<title>Cable modem architectures adapted to the noise problem in the upstream direction for multiple-access hybrid fiber coax networks</title>

Abstract

As interactive services require more bandwidth, high speed access networks must follow this trend. Although a Hybrid Fiber Coax (HFC) system provides a large bandwidth, many problems occur due to the accumulation of the ingress and impulse noise. In this paper the properties of the ingress and impulse noise will be explained based on a measurement campaign on different networks.The most striking result of the measurement campaign is the large dynamic and time-dependent behavior of the ingress noise. This dynamic behavior is an important factor in designing an upstream communication system. We show that for this reason optimized receivers will contain adaptive equalizers. This is illustrated by the performance analysis of a TDMA and an OFDM-CDMA system. Both systems are compared under the same environment. The results of this comparison shows how both can obtain the same performance.Considering the implications of both the TDMA and the CDMA system when using an equalizer in the head-end receiver, requirements for a total HFC network architecture are given. Especially synchronization and initialization issues must be addressed.