QoS awared power and admission controls based on non-cooperative game theory in wireless networks / 药物分析学报

In order to better accommodate heterogeneous quality of service (QoS) in wireless networks, an algorithm called QeS-aware power and admission controls (QAPAC) is proposed. The system is modeled as u non- cooperative game where the users adjust their transmit powers to maximize the utility, thus restraining the interferences. By using adaptive utility functions and tunable pricing parameters according to QoS levels, this algorithm can well meet different QoS reqniremcnts and improve system capacity compared with those that ignore the QoS differ- ences.

General precoder design for mitigation of intercarrier interference in OFDM mobile systems / 药物分析学报

For orthogonal frequency-division multiplexing (OFDM) communication systems, the frequency offset in mobile radio channels distorts the orthogonality between sub-carriers, which results in Intercarrier Interference(ICI) and seriously degrades the performance of systems. Based on ICI coefficients analysis, a novel precoder design scheme is proposed for mitigation of ICI. In this technique, precoder matrix is designed by the way of linear counteraction and inserted in the former transmitter signal. Computer simulation results show that this new scheme can effectively reduce ICI and significantly provide the carrier-interference power ratio improvement. Compared with existing ICI mitigation schemes with channel estimation, the proposed scheme has lower computational complexity, and compared with self-cancellation scheme, the bandwidth efficiency can be improved in this proposed scheme. The proposed scheme also has better convergence stability for time-varying frequency selective fading channel.

Impact of channel estimation error on channel capacity of multiple input multiple output system / 药物分析学报

In order to investigate the impact of channel estimation error on channel capacity of multiple input multiple output (MIMO) system, a novel method is proposed to explore the channel capacity in correlated Rayleigh fading environment. A system model is constructed based on the channel estimation error at receiver side. Using the properties of Wishart distribution, the lower bound of the channel capacity is derived when the MIMO channel is of full rank. Then a method is proposed to select the optimum set of transmit antennas based on the lower bound of the mean channel capacity. The novel method can be easily implemented with low computational complexity. The simulation results show that the channel capacity of MIMO system is sensitive to channel estimation error, and is maximized when the signal-to-noise ratio increases to a certain point. Proper selection of transmit antennas can increase the channel capacity of MIMO system by about 1 bit/s in a flat fading environment with deficient rank of channel matrix.

Imaging appearances of primary hepatic and gallbladder neuroendocrine carcinomas / 中华放射学杂志

Objective To review the imaging appearances and clinical symptoms of primary hepatic and gallbladder neuroendocrine carcinomas (PHGNC). Methods Five patients (4 females and 1 male) were examined. Long-term diarrhea not controlled by drug was found in four patients, and two of them accompanied by abdominal pain. The liver rupture occurred in one case due to the huge tumor bleeding. Five patients were examined by using ultrasonography (US), four patients by CT, and three patients by hepatic angiography. The tumor originated from liver in three cases, from liver and gallbladder in one case, and from gallbladder in one case. The tumors were diagnosed by surgery in 3 cases, by biopsy and by autopsy in 1 case, respectively. Results Multiple hyperechoic inhomogeneous masses in two cases and hypoechoic inhomogeneous masses in one case were revealed, all with some small fluid areas and abundant vessels. A huge cyst-solid tumor was clearly demonstrated by using US. A small mural nodule along the gallbladder wall was displayed by using US in a gallbladder tumor, and it showed no specific sign in the diagnosis. CT findings included hypodense inhomogeneous masses on plain CT scan, and slightly enhanced masses with some small fluid areas after injection of contrast agent. A huge cyst-solid tumor was clearly displayed by CT due to the hemorrhage, necrosis, and cystic changes in the tumor. Hepatoangiography displayed abundant vessels and stain in the solid part of the tumor, and absent vessel in the cystic region of the cyst-solid tumor accompanied by dislocation of surrounding vessels. Conclusion Imaging appearances of the liver tumor were inhomogeneous mass with abundant vessels and tumor stains. Imaging appearances of the gallbladder tumor were raised mural nodule along the gallbladder wall without specific sign in the diagnosis of the tumor. The tumor may develop hemorrhage, necrosis, and cystic changes if it is large enough. PHGNC was prone to hepatic metastases. The patients often presented with diarrhea and abdominal pain.