Which are the main constraints of 5G network deployment?

The countries who are leading in the 5G area are:
South Korea, Followed by USA and Australia.

I am quoting an excerpt of a report by Arthur D Little here:
“All leading countries have in common that they have already allocated 5G spectrum. These countries have enabled operators to roll out 5G networks quickly, many commercially, in 2018, and to trial use cases successfully”.
The Consumer Use cases range from:
Gigabit bandwidth to the Home And Next Gen Mobile User Experiences,
The corporate Use cases are:
Enterprise, Wholesale
While Autonomous Cars are being touted as one of the Key Industrial revolution beneficiaries.

Challenges are:
5G Spectrum Availability.
5G CPE and End User Devices availability and real roadmaps.
Upgrade of the Interconnect networks and Telco Backend Networks and the associated costs
Current penetration of high speed fixed and mobile (lTE/4G) broadband and usage
etc etc
As with all major technology advances 5G shall start of in telco backends and interconnects and then adoption by Large Enterprises ( lookup Campus Networks), and then with Moores law and affordable devices wide adoption…

1. Interworking with existing 3G/4G networks.
2. Spectrum availability
3. Lack of standards
4. Security and Regulatory compliance
5. Vendors availability
6. Lack of Business Model to approve funding for the project

5g meant to interwork with 3g/4g but other wireless techno as well such as wifi ...
Moreover , one of the 5g main pillar is resources sharing (nw sharing ...)which will become paramount compared to previous technologies scenarios and this could be one of the biggest challenges for operators.
NW (access+core )sharing associated with NFV, slicing 5g technologies will, in my opinion ,enable new business cases in a tough competitive environment by providing very high bandwidth on demand with required SLAs ...

Firstly, I believe spectrum availability is a key challenge

Secondly, from a subsaharan African perspective, the cost of deploying on those high spectra will be another bottleneck. Most 4G deployments in the region were done on refarmed 2G and 3G frequency because the cost of the available 4G spectrum was high i.e 800MHz and 2600MHz. Even for operators that deployed on 4G spectrum, most were on 800MHz rather than 2600MHz because more infrastructure would be required for coverage for the latter. So with 5G deployments on the higher spectrum, cost of deployment will even be higher compared to 4G.

Lastly, the lack of localised use cases will also be a constraint. The value proposition of 5G has to go beyond high-speed internet to selling points that actually help both consumers and business solve problems i.e either cutting cost, increasing efficiency or increasing revenue. Therefore, the business model of 5G is a constraint