Dong Hwan Han

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 MAC layer protocols in the IEEE 802.11 wireless LAN

In recent years, WLANs (Wireless Local Area Networks) based on the IEEE 802.11 standard have been taken a growing interest and developed widely all over the world. CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocols are the most popular MAC (Medium Access Control) protocols for WLANs. The performance of CSMA/CA protocols over wireless channels has been investigated over the past years. In this paper, we obtain the probability distribution function of the MAC layer packet service time, and we present the comprehensive performance analysis of IEEE 802.11 MAC protocol by investigating the queue dynamics of a wireless station based on the MAC layer packet service time. We adopt an MMPP(Markov Modulated Poisson Process) as the input traffic model that describes well the bursty nature of Internet traffic. The analysis on the throughput and the delay performance has been carried out by using the MMPP/G/1/K queueing model. We have some numerical results that represent the system throughput and the queue dynamics including the mean packet waiting time and packet blocking probability.

Queueing Analysis of IEEE 802.11 MAC Protocol in Wireless LAN

In this paper, we present the performance analysis of IEEE 802.11 MAC(Medium Access Control) protocol by investigating the queue dynamics of a wireless station based on the general probability distribution of packet sizes. We use the MMPP(Markov Modulated Poison Process) as the input traffic model well describing the bursty nature of Internet traffic. Thus we have the MMPP/G/1/K queueing model with the MAC layer service time to analyze the throughput and the delay performance of IEEE 802.11 MAC protocol in wireless LAN.We take some numerical examples for the queue dynamics including the mean packet delay and the packet blocking probability.

Packet delay analysis of dynamic bandwidth allocation scheme in an ethernet PON

In this paper, we deal with the packet delay of a dynamic bandwidth allocation(DBA) scheme in an Ethernet passive optical network(EPON). We focus on the interleaved polling system with a gated service discipline. On the access side, input traffic may be aggregated from a number of users. So we assume that input packets arrive at an optical network unit(ONU) according to Poisson process. We use a continuous time queueing model in order to find the mean waiting time of an arbitrary packet. We give some numerical results to investigate the delay performances for the symmetric polling system with statistically identical stations.

Performance analysis of DBA scheme with interleaved polling algorithm in an Ethernet PON

We investigate the mean queue length and the mean packet delay of a dynamic bandwidth allocation (DBA) scheme in an Ethernet passive optical network (EPON). We focus on the interleaved polling system with a gated service discipline. We assume that input packets arrive at an optical network unit (ONU) according to Poisson process. We use a continuous time queueing model in order to find the queue length distribution of the gated interleaved polling system with the first stage input queue and the second stage transmission queue. We give some numerical results to show the mean queue lengths and mean packet delays for the symmetric polling system.

Performance analysis of an AAL multiplexer with dynamic bandwidth allocation in an IP/ATM environment

In this paper, we present a discrete-time queueing model with a Markov modulated batch Bernoulli process (MMBBP) as a bursty input traffic model of internet protocol packets in order to investigate the performance of a ATM adaptation layer (AAL) multiplexer with a finite buffer and a threshold-based dynamic bandwidth allocation scheme (DBAS): As a deterministic service time, we use the segmentation processing time devoted to a cell payload in the AAL multiplexer. This service time consists of several slot times and varies in line with threshold levels of the buffer contents. In an MMBBP process, the arrivals during a slot time occur as batch Bernoulli processes with a general distribution of batch sizes varying according to the phases of a Markov chain. We obtain the loss probability and the mean delay of an arbitrary packet. We present some numerical results to show the effects of the burstiness and thresholds on the performance of the AAL multiplexer with a DBAS.

Effect of the number of active sources on ABR buffer size

Rate-based flow control plays an important role for efficient traffic management of Available Bit Rate(ABR) services. We deal with the problem of the buffer dimension for rate-based ABR control. In this paper, we analyze the Allowed Cell Rate(ACR) of a source and the queue size in a steady state. First, we investigate the effect of the number of active sources on the behavior of the ACR and the maximum queue size. Reflecting the effect of this real scenes, we determine the optimal buffer size and buffer threshold. Furthermore, our analytic results are compared with the case when the effect of the number of active sources is disregarded.

G/M/1 queues with delayed vacations

We considerG/M/1 queues with multiple vacation discipline, where at the end of every busy period the server stays idle in the system for a period of time called changeover time and then follows a vacation if there is no arrival during the changeover time. The vacation time has a hyperexponential distribution. By using the methods of the shift operator and supplementary variable, we explicitly obtain the queue length probabilities at arrival time points and arbitrary time points simultaneously.

Development of a Carbon Nanotube Paste for the High-Performance Field Emitters by Using the Simple Ball-Milling Method

The carbon nanotube (CNT) paste was fabricated by a very simple method where the paste composition could be controlled precisely. We have fabricated several types of field emitters from the CNT paste mixture consisting of the thin multi-walled CNT, the nanosized inorganic fillers, the ethyl cellulose binder and the terpineol solvent. The field emission current density was found to be more than 100 mA/cm2 at a field of 2.5 V/μm for the planar-type CNT emitter and ~5 A/cm2 for the tip-type emitter, respectively. We also optimized the filler material in the paste to make the emitter reliable under the high-temperature conditions. The developed CNT paste had good reproducibility and the field emitters made of the paste showed excellent characteristics as the electron sources for the various applications.

Queueing analysis of dynamic bandwidth allocation scheme for IP traffic on ATM networks

In this paper, we present a discrete-time finite queueing model with deterministic service times and an MMBBP (Markov Modulated Batch Bernoulli Process) as a bursty input traffic model of IP packets in order to investigate the performance of a DBAS (Dynamic Bandwidth AllocationScheme) in an ATM/IWU (interworking unit). We assume that the segmentation processing time devoted to each cell requires several slot times in the ATM/IWU. In an MMBBP process,the arrivals during a slot time occur as batch Bernoulli processes with the batch size distributions varying according to the phases of a Markov chain. As performance measures, we obtain the packet loss probability and the mean packet delay of an arbitrary packet. We present some numerical results to show the effects of the service time and burstiness of input traffic on the performance of the presented DBAS.