Sprint Nextel says it expects to invest more than USD7 billion in 2007 as it continues to enhance its cellular networks while also rolling out a new nationwide mobile WiMAX system. The firm says the bulk of its national CDMA2000 cellular infrastructure will be upgraded with EV-DO Revision A technology by the end of the year. The rollout of WiMAX is costing USD800 million in 2007, with a further USD1.5 billion-USD2 billion investment scheduled for next year. The first 2.5GHz WiMAX services are due to be launched in Chicago and Washington DC in the fourth quarter. USD1.4 billion will be spent on Sprint’s fixed line networks, which also provide backhaul for its wireless systems. Sprint Nextel is the third largest cellular operator in the US, with 53.6 million subscribers – more than 23% of the market – at the end of March, according to TeleGeography’s GlobalComms database.