The ability of Ethernet Ring Protection Switching (ERPS) to provide carrier grade switchover has made Ethernet technology viable in telecommunication carrier networks enabling network operators to replace SONET/SDH/PDH. Adaptive modulation (AM) is another evolution in technology which may effectively double the capacity of microwave links in favorable weather condition. In this paper, we propose an enhancement of ERPS protocol to support adaptive modulation in ERPS protected microwave access network for improved throughput, reliability and energy efficiency. We present a mathematical model to verify the effectiveness of our proposed modification. Simulation results show that the proposed enhancement achieves significantly higher throughput compared to existing ITU-T G.8032 protocol in varying channel conditions.