SP-RFI-I03-980202

1. SP-RFI-I03-980202 At time t₁, the CMTS transmits a map whose effective starting time is t₃. Within this map is a Request IE which will start at t₅. The difference between t₁ and t₃ is needed to allow for:
  • downstream propagation delay (including FEC interleaving) to allow all CMs to receive the Map
  • processing time at the CM (allows the CMs to parse the Map and translate it into transmission opportunities)
  • upstream propagation delay (to allow the CM's transmission of the first upstream data to begin in time to arrive at the CMTS at time t₃).

2. SP-RFI-I03-980202 At t₂, the CM receives this map and scans it for request opportunities. In order to minimize request collisions,it calculates t₆ as a random offset based on the Data Backoff Start value in the most recent Map (see Section 6.4.4, also the multicast SID definitions in Appendix, Section A.2).

3. SP-RFI-I03-980202 At t₄, the CM transmits a request for as many mini-slots as needed to accommodate the PDU. Time t₄ is chosen based on the ranging offset (see Section ) so that the request will arrive at the CMTS at t₆.

4. SP-RFI-I03-980202 At t₆, the CMTS receives the request and schedules it for service in the next map. (The choice of which requests to grant will vary with the class of service requested, any competing requests, and the algorithm used by the CMTS.)

5. SP-RFI-I03-980202 At t₇, the CMTS transmits a map whose effective starting time is t₉. Within this map, a data grant for the CM will start at t₁₁.

6. SP-RFI-I03-980202 At t₈, the CM receives the map and scans for its data grant.

7. SP-RFI-I03-980202 At t₁₀, the CM transmits its data PDU so that it will arrive at the CMTS at t₁₁. Time t₁₀ is calculated from the ranging offset as in step 3.