100
combination that is functional at 175 m (574 ft) may become unreliable if the remote device is swapped out for another from a different manufacturer or a different model from the same manufacturer. Channel Components Finally, there are elements of a cable’s construction that can passively enhance signal propagation and boost the network’s performance over extended distances. It is possible to purposely design cables and channels that will support extended distances by modifying the cable conductor size, pair twist rates, and dielectric materials. However, these channels may not support all levels of PoE and Ethernet speeds up to 1000 Mbps with minimally compliant network equipment. The maximum supported distance of any cable will vary depending on the Ethernet speed (as explored previously) and the PoE level (15 W, 30 W, 60 W, and 100 W) to be carried. This was demonstrated in the two tests using five different cables from five different manufacturers and two different conductor gauges. Deliberately constructing a cable to support an extended distance may offer stable support at lower Ethernet speeds and PoE levels; however, if the design worsens the noise mitigation while improving its signal strength, it may do more harm than good. Additionally, several of the extended distance claims in the industry today are for plug-to-plug connections that cannot be considered structured cabling, and with their supporting verification testing conducted at ~20 °C (68 °F) only. As temperatures rise, cable attenuation and resistance will increase, and the maximum distance supported by any copper cable will decrease. For installations with pathways outside of a temperature-controlled environment, a change in temperature could make the difference between a functional IP camera and an inoperative one. Installation Environment Quite often, extended distance channels are routed in a pathway that is not temperature controlled or outside the footprint of a building. In a study titled “Environmental Resilience of Twisted Pair Ethernet Applications at Lengths Greater than 100 Meters,”
a set of channels consisting of cables with conductor gauges ranging from 21 AWG to 23 AWG were connected to a number of switch ports from various manufacturers. A section of the cables was routed through an environmental chamber that allowed the temperature to be raised and lowered. The frame error rate (FER) of each channel was observed at various Ethernet speeds, channel lengths, and temperatures (Figure 4). The results of this study, seen in Figure 4, showed that 1 Gbps Ethernet transmission exhibited a significant number of dropped frames when cable temperatures were raised above ~30 °C (86 °F) and channel lengths were longer than 150 m, regardless of the cable’s conductor gauge. At distances below 150 m, these channels were capable of supporting an acceptable FER for 1 Gbps Ethernet even at temperatures as high as ~60 °C (140 °F). REWRITING THE NARRATIVE AROUND EXTENDED DISTANCES Much of the narrative on extended distances seems to be centered around shooting for the stars, based solely on how far it is possible to push DC power. Many manufacturers fail to account for data transmission performance and how that can negatively impact their customers' network performance and business objectives. Extensive tests have demonstrated that copper cable-based channels are capable of successfully transmitting Ethernet signals and PoE beyond 100 m. However, there is clear evidence that different Ethernet transmission equipment has different tolerances for supporting extended distance channels. Additionally, some claims guarantee channel lengths at more than double the TIA 100 m specification but do not take into account this equipment variability, nor do they account for the fact that cable temperature can also have a significant impact on transmissions at these lengths. This is especially true as transmission speeds increase to 1 Gbps. The studies have shown that regardless of conductor gauge, channels of 150 m or less have the greatest probability of supporting Ethernet speeds up to 1 Gbps at an acceptable FER with the greatest variety of active equipment, with cable temperatures ranging from ~20 °C (68 °F)
90
Cable A 22 AWG
80
Cable B 22 AWG
Cable C 22 AWG
70
Cable D 23 AWG
60
Cable E 23 AWG
50
40
120 m
146 m
175 m
200 m
FIGURE 2 : Percentage of equipment that established link for the cable samples, 1000BASE-T. Source: Leviton
progressively less tolerant of extended distance connections, had much more variable results at this 150 m length. These switches recorded an unpredictable number of dropped frames for all channel types, regardless of their conductor size. Finally, channel lengths that exceeded the 150 m length with all three switch combinations exhibited a significant number of dropped frames and errors for 1 Gbps Ethernet, regardless of the cable’s conductor size.
Through testing thousands of different device combinations, this study demonstrated that different pieces of network equipment exhibited different abilities to support extended distance connections, even with the same cable. In other words, there is variability in capability and performance between identical device types of different age, manufacturer, and quality, with trends showing certain devices had a higher probability of failure at longer lengths than others. Essentially, this means a switch to a device
100BASE-TX Transmission Across All Lengths
1.0E+11
1.0E+10
1.0E+09
1.0E+08
1.0E+07
1.0E+06
1.0E+05
1.0E+04
1.0E+03
1.0E+02
1.0E+01
1.0E+00
Group #1
Group #2 Group #3
Group #4
Group #1
Group #2
Group #3 Group #4
Group #1
Group #2 Group #3
Group #4 Group #1
Group #2
Group #3 Group #4
210 METERS
180 METERS
150 METERS
120 METERS
Switch combo A
Switch combo B
Switch combo C
FIGURE 3 : 1000BASE-T results. Source: Leviton
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