Yongcheng Li

Adaptive FEC-based lightpath routing and wavelength assignment in WDM optical networks

Forward error correction (FEC) has been widely used in optical communication systems to compensate for the degradation of the received optical signal to noise ratio (OSNR). Current optical networks tend to use the same type of FEC for all the lightpaths even though lightpaths with higher OSNRs can be established by FECs with lower overhead. This paper proposes an adaptive approach to choose the most efficient FECs for different lightpaths based on their individual OSNRs. An Integer Linear Programming (ILP) model and a simple waveplane-based heuristic algorithm considering shuffled lightpath demand sequences are developed to tackle the routing and wavelength assignment (RWA) problem. The simulation results indicate that compared to the non-adaptive case, using the proposed adaptive FEC selection scheme can significantly reduce the required FEC overhead. Apart from being far more tractable, the proposed heuristic approach performs almost as well as the ILP model.

Adaptive FEC selection for lightpaths in elastic optical networks

We propose a new approach to adaptively select FEC types for lightpaths in elastic optical networks. An ILP model and a spectrum-window-based heuristic algorithm are developed to analyze its performance. The proposed FEC selection scheme can achieve good performance with low FEC overhead.

How Much Can Time Domain Hybrid Modulation (TDHM) Help Increase Capacity of Software-Defined Optical Networks?

We apply the time domain hybrid modulation (TDHM) transmission technique to maximize the total capacity of software-defined optical networks. Simulation results show that compared with discrete modulations, the hybrid modulation approach can significantly increase the network capacity by about 40%.

Adaptive Lightpath FEC Selection in an Optical Network

We propose a new adaptive FEC selection scheme to choose different FEC types for each lightpath based on their OSNRs. An ILP model is developed to evaluate the performance in terms of served lightpath demands and required FEC overheads. The proposed scheme can significantly reduce the required FEC overhead compared to the non-adaptive scheme.

Lightpath blocking analysis for optical networks with ROADM intra-node add-drop contention

The contention factor limits the extent to which lightpaths using the same wavelength can be added/dropped in a Reconfigurable Optical Add/Drop Multiplexer (ROADM) when it is operated in a colorless and directionless fashion. This paper presents an analysis to estimate the probability of blocked lightpath requests when a node of this type is used and validates the results for three traffic models. Simulations confirm the validity of the analytical results for lightpath blocking both for various values of the add/drop contention factor C and for changing load distribution in the network. We observe a saturation trend in the lightpath blocking performance as the add/drop port count per bank increases and that a high enough value of C reduces lightpath blocking to levels obtainable from an ideal, comntentionless ROADM. When C is small, limitations on the add/drop port count per bank is observed to be the dominant cause of blocking lightpaths while intra-node contention effects have only a limited impact. With increasing C, blocking is caused more because sufficient link capacity is not available and not because free add/drop ports are not available摘要阻塞因子限制了相同波长光通道在一个无色、 无向 ROADM 上的分/插。 本文提出了一个分析模型来估算在三种通信模型下此类节点的网络阻塞率。 仿真确认了在各种阻塞因子和不同负载分布情况下, 分析模型对网络光通道阻塞率评估的有效性。 研究表明, 随着每一个分/插池中分/插端口数目的增加, 网络光通道阻塞率下降并最终呈现饱和趋势。 同时, 一个足够大的阻塞因子能有效减少光通道阻塞率, 并能接近于最理想的无阻塞 ROADM 节点的性能。 当阻塞因子较小时, 每个分/插池拥有的分/插端口数目将成为光通道阻塞的主要因素, 而节点内部的阻塞性对整体性能的影响有限。 而随着阻塞因子的增大, 网络中链路可用容量将成为光通道阻塞的主要因素, 可用分/插端口数的影响变小。

Hybrid Fiber and Microwave Restoration for Enhancing Availability of Fiber-Wireless Integrated Networks

Availability is a key performance criterion for the emerging Fiber-Wireless (FiWi) access network. To enhance this parameter, we present a flow-splitting restoration strategy, and based on this, develop a Linear Programming (LP) optimization model to maximize mobile user bandwidth availability. Simulations show that the proposed strategy is effective for the FiWi network under different failure scenarios.

Benefit of adaptive FEC in shared backup path protected elastic optical network

We apply an adaptive forward error correction (FEC) allocation strategy to an Elastic Optical Network (EON) operated with shared backup path protection (SBPP). To maximize the protected network capacity that can be carried, an Integer Linear Programing (ILP) model and a spectrum window plane (SWP)-based heuristic algorithm are developed. Simulation results show that the FEC coding overhead required by the adaptive FEC scheme is significantly lower than that needed by a fixed FEC allocation strategy resulting in higher network capacity for the adaptive strategy. The adaptive FEC allocation strategy can also significantly outperform the fixed FEC allocation strategy both in terms of the spare capacity redundancy and the average FEC coding overhead needed per optical channel. The proposed heuristic algorithm is efficient and not only performs closer to the ILP model but also does much better than the shortest-path algorithm.