宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需...宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需速率多为静态预先设定且为固定值,因此会导致各子载波信噪比存在明显差异性的情况下,系统无法根据业务的不同QoS需求及网络中实时队列长度对所需资源进行自适应调整。抑或缺乏依据当前网络状态的动态调配灵活性,导致通信资源的浪费或通信需求无法满足。文章针对并发多业务的资源分配问题,通过应用层、数据链路层、物理层间的数据映射,建立了跨层资源分配模型。根据应用层电力多业务的QoS需求、数据链路层缓存区内队列长度以及底层物理层子载波和系统功率,将数据分组等待时延以及分组损耗映射为实时/非实时类用户的最低传输速率,进而提出基于效用函数的MAC层用户调度和物理层资源分配算法。最后通过典型电力线信道环境仿真实验发现:所提算法比现有2个电力线载波资源分配算法在多业务并发场景下单用户的吞吐量最高可提升47.62%,分组等待时延缩短37.25%,分组损耗降低72.04%。更好的资源分配使得文章所提算法能够在保证QoS需求情况下,允许更多的用户同时接入系统,有效提升了基于OFDM的宽带电力线载波通信资源利用率。展开更多
The small-cell technology is promising for spectral-efficiency enhancement. However, it usually requires a huge amount of energy consumption. In this paper, queue state information and channel state information are jo...The small-cell technology is promising for spectral-efficiency enhancement. However, it usually requires a huge amount of energy consumption. In this paper, queue state information and channel state information are jointly utilized to minimize the time average of overall energy consumption for a multi-carrier small-cell network, where the inter-cell interference is an intractable problem. Based on the Lyapunov optimization theory, the problem could be solved by dynamically optimizing the problem of user assignment, carrier allocation and power allocation in each time slot. As the optimization problem is NP-hard, we propose a heuristic iteration algorithm to solve it. Numerical results verify that the heuristic algorithm offers an approximate performance as the brute-force algorithm. Moreover, it could bring down the overall energy consumption to different degrees according to the variation of traffic load. Meanwhile, it could achieve the same sum rate as the algorithm which focuses on maximizing system sum rate.展开更多
Purpose： Flail chest （FC） injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being chall...Purpose： Flail chest （FC） injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being challenged by renewed interest in surgical rib fixation. This retrospective epidemiological study sets out to evaluate FC patients, and quantify the natural history of this injury by studying the injury patterns, epidemiology and mortality of patients sustaining FC injuries admitted to a major trauma centre （MTC）. Methods： A retrospective cohort analysis has been conducted at an MTC with full trauma service. All patients （age 〉 16 years） sustaining FC were included. Patient demographics, injury characteristics and inpatient stay information were extracted. Results： Two hundred and ninety-three patients were identified, with a mean injury severity score （ISS） of 28.9 （range 9-75）, average age of 56.1 years （range of 16-100）, and a male predominance （78%）. Road traffic accidents accounted for 45% （n = 132） of injuries, whilst 44% were fall or jump from height （n = 129）. Associated lung contusion was present in 133 patients （45%） while 76% of patients were found to have 5 or more ribs involved in the flail segment （n = 223） with 96% （n = 281 ） having a unilateral FC. Inpatient treatment was required 19.9 days （range 0-150 days） with 59% of patients （n = 173） requiring intensive care unit （ICU） level care for 8.4 days （range 1-63） with 61.8% requiring mechanical ventilation （n = 107） for 10.5 days （range 1-54）, and Z8g underwent rib fixation with rib plates （n = 23）. The mortality rate was found to be 14% （n = 42）. A non-significant trend towards improved outcomes in the conservative group was found when compared with the fixation group; ventilation days （6.94 vs 10.06, p = 0.18） intensive treatment unit （ITU） length of stay （LOS） （12.56 vs 15.53, p = 0.28） and hospital LOS （32.62 vs 35.24, p = 0.69）. Conclusion： This study has successfully described the natural history of flail chest injuries, and has found a nonsignificant trend towards better outcomes with conservative management. With the cohort and management challenges now defined, work on outcome improvement can be targeted. In addition the comnarahility of results to other studies makes collaboration with other MTCs a realistic vrovosal.展开更多
文摘宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需速率多为静态预先设定且为固定值,因此会导致各子载波信噪比存在明显差异性的情况下,系统无法根据业务的不同QoS需求及网络中实时队列长度对所需资源进行自适应调整。抑或缺乏依据当前网络状态的动态调配灵活性,导致通信资源的浪费或通信需求无法满足。文章针对并发多业务的资源分配问题,通过应用层、数据链路层、物理层间的数据映射,建立了跨层资源分配模型。根据应用层电力多业务的QoS需求、数据链路层缓存区内队列长度以及底层物理层子载波和系统功率,将数据分组等待时延以及分组损耗映射为实时/非实时类用户的最低传输速率,进而提出基于效用函数的MAC层用户调度和物理层资源分配算法。最后通过典型电力线信道环境仿真实验发现:所提算法比现有2个电力线载波资源分配算法在多业务并发场景下单用户的吞吐量最高可提升47.62%,分组等待时延缩短37.25%,分组损耗降低72.04%。更好的资源分配使得文章所提算法能够在保证QoS需求情况下,允许更多的用户同时接入系统,有效提升了基于OFDM的宽带电力线载波通信资源利用率。
基金partially supported by National Basic Research Program of China (2013CB329002)National Natural Science Foundation of China (61631013)+6 种基金The National High Technology Research and Development Program of China(2014AA01A703)Science Fund for Creative Research Groups of NSFC (61321061)National Major Project (2017ZX03001011)International Science and Technology Cooperation Program (2014DFT10320)National Science Foundation of China (61701457 \& 61771286)Tsinghua-Qualcomm Joint Research ProgramHuawei Innovation Research Program
文摘The small-cell technology is promising for spectral-efficiency enhancement. However, it usually requires a huge amount of energy consumption. In this paper, queue state information and channel state information are jointly utilized to minimize the time average of overall energy consumption for a multi-carrier small-cell network, where the inter-cell interference is an intractable problem. Based on the Lyapunov optimization theory, the problem could be solved by dynamically optimizing the problem of user assignment, carrier allocation and power allocation in each time slot. As the optimization problem is NP-hard, we propose a heuristic iteration algorithm to solve it. Numerical results verify that the heuristic algorithm offers an approximate performance as the brute-force algorithm. Moreover, it could bring down the overall energy consumption to different degrees according to the variation of traffic load. Meanwhile, it could achieve the same sum rate as the algorithm which focuses on maximizing system sum rate.
文摘Purpose： Flail chest （FC） injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being challenged by renewed interest in surgical rib fixation. This retrospective epidemiological study sets out to evaluate FC patients, and quantify the natural history of this injury by studying the injury patterns, epidemiology and mortality of patients sustaining FC injuries admitted to a major trauma centre （MTC）. Methods： A retrospective cohort analysis has been conducted at an MTC with full trauma service. All patients （age 〉 16 years） sustaining FC were included. Patient demographics, injury characteristics and inpatient stay information were extracted. Results： Two hundred and ninety-three patients were identified, with a mean injury severity score （ISS） of 28.9 （range 9-75）, average age of 56.1 years （range of 16-100）, and a male predominance （78%）. Road traffic accidents accounted for 45% （n = 132） of injuries, whilst 44% were fall or jump from height （n = 129）. Associated lung contusion was present in 133 patients （45%） while 76% of patients were found to have 5 or more ribs involved in the flail segment （n = 223） with 96% （n = 281 ） having a unilateral FC. Inpatient treatment was required 19.9 days （range 0-150 days） with 59% of patients （n = 173） requiring intensive care unit （ICU） level care for 8.4 days （range 1-63） with 61.8% requiring mechanical ventilation （n = 107） for 10.5 days （range 1-54）, and Z8g underwent rib fixation with rib plates （n = 23）. The mortality rate was found to be 14% （n = 42）. A non-significant trend towards improved outcomes in the conservative group was found when compared with the fixation group; ventilation days （6.94 vs 10.06, p = 0.18） intensive treatment unit （ITU） length of stay （LOS） （12.56 vs 15.53, p = 0.28） and hospital LOS （32.62 vs 35.24, p = 0.69）. Conclusion： This study has successfully described the natural history of flail chest injuries, and has found a nonsignificant trend towards better outcomes with conservative management. With the cohort and management challenges now defined, work on outcome improvement can be targeted. In addition the comnarahility of results to other studies makes collaboration with other MTCs a realistic vrovosal.
