Telecom firms (or telcos to their friends) build the infrastructure that connects peoples’ devices to their beloved content. They’re often broken down into two further subsectors: the infrastructure firms that manufacture the chips, towers, and cables that carry a connection and the service providers that let you access that equipment. American Tower, for example, owns the cell towers that make network connections – and it gets paid rental fees by the likes of Verizon, who then in turn collect subscriptions from end-users like you.

An infrastructure company’s business model is fairly simple: build technology and then sell or rent it to others. Service providers, meanwhile, historically made money by hawking regular cable, internet, or cellphone subscription products – but after a bruising decade of rising infrastructure costs and falling subscription prices, they’re increasingly looking elsewhere to eke out extra revenue. Firms such as Safaricom, Kenya’s most valuable company, have experimented with mobile payments: its M-Pesa unit makes it over $1 billion a year. Others, regarding the rise of advertising giants Facebook and Google with envious eyes, have invested in their own advertising platforms. Singapore’s Singtel has spent over $1 billion buying “adtech” firms in the hope of selling its enormous bank of user data to companies seeking to better target customers.

But infrastructure firms and service providers alike are now on the cusp of a major technological change: 5G. Speedy fifth-generation mobile internet networks are already available, and are expected to become much more widespread in the next few years. That’s going to be hugely expensive: investment bank Morgan Stanley forecasts $872 billion of investment over the next decade, almost twice what was spent on 4G. This is partly because 5G signals, which can’t travel as far, require more antennae than 4G – which may lead to an expansion in shared “virtual networks” like Walmart’s Straight Talk or the UK’s Giffgaff. It could also lead to consolidation in the industry: industry giants T-Mobile and Sprint have been trying to merge for two years.

Still, for those firms left standing, 5G could prove to be much more lucrative than 4G. Executives wax lyrical about the promise of the “internet of things” (IOT): a world where almost every device connects to the internet via a 5G network. That includes doorbells, self-driving cars, medical devices, factory equipment, even fridges – and could mean millions more devices using a lot more data, as well as plenty of profits for the firms furnishing those connections. 5G may also replace wired networks in some places, with factories particularly keen on the idea. According to Morgan Stanley, 5G may generate $156 billion in revenue for telco service providers.

Infrastructure firms stand to do even better, as they can capture the service providers’ need to upgrade without worrying about whether consumers and companies will be willing to pay for them. Chinese giant Huawei is the market leader in 5G technology, though it faces security-related roadblocks to expansion in the US, and companies like American Tower should also see increased revenue. Indeed, those service providers who own their own antennae networks are starting to “spin them off” into separate firms in an attempt to raise cash to fund 5G development – as well as satisfy investors who’d rather bet on just towers. Those sales should also help firms like AT&T and Vodafone get a handle on their debt – which, as we’ll see next, is a key concern…

The takeaway: Telcos either sell infrastructure or services, and in the face of high 5G costs they’re now looking to eke out extra revenue from new lines of business.