Sprint is lagging behind other carriers in America with its 4G LTE network expansion, which explains why it has recently announced its goal of bringing LTE to more than 100 new markets in the coming months. Although 4G LTE is the “it” thing in the telecom industry, it’s clear that there are still many wireless customers out there who are still stuck on 3G.

A recent filing made by Sprint to the Securities and Exchange Commission (SEC) reveals that the carrier spent $200 million on legacy 3G platform equipment in the third quarter of the year to improve the capacity on its CDMA network.

It’s simply a case of Sprint wanting to make sure that it can handle the increased data usage on its legacy network, while slowly rolling out of the more advanced LTE network. It’s not going to be the last one either. Sprint wrote on the filing: “We expect additional capital expenditures of legacy equipment until our network modernization is substantially complete.”

Talking to Fierce Wireless, Sprint spokesman Scott Sloat explained that the spending was a necessity, given that the company has to accommodate more users on its platform, particularly smartphone users. Sloat noted that Sprint added more than 900,000 new subscribers in Q3.

Sprint said it’ll keep encouraging subscribers with 3G devices to make the jump to 4G LTE. So far, the carrier has sold over 1 million 4G LTE-enabled devices to its subscribers, whom we're sure can't wait to get 4G LTE signal bar on their devices. We hope some of them won't mind waiting until the end of 2013 for the LTE roll out to be completed.