WiMax mobile cellular systems are envisioned to provide high data rate multimedia service to users at any time, anywhere at an affordable cost. The WiMAX Forum has proposed the standard 802.16j using relays in order to extend cell coverage at low cost. Moreover, the throughput of the user could be enhanced by using a better link connection. In a previous study, we proposed a Wimax Relay 802.16j model with sectoring technique to enhance the system performance. It resulted in a significant increase in terms of spectrum efficiency and throughput at the base station. However, in that study we assumed that there was no interference between base stations and relay stations and we compared the system of our model to the other models by analysing the system performance in an isolated cell. In this article, the interference from the transmitter stations in the cell and the transmitter stations in the other cells was investigated in order to select the best route from base station to mobile station. Moreover, we consider that the total frequency band allocates dynamically to the sectors in the cell depending on the total data demand in each sector. The simulation result shows that our relay model performs better than the other models for all users' deployment even if the interference is taken into account.