4g Engineer mobile connectivity

LTE – the 4G deployment nitty gritty – macrocells and small cells

The mobile networks are built up from thousands of base stations around the country, connected back to the operators’ core networks using a variety of backhauls. Once the media hits the core network the voice/data session is directed as appropriate.

The backhaul technology has developed over time from E1s/ATM to Ethernet (fibre) with wireless connections thrown in where necessary.

Base stations, known in the business as Macrocells, contain the transmission and battery backup equipment to support a variety of call and data handling capacities (typically up to 250 simultaneous users) dependent on location. This equipment has historically taken a lot of space – it would probably fill the average master bedroom at home, requires expert installation and, because there is a mast involved to hold antennae at some height, needs Local Authority planning permission.

Technology developments mean that this kit can now fit into a single wardrobe. This does reduce the cost but doesn’t affect the engineering and planning factors. Macrocells are not cheap and take time to deploy.

With the advent of Long Term Evolution (LTE or 4G) the business of mobile, already dynamic, is changing forever. Bandwidth usage is accelerating and customers are becoming very demanding. They want a great user experience consistent with that of the expensive phones they all now carry.

The ramp up of bandwidth usage is being caused by more people using more data. This may seem to be an obvious statement but it is relevant. More people means more mobile channels are required. More data means more bandwidth capacity. Also as mobile technology becomes capable of delivering faster data throughput the growth in usage is happening at specific hotspots. Network operators have to move quickly to meet this demand – more quickly than is consistent with the lengthy planning permission for new Macrocells.

The answer is small cells. Small cells have lower capacity than Macrocells but are deployable in visually unobtrusive form factors at first or second floor levels in a street or perhaps on a lamppost. They are low cost, plug and play so they can be installed in minutes by low skilled workers and are potentially more acceptable to Local Authority planning departments than the large visible masts of the Macrocell. Small cells can therefore solve the mobile network capacity problem by (relatively) rapidly being deployed to sites where need is greatest.

It all sounds good but the industry isn’t quite there yet. The issues are cost, interference with neighbouring small cells and the backhaul technology available to relay traffic to the core network. Also they aren’t anything like plug and play. Same old stuff really.

The small cell story is more complicated though. The 2G and 3G stories have been ones where the number of Macrocells is relatively small (the approx. 4,500 in the UK is still fairly small) and the bandwidth carried, although it is growing rapidly, is fairly low in comparison with what we can expect in the future. The limited scale of these networks means that they have been relatively straightforward to manage and the limited number of manufacturers in the game means that interoperability has been relatively simple to achieve (I know that any mobile network engineer will shoot me down in flames here but all this “simplicity” is compared to what is to come).

Small cells come in a variety of sizes and flavours depending on how much traffic you want them to carry at a specific location. There is no standard classification but you may be familiar with some of the terms: Microcell (5 – 10Watts) Picocell (100mw to 250mw indoor 1 – 5 w outdoor) and Femtocells (10 – 100mw indoor only). Classically WiFi hotspots are also small cells and WiFi offload is likely to form part of a mobile operator’s strategy in coping with network capacity demand. If traffic can be shifted onto WiFi, normally terminated onto a fixed line broadband connection it takes the strain off the mobile network.

So a network that contains small cells is likely to in reality contain a wide variety of device types requiring a variety of backhaul types and all interworking with each other, including the larger Macrocells. Known as a Heterogeneous Network this not only increases the complexity of the interoperability challenge but means many more nodes and consequently a far more complex management task. Such a network needs to be a Self Organising Network (SON) – another emerging technology concept that isn’t quite there yet.

Small cells are still in the very early stages of development and testing in Europe and the rest of the world. They are, if you like, at the 1.0 stage. To be ready for mass deployment they need to move on to 2.0.  It is estimated that for every Macrocell you need 10 small cells – far higher numbers to manage.

You will have read of my experience with the O2 LTE trials – based on 25 Macrocells in London. Here in the UK we are late with our LTE 4G deployment so whilst the small cell technology is not ready yet for mass deployment we aren’t ready for it yet. Perhaps that is a “bit of luck” that we can put to our advantage.

There are some interesting LTE experiences to note from other countries. In Germany for example the regulator has insisted that the technology be rolled out to service rural notspots before hitting more densely populated metropolitan areas. Because LTE in this case is being used largely as a fixed broadband replacement service the bandwidth demand has reflected that of fixed line broadband. The average mobile broadband seen in these areas is roughly the same or slightly greater than UK average fixed broadband speeds (13 – 15Mbps) and the monthly data usage is similar It’s worth noting that one year after Vodafone’s LTE network launch in Germany the LTE data traffic volume is higher than UMTS traffic volume seen during during the first six years.

These German rural rollouts use Macrocells, 3,000 of them. As they move into the cities in Germany small cells will be needed, not just to add capacity (Macrocell sites are difficult to come by) but also to serve indoor areas – LTE ain’t good on in-building penetration.

We are in for interesting times ahead. They should be good times for the equipment vendor community but also for us users who will be able to take advantage of the higher speeds that LTE will bring. The network operator community is going to have challenges. Bandwidth use is forecast to double every year for the next five years whilst average revenues per user is expected to remain flat at best. That particular discussion is for another blog post.

That’s all folks…

Trefor Davies

By Trefor Davies

Liver of life, father of four, CTO of, writer, poet,

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