A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environment...A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load （think time is ls） the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.展开更多
为了节约都市绿地灌溉用水,提高水资源利用率,该文设计了一套基于ATmega128 MCU、嵌入式操作系统、全球移动通讯系统GSM、通用分组无线业务GPRS(General Packet Radio Service)的都市绿地远程精准灌溉控制系统。该系统实现了网络化、智...为了节约都市绿地灌溉用水,提高水资源利用率,该文设计了一套基于ATmega128 MCU、嵌入式操作系统、全球移动通讯系统GSM、通用分组无线业务GPRS(General Packet Radio Service)的都市绿地远程精准灌溉控制系统。该系统实现了网络化、智能化的土壤墒情的实时检测,以及历史数据查询、土壤信息及灌溉信息的图表显示,用水报表生成,根据地势、植被不同,生成不同灌溉策略等功能。采用GSM/GPRS自主切换技术,结合现代嵌入式实时操作系统μC/OS,进一步提高了系统的可靠性。该系统能根据植物的土壤含水率阈值和生物需水量实现精准节水灌溉。初步试验证明,该系统数据传输可靠性高,节水效果显著。展开更多
基金Project(20030533011)supported by the National Research Foundation for the Doctoral Program of Higher Education of China
文摘A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load （think time is ls） the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.
文摘为了节约都市绿地灌溉用水,提高水资源利用率,该文设计了一套基于ATmega128 MCU、嵌入式操作系统、全球移动通讯系统GSM、通用分组无线业务GPRS(General Packet Radio Service)的都市绿地远程精准灌溉控制系统。该系统实现了网络化、智能化的土壤墒情的实时检测,以及历史数据查询、土壤信息及灌溉信息的图表显示,用水报表生成,根据地势、植被不同,生成不同灌溉策略等功能。采用GSM/GPRS自主切换技术,结合现代嵌入式实时操作系统μC/OS,进一步提高了系统的可靠性。该系统能根据植物的土壤含水率阈值和生物需水量实现精准节水灌溉。初步试验证明,该系统数据传输可靠性高,节水效果显著。
