riented connectivity Cable TV Networks The downstream channel depends on the QAM technique used because that is what gives it the most bits per second and, hence, the fastest data rates down- stream, where rapid downloads are important. Upstream data rates range from 5Mbps to 30Mbps, and the upstream direction operates in the range of 5MHz to 42MHz. As mentioned earlier, this portion of the frequency band is especially sub- ject to noise interference, SO it requires modulation techniques such as Quadrature Phase-Shift Keying (QPSK) and 16-QAM, which transport fewer bits per second than other techniques but also provide better noise resistance. Cable Modem Standards Many standards deal with cable modems. CableLabs (www.cablelabs.org) is an indus- try leader in creating cable modem standards for the cable TV industry. CableLabs has defined the following standards: Data Over Cable Service Interface Specification (DOCSIS) PacketCable OpenCable VOD Metadata CableHome The Euro-DOCSIS standard was created based on the U.S. DOCSIS standard, with the goal of ensuring correct and optimal performance of Euro-DOCSIS modems and CMTSs in European networks as well as being fully compliant with the Euro- pean Digital Video Broadcasting (DVB) standard in the downstream. tComLabs (www.tcomlabs.com) developed the Euro-DOCSIS annex of the DOCSIS specifica- tion in 1999, with the cooperation of equipment vendors and cable operators. The European cable community agreed on final specifications in early 2000. ETSI has approved both DOCSIS and the Euro-DOCSIS annex as specifica- tions. The primary difference between DOCSIS and Euro-DOCSIS is that DOCSIS employs the 6MHz channel NTSC standard used in North America, whereas Euro- DOCSIS relies on the 8MHz PAL channel spacing used in Europe. Also, Euro- DOCSIS takes advantage of a higher capacity in the upstream band, ranging from 5MHz to 65MHz, versus the North American version, which uses 5MHz to 42MHz. Japan employs other variants of DOCSIS. DOCSIS For several years, cable TV operators h