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Wi-Fi was MEANT to be this way: Antennas and standards, 802.11 style

Plus: Why your phone's (sometimes) crap at wireless

Why phones aren’t always great at Wi-Fi

For all the advances being made in Wi-Fi access points in the last few years, the real weakness may not be in the equipment, or in the standards on which they are based. Rather, the limitations of small-format client devices may be the culprit for poor performance.

iPhone 4

iPhone 4: Notoriously poor signal

“The [IEEE 802.11ac] for the routers we can buy is great. You can push several hundred Mbits/sec. What we’ve found – and mobile manufacturers won’t like this – is that it’s the actual number of antennas and the number of devices [that’s the issue],” said Andrew Ferguson, founder of broadband and wireless analysis site ThinkBroadband.

Remember Antennagate, five years ago this coming June? When Apple launched the iPhone 4, poor network performance ended up being down to the positioning of the mobile antenna in the device. Apple famously asked people to avoid holding it the wrong way. It was a joke at the time, but it pointed to a real problem for mobile phone manufacturers: putting decent antennas in something the size of a very small packet of ciggies is hard.

“The old iPhone 5, you expect it to not be that great. You’d expect an iPhone 6 to be mega-fast. Not always. Even with ac, it will not be as fast as the Macbook Pro that also supports ac,” he added.

The IEEE standard 802.11ac was ratified in late 2013. Operating once again on the 5GHz band and with 80MHz channels, this has some unique properties, including wider channels. 802.11 breaks up the available spectrum into frequency channels that can be used to avoid access points clashing with each other.

“The move to AC was one of migrating to a cleaner 5GHz frequency band from the 2.4GHz frequency band that 802.11n covered,” said Dennis Huang, director of product marketing at enterprise-focused wireless access point vendor Meru Networks.

“We had to move to wider channels. 802.11n works with 40MHz channels, while 802.11ac works with 80MHz channels, doubling the amount of data that you can push down it.”

Along with other enhancements including better compression, this will get you up to 6.77Gbit/sec in theoretical aggregate capacity. However, theoretical and real capacity are typically different, as throughput speeds are mitigated by factors including environmental characteristics and error correction needs.

The Wi-Fi Alliance is currently working to certify another set of enhancements to 802.11ac, which will include a technology to solve the poor phone performance problem: multi-user MIMO (MU-MIMO).

The reason that your phone performs relatively poorly on a current 802.11n or 802.11ac access point is down to its design. The MIMO implementation in these access points will use multiple antennas to transmit independent data streams. But those antennas require more electrical power. Phones can’t usually afford that overhead, so they generally stick with one antenna against MIMO’s two, three, or four antennas.

If you’ve got a three-antenna access point, it’ll be great for your laptop which may have three antennas. Not so much for your phone, with one antenna, because the access point will use all three antennas to communicate with the phone, but the phone will only be able to receive a signal from one. Matthew Gast, director of advanced technology for Aerohive Networks, likens it to driving on a three-lane motorway but never being able to leave the inside lane.

“Even if you have an 802.11ac phone, it supports one stream. So no matter how good that phone is, it can only use one third of the spatial stream,” he said.

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