Capacity or Coverage?

At the start of their lives, wireless networking technologies have historically lived or died by their ability to provide network coverage across a given area. This makes sense; after all, without the capability to provide a satisfactory level of geographical coverage, the network is much less useful.

Consider cellular networks. Between 2G, 3G and 4G today, there are few areas in developed countries where a signal is unavailable; they do exist, to be sure, but after decades of multi-billion-dollar investment they are so infrequent when the scope of these networks is considered that the coverage problem is largely solved. These networks are by far the most valuable of all wireless networks, as shown by the revenues pulled in every year by the major cellular operators.

The same applies to Wi-Fi, although this is more dependent on the individual deployment. Whether residential, enterprise or commercial, where Wi-Fi coverage was once spotty and best-effort it is now a high priority, leading to excellent coverage in many areas both indoors and outdoors. By doing so, the value of the average Wi-Fi networks has increased, with it now being the primary and often only method of network connectivity for non-cellular devices.

If coverage is largely (although not completely) solved today, what is the next stage in the evolution of the wireless network?

At the same time as these technologies have matured in terms of coverage, the user appetite for wireless data connectivity has increased at an unprecedented rate. Wireless networks are now the preferred and often only option for users and devices to connect to the internet, and their usage patterns have intensified significantly with the advent of streaming video, bulk data applications, social media and real-time communications.

Capacity is now the challenge, and it is arriving harder and faster than the designers and operators of today’s wireless networks expected. These networks are oversaturated in many areas, attempting to transmit volumes of data from a number of users both higher than they were originally intended for.

This is a natural and even desirable evolution; it shows that the wireless network is delivering sufficient value to its user base, as otherwise the usage of the network would hold steady or decline in terms of both number of connected devices and data consumption.

However, this evolution doesn’t apply to all wireless technologies. Some, such as Bluetooth, are designed specifically for fairly low data rate, personal-area communications, and have no desire to scale up to the level of coverage or capacity of Wi-Fi or cellular technologies.

So, when designing or implementing a wireless network, which is more important today: capacity or coverage?

The answer, as ever, is it depends. Networks are required to provide coverage over a certain area as a prerequisite for them to be useful at all. However today, in a given area, a network typically already exists to provide coverage to that area. Cellular technologies such as LTE are foremost amongst these, but many areas also have wide coverage from Wi-Fi as well, particular enterprise buildings and some indoor spaces such as homes and malls.

What can now be seen is a shift from designing both technologies and networks for coverage, to designing them for capacity.

New networks will be deployed increasingly as high-capacity ‘islands’ in a ‘sea’ of lower-capacity wide-area connectivity, both indoors and outdoors. This is network densification at work, and can be thought of multiple networks deployed in a single location for different tasks, capacity or coverage.

A good example of this is the 802.11ad Wi-Fi standard, operating at multiple gigabits per second using the short-range 60 GHz band. In an indoor network, wide-area coverage is provided by 2.4 or 5 GHz Wi-Fi, with 60 GHz ‘islands’ supporting opportunistic capacity for very high-bandwidth tasks.

This shift relies on an area already having a satisfactory blanket of network coverage to be a worthwhile investment, but can pay significant dividends if this condition exists. By removing strain from the wide-area ‘overlay’ network, the addition of these ‘islands’ can greatly improve overall network capacity and benefit the user experience greatly.

Both coverage and capacity are crucially important in the modern wireless network. Without both of these, network operators will be increasingly pressed by the rising demand for bandwidth and the advancing expectation of uninterrupted network connectivity.

Expect to see a lot of areas with a ‘sea’ of network coverage today having ‘islands’ added very soon.