Push-to-pay: It’s about to get expensive to stay on Nextel

Sprint(s s) has big plans for its 800 MHz iDEN spectrum. It wants to build a new 4G network parallel to the LTE network it’s currently rolling out across the country. There’s only one obstacle to that plan: 3.1 million Nextel and Boost Mobile subscribers that currently use its iDEN network in those frequencies.

Sprint has already used the carrot to coax those customers over to its CDMA network. Now it’s trying the stick: Phone Scoop has confirmed Sprint will charge an additional $10 a month fee for all Nextel customers that keep using their iDEN phones past January.

As Sprint has started shutting down iDEN sites and offering incentives to customers to switch to CDMA phones, it’s managed to lure a lot of customers off of iDEN. But if it hopes to shut that network down completely by its stated sunset date in June, it needs to accelerate that exodus. We saw AT&T(s s) adopt a similar strategy in 2006 when it started shutting down its old time-division multiplex access (TDMA) networks. It charged customers a $5 a month fee for customers who kept using their old handsets.

iDEN is antiquated 2G technology, but it has one very appealing feature in the eyes of its loyal customers: its Direct Connect push-to-talk capabilities, a walkie-talkie service which has traditionally outshone all competing PTT services in the market. Sprint has replicated Direct Connect on its CDMA 2G and 3G networks, using an IP-based technology developed by Qualcomm(s qcom). So far it has attracted 1 million customers to the new CDMA version.