The latest Wi-Fi standard, 802.11ac, will bring speeds of more than 1 Gigabit, but as Bruce Miller, VP, Product Marketing at Xirrus, explains to James Atkinson networks need to be deployed in the right way if the challenge of meeting high density usage is to be met
Wi-Fi vendors are just beginning to ship the first products featuring the new 802.11ac Wave 1 standard. It is the first Wi-Fi standard to use the 5GHz unlicensed spectrum band, rather than the 2.4GHz band, which has been used up to now. It will increase speeds from around 400Mbps achieved by the current 802.11n to 1.3Gbps.
Wi-Fi equipment provider Xirrus has not quite got its first generation 802.11ac products out to market yet, but they have been available for pre-order since last year and will be shipping in the next quarter.
Bruce Miller, Vice President, Product Marketing at Xirrus, explains: ‘We announced a deal last year whereby if customers pre-ordered 802.11ac arrays and access points (APs) they could have them at a discount – the same price as our current 802.11n APs, in fact. So, although we won’t be first to market with our products we have already sold hundreds of them.’
Pace of change
Miller notes that Wi-Fi rolls out a new technology every two years and that means new arrays and APs and a correspondingly, new devices appearing on networks. The latest Apple Mac Books are already 802.11ac Wave 1 enabled, for example, but only a few smartphones are 11ac ready at the moment.
‘Replacing hardware every two years is not a good way of doing things, however,’ points out Miller. ‘Some convention centres do have two-year upgrades in their budgets, as they want to be cutting edge and support the latest devices. But most customers do not have the budget to do this of course.’
Nor do they want to go through the hassle of ripping out and replacing their Wi-Fi systems unless and until they have to. Mindful of this, Xirrus has developed a modular approach, which allows you to open up the chassis and swap out the radios inside for the latest technology.
Its XR range of wireless arrays goes from a two radio-slot chassis to a 16 radio-slot chassis. If more radios are needed, the chassis can be replaced with a larger one but using the same site and cable connections.
‘Our platform can therefore support three or four generations of technologies,’ says Miller. ‘You have a switch in a closet that you can slide blades into, so that way we can support a five-year replacement strategy that is about average for most customers. Customers slot into the product line as it suits their requirements and they might wait a generation and jump to another depending where they are in their buying cycle.’
Key features of 802.11ac
The 802.11ac Wave 1 standard was formally certified by the Wi-Fi Alliance in June 2013. It is capable of delivering speeds of 1.3Gbps thanks to the addition of a third spatial stream (3×3 MIMO), a doubling of the channel width from 802.11n’s 40MHz to 80MHz, an increase from 64QAM (quadrature amplitude modulation) to 256QAM, which increases the bit rate density (the way bits are carried within the RF wave), and beamforming technology. Beamforming allows the signal energy to be directed much more tightly resulting in more reliable links between APs and devices.
802.11ac Wave 2 is likely to be certified towards the end of 2014 with products coming to market in 2015. This will add a further fourth spatial stream, allow for 160MHz channels and introduces multi-user MIMO. MU-MIMO is the really clever stuff in that it allows a Wi-Fi array or AP to direct simultaneous transmissions to up to four different clients at full channel data rates.
Supplying broadband via an Ethernet connection is essentially quite simple; each user has their own dedicated connection to the Internet. But in Wi-Fi all the users are sharing the same port, or access point, in this case and somehow they must all be provided with ‘fair access’ and, if possible, a good user experience.
‘This is why Wi-Fi is fundamentally trickier,’ says Miller. ‘Multi-user MIMO is moving towards something like a switch architecture, but in the end it is still a given radio that is sharing that bandwidth, so it won’t fix that problem in the end. Users still have to share that same space at the same time. I won’t be able to talk to 30 devices at the same time with MU-MIMO on one radio – it will be less than that.
‘2015 is where 802.11ac Wave 2 will start to take off and our products will support that given our modularity. But with our solution you can also mix and match different Wi-Fi radio standards and that’s important,’ says Miller.