A system and method for improved upstream data transmission. In an embodiment, a cable modem includes a transceiver configured for transmitting data upstream once permission is granted. In between times when permission to transmit is granted, however, the cable modem is configured to prepare as much data as possible for immediate upstream transmission once that very permission is granted. Thus, prior to permission being granted, the cable modem assembles (pre-processes) the data into transmit frames such that the data frames may be stored in a local memory coupled to the transceiver in a “ready-to-go” format. In this manner, the entire amount of time/bandwidth allocated to the cable modem in response to its request for upstream data transmission may be dedicated to actually transmitting data upstream as opposed to consuming time and bandwidth processing the data into data frames after upstream data transmission has been granted.