Will cognitive radio, dynamic spectrum access come of age in 5G?

Around 10 years ago, the Defense Advanced Research Projects Agency (DARPA)’s Next Generation Communications program constructed a prototype cognitive radio system, which utilized dynamic spectrum access for its communications. By identifying unused sections of spectrum in the area it was operating, it was hoped up to 10-times more spectrum would be available for transmissions. This highlighted a growing interest in the defense community in dynamic spectrum access techniques which had been developed with the challenges of battle-space spectrum in mind, but also apparently had applicability in commercial environments in terms of making more efficient use of valuable spectrum resources and potentially leading the way to spectrum trading. The XG program was one of the largest cognitive radio projects at the time but interest in Cognitive radio was by no means limited to the U.S.

Martin Cave’s audit of public sector bands in 2005, which highlighted just how much more efficiently U.K. defense spectrum could be utilized, provoked interest in the topic in the U.K. This was produced alongside Ofcom’s Spectrum Framework Review, which set out ambitious targets for a general move from the traditional “command and control” approach to spectrum licensing to a more dynamic approach based on “market mechanisms” with the overall ambition of realizing better value from spectrum for the U.K.

With the switchover to digital television and release of TV white space, a debate was ignited over whether DSA could be applied to these civilian bands too. The obvious example of this has been the activity around TV white space, although the Federal Communications Commission discussion on 3.5 GHz is also significant.

However, the digital TV switchover was six years ago and the commercial roll out of white space devices is still fairly limited due to the complications of deploying these devices in practice. Concerns over the so-called “hidden node” issue (interference provoked by the failure of one device to detect the presence of all other devices) and how devices with different spectral views would liaise with each other have meant that the regulation of these white space devices has taken some time to agree.

In attempting to overcome these limitations, regulators gradually shied away from a pure spectrum sensing approach, towards the introduction of beacon signals to identify usage, before settling on the use of a centralized database of white spaces in each location that is used in addition to spectrum sensing.

But even then, the practical use of TV white spaces has continued to be fairly limited. Vendors and operators have struggled to find an application that suits the availability of white spaces, as well as handling the lack of guaranteed spectrum.

This same philosophy is being proposed for 3.5 GHz in the U.S., where some locations have other users (e.g. marine radar), but the combination of database and sensing could allow this band to be used. This is especially important as 3.5 GHz is one of the few LTE bands that is supported globally, so there is a clear commercial imperative.

Enter 5G

At the recent 5G Huddle, rethinking how existing technologies make use of spectrum was a key topic of discussion, with spectrum sharing a major part of this.

There are some strong arguments for why this would be sensible:

  • We’re starting to reach the limits of what we can achieve through higher order modulation schemes, with any gains insufficient to keep pace with demand.
  • We may still be making some gains with regards to multiple-input, multiple-output and CoMP, but again, not at the same rate that demand is increasing.
  • Small cells, which are increasing in usage, and network densification, levels of which are also increasing, both lend themselves well to spectrum sharing.
  • –he last variable available to us in our attempts to increase capacity is spectrum, and (at least in theory), DSA maximizes availability and efficiency of spectrum across all operators

On that last point, this is of course only if it is deployed correctly, with polite protocols for communications.

However introducing dynamic spectrum sharing to “5G” would surely result in 5G just suffering from the same technical issues that cognitive radio has encountered before.

After all, one of the key differentiators of cellular over many other wireless technologies, such as Wi-Fi, is the guaranteed quality of service. Indeed, we have previously examined how exclusively licensed spectrum loses value as the sharing arrangements increase uncertainty for operators.

Wouldn’t 5G lose this edge if spectrum access became dynamic and without guarantees?

At present, you would be correct, but it is unlikely anyone would be satisfied introducing such a glaring problem into 5G. Rather the key difference between earlier cognitive radios and 5G is that, as demonstrated with the discussions at the 5G huddle, major commercial vendors and operators are putting significant research time and investment behind the technology.

Perhaps this time around, with the full weight of the industry behind it, and with an appropriate understanding of what operators need from spectrum sharing conditions to offer high-quality services, cognitive radio and DSA can really come of age.

This blog post originally appeared as part of RCR Wireless’s Analyst Angle, where the industry’s leading analysts discuss the hot topics in the wireless industry.

The UK needs to address rural coverage – but national roaming isn’t the answer

This week has seen the UK government bring back proposals for national roaming, the idea being that those in remote villages and towns should be able to jump onto rival networks if their current provider isn’t delivering. It’s certainly an admirable initiative and one worthy of discussion – but national roaming isn’t the answer.

There has been plenty of discussion today on the pros and cons of this approach, with The Register doing a particularly good job of summarising the key reasons why this policy is well intentioned but not well thought through.

So rather than going over the same ground, we wanted to look at other potential, viable solutions to the problem.

LTE is coming

As part of the 4G licence award, Telefónica O2 has an obligation to provide “a mobile broadband service for indoor reception to at least 98% of the UK population and at least 95% of the population of each of the UK nations… by the end of 2017 at the latest.” And, perhaps encouraged by this obligation, all the operators have committed to meeting this target by the end of 2015. So much will change in the next year without further government intervention.

While LTE has been in big cities for a while now, it’s yet to reach much of the countryside or the smaller towns. But it’s on the way.

Real Wireless completed a project for the Scottish Government where we looked specifically at rural coverage and people will be genuinely surprised by just how good LTE coverage is.

We found that providing 95% of the population with indoor coverage, growing to 98% with gradual enhancements, is not beyond the reach of operators to achieve by the end of 2015. This is a huge improvement over 2G coverage, which even today only currently averages around 85% indoors. We also found that the average indoor mobile data speed available across Scotland will increase from about 2.5Mbps in 2012 to approximately 36Mbps by 2023.

The 4G roll-outs will reach 95% of the population surprisingly quickly, and there are ways to accelerate the rollout to 98%. However, it’s the final 2% that presents the most difficult challenge – but nor is this something national roaming would solve.

Rural coverage is expensive

Building networks is expensive, yet the UK already has amongst the lowest mobile infrastructure investment per head – something we touched on in a previous blog here. This is a real problem and one that puts us behind the rest of the world.

Technology has developed so that operators no longer need to invest in coverage over a wide area, to get service where users need it most – indoors. Vodafone’s open sure signal initiative is a good example of how this can work.

Targeted coverage makes it much more cost effective for operators to deploy sites and also avoids many of the planning challenges that can slow up installations. It’s this sort of technology that needs to be considered when addressing that final 2% figure, rather than expecting a blanket coverage approach. Such technology also provides operators with a way to continue to compete on coverage even as the share more of their wider networks, which is surely in the interest of consumers.

No easy answers

Rural coverage isn’t easy and the challenge has always been balancing the cost of network investment with the potential return. However with the wider rollout of LTE and the development of much cheaper, targeted ways of delivering coverage, there are viable solutions that need to be considered. It’s these approaches that need to be looked at by Government and operators in parallel, rather than pushing ahead with an approach that, while well intentioned, has some significant flaws.   Government needs to be aware of the risks of unintended consequences – just one example is the potential impact on national security flagged by police chiefs and the Home Secretary.

Wireless in Stadiums

The Challenge & Opportunities of Stadium Wireless

 We presented on this at a conference in Barcelona last week.

 Stadiums are famously some of the most challenging environments for wireless, but do offer a lot of opportunities for improving customer satisfaction, new revenue streams and operational efficiency.

 The presentation covers the challenges faced by stadium owners in meeting increasing demand for wireless but without sacrificing on the core values of their loyal supporters.

 But stadiums do have some specific technical difficulties compared with other wireless environments, including

o   Multiple user communities

o   Challenging architecture

o   Critical business requirements

o   Hig capacity density

o   A mixed propagation environment

 Getting the best from wireless in stadiums involves recognising and addressing all of these challenges and is likely to lead to a multi-party engagement model with appropriate independent wireless expertise  but whilst difficult it is definitely possible.

It also highlights some of the current challenges: such as the difficulty of getting cost effective Wi-Fi into a stadium bowl without producing a disappointing experience. And the current opportunities: such as using LTE Broadcast for a high quality video streaming and as a new source of content revenue.

The presentation is available in our downloads library.

These issues are discussed in more detail in a Stadium Magazine interview with RW Commercial Director Mark Keenan.

In addition, we discussed many of the commercial aspects in our White Paper.