A 60 GHz radio is an attractive technology in wireless home networks because it can provide high data rate up to a few Gbps. A 60 GHz network generally uses directional antennas and has a problem of neighbor discovery even though it has an advantage of high data transmissions. In particular, if a directional antenna is used in self-organized wireless adhoc networks, the neighbor discovery time and energy consumption can be significantly increased. To solve this problem, we propose a multi-band directional neighbor discovery scheme, in which management procedures are carried out by using the 2.4 GHz band with the omni-directional antennas whereas data transmissions are performed by using the 60 GHz band with directional antennas. Analytical models on the neighbor discovery time and energy consumption are also derived by considering assisted and beamforming periods in the neighbor discovery procedure through the omni-directional antenna and directional antenna. Performance evaluation results demonstrate that the proposed scheme outperforms comparative schemes that use only directional beamforming in terms of the average neighbor discovery time and energy consumption.Index Terms-Directional antennas, mmWave ad-hoc networks, multi-band application, neighbor discovery, selforganization.0018-9545 (c)