Recently, OMIPv6 series, based on public-key cryptography, have been proposed to improve RR protocol. This series no typically composed of the initial and subsequent phases. In the initial phase, the mobile node and its corresponding node build a strong long-term key, by which successive binding updates are optimized in the subsequent phase. In this paper, we compare and analyze the subsequent phases of OMIPv6 series in terms of performance, security and applicability, then presenting an improvement on the subsequent phase. Also, we show that the proposed improvement is reasonable considering performance, security and applicability overall.