The most widely used standard for wireless networks is the IEEE 802.11. In 802.11, dense deployment of Access Points (APs) is needed to meet customers' demands. The installation of multiple access points is expensive and not convenient because of Ethernet wiring from access points to backhaul network access modem, hub, etc. Wireless mesh network (WMN) is an emerging technology; presented mainly as the solution to the problem related to the necessity to create a wireless distribution system (APs need to interconnect wirelessly). It is expected to replace the wireline infrastructure network due to the scalability and rapid cost effective deployment and maintenance. One of the WMN applications is that they can be used as a backbone. The characteristics of self-organization and auto-configuration in the wireless mesh backbone offer many benefits such as low upfront investment, increased reliability and scalability. In this Paper, we are interested, to the using of directional antennas in wireless mesh backbone. By using this kind of antenna in wireless mesh backbone we can improve the performance and QoS. The directional antenna allow to improve the spatial reuse of the wireless channel, which allows nodes to communicate simultaneously without interference, and potentially establish links between nodes far away from each other, and the number of routing hops can be fewer than that of omnidirectional antennas. We also propose a new amendment to reduce the routing overhead related to the use of multiple interfaces.