Channel Sounding Scheme Research Articles

Beamformer Design for Physical Layer Security in Dual-Polarized Millimeter Wave Channels

We develop a beamforming scheme to enhance the physical layer security in dual-polarized millimeter wave (mmWave) systems. We aim to compute a transmit beamformer that maximizes the secrecy rate of the desired user. Assuming the transmitter has a statistical distribution of a dominant radio path, we compute a single-polarization beamforming vector that makes directional transmissions at mmWave frequencies more secure. Moreover, we propose a channel sounding scheme to obtain a weight vector that combines the dual-polarized antennas for improving the secrecy rate. Simulation results are presented to verify the secrecy rate performances of the proposed beamforming algorithm.

A Perturbation Approach to the Beam Tracing in the Line-of-Sight Massive MIMO Systems

In this letter, we address the problem of the beam tracing in the line-of-sight massive multiple-input multiple-output (MIMO) systems. In order to enhance the accuracy of the closed-loop channel sounding, by maximizing the predicted beamforming gain (PBFG), a new approach to the beam tracing is proposed to optimize the sounding beam sequence. The approximate expression of the PBFG measure is derived based on the perturbation analysis of the maximum likelihood (ML) cost function. At each channel use, the receiver feeds back the preferred sounding beam to the transmitter to be used at the next channel use. The performance advantage of the proposed beam tracing rule over the other existing rules and the open-loop channel sounding scheme is evidenced by the simulation results.

위치인식기반의 차세대 무선 PAN 알고리즘 개발에 관한 연구

본 논문에서는 위치인식기반 WPAN 시스템에서 송수신 안테나간의 상관관계가 존재하는 MIMO-OFDM 환경인 경우 채널의 페이딩에 의한 영향을 완화시키고 통신링크 성능향상과 신뢰성을 증대시킬 수 있는 CS(channel sounding) 기법을 제안하며, 또한 본 논문에서는 sounding신호를 통해 채널 전파특성을 측정하여 CS기법으로 추정오차가 최적화된 송신단과 수신단간의 채널 전파특성을 측정한다. 이 제안된 기법을 통해 수신단에서 간단한 연산을 통하여 채널 용량을 증가 시켜 주며, 송신단에서 채널의 정보를 이용하여 최적의 전력 할당 할 수 있고, 채널 용량의 증가를 얻을 수 있게 된다. In this paper, we propose the channel sounding scheme which is made for ideal communication between some application as well as the short distance of high speed data transmission in MIMO-OFDM system for Wireless PAN. This method is able to perceive the duration of the impulse response through the delaying of power delay profile, modeled a power delay profile which has an attenuate characteristic, and obtained the coefficient of channel response by ML (maximum likelihood). Through the amplitudes, phases and delays associated with each multipath component which were acquired from this channel sounding scheme, we can describe the wave propagation characteristics of channels between the transmitter and receiver so that the receiver could enhance not only the reliability but also the ability of communication link. Multi agent system models can be used to analyze the path of the system within any time frame. Further, parameter values can be perturbed to examine how the path of the system changes in response to exogenous shocks.

Design of Transmitter for CDM Based 2×2 Multiple Input Multiple Output Channel Sounder for Multipath Delay Measurement

Problem statement: Multiple Input Multiple Output (MIMO) wireless communication system is an innovative solution to improve the ban dwidth efficiency by exploiting multipath-richness of the propagation environment. The degree of multi path-richness of the channel will determine the capacity gain attainable by MIMO deployment. Approach: Therefore, it is very important to have accurate knowledge of the propagation environment/radio channel before MIMO implement. The radio channel behavior can be anticipated by channel meas urement or channel sounding. Code Division Multiplexing (CDM) is one of the channel sounding techniques that allow accurate measurement at the cost of hardware complexity. CDM based channel sounder, requires code with excellent auto- correlation and cross-correlation properties which generally difficult to be achieved simultaneously. Results: In this study, an efficient transmitter for CDM-ba sed 2◊2 MIMO channel sounding technique with Loosely Synchronous (LS) codes is designed. Si mulation results shows that the channel sounding scheme using LS codes gives very good performance for measuring 2◊2 MIMO channel behavior. The BPSK transmitter is designed using MATLAB, Verilog and Xilinx system generator blocks. Conclusion: The whole design is simulated as a single ISE proj ect by using ModelSim simulation tool and compiled using ISE 9.2. However the proposed design of transmitter using LS code of length 8190 bits can measure multipath delay of minimum 0.13 µs and maximum 520 µs.

Channel Sounding with Partial Channel Information in the Uplink of OFDM-Based Wireless Systems

In this paper, we consider a new channel sounding scheme for opportunistic scheduling with the use of reduced channel information in the uplink of orthogonal frequency division multiplexing (OFDM)-based wireless systems. To reduce signaling overhead for the sounding, we propose a two step channel sounding process considering the correlation characteristic in the time and frequency domain; called pre-sounding and main-sounding. Signal-to-noise power ratio (SNR) of each subchannel is first estimated through the pre-sounding process. Then, a main-sounding signal is sent over subchannels having high SNR but not highly correlated to each other. Since it is possible to extract the whole channel information from partial one by exploiting the channel correlation, the proposed scheme can significantly reduce the sounding signaling overhead without noticeable performance degradation compared to the full sounding scheme. Simulation results show that the proposed scheme provides significant performance improvement over conventional schemes especially when the channel is highly correlated in the time and frequency domain.

Ultra-Wideband Time-of-Arrival and Angle-of-Arrival Estimation Using Transformation Between Frequency and Time Domain Signals

This paper presents an ultra wideband (UWB) channel sounding scheme with a technique for time of arrival (TOA) and angle of arrival (AOA) estimation using transformation between time and frequency domain signals. Since the measured UWB power spectrum can be transformed into a time domain signal, both frequency and time domain signals are available for the channel estimation. We propose the TOA estimation using a peak search over time domain signal, and the AOA estimation using MUSIC and AOA histograms. The AOA histogram is counted for AOA samples of discrete frequencies over the UWB bandwidth. Comparing both AOA histograms before and after TOA subtraction, we can determine pairing the elements of TOA vector and those of AOA vector. The anechoic chamber tests indicated that both TOAs and AOAs were precisely resolved for two-path model, even if either TOAs or AOAs were too close to resolve.

Ultra-Wideband Time-of-Arrival and Angle-of-Arrival Estimation Using a Signal Model Based on Measurements

This paper presents an ultra wideband (UWB) channel sounding scheme with a technique for estimating time of arrival (TOA) and angle of arrival (AOA) using measurement signals. Since the power spect...

Ultra-Wideband Time-of-Arrival and Angle-of-Arrival Estimation Using a Signal Model Based on Measurements

This paper presents an ultra wideband (UWB) channel sounding scheme with a technique for estimating time of arrival (TOA) and angle of arrival (AOA) using measurement signals. Since the power spectrum over the UWB bandwidth can be measured in advance, we propose a signal model using the measurement power spectrum to design the proper UWB signals model. This signal model is more similar to measurement signals than the flat spectrum model which is an ideal model. If more than three waves impinge on a receiver, we must determine the proper grouping of the elements of TOA vector and AOA vector. It is difficult to determine the grouping using only measurement signals because of many degradation factors. We also propose pairing the elements of TOA vector and that of AOA vector using correlation method based on measurement signals and the proposed signal model. This technique is available for more than the case of three paths if pairing the estimated TOAs and AOAs of measurement signals is not accurately determined. We evaluated the proposed techniques for a vector network analyzer (VNA) with a three-dimensional virtual antenna array.

A parametric UWB propagation channel estimation and its performance validation in an anechoic chamber

This paper presents an ultrawide-band (UWB) channel sounding scheme with a parametric channel estimation to seek accurate probing of the propagation channel. The channel sounder consists of a vector network analzer and synthetic array to measure spatial transfer functions. The measured data are then applied to a maximum-likelihood (ML)-based estimator. The concepts implemented in the ML-based parametric channel estimation are: 1) to probe frequency-dependent effects in magnitude and phase of propagation paths and 2) to incorporate with robust concept of direction finding, namely, the spherical wavefront model of incident waves. The whole frequency band was divided into subbands, and the estimation of magnitude and phase was conducted in each subband. The spherical wavefront model includes a new model parameter, curvature radii, which is not covered in the conventional plane wavefront model. Performances of the proposed parametric UWB channel estimation scheme was assessed by anechoic chamber tests. The test demonstrated that: 1) the frequency-dependent magnitude and phase were accurately detected if the path was resolved and 2) the spherical wavefront outperformed the plane wavefront to model measured data given the short-range environment. Furthermore, fundamental performance of the sounding scheme, i.e., angular and time resolutions, were also evaluated in the test.

Performance of a trellis-coded 16QAM/TDMA system for land mobile communications

Trellis-coded 16QAM/TDMA systems are proposed that have a high spectral efficiency and high transmission quality and that can support a wide variety of services. A digital pilot-symbol-aided channel sounding scheme, as well as diversity reception with maximal ratio combining, are used to compensate for fading. To further improve transmission quality, symbol interleaving and two-frequency hopping are used in the trellis-coded 16QAM/TDMA system. Computer simulation demonstrates that the bit error rate (BER) performance and the spectral efficiency of the trellis-coded 16QAM/TDMA cellular system are superior to those of /spl pi//4-QPSK/TDMA used in the American and Japanese digital cellular standards. It is also demonstrated that the trellis-coded 16QAM/TDMA with diversity, symbol interleaving, and frequency hopping can achieve a BER of about 10/sup -4/ if the delay spread is 0.1 T/sub s/. >