Case Study: Digital Village in the USA
The extended range opens up new opportunities to use mmWave spectrum in more sparse suburbs and semi-rural areas, which then allows lower frequencies to be offloaded. In such areas there could be several hundred households per sector. With consumption increasing on both MBB and FWA, the additional capacity that mmWave brings makes such a scenario an ideal place for the combination of mmWave and TDD mid-band, giving FWA subscribers a high level of service.
In the following simulated scenario, which models the performance achieved in field tests, we illustrate how the extended mmWave range can be used to increase capacity and improve user experience. The case is a version of the digital village case study in the Fixed Wireless Access Handbook  which has been adapted to the data consumption behavior of the USA.
The original case study includes a step-by-step solution and business case analysis showing a 22-month ROI. Here we focus on a comparison of achievable network capacity with and without the use of mmWave. The target case is a village with surrounding, sparsely populated areas where the overall housing density is about 150 apartments per square kilometer. Current broadband offerings are mainly provided by xDSL or best-effort MBB, but there is no fiber-to-the-home, making the area an attractive candidate for FWA.
The existing MBB deployment has 3km macro distance between sites and lower FDD bands are used to serve current traffic. Over time, as MBB traffic increases, MBB traffic will use some of the acquired mid-band spectrum. The excess spectrum can be used for FWA: 100 MHz TDD at 3.5 GHz and 400 MHz in the 28 GHz band.
The service targeted by the CSP is FWA with a “fiber-like” experience. This means sold DL data rates of 100-1,000+ Mbit/s with no data cap and with typical DL rates of at least 100 Mbit/s. By combining the available spectrum, including lower FDD bands and mid-bands and 28 GHz using TDD, the CSP can get a combined network deployment serving both MBB and FWA.
In this analysis, we focus on the mid-band and 28 GHz, leaving out the details on the lower bands and performance for MBB users. However, the proposed approach includes a common solution for FWA and MBB that also handles the expected growth of MBB traffic. Also, since the case is limited by the DL capacitance, we omit the analysis of the UL. In order to maximize connection performance, the chassis is based on the use of a high-performance CPE placed on the roof, supporting both mmWave and lower bands.
The system is sized to target a DL data rate of at least 30 Mbps for the 5 percent of worst-off households at peak traffic times to provide a fiber-like experience even in those worst-case scenarios, including multiple HDTV streams per household , to maintain. In terms of data usage, we define a baseline scenario, based on observed current US fixed-line broadband levels, where the average data consumption per household is 670 GB per month, of which 90 percent (600 GB) is DL traffic [10, 11].
Assuming 10 percent of daily traffic occurs during rush hour, this equates to an average usage of 2 GB per hour during rush hour. We project annual growth of 28 percent, driven in part by many households migrating from linear satellite or terrestrial TV to broadband for all media consumption, including linear TV and streamed services.
Additionally, for comparison, we have also defined an all-broadband media scenario that assumes all households have already made this transition. In this case, we assume a consumption rate of 1 TB per month per household (900 GB per month in DL), but expect a lower annual growth of 10 percent as the switch to all media consumption via broadband is already complete.
Because capacity needs to grow as the number of customers increases, as well as higher average data consumption and speed requirements, it makes sense to incrementally increase the network’s capabilities as needed. This means that the cost of increased capacity can be billed as late as possible, unlike fiber where much of the cost is incurred upfront when fiber is deployed by all homes. In addition, capacity expansion decisions can be made selectively on a sector-by-sector basis as subscribers — and revenue — increase.
Data rate for experienced users
figure 3 shows experienced DL user data rate as a function of varying system load for the worst, average, and best located homes. The blue curves represent pure mid-band delivery, while the red represent the combined mid-band and mmWave case.