Shizong Zhang

Dual-layer efficiency enhancement for future passive optical network

Ever-increasing demands on bandwidth compel us to improve the bandwidth utilization of access networks. It is more important to enhance the efficiency of passive optical networks (PON) than other access technologies, as they are the primary solutions to various access scenarios. To satisfy the demands of improved bandwidth efficiency, we propose a dual-layer (data link layer and network layer) efficiency enhancement scheme for future PON system. Under this architecture, a data-link-layer flexible coding scheme is introduced to extend the downstream link throughput, and a network-layer centralized active queue management (AQM) scheme is introduced to increase bandwidth efficiency. Both of these technologies are designed to suit the future centralized cooperative control mode. The results of an experimental demonstration of the network coding PON scheme reveal the efficiency of the proposed architecture. The results of simulations show that the centralized AQM scheme has a positive influence on queuing delay and jitter. To the best of our knowledge, this is the first time that a data link layer mechanism and a network layer policy have been integrated to provide high efficiency and quality of service in access networks.创新点本文首次针对无源光网络(PON)提出了集中控制下的双层(数据链路层和网络层)效率提升机制。该机制在数据链路层引入了可变光分配网(ODN)的灵活网络编码的同时,在网络层引入了集中式主动队列管理(AQM)切换方案,以增加PON系统下行链路吞吐量、降低网络延迟和抖动。实验测试表明,该系统可提升下行带宽吞吐量近40%,同时增强了排队管理效果的稳定性。所提出方案能够在接入侧实现高效的数据流量压缩和流量疏导,将可用于满足未来接入网集中管控与高效传输需求。

Software defined flexible and efficient passive optical networks for intra-datacenter communications

Abstract Facing the huge traffic challenge, optical networking shows great advantages on capacity and energy issues. However, the efficiency and flexibility are not satisfactory to the data center networks, especially for intra-datacenter communications. This article reviews the typical architectures of data center networks, and suggests that TWDM-PON system can be used in the edge layer and aggregation layer in the datacenter networks. It proposes a software defined flexible and efficient passive optical network, combining the software defined technology and network coding, for intra-datacenter communications. Network coding is applied to increase the downstream bandwidth efficiency and overcome network bottleneck, and software defined technology provides the flexibility on wavelength assignment according to traffic statistics dynamically. To increase more efficiency, a seamless DBA (S-DBA) scheme and an ONU grouping algorithm are proposed to fully utilize the upstream idle time and minimize the traffic entering into the core layer of the datacenter networks. They realize flexible scheduling and resource allocation both in time domain and wavelength domain. The experimental simulations indicate that the proposed schemes and algorithms provide low delay, good fairness, increased efficiency and network flexibility.

Experimental evaluation of software defined passive optical network with network coding

Facing with the huge P2P traffic challenge, network coding shows great advantages in improving system efficiency. This paper proposed a solution to integrate network coding into passive optical networks and compatible with the existing Ethernet passive optical network named NC-PON. To increase more efficiency, a software defined passive optical networks with network coding (SDNC-PON), which combines the software defined technology and network coding, was proposed to optimize the P2P traffic under different OLTs. The core idea of SDNC-PON is to change the owner-member relationship between OLTs and ONUs flexibly to achieve the maximum traffic benefit. The results of experimental platform and the simulations indicated that the proposed architecture is efficient and with network flexibility.

Network slicing and efficient ONU migration for reliable communications in converged vehicular and fixed access network

Abstract Rapidly increased bandwidth of vehicle communication brings challenges on its infrastructure, especially for V2R/V2I scenarios. On the other hand, the costs and energy consumption asks for the network convergence among fixed access, roadside assistant vehicle network and even mobile networks. Therefore, flow interaction in the converged network threatens the reliability and safety of vehicle services. This paper proposes a flexible vehicle and fixed access converged network architecture and elastic slice-enabling scheme, to provide reliable vehicle communication service from the infrastructure level. In this architecture, optical network units (ONUs) are capable to be migrated flexibly between different optical line terminals (OLTs) to improve the bandwidth utilization of idle OLTs. Meanwhile, while taking into account the impact on network quality—ONU switching times and transmission distance, a flexible ONU migration algorithm (OMA) is proposed to maximize bandwidth resource utilization. The cross-region demonstration proves the feasibility of the proposed slicing mechanism, and the simulation results indicates that the bandwidth utilization ratio increases by 15% in the simulations circumstances.

Software defined multi-OLT passive optical network for flexible traffic allocation

With the rapid growth of 4G mobile network and vehicular network services，mobile terminal users have increasing demand on data sharing among different radio remote units (RRUs) and roadside units (RSUs). Meanwhile, commercial video-streaming, video/voice conference applications delivered through peer-to-peer (P2P) technology are still keep on stimulating the sharp increment of bandwidth demand in both business and residential subscribers. However, a significant issue is that, although wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) technology have been proposed to fulfil the ever-increasing bandwidth demand in access network, the bandwidth of optical fiber is not unlimited due to the restriction of optical component properties and modulation/demodulation technology, and blindly increase the wavelength cannot meet the cost-sensitive characteristic of the access network. In this paper, we propose a software defined multi-OLT PON architecture to support efficient scheduling of access network traffic. By introducing software defined networking technology and wavelength selective switch into TWDM PON system in central office, multiple OLTs can be considered as a bandwidth resource pool and support flexible traffic allocation for optical network units (ONUs). Moreover, under the configuration of the control plane, ONUs have the capability of changing affiliation between different OLTs under different traffic situations, thus the inter-OLT traffic can be localized and the data exchange pressure of the core network can be released. Considering this architecture is designed to be maximum following the TWDM PON specification, the existing optical distribution network (ODN) investment can be saved and conventional EPON/GPON equipment can be compatible with the proposed architecture. What’s more, based on this architecture, we propose a dynamic wavelength scheduling algorithm, which can be deployed as an application on control plane and achieve effective scheduling OLT wavelength resources between different OLTs based on various traffic situation. Simulation results show that, by using the scheduling algorithm, network traffic between different OLTs can be optimized effectively, and the wavelength utilization of the multi-OLT system can be improved due to the flexible wavelength scheduling.