Avoidance of hidden terminal problems in cluster-based wireless networks using efficient two-level code assignment schemes

To enhance throughput and reuse bandwidth. clustering techniques can effect ively manage nodes in multi-hop wireless networks. However. in such network s, hidden terminal interference degrades the system performance and increas es the average packet delay time. Therefore, this work presents novel two-l evel cluster-based code assignment techniques to resolve the hidden termina l problems. At the low lever, five basic and an optimized intra-cluster cod e assignment schemes are developed to calculate the number of codes used in each cluster. At the high level? two inter-cluster code assignment schemes (coarse-grained and fine-grained controls) are proposed to obtain the mini mal number of code sets. The merits of our schemes include low execution ti me? low probability of code re-assignment I and low overhead. Furthermore, the proposed schemes allow us to regionally update orthogonal codes when th e topology varies. Experimental results demonstrate that the proposed schem es outperform conventional techniques. Among the five basic intra-cluster c ode assignment schemes, the ordering criteria of increasing number of one-h op neighbors is the best in terms of the number of orthogonal codes to avoi d hidden terminal interference. The optimized intra-cluster code assignment scheme generally obtains fewer orthogonal codes than other schemes. For in ter-cluster code assignment schemes, the coarse-grained control has a lower code allocation time. However. the fine-grained control requires fewer ort hogonal codes.