"A Hidden Semi-Markov Model for Web Workload Self-Similarity," Shun-Zheng Yu, Zhen Liu, Mark S. Squillante, Cathy Honghui Xia, and Li Zhang, Proceedings of 21st IEEE International Performance, Computing, and Communications Conference, p. 65-72, 2002.

Measurements of Web workloads indicate that significant traffic variability is present on a wide range of time scales. Characteristics such as long-range dependence and self-similarity can have a significant impact on the server performance. In this paper, we propose a hidden semi-Markov model (HSMM) to characterize the user request patterns of Web workloads. Hidden semi-Markov models have been well studied and successfully applied to many engineering and scientific problems. The advantage of using a HSMM is its efficient forward-backward algorithms for estimating model parameters to best account for an observed sequence. We show that our proposed HSMM model asymptotically characterizes second order self-similar workloads when some duration distributions of the hidden states are heavy-tailed. A recursive formula is developed for estimating the Hurst parameter of self-similarity. We validate our model and estimation methods with respect to two sets of empirical data (requests per second) collected from two different Web servers. We then use this model to generate self-similar workloads that exhibit the same statistical properties. These measurements show that we can use as few as 4 states together with a simple Poisson process and heavy-tailed Pareto holding time distributions to accurately model the Web workloads considered in this study.

"A Label-switching Packet Forwarding Architecture for Multi-hop Wireless LANs," Arup Acharya, Archan Misra, Sorav Bansal (Stanford University)

Channel speeds for the IEEE 802.11 [2][4] family of standards continue to increase: while the recently proposed 802.11a operates at 54 Mbps, enhanced versions operating at speeds up to 108 Mbps are also under investigation. Such high-speed LAN standards are expected to further increase the popularity of wireless access to the backbone infrastructure and eventually lead to the deployment of multi-hop, wireless networks, where the wired backbone is reachable only via multiple wireless hops. Potential examples of this include in-building wireless networks in malls, hotels and apartment blocks, and community networks where rooftop antennas are used to create an ad-hoc wireless access infrastructure in specific residential communities.
A router in wired network typically requires multiple network interfaces to act as a router or a forwarding node. In an ad-hoc multi-hop wireless network on the other hand, any node with a wireless network interface card can operate as a router or a forwarding node, since it can receive a packet from a neighboring node, do a route lookup based on the packet’s destination IP address, and then transmit the packet to another neighboring node using the same wireless interface. This paper investigates a combined medium access and next-hop address lookup based on fixed length labels (instead of IP addresses), which allows the entire packet forwarding operation to be executed within the wireless NIC without the intervention of the host protocol stack. Medium access schemes to date, such as IEEE 802.11, have been designed implicitly for either receiving or transmitting a packet, but not for a forwarding operation, i.e. receiving a packet from an upstream node and then immediately transmitting the packet to a downstream node as an atomic channel access operation. This paper proposes a MAC protocol for packet forwarding in multi-hop wireless networks. The proposed protocol builds on the IEEE 802.11 DCF MAC using RTS/CTS and uses MPLS like labels in the control packets (RTS/CTS) to allow the forwarding node to determine the next hop node while contending for the channel. The throughput of this protocol is compared with 802.11 DCF MAC through simulation.

"An Overview of the Bluetooth Wireless Technology," Chatschik Bisdikian, IEEE Communications Magazine, Vol 39, No 12, pp 86-94, December 2001.

This paper won the Best Tutorial paper award given to an outstanding tutorial paper published in any communications Society publication in 2001. Dr. Bisdikian is an authority on Bluetooth wireless technology. He is involved with the development of the Bluetooth specification and serves as the vice-chair of the 802.15.1 task group that produced the IEEE 802.15.1 standard for WPANs. The paper provides an excellent introduction to the Bluetooth technology accessible to a wide audience and provide references for a deeper study of the field.

"Inferring Client Response Time at the Web Server," David P. Olshefski, Jason Nieh, and Dakshi Agrawal, Performance Evaluation Review, vol. 30, no. 1, p. 160-71, 2002, 06/2002.