Mean Packet Delay Research Articles

用于可信任中继量子密钥分配网络的差异化服务提供机制

In order to provide different quantum key service,trusted relay quantum key distribution networks with quantum key pool was studied.Firstly,relationship between packet delay and quantum key pool was analyzed.The formula was given,which showed that the mean packet delay is related to the quantum key generation rate,the initial length of quantum key,the mean length,arrival time and arrival rate of packets.The theory and simulation results verified the accuracy of the delay analysis.Next,the key providing service was classified into three types:guaranteed,prioritized and best-effort key service.Correspondingly,pre-reserving,hop-by-hop jumping-queue and hop-by-hop queuing approaches were presented to realize the above differentialized key services.Finally,simulation results verified the efficiency of the differentialized service providing scheme.

Impact of report message scheduling (RMS) in 1G/10G EPON and GPON

A wide array of dynamic bandwidth allocation (DBA) mechanisms have recently been proposed for improving bandwidth utilization and reducing idle times and packet delays in passive optical networks (PONs). The DBA evaluation studies commonly assumed that the report message for communicating the bandwidth demands of the distributed optical network units (ONUs) to the central optical line terminal (OLT) is scheduled for the end of an ONU's upstream transmission, after the ONU's payload data transmissions. In this paper, we conduct a detailed investigation of the impact of the report message scheduling (RMS), either at the beginning (i.e., before the pay load data) or the end of an ONU upstream transmission on PON performance. We analytically characterize the reduction in channel idle time with reporting at the beginning of an upstream transmission compared to reporting at the end. Our extensive simulation experiments consider both the Ethernet Passive Optical Networking (EPON) standard and the Gigabit PON (GPON) standard. We find that for DBAs with offline sizing and scheduling of ONU upstream transmission grants at the end of a polling cycle, which processes requests from all ONUs, reporting at the beginning gives substantial reductions of mean packet delay at high loads. For high-performing DBAs with online grant sizing and scheduling, which immediately processes individual ONU requests, or interleaving of ONUs groups, both reporting at the beginning or end give essentially the same average packet delays.

Scalable Architecture for VOD Service Enhancement Based on a Cache Scheme in an Ethernet Passive Optical Network

Video on demand (VOD) is becoming one of the most important services for many network operators. VOD needs a huge bandwidth to deliver data in a real-time network. Ethernet passive optical networks (EPONs) provide a low-cost and high-speed solution for multimedia services such as VOD. In this paper, we propose a scalable architecture based on an EPON, using single copy broadcast in the downstream direction and a special caching mechanism responsible for VOD requests, to improve VOD services. Our architecture consists of an optical network unit (ONU) with an associated storage unit and optical line terminal (OLT) components. We set a “broadcast” logical link identifier in the video packets so that all of the ONUs can accept them. Therefore, when the movie is sent from the OLT to the ONUs after it is requested by the user, each ONU accepts the movie packet and saves it in its own storage. In this architecture, the OLT just needs to send each video to the ONUs once, and the attached storage is responsible for future requests. With this architecture, at least 60% of VOD traffic can be saved in the feeder fiber. Simulation results show that our architecture can improve the overall quality of service in terms of packet loss, mean packet delays, jitter, and system throughput.

Analysis of Continuous Communication Availability in Vehicular Ad Hoc Networks

In this paper, we study the steady-state statistical properties of continuous communication path availability in vehicular ad hoc networks. We assume a network of highways with arbitrary topology. The mobile nodes arrive at the network through one of the traffic entry points following a Poisson process and move along a path according to a mobility model with a state-dependent mean speed. First, the joint distribution of the number of nodes in the highway segments of the network is determined. Then, the number of clusters in the node population of a network path is modeled as a Markovian birth-death process where a cluster is defined as a group of nodes that may communicate with each other directly or indirectly. Thus, the probability distributions of the number of clusters in a path and duration of continuous communication path availability time are derived as functions of mobility and traffic arrival parameters. We present mean durations of continuous availability and unavailability times and mean packet delay for end-to-end communications in a path. The given numerical results illustrate the effects of mobility and traffic arrival process on continuous communication path availability and packet delay. The results show that the mean durations of path availability and mean packet delay increase with the increasing transmission range. Clearly, while high path availability duration is desired but not high packet delay. Thus, the transmission range should not be chosen higher than needed for acceptable communication path availability, so as to maintain an acceptable mean packet delay. In practice, an adaptive transmission range may be required to achieve the right balance between the communication path availability and delay. The analytical results have also been compared with some available experimental studies and verified by two different simulation approaches.

Packet Delay in UAV Wireless Networks Under Non-saturated Traffic and Channel Fading Conditions

In this paper, we conduct a statistical analysis for the packet delay in a wireless network of unmanned aerial vehicles (UAVs) under non-saturated traffic and channel fading conditions. Each UAV runs the distributed coordination function of IEEE 802.11 at the medium access control layer, and all UAVs are one-hop neighbors. A pair of UAVs can communicate over the lossy wireless channel of a fixed data rate. A non-saturated traffic condition is used. By modeling each node UAV as a standard queueing system (i.e., $$M/M/1$$ or $$M/G/1$$ queue), we derive the mean packet delay under the non-saturated traffic condition. Numerical and simulation results show that the mean packet delay derived based on $$M/M/1$$ queue is accurate for UAV wireless networks under the non-saturated traffic condition and with an independent packet error rate. It is observed that the mean packet delay increases with either the number of UAVs in the network or the packet generation rate. More important, existing results in the literature, based on the saturated traffic condition (i.e., packets are always supplied for transmission), tend to overestimate by a large amount the mean packet delay for networks with non-saturated traffic. In the second part of this paper, we apply simulation data to analysis of the probability distribution function of the packet delay when the packet error rate equals zero. Using a distribution fitting tool, we observe that the packet delay can be well approximated by the sum of a deterministic delay, which corresponds to the time period during which the UAV senses the medium and is able to perform a successful transmission, and a random delay, which follows a Gamma distribution function.

Analysis of mean packet delay for upstream transmissions in passive optical networks with sleep mode

The sleep mode has been introduced to improve the energy efficiency of passive optical networks (PONs) with interleaved polling with adaptive cycle time (IPACT) as a medium access control (MAC) scheme. For energy saving, the sleep mode of each optical network unit (ONU) is activated based on the packet queue length for upstream traffic. We model such a PON as an N-user M/G/1 queue with reservations and vacations. Based on the framework of M/G/1 queueing analysis with some modification made to incorporate the nature of IPACT as well as the sleep mode, we derive a closed form expression of the mean packet delay. A unique challenge in our analysis is that certain quantities such as the residual time of an on-going sleep period for the upstream channel must be considered from the network's viewpoint while the delay due to the sleep mode experienced by a packet must be considered from the ONU's viewpoint. Simulation experiments are conducted to validate the analytical results and to show that the results are relatively insensitive to packet arrival statistics for large sleep periods. Finally, we demonstrate how a sleep period can be chosen given the quality-of-service (QoS) requirement on the mean packet delay.

Lightweight wireless protocol based on IEEE 802.11 for delay sensitive telerobotic systems

In this paper, we consider wireless telerobotic systems and protocol development for low-delay wireless communication. Telerobotics can be defined as the control of robot arms from a remote location. In a telerobotic system, there is a robot arm to be controlled that is identified as the `slave arm', and a remote operator at a distant location using a robotic manipulator that is called the `master arm'. In the control system measurements, actuator delays do degrade the system's performance. Therefore, communication delays between the master and slave arms, and their minimization, are of extreme importance in telerobotics. In this paper, we first develop a new wireless communication protocol, the lightweight wireless protocol (LWP), designed on top of the 802.11 media access control layer. This low-delay wireless LWP protocol is implemented on an embedded system (AirDrop-LWP) without an operating system and its associated overhead. Finally, 2 AirDrop-LWP--embedded systems running this low-delay wireless LWP protocol are used to build a telerobotic system with a Mitsubishi RV-2AJ industrial robot. The LWP protocol is also tested on a robot car controlled by an AirDrop-LWP card as a slave arm and a standard PC as a master arm. The key features of the LWP are a reduced packet size, simple protocol stack, predictive compression of operator movements, and prediction of lost data packets. The LWP protocol is compared with the user datagram protocol and significant performance improvements are observed: a reduced delay of up to 50% and an additional 20% lower delay via compression. Variation in the packet delay times is also an important parameter for the wireless control system. As the standard deviation of the packet delay times increase, and becomes less and less predictable, the resulting telerobotic system will be more and more difficult to operate. We measured the standard deviation of packet delays and observed that it increases with the packet size, and this increase is faster than the increase in mean packet delay.

State Dependent Attempt Rate modeling of single cell IEEE 802.11 WLANs with homogeneous nodes and Poisson packet arrivals

We study a State Dependent Attempt Rate (SDAR) approximation to model M queues (one queue per node) served by the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol as standardized in the IEEE 802.11 Distributed Coordination Function (DCF). The approximation is that, when n of the M queues are non-empty, the (transmission) attempt probability of each of the n non-empty nodes is given by the long-term (transmission) attempt probability of nsaturated nodes. With the arrival of packets into the M queues according to independent Poisson processes, the SDAR approximation reduces a single cell with non-saturated nodes to a Markovian coupled queueing system. We provide a sufficient condition under which the joint queue length Markov chain is positive recurrent. For the symmetric case of equal arrival rates and finite and equal buffers, we develop an iterative method which leads to accurate predictions for important performance measures such as collision probability, throughput and mean packet delay. We replace the MAC layer with the SDAR model of contention by modifying the NS-2 source code pertaining to the MAC layer, keeping all other layers unchanged. By this model-based simulation technique at the MAC layer, we achieve speed-ups (w.r.t. MAC layer operations) up to 5.4. Through extensive model-based simulations and numerical results, we show that the SDAR model is an accurate model for the DCF MAC protocol in single cells.

Quality of VoIP in WiMAX and UMTS

The deployment of the Next Generation Wireless Networks (NGWNs) has posed great challenges due to the demanding requirements to integrate different radio access technologies and to provide high Quality of Service (QoS) for applications such as Voice over IP (VoIP) traffic. To meet the demand of providing high-quality of VoIP at anytime and from anywhere, it is imperative to design suitable models to map QoS between different radio networks. In this paper we investigate the QoS performance of WiMAX and UMTS for supporting VoIP applications since UMTS and WiMAX are emerging as the promising technologies for building the NGWNs. We designed simulation modules in OPNET for both WiMAX andUMTS, and carried out extensive simulations to evaluate and analyze several important performance metrics such as Mean Opinion Score (MOS), end-to-end delay, jitter and packet delay variation. Simulation results show that WiMAX outscores UMTS with a sufficient margin, and provides better support to VoIP applications compared with UMTS.

Downstream-based Scheduling for Energy Conservation in Green EPONs

Maximizing the optical network unit's (ONU) sleep time is an effective approach for achieving maxi- mum energy conservation in green Ethernet passive optical networks (EPONs). While overlapping downstream and upstream ONU transmissions can maximize the ONU sleep time, it jeopardizes the quality of service (QoS) performance of the network, especially for downstream traffic in case the overlapping is based on the upstream time slot. In this paper, we study the downstream traffic performance in green EPONs under the limited service discipline and the upstream-based overlapped time window. Specifically, we first derive the expected mean packet delay, and then present a closed-form expression of the ONU sleep time, setting identical upstream/downstream transmission cycle times based on a maximum downstream traffic delay re- quirement. With the proposed system model, we present a novel downstream bandwidth allocation scheme for energy conservation in green EPONs. Simulation results verify the proposed model and highlight the advantages of our scheme over conventional approaches.

Analysis of discrete-time buffers with heterogeneous session-based arrivals and general session lengths

In this paper we study the effect of session-based arrival streams on the behavior of a discrete-time queueing system with infinite storage capacity and a single output line. These session-based arrival streams are a new and realistic approach for modelling traffic generated by users in a telecommunication network. Users from an infinite population can start and end sessions during which they are active and send packets to the queueing system. Each active user generates a random, yet strictly positive number of packets per time slot. There are T different sessions types, each characterized by their own general session-length, session-incidence and bandwidth distribution.The corresponding discrete-time queueing model is analyzed by a generating-functions approach with infinite-dimensional state description. We derive the steady-state probability generating functions of the buffer content and the packet delay. From these, we obtain the mean buffer content as well as the mean packet delay and even the mean session delay. Finally, some numerical examples illustrate the influence of various parameters on the buffer behavior.

Adjustable TXOP mechanism for supporting video transmission in IEEE 802.11e HCCA

The basic mechanism of HCCA (HCF Control Channel Access) has been introduced in IEEE 802.11e standard to support the parameterized QoS by allocating a fixed duration based on the requested TSPEC requirements during the admission control process. However, the variable bit rate (VBR) traffic (e.g., MPEG-2 and MPEG-4 video) cannot be surely supported. In this study, the adjustable TXOP mechanism for supporting video transmission, ATMV, has been proposed. The mechanism adaptively adjusts the TXOP duration according to a finite state machine based on feedback queue size information. The mechanism aims for prompt serving burst packets, generated from the incoming video frames, which finally minimizes the packet delay. Both system performance (mean packet delay, TXOP loss factor, and channel occupancy) and video quality (PSNR and MOS values) have been evaluated from five video clips in three categories by using the network simulator, NS2, with EvalVid toolset. The results reveal that the proposed mechanism performs well for rapid movement video category and adequately supports for other video categories.

Performance Evaluation of High Speed Data Networks with Different Transmission Modes

this paper, a discrete-time single server model is considered in which the server functions can be interrupted and serves on dual mode operating strategy. After a server interruption, the server can either continue the transmission of the message or can completely retransmit the message. These modes are called Continue After Interruption (CAI) mode and Repeat After Interruption (RAI) mode respectively. Two types of traffic are considered (i) multimedia data traffic server operates on Continuous After Interrupt (CAI) mode and (ii) normal data traffic mode server is at Retransmit after Interrupt (RAI) mode. First, we give some general results on a GI-1-1 queue. Next we derive expression for the probability generating function of system contents and cell delays. Some performance measures such as mean delays have been derived in both types of server modes. Keywords-time queueing model, mean packet delays, server interruption, Continue After Interruption (CAI) mode and Repeat After Interruption (RAI) mode.

Packet Delay Statistics of the Multichannel Selective-Repeat Automatic-Repeat-Request

In this paper, we conduct stochastic modeling and analysis of the packet end-to-end delay in a multichannel selective-repeat automatic-repeat-request (MSR-ARQ) protocol. In this protocol, the transmitter continuously transmits packets over multiple parallel channels and retransmits erroneously received packets with either dynamic or static packet-to-channel scheduling policy. Under the assumption that packets are always supplied at the transmitter, denoted by the saturated traffic condition, we analyze the steady state probability distribution function of the delay of an arbitrary packet, which is measured by the duration between the instant at which the packet is transmitted for the first time and the time it departs from the resequencing queue at the receiver. Using the analysis result, we numerically compute the distribution function for chosen values of the number of channels and the error rates to demonstrate the computational effectiveness of the result. With numerical and simulation results, we then study the performance of MSR-ARQ in terms of the mean packet delay and compare the two scheduling policies. It is shown that the dynamic scheduling achieves a better packet delay performance than the static scheduling. With the dynamic scheduling and the presence of difference between the error rates of parallel channels, the mean packet delay decreases as the difference between channels’ error rates increases. Moreover, the number of parallel channels has an insignificant impact on the mean packet delay, which shows that the use of parallel channels is favorable for the wireless or mobile communications to increase the data transmission rate while keeping the mean packet delay at an acceptable level.

An Energy-Efficient MAC Protocol Using Dynamic Queue Management for Delay-Tolerant Mobile Sensor Networks

Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC) for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay.

Virtually Dedicated Resource Allocation for VoIP Traffic in the Downlink Mobile WiMAX System With Hybrid ARQ

This paper introduces the concept of a virtually dedicated resource allocation (VDRA) scheme that significantly reduces signaling overhead for accommodating low/medium data traffic, including real-time VoIP traffic. The basic concept of the VDRA scheme is to allocate the virtually dedicated resource to each user and to use the resource only when there are data to be transmitted. The performance of the proposed VDRA scheme in downlink is analyzed using a queuing system with hybrid automatic repeat request retransmissions to derive the distribution of packet delay and user capacity. In addition, the analytical results are verified through simulation results. The performance of the proposed VDRA scheme is compared with the persistent allocation scheme and the dynamic scheduling scheme. The proposed VDRA scheme yields a 15%-28% increase in user capacity and a 26%-69% decrease in the size of signaling overhead compared with the dynamic scheduling scheme. The proposed VDRA scheme yields slightly better performance in terms of user capacity and signaling overhead than the persistent allocation scheme for accommodating even voice over Internet Protocol (VoIP) traffic. In addition, the proposed VDRA scheme yields much smaller mean packet delay performance than the persistent allocation scheme. Moreover, the application of the persistent allocation (PA) scheme is limited to only real-time periodic VoIP traffic. On the other hand, the applicability of the proposed VDRA scheme is much wider than the PA scheme, including periodic and nonperiodic traffic, as well as real-time and non-real-time traffic, because the proposed VDRA scheme requires no constraint to the input traffic.

Performance Evaluation of a Three Node Client Relay System

In this paper, the authors examine a client relay system comprising three wireless nodes. Closed-form expressions for mean packet delay, as well as for throughput, energy expenditure, and energy efficiency of the source nodes are also obtained. The precision of the established parameters is verified by means of simulation.

Occupancy Distributions of Homogeneous Queueing Systems Under Opportunistic Scheduling

This paper analyzes opportunistic schemes for transmission scheduling from one of n homogeneous queues whose channel states fluctuate independently. Considered schemes consist of an LCQ policy that transmits from a longest connected queue in the entire system, and its low-complexity variant LCQ(d) that transmits from a longest queue within a randomly chosen subset of d ≥ 1 connected queues. A Markovian model is studied where mean packet transmission time is n-1 and packet arrival rate is λ <; 1 per queue. Transient and equilibrium distributions of queue lengths are obtained in the limit as the system size n tends to infinity. It is shown that under LCQ almost all queues are empty in equilibrium, maximum queue length is 1, and the overall system occupancy is Θ(1) as n → ∞. Limiting distribution of the system occupancy is characterized. Limiting queue length distributions under LCQ(d) are also given. It is shown that if d is fixed then the system occupancy is Θ(n) and the queue length distribution has infinite support. If d = ω(1) but d = o(n) then the maximum queue length is 1 and the system occupancy reduces to O(n/d). Numerical comparison of the obtained asymptotic mean packet delays suggests that LCQ and LCQ(d) may have comparable delay performance for moderate values of n and d.

Analysis of Mean Packet Delay for Dynamic Bandwidth Allocation Algorithms in EPONs

Closed-form mathematical expressions of network performances, such as the mean packet delay, are useful for evaluating a communication network during the design process. This paper provides derivations of closed-form expressions of the mean packet delay for the gated service and the limited service of dynamic bandwidth allocation in Ethernet passive optical networks (EPONs). Based on the M/G/1 queueing analysis framework of a multiuser cyclic polling system, we derive the mean packet delay expressions by modifying the expressions for the reservation time component of the total delay. Results from simulation experiments confirm that our analysis can accurately predict the mean packet delay. Finally, we extend the analysis to demonstrate how the limited service can protect packets transmitted by a light-load user from having excessive delays due to high traffic loads from other users in the same EPON. The analytical results indicate that, in selecting the maximum length of a scheduling cycle for the limited service, there is a tradeoff between the mean packet delay under uniform traffic and the guaranteed upper bound on the mean packet delay under nonuniform traffic.

A bandwidth assignment polling algorithm to enhance the efficiency in QoS long‐reach EPONs

AbstractA novel polling algorithm is proposed to provide subscriber differentiation at the upstream channel in long‐reach EPONs. As operators and service providers prefer to operate at loads with no congestion and losses, the developed algorithm has been designed to improve the efficiency for those loads at which the network is likely to work. This new scheme permits to anticipate the transmission of some packets in order to take advantage of the wasted bandwidth between consecutive transmissions of ONUs. As a result, not only does this algorithm behave alike other polling algorithms for high loads, but it also improves the efficiency at low and medium loads, leading to a reduction in the mean packet delay. The new algorithm has been tested in different scenarios, motivated by the increasing interest in enlarging the long‐reach EPON distances. Simulation results show that as the distance increases, the algorithm achieves a significant reduction of the mean packet delay for an extended range of loads. Copyright © 2010 John Wiley &amp; Sons, Ltd.