Scuola Superiore SantAnna Simulazione di protocolli RT per Reti di Sensori Wireless in ambiente NS-2 Giuseppe Lipari, Paolo Pagano

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)2 Rational for this new Paradigm Networks are becoming faster and software complexity in a node higher, thus increasing the vagueness of simulation because of assumption of events within a node occuring in zero time; To reduce the gap and errors between a simulation and the final implementation; To simulate applications which need a very high level of accuracy in timing: need to consider detailed time usage within and outside a node; Ability to simulate homogeneous as well as hetrogeneous environments by using the appropriate CPU-OS combination profile at various nodes.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)3 Project phylosophy Integrate existing simulators –Network Simulator of Choice: NS-2 (USC-ISI, UCLA, UCB); –OS Simulator of Choice: RTSim (ReTiS Lab, Sant Anna).

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)4 NS-2 Architecture Application: –Standard network applications like FTP, Telnet or various Traffic Generators like CBR, Exponential... Agent: –Represent endpoints where network-layer packets are constructed or consumed, and are used in implementing protocols; Node: –Represents a basic node in the network. Can be configured to adopt various routing, MAC, LL, and PHY layer protocols.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)5 Expectations from new Architecture Simulation Time Accountancy for latency in: –Periodic and Aperiodic Task Set –Interrupt processing Ability to use existing NS-2 agents, MAC and PHY layers already provided in the standard distribution: – based WPANs supported starting from NS Transparency: –no major change in NS-2 user interface; –user provided by APIs accessible through the TCL front- end. Support for heterogeneous environments i.e. ability to simulate different CPU as well as OS profiles on various nodes in a simulation.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)6 The new Library added to NS-2 Implement RTSim Task Scheduler as an Application in NS-2 Framework –Simple and easy to do –Minor modification to RTLib Simulate different scheduling policies (FIFO, FP, EDF,...)

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)7 Kernel instructions The RT-Application is now in charge of: –scheduling packet transmission; –handle packet reception. Send and Receive instructions have been added to RTSim; FCFS (~TinyOS) and FP scheduling policies are simulated. Figures refer to FCFS scheduling policy.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)8 Computation and Network Load Simulate from light to heavy load in the node through a set of Dummy Periodic Tasks: –tuning the number of tasks; –tuning the task parameters (C,T,U) to obtain different loads. Calculating the total delay (source to destination) as a function of the packet and checking the impact of the scheduling policies in time sensitive applications; Network load tuned acting on transmission schedules and concurrent access.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)9 Network Scenarios (1) Starting from simple scenarios: –4 nodes located at the edges of a square communicating to a sink placed at the center of mass; no hidden terminal; no network structure (single cluster); no routing; the sink plays the role of WPAN coordinator. To re-obtain the governing laws of RT- computing. Screenshot of the Network AniMator (NAM)

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)10 Network Scenarios (2) Complicating the picture: –Introducing routing paths and data streams; –Nodes connecting different clusters fetch and forward the readings coming from other clusters. How do RT-issues influence the reactivity of such nodes? Screenshot of the Network AniMator (NAM)

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)11 t [s] Selection of relevant metrics By simulation we evaluate: –the maximum, mean and minimum latency observed in sending and receiving the packets; –the time propagation through the sender and recipient network stacks (including re- transmissions done at low layers); –the packet probability of being delivered. Applications can be sensitive to one, more or all these metrics.

Sensori wireless ed integrazione di sistema per applicazioni ubique in ambito ospedaliero 3 novembre 2006Paolo Pagano (ReTiS, SSSA Pisa)12 Outlook and Conclusions NS-2 and RTSim have been integrated to take into account RT-issues in wireless telecommunications; In WSNs these issues play a role whenever any QoS must be guaranteed by the nodes; Simple and more complicated scenarios are being simulated to evaluate selected metrics; FCFS and FP scheduling policies have been implemented and are being compared within certain network and CPU load conditions; results are coming...