Green Protocol For Hybrid Optical-Wireless Broadband Access Networks (HOWBAN)

Currently, Internet has become an important tool for people's study, work and life. People's demand for broadband access to Internet is increasing day by day. Optical access and wireless access are two effective last-mile solutions. In this context, Hybrid Optical-Wireless Broadband Access Networks (HOWBAN) emerges, which combines the advantages of the two access networks.Due to the energy shortage in today's society, energy conservation has become increasingly important, and the slogan of energy-saving has never stopped. Therefore, how to design green protocols to save energy is one of the important topics in HOWBAN. With the development of HOWBAN, the network size is increasing, and the problem of risk control presents formidable challenges to routing protocol design. This paper focuses on these two problems, and proposes a routing protocol called Risk and Energy Aware Routing Algorithm (REAR).Firstly, the paper introduces the basic concepts of HOWBAN and main advantages, investigates the popular protocols and energy-saving strategies, and compares their performance. Then, we combines energy-saving strategies and RADAR, proposes an improved protocol, called REAR. We simulate this novel protocol and verify its effectiveness. There is no energy-saving control in RADAR. So, all of the ONU are active, and this wastes energy. The common energy-saving protocol can save energy by shut down some ONUs, but it assume in a good network condition. However, if the ONU is failure, a lot of packets will be lost. To compensate for these shortcomings, our proposal, called REAR, based on the architecture of HOWBAN, combines ONU's sleeping control and risk list. The protocol maintains a Risk List (RL) table in each routers, which contains seven fields, including path status (PS) (live or stale) and ONU status (OS) (active or sleep). Among paths in RL, it just chooses the live and active path. Finally, in different traffic scenarios, we simulate the performances of RADAR, EARA and REAR. Simulation results show that REAR has an steady packet loss and its energy-saving is better than EARA.