Unexpected sources such as bug zappers and radio towers can wreak havoc on a radio-frequency identification deployment. At least that''s what IBM Global Services is discovering as it rolls out RFID for Wal-Mart Stores Inc.

IBM Global Services has deployed RFID equipment in the grocery sections of seven pilot Wal-Mart stores, in support of the retailer''s RFID project, which officially kicks off Jan. 1. Wal-Mart has six weeks left to finish deploying RFID software and integrating middleware in about 143 Wal-Mart stores and several distribution centers.

During the deployment, IBM consultants have encountered interference from handheld devices such as walkie-talkies, forklifts, and other devices typically found in distribution facilities. And nearby cell-phone towers, which transmit at the high end of the frequency band, sometimes leak unwanted radio waves into the RFID readers. Bug zappers in the grocery sections of the pilot stores also caused interference. "When you have a bug that hits the zapper, the RF power generated by the interaction with the bug produces noise in the coax cables," says Douglas Martin, executive consultant at IBM Global Services.

Martin shared IBM''s lessons learned at the Wireless Internet for the Mobile Enterprise conference on Tuesday held at the University of California at Los Angeles. IBM will continue to look for other potential problems: It''s currently visiting different Wal-Mart sites to find any other equipment that might interfere with RFID. Martin told the standing-room-only crowd of about 125 high-level industry executives and a handful of UCLA faculty members at the conference that any company considering RFID implementation should conduct similar site visits to seek out possible RF interference.

Next, IBM''s taking its experience abroad to China. Since many of Wal-Mart''s suppliers manufacture and ship products from Asia, Martin says a group from IBM is going to China in four weeks to work with companies tagging and shipping products directly from that region.