How to build a mobile network that actually works

As odious as it is to start another article by mentioning the iPhone, it's there we need to begin. People have essayed at length on the effects the Apple phone has had on the handset market but there's been just as an important by-product issue that's arisen at the same time.

With everyone rushing to O2 in the UK and AT&T in the States for contracts when the iPhone was an exclusive, there began to growl low grumblings about the quality of service that these networks were providing. The grumblings grew to whingings and the whingings to some fairly direct internet spleen venting which has only disappeared since the likes of Orange and Vodafone have offered an alternative.

Now whether or not these networks were particularly at fault, whether they were victims of their own success or whether the iPhone itself has antenna problems is another issue but the fact is that it's the first time since the mobile telephony took off that mass focus has switched back to call quality. So, then what are the key elements that make a mobile network perform properly and why is it that some operators are just better than others? If you're ready and sitting comfortably, then we'll tell you how it works.

 

The Core Network

At the heart of all the mobile operators sits the core network. It's a series of networked computer switches that have taken over the roll of the old school scenario of a women with thick rimmed glasses and her hair tied up circa 1920 plugging leads in and out of a board. Each switch has a number of set cell towers associated with it and when a call comes through, it's job is to route that call through to the right switch which is associated with the tower that happens to be nearest the person the caller is trying to get hold of. It does this by passing the call through the network from switch to switch using the shortest possible route.

In order to do this, the core network needs to know where all the numbers are at any one time so that it knows to go to the right switch to route the call correctly, so part of the job is to keep track of your mobile phone, and therefore you, wherever you go. Every time you move from the range of one cell tower to another, there are signals sent back and forth to make sure that the core knows where to find you. Another important function of the core is, of course, to charge you for making the calls in the first place.

Essentially, the core network is where all the intelligence in the system lies and when a network goes down, this is going to be where the problem is. Complications arise when the switches, or the connections between them, start to fail. Other switches can then re-route around the problem by taking calls via another pathway through the network of switches but that increases the traffic load on those other routes that can then lead to further problems and potentially more crashes.

On top of that there's also the problem that most networks have two cores - one for the 2G network and one for 3G. That's all very well and good but that can also lead to issues when switching between the two with calls being dropped and sleeping phones which fall off the radar altogether for periods of time.

So, if you want a core network that's going to offer quality, then one idea is to do something like Vodafone has done. The Newbury-based company has just completed a 3-year overhaul of their core to arrive on the other side with a single unified network dealing with both 2G and high speed data services as well. What's more, it's designed with the switches connected in units of pools of six. The idea is that it's a more stable structure with more interconnections that's also now highly scalable. So far, they're the only network in the UK to have done it adding more backing to their market position of service quality even if they might be surpassed in customer base by O2 and a merged Orange/T-Mobile.

Backhaul Transmission

A solid core is all very well and good but for a mobile network to really deliver, it has to be good from end to end. One weak link ruins the lot. So, to get the data safely between the core and the cell towers, you need a big, fat, bit-pipe of sorts. You can do that using microwave dishes sending signals from A to B over the air or you can hard wire the connections using copper or fibre. Naturally, you'll get a better performance out of a hard connection but then it costs a lot to lay all the cable. So how does a good network solve the problem?

Well, taking Vodafone again as an example, it's got round the issue by signing an agreement to use BT's already existing Ethernet connections which offer space for 60Mbps service. Vodafone doesn't have a 60Mbps system, nor are there any mobile devices that can use those kinds of speeds but the idea is that there's plenty of room for growth and absolutely no chance of a bottle neck in the backhaul system either now or in the near future.

Once you've got your connection choice sorted, what you really don't want to do, if aspiring to be a quality network, is to set it up such that your cell towers are all connected together in series of long daisy chains from your core network across the length of the country. Then all you need is one link up or tower to go and you can kiss goodbye to everything from Darlington to Dundee. Instead, you build in resilience by having you backhaul connections spreading out in rings with a series of failsafe loops and link-ups thrown in for good measure too. That should keep things nice and stable.

Cell Towers

The final link in your mobile network chain is the cell towers themselves. If your customers are using substandard phones with substandard built-in antennas, there's not a lot you can do about that, except tell manufacturers if you're getting consistent complaints about their handsets and, yes, this does happen.

Cell towers equal coverage and that's one of the first complaints your users might have. It's a fairly simple mathematic, the more of them you have, the better your coverage is. On top of that, there's also capacity to consider. Any one cell tower can only provide so much bandwidth for people to use.Eventually, if you've got too many people in one area trying to use the signal from the same tower, the load is going to become too much. Think trying to make a call, send a text or get online at a music or sporting event surrounded by thousands of others in the same place trying to do the same.

So, to build a good network, you not only need lots of towers spreading out all over the UK with all the backhaul to connect them up but you also have to pack them into urban areas as well. If you're really smart, then have a battalion of movable cell towers as well which can be used for special events to try to alleviate the classic half time problem at football games and such. You'll also need some pretty creative solutions when something as big as the Olympics or the World Cup hits town.

You've also got some decisions to make. The mobile network in the UK works at two different frequency groups. The first is 900MHz and the second 1800MHz and you can deploy masts working at either one. The issue is that 900 has a longer wavelength which means that its signal can travel further and with greater penetration through buildings and other objects but it's the 1800 frequency that delivers all the high speed 3G data traffic.

The temptation is to save the 900 towers for the countryside where you're looking to cover as much ground as possible and keep the 1800 for the cities where you're more worried about capacity. Unfortunately, that's why you don't get much 3G in rural areas and that particularly thick buildings in towns can sometimes block your signals. So, there's a bit of a balancing act if you want to get as best for the average user as possible.

Beyond that, the amount of spectrum you have and whether it's in one big block or several chunks makes a big difference for capacity and ultimately speed of service too. Although the frequencies are referred to as 900MHz and 1800MHz, they actually represent a range between 890MHz or so and 910MHz or so and likewise for the band of 1800. The mini spectrum is then divvied up between all the operators.

To make sure that your chunks don't get any interference from the other networks with neighbouring chunks of their own, you have to devote the outer portions of your allocation to dead zones of around 100KHz known as Guard Bands which simply act as buffers. Now, that's bandwidth that you might rather be using to carry your signals.

So, if you're lucky enough to have just one large piece of spectrum, then you only have two of these - one at either end - wasting just 200KHz. If you have lots of smaller sections to manage, then you're going to use up a lot more, and what that boils down to is less capacity at each site which translates to less speed per given number of people trying to use it. This was one of the major competition issues of the merger between Orange and T-Mobile. Once together, it offers larger sections of this sought after contiguous bandwidth, making it increasingly hard for others to keep up but also an interesting choice for mobile broadband users looking for high speed access.

Conclusions

Now next time you get annoyed with the reception on your phone you might have a better idea of what's going on. If you're getting dropped calls or generally not so hot service wherever you go, there's a good chance that your provider could do with updating its core network.

When you lose the signal in the basement or the kitchen of your town house, there's a good chance that you're working on a 1800MHz cell tower. The real key to having a perfect network though is for all three of the areas above to be put together with care, attention and probably lots of money as well. It has to be an end to end solution otherwise one issue will ruin the whole chain.

After that, you have to hope that your quality network has some cash left to ensure access to the top mobiles as well. Either that or it's one of the best reasons to buy the phone you're after out right and go SIM-only on the operator who gives you the best service.



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