In a multihop MANET (mobile ad-hoc network), reliable broadcast support at the MAC layer will be of great benefit to the routing function, multicasting applications, cluster maintenance, and realtime systems. In this paper, we propose a new hybrid MAC protocol, called the adaptive location-aware broadcast (ALAB) protocol, for link-level broadcast support in multichannel systems. ALAB is scalable and mobility-transparent since it does not require any link state information. Above all, in ALAB, both deadlock and hidden terminal problems are completely solved. In principle, ALAB tries to combine both of the advantages of the allocation- and contention-based protocols and overcomes their individual drawbacks. At high traffic or density, ALAB outperforms the pure TDMA because of spatial reuse and dynamic slot management. At low traffic or density, ALAB outperforms the pure CSMA/CA because of its embedded stable tree-splitting algorithms. In addition, ALAB provides deterministic access delay bounds from its base TDMA allocation protocol. Simulation results do confirm the advantage of our scheme over other MAC protocols, such as IEEE 802.11, ADAPT, and ABROAD, even under the fixed-total-bandwidth model.