Confronted with a reluctance by advertisers to commit to upfront buys for next season, NBC has lowered its ad rates, breaking ranks with other networks, the Wall Street Journal reported Thursday. (Electronic Media magazine reported on its Web site that NBC was selling ad inventory at 5 percent below last year's rates.) As a result, the newspaper said, the network is well ahead of other networks in selling ad time for next season. "We had to give some price concessions to get an even bigger share of the market," NBC Television Network President Randy Falco told the newspaper. Nevertheless, ABN Amro analyst Spencer Wang predicted that NBC's upfront sales would reach $1.75 billion for the 2001-02 season, down from $2.2 billion last year, a 22 percent drop.