# RARZ: Ring-Zone Based Routing Protocol for Wireless Sensor Networks
## 1 Introduction
Our aim is to realize hierarchical position-based routing that does not need ascertainment of the node positions. This would not only retain the scalability advantage but also bring about energy efficiency, which is usually lacking in the position-based schemes. Moreover, we have eliminated the overhead incurred in terms of control messages exchanged among nodes and BS while selecting CH in the network before each round of communication begins. There have been a variety of proposals (presented in detail in Section 2) for energy-efficient routing in WSNs under various assumptions but specific to the applications. In [7], the BS position is assumed to be fixed and located inside the sensing region. The BS first broadcasts different transmission power messages in the sensing region by dividing it into a different number of rings or tiers. Upon receiving a message, the nodes keep assigning themselves a certain ringID. After successful formation of rings,  
Figure 1: Empirical analysis of hierarchical and flat multihop routing in WSN. the packets are transferred from upper-level rings to lower-level rings on the basis of ring or tier ID. For a message generated in a certain ring, only nodes with lower ringIDs relay the message towards the BS. The nodes in the n-th ring will relay their data to the BS via n hops. All the nodes in the n-th ring share the same network address n, where n is the ringID. One of the drawbacks of the algorithm presented in [7] is that the relaying node (next hop node) is chosen on the basis of a random back-off algorithm that is lacking the node's remaining energy. Therefore, certain nodes may quickly get depleted in energy, by virtue of their positions in the region, resulting in a reduced network lifetime. Another issue in [7] is that the number of hops depends upon the ringID from where the packet has originated. For example, the node in the 7 th ring will relay data to the BS in seven hops. There are situations where the next hop node can be located two hops closer to the BS (the next ring in the direction of the BS). If this situation is exploited, the number of transmissions and hops is reduced and the network lifetime is extended. The proposed algorithm (RARZ) solves both these issues by exploiting the aforementioned scenario and selecting the next hop based on the remaining node energy. RARZ is blind in the sense that packets are sent without ascertaining whether the concerned node will be the next hop node in the path or not. RARZ is table-less, as well as non-position-based, and does location-based routing without the need for the nodes to know their positions. In this paper, we propose a multi-hop Routing Algorithm using Ring Zone (RARZ) model for wireless sensor networks. RARZ reduces the number of hops between the sender and the receiver (i.e., BS) and uses high-level energy sensor nodes along the path for relaying purposes to extend the overall network lifetime. The next hop node is chosen based on its current energy level and the ring in which the node is located. The work described in RARZ is inspired by a well-known protocol named the address-light, integrated MAC and routing protocol (AIMRP) [7]. Our scheme is, however, different in the criteria of next hop selection. This may lead to a further reduction in the number of hops to the destination, \"anywhere\" placement of base station in the network, and minimization of the end-to-end delay and average hop count. The rest of the paper is organized as follows. Section 2 surveys the literature for the work related to the issue at hand. Sections 3 and 4 discuss the proposed protocol description and simulation results in detail, respectively. Section 5 concludes the paper.