5.8 MOST

MOST (media-oriented synchronous transfer) is described by Heck et al . ¹¹ as an alternative network protocol designed for synchronous, asynchronous and control data over a low-cost optical fibre network. It is claimed that the technology sits between USB and IEEE 1394 in terms of performance and that MOST has certain advantages in the transfer of synchronous data produced by multimedia devices that are not well catered for in other protocols. It is stated that interfaces based on copper connections are prone to electromagnetic interference and that the optical fibre interface of this system provides immunity to such, in addition to allowing distances of up to 250 m between nodes in this case.

MOST specifies physical, data link and network layers in the OSI reference model for data networks and dedicated silicon has been developed for the physical layer. Data is transferred in 64-byte frames and the frame rate of data is dependent on the sampling rate in use by the connected devices, being 22.5 Mbit/s at a 44.1 kHz audio sampling rate. The bandwidth can be divided between synchronous and asynchronous data. Potential applications are described including professional audio, for transferring up to 15 stereo 16-bit audio channels or ten stereo channels of 24-bit audio; consumer electronics, as an alternative to SPDIF at similar cost; automotive and home multimedia networking.

There is now a detailed specification framework for MOST ¹² and it is the subject of a co-operation agreement between a number of manufacturers. It seems to have been most widely adopted in the automotive industry where it is close to being endorsed by a consortium of car makers .