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The paper presents the comprehensive transparency analyses in terms of low frequency approximation of perceived impedance for the notable passivity-based approaches such as wave variable (WV), time domain passivity observer and control (TDPC), energy-bounding approach (EBA) and predictive energy-bounding approach (Predictive-EBA). Firstly, low frequency models of perceived impedance for the aforesaid approaches are developed and then, analyzed and discussed in detail. Secondly, these approaches are compared with each other to study the transparency in free motion and contact mode for prominent two-channel (2C) force feedback architectures namely, position error-based force reflection (PE) and direct force sensing (PF). Lastly, the detailed analyses and comparisons among WV, TDPC, EBA and Predictive-EBA are done both qualitatively and quantitatively, followed by the important discussions and conclusions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]