Asynchronous communication and symbol synchronization in multipoint-to-point multicarrier systems

Discrete multitone (DMT) has been selected as the modulation technique for multipoint-to-point systems such as cable telephony and in home networks over conventional single-carrier techniques by several vendors, because it provides superior impulse noise immunity, frequency diversity, and spectral efficiency for many communication systems. This paper provides novel solutions for two key issues in such DMT and OFDM systems. First, a technique for in-band asynchronous communication, essential for adding new remote units, is presented. Second, a robust symbol synchronization technique, especially for aligning the transmissions of the remote units at the headend (the central site), is presented. Both techniques are highly efficient and cause negligible degradation in SNR