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Cisco Bug: CSCte10747 - USCB failed when CM rng-pwr higher than the P_max of its MTC mode

Last Modified

Oct 11, 2010

Products (1)

  • Cisco uBR10000 Series Universal Broadband Routers

Known Affected Releases


Description (partial)


There are two possible symptoms.

1. Modem may register in partial mode.
    This can be determined by "show cable modem [mac] verbose | inc Partial"
2. DOCSIS 3.0 Modem keeps cycling from offline to  "UB init(t)" state, but unable to register online properly.

show cable modem
MAC Address    IP Address     I/F         MAC           Prim RxPwr  Timing Num I
                                                               State            Sid  (dBmv) Offset CPE P
xxxx.yyyy.zzzz a.b.c.d      C5/1/0/UB   init(t)             5    19.00  2437   0   N

"Show cable modem [mac-address] verbose" shows that the modem individual channel transmit power level (Reported Transmit Power Level) is exceeding the Peak (Max) Transmit Power as allowed by the DOCSIS 3.0 Specification.

TI Based modem will complain at time of parsing REG-RESP:

[ERROR] [DOCSIS.CHM(pid=278)]: HAL_RngEnableMultipleTxMode failed
[INFO] [DOCSIS.REINIT_MAC(pid=313)]: ReinitMAC : DS = -1, UCID = -1, Reason = DYNAMIC_RANGE_WINDOW_VIOLATION (19) 


PHYv3.0 section 6.2.19 Transmit Power Requirement contains the transmit power budget on per channel basis, derived from the modem transmit channel set, and each individual upstream channel parameters. 

The existing DOCSIS plant may be designed for single channel DOCSIS 1.x/2.0 modems, which has a much higher maximum transmit power level, comparing to DOCSIS 3.0 modem operating in MTC-mode and having 2 or more channels. 

In such case, modem may ranged successfully prior to REGISTRATION, since modem is still operate with single channel, like legacy 2.0/1.x modem. As soon as it is transitioning to MTC-mode during REG-RESP, its allowable maximum transmit power level, as defined in the PHY3.0 spec, is far below the ranged reference channel power level, which lead to the above error condition, and modem stop any ranging attempts on the newly assigned channels. Eventually, it failed registration, and went offline. This cycle repeats. This case is only applicable if all upstream channels assigned to the modem channel set are exceeding the peak allowable transmit power level.

If not all channel are exceeding the peak transmit power level, then modem may register in partial mode. Another words, modem may still able to continue to range successfully on the channel(s) that are still within the range, and transmitting data on those channel in partial-mode.
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