다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

With the explosive growth of mobile data demand, the fifth generation (5G) mobile network would exploit the enormous amount of spectrum in the millimeter wave (mmWave) bands to greatly increase communication capacity. There are fundamental differences between mmWave communications and existing other communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mmWave communications pose several challenges to fully exploit the potential of mmWave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control. To address these challenges, we carry out a survey of existing solutions and standards, and propose design guidelines in architectures and protocols for mmWave communications. We also discuss the potential applications of mmWave communications in the 5G network, including the small cell access, the cellular access, and the wireless backhaul. Finally, we discuss relevant open research issues including the new physical layer technology, software-defined network architecture, measurements of network state information, efficient control mechanisms, and heterogeneous networking, which should be further investigated to facilitate the deployment of mmWave communication systems in the future 5G networks.

A survey of millimeter wave communications (mmWave) for 5G: opportunities and challenges

高等学校計算数学学報 = Numerical mathematics

Space-Time Block Coding for Wireless Communications

In general, Micropower Impulse Radar (MIR) depends on Ultra-Wideband (UWB) transmission systems. UWB technology can supply innovative new systems and products that have an obvious value for radar and communications uses. Important applications include bridge-deck inspection systems, ground penetrating radar, mine detection, and precise distance resolution for such things as liquid level measurement. Most of these UWB inspection and measurement methods have some unique qualities, which need to be pursued. Therefore, in considering changes to Part 15 the FCC needs to take into account the unique features of UWB technology. MIR is applicable to two general types of UWB systems: radar systems and communications systems. Currently LLNL and its licensees are focusing on radar or radar type systems. LLNL is evaluating MIR for specialized communication systems. MIR is a relatively low power technology. Therefore, MIR systems seem to have a low potential for causing harmful interference to other users of the spectrum since the transmitted signal is spread over a wide bandwidth, which results in a relatively low spectral power density.

/pdf/response-to-fcc-98-208-notice-of-inquiry-in-the-matter-of-3attixctl7.pdf

Response to FCC 98-208 notice of inquiry in the matter of revision of part 15 of the commission's rules regarding ultra-wideband transmission systems

In this paper, we consider the directional multigigabit (DMG) transmission problem in IEEE 802.11ad wireless local area networks (WLANs) and design a random-access-based medium access control (MAC) layer protocol incorporated with a directional antenna and cooperative communication techniques. A directional cooperative MAC protocol, namely, D-CoopMAC, is proposed to coordinate the uplink channel access among DMG stations (STAs) that operate in an IEEE 802.11ad WLAN. Using a 3-D Markov chain model with consideration of the directional hidden terminal problem, we develop a framework to analyze the performance of the D-CoopMAC protocol and derive a closed-form expression of saturated system throughput. Performance evaluations validate the accuracy of the theoretical analysis and show that the performance of D-CoopMAC varies with the number of DMG STAs or beam sectors. In addition, the D-CoopMAC protocol can significantly improve system performance, as compared with the traditional IEEE 802.11ad MAC protocol.

Directional Cooperative MAC Protocol Design and Performance Analysis for IEEE 802.11ad WLANs

In this paper, we propose a spatial reuse strategy for millimeter-wave (mmWave) wireless personal area networks (WPANs) with directional antennas. By this strategy, two or more transmissions can be appropriately scheduled for spatial sharing based on the beamforming (BF) information. Moreover, we analyze the performance of this strategy with consideration of the difference between idealistic and realistic directional antennas. Simulation results show that the strategy efficiency is related to antenna types, configurations and network topologies, and that the spatial multiplexing gain can be increased accordingly.

https://www.researchgate.net/profile/Qian_Chen11/publication/261046879_Spatial_reuse_strategy_in_mmWave_WPANs_with_directional_antennas/links/54ca11cd0cf2807dcc2891be.pdf

Spatial reuse strategy in mmWave WPANs with directional antennas

In this paper, a new cyclic-extended block-spreading CDMA (CEBS-CDMA) system is proposed to combat multiple access interference (MAI) efficiently over a frequency selective fading channel for an asynchronous reverse link transmission. Attribute to the block spreading, the MAI is minimized due to the small channel variation across consecutive blocks in a typical high speed system, where the signaling block duration is very short. It suggests a simplified transceiver structure with symbol-wise efficient frequency domain equalization (FDE) to improve the performance and reduce the complexity under frequency selective fading channels. A new cell-specific scrambling code is proposed with the CEBS-CDMA system for a multi-cell environment reverse link transmission, suppressing other-cell interference (OCI) efficiently. The simulation results show that the proposed CEBS-CDMA system achieves much better performance of multiple users compared to the conventional direct sequence CDMA (DS-CDMA) and cyclic prefix-CDMA systems.

A simplified transceiver structure for cyclic extended CDMA system with frequency domain equalization

Ultra-wideband (UWB) is a promising radio technology for networks delivering extremely high data rates at short ranges. Multi-band orthogonal frequency division multiplexing (MB-OFDM) is a suitable solution to implement high speed data in ultra wideband spectrum by dividing the available spectrum into multiple bands. MB-OFDM achieves adaptability as well as high performance, low-power and low-cost characteristics through the usage of OFDM. Due to the importance of error correcting codes for OFDM systems, it is essential to employ a powerful error correcting code for the MB-OFDM system to improve the performance. Recently, low-density parity-check (LDPC) code has attracted great attention because it achieves bit error rate near to the Shannon limit. In this paper, we design and evaluate the performance of the MB-OFDM system using LDPC code. In order to simplify the implementation of the LDPC encoder and decoder, we introduce a joint code and decoder design approach to construct a class of (3, k)-regular LDPC code which exactly fits to a partly parallel decoder implementation. The simulations show that the performance of such a simplified LDPC coded MB-OFDM system is better than that of a convolutional coded MB-OFDM system, and is very close to that of the conventional LDPC coded MB-OFDM system. The implementation complexity of the simplified LDPC code is carefully examined subsequently in the paper.

Performance studies of a multi-band OFDM system using a simplified LDPC code

IEEE 802.15.4a Task Group is defining an ultra low power consumption and low cost radio for Wireless Personal Area Networks (WPANs) applications using Ultra-wideband (UWB) technology with high precision ranging capability. Ternary preamble sequences of two different lengths have been proposed and adopted in the IEEE 802.15.4a specification for ranging. In order for a IEEE 802.15.4a low cost UWB device to support multiple frequency bands across the available spectrum and ranging features, as many as twenty-four ternary sequences is required. A sizeable amount of memory is needed to store the codes. In this paper, we propose a method to generate the ternary codes using linear feedback shift registers (LFSRs) as and when it is required, resulting in significant memory savings. The ranging performance using the proposed ternary preamble sequence is evaluated through simulation.

Xiaoming Peng

Papers

Directional Cooperative MAC Protocol Design and Performance Analysis for IEEE 802.11ad WLANs

Spatial reuse strategy in mmWave WPANs with directional antennas

A simplified transceiver structure for cyclic extended CDMA system with frequency domain equalization

Performance studies of a multi-band OFDM system using a simplified LDPC code

Ranging Mechanism, Preamble Generation, and Performance with IEEE 802.15.4a Low-Rate Low-Power UWB Systems