The Challenges of 5G Spectrum
September 23, 2015
There has never been as much uncertainty about spectrum for a new generation of mobile service technology as there exists today for 5G. GSM was set in the 800 / 900 MHz band and 3G was set in the 2.1 GHz band. Vendors aligned their products with the target bands. There was clear focus and purpose. Then came LTE where uncertainty on spectrum began to creep. Looking back at 2006-2009 timeframe when LTE was under developments and in trials, a number of bands were identified and available instead of specific spectrum. Initially the thought was for higher bands such as 2.5 GHz, but LTE was deployed in 700 / 800 MHz first reiterating that coverage is always the lead driver for deployments of new technologies for both regulatory and practical business and operational considerations: after all, there’s no capacity challenge on new networks. Today, fragmentation of spectrum is the hallmark of LTE. While much of the same will be for 5G when it happens, it promises to be even a deeper problem.
5G is promising to add several layers of complexity due to its all inclusive nature of services which range from extreme broadband services to massive machine-type communications (mMTC) and ultra-reliable MTC. These applications have their own requirements and sweet spots for spectrum bands. Additionally, the spectrum regime will no longer be based on the exclusive licensing nature characterizing LTE spectrum, but will also include unlicensed and shared spectrum schemes. Also, the different use cases to LTE mean different spectrum bands. Fragmentation of spectrum, expansion of bands, and multiplicity of licensing schemes will be the hallmarks of 5G spectrum. This raises significant questions for vendors seeking to align spectrum requirements of future 5G products.Which bands will be available then for 5G is a mystery all in itself. The ubiquity of 5G applications, requirements and services would not exclude any band allocation in the radio spectrum. On this, no one is clearer than the GSMA: “The GSMA’s position is that three key frequency ranges are currently worthy of consideration for different 5G deployment scenarios: Sub-1 GHz, 1-6 GHz and above 6 GHz“. If capacity is a major driver for 5G as it has been for previous generations, it will be a challenge to find wide spectrum allocations in sub-6 GHz. Discussion on which bands to allocate for IMT-2020, or 5G, have only started a few months ago at the national regulator level led by the FCC last October.
The process of allocating spectrum for 5G can start with WRC-15 in November which can set in motion decisions on 5G spectrum at WRC-19. But practically, it will get more difficult to obtain sub-6 GHz spectrum, which is why 5G is pushing into microwave and millimeter wave bands. For example, in one of the first moves by a regulatory body, the FCC is investigating the suitability of such bands for access technology and the US proposal for WRC-19 for 5G spectrum includes 27.5-29.5 GHz, 37-40.5 GHz, 47.2-50.2 GHz, 50.4-52.6 GHz, and 59.3-71 GHz.
These frequencies don’t present a practical and economical approach for carrier deployed networks in the traditional planned fashion. The use of microwave and mmWave bands requires a different, consumer-led process to setup service. The restricted coverage area requires different spectrum licensing schemes: how spectrum should be assigned goes hand-in-hand with what spectrum to assign.
The challenges of spectrum for 5G make all predictions of early deployments – as early as 2020 – wishful thinking in my opinion. Carriers have invested much in LTE and will continue to invest beyond 2020. That’s why some have voiced apprehension about the 5G hype, blaming it on vendors as did Douglas Li the CEO of SmarTone. His comments resonate with many carriers who are not as bold as to voice that publicly. In the end, carriers have to recoup their investments before making new ones. A 5G technology vision based on similar approach to previous generations runs a major risk of hurting rather than benefiting the industry. Spectrum harmonization improves financial metrics and the lack of it increases the risk of 5G for operators.