Research On Layered Cross-Domain Optimization For OFDM Optical Networks

With the continuous growing of Internet scale and applications,the hungry for the bandwidth becomes increasingly dramatic,especially under urgent circumstances of saturated network resources,thus making the problem about efficient infrastructure utilization necessarily becomes operators’ focus.By using Orthogonal Frequency Division Multiplexing(OFDM),multiple orthogonal subcarriers enjoy parallel transmission,leading to higher spectrum efficiency and color/polarization dispersion resistance in OFDM optical networks.In accordance with the ’cross-domain’ principle,the optical OFDM can be applied to two main aspects:1)the next-generation high-speed elasitic optical backbone network(OFDM-EON)and the next-generation elastic passive optical access network(OFDM-PON).In the network layer of OFDM-EON,the appropriate amount of continuous spectrum slots is allocated for the user demand without the limitation brought by traditional Wavelength Division Multiplexing(WDM)where the fixed guardband is configured among channels,thus mitigating the granularity mismatch between the actual bandwidth requirement and channel provisioning.In the physical layer of OFDM-PON,a novel mode supporting fiber access will own advantages of high spectrum efficiency and color/polarization dispersion,as well as low hardware deployement complexity.Though there have been researches focusing on the key technologies in terms of optical backbone or access domain,their solutions cannot be directly applied to OFDM optical networks that have unique architecture and traffic characterisitcs.It becomes very urgent to design novel schemes for OFDM optical networks with the consideration of flexible modulation and diverse requirements for service qulatiy.Moreover,the existing studies still remain in the single-layer or individual domain,but the layered and cross-domain optimization mechanisms develop in the initial stage where many problems are waiting to be solved.In summary,the research on the inter-layer,and cross-domain optimization mechanisms has potential academic significance and application value for OFDM optical networks.The main contributions and innovative results are summarized in the following.(1)Research on algorithms supporting adaptive routing and spectrum assignment in OFDM-EONs.Firstly,a novel spectrum slice auxialiry graph is proposed and we then design the algorithm applied to the routing and spectrum assignment in OFDM-EONs based on the graph.Our algorithm utilizes shortest path to perform routing while first-fit method for spectrum allocation.Finally,the idea of waveband switching together with adaptive modulation is also taken into account for the algorithsm design.(2)Research on elastic waveband switching algorithms based on Markov prediction and time division multiplexing in OFDM-EONs.We design a novel routing and spectrum assignment based on time division multiplexing with the joint consideration of adaptive modulation and waveband grooming.According to the availability of currnt network resources by predicting the future possible occupation through Markov chan,the routing and spectrum allocation is conducted for the traffic,thus reducing the network blocking probability.(3)Research on algorithms of channel estimation in OFDM-PONs.To overcome the drawback of traditional Discrete Fourier Transform(DFT)-based channel estimiation,e.g.,to avoid the generation of additional high-frequency information caused by running Inverse DFT for the original discontinuous sequence,an identified algorithm is proposed.The optimized DFT algorithm together with avelet denoising effectively filters the noise of available paths.(4)Research on software-defined reconfigurable transmission mechanisms in OFDM-PONs.In the physical layer of OFDM-PONs,the function of Software-Defined Network(SDN)is also applied,and we construct the corresponding software-defined reconfigurable data transmiion platform,in order to achieve the flexible switchover of different tranmission modulars.To demonsrate and evaluate the performance of proposed algorithm and plateform,we utilize OptiSystem,MATLAB,C++and Python to establish simulation systems.The simulation results show that the proposed algorithm and plateform are effective in terms of saving optical switching ports,reduing network blocking probability,lowering erro bit rate and improving network scalability.The aforementioned meaningful research results can provide theory basis and technical support for the development of OFDM optical networks.