The Ethernet over passive optical network (EPON) has been recognized as a potential solution for providing integrated services to end users at bandwidths far exceeding current access technologies. We have previously proposed and demonstrated an EPON that uses an upstream carrier-sense multiple access with collision detection (CSMA/CD) protocol [1]. CSMA/CD is considered well-suited to current access network environments whereby upstream traffic is significantly lower than downstream traffic, allowing the former to have a much lower speed [2]. It has been shown that more than 95% of upstream packets can be delivered without collision with 10 Mb/s and 100 Mb/s upstream line-rates, thus readily supporting the large number of installed 10BaseT and 100BaseT devices in existing local area network interfaces [3]. With the emergence of IP telephony applications, we investigate in this work, the applicability of the CSMA/CD-based EPON for the delivery of real-time voice-over-IP (VoIP) traffic. For VoIP, quality of service (QoS) is determined not only by the end-to-end delay which encompasses queueing, medium access, and propagation delays, but also by the variation of this delay [4], We investigate through simulations the end-to-end delay and jitter characteristics of a realistic CSMA/CD-based EPON, and show that both measures are within the bounds recommended by current standards to meet QoS requirements, and thus allowing cost-savings through integration with commercially available standard-based VoIP devices and Ethernet chipsets. Our results highlight the potential of the EPON for the overlay of real-time VoIP with best-effort data for fiber to the home (FTTH) and curb (FTTC) services.
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