The City of Sacramento has deployed 300+ small cells as part of a 5G Fixed Wireless Access deployment with Verizon. These deployments can only provide partial 5G coverage of a city like Sacramento. This is because of the relative transmission range of 26Ghz and 28Ghz spectrum. In fill is required with further small cells and coverage fill is required at mid-band Spectrums like 3.5Ghz.
Sacramento 5G FWA Coverage
The most effective way of delivering backhaul to multiple small cells sites is to use SD-WAN technologies over either Ethernet or microwave links. WAN Optimisation requires an intelligent-path control mechanism for improving application delivery and WAN efficiency. This intelligent path control and management of VPN tunnels needs to be integrated into the network slice management control plane function in order to guarantee the mission critical services.
The Network Slice Management control plane needs to manage end to end the latencies and traffic shaping. To do this the SD-WAN component for small cell backhaul must be an integral part of the end to end network orchestration.
Master Orchestrator Problems
The challenge for telcos face is how to integrate technology specific orchestrators. A 5G SD-WAN small cell solution could involve four unique orchestrators:
small cell orchestrator
with a 5G core orchestrator
a network slice orchestrator (NSSMF)
and multiple existing SD-WAN orchestrators
Most telcos have already deployed a SD-WAN products, involving multiple SD-WAN CPE vendors, where each CPE vendor provides a bespoke orchestrator. Industry examples include, the Cisco Viptela SD-WAN solution which uses a vManage network management solution within the orchestration / management plane and the Nokia Nuage SD-WAN solution that follows the same pattern.
To break this predominance of orchestrators (with lots of compensating logic) it is important to seek integration by API direct to the control plane. To be successful telcos may wish to examine how a vendor agnostic Network as a Service may improve their 5G orchestration strategy.
FWA is not a new idea with 5G and has been available to anybody tethering since 3G. FWA is comparable to Fibre-to-the-Home as both are connectivity solutions for the edge of the network. 5G mmWave (~25Ghz and above) is promising an alternative to FTTH, with 1Gb per second download speeds. It is therefore worth understanding the technologies and engineering necessary to make FWA a viable or better alternative to fibre.
Verizon has targeted FWA as an alternative to FTTx with its 5G Home service launched across Houston, Indianapolis, Los Angeles and Sacramento in October 2018. Verizon estimates the 5G mmWave FWA addressable market to include 30 million premises. To be successful Verizon’s FWA has to be cheaper than the delivery of FTTx and will have to overcome some quite considerable engineering challenges. These include the roll-out of multiple 5G antennas with small-cell front-haul for extended coverage, the deployment of external to home 5G receivers, a distributed core that can host Mobile Service Edge and CDNs close to the 5G Cell Towers, and a new 3GPP Release 16 Core that can support network slicing for the 28Ghz spectrum.
FWA logical architecture
The above diagram shows a logical architecture for a 3GPP Release 16 compliant new mobile core connected through multiple distributed sites connected to radio site gNodeBs delivering FWA service to the home. A new core is not fully necessary, as Verizon are launching already using their channel coding, multiplexing and interleaving technologies. A new mobile core will be advantageous in guaranteeing the QoS for mmWave FWA slices.
The majority cost for FWA is in the delivery of the radio network and mmWave antenna. Higher costs will always be incurred if RAN planning has not been optimised and necessitates 5G small cell in-fill. For this reason mmWave may be better deployed as new sites in a standalone Model 2x configuration. Other costs include upgrading the mobile core but this cost is shared with other 5G use cases. Spectrum licencing is another important cost. Currently mmWave licence spectrum is relatively available, hence lower cost, and more extremely high frequency is being released by national regulators.
To be competitive FWA must be economically viable against fibre delivered to the home. This includes internet peering & CDNs. In regulated territories like the UK that already have Local Loop Unbundling the competitor CSP can consume service from the distributed site. This has been part of the US regulatory framework since the US Telecommunications Act of 1996 that requires ILECs to lease local loops to competitors (CLECs). In an all fibre model the cost of connection is to the premise (FTTP) or home (FTTH). If regulatory dark fibre or open ducts are in place then the competing CSP can consume those services at a regulatory defined price. In the UK that model is only being developed after initial regulatory challenges and in the US the FCC has not extended enforcement of dark fiber offering since 2014. It is therefore suitable for a US mobile carrier to consider 28Ghz as a more efficient distribution mechanism than FTTH if there are no regulated dark fibre or open-duct solutions available. It is also worth considering that the civils part of the delivery of fibre (the dotted FTTH line in the below diagram) can cost as much as 90% of the total service delivery cost.
Simplified FTTH Architecture
A final comparison between FTTH and FWA:
Same Costs: Network spine, backhaul and equivalent equipment are the same for FTTH & FWA
Higher FWA Costs: The spectrum licence costs are unique to FWA but due to spectrum availability may not be prohibitive, power & cooling costs are higher for FWA and the maintenance cost of FWA should be higher for exposed antennae
Higher FTTH Costs: The only cost that is higher with FTTH is the civils part of delivery. This cost can be very high because of the complexity of getting wayleaves and permissions and digging up roads.
In conclusion, FWA should be more efficient and cheaper service to deliver as long as the network planning is accurate and does not necessitate continual modification based on further cell deployments.
API Crazy 