Ethernet in the First Mile
For engineers struggling with the IEEE standard 802.3, this book annotates and explains the dense language of the standard document, taking particular care how to explain how the EFM dovetails with other standards.
TABLE OF CONTENTS Ethernet in the First Mile
Chapter 4: The Short-Reach Solution: 10PASS-TS
"We have two firmly entrenched camps that have been battling for nearly a decade over the choice between QAM (aka SCM or single carrier modulation) and DMT (aka MCM or multi-carrier modulation). This is a religious war, with fortunes to be made or lost on each side. As usual, the primary battle lines have been drawn by the IC vendors, but there are zealots among the equipment vendors and service providers as well."
-HOWARD M. FRAZIER
Introduction to VDSL
General Characteristics
Of all standardized xDSL flavors, Very-High Speed Digital Subscriber Line (VDSL) offers the highest bitrates. To accomplish this, VDSL transceivers use a much wider spectrum than any other xDSL: Standards originally provided for bandwidths up to 30 MHz, but currently approved frequency plans are all limited to 12 MHz (see Figure 4.3)-this is already a 10-fold increase over the 1.1 MHz of bandwidth used by ADSL.
As is explained in Chapter 3, signal attenuation increases with frequency and cable length, so the higher frequency range can only be exploited on very short loops. A typical reach often quoted for VDSL is 1.5 km, which limits its deployment options to private networks (e.g., LAN extentions) and phone lines served from a street cabinet. The high investment associated with building fiber-fed cabinets for VDSL distribution is probably the main reason for the slow take-up rate in most parts of the world.
Single-Carrier Modulation
Quadrature Amplitude Modulation (QAM) is a modulation method in which information is coded in the amplitude and...
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