Operating Systems for Wireless Sensor Networks in Space

Operating Systems for Wireless Sensor Networks in Space Abdul-Halim Jallad and Tanya Vladimirova 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 1 MAPLD 2005/1005

Outline of Presentation n n Applications of wireless sensor networks in space Formation flying missions overview Requirements analysis of operating systems formation flying missions Testbed development Conclusions 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 2 MAPLD 2005/1005

Wireless Sensor Networks: Convergence of Technologies Wireless communications: optical and RF communications enable networking between nodes Embedded computing: Small and low-cost processors that are networked together facilitate collaboration through information and resource sharing 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Wireless sensor networks Page 3 Sensors: Miniaturization and micromachining makes tiny and lowcost sensors available commercially MAPLD 2005/1005

Wireless Sensor Networks in Space 1) Manned Spacecraft missions: e. g. crew health monitoring 3) Spacecraft Diagnostics and monitoring 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova 2) Spaced-based formation flying wireless sensor networks 4) Inter-planetary Exploration Temperature Sensors Page 4 Figure from MAPLD 2005/1005 http: //sensorwebs. jpl. nasa. gov/

Multi-Satellite Missions: Terminology n n n A Distributed Space System (DSS) is a system that consists of two or more satellites that are distributed in space and form a cooperative infrastructure for science measurement data acquisition, processing analysis and distribution. n A Cluster is a functional grouping of spacecraft, formations, or virtual satellites. A Sensor Web is a system of intracommunicating spatially distributed sensor crafts that may be deployed to monitor environments. Sensor webs may involve many non-space elements and are therefore not completely covered by DSS. 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova n A Virtual Satellite is a spatially distributed network of individual satellites collaborating as a single functional unit, and exhibiting a common system-wide capability to accomplish a shared objective. n A Constellation is a group of satellites that have coordinated coverage, operating together under shared control, synchronised so that they overlap well in coverage and reinforce rather than interfere with other satellites' coverage. A Formation is a multiple-spacecraft system with desired position and/or orientation relative to each other or to a common target. Formation flying is the term used for the tracking and maintenance of a desired relative separation, orientation or position between or among spacecraft. MAPLD 2005/1005 Page 5

Formation-Flying Missions: Types Signal Combination: Distinct sensors on separate nodes collect data from different sources and merge this data on-board of the formation to extract global information of a particular phenomenon e. g. Earth observation-1 mission. n Signal Separation: Measurements from the same source are collected by spatially distributed sensors onboard different nodes in the formation e. g. large synthetic apertures. n 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 6 Signal Coverage: A Sensor Web with identical sensors on the nodes with the purpose of covering wide areas of surface (e. g. multi-point sensing). n MAPLD 2005/1005

Formation-Flying Missions: The Information System Sensors and Actuators: These may be divided into three classes – spacecraft specific, formation-flying specific and payload specific On-Board Computing: • Hardware is to be power and memory efficient while being fault-tolerant. • Software includes: – mission software – middleware – an operating system to support distributed services. 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Inter Satellite Communications: Formation. Flying Missions: Information System Page 7 Intersatellite links are different from terrestrial WSN wireless links in two main aspects: • large distances involved and • predictability MAPLD 2005/1005

Model Application Aims of Research n n n To investigate the advantages and disadvantages of distributed computing on-board of formation -flying (FF) missions To study possible implementations of distributed computing on-board FF missions To propose an optimal operating system architecture for such missions n n Mission Model The Network For the purpose of n narrowing down the scope of this investigation we focus on a particular type n of FF missions – virtual satellites Application: Separation distances = in the order of kilometers Use of directional antennas. n n n The satellite nodes: n n 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Sensor web: Imaging Signal Separation: Synthetic apertures Mass <= 1 Kg Area <= 1 cm 3 Power <= 2 Watts Orbit = Low Earth Orbit (LEO) ~ 600 Km Page 8 MAPLD 2005/1005

Formation-Flying Mission: Information System Architecture Application Middleware App 1 Algorithms App 2 Modules App 3 Services Virtual Machine P o w er Middleware management Operating System Transport Threads Network Address space Data Link Physical Files Hardware Drivers Sensor Driver Hardware 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova M a n a g e m e nt Sensor Page 9 MAPLD 2005/1005

OS Design for Formation-Flying Missions Main Functions: Process Description and Control Scheduling Memory Management n Concurrency n n Input/Output Management File Management n n n Security Networking n n 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 10 Process description and control: Ø Fault-tolerance: e. g. process replication Ø Memory considerations Concurrency: Ø FF missions are distributed systems and involve concurrency Memory management: Ø Use of bulk memory Ø Program memory wash Input/output management File management: Ø Fault-tolerance Networking: Ø Space protocol for ISL and ground space links Security Scheduling: Ø Real-Time scheduling MAPLD 2005/1005 Ø Low-power scheduling

OS Design Factors for Formation-Flying Missions n OBDH Ø n ISL Ø Operating System n Page 11 The effect of the relative dynamics brought by FF on the OS design needs to be investigated The nature of the applications running on-board and its distribution among the FF nodes may have a direct impact on the OS design Constraints Ø 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova The OS needs to consider the bandwidth, power consumption and unreliability of the intersatellite links while making distributed decisions On-board Software Ø n The architecture of the on-board data handling system (e. g. distributed, centralized, multiprocessor etc. ) affect the operating system design Formation Flying (FF) Ø n Factors The limited size and therefore available energy for computation and communication is an important factor that the OS design has to MAPLD 2005/1005 consider

On-Board Data Handling for Pico-Satellites * = system-on-a-chip: may involve various technologies including mixed-signals (analog/digital) on a single substrate OBDH Ultra-low Power Multi-processor Systems Advanced Packaging Reconfigurable hardware FPGAs ASICs SOC* Si. Ge on SOI Time-Scale = ? ? ? 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 12 MAPLD 2005/1005

Types of Operating Systems Operating System Description Pros Cons Example/ Mission Monolithic Almost any procedure can call any other procedure. Efficient Lack modularity OS: Linux Mission: None Microkernel (client/server) A few essential functions are • Flexible embedded in the kernel. Other • Well suited for services run as processes in distributed systems user mode. Less efficient OS: QNX, Vx. Works than Missions: monolithic Tiung. SAT-1, PROBA Virtual Machines Exact copy of bare hardware. Lowperformance Component. Based The Operating system consists • Portable of a set of independent • Efficient components representing • Well suited for system resources distributed systems 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Portable Page 13 OS: Embedded Java Virtual machine Mission: None OS: Tiny. OS Mission: None MAPLD 2005/1005

The Tiny. OS: Component-Based OS Tiny. OS n n • • Operating system specifically designed for wireless sensor networks Applications consist of scheduler and a graph of components “Higher-level” components issue commands to and respond to events from “Lower-level” components Components contain: Set of command handlers, Set of event handlers, A fixed size storage frame, Collection of simple threads which can be scheduled. 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Tiny. OS Component Commands received Tasks Commands made Tiny. OS Application Events initiated Frame Events received Components can be implemented in hardware or software. Events propagate upward in the hierarchy Commands propagate downward in the hierarchy. Page 14 MAPLD 2005/1005

Operating System Design for Swarms of Pico-Satellites Design Requirements n n n Fault tolerance Small foot-print Low-power consumption Support for reconfigurable computing. Distributed system support n n Component. Based Model Component library Scalability Execution-Model Thread-based model Event-based model -The system uses a main thread, which hands off tasks to individual taskhandling threads -Tasks perform computations -High context switch overhead Support for inter-satellite link communications -Tasks are implemented as finite state machines - States of tasks are transitioned through events Conclusion: The component-based structural model provides flexibility, reusability and is suitable for distributed systems design while the eventbased behavioural model provides speed, low power and memory efficiency. 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 15 MAPLD 2005/1005

Distributed Computing for Formation-Flying Missions: Testbed Windows XP PC Visualization STK Matlab STK Advanced AO Satellite Tool Kit STK/ Connect TCP/IP server Simulink Ethernet GR-PCI-XC 2 V-FT XSV 800 LEON-3 Multiprocessor OBC RS 232 Linux development platform Programming Environment 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova DDD GCC Compiler DSU Monitor Page 16 MAPLD 2005/1005

System Emulation Distributed System Emulation Hardware Node Emulation Hardware n GR-PCI-XC 2 V-FT n n XC 2 V 3000 Virtex-II FPGA Ethernet PHY interface LEON-FT core Support On-board memory n n n SRAM SDRAM Flash PROM Figure from the “LEON-PCI-XC 2 V Development board user manual” 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova n XSV 800 n n n XCV 800 Virtex FPGA Ethernet PHY interface On-board memory n n SRAM Flash Prom n Mica 2 motes n n n 916 MHz Multichannel Radio Transceiver ATMEL 128 L 8 -bit low-power processor Compatible with Tiny. OS (specifically designed for sensor networks). Figure from the www. xess. com website Page 17 MAPLD 2005/1005 Figures from mica 2 datasheet

Pico-Satellite Computing Platform n The chosen processor is the LEON-3 soft IP core n n n 32 -bit SPARC V 8 architecture Could be used in a multiprocessor system Soft core (suitable for developing system-on-chip prototypes) Power-down mode is supported Embedded Hardware Debug Support Unit (DSU). 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova LEON-3 in a multi-prosessor configuration Figure from www. gaisler. com Page 18 MAPLD 2005/1005

Conclusions n n n Wireless sensor networks are a promising technology for space applications including orbital formation-flying (FF) missions and inter-planetary exploration. This research focuses on implementation of distributed computing on-board FF missions employing the wireless sensor networks concept. The various factors that affect the operating system (OS) design of FF missions may be divided into two categories: n n n A novel OS for multi-satellite FF missions should have the following features: n n n Traditional OS requirements: e. g. code efficiency and real-time performance. Specific requirements for FF missions: e. g. fault-tolerant distributed computing, orbit dynamics etc. An event-based execution model allowing to achieve low-power consumption and to fulfil the concurrency requirement with minimal amount of code. A component-based structural model allowing to achieve the modularity requirement and enabling the hardware/software boundary crossing, which provides support for reconfigurable and distributed computing. The Tiny. OS is selected as the baseline OS to be studied and adapted for use in distributed FF satellite missions. 11/23/2020 Abdul-Halim Jallad, Tanya Vladimirova Page 19 MAPLD 2005/1005