The wireless mobile ad hoc network (MANET) has received a lot of attention recently. This paper considers the channel assignment problem in a MANET which has access to multiple channels. Although a MANET does not have the infrastructure of base stations, interestingly its channel assignment can be conducted efficiently in a way very similar to that in cellular systems (such as GSM). In this paper, we propose a new location-aware channel assignment protocol called GRID-B (read as GRID with Channel Borrowing), which is a sequel of our earlier GRID protocol [Location-aware channel assignment for a multi-channel mobile ad hoc network, Technical Report NCU-HSCCL-2000-02, 2000]. The protocol assigns channels to mobile hosts based on the location information of mobile hosts that might be available from the positioning device (such as GPS) attached to each host. According to our knowledge, no location-aware channel assignment protocol has been proposed before for MANETs. Several channel borrowing strategies are proposed to dynamically assign channels to mobile hosts so as to exploit channel reuse and resolve the unbalance of traffic loads among different areas (such as hot and cold spots). We then propose a multi-channel MAC protocol, which integrates GRID-B. Extensive simulation results are presented to show the advantage of the new GRID-B protocol.