Step 4—Interpret the MAC Log File and Take Action
The search table is arranged so that the first frequencies tried are above 450 MHz. Because many CATV systems have been upgraded from 450 MHz to 750 MHz coaxial cable, digital channels have a high chance of being assigned in the new spectrum. The search table omits channels below 90 MHz and above 860 MHz since the DOCSIS specification does not mandate their coverage.
Some CATV systems use alternative frequency plans such as the IRC (Incrementally Related Carrier) plan and HRC (Harmonically Related Carrier) plan. Cisco cable access routers support both of these plans. Most of the IRC channel slots overlap the EIA plan.
Event 3—Obtain Upstream Parameters
The Cisco uBR924 waits for an upstream channel descriptor (UCD) message from the headend CMTS. The UCD provides transmission parameters for the upstream channel.
508146.124 | CMAC_LOG_STATE_CHANGE | wait_ucd_state |
508147.554 | CMAC_LOG_UCD_MSG_RCVD | 3 |
508147.558 | CMAC_LOG_UCD_NEW_US_FREQUENCY | 20000000 |
508147.558 | CMAC_LOG_SLOT_SIZE_CHANGED | 8 |
508147.622 | CMAC_LOG_FOUND_US_CHANNEL | 1 |
508147.624 | CMAC_LOG_STATE_CHANGE | wait_map_state |
508148.058 | CMAC_LOG_MAP_MSG_RCVD |
|
508148.060 | CMAC_LOG_INITIAL_RANGING_MINISLOTS | 40 |
Event 4—Start Ranging for Power Adjustments
The ranging process adjusts the transmit power of the cable access router. The Cisco uBR924 performs ranging in two stages: ranging state 1 and ranging state 2.
The CMAC_LOG_POWER_LEVEL_IS field is the power level that the CMTS told the Cisco uBR924 to adjust to. The CMAC_LOG_RANGING_SUCCESS field indicates that the ranging adjustment was successful.
508148.062 | CMAC_LOG_STATE_CHANGE | ranging_1_state | |
508148.064 | CMAC_LOG_RANGING_OFFSET_SET_TO | 9610 |
|
508148.066 | CMAC_LOG_POWER_LEVEL_IS | 28.0 | dBmV (commanded) |
508148.068 | CMAC_LOG_STARTING_RANGING |
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508148.070 | CMAC_LOG_RANGING_BACKOFF_SET | 0 |
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508148.072 | CMAC_LOG_RNG_REQ_QUEUED | 0 |
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508148.562 | CMAC_LOG_RNG_REQ_TRANSMITTED |
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508148.566 | CMAC_LOG_RNG_RSP_MSG_RCVD |
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508148.568 | CMAC_LOG_RNG_RSP_SID_ASSIGNED | 2 |
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508148.570 | CMAC_LOG_ADJUST_RANGING_OFFSET | 2408 |
|
508148.572 | CMAC_LOG_RANGING_OFFSET_SET_TO | 12018 |
|
508148.574 | CMAC_LOG_ADJUST_TX_POWER | 20 |
|
508148.576 | CMAC_LOG_POWER_LEVEL_IS | 33.0 | dBmV (commanded) |
508148.578 | CMAC_LOG_STATE_CHANGE | ranging_2_state | |
508148.580 | CMAC_LOG_RNG_REQ_QUEUED | 2 |
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508155.820 | CMAC_LOG_RNG_REQ_TRANSMITTED |
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508155.824 | CMAC_LOG_RNG_RSP_MSG_RCVD |
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508155.826 | CMAC_LOG_ADJUST_RANGING_OFFSET |
| |
508155.826 | CMAC_LOG_RANGING_OFFSET_SET_TO | 11954 |
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508155.828 | CMAC_LOG_RANGING_CONTINUE |
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508165.892 | CMAC_LOG_RNG_REQ_TRANSMITTED |
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508165.894 | CMAC_LOG_RNG_RSP_MSG_RCVD |
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508165.896 | CMAC_LOG_ADJUST_TX_POWER |
| |
508165.898 | CMAC_LOG_POWER_LEVEL_IS | 31.0 | dBmV (commanded) |
508165.900 | CMAC_LOG_RANGING_CONTINUE |
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508175.962 | CMAC_LOG_RNG_REQ_TRANSMITTED |
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508175.964 | CMAC_LOG_RNG_RSP_MSG_RCVD |
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508175.966 | CMAC_LOG_RANGING_SUCCESS |
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Troubleshooting Tips for the Cisco uBR924 Cable Access Router 15