Zhenqian Feng

OpenSAN: a software-defined satellite network architecture

In recent years, with the rapid development of satellite technology including On Board Processing (OBP) and Inter Satellite Link (ISL), satellite network devices such as space IP routers have been experimentally carried in space. However, there are many difficulties to build a future satellite network with current terrestrial Internet technologies due to the distinguished space features, such as the severely limited resources, remote hardware/software upgrade in space. In this paper, we propose OpenSAN, a novel architecture of software-defined satellite network. By decoupling the data plane and control plane, OpenSAN provides satellite network with high efficiency, fine-grained control, as well as flexibility to support future advanced network technology. Moreover, we also discuss some practical challenges in the deployment of OpenSAN.

Software defined satellite networks: Benefits and challenges

To date, traditional satellite systems are contained-designed and inflexible for configuration update, space systems interconnections and providing fine-grained services. In this paper, we propose a novel satellite network architecture: software defined satellite networks (SDSN) to solve these problems. The new architecture is based on the central control patten of software defined networks (SDN), and takes full use of the inter-satellite links (ISLs) forwarding and GEO broadcasting for rapid network deployment. With global network view and central control ability, SDSN can (1) balance the flexibility and controllability of space dynamic routing algorithms, (2) rapidly deploy flexible and fine-grained network management strategies, (3) reduce the system cost, and (4) improve the collaboration between satellites and the compatibility of heterogeneous space systems. Meanwhile, the challenges are also introduced in designing and deploying the new architecture. Finally, the performance of the new SDSN architecture is validated in this paper.

MSN: a mobility-enhanced satellite network architecture: poster

The proposed MSN architecture is intended to directly address the challenge of mobility, which refers to the motion of users as well as the dynamics of the satellite constellation. A virtual access point layer consisting of fixed virtual satellite network attachment points is superimposed over the physical topology in order to hide the mobility of satellites from the mobile endpoints. Then the MSN enhances endpoint mobility by a clean separation of identity and logical network location through an identity-to-location resolution service, and taking full advantage of the users geographical location information. Moreover, a SDN based implementation is presented to further illustrate the proposal.

NCSR: Multicast transport of BGP for geostationary Satellite network based on Network Coding

To integrate the satellite systems into the terrestrial IP network, border gateway protocol BGP is considered as a promising candidate. Taking advantage of wireless broadcast property could significantly improve the bandwidth occupation of BGP routing transport in GEO satellite network. However, its performance would be seriously degraded when interfered with the environment. This paper proposes NCSR (Network Coding for Satellite network BGP Routing transport) which applies network coding to multicast transport of BGP in GEO satellite network. NCSR exploits the broadcasting feature and achieves reliable multicast transport of BGP over the lossy space links. Representative mechanisms in transport layer are chosen to evaluate bandwidth improvement in typical scenario of DVB-S2/RCS. Through theoretical analysis and extensive simulations, we compared NCSR with other existing proposals. Results show that NCSR can not only tolerate more packet losses, but also significantly reduce more bandwidth cost of BGP. Moreover, the benefits of NCSR increase sharply with the number of participated ground terminals and the rate of packet loss.

Improving the snapshot routing performance through reassigning the inter-satellite links

This paper presents an inter-satellite link (ISL) reassignment method to optimize the snapshot routing performance for the polar-orbit LEO (low Earth orbit) satellite networks. When the snapshot routing tables are switching in all satellites, we propose to reassign the inter-plane ISLs regularly to improve the quality of the next snapshot. Evaluations indicate that our method can obtain equal-length snapshots regardless of the latitude of polar border, which is superior to the natural partition method. Meanwhile, compared with the equal partition method which is practically used in Iridium system, our method can prolong 82.87% snapshot duration, increase 8.68% inter-plane ISL utility ratio and averagely reduce the delay of 54.57% end to end paths. We believe that our method could be practically and effectively applied in the Iridium-NEXT system.

Improving Availability through Energy-Saving Optimization in LEO Satellite Networks

Recently, satellite networks are widely used for communication in areas lack of network infrastructures, and will act as the backbones in the next generation internet. Therefore, the availability of satellite networks is very important. In space, the energy is always limited for satellites, and highly efficient energy utilization would certainly improve the availability of satellite systems. In this paper, we consider the energy-saving optimization for the LEO satellite network instead of a single satellite. We modify and extend the multicommodity flow model [3] to switch off satellite nodes and links as much as possible in LEO satellite networks. Taking advantage of the multi-coverage scheme and traffic distribution patents in satellite networks, we improve the heuristic algorithms in [3] to turn off the unnecessary satellites, up-down links and inter-satellite links respectively up to 59 %, 61 % and 72 % under the constraints of link utilization and routing hops increase ratio, and the total energy saving ratio can be up to 65 %. Finally, the availability of LEO satellite networks has been deeply developed.

Distributed mobility management in IP/LEO satellite networks

By virtue of low end-to-end delay, the Low Earth Orbit (LEO) satellite network shows notable advantages in providing network services in global range. However, the high mobility of satellites leads to the constant changing location for terminals, which brings great challenges to the mobility management in LEO satellite networks. Existing mobility management schemes in satellite networks mainly borrow the idea from IP mobility solutions, such as MIP, MIPv6. Nevertheless, these schemes are all based on the centralized management architecture, which has exposed many defects in the terrestrial network, such as the scalability and performance problems. To eliminate these limitations, the Distributed Mobility Management (DMM) is proposed by deploying the distributed anchors to handle the traffic from mobile terminals. Currently, the feasibility of DMM in satellite networks has not been studied. In this paper, we present DIPS, a DMM based IPv6 mobility solution in LEO satellite networks. DIPS highlights a distributed location management architecture based on terrestrial gateways. To identify the merits and shortages, we make a comparison between the typical centralized scheme and DIPS. The theoretical analysis is presented to evaluate the performance on management cost. After that, the simulation with NS2.35 in the scenario of the Iridium system is conducted. Simulation results show that DIPS is an efficient scheme with preferable scalability in both management cost and latency.

Poster: Avoiding Rollback Traffic during the Switch of Snapshot Routing in Cyclic Mobile Networks

In this paper, we propose a rollback traffic avoidance method for the snapshot routing in cyclic mobile networks. Since the snapshot routing tables are switched simultaneously, part of the traffic may be sent back on some links if the new routing path contains the same links but with reversed forwarding direction against the old one. Since the selection of routing paths to avoid the rollback traffic is NP-hard, we propose an approximate algorithm called Inter-Snapshot Rollback Traffic Avoidance (ISRTA), to pursuit the approximate optimal solutions. Evaluation is performed based on the typical cyclic mobile network -- Iridium satellite system, and the simulation results show that our method can efficiently eliminate the rollback paths and traffic in the Iridium system.

NC-STP: A High Performance Network Coding Based Space Transport Protocol

Because of the long propagation delay and high PERs in space links, a proper transport protocol is required to transmit data reliably and effectively in space networks. To meet that demand, the Delay/Disruption Tolerant Network (DTN) is proposed, which calls for new designed principles in order to achieve efficient and reliable communication between DTN peers. In this paper, we propose a novel Network Coding based Space Transport Protocol (NC-STP) as a transport scheme for the space network. The NC-STP combines the advantages of auto retransmission and network coding, while at the same time keeps its controlling mechanism very simple. Known from other solutions, NC-STP retransmits the line combination of original packets instead of the original packets themselves and can transmit files in a continuous manner. We evaluate the performance of NC-STP both theoretically and experimentally. The results reveal that NC-STP can achieve better performance than DSTP.

GRIMM: A Locator/Identifier Split-Based Mobility Management Architecture for LEO Satellite Network

As a complement part of terrestrial networks, Low Earth Orbit (LEO) satellite network plays an important role in providing network services for its low end-to-end delay and efficient frequency spectrum utilization. However, the frequent handover occurrences of Ground-Satellite Links (GSLs) pose great challenges on the mobility management in LEO satellite network. Due to the differences between satellite and terrestrial network in topology, processing power and links, the application of current IP mobility solutions to satellite network has some drawbacks which leads to the non-optimal routing. Base on a comprehensive analysis on the limitations of current IP mobility solutions in satellite network, this paper proposes GRIMM, a gateway based regional mobility management architecture for satellite network based on Locator/Identifier split. The coverage of the satellite system is divided into regions according to the distribution of terrestrial gateways. Each gateway realizes a localized location management for terminals within respective region, and global location management is achieved through the synchronization among all gateways. GRIMM avoids the non-optimal routing and achieves efficiency. Both theoretical analysis and simulation results show that the proposed mobility management architecture can achieve a greatly reduced management cost on Inter-Satellite Links (ISLs) while keeping comparable latency in transmission.