A Multirate code for wired Local Area Networks

A matrix is described that transforms input vectors (blocks) of length (K - 2), consisting of digital PAM vector components, into output vectors (blocks) of length K. The matrix transformation is such that the spectrum of the output blocks have a DC null and that the shape of the power spectrum is controlled. In particular, assuming statistically independent PAM components as input and assuming that rectangular transmission pulses are used then the transmitted signal power is concentrated in the lower frequency range. This property and a DC null are of primary importance in wired LANs. The matrix transformation is implemented by using a multirate (MR) digital filter of low complexity. Since a matrix transformation is used, more than three levels per transmitted pulse can be sent resulting in a greater bandwidth efficiency. Furthermore the power efficiency can be increased by using Wagner decoding. The performance of the MR code is compared with that of the well known 100Base-TX ´Fast Ethernet´ standard. It is shown that the MR-code design and implementation is less complex than the 100Base-TX coding, and has a superior performance.