In a brief interview at 4G World on Tuesday, Matt Carter, president of 4G at Sprint Nextel, admitted that the carrier lost some potential customers in the markets were 4G was first deployed, because of spotty WiMax coverage.

Carter said: "We lost some customers in early deployments." Though the first 4G deployments by Sprint took place in the Baltimore area, Carter refrained from pinpointing the areas in which the problem occurred.

However, Carter also added that, in recent months, WiMax coverage within a given market had touched the "acceptable" range.

Noting that there are a number of things that result in spotty coverage, Carter said that in some cases of uneven WiMax coverage, a WiMax-embedded USB dongle on a laptop or on handsets like HTC Evo 4G and Samsung Epic apparently switched users over to a 3G CDMA network, in case of unavailability of a 4G WiMax network.

In addition, Carter said part of the problem also developed from working with the WiMax infrastructure provider, Clearwire, which though majority-owned by Sprint, operates as a separate entity.

Hinting at some control concerns over the Wimax deployment, since Sprint is both an owner and customer of Clearwire, Carter said that the "coordination and collaboration" was increasingly getting better, with the WiMax technology having been rolled out in 55 US cities, reaching 63 million people.