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Search Results: 1 - 10 of 11447 matches for " Yueming Cai "
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Reliable Multicast with Network Coding in Lossy Wireless Networks  [PDF]
Wei Yan, Shengyu Yu, Yueming Cai
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.310110
Abstract: To reduce the feedbacks between access point and all nodes in lossy wireless networks, a clustered system model consisting of a cluster head and multiple common nodes is investigated. Network coding has been proposed for more efficient retransmissions in reliable multicast. However, in existing schemes the access point retransmits coded packets, which causes severe delay and considerable feedbacks. In this paper, an XOR scheme based on clustered model is presented. For this scheme, the cluster head broadcasts combined packets by XORing lost packets appropriately to recover lost packets locally. We also analyze the performance in terms of expected number of transmissions. Simulation results verify theoretic analysis. And our results show that proposed XOR offers a compromise between ARQ and random linear network coding.
Performance Analysis of OFDM-Based Decode-and-Forward Relay Network with Multiple Interferers over Rayleigh Fading Channels
Jia Tu,Yueming Cai,Weiwei Yang
EURASIP Journal on Advances in Signal Processing , 2011, DOI: 10.1155/2011/202549
Abstract:
When Does Relay Transmission Give a More Secure Connection in Wireless Ad Hoc Networks?
Chunxiao Cai,Yueming Cai,Xiangyun Zhou,Weiwei Yang,Wendong Yang
Computer Science , 2014,
Abstract: Relay transmission can enhance coverage and throughput, while it can be vulnerable to eavesdropping attacks due to the additional transmission of the source message at the relay. Thus, whether or not one should use relay transmission for secure communication is an interesting and important problem. In this paper, we consider the transmission of a confidential message from a source to a destination in a decentralized wireless network in the presence of randomly distributed eavesdroppers. The source-destination pair can be potentially assisted by randomly distributed relays. For an arbitrary relay, we derive exact expressions of secure connection probability for both colluding and non-colluding eavesdroppers. We further obtain lower bound expressions on the secure connection probability, which are accurate when the eavesdropper density is small. By utilizing these lower bound expressions, we propose a relay selection strategy to improve the secure connection probability. By analytically comparing the secure connection probability for direct transmission and relay transmission, we address the important problem of whether or not to relay and discuss the condition for relay transmission in terms of the relay density and source-destination distance. These analytical results are accurate in the small eavesdropper density regime.
Primary psoas abscess extending to thigh adductors: case report
Zhongjie Zhou, Yueming Song, Qianyun Cai, Jiancheng Zeng
BMC Musculoskeletal Disorders , 2010, DOI: 10.1186/1471-2474-11-176
Abstract: A 45-year-old male with no significant past medical history presented with pain in the left thigh, and limitation of movement at the left hip and knee joint for one month. Ultrasound, CT, and MRI revealed a liquid mass in the left psoas. Percutaneous drainage of this mass yielded 300 ml pus from the psoas. After surgery, the patient reported relief of pain; however, ten days after removal of the drainage tube, the patient complained of persistent pain in his left thigh. CT revealed that the psoas abscess had extended inferiorly, and involved the entire set of adductors of the left thigh. Open surgical drainage was performed at the flank and at the thigh, yielding 350 ml of pus from the thigh. After open drainage and adequate antibiotic therapy, the patient made a good recovery. Follow-up CT confirmed complete resolution of the abscess.Large psoas abscess can penetrate the psoas sheath, and descend to thigh adductors even after percutaneous drainage. Appropriate treatment includes open surgical drainage along with antibiotic therapy.The psoas muscle is a retroperitoneal muscle that originates from the lateral borders of the 12th thoracic to fifth lumbar vertebrae, and ends as a tendon that inserts into the lesser trochanter [1]. Psoas abscess, first described by Mynter in 1881 as "psoitis"[2], is a collection of pus in the psoas compartment, and can be primary or secondary. The clinical presentation is variable and often, non-specific. Classic presentation is characterized by fever, back pain, and anterior thigh or groin pain. The diagnosis is aided by radiologic testing; CT is useful in making a definitive diagnosis, but ultrasound also can be a good choice to detect a large psoas abscess. Treatment involves the use of appropriate antibiotics along with drainage of the abscess. With appropriate treatment, the prognosis is good[3]. Psoas abscess can descend along the psoas sheath and reach the inner upper third of the thigh, but it infrequently penetrates the sheath
Channel Estimation for Two-Way Relay OFDM Networks
Yang Weiwei,Cai Yueming,Hu Junquan,Yang Wendong
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract: We consider the channel estimation for two-way relay OFDM networks. We proposed an LS-based channel estimation algorithm under block-based training schemes. Based on the mean square error (MSE) criterion, the condition and the design method for optimal training sequences are discussed. To reduce peak-to-average power ratio (PAPR), a special sequence called Zadoff-Chu sequence is employed to design the optimal training sequence, which can achieve both minimum MSE performance and excellent PAPR performance.
Channel Estimation for Two-Way Relay OFDM Networks
Weiwei Yang,Yueming Cai,Junquan Hu,Wendong Yang
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/186182
Abstract:
Joint Relay and Jammer Selection Improves the Physical Layer Security in the Face of CSI Feedback Delays
Lei Wang,Yueming Cai,Yulong Zou,Weiwei Yang,Lajos Hanzo
Mathematics , 2015,
Abstract: We enhance the physical-layer security (PLS) of amplify-and-forward relaying networks with the aid of joint relay and jammer selection (JRJS), despite the deliterious effect of channel state information (CSI) feedback delays. Furthermore, we conceive a new outage-based characterization approach for the JRJS scheme. The traditional best relay selection (TBRS) is also considered as a benchmark. We first derive closed-form expressions of both the connection outage probability (COP) and of the secrecy outage probability (SOP) for both the TBRS and JRJS schemes. Then, a reliable-and-secure connection probability (RSCP) is defined and analyzed for characterizing the effect of the correlation between the COP and SOP introduced by the corporate source-relay link. The reliability-security ratio (RSR) is introduced for characterizing the relationship between the reliability and security through the asymptotic analysis. Moreover, the concept of effective secrecy throughput is defined as the product of the secrecy rate and of the RSCP for the sake of characterizing the overall efficiency of the system, as determined by the transmit SNR, secrecy codeword rate and the power sharing ratio between the relay and jammer. The impact of the direct source-eavesdropper link and additional performance comparisons with respect to other related selection schemes are further included. Our numerical results show that the JRJS scheme outperforms the TBRS method both in terms of the RSCP as well as in terms of its effective secrecy throughput, but it is more sensitive to the feedback delays. Increasing the transmit SNR will not always improve the overall throughput. Moreover, the RSR results demonstrate that upon reducing the CSI feedback delays, the reliability improves more substantially than the security degrades, implying an overall improvement in terms of the security-reliability tradeoff.
Robust frequency offset estimator for OFDM over fast varying multipath channel
Li Wei,Youyun Xu,Yueming Cai,Xin Xu
Mathematics , 2012,
Abstract: This paper presents a robust carrier frequency offset(CFO) estimation algorithm suitable for fast varying multipath channels. The proposed algorithm estimates CFO both in time-domain and frequency-domain using two carefully designed sequences. This novel technique possesses high accuracy as well as large estimation range and works well in fast varying channels.
Quantitative Study of Lunisolar Precession Mechanism  [PDF]
Yueming Wu, Mingfu Cao
Journal of Geoscience and Environment Protection (GEP) , 2016, DOI: 10.4236/gep.2016.47021
Abstract:
According to Xiaodong Song et al.’s study about difference rotation in the Earth’s inner core, a physical model of lunar motion changing the angular momentum of the Earth’s circles is presented in this work. The Lunar motion makes there be a huge gap existing in the core angular momentum between far lunar hemisphere and near lunar hemisphere. The gap results in the difference rota-tion in the Earth’s inner core, meanwhile, it increases the angular velocity of far lunar hemisphere and decreases the angular velocity of near lunar hemisphere. The Earth’s liquid outer core gene-rates an astro-geodynamical effect including the difference rotation among the Earth’s circles. It is found that when the moon moves into the apogee or the perigee of the lunar orbit, and the moon phase is the upper and lower chords (i.e. semi-diameter place), the true anomaly of the moon will change from 270-degree back (or forward) to 90-degree; this results in the mantle shell of the Earth westward, and forms lunisolar precession, the vernal equinox westward and Chandler polar motion.
OVERSAMPLING SIGMA-DELTA CONVERSION TECHNOLOGY
过取样Σ△转换技术

Cai Yueming,Shen Yongchao,Wu Boxiu,
蔡跃明
,沈永朝,吴伯修

电子与信息学报 , 1995,
Abstract: Oversampling sigma-delta conversion technology is widely used for high-resolution A/D and D/A conversion in the audio frequency band, and also gives interesting advantages in efficient signal processing. This paper reviews the development and basic methods of the technology. The prospects of application and the ways of development are also discussed.
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