This paper mainly explores interference of multi-hop ad-hoc networks for two cases of antennas in two dimensional areas. We make a comparison of omni-directional antenna which radiates power in one plane with directional antenna using beamforming or sectoring technique, and calculate interference and carrier to interference ratio (C/I) for both cases. Subsequently, we show that using directional antennas drastically decreases interference, and thus increases carrier to interference ratio (C/I). Our model has proposed a regular lattice for possible locations of mobile nodes. This enables us to calculate the expected value of C/I, without having detailed information about movement patterns and exact location of all nodes at any moment. Based on the model, we have reckoned effects of variation in the network size, network density and traffic load on C/I. We have also calculated an upper bound for the interference that use carrier sensing for medium access control (MAC).