Mean Packet Delay Research Articles

Reducing the Energy Consumption of Ethernet with Adaptive Link Rate (ALR)

The rapidly increasing energy consumption by computing and communications equipment is a significant economic and environmental problem that needs to be addressed. Ethernet network interface controllers (NICs) in the US alone consume hundreds of millions of US dollars in electricity per year. Most Ethernet links are underutilized and link energy consumption can be reduced by operating at a lower data rate. In this paper, we investigate adaptive link rate (ALR) as a means of reducing the energy consumption of a typical Ethernet link by adaptively varying the link data rate in response to utilization. Policies to determine when to change the link data rate are studied. Simple policies that use output buffer queue length thresholds and fine-grain utilization monitoring are shown to be effective. A Markov model of a state-dependent service rate queue with rate transitions only at service completion is used to evaluate the performance of ALR with respect to the mean packet delay, the time spent in an energy-saving low link data rate, and the oscillation of link data rates. Simulation experiments using actual and synthetic traffic traces show that an Ethernet link with ALR can operate at a lower data rate for over 80 percent of the time, yielding significant energy savings with only a very small increase in packet delay.

IP Encapsulation Mechanism for Efficient RSVP Tunnel in Next Generation Mobile Networks

This paper describes IP encapsulation technologies for the Mobile RSVP tunnel in next generation networks. Bandwidth is inherently a scarce network resource, and hence signaling overhead should be minimized as much as possible. However, because of duplicate RSVP messages, the existing RSVP tunnel-based mechanism suffers from bandwidth overhead and tunnel problems. The waste of network resources prevents low-cost network construction and the maximization of integrated network utility, which are the goals of next generation networks, and can lower the reliability of networks with the increase of service subscribers and resultant expansion of resource consumption. To solve these problems and to support end-to-end QoS efficiently, RSVP needs to be changed at a minimum degree. In this paper, a new IP encapsulation mechanism for saving of network resources in the Mobile RSVP tunnel (IPEnc-RSVP) is proposed. In order to compare the proposed mechanism and the existing RSVP tunnel-based mechanism in Mobile IP-based networks, we perform a comparative analysis of bandwidth consumption gain, throughput, mean packet delay, etc., and demonstrate the superiority of the proposed mechanism. In addition, we analyze several performance factors of RSVP protocols by applying the existing RSVP tunnel-based mechanism and the proposed mechanism, respectively.

Scheduling schemes for multimedia service in wireless OFDM systems

Scheduling schemes play a key role in the system performance of broadband wireless systems such as WLANs/WMANs. Maximal SNR and round robin are two conventional scheduling strategies that emphasize efficiency and fairness, respectively. The proportional fair scheme provides a trade-off between efficiency and fairness, and has been well studied in TDMA and CDMA systems. In this article we extended the PF scheduling scheme to OFDM-based BWSs (OPF). In addition, we propose three variations: adaptive OPF (AOPF), multimedia AOPF (MAOPF), and normalized MAOPF (NMAOPF) in order to meet the QoS requirements for multirate services in multimedia systems. The adaptive modulation and coding schemes in time varying and frequency selective fading are considered. The system performances of the algorithms are compared in terms of efficiency (throughput and mean packet delay) and fairness (user satisfaction rate and average user rate). Joint physical and media access control layer simulation results show that AOPF and MAOPF can improve throughput at the cost of fairness, and NMAOPF can provide the highest throughput without losing fairness.

Preferential transmission of multicast packets using a preallocation scheme in combination with a wavelength monitoring scheme on a RingO network

AbstractThis paper proposes a multicast packet preferential transmission system combining preallocation and waveform monitoring schemes with the RingO network. In the proposed system, a multicast packet preferential time slot is allocated to each node by preallocation. Each node can use all wavelengths in the allocated time slot to transmit a multicast packet simultaneously to all destination nodes. Wavelength monitoring is applied to time slots other than the allocated time slot, and if there is an available wavelength channel, a unicast packet is transmitted. Thus, the data packets are transmitted with high efficiency. The performance is evaluated by computer simulation. It is shown that the proposed system can greatly improve the mean packet delay and the throughput characteristics, compared to the simultaneous transmission system, in a heavily loaded situation with an input load exceeding 0.9. The proposed method is also shown to be more effective than the partitioned transmission system, in that the transmission delay difference of multicast packets between destination nodes, and also the packet delay difference of multicast packets for each destination node, can be reduced. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(7): 56– 68, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20375

IntServ6: an approach to support QoS over IPv6 wired and wireless networks

AbstractIn this paper we propose a new approach for Quality of Service (QoS) support on Internet. This approach, named IntServ6, is based on the Integrated Services Architecture (ISA). It takes advantage of the IPv6 header flow label field to improve a set of the standard ISA properties such as reservations within tunnels, flows aggregation and interconnection with MPLS transport networks. IntServ6 can be used for QoS support in IPv6 wired and wireless networks. This paper describes the IntServ6 operation and performance evaluation over both environments. Evaluation results show that this approach has a better router performance with respect to the standard IntServ. Thus, IntServ6 reduces the mean packet delay and reduces the packet delay dependence with the mobility. Copyright © 2007 John Wiley & Sons, Ltd.

A novel medium access control protocol for optical local networks based on data request ordering

The basic aim of the scheduling algorithms in wavelength division multiplexing (WDM) single-hop optical networks is to construct a short schedule, in order to support quick communication between the nodes of the network. A design of medium access control (MAC) protocol without collisions is introduced for scheduling variable-length data packets based on a broadcast and select architecture. The system includes only data channels and the coordination of the transmissions is achieved via control packets, functioning before the beginning of actual transmissions. The proposed scheme adopts a prediction mechanism in order to eliminate the possible delay introduced by the scheduling computation between the control and data phases of each cycle of transmission. The two common scheduling strategies suggested try to reorder the service sequence of the nodes, by prioritizing the nodes with long data packets, compared with the nodes with short data packets. The final schedule, formed by a scheduling matrix, seems to be much shorter and leads to an increase, in terms of channel utilization. The extensive simulation results show that the novel scheduling techniques offer more free time space for schedule and allow more data to travel on the medium for the same amount of time. Also, the mean packet delay on the queues is reduced and the relation throughput-delay is much better.

Discrete-time performance analysis of a congestion control mechanism based on RED under multi-class bursty and correlated traffic

Internet traffic congestion control using queue thresholds is a well known and effective mechanism. This motivates the stochastic analysis of a discrete-time queueing systems for the performance evaluation of the active queue management (AQM) based congestion control mechanism called Random Early Detection (RED) with bursty and correlated traffic using a two-state Markov-Modulated Bernoulli arrival process (MMBP-2) as the traffic source. A two-dimensional discrete-time Markov chain is introduced to model the RED mechanism for two traffic classes where each dimension corresponds to a traffic class with its own parameters. This mechanism takes into account the reduction of incoming traffic arrival rate due to packets dropped probabilistically with the drop probability increasing linearly with system contents. The stochastic analysis of the queue considered could be of interest for the performance evaluation of the RED mechanism for the multi-class traffic with short range dependent (SRD) traffic characteristics. The performance metrics including mean system occupancy, mean packet delay, packet loss probability and system throughput are computed from the analytical model for a dropping policy which is a function of the thresholds and maximum drop probability. Typical numerical results are included to illustrate the credibility of the proposed mechanism in the context of external bursty and correlated traffic. These results clearly demonstrate how different threshold settings can provide different trade-offs between loss probability and delay to suit different service requirements. The effects on various performance measures of changes in the input parameters and of burstiness and correlations exhibited by the arrival process are also presented. The model would be applicable to high-speed networks which use slotted protocols.

Performance of Scheduling Algorithms under Mobility for Multimedia Services in OFDM Systems

Scheduling algorithms are playing a key role in overall system performance of broadband wireless systems (BWS). Maximal SNR (MaxSNR) and Round Robin (RR) are two conventional scheduling strategies which emphasize efficiency and fairness respectively. Proportional Fair (PF) algorithm provides tradeoff between efficiency and fairness. In this paper, we apply PF to IEEE 802.16a OFDM based BWS and name it OPF. We also propose a new algorithm for multimedia services: Normalized Multimedia Adaptive OPF (NMAOPF). Adaptive modulation and coding scheme is applied in time varying and frequency selective fading wireless channel. System performances are compared in efficiency and fairness with and without user mobility. Efficiency is in terms of throughput, mean packet delay and packet drop ratio; fairness is in terms of user satisfaction rate and average user rate. Joint PHY and MAC layer simulation results show that: within the traffic range of 55 to 70 Mbps, compared with RR and MaxSNR, the performance of OPF is in between. Our proposed NMAOPF outperforms all others without user mobility, while under mobility, it is not as good as MaxSNR but better than OPF and RR.

Opportunistic Nonorthogonal Packet Scheduling in Fixed Broadband Wireless Access Networks

In order to mitigate high cochannel interference resulting from dense channel reuse, the interference management issues are often considered as essential part of scheduling schemes in fixed broadband wireless access (FBWA) networks. To that end, a series of literature has been published recently, in which a group of base stations forms an interferer group (downlink transmissions from each base station become dominant interference for the users in other in-group base stations), and the scheduling scheme deployed in the group allows only one base station to transmit at a time. As a result of time orthogonality in transmissions, the dominant cochannel interferers are prevented, and hence the packet error rate can be improved. However, prohibiting concurrent transmissions in these orthogonal schemes introduces throughput penalty as well as higher end-to-end packet delay which might not be desirable for real-time services. In this paper, we utilize opportunistic nonorthogonality among the in-group transmissions whenever possible and propose a novel transmission scheduling scheme for FBWA networks. The proposed scheme, in contrast to the proactive interference avoidance techniques, strives for the improvements in delay and throughput efficiency. To facilitate opportunistic nonorthogonal transmissions in the interferer group, estimation of signal-to-interference-plus-noise ratio (SINR) is required at the scheduler. We have observed from simulations that the proposed scheme outperforms the reference orthogonal scheme in terms of spectral efficiency, mean packet delay, and packet dropping rate.

Degenerate delay-capacity tradeoffs in ad-hoc networks with Brownian mobility

There has been significant recent interest within the networking research community to characterize the impact of mobility on the capacity and delay in mobile ad hoc networks. In this correspondence, the fundamental tradeoff between the capacity and delay for a mobile ad hoc network under the Brownian motion model is studied. It is shown that the two-hop relaying scheme proposed by Grossglauser and Tse (2001), while capable of achieving a per-node throughput of /spl Theta/(1), incurs an expected packet delay of /spl Omega/(logn//spl sigma//sub n//sup 2/), where /spl sigma//sub n//sup 2/ is the variance parameter of the Brownian motion model. It is then shown that an attempt to reduce the delay beyond this value results in the throughput dropping to its value under static settings. In particular, it is shown that under a large class of scheduling and relaying schemes, if the mean packet delay is O(n/sup /spl alpha////spl sigma//sub n//sup 2/), for any /spl alpha/<0, then the per-node throughput must be O(1//spl radic/n). This result is in sharp contrast to other results that have recently been reported in the literature.

GPON service level agreement based dynamic bandwidth assignment protocol

A dynamic bandwidth assignment protocol is proposed that demonstrates impartial and highly efficient bandwidth arrangement for gigabit-capable passive optical networks. In particular the novel algorithm automatically modifies the assigned bandwidth per optical network unit to support quality of service and service level agreement according to maximum network capacity and users&apos; queuing status. Network simulation results have demonstrated superior mean packet delay performance achieving a tenfold reduction of packet delay at high network load when compared to other dynamic bandwidth assignment algorithms.

Packet Delay Analysis of Symmetric Gated Polling System for DBA Scheme in an EPON

In this paper, we analyze the mean packet delay of a dynamic bandwidth allocation (DBA) scheme in an Ethernet passive optical network (EPON). We propose the interleaved polling system with a gated service discipline and a two-stage queue in order to investigate the delay performance of DBA scheme in an EPON. We assume that input packets arrive at an optical network unit (ONU) according to a Poisson process from several types of users. We use a continuous time queueing model in order to find the mean packet delay and the mean cycle time of an arbitrary packet. We obtain the closed form solution for the mean packet delay of the proposed gated polling system with a two-stage queue. We obtain another result on the mean packet delay by solving a system of linear equations derived from the moments of the queue length distribution. We give some numerical results to investigate the delay performances for the symmetric polling system with statistically identical stations. In addition, we compare numerical results on the closed form solution with numerical results on a system of linear equations.

Performance analysis of a discrete-time queuing system with a correlated train arrival process

In this paper, we present an exact transient and steady-state discrete-time queuing analysis of a statistical multiplexer with a finite number of input links and whose arrival process is correlated and consists of a train of a fixed number of fixed-length packets. The functional equation describing this queuing model is manipulated and transformed into a mathematical tractable form. This allows us to derive the transient probability generating function (pgf) of the buffer occupancy. From this transient pgf, time-dependent performance measures such as transient probability of empty buffer, transient mean of buffer occupancy and instantaneous packet overflow probabilities are derived. By applying the final-value theorem, the corresponding exact expressions for the steady-state pgf of the queue length and packet arrivals are derived. We also show how the transient analysis provides insights into the derivation of the system's busy period distribution. Closed-form expressions for the mean packet and message delays are also provided. The paper presents significant results on the transient and steady-state analysis of statistical multiplexers with N input links and correlated train arrivals.

Performance of wireless networks with hidden nodes: a queuing-theoretic analysis

Hidden nodes are a fundamental problem that can potentially affect any wireless network where nodes cannot hear each other. Although the hidden node problem is well known, so far only few papers have quantified its effects in a comprehensive manner. This paper represents a first step towards getting a quantitative insight into the impact of hidden nodes on the performance of wireless networks. We first carry out an exact queuing-theoretic analysis for a 4-node segment and derive analytical expressions for the probability of packet collision, the mean packet delay, and the maximum throughput, based on a model that closely follows the IEEE 802.11 standard. We then extend the analysis and provide an approximation for a general linear topology that is asymptotically exact at low load. Finally, we perform detailed simulations to validate our analytical results and show their applicability to predict the performance of IEEE 802.11 networks with hidden nodes. The simulation and analysis closely match. Moreover, they reveal that the impact of hidden nodes propagates through the network causing some nodes to saturate at load as low as 15% of the capacity.

Delay controllable protocol with multiple priorities for home automation network

Media access control (MAC) protocol based on carrier sense multiple access (CSMA) with bounded packet delay for each priority is useful for real-time and emergent use. In this paper, a CSMA based protocol with multiple priorities for home automation network is proposed to ensure controllable mean packet delay (CMPD) for all priorities under heavy traffic load. A transmission ratio assignable (TRA) algorithm is used to achieve CMPD for each priority. Analysis of the TRA algorithm is presented, and the CMPD theorem is proved that the CMPD is inversely proportional to the assigned successful transmission ratio for all priorities. It is meaningful because the CMPD can be controlled by assigning different successful transmission ratio to different priorities. Furthermore, simulation results demonstrate that the TRA algorithm and the CMPD theorem are correct.

Evaluations on a Buffering WDM Optical Packet Switch Equipped with Shared Wavelength Converters

In this paper, a buffering WDM optical packet switch scheme employing the wavelength converters for contention resolution is evaluated. The architecture is dedicated to an individual buffer for each output and is equipped with tunable wavelength converters (TWCs) shared among the input lines. With the wavelength dimension for contention resolution, the size of each output buffer is reduced and less number of wavelength converters is employed; therefore, it is cost-effective. Based on the switch architecture, lower packet loss probability can be achieved. Furthermore, we analyze mean contention time in output contention process and mean packet delay in output buffer. Our studies indicate that the output contention process can be modeled by a B I /D/B/N queueing process and the output buffer can be modeled by a G [X] /D/1/B queueing process. Performance of TWCs in buffering packet switch is extensively studied by means of numerical simulations.

Stochastic modelling of random early detection based congestion control mechanism for bursty and correlated traffic

With the rapid development of the Internet, the control of traffic congestion has become one of the most critical issues that must be confronted by the users. It is also a major challenge to researchers in the field of performance modelling. The paper presents a discrete-time stochastic queueing model for the performance evaluation of the active queue management (AQM) based congestion control mechanism called random early detection (RED) using a two-state Markov-modulated Bernoulli arrival process (MMBP-2) as the traffic source. A new analytical framework is proposed and a two-dimensional discrete-time Markov chain is introduced to model the RED mechanism. This mechanism takes into account the reduction of the incoming traffic arrival rate due to packets dropped probabilistically with the drop probability increasing linearly with the system contents. The analytical evaluation of the queue considered could be of interest for modelling the performance of the RED mechanism for the Internet traffic with short range dependent (SRD) traffic characteristics. The mean system occupancy, mean packet delay, probability of packet loss and system throughput are computed from the analytical model for a dropping policy, which is a function of the thresholds and maximum drop probability. The numerical results clearly demonstrate how different threshold settings can provide different tradeoffs between loss probability and delay to suit different service requirements. The effects of input parameters on a selected set of performance metrics, burstiness and correlations for the arrival process are also studied.

Soft QoS provisioning using the token bank fair queuing scheduling algorithm

Future-generation wireless packet networks will support multimedia applications with diverse QoS requirements. Much of the research on scheduling algorithms has been focused on hard QoS provisioning of integrated services. Although these algorithms give hard delay bounds, their stringent requirements sacrifice the potential statistical multiplexing performance and flexibility of the packet-switched network. Furthermore, the complexities of the algorithms often make them impractical for wireless networks. There is a need to develop a packet scheduling scheme for wireless packet-switched networks that provides soft QoS guarantees for heterogeneous traffic, and is also simple to implement and manage. This article proposes token bank fair queuing (TBFQ), a soft scheduling algorithm that possesses these qualities. This algorithm is work-conserving and has a complexity of O(1). We focus on packet scheduling on a reservation-based TDMA/TDD wireless channel to service integrated real-time traffic. The TBFQ scheduling mechanism integrates the policing and servicing functions, and keeps track of the usage of each connection. We address the impact of TBFQ on mean packet delay, violation probability, and bandwidth utilization. We also demonstrate that due to its soft provisioning capabilities, the TBFQ performs rather well even when traffic conditions deviate from the established contracts.

Virtual private network bandwidth management with traffic prediction

Dynamic link resizing is an attractive approach for resource management in virtual private networks (VPNs) serving modern real-time and multimedia traffic. In this paper, we assess the use of linear traffic predictors to dynamically resize the bandwidth of VPN links. We present the results of performance comparisons of three predictors: Gaussian, auto-regressive moving average (ARMA) and fractional auto-regressive integrated moving average (fARIMA). The comparisons are based on the mean packet delay, the variance of the packet delay, and the buffer requirements. Guided by our performance tests, we propose and evaluate a new predictor for link resizing: linear predictor with dynamic error compensation (L-PREDEC). Our performance tests show that L-PREDEC works better than Gaussian, ARMA and fARIMA in terms of the three metrics listed above. The benefit of L-PREDEC over the Gaussian predictor is demonstrated in two configurations: a common queue with aggregate link resizing and multiple queues with separate link resizing. In both configurations, L-PREDEC has consistently achieved better multiplexing gain and higher bandwidth utilization than its Gaussian counterpart.

Design and Analysis of a Channel Access Protocol for WDM-Based Single-Hop Optical Networks*

We propose a channel access protocol for single-hop wavelength division multiplexing (WDM) optical networks. Each node is equipped with a fixed-tuned transmitter, a tunable transmitter, a fixed-tuned receiver, and a tunable receiver. The proposed protocol alleviates the drawbacks of a previous protocol [1], e.g., invalid data transmissions that follows receiver collisions and possible acknowledgment packet collisions with header/data packets, while retaining many advantages. As a result, the network performance in terms of throughput and packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the proposed protocol, and are validated through event-driven simulation. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Through numerical results and simulation studies, we show that the proposed protocol achieves better channel utilization and incurs lower packet delays.