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1.
IEEE 802.11 wireless network standard has become one of the most used wireless networking technologies for smart devices as it offers mobility support and low cost deployment. However, these devices deeply rely on the energy provided by their batteries, which results in limited running time. IEEE 802.11 network standard provides stations with carrier sense multiple access with collision avoidance for the medium access. Yet it results in stations to consume an important amount of power. Therefore, minimizing WiFi‐based energy consumption in smart devices has been received substantial attention in both academia and industry. Accordingly, this paper * proposes a novel beacon‐based energy‐efficient collision‐free medium access control protocol for any type of IEEE 802.11 stations, regardless of being stationary or mobile, or having different amount of traffic flow, transmission rates, or traffic types. The proposed scheme is valid for all types of low or wide bandwidth, single or multiuser multiple‐input multiple‐output WLAN channels, such as IEEE 802.11a\b\g\n\ac. In the proposed scheme, energy saving is achieved, enabling stations to transmit on the right time and maintaining stations in the doze state during a predetermined sleep_time interval after each successful frame transmission, by making use of modified control and management frames of the standard IEEE 802.11 protocol. The proposed scheme reduces the probability of collisions and may allow stations to enter the collision‐free state, regardless of the number of stations on the channel and their traffic types. Widespread simulations have been executed to validate the efficiency of the proposed method. The results demonstrate that the proposed method significantly increases overall throughput and reduces power consumption of stations over IEEE 802.11 WLANs. 相似文献
2.
A road side unit (RSU)-coordinated multichannel media access control (MAC) (RMM) protocol was proposed in vehicular ad hoc network,which aimed to improve the transmission efficiency of non-safety messages.Under the coordination of RSU,nodes had more opportunities to make SCH reservations on control channel,and the contention-free message transmissions were thus realized.The proposed RMM protocol could use the service channel during the whole synchronization interval for non-safety message transmissions,and thus the saturated network throughput and channel utilization were improved,and the transmission delay was reduced.Compared with other existing protocols,extensive analysis and simulation results demonstrate the superiority of the RMM protocol. 相似文献
3.
为了准确评估实际网络中IEEE 802.11b分布式协调功能(Distributed Coordination Function,DCF)的系统性能,提出了一种三维Markov链路模型,该模型综合考虑了DCF协议退避计数器冻结状态和有限重传次数,并结合M/M/1/K排队模型给出了在负载有限的情况下DCF系统性能的理论模型。仿真结果表明,该模型能准确地预测IEEE 802.11b DCF协议的系统性能。 相似文献
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5.
组呼通信在指挥调度中有着重要作用,而在一些地面没有基站的地方,就无法正常使用。卫星通信具有无视地形,通信范围广,不易受陆地灾害影响,易于建设等优点。把卫星通信和组呼通信结合在一起的卫星组呼通信技术兼顾两者的优点,能更好的发挥指挥调度这一作用。当前卫星组呼通信采用固定频率方式,组呼成员在一个频率下进行通信,这种方式实用性不好。本文研究的是移动卫星组呼,在GMR-1系统的基础上研究了卫星组呼通信中MAC层的功能,提出了MAC-Ready-Gcc、MAC-Dedicated-Gcc这两个为了支持组呼的状态,并针对在MAC层发生的PTT竞争提出了一种回退策略。 相似文献
6.
在 IEEE 802.11b MAC层协议的研究基础上,提出了一种基于无线Ad Hoc网络的最佳中继选择策略,该策略综合考虑瞬时信道信息和节点剩余能量,能够有效防止信道条件好的节点的过度使用,并能保证系统高吞吐量。文中以饱和吞吐量和网络生存时间为性能指标,对新算法和以往协作MAC算法进行仿真和比较,结果表明新算法在网络吞吐量下降不明显的情况下,能大大增加网络生存时间。 相似文献
7.
Responses of MAC‐T Cells to Inhibited Stearoyl‐CoA Desaturase 1 during cis‐9, trans‐11 Conjugated Linoleic Acid Synthesis 下载免费PDF全文
Cis‐9‐conjugated, trans‐11‐conjugated linoleic acid (CLA) is known for its positive activities on human health. The synthesis of cis‐9, trans‐11 CLA in mammary glands is generally thought to be catalyzed by stearoyl‐CoA desaturase 1 (SCD1), but this has not been rigorously established. In this study, we hypothesized that the inhibition of SCD1 (by CAY10566) would block the synthesis of cis‐9, trans‐11 CLA in bovine mammary alveolar cells (MAC‐T) cells. Results showed that MAC‐T cells incubated with 10 nM CAY10566 for 12 h (CAY) produced less cis‐9, trans‐11 CLA (p < 0.01), lower 14:1/(14:1 + 14:0)% (p < 0.01), more trans‐11 18:1 (TVA) accumulation (p < 0.01), and reduced SCD1 mRNA levels (p < 0.01) compared with the control group (CON). Moreover, the mRNA abundances of sterol regulatory element‐binding protein 1 [SREBPF1], acyl‐CoA synthetase short‐chain family member 2 [ACSS2], and lipin 1 [LPIN1] were significantly elevated when SCD1 was inhibited in the CAY group (p < 0.05). Taken together, CAY10566 inhibition of SCD1 resulted in lower cis‐9, trans‐11 CLA synthesis ability, and SREBF1, ACSSS2, and LPIN1 were negatively associated with SCD1. These findings not only provide the direct evidence that cis‐9, trans‐11 CLA synthesis is catalyzed by SCD1, but also help us understand the responses of MAC‐T cells to SCD1 inhibition. 相似文献
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9.
为满足智能卡在银行、保险、医疗等管理系统的应用需求,设计了一款基于ARM的支持双界面智能卡的读写系统。采用具有ARM Cortex M3内核的STM32F103RBT6和近场通信收发器STRFNFCA等芯片进行相关的硬件设计。软件设计完成了对非接触式卡和接触式卡的底层驱动及应用层通信模块、LCD显示等操作;根据PBOC 2.0标准对智能卡进行金融交易包括圈存、消费、查余额等;同时,读卡器集成了Crypto 1加密算法来兼容市场上的Mifare系列卡。测试结果表明,读写系统性能稳定、功耗低、实用性强、可靠性高。 相似文献
10.
提出一种基于消息缓存的多跳协作机制(ICC机制),该机制不需要依靠准确的网络状态信息和复杂的协作节点选择算法,而是通过利用RTS/CTS交互消息获得相隔两跳的节点MAC地址,并在数据帧中添加下两跳的节点MAC地址,使得相隔两跳的节点可靠的接收到节点发送的信号,并对接收到的信号进行合并,从而获得分集为2的增益。 相似文献