THE RANGE OF BASEBAND AND PASSBAND HDSLS IN NTTS LOCAL NETWORKS

This paper presents the results of a study made to determine the Line length coverage of the high-bit-rate digital subscriber line (HDSL) pr esent in NTT's local networks. The HDSL carries one bi-directionaI 784 kbit/s channel per pair and supports the digital interface at 1544 kb it/s by using two cable pairs. The primary purpose of this study is to estimate the range limits for candidate transmission schemes consider ing line installation conditions, and to determine the most promising transmission scheme and its feasibility given the environment of NTT's local networks. Pulse amplitude modulation (PAM) and quadrature ampli tude modulation (QAM) transmission schemes are compared for HDSL imple mentation. It is shown that 2B1-Q-PAM and 16-QAM generally achieve bet ter performance than the more complicated PAM and QAM given the presen ce intrasystem crosstalk interference (interference between identical transmission systems). The range limits determined by intersystem cros stalk interference (interference between different transmission system s) with basic rate access (BRA) implementing a burst-mode transmission method are also estimated. This paper concludes that 2B1Q-PAM achieve s the best overall performance in NTT's local networks. A feasibility study of 192-6144 kbit/s transmission is also described.