Yutae Lee

Performance analysis of HomePlug 1.0 MAC with CSMA/CA

As demands for data communications among home/personal devices in home environments increase, various types of home-networking technologies have appeared. Among them, power line communication is one of the most promising wired home-networking technologies, because the existing power line facilities can be utilized for data transmission without deploying any new physical links. HomePlug 1.0 is the most popular power line communication technology, which has been standardized by the HomePlug power line alliance, and attempts to mitigate the effect of time- and frequency-varying channels by enhanced modulation and channel coding. Although HomePlug 1.0 has undergone field trials and simulations, its analytic model and performance was only conducted for throughput under saturation conditions. We propose a new analytic model to evaluate MAC throughput and delay of HomePlug 1.0 both under saturation and under normal traffic conditions. We verify our proposed model via simulations and evaluate the performance of HomePlug 1.0.

Performance Analysis of IEEE 802.11 DCF under Nonsaturation Condition

Carrier sense multiple access with collision avoidance (CSMA/CA) methods are considered to be attractive MAC protocols for wireless LANs. IEEE 802.11 distributed coordination function (DCF) is a random channel access scheme based on CSMA/CA method and the binary slotted exponential backoff procedure to reduce the packet collision. In this paper, we propose a new analytical model for a nonsaturated IEEE 802.11 DCF network and evaluate its performance. We verify our model using simulations and show that our results agree with the simulations.

Performance Evaluation of an Enhanced GDCF for IEEE 802.11

In this letter, we propose an enhanced gentle distributed coordination function (GDCF), which is a simple and effective collision resolution mechanism, to improve the performance of IEEE 802.11 DCF. We compare performance of the enhanced GDCF with that of the legacy DCF and the conventional GDCF via analysis and simulations. The enhanced GDCF introduces a new counter to check the number of consecutively successful transmissions, and the maximum permitted values of the counter differ for different backoff stages. The proposed GDCF is shown to have performance superior to that of the conventional GDCF for various combinations of contending stations and frame length.

A New Analytic Method for IEEE 802.11 Distributed Coordination Function

In this paper, we consider a network of N identical IEEE 802.11 DCF (Distributed Coordination Function) terminals with RTS/CTS mechanism, each of which is assumed to be saturated. For performance analysis, we propose a simple and efficient mathematical model to derive the statistical characteristics of the network such as the inter-transmission time of packets in the network and the service time (the inter-transmission time of successful packet transmissions) of the network. Numerical results and simulations are provided to validate the accuracy of our model and to study the performance of the IEEE 802.11 DCF network.

Discrete-Time Bulk Queueing System with Variable Service Capacity Depending on Previous Service Time

This paper considers a discrete-time bulk-arrival bulk-service queueing system nwith variable service capacity, where the service capacity varies depending on nthe previous service time. Using the supplementary variable method and the ngenerating function technique, we obtain the queue length distributions at arbitrary nslot boundaries and service completion epochs.

Performance Evaluation of an Enhanced GDCF under Normal Traffic Condition

IEEE 802.11 is one of the most interesting technology in wireless local area networks. In this paper, we investigate performance of IEEE 802.11 DCF (distributed coordination function) and an enhanced GDCF (gentle DCF) in terms of throughput and MAC delay under normal traffic condition. We also present an analytical model for the enhanced GDCF MAC delay under saturation condition. From the results, the performance of the enhanced GDCF is nearly same as that of conventional DCF for light traffic load, but the enhanced GDCF yields better performance than the conventional DCF for heavy traffic load.

Relationship between the buffer threshold and the link utilization in ABR services

Rate-based flow controls play an important role in traffic management of Available Bit Rate (ABR) services. The performance of a rate-based ABR flow control is investigated. In a steady state the evolution of both the Allowed Cell Rate (ACR) and the length of queue within a switch is classified into three cases as the number of active sources varies. In each case, both the link utilization and the maximum queue length are derived. Then, for a given buffer threshold, we determine both the link utilization and the buffer size achieving zero cell loss. Numerical results show the effect of the threshold on the buffer size and the link utilization.