Routing Protocol for LEO Satellites

The routing protocol discussed is the satellite grouping and routing protocol (SGRP) for low earth orbit (LEO) and middle earth orbit (MEO) satellite IP networks. SGRP routing protocol offers a solution for space based networking for satellites designed to transmit packets in minimum-delay path and distribute the routing table to other satellites from low earth orbit (LEO) to middle earth orbit (MEO) (Chen, 2005). An advantage to this protocol is the physical separation of the LEO and MEO computational routing tasks that benefit power savings, efficient use of bandwidth, and management of routing congestion. In recent years, LEO satellites have become more popular due to its low cost and possible applications for environment, GPS, imagery, and telecommunications. Companies such as SpaceX and OneWeb companies have had announced ventures of Internet in space (Kellenher, 2017). The social benefit is ubiquitous Internet here on earth and in space especially as Internet of things (IOT) is becoming more popular. Moreover, I see an opportunity for security as these cubesats offer a unique network that could be used for critical infrastructure.

Routing Protocol for LEO Satellites

In this discussion, a routing protocol not detailed in the book is to be explored. This routing protocol is satellite grouping and routing protocol (SGRP) for low earth orbit (LEO) and middle earth orbit (MEO) satellite IP networks. In recent years, LEO satellites have become more popular due to its low cost and possible applications for environment, GPS, imagery, and telecommunications. However, space based networking services in industries such as telecommunications offers some unique challenges.

Routing Problem in Space

As Internet-based applications pushes into broad-band satellites, expensive geosynchronous equatorial orbit (GEO) satellites sits high in orbit above the earth relaying telecommunications to ground based terminals. In contrast, smaller LEO and MEO satellites in a low orbit, offers opportunities for unique Internet-based applications but with some challenges due to the constantly moving satellite. This difference between GEO and LEO/MEO offers unique routing and communications challenges. Internet protocol TCP/IP is great for terrestrial routing, however the delays and propagation time of transmission between routing nodes with satellites is slow effecting quality of service (QOS). To address this issue, a routing protocol, satellite grouping and routing protocol (SGRP), was designed for low earth orbit (LEO) and middle earth orbit (MEO) routing network.

Satellite Grouping and Routing Protocol (SGRP)

Satellite grouping and routing protocol (SGRP) was designed to transmit packets in minimum-delay path and distribute the routing table to other satellites from low earth orbit (LEO) to middle earth orbit (MEO) (Chen, 2005). These groups of satellites have the capability to collect and exchange the link delay information of the LEO layer and then transmit that information to MEO satellites which distributes the routing information such as packet routing and forwarding. This network architecture of LEO and MEO satellites offers good network management between space orbits and terrestrial gateway stations.

The SGRP routing schemes assume a connection-oriented network structure, dynamic routing tables along with a discrete time network model in a satellite over satellite (SOS) architecture, and IP traffic. There are three types of duplex links in this network that is inter-satellite links (ISL), inter-orbital links (IOL), and user data link (UDL). ISL is the communications within the same layer of satellites connected to their immediate neighbors. IOL is the communication between MEO and LEO satellites. UDL is a terrestrial gateway where LEO satellites communicate. These delay metrics are used in the route computation which is the sum of the processing, queuing, and transmission delays in the satellites and propagation delays on the ISL. MEO satellites calculate the routing tables and by managing transmitted and stored tables to LEO satellites (Chen, 2005).

SGRP Routing Protocol Advantages

Congestion in routing typically results from the overflowing of router buffers as the networking becomes congested (Kurose, 2009). This physical separation of the LEO and MEO computational routing task saves power and maximizes the efficient use of bandwidth, thereby solving the routing problem of congestion. The results from this SGRP congestion control simulations between SGRP and datagram routing algorithm (DRA) and shortest path algorithms is that DRA was 13% higher in congestion than that of the path calculated by SGRP. The calculations performed between shortest path algorithms and SGRP was about the same (Chen, 2002).

Summary

Due the increased interest of low cost LEO satellites and the rapid growth of Internet-based applications pushes satellite networks to carry IP traffic. SGRP routing protocol offers a solution to space based networking for satellites designed to transmit packets in minimum-delay path and distribute the routing table to other satellites from low earth orbit (LEO) to middle earth orbit (MEO) (Chen, 2005). An advantage to this protocol to this physical separation of the LEO and MEO computational routing task is power savings and the efficient use of bandwidth, thereby solving the routing problem of congestion.