Breaking through barriers
Written by: Sam Fenwick | Published:

Wi-Fi is evolving to keep up with the boom in mobile device use in high density environments. Sam Fenwick has the details

In the cellular world 5G is just on the horizon and the same is true of 802.11ax – a new version of Wi-Fi, which is being developed as a standard in IEEE. It follows hot on the heels of 802.11ac wave 2, which was designed to allow Wi-Fi to better handle high-bandwidth applications running on an increasing number of devices. It achieves this through the introduction of multi-user MIMO, a doubling of the maximum channel bandwidth from 80 MHz to 160 MHz, the use of four spatial streams (up from three) and extended device support for channels in 5GHz.

802.11ax continues this direction of travel, with a focus on enhancing performance in dense and congested environments such as airports, train stations and stadiums. According to Intel, it’s expected to boost peak data rates for a single client device by up to 40 per cent and boost average throughput per user by at least four times in congested environments. One of the ways in which it will achieve this is through the use of downlink and uplink OFDMA (orthogonal frequency-division multiple access) – a key technique already used in LTE.

This, according to Oliver Bosshard, chief operations officer at Real Wireless, “is a potential game changer because it gives far more control of transmission scheduling on the wireless interface. The current approach of Carrier Sensing and Collision Avoidance struggles in high density areas where hundreds or thousands of devices try to access the same channel (the wireless interface) at the same time. They’ll keep trying to access it, find out that it’s used, back off and try again, which is highly inefficient. That’s going to improve a lot with 802.11ax due to OFDMA and other features. The radio channel is broken into subcarriers which can be assigned to individual users. You can tell the user device when to transmit on the uplink, coordinate it with downlink transmission and therefore get more control of the air interface.

“This extra control means that we can start to introduce improved quality of service and prioritisation, which is available with LTE for other latency-sensitive or operational-critical applications, and the performance of critical services won’t degrade the way it currently does when you have lots of users. Put in a nutshell, there is an increased level of device management resulting in more efficient sharing of the spectrum and users will see an improved quality of experience.”

Another benefit of 802.11ax is that traffic scheduling will improve battery life, while multi-user MIMO and higher modulation and coding schemes will allow greater spectral efficiency, “making 802.11ax far more LTE-alike.”

Bosshard says that this means that there could potentially be competition between Wi-Fi and MulteFire – the only LTE technology that operates purely in licence-exempt spectrum – especially in indoor or campus environments. One potential advantage MulteFire might have in this area is “that it can be connected into a Mobile Network Operator’s (MNO’s) core network, and so could potentially deliver the same voice and mobile broadband performance to the end users as if they were on the MNO’s network, using licensed spectrum. But Voice-over-Wi-Fi is improving and with 802.11ax, Wi-Fi could provide the same performance as MulteFire.”

Of course, one area where Wi-Fi and LTE work in conjunction is the offloading of traffic from MNOs’ networks onto Wi-Fi and Bosshard adds that it can be a “rather good alternative to mobile broadband” for enterprises and venues, given the cost and current complexity of providing reliable high capacity in-building LTE coverage. “Voice over Wi-Fi service is something that’s in use by many MNOs as an automatic fall-back option in the absence of cellular coverage – its performance is quite good already and it keeps on improving especially as Wi-Fi evolves,” he adds.

A good example of this was the network of more than 2,200 Wi-Fi access points deployed for this year’s Mobile World Congress, which were engineered by Cisco and Boingo to use Passpoint, a Next Generation Hotspot (NGH) technology that allow automatic and seamless connection to wireless networks. US operators, AT&T, Sprint and T-Mobile, pushed the majority of traffic to the city’s NGH hotspots and during the event the network carried more than 2.3 terabytes of data, while delivering speeds of up to 25 mbps.

Similarly, Qualcomm Technologies says its modems are designed to support automatic handoff between Wi-Fi and 4G/LTE depending on signal quality and Internet access, enabling higher quality calls and faster data streaming.

Although MNOs will have access to more spectrum in the 5G era, Bosshard expects that in “really dense urban and hotspot areas, Wi-Fi will still play a crucial role in offloading the MNOs’ networks and provide localised capacity.”

One other area where the blurring of the lines between Wi-Fi and LTE may occur is in the US with Citizens Broadband Radio Service (CBRS) shared spectrum in the 3.5 GHz band. Back in 2016, Ruckus Networks and Qualcomm demonstrated neutral host small cells that can operate in standalone mode, but can also be backhauled over Wi-Fi.

“Of course, you can use DAS for a huge environment – it’s economically viable for a stadia or something like that – but in most building environments it’s far more economic to deploy Wi-Fi and then backhaul the LTE across it, says Nick Watson, vice president EMEA at Ruckus Wireless.

He adds that Samsung and Apple have launched 3.5 GHz handsets and that Ruckus is in discussions with most of the governments across Europe, “the spectrum is different of course, but even so people have given us the ability to do some testing with 3.5 GHz in controlled environments. So, this [CBRS] is picking up quite a head of steam in the US and there’s a huge amount of interest in it across Europe and other parts of the world.”

Another thing to consider here is the concept of 5G as a network of networks, along with the way that millimetre-wave, ultra-dense deployments pose issues for installers and city councils alike. It’s a similar story for Wi-Fi. “We’re already deploying Wi-Fi devices on the outside of buildings but we’re also building our Wi-Fi devices to sit within street furniture such as streetlights and poles, and within bus shelters, so you get away from people objecting to these multiple ‘large carbuncles on the face of an old friend’ as Prince Charles said”, says Watson.

“As an example, in St Petersburg we [deployed Wi-Fi alongside] ER-Telecom and we had to do a number of things to make the devices blend in with the background.”

Watson adds that mesh networking is an enabler of these large high density deployments, but it is important to avoid multi-hops, as they can result in high or inconsistent latencies that can result in a poor user experience.

Pebbles before the avalanche
At the moment, we’re at the very beginning of the rollout of 802.11ax. For example, Aerohive Networks announced its intention to deliver three models of 802.11ax access point back in January and shipped its first 802.11ax access points to customers in Europe and US in late July. In addition, Ruckus Networks launched its R370 802.11ax access point on July 17 – which is designed to deliver high-resolution, latency-sensitive video in ultra-high density environments. Huawei launched its AP7060DN access point back in September 2017.

It’s worth noting though that the products released to date are based on the draft 802.11ax standard, which is not expected to be finalised by IEEE until late 2019. Development of the standard began back in July 2014 and has suffered from a couple of setbacks with two previous ballots failing to obtain the necessary majority, although the latest draft was passed with a majority of 86.5 per cent.

While this state of affairs is not ideal, a white paper from Aruba notes that “the precedents of 802.11n and 802.11ac indicate that the risk of early 802.11ax equipment becoming orphaned is very low,” and adds that vendors have successfully met the challenges associated with producing equipment prior to certification before.

According to a report from Dell’Oro Group that was published earlier this summer, the delays in rolling out 802.11ax products are expected to reduce the extent of Enterprise Class-WLAN market growth in 2018. “Several manufacturers of Enterprise-class products are postponing general availability of 802.11ax access points as they wait for more advanced chipsets and further development of the standard,” said Trent Dell’Oro, business analyst at Dell’Oro Group at the time. “In light of this news, we lowered our Enterprise-class access point forecast for 2018 by over six per cent. We imagine the market may come in lower than we predicted, depending on the degree to which customers push out projects as they wait for the new technology.”

User devices need upgrading
As Bosshard notes, for us to truly move into the 802.11ax era and reap its full benefits it has to be supported by user devices and “it will take a while for various parts to come together – the supply chain to offer 802.11ax in all standard user devices, a reasonable market penetration to be achieved and for the network infrastructure to be upgraded to 802.11ax – all of which will be necessary to get the best from this new Wi-Fi standard.” Back in February, Qualcomm announced the WCN3998, a 2x2 802.11ax chipset for smartphones and mobile devices, which also supports the WPA3 security protocol, whilst in January, Intel announced its intention to expand its home Wi-Fi portfolio with new 802.11ax chipsets for mainstream 2x2 and 4x4 home routers and gateways during 2018.

“It is expected that some routers, smartphones and laptops will start to get to market with 802.11ax chipsets in 2018, but there is a risk that the Wi-Fi Alliance certification process will not be in place and early devices may not be certified” Bosshard adds.

It’s worth noting that in the same way as two-way radio manufacturers have continuously added new features on top of DMR, Wi-Fi vendors are seeing 802.11ax as a foundation rather than something set in stone. For example, “Ruckus iterates over and above the standards as they move at a pace that requires consensus and then the silicon has to be created – in the meantime Wi-Fi moves at a lightning fast pace in terms of development,” Watson says.

He adds that there are eight different areas where Ruckus has added elements over and above those seen in 802.11ax. An example of these applies to high density environments such as a train station where there are a lot of transient users – many people entering and leaving the area without any intention of connecting to the Wi-Fi network. In that situation, the Wi-Fi network “would get bombarded with them – and while that would still be true with 11ax, there’s nothing in there that really prevents that.” Ruckus has a transient client capability to minimise this issue. Watson also says that multi-vendor Wi-Fi deployments are very rare and its relatively low cost compared to other technologies and the desire for rapid deployments means that he’s yet to hear any customers express any concerns around vendor lock-in.

Avoiding the spectrum crunch
No discussion of the latest wireless technology would be complete without a mention of spectrum. In February 2017, the Wi-Fi Spectrum Needs Study – which was commissioned by the Wi-Fi Alliance – indicated that the growing use of Wi-Fi devices coupled with rising data speeds and traffic volumes would mean that the amount of spectrum currently available in 5 GHz would become insufficient by 2020, with a further 500 MHz to 1 GHz required in various world regions to support the expected growth in Wi-Fi beyond that date, rising to 1.3-1.8 GHz additional spectrum by 2025, if the use of the technology exceeds expectations. It also noted that Wi-Fi spectrum needs to be “sufficiently contiguous to support a number of 160 MHz wide channels, which are required to support a growing number of bandwidth-intensive applications and to allow maximum Wi-Fi benefits to be attained.”

Bosshard says that in the UK, Ofcom made 125 MHz of additional spectrum (the 5.8 GHz band) available for Wi-Fi and removed a guard band of 20 MHz (5795 - 5815 MHz) last year. This spectrum had previously been reserved for DSRC and typically used for road tolling systems, but there was little take-up in the UK. Bosshard says that 6 GHz is also being heavily discussed in the US and continental Europe as far as Wi-Fi use is concerned. He notes that one of the advantages of spectrum at 6 GHz is that there is potentially more continuous spectrum available for Wi-Fi, which means that there’s more room to use 80 or 160 MHz channels. However, he highlights the difficulties in harmonising spectrum at the global level even though such harmonisation drive economies of scale and hence lower equipment costs.

In Europe, FM57, the project team within the Electronics Communications Committee (ECC) – a division of the European Conference of Postal and Telecommunications Administrations (CEPT), is investigating the use of Wireless Access Systems and RadioLAN at 6 GHz, as requested by a European Commission Mandate. A summary of a FM57 meeting that took place in March highlighted that “15 CEPT countries already have mobile allocation in the 6 GHz band with primary status and another CEPT country has allocation with secondary status.” The group is due to meet in October and provide a draft interim CEPT report to the European Commission the same month.

Over in the US, Ajit Pai, the chairman of the FCC said in a blog that it is planning “to move forward with a rulemaking on that [6GHz] spectrum this fall.” Back in October, a number of large tech companies, including Apple, Facebook, Google and Qualcomm, filed a report with the FCC in response to the latter’s Notice of Inquiry on Exploring Flexible Use in Mid-Band Spectrum between 3.7 GHz and 24 GHz (which was issued in July 2017). The response said they all agree that “Part 15 access to the 5925–7125 MHz band (the “6 GHz band”) is essential to meeting demand for the next generation of wireless broadband services” and called for the entire band to be opened up to unlicenced radio local access network operations.

It’s worth noting that there’s the WiGig standard operating in 60 GHz should extremely high (8 Gbps) data rates be required (see my interview with the Wi-Fi Alliance’s CEO, Edgar Figueroa in our November 2016 issue).

Wi-Fi will certainly have a role to play in the 5G era and with both technologies expected to move off the drawing board over the next few years, it’s an exciting time for everyone involved.

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