Rentao Gu

Baseband unit cloud interconnection enabled by flexible grid optical networks with software defined elasticity

The evolution toward 5G mobile networks is characterized by supporting higher data rate, excellent end-to-end performance and ubiquitous user-coverage with lower latency, power consumption, and cost. To support this, the RANs are evolving in two important aspects. One aspect is “cloudification,” which is to pool baseband units to be centralized for statistical multiplexing gain. The other aspect is to use advanced optical technologies for digital and analog signal transmission in a cloud-based RAN. In this article, we focus on BBU cloud interconnection with optical layer technologies. Flexible grid optical networks with the enabling technologies are introduced to provide elastic, transparent, and virtualized optical paths between the BBU pools. To improve the elasticity and intelligence of C-RAN, we propose a software defined centralized control plane to coordinate heterogeneous resources from three domains: the BBU domain, radio domain, and optical domain. We report an experimental demonstration of elastic lightpath provision for cloud radio-over-flexible grid optical networks in a software-defined-networking-based testbed.

Dynamic virtual network embedding over multilayer optical networks

Network virtualization is meant to improve the efficiency of network infrastructure by sharing a physical substrate network among multiple virtual networks. Virtual network embedding (VNE) determines how to map a virtual network request onto a physical substrate. In this paper, we first overview three possible underlying substrates for interdatacenter networks, namely an electrical-layer-based substrate, an optical-layer-based substrate, and a multilayer-based (optical and electrical layer) substrate. Then, the corresponding VNE problems for the three physical substrates are discussed. The work presented focuses on VNE over a multilayer optical network; a key problem is how to map a virtual network request onto either an electrical or optical substrate. We propose an auxiliary graph model to address multilayer virtual network mapping in a dynamic traffic scenario. Different node-mapping and link-mapping policies can be achieved by adjusting weights of the edges of the auxiliary graph, which depends on the purposes of the network operators.

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。

Dynamic bandwidth allocation algorithm for next-generation time division multiplexing passive optical networks with network coding

Abstract. An efficient dynamic bandwidth allocation (DBA) algorithm for multiclass services called MSDBA is proposed for next-generation time division multiplexing (TDM) passive optical networks with network coding (NC-PON). In MSDBA, a DBA cycle is divided into two subcycles with different coding strategies for differentiated classes of services, and the transmission time of the first subcycle overlaps with the bandwidth allocation calculation time at the optical line terminal. Moreover, according to the quality-of-service (QoS) requirements of services, different scheduling and bandwidth allocation schemes are applied to coded or uncoded services in the corresponding subcycle. Numerical analyses and simulations for performance evaluation are performed in 10 Gbps ethernet passive optical networks (10G EPON), which is a standardized solution for next-generation EPON. Evaluation results show that compared with the existing two DBA algorithms deployed in TDM NC-PON, MSDBA not only demonstrates better performance in delay and QoS support for all classes of services but also achieves the maximum end-to-end delay fairness between coded and uncoded lower-class services and guarantees the end-to-end delay bound and fixed polling order of high-class services by sacrificing their end-to-end delay fairness for compromise.

Early traffic identification using Bayesian networks

Port-based or payload-based analysis is becoming difficult for accurate traffic identification when many applications use dynamic port numbers and encryption to avoid detection. In this paper we present an approach for online traffic classification relying on the observation of the first n packets of a flow. The packet size and inter-arrival times of the individual packets, rather than the statistic features, are chosen as identification parameters. We use labeled data set as training set to construct a Naïve Bayes classifier and use the real discretized conditional probability instead of Gaussian distribution. Two real data sets collected in the campus networks are used to evaluate the proposed approach and the effectiveness is proved. The results also indicate that this approach is not sensitive to the prior probability estimation in most cases, and that packet sizes are more efficient than the inter-arrival times although both of them are important.

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.

Sign Inference for Dynamic Signed Networks via Dictionary Learning

Mobile online social network (mOSN) is a burgeoning research area. However, most existing works referring to mOSNs deal with static network structures and simply encode whether relationships among entities exist or not. In contrast, relationships in signed mOSNs can be positive or negative and may be changed with time and locations. Applying certain global characteristics of social balance, in this paper, we aim to infer the unknown relationships in dynamic signed mOSNs and formulate this sign inference problem as a low-rank matrix estimation problem. Specifically, motivated by the Singular Value Thresholding (SVT) algorithm, a compact dictionary is selected from the observed dataset. Based on this compact dictionary, the relationships in the dynamic signed mOSNs are estimated via solving the formulated problem. Furthermore, the estimation accuracy is improved by employing a dictionary self-updating mechanism.

Resource allocation optimization for time and wavelength division multiplexing passive optical network enabled mobile fronthaul with bitrate-variable compressed common public radio interface

Recently, a cloud radio access network (C-RAN) has been proposed as a candidate architecture for fifth-generation mobile communication. Fronthaul is a new segment in C-RAN. In this paper, we investigate the algorithms for resource allocation in time and wavelength division multiplexing passive optical network enabled front-haul. We formulate an integer nonlinear programming (INLP) model, considering the operation mode of the small cell. A heuristic method is also proposed based on an adaptive parallel genetic algorithm (GA). Three optimization objectives are considered when we implement the resource allocation schemes in the fronthaul: 1) minimize the total number of used wavelengths, 2) minimize the load imbalance of the fronthaul, and 3) minimize the amount of traffic influenced by fronthaul virtual topology change. The results show that INLP and adaptive parallel GA have good performance for resource allocation in the fronthaul. Wavelength resources can be significantly saved in different load scenarios, so that the load difference can be minimized with minimal topology adjustment. Furthermore, the adaptive parallel GA obtains more efficient resource allocation than the traditional GA with much less running time, which makes it applicable for the large-scale fronthaul network optimization with fast convergence.

Demonstration of BGP Interworking in Hybrid SPTN/IP Networks

This paper proposes BGP interworking and inter-communication architecture and mechanisms for hybrid SPTN/IP, and the extended Ryu based controllers realize BGP information sharing between SPTN network islands and IP networks in a multi-domain testbed.

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.