TABLE OF CONTENTS Broadband communications and home networking require higher data rates, which in turn demand higher speed modems. Several technologies are being developed to handle these increased data speeds. Only recently, V.34 modems were considered high-speed modems, delivering data rates up to 33.6 kbps. A modem speed of 28.8 kbps was considered very good. Then, the 56 k modems were introduced, with an average modem speed in the high 40 kbps. The tremendous increase in Internet use and the demand for very high-speed modems resulted in ISDN delivering 64 kbps, or combined 128 kbps. The demand kept forcing the speeds even higher as the DSL modems reached speeds in the Mbps.
When broadband communications and home networking became popular, speeds into the 10 and 11 Mbps range were possible, using parallel techniques, such as OFDM and more complex digital modulation schemes, for example, QAM systems. Data rates are continually improving: speeds up to 50 MHz, 100 MHz, 155 MHz, and even data rates into the Gbps are being developed.
Integrated services digital network (ISDN) has provided high-speed data rates for several years. ISDN uses the switched telephone network, the same as is used for the standard telephone. ISDN provides the user with two 64 kbps channels, also called bearer channels or B-channels and a lower speed D-channel. ISDN offers both high quality voice and high-speed data rates by combining the two 64 kbps channels to a 128 kbps bi-directional data channel. Although ISDN did...
