IP architecture of a MOST150 based infotainment system: Page 4 of 6

October 12, 2012 //By Alexander Leonhardi, Uwe Walter, Rico Hauke, Marco Maniscalco
IP architecture of a MOST150 based infotainment system
Internet access has become an essential feature of modern vehicle infotainment systems. Today, it is the prerequisite to provide the user with up-to-date online information and services. In the case of a high-end distributed infotainment system - which consists of, for example, a head unit (HU), a rear-seat entertainment unit and a TV tuner - the communication is largely based on the Internet Protocol (IP), whose mechanisms have to be coordinated accordingly.
the backend and directly access services on the Internet, e.g., for multimedia streaming.

The settings of the IP architecture define the (static) IP addresses and IP-related settings of the devices, their routing tables, as well as the rules for the firewall in the system. Through the routing tables, it is possible to divide the IP traffic into certain subnetworks. For example, the IP traffic of a mobile device using the Internet connection of the HU can be routed directly to the Internet, while bypassing the IPSec connection. Firewall rules prevent any IP traffic for the mobile device from being forwarded to other applications and devices on the infotainment network.

4. MOST150 Ethernet Channel

For the transmission of IP traffic between devices connected to MOST, the MOST150 Ethernet Packet (MEP) channel is used. We have already presented our investigations on the throughput with the maximum bandwidth allocated for the packet channel. In these experiments (see [3]) a net bandwidth of over 107 MBit/s was achieved, showing that the maximum bandwidth of 142.8 Mbit/s can be utilized to a large extent (i.e., 75%).

We are currently investigating the performance of the MEP channel in an actual system with development samples of their devices. For our experiments, the boundary was set to 65, leaving a maximum bandwidth of 43.75 Mbit/s for the packet channel. Due to the characteristics of MOST, this bandwidth is not influenced by parallel synchronous or isochronous channels used for the transmission of audio or video streams. However, it is influenced by parallel traffic on the MOST Data Packet (MDP) channel. We did our measurements without (yet) generating parallel traffic on the MDP channel.

The throughput was measured for TCP and UDP with iperf executed on the HU and the rear-seat entertainment unit. For unidirectional traffic, we achieved for TCP a bandwidth of 36 Mbit/s, which is about 82% of the maximum available bandwidth. Because of the protocol overhead of

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