology as prepayment and travelcards can be bought online and stored on the cards. As a result, queuing at ticket offices is reduced and TfL staff are freed up for other duties.
In order to encourage customers to get on board, TfL offers commuters cheaper travel on Oyster.
The Oyster system, launched back in 2002, has not been without its glitches - a computer bug was blamed for crashing the system during the morning rush-hour back in 2005 and, more recently in summer last year, the system crashed twice in a fortnight.
Dutch researchers have also claimed there are vulnerabilities with the Mifare Classic chipset used on the cards that could enable criminals to clone Oyster cards (see V is for Vulnerabilities).
The future for smartcard ticketing systems could lie with mobiles. Back in 2007 mobile operator O2 launched a six-month pilot of a phone that came with Oyster functionality.
Testers simply had to touch their phone to the Oyster reader to use it as a ticket for travel on London's transport network and at the end of the trial the majority said they were interested in taking up a mobile Oyster app in future. However the launch of a commercial Oyster phone - or app - in the UK is likely to be several years away.
P is for Piggybacking
The flip side of wi-fi sharing (see F is for FON) is wireless piggybacking - stealing connectivity by logging on to an unsecured wi-fi network.
A moneysupermarket.com survey last year found more than one in 10 people admitted to using someone else's internet connection without permission, while 16 per cent said they had failed to password-protect their own wireless connection leaving it open to piggybackers.
Legislation covering wi-fi theft is set out in The UK Communications Act 2003 Chapter 21, Section 125 refers to "Dishonestly obtaining electronic communications services" and states:
"(1) A person who -
(a) dishonestly obtains an electronic communications service, and
(b) does so with intent to avoid payment of a charge applicable to the provision of that service,
is guilty of an offence."
The penalty for being convicted of wi-fi piggybacking under this Act is up to five years in jail or a fine, or both.
However not all silicon.com readers believe wi-fi piggybacking should be considered criminal - with some happy to share with strangers and others saying the onus should be on network admins to secure their own wireless routers in the same way a homeowner always locks their front door.
Wi-fi sharing community company FON offers a legal way to share someone else's wi-fi (see F is for FON).
Who's logging on to your wi-fi? (Photo credit: Noonch via Flickr.com under the following Creative Commons licence)
Q is for Quality of service
Quality of service (QoS) in a wireless context means the guarantee of a minimum level of service for a wireless product or service. Any number of elements can make up QoS with things like bandwidth, jitter and error rate among the most common.
QoS is often used to make sure certain types of traffic receive sufficient priority on the network - VoIP or streamed multimedia content such as videoconferencing, for example.
With QoS, bandwidth can be guaranteed for such time-sensitive voice services on the network, while users with less real-time requirements can be made to wait.
Where QoS has been implemented on a wireless network someone could download a large presentation file, for instance, without degrading the quality of a teleconference.
802.11e - an approved amendment to the 802.11 wireless standard - has tackled QoS with a set of enhancements for wireless LAN applications designed to prioritise time-sensitive categories of traffic.
R is for RFID
Radio frequency identification tags are tiny microchips equipped with antennae allowing data - typically a unique code or identifier - to be transferred wirelessly to a reader.
The tags are typically attached to objects to enable machines to automatically identify what they are. However, tags have also been attached to animals and even humans.
RFID tags can be passive or active. Active tags incorporate a battery meaning data can be transmitted over greater distances than their passive counterparts. Passive tags are smaller and cheaper - having no battery and relying on drawing power from the RFID reader instead - but they need to be brought much closer to the reader as a result. Passive tags typically have a very long shelf life (of up to a decade) but are able to store less data than the more expensive active tags.
As well as being contactless, RFID does not require line-of-sight between tag and reader - making it a more flexible technology than the more common (and much less expensive) alternative: barcodes.
However RFID's cost per tag is still too high for retailers to ditch barcodes - and instead RFID tends to be used for inventory of larger items, such as pallets in warehouses, or to keep track of more costly goods, such as military equipment.
The technology has applications outside supply chain management too. Back in 2006 the UK government introduced a RFID chipped passport using the chip to store a facial biometric of the passport holder, along with basic ID information contained on the paper passport. Second generation ePassports, due to be introduced in 2011/12, will have a chip containing fingerprint scans and personal details.
The financial services industry is also interested in RFID. Earlier this year, Barclays bank announced it would be replacing all debit and credit cards by 2011 with ones that incorporate a RFID chip to enable contactless payments.
Close up of an RFID chip inside a credit card keychain (Photo credit: oskay via Flickr.com under the following Creative Commons licence)
S is for Spectrum
Radio spectrum is the Kate Moss of the wireless world - many people desire it; few can afford it; fewer still will ever get a whiff of it. But it's powerful and valuable stuff: UK telecoms regulator Ofcom estimates business activity that is largely dependent on spectrum contributes £37bn, or three per cent, of the UK's GDP.
Ofcom is tasked with overseeing UK spectrum usage to, among other things, prevent interference between different wireless devices. It also runs auctions to sell swathes of spectrum when it becomes available.
The characteristics of spectrum bands vary - with some being more desirable to power mainstream comms technologies owing to the radiowaves' ability to travel long distances and more easily penetrate buildings. For instance, the likes of FM and digital radio, mobile phones and satellite TV operate in the higher frequency bands (between 30MHz to 30GHz), with very low frequency bands reserved for niche uses such as submarine comms.
Ofcom dubs spectrum below 15GHz as "the most sought after and congested frequencies". But arguably the most valuable spectrum lies in the so-called sweet spot of the UHF (Ultra High Frequency) band: the 300MHz to 3GHz tranche.
One UHF section, in the frequencies 470MHz to 862MHz, will soon be freed up for auction by the switching off of the analogue TV services in 2012 as television broadcasts go fully digital.
This spectrum, known as the Digital Dividend, is particularly attractive to mobile operators as the longer wavelengths would mean a network using the spectrum would need fewer base stations to generate a good signal - ergo cheaper network infrastructure. The spectrum's in-building coverage is better too.
But it's not just mobile operators that the Digital Dividend could appeal to: suitable uses for this spectrum could include WiMax, mobile television and broadband, local TV stations and additional Freeview channels, according to Ofcom.
Unlike some of its previous spectrum auctions the regulator has decided to auction the Digital Dividend spectrum on a "service-neutral basis", so technology developments that could use the spectrum aren't hamstrung by restrictions on what it can be used for.
T is for Telemetry
Telemetry and telematics refers to the automatic monitoring, measuring and transmission of data.
Vehicle telemetry is one of the best known wireless applications of the tech, where it's used for fleet management - tracking how far a vehicle has travelled, at what speed or how much fuel it's consumed for example.
Vehicle telemetry can also be used for freight storage logistics and has already been deployed in Formula 1, where real-time data on race vehicles' performance is gathered to calculate potential lap times.
Wildlife tracking and monitoring can also take advantage of telemetry, where scientists can wirelessly monitor endangered species or study migration patterns. Weather stations that gather information on the local climate in remote regions are another application of wireless or radio telematics.
Telemetry often utilises M2M - or machine-to-machine - communications, transmitting small amounts of data between devices without human interaction.
Such data can be used to track items or monitor environments: for example, in a refrigerated lorry, sensors in the storage compartment could detect when the temperature is too high and communicate this to a device that could cool the compartment to the correct level.
With M2M making use of cellular networks for data transfer, mobile operators are becoming increasingly interested in the market's potential to create new revenue streams. Last year analyst house Berg Insight predicted there will be almost 60 million connected machines by 2013 and urged mobile operators to "position themselves for the future" and get involved.
Kestrel wearing telemetry (Photo credit: Jason Riedy via Flickr.com under the following Creative Commons licence)
U is for Underground
While mobile network coverage does not currently extend to Tube tunnels, Transport for London (TfL) has previously mooted plans to bring connectivity to stations and trains, issuing a tender for the Waterloo & City line back in 2007.
However TfL told silicon.com earlier this year that the company has yet to receive a "credible proposal" for pushing out mobile coverage to the line, adding that "the unique nature and environment of the Tube mean that project costs would be prohibitively high at this time".
However, in an unexpected twist, the government's comms minister Lord Carter championed the cause of Underground mobiles in his Digital Britain report - flagging up the Tube as a coverage blackspot and calling for it to be plugged in time for the 2012 Olympics.
The report adds that the government is willing to address any regulatory or "similar constraints" that might be acting as a barrier to an Underground deployment. However there's still no cash on the table so an imminent Tube rollout does not seem any more likely.
While commuters may not yet have wireless comms on the Tube, London's emergency services are already able to speak to each other when on the London Underground. Earlier this year the Airwave emergency services comms system was rolled out to the whole of the Underground network meaning police and other emergency services personnel don't have to send staff above ground to radio for help.
The project saved cash by piggybacking on the existing Connect digital trunk system, used for communication by TfL workers, rather than building an entirely new infrastructure.
Passengers on Glasgow's subway are also getting mobile connectivity underground. Wireless network vendor Arqiva is in the process of hooking up the city's 15 subway stations via a distributed antenna system that could also be used to roll out wi-fi connectivity at stations in future.
V is for Vulnerabilities
A range of encryption protocols are in use to prevent hackers and other ne'er-do-wells from getting into company networks.
WEP (aka wired equivalent privacy) was the first wireless encryption standard but is now considered to be the weakest protocol. That doesn't mean it's not still in use however - a survey at the start of this year found a quarter of retailers still using WEP. Even more worryingly, around a third of the retailer access points probed were found to be entirely unencrypted.
The dangers of not shoring up a wireless network with adequate encryption were amply illustrated by the massive data breach suffered by retail chain TJX which came to light in 2007. The company was only using WEP on its WLANs which meant hackers were able to steal 45 million customer records over a period of around two years, including millions of credit card numbers. Once they had cracked the encryption, they were able to collect the user names and passwords of staff as they logged in and then set up their own accounts to collect transaction data.
The problem with WEP is that while it does encrypt data it only uses a static encryption key so if hackers intercept enough packets they can crack the key. It can be done remarkably quickly with the right tools: the FBI, for instance, has demonstrated a three-minute crack of WEP.
The latest wi-fi security protocol available is WPA2 - wi-fi protected access version 2 - which changes the encryption key with every data packet sent rather than having a static key. It also uses a different encryption protocol to WEP and also incorporates technology aimed at sniffing out imposter packets trying to sneak onto the network.
One reason companies may be seen to be dragging their feet on wireless security and using older, less secure protection is that WPA2 requires compatible hardware which can mean having to buy new equipment.
W is for WiMax
WiMax is a long-range wireless broadband standard, often compared to wi-fi on steroids.
Unlike wi-fi, WiMax uses licensed spectrum but, also unlike its wireless cousin, works over distances of many miles, rather than just within rooms in a building. It has a maximum range of around 30 miles and is typically used to provide connectivity to metropolitan areas.
WiMax offers a last-mile alternative to fixed-line broadband - for instance it can be deployed to bring broadband services to rural 'notspots' unserved by fixed-line infrastructure, typically where laying copper or fibre would be seen as too costly.
WiMax can also be used to provide backhaul for wireless base stations - be they cellular, wi-fi or mobile WiMax.
Various WiMax networks are up and running globally - in the UK, for example, WiMax company Freedom4 has networks in Manchester, Milton Keynes and Warwick running on the 3.6GHz spectrum band.
Mobile WiMax has been mooted as a rival carrier technology to the next-gen evolution of cellular networks (aka 4G or LTE). For mobile WiMax, the standard is 802.16e: a version of WiMax that supports mobility and is theoretically capable of symmetrical speeds up to 70Mbps - see E is for 802.16e.
X is for X-ray
Could nano-sized wireless devices drift around our veins and arteries in the not-too-distant future - monitoring the human body from within, transmitting health data and sending alerts in the event of medical emergencies such as a heart attack?
According to a 2008 report by UK telecoms regulator Ofcom, such wireless in-body technologies could make it out of the research labs in the next decade or two.
Ofcom reckons in-body networks could be implanted in patients to monitor their movements and/or vital health signs, such as blood sugar level.
Having gathered the information, the network could send it wirelessly via a home broadband hub or portable monitor to keep doctors informed of patients' progress.
Another medical use of wireless technology that's already in use are wireless detectors for digital X-rays systems - which convert X-ray radiation to digital image data.
Such gadgets make it more easy to X-ray certain areas of the body or less mobile patients as the detector can be brought to the patient rather than vice versa.
Y is for Yikes
The growth in wireless networks has led to concerns about whether there are adverse health effects from continued low-level exposure to the electromagnetic fields networks create.
Wi-fi health jitters have even led to wireless networks being removed from schools and universities.
However a 2006 World Health Organisation (WHO) fact sheet reviewing the scientific evidence of any health effects resulting from exposure to both mobile phone base stations and other local wireless networks concludes there is currently no evidence of health risks.
"Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF [radio frequency] signals from [mobile] base stations and wireless networks cause adverse health effects," the report states.
According to the WHO, the only scientifically proven health effect of exposure to RF signals is a very slight increase in body temperature - and only then from very high field intensity radio frequency waves, more powerful than even those emitted from mobile base stations.
Wireless networks, being orders of magnitude weaker still, should be even less of a worry, the report concludes.
"Since wireless networks produce generally lower RF signals than base stations, no adverse health effects are expected from exposure to them," it states.
However owing to the lack of long-term health impact studies of wireless networks - and the difficulty in conclusively proving there is zero risk from exposure to anything - the debate about health risks is likely to rumble on for a while yet.
silicon.com columnist Peter Cochrane has no such doubts. Writing in a blog post last year he points out: "Radio emissions are not at all like ionising X-rays that can blow cells apart. So, as adequately demonstrated by our overall survival and ability to live with electromagnetic radiation for almost 100 years, there isn't a real problem with wireless radiation anyway."
Click here to read more of Cochrane's views on electromagnetic health risks.
Z is for ZigBee
ZigBee is a low-power, low-cost open wireless standard. It operates in unlicensed spectrum and enables everyday devices to connect wirelessly to the internet and transmit and receive data.
While it may lose out to fellow personal area network tech Bluetooth in the speed stakes, being limited to a maximum of 250Kbps, it wins on the power front, consuming significantly less energy.
ZigBee is especially suited to remote monitoring and control, as well as sensory network applications. It can also support mesh networks (see M is for Mesh network) - the self-healing properties of which are considered well suited to ZigBee's world of remote, always-on, low-powered sensors.
Typical hardware uses include smart meters, thermostats, medical data monitors, smoke or burglar alarm systems, building or home automation gadgets and domotics (the use of robot and computer technology in domestic appliances).
Some industry watchers however believe ZigBee is becoming increasingly focused on a single use-case: smart metering. Even so, smart metering could still be a substantial market, with the UK government recently announcing a plan for a smart meter to be installed in every home by 2020.
A smart meter (Photo credit: cote via Flickr.com under the following Creative Commons licence)
silicon.com's Tim Ferguson contributed to this report