Research On Delay-aware Energy-saving Mechanism In Hybrid Optical-wireless Broadband Access Networks

A passive optical network(PON)has been widely considered to be a perfect solution to offer high bandwidth and excellent stability.However,PON cannot provide users with anytime-anywhere access services due to its high deployment cost.On the other hand,wireless access networks are flexible and low-cost,but they can only offer very limited bandwidth.The Hybrid Optical-Wireless Broadband Access Network(HOWBAN)combines the merits from the both types of access networks to provide customers with high-capacity,reliable,flexible,and ubiquitous services.In today's society,it is very important to save energy due to the shortage energy.More importantly,access networks contribute to 70% energy consumption of the Information and Communication Technology.This problem is much more severe in HOWBAN because it comprises myriads of access devices that are constantly switched on and off.Therefore,the energy-saving methods are necessary for HOWBAN to reduce the energy consumption.Firstly,the basic concepts and main advantages of HOWBAN are summarized and then the research status is introduced.Later,the necessity of saving energy in the HOWBAN is illustrated.Besides,the key problems and basic principles of several energy-saving strategies in the HOWBAN are emphatically expounded.Secondly,a novel delay-aware adaptive sleep mechanism is proposed to reduce the energy consumption of HOWBAN in this paper.The optimal sleep time of ONU is obtained based on the delay analysis of the optical domain and wireless domain and the maximum delay requirement of packets.Then,the optimal sleep time is updated according to the dynamic changes in the network.The simulation results show that the proposed mechanism reduces the energy consumption effectively and meets the delay requirements of packets well.Thirdly,a delay-aware energy-saving mechanism with adaptive gateway selection is proposed.Based on green dynamic bandwidth allocation and M/G/1 queuing model,the packet delay in the optical domain is mathematically analyzed.Then,the optimal sleep time of ONU is calculated by comprehensively considering the packet delay in wireless domain and the delay requirements of different service classes.Meanwhile,in order to solve the problem of increased downstream packet delay caused by the sleep of ONUs,the downstream packet delays when different gataways are chosed are analyzed.Then,the optimal forwarding gateway is selected.The simulation results show that the proposed mechanism can effectively reduce the energy consumption of the network while satisfying the packet delay requirements.Lastly,the research works are concluded and the future research works are expected.