I'm having a hard time understanding how this relates to a HFC network. Because you have a different technology (optical) in-between the node and CMTS. Why is there no compensation happening in the (RF) receiving end of the node before the optical transmitter, and how are these (upstream) RF impairments transferred over fiber (I don't believe optical is plagued by these sort of impairments)? is there some 'meta data' added, on how the optical receiver in the headend should 'translate' the RF back to the CMTS? I find it hard to grasp how the optical translation of the (upstream) RF signal is affected and transferred to the CMTS on the other side. unless the CMTS instructs the modem to send a 'cleaner' upstream channel to the node, not the CMTS itself as implied here. because in a HFC network, there never is a direct RF connection between modem and CMTS (as also implied in the video, unless I misinterpreted).
The fiber optic cable is just the medium that transmits whatever signal it receives from one point to the other. An RF impairment on the coax portion of the plant can distort the signal travelling from the cable modem to the CMTS. That distorted signal is transmitted over the fiber portion of the plant to the CMTS just as it was received. The CMTS receives the distorted signal and determines how it needs to be adjusted to remove the effect of the impairment. It tells the cable modem how to pre-distort its signal in the inverse of what it originally received. When that pre-distorted (pre-equalized) signal passes through the impairment, the pre-distortion cancels out the effect of the impairment. That corrected (equalized) signal continues through the coax and fiber portion of the plant back to the CMTS.
An ICFR in PNM only shows you how the signal is distorted. It's like looking at the very top of the haystack on the channel. When a PNM tool shows you an ICFR that is out of spec, you should also be able to view the digital taps to see which of the 24 taps are elevated. Those digital taps are a graphical representation of how the cable modem is adjusting its equalizers to send the inverse signal to the CMTS to compensate for the upstream impairment. From that digital tap data, the PNM tool can calculate the approximate length of the echo cavity (micro-reflection) that is impacting the signal. We refer to that in our tool as the TDR or vTDR depending on the length. That echo cavity distance, plus a map in the PNM tool showing which devices are being impacted, will give you an idea of where to start looking for the fault that is causing the bad ICFR. This needs to be done in in conjunction with your plant maps so you know where your actives and passives are in relation to the impacted modems. There is an excellent explanation of how that works in this video: ua-cam.com/video/-foccyrN6_w/v-deo.html
Excelente explicación, lo traduje al Español y es casi perfecto. Thank you so much
Wow this is some good stuff!! Thank you
Thanks for sharing
I'm having a hard time understanding how this relates to a HFC network. Because you have a different technology (optical) in-between the node and CMTS. Why is there no compensation happening in the (RF) receiving end of the node before the optical transmitter, and how are these (upstream) RF impairments transferred over fiber (I don't believe optical is plagued by these sort of impairments)? is there some 'meta data' added, on how the optical receiver in the headend should 'translate' the RF back to the CMTS? I find it hard to grasp how the optical translation of the (upstream) RF signal is affected and transferred to the CMTS on the other side. unless the CMTS instructs the modem to send a 'cleaner' upstream channel to the node, not the CMTS itself as implied here. because in a HFC network, there never is a direct RF connection between modem and CMTS (as also implied in the video, unless I misinterpreted).
The fiber optic cable is just the medium that transmits whatever signal it receives from one point to the other. An RF impairment on the coax portion of the plant can distort the signal travelling from the cable modem to the CMTS. That distorted signal is transmitted over the fiber portion of the plant to the CMTS just as it was received. The CMTS receives the distorted signal and determines how it needs to be adjusted to remove the effect of the impairment. It tells the cable modem how to pre-distort its signal in the inverse of what it originally received. When that pre-distorted (pre-equalized) signal passes through the impairment, the pre-distortion cancels out the effect of the impairment. That corrected (equalized) signal continues through the coax and fiber portion of the plant back to the CMTS.
getting high ICFR right at the Node, could you advice,
An ICFR in PNM only shows you how the signal is distorted. It's like looking at the very top of the haystack on the channel. When a PNM tool shows you an ICFR that is out of spec, you should also be able to view the digital taps to see which of the 24 taps are elevated. Those digital taps are a graphical representation of how the cable modem is adjusting its equalizers to send the inverse signal to the CMTS to compensate for the upstream impairment. From that digital tap data, the PNM tool can calculate the approximate length of the echo cavity (micro-reflection) that is impacting the signal. We refer to that in our tool as the TDR or vTDR depending on the length. That echo cavity distance, plus a map in the PNM tool showing which devices are being impacted, will give you an idea of where to start looking for the fault that is causing the bad ICFR. This needs to be done in in conjunction with your plant maps so you know where your actives and passives are in relation to the impacted modems. There is an excellent explanation of how that works in this video: ua-cam.com/video/-foccyrN6_w/v-deo.html
@@ZCorum i use a Viavi meter.
only on OFDMA return