Measuring delays in DOCSIS cable modem technology

Data over Cable Services Interface Specification (DOCSIS) is an International Standard that defines the interoperability between cable modem technologies. The most common deployed cable modem technology is known as Hybrid Fiber/Coax (HFC) network. In HFC, the components involved are the Cable Modems (CM) and the Cable Modem Termination System (CMTS). The fiber optic cable runs from the CMTS at the head-end to an optical node in the neighborhood and coaxial runs from the optical node to the cable modem. The DOCSIS protocol is the leading specification for carrying data between multiple cable modems and the CMTS using the HFC network.;DOCSIS is a Media Access Control protocol used in the HFC Network for two-way RF channel (upstream and downstream channel) communication in the Cable Industry. On the downstream channel, data flows from the CMTS to the cable modem and on the upstream channel; it flows from the cable modem to the CMTS. On the downstream channel, the CMTS broadcasts data and all the cable modems listen to the frames. The cable modem only accepts the frame when the destination matches its own or the devices, which are connected to it. The data transmission in the upstream channel is a multipoint to point Time Division Multiple Access (TDMA) (for DOCSIS 1.x and DOCSIS 2.0) and Synchronous Code Division Multiple Access (SCDMA) (for DOCSIS 2.0 and 3.0). The CMTS controls the data transmission in the upstream channel by sending bandwidth allocation MAP at regular interval (Godsay C.K., 2004).;The goal of this study is to determine the upstream scheduling service performance by performing simulations and measuring delays in DOCSIS cable modem technology.;In this study, a simulation software known as OPNET was used to measure the delay, using different system parameters.;The system parameters would be adjusted and the effect on delay would be obtained from the simulation performed using OPNET's DOCSIS Model Suite.;The delay on the upstream channel is the time it takes for a cable modem to make a request, receive a grant and send its data packets to the CMTS. Delay is very important for providing quality of service in DOCSIS. With the support of video, voice and data known as triple play, delay on the upstream channel plays an important role especially in providing real time video, voice and multimedia applications.