Your requirement doesn't mean anything as written: A dB value has no meaning without a frame of reference, and bandwidth is not measured in kilohertz.
The valid datarates for 802.11b are 11Mbps, 5.5Mbps, 2Mbps, and 1Mbps. If your government official meant 500 Kbps instead of 500 Khz, then WiFi will probably meet whatever he was trying to require since it cannot drop below 1000 Kbps.
