Jelena V. Misic

Performance Analysis of Cloud Computing Centers Using M/G/m/m+r Queuing Systems

Successful development of cloud computing paradigm necessitates accurate performance evaluation of cloud data centers. As exact modeling of cloud centers is not feasible due to the nature of cloud centers and diversity of user requests, we describe a novel approximate analytical model for performance evaluation of cloud server farms and solve it to obtain accurate estimation of the complete probability distribution of the request response time and other important performance indicators. The model allows cloud operators to determine the relationship between the number of servers and input buffer size, on one side, and the performance indicators such as mean number of tasks in the system, blocking probability, and probability that a task will obtain immediate service, on the other.

Performance of a beacon enabled IEEE 802.15.4 cluster with downlink and uplink traffic

The performance of an IEEE 802.15.4 compliant network operating in the beacon enabled mode with both downlink and uplink traffic is analyzed through discrete time Markov chains and the theory of M/G/1 queues. The model considers acknowledged transmissions and includes the impact of different network and traffic parameters such as the packet arrival rate, packet size, inactive period between the beacons, and the number of stations. We investigate the nonsaturation region and outline the conditions under which the network abruptly goes to saturation. The analysis of stability of the network queues shows that the stability of the downlink queue at the coordinator is the most critical for network operation. Due to the abruptness with which the switch from nonsaturation to saturation occurs, the network operating point has to be carefully chosen according to the volume of downlink traffic. Furthermore, our model shows that certain features prescribed by the standard actually limit the performance of 802.15.4 networks.

Vehicular telematics over heterogeneous wireless networks: A survey

This article presents a survey on vehicular telematics over heterogeneous wireless networks. An advanced heterogeneous vehicular network (AHVN) architecture is outlined which uses multiple access technologies and multiple radios in a collaborative manner. The challenges in designing the essential functional components of AHVN and the corresponding protocols (for radio link control, routing, congestion control, security and privacy, and application development) are discussed and the related work in the literature are reviewed. The open research challenges and several avenues for future research on vehicular telematics over heterogeneous wireless access networks are outlined.

The impact of MAC parameters on the performance of 802.15.4 PAN

The operation of a personal area network, operating under the IEEE Standard 802.15.4 in the beacon enabled mode, is analyzed using the theory of discrete time Markov chains and M/G/1/K queues. The model includes the impact of different parameters such as packet arrival rate, number of stations, stations buffer size, packet size, and inactive period between the beacons. We have derived several important performance parameters such as probability of access, probability that medium is idle, queue length distribution in the device, and probability distribution of the packet service time. Some important conclusions regarding the implementation of 802.15.4 networks and compatible network devices are outlined.

Performance of IEEE 802.15.4 beacon enabled PAN with uplink transmissions in non-saturation mode - access delay for finite buffers

In this work, we derive the probability distribution of access delay and calculate throughput of a personal area network operating under the IEEE standard 802.15.4 in the beacon enabled mode. We model the network using the theory of discrete time Markov chains and M/G/1/K queues. The model considers acknowledged uplink transmission in non-saturation mode, and includes the impact of different parameters such as packet arrival rate, number of stations, the finite size of individual node buffers, packet size, and inactive period between the beacons. Our model also captures the problem of congestion at the beginning of the superframe due to multiple transmissions delayed from the previous superframe. The results show that average access delays, even for small buffer sizes, may be quite high if the throughput exceeds 50%, which can seriously affect applications with delay bounds. Values of throughput larger than 50% can be achieved at the expense of larger buffer sizes, which imposes implementation problems on devices with small memory resources.

A Fine-Grained Performance Model of Cloud Computing Centers

Accurate performance evaluation of cloud computing resources is a necessary prerequisite for ensuring that quality of service parameters remain within agreed limits. In this paper, we employ both the analytical and simulation modeling to addresses the complexity of cloud computing systems. Analytical model is comprised of distinct functional submodels, the results of which are combined in an iterative manner to obtain the solution with required accuracy. Our models incorporate the important features of cloud centers such as batch arrival of user requests, resource virtualization, and realistic servicing steps, to obtain important performance metrics such as task blocking probability and total waiting time incurred on user requests. Also, our results reveal important insights for capacity planning to control delay of servicing users requests.

Modeling Bluetooth piconet performance

The performance of a single Bluetooth piconet is analyzed using the theory of M/G/1 queues with vacations. Analytical results for probability distributions of packet access time and service cycle time are derived. Two scheduling policies are modeled and compared: exhaustive service was found to perform better, but limited service does not incur the risk of starvation. A hybrid scheme known as k-limited scheduling is shown to provide a reasonable tradeoff between performance and fairness. Results were confirmed through simulations.

Performance Characterization for IEEE 802.11p Network With Single Channel Devices

In this paper, we investigate the performance of networks built from single-channel devices that use wireless access in vehicular environment protocols. We consider several traffic combinations, each of which presents a mix of traffic classes, over control and service channels. Our results show that time switching between the channels causes synchronization of backoff processes, which increases the frame collision probability, in particular for small sizes of contention windows. We also evaluate the impact of the interruption of the backoff process by inactive channel time, which gives rise to a probability distribution with repeated tails and a coefficient of variation larger than 1. Our model can also be used to evaluate different sets of enhanced distributed channel access parameters and to select the channel duty cycle according to the policy of the network operator.

Performance analysis of IEEE 802.15.6 under saturation condition and error-prone channel

Due to lack of an appropriate wireless technology which satisfies all the requirements of Wireless Body Area Networks (WBANs) the IEEE 802.15.6 Task Group introduced the IEEE 802.15.6 communication standard optimized for low power devices and operation on, in or around the human body. In this work we develop an analytical model for performance evaluation of an IEEE 802.15.6-based WBAN under saturation condition and error prone channel. We model the backoff procedure as specified in the standard employing a probabilistic approach. We validate results of the analytical model with a simulation model. Our results indicate that under saturation condition the medium is mostly utilized by the nodes with highest priority while other user priorities are starving.

Access delay for nodes with finite buffers in IEEE 802.15.4 beacon enabled PAN with uplink transmissions

In this work we analyze the performance of a personal area network operating under the IEEE Standard 802.15.4 in the beacon enabled mode, and derive the probability distribution of packet access delay and calculate the throughput. We assume that the network is operating in non-saturation mode and that the nodes have finite buffers. We model the operation of the PAN using the theory of discrete time Markov chains and M/G/1/K queues. The model considers acknowledged uplink transmission and includes the impact of different parameters such as packet arrival rate, number of stations, stations buffer size, packet size, and inactive period between the beacons. The model also captures the problem of congestion at the beginning of the superframe due to multiple transmissions being delayed from the previous superframe, and we propose a correction to the standard in order to avoid this problem. In order to achieve acceptable access delays and small blocking probability at the buffer (which has to be small), PAN must be operated at throughput less than 50%, which can be achieved by restricting the number of the nodes in the PAN, or by reducing the packet arrival rates at the nodes.