Spectrum Use and Options
Spectrum use and availability are the most important factors in fielding a viable 5G network, as they will determine the speed, volume, and latency of data transfer going forward. 4G data transfer capabilities cannot keep pace with current demand, and the 5G step-change would address the increasing rate of data consumption by fielding a functioning 5G network using mmWave bands, sub-6 bands, or both. The following sections describe the relative strengths and weaknesses of mmWave and sub-6 approaches, as well as their potential applications and roles in a future 5G ecosystem.
Millimeter Wave (mmWave)
MmWave spectrum operates in high frequencies found between 30 GHz and 300 GHz, and is attractive for a number of reasons. First, the shorter wavelengths of mmWave create narrower beams, which in turn provide better resolution and security for the data transmission and can carry large amounts of data at increased speeds with minimal latency. Second, there is more mmWave bandwidth available, which improves data transfer speed and avoids the congestion that exists in lower spectrum bands (prior to researching potential 5G uses of mmWave frequencies, the only major operators in that area of the spectrum were radar and satellite traffic). A 5G mmWave ecosystem would require a significant infrastructure build, but could reap the benefits of data transferred at up to 20x the speed of current 4G LTE networks. Finally, mmWave components are smaller than components for lower bands of the spectrum, allowing for more compact deployment on wireless devices. Outside of its physical properties, MmWave is also attractive to U.S. 5G developers because the U.S. government owns large swaths of the sub-6 spectrum, particularly in the 3 and 4 GHz range, making it difficult for carriers to purchase dedicated spectrum licenses at FCC auctions or even to share that part of the spectrum.
However, mmWave has its share of challenges. While its short wavelengths and narrowness of its beam allow for improved resolution and security of data transfer, these qualities can also restrict the distance at which mmWaves can propagate. This creates a high infrastructure cost, as a mmWave network would require densely populated base stations throughout a geographic area to ensure uninterrupted connectivity. This challenge is further aggravated by the fact that mmWaves can be easily blocked by obstacles like walls, foliage, and the human body itself. MmWave spectrum can achieve extended range in specific circumstances, such as in large buildings with flat reflective windows above the tree line, but few environments in the United States are conducive to this type of propagation.
Various studies have begun to test the efficacy of mmWave and sub-6 infrastructure builds in the United States. MoffettNathanson LLC recently conducted an analysis of Verizon’s 5G mmWave efforts in Sacramento and discovered that after roughly six months in the market, Verizon’s ~150 fixed wireless broadband (FWBB) base stations can only offer service to around 6% of residential addresses in the tested areas.[1] Verizon has been targeting particularly dense
- ↑ Craig Moffet, Ray McDonough and Jessica Moffet, “Fixed Wireless Broadband: A Peek Behind the Curtain of Verizon’s 5G Rollout,” p. 7, MoffetNathanson, March 20, 2019, https://www.moffettnathanson.com/?Section=Media%20/Telecom.
