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SECURITY

Wireless Connections: What You Need To Know (Part 2)

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Wi-Fi, Bluetooth, 2.4GHz, Miracast and more: Darien Graham-Smith explains each of today's numerous wireless standards

A similar concept is the 802.11ad protocol, branded “WiGig” after the Wireless Gigabit Alliance that developed it (now incorporated into the Wi-Fi Alliance). WiGig can use low-frequency communications to talk to a device that’s 10m away on the other side of a wall, or automatically switch up to 60GHz to communicate with a device sitting right next to the transceiver at up to 7Gbits/sec. The technology hasn’t caught on in the mainstream, but the USB Implementers Forum is working on a new approach to wireless USB that will function over WiGig as well as Wi-Fi networks, so the technology could yet have its day.

WiGig can use low-frequency communications to talk to a device that’s 10m away

WiGig can use low-frequency communications to talk to a device that’s 10m away

A more advanced wireless interconnect is Wi-Fi Direct, a standard that lets any number of Wi-Fi-equipped devices exchange files and information directly, rather than having to go through a router. Only one device needs to support Wi-Fi Direct - the others will simply see it as a regular access point - but range and bandwidth will depend on the hardware, and on which Wi-Fi standard is being used (we’ll get into these issues later). Many smartphones and tablets can act as hosts, as can the Xbox One; you can already buy mice, loudspeakers and printers that support Wi-Fi Direct connections.

Wireless display

The Miracast standard lets you transmit video wirelessly to a TV or monitor by sending an H.264-compressed stream over an 802.11n Wi-Fi Direct link. Support is already built into a number of Android devices, and recent Ultrabooks that support Intel’s own WiDi wireless-display technology can talk directly to Miracast-compatible displays. OS support is built into Windows 8.1.

The Miracast button displays the EZMirror screen 

The Miracast button displays the EZMirror screen

Few TVs are directly compatible with Miracast, but you can buy a receiver for around £60 that plugs into your TV via an HDMI cable. The catch is latency: it takes time for the transmitting device to encode the video stream, and more time for the receiver to decode it again.

Officially, Intel’s latest drivers cut this down to 60ms, but we’ve seen external displays lag behind the built-in one by up to a second. That’s fine for presentations and movies, but a disaster for games.

Apple devices don’t currently support Miracast, but the proprietary AirPlay system does a similar job, letting you use a television to mirror the screen of a Mac or iOS device. A selection of receivers is available, with prices starting at around £30; you can also use an Apple TV appliance.

Ad hoc connections

The first and the most important design decision that we made was to adopt the paradigm of ad hoc communication

The first and the most important design decision that
we made was to adopt the paradigm of ad hoc communication

Some wireless technologies aren’t intended for persistent connections, but for ad hoc data sharing. The most extreme example of this is the radio-frequency identification (RFID) tag - a tiny transmitter that shares a single piece of programmed information with any receiver that comes near to it. RFID technology is commonly used for access management, so an automated door might open only when it detects an RFID tag with a valid identity, or a reader on a London bus might use the RFID chip embedded in your Oyster card to log your journey. Contactless payment systems work in the same way, and modern UK passports include an embedded RFID tag detailing the holder’s personal information, since this is quicker to read electronically and harder to falsify than a printed page.

 

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