Browsing by Author "Ashraf, M. Waqar"

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Citation - WoS: 2
Citation - Scopus: 2
Disaster-Resilient Lightpath Routing in WDM Optical Networks
(Springer, 2022) Ashraf, M. Waqar; Butt, Rizwan Aslam; Faheem, M.; Tariq, M.; Munir, Abid
Optical network serves as a core network with huge capacity and a multitude of high-speed data transmission. Natural disasters and physical attacks showed significant impacts on the optical networks such as damages the network nodes and optical links. Network survivability attempts to provide uninterrupted services when network component ceases to function or malfunctioned either in the event of a disaster or due to human intervention. In this paper, two polynomial-time algorithms have been proposed to select an optimal pair of link-disjoint lightpaths between two network nodes such that (1) their minimum spatial distance (MSD) is maximized, and (2) the path length of the primary lightpath is minimized such that backup lightpath has some particular MSD from the primary lightpath while disregarding safe regions around the source and destination nodes. Through extensive simulations, it is shown that, in case of disaster event, the first algorithm (DPMMSD) computes the backup path with maximum survivability in case of multiple link failures of spatially close nodes, whereas second algorithm (CMMSD) computes the shortest backup lightpath while adhering to the target survivability requirements. DPMMSD, CMMSD and the benchmark EKSP enables the evaluation and comparison of the performance. EKSP computes more pairs hence takes more computing time whereas DPMMSD and CMMSD modestly discard the computation of self and repeating pairs, enabling quick computations.
Citation - WoS: 6
Citation - Scopus: 8
Sleep Assistive Dynamic Bandwidth Assignment Scheme for Passive Optical Network (PON)
(Springer, 2018) Butt, Rizwan Aslam; Faheem, M.; Ashraf, M. Waqar; Idrus, Sevia M.
In passive optical network (PON), in addition to efficient bandwidth management, a dynamic bandwidth assignment (DBA) scheme can also enhance the energy efficiency performance of the optical networks units (ONUs) during sleep mode. A few such green DBA schemes have been proposed in literature for EPON, however, ITU compliant PONs have not got attention. In this study, the role of a DBA scheme during the cyclic sleep mode for XGPON has been investigated. A sleep assistive (SA)-DBA scheme is proposed that not only improves the energy saving performance of cyclic sleep mode but also reduces the upstream delays and variance for all the type-2 (T2), type-3 (T3) and type-4 (T4) traffic classes. Although, the upstream delay of type-1 (T1) traffic class slightly increases, the average upstream delay of all the traffic classes remains below the set target delay limit of 56ms.
Citation - WoS: 6
Citation - Scopus: 6
Sleep-Aware Wavelength and Bandwidth Assignment Scheme for TWDM PON
(Springer, 2021) Butt, Rizwan Aslam; Faheem, Muhammad; Ashraf, M. Waqar; Arfeen, Asad; Memon, Kamran Ali; Khawaja, Attaullah
The energy efficiency and delay performance of PON are two inversely related phenomena. Higher sleep time of the Optical Network Units (ONUs) results in higher upstream (US) delays due to increased traffic queues during the ONU Asleep state. Although an efficient dynamic bandwidth and wavelength assignment (DWBA) scheme can decrease US delays by minimizing the bandwidth waste and improving the fairness of bandwidth distribution among the ONUs. However, the conventional DWBA schemes are not designed to work with cyclic sleep mode (CSM) and they keep on assigning bandwidth to ONUs even if the ONU is in Asleep state leading to wastage of bandwidth and degraded CSM performance. Therefore, in this work a sleep aware DWBA scheme for TWDM PON is presented to coordinate with CSM mode. It only assign bandwidth to Active ONUs during the guaranteed phase, surplus phase and excess phase allocation phases which minimizes the bandwidth waste and the bandwidth lost at the ONU end. The wavelength switching process is also improved by only considering the Active state ONUs to balance the traffic load on all the wavelengths. The simulation results support our claim as the SA-DWBA scheme on average achieves DWBA schemes due to up to 50% to 65% higher energy savings compared to other due to longer ONU Asleep times. However, the increased upstream delays of all the traffic classes in SA-DWBA scheme remain within the set delay limit of 50 ms.