Relay Node Placement in Wireless Sensor Networks With Respect to Delay and Reliability Requirements

Wireless sensor networks are gradually employed in many applications that require reliable and real-time data transmission. As hop count is an important factor affecting end-to-end delay and reliability, we investigate the hop constrained relay node placement (HCRNP) problem in this paper. First, to achieve connectivity requirement, we study the connected HCRNP problem. Then, to design survivable network topologies against node failures, we study the 2-connected HCRNP problem. Correspondingly, two polynomial-time algorithms: cover-based 1-connected node placement (C1NP) and cover-based 2-connected node placement (C2NP) are proposed, respectively, to address the above two problems. Through rigorous analysis, we show that 1) C1NP has an approximation ratio better than existing algorithms for the connected HCRNP problem (i.e., O(1) for special settings and O(<inline-formula><tex-math notation="LaTeX">$\ln n$</tex-math></inline-formula>) for arbitrary settings, where <inline-formula><tex-math notation="LaTeX">$n$</tex-math></inline-formula> is the number of SNs) and 2) C2NP is the first algorithm that can provide an explicit performance guarantee for the 2-connected HCRNP problem, i.e., whenever C2NP finds a feasible solution, the ratio of this solution to the optimal solution is guaranteed to be O(<inline-formula><tex-math notation="LaTeX">$\ln n$</tex-math></inline-formula>). Finally, we verify the effectiveness of the proposed algorithms through extensive simulations.