Issue link: https://www.e-digitaleditions.com/i/1156106
36 I ICT TODAY Active Line Noise BAN: 1022951525 Target RG: 290711056782 Frequency(kHZ) Tone(Tone allocation:U0 6-32, D1 33-868, U1 869-1205, D2 1206-1971) ALN — MASK(1% worst case 5-VDSL crosstalk) 0 -80 -90 -100 -110 -120 -130 -140 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 7,000 7,500 8,000 8,500 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 Noise (dBm/Hz) FIGURE 3: Induced 60Hz/noise effects on VDSL circuits. As shown in Figure 3, even with low levels of contin- uously induced 60 Hz voltages on their digital subscriber line (DSL) circuits that are used to provide the internet and U-verse TV services, a broad range of induced power harmonic noise frequencies could override on the induc- tion to amplify other minor or severe impairments causing severely detrimental video effects, such as pixelation, freezing, high forward error correction (FEC) counts, and reinitializations (REINITs) causing loss of sync. Other internet and IPTV service providers (e.g., Comcast, Charter Communications, CenturyLink) might experience the same impairments per the U-verse TV example. It has been determined in tests made at Fluke Labs that power influence (PI) levels exceeding 92 decibels above reference noise with C-message weighting (dBrnC) causes loss of sync between the IPTV video equipment located at both ends of the circuit. It is also known that excessive levels of impulse noise can cause pixelation and picture freezing, which can force the length of the circuit to be shortened to obtain acceptable service. However, induced longitudinal voltages can cause gateway devices and set top boxes (STBs) to "lock-up," thereby requiring rebooting or momentarily being unplugged in order to release the surge of electricity that caused the problem. Higher levels of induced currents/voltages can even damage the video equipment ports, gateways, and STBs, causing unnecessary outages, excessive technician repair visits, and the additional expense of replacing the units. There are similar EMI issues of less magnitude in the inside wiring from the gateway device to the STB/ DVR, especially due to the use of unshielded Cat 5 or Cat 6 cabling. Compact fluorescent lights (CFLs), treadmills, light dimmer switches, and a host of other harmonic-producing electrical loads can create high- frequency electrical noise problems that can affect the signal quality and customer QoE, leading to mysterious circuit malfunctions that are frustrating to find and troubleshoot. This same phenomenon occurs in LANs, even though the cable infrastructures are typically shorter in length than what is found in DSL video streaming services and are generally inside buildings. Buildings are notorious locations for sources of EMI generation. It takes only one antenna to pick up EMI, especially when most of the cables used are unshielded twisted pair (UTP) as shown in Figure 4. As the 100 meter (328 ft) maximum design length of Ethernet circuits is approached, similar QoE issues can start to occur with video streaming appli- cations and WLANS. Now that circuits are being allowed to exceed these lengths due to the use of extenders, there is a substantially higher risk of experiencing problems from EMI.