Will 5G be for a minority of high capacity hill dwellers or for the rest of us?

Will 5G be for a minority of high capacity hill dwellers or for the rest of us?

The “single frequency” networks we use today have changed the landscape of mobile coverage – literally! If one stands in any place and plots the total day-time mobile data capacity available as a height above the ground – the resulting national contour map looks like the hills of Yunnan Province in Southern China. The capacity peaks are where the radio towers are and the valley floor is where the radio interference from the next tower decimates the capacity. Roughly 25% of the population live on the peaks and upper slopes of these capacity hills and 75% of the population live on the lower slopes and valley floor. (These are ball-park numbers from simple geometry). Three sorts of mobile technology developments over the past 20 years have been making this capacity disparity a whole lot worse.

The first has been the direction of radio system technology advances. They have focused solely on making the hills ever higher but doing relatively little about the valleys. The aim has been to show consumers at least the possibility of every higher down-load speeds. It began with the 3G technology followed by HSPA and now LTE (or 4G).  A number of research programmes under the LTE advanced and 5G umbrellas offer spectacular advances in down-load speeds but the benefits of these breakthroughs are likely to be mainly limited to the 25% of high capacity hill dwellers and little or nothing for all those in the valleys.

The second trend towards ever higher capacity hills is being driven by the spectrum regulators. They are doing their best to find more spectrum to meet the rising consumer demand for wireless data. Setting to one side the recently released digital dividend spectrum at 800 MHz (as it only amounts to 20% of the current mobile spectrum), the general rule has been to look ever higher in the radio spectrum to find the extra bandwidth. We have moved over time from the original 900 MHz cellular spectrum to 1800 MHz, then 2.1 GHz (for 3G), then to 2.6 GHz (for 4G), some 3.4 GHz spectrum is soon to be auctioned and even spectrum above 20 GHz is under discussion. As we move higher in the radio spectrum the range of transmission gets shorter. This leads to ever more capacity being packed onto the hills and contributing nothing directly to the valley floors. Carrier aggregation allows some secondary relief but it does not solve the huge drop in cell-edge capacity from whichever carrier is serving the valley floors.

The third trend is the collapse of mobile handset performance as an ever greater number of frequency bands are brought into use for mobile radio. An antenna optimised to work over widely separated frequency bands always has a worse performance than one optimised for a specific frequency band. But the smartphone story gets worse. Antenna arrangements packed into the tiny volume of a smartphone has become a nightmare for radio engineers. The impact of the deteriorating receiver performance of wireless devices is to suck extra capacity out of the mobile networks to compensate. This loss will hardly be noticed on the hills and upper slopes. For the lower slopes and valley the impact is to make a bad situation worse. The level of the valley floor is gradually sinking.

This brings me back to the lead question – will 5G continue the trend of making the capacity hills ever higher with no advance for the 75% of the population on the lower slopes and valleys?  The temptations are there. Mobile down-load speeds of 1 Gb/s or more are guaranteed to grab the headlines. It provides marketing departments with superlatives to sell devices and services. But lost in all the hullabaloo will be the fact that the geographic reach of these incredible speeds may have shrunk, in the extreme, to little more than flag poles on top of the hills.  A new wireless access service that only reached 25% of the population would be killing “the mobility story” that has allowed mobile operators to charge a premium price for the sheer convenience of consumers being able to do what they want without having to worry about where they were. In political terms a brand new opportunity that would never reach 75% of voters looks like the “kiss of death” in terms of the endorsement of governments for national broadband infrastructures.  It may be in the human spirit to take research to the very extremes of what is possible but this does not automatically translate into a commercially sensible “next big leap” for wireless communications.

The debate has started on what 5G should be. Some vendors are already pushing the “ever faster” down-load story. Others say the attention needs to be on a more balanced package of wireless broadband network benefits and not just focus on the radio air-interface. The word “package” is where the ideal solution is likely to be found. We can see this from recent history. The world’s most successful mobile technology revolution (GSM) was not just about data down-load speeds or even the radio air-interface. It was also about global mobility supported by a new intelligent network platform. It was about a huge leap in security. It was about a handset cost revolution only made possible with the digital technology.  GSM was the “marketing wrapper” around this package of huge commercial benefits.

The magnet of a global “5G marketing wrapper” can be important in bringing different interests together to compromise and reach international agreement on standards. This has to be the approach the world takes for 5G. There should be a place for much higher mobile down-load speeds but it cannot be allowed to take more than 20% of the 5G story-line. Also within the 5G marketing wrapper has to be advancing the DAN (Demand Attentive Network) agenda to significantly improve mobile radio economics and responsiveness, a leap forward in signalling efficiency (eg MAC Lite), air-interface latencies of less than 100μs, much more energy efficient networks and a place for the Internet of Things.  We need to talk of a new 5G network and resist taking a road that will take “the mobility” out of mobile radio. It is this other 80% of the story-line that can take global wireless communications to the next level of commercial success beyond 2020.

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