Modems are becoming commonplace in cars. Drivers like to use them to stream music and create wi-fi hotspots. Automakers like them for the data they can report and the updates they can push to their cars. Dealers like them because they tell drivers when to come in for service.

Today's modems run on 4G LTE cellular technology, but the future is 5G and that future isn't too far away. Experts say 5G technology could be the key to getting cars to talk to each other other, pedestrians, and the infrastructure around them—so-called "vehicle-to-vehicle" and "vehicle-to-infrastructure" communication, which is all lumped under the "V2X" moniker.

That future could come as soon as 2021, according to a report from Car and Driver.

Qualcomm, the longtime American semiconductor and telecommunications equipment manufacturer, is making a big play in the automotive business. It plans to have a cellular V2X chipset ready for the market next year, and that chipset could be powered by commercially available 5G technology by 2021, according to Nakul Duggal, vice president of product management in Qualcomm’s automotive division.

The 5G technology would give the V2X technology longer range, better reliability, and shorter delays when transferring data than the current 4G LTE tech or the dedicated short-range communications devices experts assumed cars would use for V2V and V2X communications.

V2X technology will make cars safer by transmitting information about what lies ahead, such as potholes, accidents, traffic jams, slick spots, or possibly poor driving by other vehicles, like cars running red lights. This type of information can be transmitted up to 10 times per second to prepare for the dangers up ahead.

According to Strategy Analytics, a consulting firm, 20 percent of new vehicles sold in 2015 had embedded cellular connectivity. That is expected to grow to 75 percent by 2024.

Duggal said adding modems to cars can make them safer.

"This is a safety application at the end of the day," he said. “Every car sold is going to have a modem, and our approach is to make it part of the modem. A lot of accidents are caused by poor weather conditions or sudden changes in other conditions. They’re very avoidable. From a road-safety perspective, this could definitely have a major benefit.”

Qualcomm has been working with PSA Group, owner of Peugeot and Citroen, on V2X technology for the past year and BMW is about to get on board. Those partnerships give Qualcomm an entry into Europe. The tech giant has also tested cellular V2X in Korea, China, Japan, and San Diego. Ford announced a deal with Qualcomm at this year's CES to study V2X technology, and the company has worked with General Motors on its OnStar telematics system since 2002.

In the future, cellular V2X technology will also enable self-driving car technology, pushing high-definition maps to vehicles, as well as warning vehicles what may be around the next corner.

The future is coming, and 5G is a big part of it.