Limited Preemption UFWA

To observe the simulation result of the BLP of the real time traffic, we can find that BLP of the real time traffic is too low. Considering the nature of the shorter burst length of the real time traffic, we proposed a limited preemption scheme to modify the proposed UFWA to try to improve the throughput, called limited preemption UFWA (LP-UFWA). While doing wavelength pre-assignment function on the w^th wavelength and the preemption index (Rw) exceeds a threshold, Pth, we would set Rw equal to -1 not the original value, where -1 means the associated DB is blocked on the w_th wavelength. The following two figures, fig.4.11 and fig. 4.12 will show the improvement of the throughput and the associated BLP of the real time traffic. And the simulation results will be based on a threshold, Pth, which is equal to 1.5, equivalent to 15 time longer preempted length than the real time traffic. It can be found that the limited preemption does improve the throughput about 150 Mbps at traffic load intensity equal to 1. Especially for the utility method and the UFWA (M=2), the limited preemption scheme limit the occurrences of preemption, and that would overcome the weakness of preempting too much characteristic of the two algorithms. Fig. 4.12 shows the BLP of the real time traffic versus the traffic load intensity. Even the BLP is increasing dramatically compared to the original proposed UFWA, it is still only about 0.2% when the traffic load intensity equal to 1. Therefore, the LP-UFWA can maintain BLP of the real time traffic at a low level but improve the throughput.

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Fig. 4.11 Throughput of the Limited Preemption UFWA (LP-UFWA)

0.00%

Fig. 4.12 The BLP of the real time traffic of the LP-UFWA

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Chapter 5 Conclusions

The paper proposed the utility-based fuzzy wavelength assignment (UFWA) to not only support QoS, but also achieves higher throughput. The UFWA uses the suitable wavelength concentrator (SWC) to reduce the number of the placements of the fuzzy wavelength evaluator (FWE). The SWC also does the wavelength pre-assignment function on all W wavelengths, so that we can let all wavelengths to find their own scheduled ways other than the PLAUCVF and the EPCS. In addition, the UFWA uses four parameters, including preemption index, the used length of the FDL, void, and utilization to describe the wavelength pre-assignment results on all wavelengths. By considering these four parameters, the UFWA can use the utility function and the fuzzy logic system to make a balance between the used lengths of FDLs and the voids, and preempt bursts as short as possible. The fuzzy logic system can help us to classify these four parameters into several linguistic variables using associated fuzzy membership functions. Then we can utilize fuzzy rules to evaluate each wavelength’s adequate degree. To observe the simulation results, we find when M=4, the UFWA achieves almost the same high throughput as M=8 but we only have

to place half of the number of the FWEs than the UFWA when M=8. Besides, M=4 has shorter delay due to the more serious protection of using FDLs by the utility function.

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Moreover, due to the relatively low BLP of the real time traffic and the nature of delay sensitive of the real time traffic (shorter burst length), we proposed another algorithm, called the limited preemption UFWA (LP-UFWA) to achieve the higher throughput but still keep the low BLP of the real time traffic about 0.2% even when traffic load intensity equal to 1.

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Vita

He-Jyun Lin was born in 1985 in Kaohsiung, Taiwan. He received the B.E. and M.E. degree in the department of communication engineering, college of electrical and computer engineering from National Chiao-Tung University, Hsinchu, Taiwan, in 2007 and 2009, respectively. His research interests include optical networks.