Hello All,
Here is the scenario:
CM's diplexer HW supports the below:
1. 5 – 85 MHz US, 108 – 1218 MHz DS
2. 5 – 204 MHz US, 254 – 1218 MHz DS
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CMTS configurations:
US: 4 SC-QAM + 1 OFDMA
us-channel 1 frequency 16510000
us-channel 2 frequency 23010000
us-channel 3 frequency 29510000
us-channel 4 frequency 36010000
us-channel 12 frequency 45000000 141000000
DS is configured from 303 MHz onwards.
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If the TLV84.1 is specified as 3 (117Mhz) in the CM config file, which US frequency the CM diplexer should choose? 5 to 85 OR 5 to 204?
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Our understanding:
From the specification point of view:
TLV 21/84 is intended to convey to the CM the diplexer band edge information to which the plant is configured. It is sent in the MDD message. In the absence of TLV 84 in the configuration file, the CM uses TLV 21 to configure the proper CM diplexer split. With that said, TLV 84 has the same functionality in that it also describes US and DS band edge ranges configurable on the RF Plant. If present in the config file, it will override TLV 21. TLV 84 is also describing the configuration state of the RF Plant including the CMTS’s diplexer settings. For example, if TLV 84.1 is set to “3”, we are telling the CM that the US channels on this RF interface / MAC Domain could be configured from 5MHz to 117MHz. This also implies that the CMTS has a diplexer on the RF plant that is most likely 5-204 / 254-1218 MHz, certainly not 5-85 / 108-1218 MHz. The CM must choose the 5-204 / 254-1218 diplexer setting to be aligned with the RF plant.
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Also the below section from the specification is little deviating from our understanding:
The CM MUST set its diplexer upstream upper band edge to the highest upstream frequency that it supports within the range reported in
the Diplexer Upstream Upper Band Edge configuration file sub-TLV. If the supported CM diplexer upstream upper
band edge frequencies are greater than the Diplexer Upstream Upper Band Edge reported in the Diplexer Upstream
Upper Band Edge configuration file sub-TLV, the CM MUST set its diplexer upstream upper band edge to the
lowest upstream frequency that it supports.
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Please help clarifying the below queries:
1. With the above CMTS configuration, if TLV84.1 (117MHz) is in-between lowest CM diplexer US upper band frequency(85MHz) and highest CM diplexer US upper band frequency (204MHz), which US frequency the CM diplexer should choose? 5 to 85 OR 5 to 204?
2. With the above CMTS configuration, Is that OK to specify TLV84.1 as 3 (117MHz), as TLV 84 is to be specified by the MSO/service provider who is very well aware of the plant capacity/configuration?
3. Is that fine to specify only TLV84.1 in the CM config Or Do we need to specify both TLV 84.1 & 84.2?
Thanks,
Rajmohan