It may not have been exactly transformative, but 2015 saw the continuation of several important trends and the emergence of others. T-Mobile (NYSE:TMUS) built on the momentum it began to generate in 2014 with its "un-carrier" marketing campaign, expanding the initiative by adding data-free video streaming (Binge On) and expanding its data-free music streaming (Music Freedom) with new content partners. T-Mobile's disruptive strategy paid big dividends this year as the carrier passed Sprint (NYSE: S) to become the nation's third-largest operator and stoked at least some competition among the tier-ones.

T-Mobile's impact was also evident as its fellow carriers continued to move away from lengthy contracts and handset subsidies and toward equipment installment plans or phone leases. Even longtime holdouts Verizon (NYSE: VZ) and AT&T (NYSE:T) finally began to succumb, phasing out contracts in favor of equipment installment plans (EIPs) with activation and upgrade charges. Those moves marked the beginning of the end of an underpinning on which the U.S. wireless market was built.

Meanwhile, operators spent much of the year shutting down legacy networks as they continued to transition to LTE and laid the foundation for 5G rollouts and technologies such as software-defined networks (SDN) and network function virtualization (NFV). T-Mobile killed MetroPCS' CDMA network, AT&T did the same for the network it inherited from Leap Wireless, and Sprint began to pull the plug on Clearwire's WiMAX towers nationwide.

And from the everything-old-is-new-again file, carriers rekindled their pursuit of the kind of mobile-video initiatives that failed to find an audience when they first surfaced nearly a decade ago. Verizon launched Go90, an over-the-top video offering targeted directly at mobile users, and AT&T is preparing to leverage its acquisition of DirecTV with a mobile-focused offering set to launch in the coming weeks. T-Mobile took a different tack, packaging content from multiple providers for its Binge On program, which delivers zero-rated video content from multiple providers. Consumption of mobile video is clearly on the rise, but whether carriers can leverage that trend is still far from clear.

Finally, Apple (NASDAQ: AAPL) continued to enjoy remarkable momentum as a smartphone vendor even as its vulnerabilities began to show as we enter the post-smartphone era. Cupertino once again claimed the overwhelming share of smartphone profits throughout the year, managing to maintain high margins in a space where slim margins are the norm and where smartphone growth is slowing substantially worldwide. Apple faces headwinds though as it expands beyond smartphones into newer markets such as wearables and the connected car -- but its dominance in the massive smartphone market cannot be denied.

These trends will all play important roles as we enter 2016, and important new ones are sure to emerge in a market likely to grow more dynamic in the coming months. Which is why we're likely to see more disruption and increased competition among carriers, manufacturers and perhaps even OS providers in the coming year.

FierceWireless analyzes five of the most important topics from 2015 in this report. We're looking forward to reading your comments. Also, don't forget to check out the 2015 Year in Review by FierceCable, the 2015 Year in Review by FierceOnlineVideo, the 2015 Year in Review by FierceTelecom, the 2015 Year in Review by FierceWireless:Europe and the 2015 Year in Review by FierceWirelessTech.

P.S. FierceWireless will be on a publishing break from Dec. 25 through Jan. 4. We'll be updating the site with any breaking news, but you won't see us in your inbox until Monday, Jan. 4.