The 3GPP 5G specification was unique in that it included the use of mmwave technology. The telecommunications industry has broadly recognized that demand for wireless services is increasing at an exponential rate, and the use additional frequency spectrum in the mmwave band from 24 GHz to 43 GHz is required to meet such demand. This situation is illustrated in Figure 1, as presented by the research group Mobile Experts in their April, 2022 report “5G Millimeter Wave 2022”.
Figure 1: 5G Strategic view: Necessary for mobile capacity (Source: Mobile Experts. Average shown for top urban markets in USA)
As can be seen, the red line indicates the exponential growth of user demand. Intuitively, a significant portion of this demand can be attributed to a trend towards higher bandwidth content, most notably video. Applications such as Tik Tok, Reels, various streaming services and video applications dominate mobile traffic. Further, the growth in uplink traffic is significant as well, with applications such as Zoom video, Twitch or simply shared 4K videos shot on the latest iPhone.
The gray bars indicate the exiting and projected sub-6GHz network capacity in the top US markets. As can been seen, the projection indicates that based on current projections, the carriers will begin to run out of capacity by the end of 2023. The black bars indicate the use of 5G mmwave capacity, which has already commenced in 2020, but is expected to accelerate over the next 5 years.
Another important market dynamic in the carrier space is the continued growth of fixed wireless access. In the second quarter alone, Verizon and T-Mobile saw combined new net additions of over 550,000 fixed wireless customers, according to their financial reporting. Verizon Business CEO, Sampath Sowmyanarayan, mentioned their FWA business is growing at an ‘unprecedented’ clip. This is a clear indication that there is room for improvement in the broadband access market. Globally, according to the June, 2022 version of the Ericsson Mobility Report, during the last 6 months (before June, 2022) there’s been a 30% increase in the numbers of carriers providing FWA service. As can be seen in Figure 2, the number of FWA customers in the carrier market is expected to double to 225M.
Figure 2: Global Fixed Wireless connections (millions) (Source: Ericsson Mobility Report, June 2022)
There is a looming challenge for carriers related to their highly successful acceptance of their fixed wireless services. At present, a large number of their FWA customers are using sub-6Ghz spectrum. The average US household uses about 514GB of monthly data. This is in contrast to the average monthly mobile use of 14.6GB (2021). Additionally, the average cost of home internet is $64/mo, while consumers are paying in the range of $80/mo. As can be seen, the mobility business is much more lucrative than the broadband business in the US. It stands to reason that eventually, while carriers are seeing tremendous growth in their FWA business, the best way to address that market is using mmwave technology, while utilizing their mid-band technology for their mobile customers.
mmWave technology itself presents a host of technical challenges that have been resolved in order to make it commercially viable.
Starting at 24GHz and upwards, there is a significant amount of free space loss compared to sub-6GHz. As such, a key element of mmwave technology is the use of a phased array system for both transmitting and receiving. A phased array system includes phase shifters, power amplifiers and associated antenna elements. On the transmit side, the system utilizes the concept of constructive interference to aggregate serval sinusoidal signals into a focused RF beam. The strength of this RF beam is a function of the number of radiating elements (power amplifiers) as well as the number of antenna elements. As such, in contrast to an isotropic device in the sub-6GHz band, a mmwave device utilizes the concept of a phased array to focus RF energy to overcome the fundamental problem of free space loss.
An additional component of a phased array system is the use of phase shifters. As the name suggests, these devices shift the phase of each individual amplifier in order to steer the beam in a particular direction. This ability is a key element of a mmwave system. In the fixed wireless application, the consumer normally has a fixed line of sight the base station. In order to optimize the link margin, it is often necessary to steer the beam to an optimal location. As such, not only is beam forming an essential aspect of mmwave systems, the ability to steer the beam is important as well.
Another important aspect to mmwave systems is the need for the antenna array to be in close physical proximity to the amplifiers. This is necessitated by significant transmission loss of mmwave signals on a PCB, as well as the importance of the choice of PCB material. Engineers like to keep the length of the transmission lines to less than 1mm, in other words in physical contact. This requirement has promoted the use of RF modules in the mmwave market, whereby the antenna is built into the PCB, and sold as an integrated unit. This removes the vagaries and sensitivities of mmwave design and provides customers with a tested device with guaranteed performance.
To summarize, the growth of wireless demand is viewed to be unabated for the foreseeable future. While existing wireless technology support the current demand, it’s clear additional wireless spectrum will be required in the future. mmWave technology has matured over the last several years and will be a primary component of all major carrier networks in the years to come.
