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 (3x3 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.
It is important because it allows for easy backwards compatibility to provide continued support for 802.11n devices and older Wi-Fi devices. ‘Our approach with multi-radio arrays, or even the dual-radio arrays, is that I can set up each radio resource and customise it or programme it the base of clients I have to support. You can mix and match the radios inside the modular chassis array, but still use a single array infrastructure,’ says Miller. ‘That way you don’t have to add new arrays and install new cable runs.’
‘If I am serving a public venue like a stadium where 80%-90% of the users have a smartphone, or a school where most of them will have tablets or laptops, some of which might be quite old, using 802.11a/b, for example, I can programme the radios to match the client base. I can then continue to track the user base, see what devices they are using and change the radios over time as their devices get upgraded.
‘So, you have the flexibility to do a partial upgrade and then maybe a full upgrade,’ says Miller. ‘The technology is moving too fast, so unless you have the budget to change your hardware every two years you will not be able to match the motion of the market.’
Miller says there is big education job still to be done on Wi-Fi. Perhaps the key one is to inform clients that installing a Wi-Fi LAN is not all about coverage. Being able to handle the density of users and the kinds of applications they wish to engage, particularly high bandwidth guzzling video streaming, is also vital. And to do that, clients need to look at the entire end-to-end systems and not just the front end radios.
One of the most important aspects is to ensure that the Ethernet pipe itself is large enough to handle the density of simultaneous users.
‘The impact of many simultaneous users accessing high bandwidth applications on the network though will ripple through if you still only have a 100Mb Ethernet pulled to all your APs. It starts to create choke points, so you will need to move to at least a 1Gb Internet pipe – our high end products support 10Gb – and depending on the amount of capacity needed, you may want to look at even faster uplinks. So, you need to consider the back end too, the switches and the Internet pipe itself,’ advises Miller. ‘If you are going to invest in supporting all these devices, you have to ensure that the entire network is up to speed.’
Miller says Xirrus sees a huge disparity in how Wi-Fi is deployed and this comes back to the need for education. ‘It is not just about coverage. You need the full end-to-end network to support the service and a lot of networks are not designed with the full end-to-end capability in mind.
‘You have to put in more equipment to get a better signal, as smartphones need a better signal than laptops do, but you then also have to consider how many users you are going to have. That means you have to design the network in a way that will work. You can’t skip that; it is not just about the front end radios; customers need to be wary of vendors who undersell.’
As an example, Miller refers to a recent tender for a primary school in the US. 15 resellers responded with quotes ranging from $1.3 million at the high end down to $150,000 at the low end. Not only that, a number of Wi-Fi vendors were represented twice via different resellers at a roughly 2 to 1 ratio.
One competitor’s system was bid at roughly $750,000 and $350,000 by different resellers. For Miller, this shows that the design of the network was dramatically different even among resellers who are supposedly versed or trained on how to sell that particular product. ‘What that means is at least one of them lowballed that design by not putting in enough equipment,’ he says.
‘Wireless is very different from an Ethernet solution, because you don’t have this specific user base orientation to your design, running two cables to connect two people per cubicle say. You have to design it on coverage, so resellers bid aggressively to win, and therefore underbid. But it doesn’t make any sense that when two resellers are bidding the same vendor equipment, one has twice as much equipment as the other, even though the requirement is the same,’ points out Miller.
Another RF consideration with 802.11ac is aggregated channels. The original 802.11a standard in the 2.4GHz band had a total of 24 non-overlapping channels available. But every time the channel width is widened to achieve higher data rates, it comes at the cost of making fewer channels available.
There are even fewer channels available in the 5GHz band. Moving to 80MHz reduces the number of channels to just two and if 160MHz channels are used, just one is available.
‘You have to ask how you deal with that,’ says Miller. ‘Do I support full bandwidth with channels everywhere or have some radios support that and some that don’t. So, in a Xirrus 8-radio array, I might programme two radios to provide full 80Mb bandwidth 802.11ac to support 802.11ac laptops. I might then programme two more to support a non-aggregated channel to run my older devices on and then another couple of radios to support 2.4GHz only devices, for example.’
Miller points out that you can mix and match the technologies, because now you have even wider variety of legacy Wi-Fi standards to support, but what you don’t want to do is mix them up within the same radio channel, as the older devices will slow down the new fast devices. Instead, you spread support for different Wi-Fi devices across different radios.
While the RF considerations are naturally important to Wi-Fi, the application layer is also vital to its future development. ‘It’s not just about meeting the coverage and capacity demands, it’s about delivering a good user experience,’ says Miller, ‘especially now that video is becoming so huge.’
He cites the instance of Instagram adding the ability to send video clips in June 2013. In one day it allegedly became the No.1 OTT video service surpassing even YouTube, so wireless networks are going to have to step up to provide a service that can handle this demand.
‘Our approach is to look at the application layer,’ says Miller. We provide a tool called Application Control with all our products, which recognises the nature of the app be it YouTube, Instagram or Netflix and you can prioritise or de-prioritise it. A corporation running business critical applications such as SAP or Oracle, for example, we can recognise that and prioritise it over social media, streaming video, BitTorrent or whatever.’
Policies can be set that provide the CEO or staff using applications that are crucial to the business, such transacting financial information, taking orders, with a higher priority accesss than someone looking at social media.
‘We look at that information and add it to our policy context. We know who the user is, what device he has, what app he is running and even his location. I have a lot of context to enable me to ensure the guest in the lobby has low priority and the CEO gets top priority,’ says Miller.
Schools need acceptable use policies, so certain apps can be entirely blocked or just blocked at certain times. Facebook might be permissible for posting, but not for playing the games on it. Xiirrus’s technology enables policy managers to not just distinguish the app, but what is inside the app and be able to block aspects of it.
‘This is a key aspect of Wi-Fi now,' says Miller. 'It is not just about understanding how to deal with the RF level to provide fair access to users, but doing that at a user and application context level. You have to understand what is important to the business and map it to the business decision making in terms of priorities. Wi-Fi is set up to be fair for everyone, but it is not actually what you want.’
Intelligence at the edge
Xirrus has been able to achieve this granular view by using its distributed architecture approach. Computing power and intelligence are installed in the actual APs right at the edge of the network, as that is where the users are. This avoids the necessity of having to refer decision making back to the core using a central controller.
‘When we turn on Application Control at the edge of the network we’ve seen some customers save 30% of the bandwidth on the core and that will ultimately save bandwidth on the Internet uplink which is what they are actually paying for,’ points out Miller.
‘If you don’t have to pull everything back into the core, the decision making and authorisation to move from one AP to another is done at the edge - and it is good for scalability too,’ he says.
Five years ago, when a much smaller amount of bandwidth was being consumed, a centralised control system was a good solution, especially for security. ‘But now traffic is so much greater you have to look at distributed architectures or else you do not have the ability to scale,’ argues Miller.
He points out that those controllers/central gateways can be expensive and if there is a single point of failure that can be disastrous, unless the customer has invested in additional equipment to support redundancy, but that can mean a significant amount of money. ‘The industry is moving away from the thin AP and centralised controller approach, it just doesn’t scale as well, and now 802.11ac takes it further,' says Miller.
Value added services
Xirrus took a distributed approach from the beginning and now has a platform with a lot of computing and memory resources in every AP or array at the edge of the network, which it can use to provide additional services. Providing application visibility is one of those things, but by partnering with third parties it can add more.
For example, one of the largest exhibition venues in the US, the Sands Convention Centre in Las Vegas, (2.2million sq ft) has ubiquitous Wi-Fi across its whole estate. It is talking about providing a way finding application so visitors can navigate to an exhibitor’s booth. Once at the booth, customised content can be pushed to the visitor’s device based on their proximity to that location. Instead of picking up a brochure it will pop up onto your bookshelf.
Proximity service advertising is another common service too. These kinds of services help monetise the Wi-Fi network and can provide a good return on investment. Miller cites a US hotel that makes $1 million a year on its network by providing tiered business services; free access to guest, but if you pay you get better bandwidth or additional services over the top, for example.
Retail is another much discussed business vertical. The real-time, contextual information provided by Xirrus’s Application Control can provide very useful analytics on customer behaviours and show which aisles/areas have the most traffic. This enables the retailer to make much more informed and intelligent decisions about where to place product, kiosks, or maybe advertising space for which it can charge premiums for adverts in areas with the highest customer pass by.
Looking ahead, Miller sees Xirrus increasingly exploiting the computing power it has at the edge of the network. ‘As we move down the road, it becomes less about deploying RF and the Internet pipes to get access on there. We think we have solved that better than most with our distributed architecture, our ability to scale up easily and in the ways we can customise the arrays to meet the actual user requirements in different parts of a building or area.
‘We feel our modular approach puts us in a good position to keep up with technical advances and allow our customers to upgrade when they are ready. But the future will also be about including the additional services on top that give value to the customer. This will be more and more interesting. We have also boosted our outdoor products and this is a growing area for Wi-Fi deployments, especially with carriers looking to offload traffic onto Wi-Fi.’
Miller also sees the Wi-Fi Broadband Alliance’s Next Generation Hotspot (automatic, seamless roaming between cellular and Wi-Fi networks) underpinned by the Wi-Fi Alliance’s Passpoint programme for certifying NGH-enabled equipment, as being a good growth driver for Wi-Fi in general.
‘We think our platform is well suited for that, as we have the ability to scale up to large numbers and high densities and support that both indoors and outdoors. Wi-Fi is showing up everywhere, it is like a utility,’ says Miller. Good news for any Wi-Fi vendor able to move fast enough to keep up with the pace of technological change and provide a consistently good user experience.