Frame Arrival Research Articles

Grant management procedure for energy saving TDM-PONs

Abstract In order to minimize energy consumption in Time Division Multiplexing-Passive Optical Network (TDM-PON), IEEE and ITU-T have mandated sleep mode mechanism for Optical Network Units (ONUs) in the latest TDM-PON standards (e.g. IEEE P1904.1 SIEPON, ITU-T G.sup45). The sleep mode mechanism is a promising mean for maximizing energy saving in an ONU. An ONU in sleep mode flips between sleep and active state depending on the presence or absent of upstream and downstream frames. To ensure Quality of Service (QoS) of upstream frames, the recent TDM-PON standards introduced an early wake-up mechanism, in which an ONU is forced to leave the sleep state on upstream frame arrival. When the Optical Line Terminal (OLT) of a TDM-PON allows early wake-up of its connected ONUs, it allocates gratuitous grants for the sleeping ONUs along with allocating upstream grants for the ONUs in active state. Note that, the gratuitous grants control message sent periodically by the OLT on Inter-Gratuitous grant Interval (IGI) time. After leaving sleep state due to the arrival of upstream frame, the ONU uses its allocated gratuitous grant to send a control message mentioning the amount of upstream bandwidth (upstream grant) required in order to forward the remaining frames in its buffer. However, the existing early wake-up process of ONU can lead to increase the energy consumption of an ONU. It is because of the ONU wakes-up immediately from the sleep state on arrival of the upstream frame, but even so, it needs to wait for forwarding the frame until its allocated gratuitous grant period, resulting in spending energy unnecessarily. In addition, current energy saving solution for TDM-PONs do not provide a clear solution on how to manage different types of grants (e.g. listening grant, upstream transmission grant) within a Dynamic Bandwidth Allocation (DBA) polling cycle. To address this problem, we propose a state-of-art Grant Management Procedure (GMP) in order to maximize energy saving in a TDM-PON with sleep mode enabled ONUs. GMP contributes in defining the location of the different types of grants during a DBA polling cycle. Furthermore, GMP devises a mechanism so as to allow an ONU to predict its assigned gratuitous grant control message arrival time, thereby allowing an ONU to remain its transceiver unit powered off until the arrival period of the next gratuitous grant control message, increasing the energy saving of the ONU. Results show that, with the increment of IGI, the energy saving performance of an ONU with GMP increases noticeably in compare to a conventional ONU (an ONU that does not use GMP) without imposing any additional upstream frame delay.

Early Wake-Up Decision Algorithm for ONUs in TDM-PONs With Sleep Mode

Recent IEEE and ITU-T standards for time division multiplexing-passive optical networks (TDM-PONs) with sleep mode recommend that the optical line terminal (OLT) in a TDM-PON should be in charge of invoking the optical network units (ONUs) to move into the sleep state in the absence of frames. It is considered that, upon upstream frame arrival, a sleeping ONU can leave the sleep state, in which an ONU turns off its transmitter or both its transmitter and receiver, immediately, prior to its assigned sleep interval length. In this paper, we refer to this approach as immediate early wake-up (IMEW). According to the standards, the OLT may or may not allow an ONU to trigger an early wake-up function (EWF) upon the upstream frames' arrival. If the OLT does not allow the EWF [we refer to this as not support early wake-up (NSEW)], an ONU should stay in the sleep state during its assigned sleep duration and buffer all the upstream frames while it is in this state. In IMEW, the upstream frames experience a small delay, but the ONU's energy consumption increases remarkably. Conversely, in NSEW, an ONU consumes less energy compared to IMEW at the price of increasing the upstream frame delay and the possibility of having its buffer overflow. In this paper, the limitations of IMEW and NSEW have motivated us to propose a novel early wake-up decision (EWuD) algorithm that aims at meeting the upstream frame delay requirement while reducing the ONUs' energy consumption as much as possible. The role of the EWuD algorithm is to select an appropriate time for triggering EWF, taking into consideration two factors: 1) buffer overflow probability and 2) delay requirement violation of upstream frames. We evaluate EWuD performances using our TDM-PON OPNET modular-based simulation model under a wide range of scenarios. The findings demonstrate that our proposed EWuD can successfully meet the delay requirements of all upstream frames while reducing the ONUs' energy consumption significantly.

Parallel Implementation of Real-Time Communication and IP Communication by using Multiple Ring Buffers

Recent Linux[7] kernel introduced an interrupt mitigation method called NAPI to reduce the overhead of interrupt handling procedures caused by frame arrival and transmission. However, NAPI caused serious delay and jitter in such procedures. On the other hand, many conventional real-time communication mechanisms were implemented independently to the existing network stack, and most of such mechanisms disabled the stack. There-fore, it is difficult to utilize both of real-time communication and IP communication in parallel. This paper proposed a parallel implementation method to realize both of real-time communication and IP communication simultaneously in a single computer unit. This method implement real-time network stack and IP network stack in parallel by using multiple queue functionality in a NIC (network interface card). Also, this method applied the interrupt mitigation method only to the IP stack. Therefore, this method achieved to reduce the overhead of the wide bandwidth of IP traffic, also to keep delay and jitter of real-time traffic enough small. Some experiments were conducted to measure the performance of the proposed method. The RTT (round trip time) delay of realtime communication was kept lower than 100μs even in high traffic load of 800 Mbit/s with small jitter; while the RTT of IP communication varied between 100μs to 20 ms. This paper introduced the design, implementation, and evaluation of the proposed method.

Study of the potential energy savings in Ethernet by combining Energy Efficient Ethernet and Adaptive Link Rate

ABSTRACTThe Energy Efficient Ethernet (EEE) standard (IEEE 802.3az) has introduced some modifications to existing Ethernet standards with the aim of improving energy efficiency in the transmission of data frames. The adopted mechanism is to use different power modes of operation such that a device can be put into a low‐power mode when there is no data to transmit and awake it very quickly upon frame arrival. This is expected to reduce energy consumption significantly, especially on low‐loaded links. An alternative to EEE, known as Adaptive Link Rate (ALR), was also proposed to improve energy efficiency in Ethernet by dynamically changing the link speed at different traffic loads. ALR reduces the energy consumption because the lower the link speed, the less energy is consumed. However, this option is no longer considered in the EEE standard process.In this work, the potential energy savings of combining both EEE and ALR are explored. The results show that such a combination can further improve the already efficient EEE standard given the different power overheads associated with transitions between the active and idle power modes at different link speeds. This conclusion provides a clear motivation to investigate the combination of EEE and ALR more in detail in further developments. Copyright © 2011 John Wiley & Sons, Ltd.

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Performance evaluation of a power saving mechanism in IEEE 802.16 wireless MANs with bi-directional traffic

One of the most important ways for extending the battery lifetime of Mobile Stations (MSs) in a wireless Metropolitan Area Network (MAN) is to conserve the power consumption effectively. When a power saving mechanism with the sleep mode in IEEE 802.16-2009 is used, the system will be in a sleep state and the energy will be saved if both the Uplink (UL) and the Downlink (DL) are idle. In this paper, we present a new mathematical analysis for the system model with synchronous multiple vacations to capture the working principle of the Power Saving Class (PSC) type III in IEEE 802.16-2009 by taking into account the bi-directional traffic (the UL traffic and DL traffic together). By using the methods of a semi-Markov process and a two-dimensional embedded Markov chain, we derive the steady-state probability distribution of the system. Noting that the transmission of UL data frame will not be influenced by the sleep mode, but the sleep mode can be terminated by the arrival of UL data frames, we give the formula for the average delay of the DL data frames taking the bi-directional traffic into consideration. Moreover, we also present the expression for the energy saving ratio. Analytical results and simulation results are provided to investigate and validate the influence of the system parameters on the system performance. Finally, considering the trade-off between the average delay of data frames and the energy saving ratio, we develop a cost function to determine the optimal length of the sleep window in order to maximize the energy saving ratio while satisfying the Quality of Service (QoS) constraint on the average delay of data frames.

Performance analysis of service differentiation in wireless local area networks with Poisson frame arrivals

We propose an analytical model for IEEE 802.11 wireless local area networks (WLAN), where both a multi‐dimensional discrete‐time Markov chain and an M/G/1/ K are used to compute the performance measures of interest. Instead of assuming saturated traffic load, we consider the more realistic Poisson frame arrival traffic model. To support service differentiation, two parameters are set according to the user's priority: initial window size and window increasing factor. Last but not least, computer simulation programs written in C language are run to verify the accuracy of the analytical results.

Loss performance model for wireless channels with autocorrelated arrivals and losses

In this paper, we firstly propose simple and computationally efficient wireless channel modeling algorithm that explicitly takes into account first- and second-order statistics of frame error observations. For this purpose we use a discrete-time Markov modulated process with at most single event (error) at any time slot. Then, we identify a class of priority queuing systems of G + G/GI/1/K type capable to model the frame transmission process over wireless channels with correlated arrival and loss processes. Using the proposed frame error process, performance evaluation model of the wireless channel at the data-link layer is then reduced to the special case of ∑ i D-BMAP i /D/1/K queuing system with non-preemptive priority discipline. The proposed queuing representation allows to capture forward error correlation (FEC) and automatic repeat request (ARQ) functionality of the data-link layer as well as distributional and autocorrelational properties of the frame arrival and frame loss processes. This model is further analyzed for a number of performance parameters of interest including probability function of the number of frames in the system and probability function of the number of lost frames. It is shown that the channel response in terms of the mean number of frames in the system and the mean number of lost frames varies substantially for different first- and second-order frame error and arrival statistics. The impact of input statistics is also different for normal ( ρ < 1) and overloaded conditions ( ρ ⩾ 1) of ∑ i D-BMAP i /D/1/K queuing system.