Spectrum Sharing: The Wireless Carpool Lane

The vision of urban planners in the late 1940’s and 1950’s was that of a suburban population commuting to work in the main city. People flocked to the suburbs and highways were built to connect suburbs with cities; cars were sold and soon enough the model became unsustainable. More highways were needed and existing ones needed more lanes. The model became prohibitively expensive not to mention rising public awareness to environmental issues resulting from car emissions. Municipalities soon realized the need for solutions to congested highways. One such solution is the carpool lane open to vehicles with more than one passenger. Shared transportation became encouraged: if you car pool, you’ll save time, money and help save the environment.

Wireless communications is similar in many respects. Spectrum is a scarce resource, as much as highway capacity is a limited one. More spectrum has been the mantra to date, much as more and wider highways was thirty years ago. Operator’s message to regulator is a simple one: traffic demand will exceed supply; we need more spectrum; and not all bands will work out for us. This obviously is not sustainable for the long term much as building more highways is.

But new spectrum alone cannot solve the capacity problem. It can provide temporary relief, but over the long term, new models and solutions are required. After all, spectrum is a limited resource to state the obvious. When one operator wins exclusive use of spectrum, another operator is in effect denied access to that slice: a competitive zero sum game. Enter spectrum sharing: this is the carpool lane of wireless communications where more than one operator will have access to the same slice of spectrum (lane). Sharing spectrum can be justified on a number of economic and technical foundations as has been detailed in PCAST’s report. So, given the growing demand on data services we can see that spectrum sharing techniques are bound to develop. The question is what form of spectrum sharing will take shape and when will that happen.

However, there’s a main point that we need to be aware of: spectrum exclusivity encourages operators to invest in relatively expensive infrastructure—service availability remains a major element of competitive differentiation. For spectrum sharing to take off, we need to find a way to deploy infrastructure at much lower cost than we do today. The challenge will be to develop this low cost infrastructure. One technology that’s often cited is small cell base stations. Public small cells (outdoor base stations in licensed wireless bands) have been lightly deployed in North America and Europe, but more widely deployed in Asian cities where population density is very high. They are slated to play a much larger role when spectrum sharing is made possible by regulators. But the price of public small cells will still need to be driven lower, especially if one considers the total cost of ownership that includes installation and backhaul among other costs.

The solution to the cost issue can be in new business models for wireless network operations. There is much room for new and innovative practices to fit the spectrum sharing model. The potential offered by spectrum sharing is multifaceted that will surely keep developments in the wireless industry very interesting for years to come. One can always look at how complex traffic capacity problems of are address to glimpse a part of the solution to teletraffic capacity limitations!