Effective scheduling algorithm for on-demand XML data broadcasts in wireless environments

The organization of data on wireless channels, which aims to reduce the access time of mobile clients, is a key problem in data broadcasts. Many scheduling algorithms have been designed to organize flat data on air. However, how to effectively schedule semi-structured information such as XML data on wireless channels is still a challenge. In this paper, we firstly propose a novel method to greatly reduce the tuning time by splitting query results into XML snippets and to achieve better access efficiency by combining similar ones. Then we analyze the data broadcast scheduling problem of on-demand XML data broadcasts and define the efficiency of a data item. Based on the definition, a Least Efficient Last (LEL) scheduling algorithm is also devised to effectively organize XML data on wireless channels. Finally, we study the performance of our algorithms through extensive experiments. The results show that our scheduling algorithms can reduce both access time and tuning time signifcantly when compared with existing work

Veränderte autonome Funktion bei Patienten mit obstruktiver Schlafapnoe im Wachzustand

Background: Patients with obstructive sleep apnea (OSA) show impaired cardiac autonomic function with heterogeneous profiles of heart rate variability (HRV) during sleep-wake states. However, the effect of OSA and its severity on autonomic modulation assessed by HRV during the wake period in a large multicenter clinical cohort is unclear. Methods: A total of 1247 participants (426 non-OSA controls and 821 OSA patients, according to apnea-hypopnea index≥5) were globally recruited from the Sleep Apnea Global Interdisciplinary Consortium. HRV measures were computed from 5-minute ECG data in wake status with relaxed tidal breathing prior to the sleep onset, using time-domain, frequency-domain and non-linear approaches. Differences in HRV measurements were estimated among groups using analysis of covariance, adjusted for age, gender, body mass index, race/ethnicity, comorbidities and sites. Results: OSA patients exhibited significantly reduced time-domain variations (SDNN, SDANN1, RMSSD, pNN50) and less complexity of cardiac rhythms (Shannon entropy, Fwshannon, Forbword) compared to non-OSA subjects. Those with severe OSA had considerably lower HRV compared to in comparison to other groups, both in time-domain and non-linear measurements. Compared to patients with OSA, those with severe OSA had reduced HRV based on SDNN (adjusted mean [95% CI]: 37.40 [34.55, 40.25] vs.46.19 [43.77, 48.60] ms; p<0.0001), SDANN1 (17.98.0 [15.87, 20.10] vs. 22.77 [20.97, 24.56] ms; p<0.0001), RMSSD (21.51 [19.59, 23.42] vs.27.98 [26.35, 29.60] ms; p<0.0001), pNN50 (5.1% [3.7%, 6.5%] vs. 9.2% [8.0%, 10.4%]; p=0.0001), Shannon entropy (1.8 [1.8, 1.9] vs. 2.0 [2.0, 2.1]; p<0.0001), Fwshannon 2.7 [2.6, 2.7] and Forbword (37 [35, 38] vs. 33[32, 34]; p=0.0001). There were no significant differences in overall frequency-domain metrics. Among obese patients, there is an increase in sympathetic tone in patients with severe OSA with higher LF/HF ratio compared to those without OSA (4.2 vs. 2.7; p = 0.009). Conclusions: HRV is significant correlative with OSA severity. OSA patients show reduced HRV patterns during pre-sleep wakefulness compared to individuals without OSA, especially patients with severe OSA having significantly decreased time-domain HRV metrics and less complex non-linear HRV dynamics. Only obese OSA patients show enhanced sympathetic activity with increased LF and LF/HF. Thus, HRV could be a promising tool to investigate autonomic modulation and cardiovascular pathophysiology in patients with OSA.Patienten mit obstruktiver Schlafapnoe (OSA) zeigen eine eingeschränkte kardiale autonome Funktion mit heterogenen Profilen der Herzratenvariabilität (HRV) im Wachzustand und im Schlaf. Die Wirkung von OSA und ihrer Schwere auf die autonome Modulation, die durch HRV während der Wachphase in einer großen multizentrischen klinischen Kohorte bewertet wurde, sind jedoch unklar. Methoden: Insgesamt 1247 Probanden (426 ohne OSA und 821 Patienten mit OSA, basierend auf dem Apnoe-Hypopnoe-Index ≥ 5) wurden weltweit aus einem globalen interdisziplinären Konsortium für Schlafapnoe rekrutiert (the Sleep Apnea Global Interdisciplinary Consortium, SAGIC). Die HRV-Parameter wurden während einer Periode von 5-minütigen Wachheit mit Spontanatmung vor der eigentlicher Schlafstudie unter Verwendung von Zeitbasis-, Frequenzbasis- und nichtlinearen Methoden berechnet. Unterschiede in den HRV-Parametern wurden zwischen den Gruppen unter Verwendung von Kovarianzanalysen bewertet, wobei Alter, Geschlecht, Body-Mass-Index, Ethnizität, Komorbiditäten und Standort des Schlaflabors kontrolliert wurden. Ergebnisse: Patienten mit OSA zeigten im Vergleich zu Personen ohne eine OSA signifikant geringere Variationen der Parameter in der Zeitbasis (SDNN, SDANN1, RMSSD, pNN50) und eine geringere Komplexität der Herzschläge (Shannon-Entropie, Fwshannon, Forbword). Diejenigen mit schwerer OSA hatten im Vergleich zu allen anderen Gruppen eine auffallend reduzierte HRV, sowohl in den Zeitbasis als auch in nichtlinearen Parametern. Im Vergleich zu Patienten ohne OSA hatten Patienten mit schwerer OSA eine niedrigere HRV basierend auf SDNN (adjustierter Mittelwert [95% CI]: 37.40 [34.55, 40.25] vs.46.19 [43.77, 48.60] ms; p<0.0001), SDANN1 (17.98.0 [15.87, 20.10] vs. 22.77 [20.97, 24.56] ms; p<0.0001), RMSSD (21.51 [19.59, 23.42] vs.27.98 [26.35, 29.60] ms; p<0.0001), pNN50 (5.1% [3.7%, 6.5%] vs. 9.2% [8.0%, 10.4%]; p=0.0001), Shannon entropy (1.8 [1.8, 1.9] vs. 2.0 [2.0, 2.1]; p<0.0001), Fwshannon 2.7 [2.6, 2.7] and Forbword (37 [35, 38] vs. 33[32, 34]; p=0.0001). Bei Ergebnissen der Methoden im Frequenzbereich wurden insgesamt keine signifikanten Unterschiede gefunden. Bei adipösen Patienten gibt es einen Anstieg des sympathischen Tonus bei schwerer OSA mit einem höheren LF/HF-Verhältnis im Vergleich zu adipösen nicht-OSA-Patienten (4,2 vs. 2,7; p = 0,009). Schlussfolgerungen: Die HRV korreliert signifikant mit dem Schweregrad der OSA. OSA Patienten zeigen im Wachzustand reduzierte HRV-Messwerte im Vergleich zu Personen ohne OSA, insbesondere Patienten mit schwerer OSA zeigen deutlich verringerten HRV-Messwerten in der Zeitbasis und weniger komplexitatin parametern der nichtlinearen HRV-Dynamik. Nur adipöse OSA-Patienten zeigen eine sympathische Hyperaktivität mit erhöhtem LF und LF/HF. Somit könnte HRV zusätzliche Informationen über die autonome Modulation und die kardiovaskuläre Physiologie bei OSA-Patienten liefern

Utilizing ZigBee Technology for More Resource-efficient Wireless Networking

Wireless networks have been an essential part of communication in our daily life. Targeted at different applications, a variety of wireless networks have emerged. Due to constrained resources for wireless communications, challenges arise but are not fully addressed. Featured by low cost and low power, ZigBee technology has been developed for years. As the ZigBee technology becomes more and more mature, low-cost embedded ZigBee interfaces have been available off the shelf and their sizes are becoming smaller and smaller. It will not be surprising to see the ZigBee interface commonly embedded in mobile devices in the near future. Motivated by this trend, we propose to leverage the ZigBee technology to improve existing wireless networks. In this dissertation, we classify wireless networks into three categories (i.e., infrastructure-based, infrastructure-less and hybrid networks), and investigate each with a representative network. Practical schemes are designed with the major objective of improving resource efficiency for wireless networking through utilizing ZigBee technology. Extensive simulation and experiment results have demonstrated that network performance can be improved significantly in terms of energy efficiency, throughput, packet delivery delay, etc., by adopting our proposed schemes