George John Kustka

Adaptive digital access protocol: new features and performance improvements

This paper reports on a broadband multiple access protocol for bi-directional hybrid fiber-coax (HFC) networks. Referred to here as the enhanced adaptive digital access protocol (ADAPt+TM), it builds upon earlier work to define a medium access control (MAC) protocol amenable to a multiple service environment supporting subscriber access in HFC networks with tree and branch topologies. ADAPt+ efficiently supports different access modes such as synchronous transfer mode (STM), asynchronous transfer mode (ATM), and variable length (VL) native data (e.g., IP, IPX). This enhanced protocol adapts to changing demands for a mix of circuit- and packet-mode applications, and efficiently allocates upstream and downstream bandwidth to isochronous and bursty traffic sources. This paper describes: ADAPt+ for upstream communication and multiplexing/demultiplexing for downstream communication; its applicability to STM, ATM and other native data applications; and performance attributes such as bandwidth efficiency and latency.

A New NTSC Co-Channel Interference Rejection Filter with Coded 6-VSB Modulation for Improved ATV Coverage

The Advanced Television Systems Committee (ATSC) advanced television (ATV) standard and its service area predictions assume the use of a comb filter at the receiver However, such a filter is not required by the ATV standard. There are also unresolved questions about the efficacy of the comb filter. We describe a new system, including an NTSC co-channel interference rejection filter with coded 6-level digital vestigial sideband (6-VSB) modulation, of comparable complexity, which offers improved ATV service area. Coverage analysis results demonstrate that the system provides much better co-channel performance today, with a comparable carrier-to-noise (C/N) threshold and better threshold performance when NTSC transmission ceases in the future. The new system obviates concerns about the reliability of the comb filter under conditions of noise, interference, and multipath.