Unmanned Systems Technology 038 l Skyeton Raybird-3 l Data storage l Sea-Kit X-Class USV l USVs insight l Spectronik PEM fuel cells l Blue White Robotics UVIO l Antennas l AUVSI Xponential Virtual 2021 report

8 Platform one Real-Time Innovations (RTI) has updated its software framework to support autonomous systems such as robots and driverless cars that require low latency and determinism (writes Nick Flaherty). Connext 6.1 is the first software framework designed to address the development and deployment challenges faced by companies building remotely operated autonomous systems. It uses a Distributed Data System (DDS) with a publish-subscribe architecture. That allows systems to scale but has suffered from issues with latency, especially when using unstable wireless links. Connectivity for distributed control is extremely challenging. Applications require high reliability and real-time performance, even though connectivity in harsh environments is often unreliable and low in bandwidth. The comms links can span local, wide-area, public and private networks.  Connext 6.1 adds support for real-time remote operation over any network with seamless connections without losing information. This real-time wide-area network (WAN) transport function is fully integrated with the rest of the Connext software framework, and applications can use all the features available over a LAN when communicating over the WAN. The lower latency is achieved by using the User Datagram Protocol (UDP) to communicate over the internet instead of the more typical Transmission Control Protocol (TCP). TCP has built-in buffering and reliability, but there is no way to control latency for different data flows. On top of UDP, Connext implements an optimised version of the DDS reliability protocol, including prioritisation of data flows and different delivery policies such as best-effort, reliable and keep last delivery. This tailors the performance of the framework based on the latency requirements of each data flow in a system. For example, applications will acknowledge and resend lost low-latency data such as control signals more quickly than less latency-sensitive information such as device status. “The WAN transport feature is one of the fastest and easiest ways to achieve peer- to-peer UDP WAN comms, especially for projects already using RTI Connext DDS but also for those using other middleware or even starting from scratch,” said Charles Cross, CTO at Mission Robotics, which uses the software. “We were able to create a proof of concept from scratch that allowed us to remotely control and monitor a robot over the internet in only 3 hours.” Connext 6.1 also has a fine-grained security model, whereby the security overhead can be controlled per data flow as opposed to per connection. This means the security overhead that increases latency can be controlled for each data flow based on its requirements.  With the publish-subscribe architecture, applications communicate from peer to peer, and data is not routed or relayed by intermediate brokers or servers. Connext uses a ‘cloud discovery service’ rather than network address translation to support mobile applications with changing internet addresses. This only brokers discovery at start-up time, and data exchange takes place in a peer-to-peer manner. This simplifies deployment of dynamic systems in which applications, assets and their network addresses may not be known at configuration time. It provides a means for applications to discover each other and communicate directly. That minimises latency and maximises throughput. Built-in data compression in Connext 6.1 also improves efficiency over bandwidth-constrained networks, and lowers the overhead and latency while increasing throughput. A choice of compression algorithms and levels allows optimisation of processor versus network utilisation for different payload types. Support for .NET Core 5 lets developers use C# and run their applications on any platform that supports .NET Standard 2.0. In addition to Windows, this includes Linux, macOS and the Unity game engine. Comms June/July 2021 | Unmanned Systems Technology DDS software update The latest version of the Connext DDS framework adds real-time deterministic comms