Smart antennas are expected to enhance scalability in ad hoc networks. This paper at first evaluates three directional MAC protocols, DMAC, MMAC and SWAMP as well as the omni-directional protocol IEEE 802.11 DCF in multi-hop transmission environment. The evaluations address the problem that the performance strongly depends on the topology of routes between sources and destinations, referred to as a directional hidden terminal problem. After analyzing the problem, we propose three MAC level solutions and one routing level solution. The MAC solutions are directional NAV indicators which are BRTS, RCTS and HCTS to indicate on-going communications to a directional hidden terminal to set directional NAV. On the other hand, the routing level solution is orthogonal routing protocol (ORP). ORP is a DSR based on-demand routing protocol and it prevents adjacent links to be in straight lines. As computer simulated results, we show that HCTS can improve the throughput performance.