An efficient reservation MAC protocol with preallocation for high-speed WDM passive optical networks
ABSTRACT Wavelength division multiplexing passive optical networks (WDM PONs) can dynamically offer each end user a unique optical wavelength for data transmission as well as the possibility of wavelength reuse and aggregation, thereby ensuring scalability in bandwidth assignment. In this paper, we propose a new byte size clock (BSC) reservation MAC scheme that not only arbitrates upstream transmission and prevents optical collisions, but also varies bandwidth according to demand and priority, reduces request delay using pre-allocation and delta compression, and handles the addition/reconfiguration of network nodes efficiently. The new access scheme exploits both WDM and TDM to cater for both light and heavy bandwidth requirements and supports both Ethernet and ATM packets without segmenting or aggregating them. Our proposed protocol is not only backward compatible with APON and EPON, but also provides a better utilization of the access link in terms of the throughput and delay. In addition, the amount of pre-allocated bandwidth can be minimized using delta compression, which in turns reduces the latency due to the request and grant mechanism. We analyzed, evaluated, and simulated the performance and practicality of the proposed scheme.
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ABSTRACT: The fundamental stability limit and packet delay characteristics of offline scheduling, an elementary scheduling mechanism in recently proposed dynamic bandwidth allocation mechanisms for Ethernet passive optical networks (EPONs) with wavelength division multiplexing (WDM), are unknown. For Poisson packet traffic and gated grant sizing, we develop an analytical framework for characterizing the stability limit and packet delay of off-line scheduling in WDM EPONs. We consider two reporting strategies: immediate reporting, whereby the report is immediately attached to an upstream data transmission, and synchronized reporting, where all reports are sent at the end of a polling cycle. We find that our analytical framework correctly characterizes the stability limit and approximates the delay of (i) synchronized reporting with arbitrary traffic loading and (ii) immediate reporting with symmetric traffic loading (where the number of equally loaded ONUs is an integer multiple of the number of upstream channels). For immediate reporting with asymmetric traffic loading, we discover and analytically characterize multicycle upstream transmission patterns that may increase or decrease the stability limit from the limit for synchronized reporting. We complement the analysis and simulation for Poisson packet traffic with simulations for self-similar packet traffic and observe that self-similar traffic results in substantially higher delays at low to medium loads as well as slightly higher stability limits than Poisson traffic.Journal of Optical Communications and Networking 02/2010; · 1.43 Impact Factor
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ABSTRACT: We analyze the mean packet delay in an Ethernet passive optical network (EPON) with gated service. For an EPON with a single optical network unit (ONU), we derive i a closed form delay expression for reporting at the end of an upstream transmission, and ii a Markov chain-based approach requiring the numerical solution of a system of equations for reporting at the beginning of an upstream transmission. Reporting at the beginning, which has not been previously examined in detail, achieves significantly smaller delays than re-porting at the end of an upstream transmission for a small number of ONUs. Both of these analyses are fundamentally different from existing polling sys-tem analyses in that they consider the dependent switchover times of the EPON. We extend the analysis for reporting at the beginning of an upstream transmission to approximate the mean packet delay in an EPON with mul-tiple ONUs and verify the accuracy of the analysis with simulations. Overall, our numerical results indicate that for utilizations up to 75%, the mean packet delay is close to its minimum of four times the one-way propagation delay.Journal of Optical Networking 01/2008; 7(1). · 1.08 Impact Factor
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ABSTRACT: This study proposes a novel WDM EPON system based upon an AWG, in which multiple wavelengths are established in both the upstream and the downstream fibers. The use of the AWG device enables the WDM EPON architecture to support wavelength spatial reuse and allows the ONUs to communicate directly with one another rather than through the OLT. The proposed WDM EPON scheme takes account of the requirement for backward compatibility with the 802.3ah MPCP and investigates the associated DBA algorithm used to arbitrate the access of each individual ONU over the WDM layer.Networks, 2007. ICON 2007. 15th IEEE International Conference on; 12/2007