TrueTime Network (External C)


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  •  Cross Industry

Short Description

TrueTime Network makes it possible to simulate wired and wireless network communications within Modelica models using Dymola. It simulates the physical layer, medium access and packet transmission in local area networks. The core of library is implemented as external C code.

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Long Description

TrueTime Network supports eight simple network protocol models: FlexRay, PROFINET IO, CSMA/CD (e.g. Ethernet), CSMA/AMP (e.g. CAN), Round Robin (e.g. Token Bus), FDMA, TDMA (e.g. TTP), and Switched Ethernet. Additionally, the wireless networks IEEE 802.11b/6 (WLAN) and IEEE 802.15.4 (“ZigBee”) are also available. Alongside the wired and wireless network models, the library includes various sending and receiving nodes for interfacing with the rest of the model). These make it possible to send and receive messages containing reals and arrays of reals over the networks. The network blocks can be configured via number of block parameters. Common parameters to all types of networks are the bit rate, the minimum frame size, and the network interface delay. For each type of network there are a number of further parameters that can be specified. For instance, TDMA requires the user to specify a cyclic transmission schedule. For the wireless networks it is possible to specify the transmit power, the receiver signal threshold, the path loss exponent, the ACK timeout, the retry limit, and the error coding threshold.

TrueTime Network is implemented in Modelica and in C. The Modelica classes used to model communication networks relies on external function calls that are implemented in C, which in turn invokes functions of the TrueTime simulation engine. When a node tries to transmit a message, a triggering signal is sent to the network block on the corresponding input channel. The network block contains a discrete-event simulator that reads incoming messages, handles the medium access and resolves collisions, simulates the actual data transmission, and writes outgoing messages. When the transmission of the message is finished, the network block sends a triggering signal on the output channel corresponding to the receiving node, and the transmitted message is put in a buffer at the receiving side. A message contains information about the sending and the receiving computer node, arbitrary user data, the length of the message, etc. The network models simulate transmission delay but ignore propagation delay, since the latter is typically very small in a local area network. Only packet-level simulation is supported, meaning that higher-level protocols such as TCP are not included.

Release History

Release Date

Release ID

with Modelica


Tested with

January 31 2009



Dymola 7.2

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