The telecoms industry is increasingly becoming a victim of its own success, promising mesmerising feats of connectivity that are simply not possible, today. With 5G, the industry has outlined its vision for a transformation in wireless, and the far-reaching implications it will have on the society around us.
But, peeking behind the curtains, it becomes immediately apparent that these promised breakthroughs are not without their own set of drawbacks. In an idyllic world, there are unlimited resources, from ample time to endless supplies of money. We don’t live in that world, and that’s not the world that 5G will be deployed in.
Instead, we live in a world of physical obstructions, where mountains reach for the skies and cities sit in valleys. Our world is bound by the limits of physics which, in turn, dictate just how much information we can squeeze into bands of radio spectrum. Those bands, and specifically, the ones being touted to provide gigabit-class capacity, demand a cosmic level of investment.
And with the pace of technological advancement accelerating, should we swallow the cost of something that will, ultimately, be replaced with a superior alternative?
An Insight into Fixed Wireless Access
Utilising radio spectrum to deliver broadband is not a new idea, in fact, it’s a compelling technique which predates even the most primitive 4G LTE networks at the turn of the decade. In the time since its initial conception, wireless technology has evolved from being an energy-sipper to a fundamental feature of modern connected devices. Most importantly, however, this technology has changed how we use our devices, from enabling the app-economy to initiating the streaming age.
And it is our usage of these services that is empowering innovators and inventors to pave the next steps in this journey. Provisioning high-speed broadband through the air has a lot going for it. Rather than just reminding us of the era we live in, this method of connectivity brings with it several key advantages. These advantages should help people to understand that Fixed Wireless Access (FWA) is not a competitor to fibre because the two solutions are radically different, and the latter will remain superior in virtually every aspect, where it can be deployed.
The most clear-cut advantage of FWA is cost-effectiveness, with its deployment and operation requiring minimal resources compared to fibre densification at the edge of networks. In regions where the topography prohibits fibre deployment, and where sparse population distribution means a Return on Investment (ROI) is not possible, FWA is the only logical method of connectivity. If we look at developing countries, where there may be a unilateral absence of fixed infrastructure, the initial investment requirements for self-built fibre are simply stunning.
Crucially, FWA cuts out the ‘last mile’ of FTTx, which sees fibre being placed in underground ducts or strung along poles above the ground. This process is incredibly CapEx intensive and time-consuming, requiring footpaths and road surfaces to be opened for the installation of ducting, and involving multiple different stakeholders during the network design stages. Moreover, don’t forget the long term operational expenses that are generated by requirements for maintenance work. Some studies conclude that the costs associated with extending fibre at the edge and delivering it directly to homes and businesses account for over 90% of the total cost of these networks.
Breaking down the infrastructure cost model of FWA, there are three pillars. The most obvious of these is the radio spectrum that is required to transmit information wirelessly. Currently, licensed spectrum is the dominant means of connectivity because of its resilience. In Ireland, this spectrum is regulated by ComReg, who allocates it to bidders in proportion to how much they are willing to pay for different bands when they go to go auction. The licenses for spectrum usually reach over a decade before expiration, and they require an up-front sum and usage fees made payable to the regulator during the license period.
Secondly, FWA providers must consider the cost of equipment at the 5G base station or small cell (gNB). This is the edge of the network, acting as the closest link between the provider and end users. Ground equipment at these nodes includes everything from BBUs to generators, while the physical structure carries the antennas and RRUs. With macrosites, in particular, there is a substantial cost involved with leasing land and electricity usage.
The remaining costs lie within the transport and core networks which connect the edge nodes to the Internet. High-capacity macrosites require FTTA, and this can be facilitated by renting strands of dark fibre from wholesale networks and connecting with the gNB. In cases where fibre does not exist, self-built fibre or microwave are the only options. The former is an expensive solution as outlined earlier, but provides unparalleled, scalable capacity. The latter approach is less expensive, however, its availability and peak capacity pails in comparison to fibre, and there are spectrum license fees to consider.
Another benefit of FWA is the fact that it is a proven and well-defined business case for provisioning broadband, at least with the utilisation of spectrum such as 800MHz, 1800MHz and 2100MHz. The Return on Investment is materially higher in the short term than it it is with fixed access networks given the more palatable upfront and operational costs. This also means that low adoption of FWA is less detrimental to the business case than it is with FTTH, a solution that requires a high take-up rate over the long-term to warrant its existence.
Bundling FWA packages with mobile plans is not a new tactic employed by telecoms companies because it has been proven to significantly increase customer retention and thereby reduce churn. The same form of “stickiness” is more difficult to achieve with dual or triple-play packages that include fixed broadband as it is inherently more expensive, reducing wiggle-room for discounting.
Perhaps the most noteworthy strong-point of FWA from a business case perspective is the liberation that it offers to market entrants. Deploying fixed infrastructure where incumbent providers are present usually does not make sense, and this thwarts competition from new providers. The same restrictions don’t apply to FWA because the cost of the last mile is eradicated, meaning much of the transport network can be rented from third-party companies at a reasonable cost. In this way, we can find greater competition in FWA markets, pushing down prices for consumers and encouraging innovation from operators.
In terms of the use cases applying to FWA, they mirror those enabled by fixed networks, provided metrics such as bandwidth, jitter, latency and packet loss are similar. Previously, this would be impossible, but given the implementation of techniques such as beamforming and Massive MIMO with spectrum in mid and high-bands, it can now become a reality.
As a result, new use cases such as dual-connectivity can be devised. This would see businesses maintaining both a fixed and wireless connection at their premise to ensure the highest possible level of redundancy and up-time. Furthermore, dual-connectivity is increasingly being utilised as a means to maximise the level of throughput available to a business by aggregating the capacity of FWA with that of fixed connections. This is particularly advantageous for businesses that rely on copper for the last mile (FTTC), or for those that need to segment their traffic across different transport networks.
For short-term connections, such as those required during events and festivals, FWA is the only viable method of connectivity in most cases. This is reinforced by the fact that the majority of outdoor festivals take place in the fringe of urban areas, where fixed networks may be non-existent. Also, think of the applicability of FWA for holidaymakers and seasonal influxes of tourists.
Of course, next-generation FWA solutions must be designed to cater for every type of traffic, from supporting an exploding number of IoT devices to connecting mission-critical machines which require an extremely low and consistent level of latency. Again, much of this will be made possible by the utilisation of high-frequency spectrum, and network densification.
Massive MIMO transforms sub-6GHz 5G NR
Spectrum in the sub-6GHz range will support pioneering 5G NR deployments, both from a mobile and FWA perspective. This is spectrum that can offer vastly enhanced capacity compared to today’s low-band networks, and the opportunity to aggregate it with existing 4G carriers only serves to amplify the benefits. Furthermore, the introduction of features such as Massive MIMO, 256 QAM and utilisation of unlicensed spectrum makes sub-6GHz 5G NR a meaningful generational leap over today’s 4G networks.
It will be spectrum in the 3.6GHz band that will enable the deployment of 5G NR for FWA in urban, suburban and rural areas over the coming years. Hitting the sweet spot as mid-band spectrum, 3.6GHz offers additional capacity over today’s 800, 1800, 2100 and 2600MHz 4G bands, while boasting better signal propagation than high-bands.
However, acting as a middle-ground spectrum, there is less clarity as to the applicability of 3.6GHz for FWA. In urban areas, the capacity that it providers will not be sufficient for long-term demand, or for an extremely high density of connections per cell as projected will occur. And with the reality that fixed infrastructure is pervasive in developed urban regions, why choose a network with a limited lifespan?
The opposite applies in rural areas, where the demand for capacity is to a lesser degree but other factors such as topography and population distribution become an issue. Breaking it down, for FWA providers to target a high number of rural subscribers, there needs to be a high level of geographic coverage. Needless to say, the 3.6GHz band is not suitable for reaching coverage goals because it requires a high density of macrosites, on a level that is vastly more intense than it is with low-band (700 and 800MHz) networks serving rural areas today.
However, despite these limitations, there is one region which perfectly fits the capacity and coverage characteristics of 3.6GHz. It’s suburban premises, the bridging point between urban and rural, both in terms of connectivity and population density. Here, deployment of the 3.6GHz band can offer enterprise and residential high-speed broadband at a competitive price.
With a dense and large portfolio of multi-band macrosites to deploy this spectrum atop, the rollout can be a swift process arousing very minimal disruption. Combine this with the fact that there is usually the presence of dark fibre networks in suburban regions, and it is clear that these elements align perfectly for such a rollout. Also, don’t forget that sub-6GHz spectrum can be deployed standalone or non-standalone, introducing a new level of versatility.
The growing proportion of traffic offloaded to fixed networks at the edge means the capacity of this band will be ample for quite some time, after which it can be superseded by mmWave spectrum and the maturing ecosystem of equipment that it will support. Additionally, the profile of suburban premises is such that achieving a high adoption rate per cell is easier than it is in sparsely populated rural areas.
It is also notable that the vast majority of suburban developments are located on lowland, with the occurrence of natural features such as hills being a rarity. This is a friendly environment for signal propagation, with the only barriers existing being man-made ones, most of which can be mitigated with the installation of an externally-mounted low or medium gain antenna.
Despite the density of cells, achieving indoor coverage with the 3.6GHz band will become a challenge and one that will ultimately shape the design of our networks. Here enters Massive MIMO, a truly transformational breakthrough for mobile consumers and providers alike. This technology employs dozens, and eventually hundreds, of antennas to enhance the capacity of mid and high-bands such as 3.6GHz.
Crucially, Massive MIMO improves the reliability of wireless links, resulting in major signal quality increases at the cell edge and deep within buildings. In fact, the impact of implementing Massive MIMO in the 3.5-3.6GHz band is so tremendously profound that a study conducted by Nokia determined this combination provided better coverage than 1800MHz 4G utilising 2x2MIMO. Ericsson has voiced a similar stance on this and expects deployments of the band atop existing 4G site grids will provide a coverage footprint comparable to 2100MHz networks operating today.
Without exception, this is a remarkable breakthrough for the industry, significantly reducing the cost and complexities that would dog mobile providers in the event of a requirement to carry out heavy densification of their networks for sub-6GHz spectrum. Other features such as downlink/uplink decoupling will have an equally positive effect on the performance of the 3.6GHz band and sub-6GHz spectrum, affording huge advantages to the FWA providers.
MmWave FWA is a Distant Dream
MmWave spectrum has been hyped to an anticlimax thus far, with claims about its phenomenal characteristics crashing back to reality as soon as the word deployment is mentioned. That’s because the tiny distances between the peaks and valleys within the spectrum make propagation an incredibly difficult endeavour, requiring new triumphs in radio design to mitigate signal attenuation.
Everything around us is a barrier for mmWave spectrum, and fundamentally, every additional obstruction increases the cost of deployment exponentially, to a level that is just not viable. The atmosphere above our heads, the trees flanking our streets and even the windows that allow us to gaze at the outside world act as barriers to the penetration of mmWave signals. For an insight, some estimates put the rate of signal loss with mmWave spectrum in the presence of intense rain (50mm/hour) at 18.4dB per km.
To understand why the industry is pushing forth mmWave spectrum, and why it is acutely relevant to FWA, we need to examine the set of benefits that it introduces. The most prominent of those is a quantum leap in the amount of spectral bandwidth available, to such an extent that spectrum in bands such as 70GHz accounts for more bandwidth than that of all other licensed bands combined. Think about that for a second, it is stupefying.
This extreme capacity allows for the creation of wireless links that exceed 10Gbps, a testament to the bright future of wireless. Scalability is also a core feature of mmWave, allowing mobile providers to bolster the capacity of links as demand increases with more efficient modulation schemes.
Furthermore, the narrow beams cast by mmWave sites, especially with beamforming, can act as an advantage compared to lower frequencies which provide a large footprint, limiting the number of links that can be broadcast in a specific geographical area because of signal interference. With the ability to deploy many mmWave links in close proximity to one another, this feature only serves to amplify the scalability potential. For example, the beamwidth of a 70GHz link is four times as narrow as that of an 18GHz link, delivering up to sixteen times the density of E-Band links.
These breakthrough features, however, are overshadowed by the aforementioned signal attenuation traits of mmWave spectrum. To tackle that, the industry is working feverishly to develop new techniques which reduce the rate of signal loss, and as a direct consequence, to make mmWave a viable strategy for FWA services. Those techniques include beam steering and beam tracking, both of which will play a fundamental role in maintaining mmWave links in challenging signal conditions.
A key facet of mmWave for FWA will be the miniaturisation of transceivers, allowing for the deployment of an unprecedented number of small cells. Unsurprisingly, the stunning volume of small cells required will push down the cost per unit over time, allowing us to enhance the density of networks without incurring CapEx or OpEx increases over the lifespan of this technology. Looking specifically at FWA, this is important because it paves the way for a more rapid ROI and makes the business case more attractive for non-incumbents.
Referring to the availability characteristics of mmWave spectrum, it is paramount to consider the atmospheric conditions in which links operate. As with every band of spectrum, the probability of events such as rainfall occurring on a region-by-region basis will dictate the availability percentage, or the average percentage of the time the link is predicted to operate according to its specification. Obviously, the signal attenuation incurred by mmWave spectrum is greater than that with access spectrum utilised in the past, reducing the availability ratings in many places.
FWA providers operating services within mmWave spectrum will be required to analyse data portraying predicted rain rates in different geographical locations to offer an availability rating to customers. For reference, the International Telecoms Union (ITU) develops detailed rainfall models to address the above requirement. Factors such as the hop distance, transmit power, receive sensitivity, and beam divergence will impact the availability rating and the ability of the band to overcome events such as intense rainfall without failure.
Notwithstanding the limitations of mmWave spectrum and the immature ecosystem that it encapsulates, the largest barrier thwarting its adoption for FWA is the spectrum landscape in the European Union, one that is lagging behind our peers. Spectrum harmonisation efforts on the continent provide major benefits to consumers and providers, however, these same efforts also slow down the process of repurposing bands on a regional basis, hindering the shift to mmWave 5G NR.
The pioneering mmWave band in Europe is 26GHz (24.25-27.5 GHz), with first-stage FWA providers poised to take advantage of the capacity characteristics introduced with the spectrum. Ubiquitous prevalence of microwave links in this band means mobile providers will need to shift their transport networks to spectrum in higher bands such as 32GHz and the E-Band. This will be a lengthy process, and heavy dependence on microwave backhaul in many European countries will be an issue for mobile providers seeking a swift transition to access use in the 26GHz band.
Later down the road, we will see the implementation of spectrum in the 40.5-43.5 GHz and 66-71 GHz for mmWave access use. These are ultra-high capacity bands that can be leveraged standalone or aggregated with alternative spectrum to improve signal quality at the cell edge, and to meet the evolving traffic demands of residential and businesses subscribers.
Ultimately, however, there will need to be sweeping changes in the technology at our disposal if any of the above bands are to be deemed commercially viable for large-scale FWA deployments. And, please, don’t scoff at the ability of the telecoms industry to deliver innovation. Just several years ago, provisioning speeds above 10Mbps wirelessly would be considered mind-blowing. Today, we are plotting to push past the 1Gbps milestone and to achieve latency-free wireless connectivity. If that doesn’t excite you, imagine the cloud computing and traffic slicing applications that will be possible.
Transport Networks for FWA in the 5G Era
Transport networks perform a fundamental function in the delivery of broadband, fixed or wireless. And while many FWA providers love to boast that their network is not tied down by fibre, in reality, they are underpinned by it. This is because no microwave solution to date offers the same level of no-compromise performance that fibre exhibits. In every key metric – availability, capacity, latency and packet loss – fibre excels.
These advantages cannot be overlooked in the 5G era, an imminent future in which gigabit-class wireless networks require serious backbone capacity to avoid a slowdown. Aiding this transition to fixed networks is the increasing penetration of dark fibre services in urban, suburban and rural areas. This open access infrastructure reduces the TCO, removing market entry barriers for smaller FWA providers. As such, fibre will be the spine of wireless networks in the coming decade.
Low-band microwave solutions (6–13GHz) of yesteryear just don’t cut the mustard for FWA networks anymore, even in the sparsely populated rural locations that they are typically deployed in. These solutions were attractive in the past and will remain relevant in some extremely remote regions, because of their excellent availability metrics, cost-effectiveness and hop distances. For example, low-band links can span beyond 10km and provide capacity of up to 2Gbps.
As I alluded to earlier, 32GHz will become the preferred mid-band for microwave backhaul, especially considering 26 and 28GHz will be repurposed for access use. Delivering capacity of up to 4Gbps, this band assumes the role of an interim transport solution for high-capacity FWA networks. Sub-6GHz macrosites will require a cost-effective but performant microwave band and 32GHz ticks both of those boxes. We will witness greater deployment of the 32GHz band in peripheral regions to link macrosites that serve large areas, resulting in a huge QoS uplift there.
Transitioning microwave links to higher bands will be an important strategy to support 5G NR access networks, with 42GHz (40.5–43.5GHz) and 66–71GHz being earmarked for this precise application in Europe. However, the real magic of next-generation microwave backhaul is realised within the E-Band, where peak capacity reaches 10Gbps when deployed standalone and 11Gbps when deployed non-standalone.
Put simply, the E-Band (71–76GHz paired with 81–86GHz) will become the dominant microwave solution moving forward, acting as a resilient alternative to fibre in locations where the density of fixed networks is insufficient to meet demand. Links utilising this spectrum can exceed 3km in distance, with hops above 5km possible when aggregation with mid-bands (15–23GHz) is introduced.
The E-Band will act as a catalyst for advancement in the space of multi-carrier backhaul links, creating higher capacity links that enhance availability. All of this progress will be important to address the digital divide in rural regions, a topic which is often forgotten amidst the mmmWave 5G hype. Microwave solutions will remain more cost-friendly than self-built or dark fibre, and therefore, they will be a pivotal tool to enable high-capacity FWA networks in the sub-6GHz and mmWave 5G NR age.
Pushing forth an immature ecosystem
Something fundamental that has been forgotten in the race to 5G is the ecosystem of devices that must be in place to allow consumer adoption of next-generation networks. The nature of FWA devices is unique in that their nomadic state reduces the signal degradation challenges that are introduced with movement. This, along with the more flexible space limitations, means that we will see comprehensive support for a myriad of sub-6GHz bands in Customer Premises Equipment (CPE) such as routers very soon.
Smartphone manufacturers are at an inflection point in terms of design because the multi-mode modems and antennas required to support sub-6GHz and mmWave spectrum require additional internal space. This is space that is simply not available, and it won’t magically appear. Until further miniaturisation, the design decisions that facilitate support for modems in our smartphones will sacrifice other key parameters such as battery capacity. This draws a striking comparison to the early days of 4G, when the first devices to feature support for the technology traded practicality for wireless performance.
That said, defying the odds, Qualcomm has managed to partner itself with an incredible number of manufacturers to enable the development of smartphones which can achieve multi-gigabit throughput in sub-6GHz spectrum. Stalwart companies including LG, OnePlus, Samsung and Xiaomi have announced their intentions to launch 5G-capable devices from May of this year, a momentous breakthrough for the industry. The chipmaker’s X50 modem leverages non-standalone 5G NR and 4×4 MIMO to deliver a dramatic uplift in both downlink and uplink performance.
This forthcoming advancement in the smartphone market is relevant to FWA because it will touch everything around it, from CPE to Industrial IoT devices. Qualcomm’s pioneering 5G modem mentioned above will find its way into dedicated FWA devices over the coming months, with companies such as Netgear already teasing their products. What’s more, the successor to the X50 modem has already been revealed by Qualcomm, and it’s FDD and spectrum sharing features will shape a more comprehensive transition to 5G NR next year.
As detailed, CPE is not bound by the same design principles as smartphones or other connected devices, and this is of huge benefit to FWA providers. With residential wireless routers, there is limitless flexibility in terms of internal space and material. Possibly the biggest liberator, however, is the dependence on mains power, negating the need for expensive and large batteries.
Looking specifically at CPE enabling FWA in sub-6GHz spectrum, a flurry of new devices are inbound. Huawei has launched its 5G CPE Pro, a pioneering residential router capable of achieving a peak downlink speed of 3.6Gbps in sub-6GHz spectrum. The company’s Balong 5000 multi-mode modem is found inside this router, and support for standalone and non-standalone 5G (Dual-Link) is a world-first.
Given the fact that indoor signal quality with sub-6GHz spectrum such as the 3.6GHz band will not differ wildly from that of existing 4G networks in 1800, 2100 and 2600MHz bands thanks to Massive MIMO, internally-positioned CPE is viable for FWA. However, that viability hinges on the density of the site grid, meaning FWA providers who operate a large number of macrosites in a smaller value of area will benefit massively in terms of indoor penetration.
Those who have relied upon low-band deployment in the past and, hence, boast a poor site grid will struggle to maintain the link between indoor CPE and external macrosites. As such, for these FWA providers, offering services to consumers will only be possible via the medium of externally-mounted antennas. The same will be true for mmWave spectrum.
For indoor routers to maintain a link with macrosites in challenging signal conditions, the output power (55+dBm) required would be extraordinary, and above the legal limits. This is why many FWA providers will need to choose the outdoor antenna approach, where the output power (40dBm) required to maintain a link is reduced as a result of the removal of physical barriers such as walls and windows.
A Demonstration of Wireless Prowess
In every essence of the technology, 5G is a demonstration of wireless prowess, culminating decades of advancement in how we utilise radio spectrum to transmit information. Fixed-Wireless-Access leverages this technology spectacularly, enabling the delivery of high-speed broadband in areas that are not addressable with fixed fibre solutions today. This is a fundamentally different form of wireless broadband than that offered in the past, designed to meet the demands of consumers and businesses for years to come.
FWA in the 5G era should deliver gigabit-throughput and rock-bottom latency, all at a fraction of the cost of fixed access infrastructure. To achieve this, our transport networks will need to be transformed, implementing fibre where possible and high-capacity microwave spectrum such as the E-Band elsewhere. At the edge, spectrum in the sub-6GHz range will provide a path to first-stage deployment of 5G NR services, without inducing major CapEx requirements atop providers. This liberates market entry restrictions, and with Massive MIMO, increasing the site grid to ensure indoor coverage is optimal may not be as urgent as we initially thought.
But, the gold-standard, future-proof form of FWA is only attainable with the use of mmWave spectrum, where an unprecedented level of capacity introduces new possibilities for consumers and providers. We won’t witness the dawn of FWA services operating in this spectrum anytime soon, after all, the signal attenuation challenges still need to be mitigated with further development and innovation. However, shunning FWA in light of these hurdles would be a mistake because it will work to reduce the digital divide.