A method (referred to as I-SWIFT) is presented for integrating the flow of synchronous voice streams into existing broadband cable systems. The interface between the integrated voice subnetwork and the cable system is realized by a metropolitan area gateway (MAG) implemented at the broadband cable headend. In I-SWIFT, an intelligent scheduling algorithm in the MAG dynamically allocates channel bandwidth using modified data switch-filtering techniques. The MAG accomplishes this by establishing a fixed voice frame (with realignment) which is implemented in an upwardly compatible fashion with respect to the existing carrier-sense multiaccess communication with collision detection (CSMA/CD) data stations. Thus, previously installed stations require no modification. It is shown that for typical system design parameters, the I-SWIFT gateway approach can achieve much improved performance over previous compatible voice/data integration methods.>