Papers by shao-cheng Wang
29th Annual IEEE International Conference on Local Computer Networks
We propose ELECTION, a new sleep scheduling scheme that adaptively schedules the sleep cycles of ... more We propose ELECTION, a new sleep scheduling scheme that adaptively schedules the sleep cycles of both communication radios and sensors in wireless active sensor networks. Taking advantage of spatial and temporal correlations in the underlying physical phenomenon, our scheme controls sleeping schedules of radios and sensors, and adaptively meets the energy efficiency, latency and responsiveness needs of applications. During the normal phase of operation, sensors take samples of the environment once at each wakeup time, and based on the perceived environment they adapt their sleep cycles. When an abnormality is perceived from the sampled data, sensors communicate with their neighbors to form a cluster and report to the base station. Analysis and simulation results show that ELECTION outperforms existing protocols significantly in terms of energy savings as well as delay and responsiveness.
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286)
The recording of gastric activities by surface electrodes is called electrogastrography(EGG). It ... more The recording of gastric activities by surface electrodes is called electrogastrography(EGG). It should be carefully filtered and amplified because of its ultra-low frequency, tiny and noisy signal. A new system, including a signal acquisition device and Windows-based software, was designed to record and analyze the EGG signal. Many volunteers and patients have been successfully tested by the system.
Performance evaluations for hybrid IEEE 802.1 lb and 802.11g wireless networks
PCCC 2005. 24th IEEE International Performance, Computing, and Communications Conference, 2005.
background traffic-aware rate adaptation for IEEE 802.11: implementation and test-bed experimental results
ACM SIGMOBILE Mobile Computing and Communications Review, Jan 21, 2010
IEEE 802.11-based devices employ rate adaptation algorithms to dynamically switch data rates to a... more IEEE 802.11-based devices employ rate adaptation algorithms to dynamically switch data rates to accommodate the fluctuating wireless channel conditions. In this paper, we design and implement a new Background traffic aware rate adaptation algorithm (BEWARE) in Linux-based device driver. The proposed rate adaptation algorithm makes rate decisions by on-the-fly estimating the expected packet transmission time which captures both current wireless channel and background traffic conditions. Our test-bed experiment ...
Proceeding of ACM MOBICOM, San Diego, CA, Oct 1, 2003
Short-lived small transfers such as resource discovery and queries are likely to constitute a sig... more Short-lived small transfers such as resource discovery and queries are likely to constitute a significant portion of the traffic in future ad hoc networks. In earlier work on ad hoc routing, randomly assigned long-lived connections have been studied. In this study we show that small transfers stress the route setup phase (vs. maintenance/repair phase) and exhibit significant different behavior than the commonlystudied long-lived transfers. Through extensive simulations, we attribute such differences to “cache” performance. A firstorder ...
Proceedings. 2006 31st IEEE Conference on Local Computer Networks, 2006
Recent advance in IEEE 802.11 based standard has pushed the wireless bandwidth up to 600Mbps whil... more Recent advance in IEEE 802.11 based standard has pushed the wireless bandwidth up to 600Mbps while keeping the same wireless medium access control (MAC) schemes for full backward compatibility. However, it has been shown that the inefficient protocol overhead casts a theoretical throughput upper limit and delay lower limit for the IEEE 802.11 based protocols, even the wireless data rate goes to infinitely high. Such limits are important to understand the bottleneck of the current technology and develop insight for protocol performance improvements. This paper uses a queuing system approach to extend the discussions of IEEE 802.11 protocol throughput and delay limits to the situation that arbitrary non-saturated background traffic is present in the network. We derive analytical models to quantify the limits for Distributed Coordination Function (DCF) of legacy 802.11a/b/g and Enhanced Distributed Coordination Access (EDCA) of IEEE 802.11e. We find such limits are functions of the underlying MAC layer backoff parameters and algorithms, and are highly dependent on the load that background traffic injects into the network. Surprisingly, depending on the rate of arrival traffic, the packet delay limit may become unbounded such that no delay sensitive services can be operated under such condition. Moreover, we also discuss the effects of different frame aggregation schemes on the performance limits when data rate is infinite. The developed model and analysis provide a comprehensive understanding of the performance limitations for IEEE 802.11 MAC, and are useful in gauging the expected QoS for the purposes such as admission control.
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
Telemedicine is a rapidly growing area and recently there are studies devoted to prehospital care... more Telemedicine is a rapidly growing area and recently there are studies devoted to prehospital care of patients in emergency cases. Here we present a GSM-network-based, function-integrated telemonitoring system to give first aid before reaching the hospital.
A speech controlled artificial limb based on DSP chip
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286)
A speech signal pattern recognition DSP-based system is constructed for real-time control of arti... more A speech signal pattern recognition DSP-based system is constructed for real-time control of artificial limb through precise identification of speech and speech command. The portable DSP-based system provides a more effective method to provide multiple control commands than the electromyographic signals from the amputation stump or residual limb. The traditional prosthetic arm can not achieve many complex actions because the EMG of the residual limb is hard to detach from the many different control signals. Goals of multiple command recognition and low cost were achieved by using a portable DSP-based system
IEEE/ACM Transactions on Networking, 2011
IEEE 802.11-based devices employ rate adaptation algorithms to dynamically switch data rates to a... more IEEE 802.11-based devices employ rate adaptation algorithms to dynamically switch data rates to accommodate the fluctuating wireless channel conditions. Many studies observed that, when there are other stations transmitting in the network, existing rate adaptation performance degrades significantly due to the inability of differentiating losses between wireless noise and contention collisions. They proposed to exploit optional RTS frames to isolate the wireless losses from collision losses, and thus improve rate adaptation performance. In this paper, we conduct a systematic evaluation on the effectiveness of various existing rate adaptation algorithms and related proposals for loss differentiations, with multiple stations transmitting background traffic in the network. Our main contributions are twofold. Firstly, we observe that most existing rate adaptations do not perform well in background traffic scenarios. In addition, our study reveals that RTS-based loss differentiation schemes can mislead the rate adaptation algorithms to persist on using similar data rate combinations regardless of background traffic level, thus result in performance penalty in certain scenarios. The fundamental challenge is that rate adaptation must dynamically adjust the rate selection decision objectives with respect to different background traffic levels. Secondly, we design a new Background traffic aware rate adaptation algorithm (BEWARE) that addresses the above challenge. BEWARE uses a mathematical model to calculate on-the-fly the expected packet transmission time based on current wireless channel and background traffic conditions. Our simulation results show that BEWARE outperforms other rate adaptation algorithms without RTS loss differentiation by up to 250% and with RTS by up to 25% in throughput.
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Papers by shao-cheng Wang