Data Distribution Service Specification Research Articles

Reliable Middleware for Wireless Sensor-Actuator Networks

Many important and critical applications use wireless sensor/actuator networks (WSAN). These applications are spanning widely that range in several environments, including industrial, commercial, and residential. Most of these applications need a certain level of real-time communication in addition to reliable data delivery service. Data distribution service (DDS) is a known standard for supporting real-time distributed systems based on the publish/subscribe model. The DDS specification offers two disparate quality-of-service levels of data reliability, namely: best-effort and fully-reliable. TinyDDS is a lightweight and partial porting of DDS middleware to sensor-based platforms, specifically for platforms with limited resources. However, TinyDDS in its current form lacks the reliability support for data delivery. In this paper, we extended the DDS data reliability service and integrated it into TinyDDS, which resulted in Reliable TinyDDS. Moreover, we provide a prototype and comprehensive performance evaluation of the reliability functions taking into account: number of hops, number of publishers, and several other network parameters. The achieved results indicate that reliable data delivery in real-time for WSAN is possible with optimized system parameters, such as retransmission time-out value of 400ms and number of hops not exceeding 10 for an end-to-end delay ranging from 10 to 100s of milliseconds.

A Novel Mobility-Aware Data Transfer Service (MADTS) Based on DDS Standards

Information sharing between mobile devices has gained immense popularity in recent times, owing to advances in network bandwidth and sophistication of mobile applications. Developing such applications to facilitate seamless information sharing between heterogeneous mobile devices can be cumbersome. The Object Management Group DDS (Data Distribution Service) specification provides a standard for a range of real-time mobile systems and embedded computing environments, from small networked embedded systems up to large-scale information backbones, to communicate with each other. The service exhibits features such as asynchronous interaction, Quality of Service (QoS) support, and a dynamic discovery mechanism to support smooth hand-off during communication. In this paper, we propose a service architecture model to facilitate uninterrupted mobile communications, using the DDS specification, so as to minimize disconnections during the data communication between mobile nodes due to mobility factors. We also introduce the application of the DDS QoS module for evaluating our mobility-aware data transfer model. Several experiments were conducted to identify the capabilities of the proposed approach in a heterogeneous environment in terms of latency and throughput, using a two mobile node scenario, and the results were found to be promising.

Designing High Performance Factory Automation Applications on Top of DDS

DDS is a recent specification aimed at providing high-performance publisher/subscriber middleware solutions. Despite being a very powerful flexible technology, it may prove complex to use, especially for the inexperienced. This work provides some guidelines for connecting software components that represent a new generation of automation devices (such as PLCs, IPCs and robots) using Data Distribution Service (DDS) as a virtual software bus. More specifically, it presents the design of a DDS-based component, the so-called Automation Component, and discusses how to map different traffic patterns using DDS entities exploiting the wealth of QoS management mechanisms provided by the DDS specification. A case study demonstrates the creation of factory automation applications out of software components that encapsulate independent stations.

Bloom filter-based discovery protocol for DDS middleware

The Data Distribution Service (DDS) middleware has recently been standardized by the OMG. Prior to data communication, a discovery protocol had to locate and obtain remote DDS entities and their attributes. Specifically, DDS discovery matches the DataWriters (DWs) and DataReaders (DRs) entities ( Endpoints) situated in different network nodes. DDS specification does not specify how this discovery is translated “into the wire”. To provide interoperability and transparency between different DDS implementations, the OMG has standardized the DDS Interoperability Wire Protocol (DDS-RTPS). Any compliant DDS-RTPS implementation must support at least the SDP (Simple Discovery Protocol). The SDP works in relatively small or medium networks but it may not scale as the number of DDS Endpoints increases. This paper addresses the design and evaluation of an SDP alternative–which uses Bloom Filters (BF)–that increases DDS scalability. BFs use Hash functions for space-efficient probabilistic data set representation. We provide both analytical and experimental studies. Results show that our approach can improve the discovery process (in terms of network load and node resource consumption), especially in those scenarios with large Endpoint per Participant ratios.