TELECOMMUNICATIONS : Nextel Says It Will Buy Motorola Radio Rights : Telephones: Licenses would help firm create a network to compete with cellular systems.

Nextel Communications Inc., a small company that provides radio service for taxi fleets and construction crews, said Tuesday that it is buying the mobile radio licenses of Motorola Inc. in a mostly stock deal valued at $1.8 billion.

Separately, Nextel said Japan’s Nippon Telegraph & Telephone Corp. will provide technical assistance in creating a seamless nationwide mobile telecommunications network. By transforming so-called specialized mobile radio licenses now used for pagers and fleet dispatch services into full-fledged mobile telephone and data systems, Nextel plans to offer an alternative to the existing cellular phone system.

The Rutherford-based company plans to accelerate the construction of its nationwide network by one year so that it is largely completed by the end of 1995, said Nextel Chairman Morgan E. O’Brien.

“Our goal is to have substantial buildout by . . . 1995,” he said.

Nextel may announce another major deal soon. O’Brien said Nextel should forge an alliance with a major long-distance company in the near future to provide truly nationwide coverage to its subscribers.

The leading candidate appears to be MCI Communications Corp., which already has an agreement with Nextel to provide long-distance services and has expressed interest in buying a major stake in a wireless communications company. Under its agreement, Motorola can sell the Nextel shares it would receive in the transaction if a strategic opportunity arises, O’Brien said.

MCI’s biggest competitor, American Telephone & Telegraph Co., has already announced plans to merge with McCaw Cellular.

Under Nextel’s 10-year agreement with NTT, Japan’s largest employer, NTT will dispatch teams of engineers to help design and build the link between Nextel’s Motorola-supplied radio transmitters and the public telephone system. NTT has agreed to pay $75 million for 1.5 million Nextel shares, and would earn $14 million in fees for the first two years.

The Motorola transaction, in contrast, would strengthen Nextel’s presence in many of the areas where it already owns radio channels. In Los Angeles, for example, Nextel would be able to shift Motorola’s frequencies in outlying areas to its transmitters in more densely populated zones, increasing system capacity. The Los Angeles system is expected to debut in January.

Nextel plans to offer coverage over virtually the entire state of California by the first quarter of 1994, before expanding its digital services to New York and Chicago by mid-1994.