Mallinson: Cellular and Wi-Fi are complementary, but need for more licensed spectrum is urgent

Keith Mallinson

Long gone are the days when many cellular and Wi-Fi aficionados would largely shun each others' technologies for accessing the Internet away from the home and office. Attending Avrens' Small Cell World Summit and Wi-Fi Global Congress events in London over the last few weeks revealed to me how very much the two communities now value what each other has to offer. Indeed, cellular technologies and operator services are highly complementary to those for Wi-Fi. This symbiotic relationship will continue and grow despite the fact that technological developments and commercial network deployments are making cellular increasingly able to provide the performance of Wi-Fi in the local area; and vice versa with Wi-Fi becoming more mobile by adopting many cellular-like capabilities. 

If mobile broadband growth is to continue at current triple-digit percentage rates there will need to be much more than the doubling of the current spectrum allocations slated for the next decade. Improving radio technology, increasing cell site density (including small cells and Wi-Fi offload), and substantial amounts of additional spectrum are the three compounding supply factors that must all contribute to the required increase in wireless network capacity.

In-building small cells are improving cellular coverage and increasing capacity through spectrum reuse. In addition to Wi-Fi in the office and at home, Wi-Fi access points are being installed, with high density per square kilometre, indoors and outside in public places where pedestrians gather or wander (e.g., in shopping centres, sports stadiums and transportation terminals). Improved Wi-Fi capabilities in handover and roaming enable a more cellular-like experience among these communications hot spots and in combination with cellular services.

Cellular will continue to prevail in providing wide-area geographic coverage, with high mobility for use in cars and trains, and in its ability to provide assured quality of service through use of licensed spectrum with exclusive use.  Cellular network operators are also increasingly using Wi-Fi on unlicensed spectrum with shared use to offload mobile broadband data traffic in places where demand is most intense. However, with numerous service providers and private users on an uncoordinated basis in public areas, Wi-Fi networks can become overcrowded and provide poor quality of service. Wi-Fi's popularity often leads to a tragedy of the commons: networks may provide little or no throughput at certain times and in some places.

Some go hungry when free lunches get scoffed up

Whereas additional unlicensed spectrum will be welcomed by many users and may provide some relief to current overcrowding, this may only be partial and short-lived in public places where there are many users.  There is virtually limitless appetite for free broadband connectivity as users become accustomed to using broadband applications such as those that stream or download video. The higher speeds available with Wi-Fi enhancements including 801.11n (theoretically up to 130 Mbps) and 802.11ac (theoretically up to 1 Gbps) stimulate this demand and can exacerbate traffic overloads. With increasing speeds on cellular technologies including LTE (theoretically up to 100 Mbps already and increasing), and growing popularity for mobile broadband services on smartphones, most operators have had to eliminate flat-rate, all-you-can-eat pricing to temper demand because a very small proportion of customers were consuming the vast majority of network resources. Similarly, increasing "free" and shared capacity with Wi-Fi over unlicensed spectrum will rapidly bring about spectrum exhaustion at busy times in many places.

In contrast, licensed spectrum with allocations through auctions and on the basis of coverage and service commitments is economically efficient and has fostered outstanding growth in cellular, including mobile broadband. Cellular operators are most incentivized to deploy scarce spectrum resources on the basis of its costs and the revenues that accrue from its use. Prices per gigabyte of data carried over cellular networks continue to fall dramatically.  Operator services revenues are flat or declining in most nations despite exponential growth in mobile broadband. According to the GSMA's Wireless Intelligence research, the United States is one of the few countries worldwide where consumers are increasing their spending on mobile, while Ericsson's Mobility Report shows that worldwide network traffic demands have doubled annually.

Maximizing economically efficient use

Wi-Fi is optimized for providing high connectivity speeds over short distances to a restricted number of users on local-area networks where there is a limited threat of network congestion from the uncoordinated and uncontrolled demand that is inherent with unlicensed spectrum usage.  In private places such as homes, offices and hotel guest rooms it can be possible to provide unbridled network access over Wi-Fi with only small a small probability of blocking through wireless congestion. The relatively low cost of network equipment and free spectrum also makes it very attractive for cellular operators to offload traffic if and when there is sufficient Wi-Fi capacity available. 

However, cellular using licensed radio spectrum will remain essential for providing the umbrella of wide-area network service including broad geographic coverage, vehicle-speed mobility and high service quality. With exponential demand in growth for mobile broadband, it is essential that substantial amounts of additional spectrum be made available for cellular. This should include traditionally-licensed spectrum, and additional spectrum that is infrequently or partially used by others. This can be made available to cellular operators, but with certain restrictions reflecting when and where it might still be needed by primary licensees including broadcasters, the military, aviation authorities, the coast guard or public safety agencies.

Keith Mallinson is a leading industry expert, analyst and consultant. Solving business problems in wireless and mobile communications, he founded consulting firm WiseHarbor in 2007. WiseHarbor publishes an Extended Mobile Broadband Forecast. This includes network equipment, devices and carrier services to 2025. Further details are available at: Find WiseHarbor on Twitter @WiseHarbor.