Measurement-based Channel Characterization Using Virtual Array with Directional Antenna

Obtaining accurate channel characteristics is essential for wireless communication system design and protocols. Directional scan sounding (DSS) achieved by rotating a directional antenna with a turntable, and virtual antenna array (VAA) basedsounding achieved by moving the antenna to the pre-designed locations are both popular methods to characterize static radio channel environments. However, the beam-width of the employed directional antenna limits the angular resolution of DSS. The conventional VAA usually employs an omnidirectional antenna which limits its application in millimeter wave bands due to the low antenna gain. In this work, VAA scheme based on directional antennas is presented to characterize the spatial-temporal profiles and omnidirectional pathloss of the channels. This scheme can provide high angular resolution and improve the SNR in the measurements simultaneously. Indoor channel measurements at 28 GHz with four different link distances were conducted to verify the effectiveness of the directional antenna based VAA scheme

Over-the-Air Testing for Connecting Faults Diagnosis in Beamforming Antenna Arrays with Short Measurement Distance

A novel diagnosis method for detecting the connecting faults (i.e., disconnected and misconnected antenna elements) in beamforming antenna array is proposed. Compared with state-of-the-art methods, the proposed diagnosis method can be conducted when the phased array operates in its default beam-steering mode. Moreover, the proposed diagnosis method is fast since it only requires a few near-field measurement positions in a very short distance (i.e., the near-field of the array). Measurement uncertainties, e.g., the scatterings from the practical testing environment, are considered in the method. Therefore, the proposed method can robustly detect beamforming array connecting faults in practical production line testing environments. The method is first validated using an 11-element dual-polarized base station (BS) antenna array at 2.7 GHz by numerical simulations. It is further experimentally validated using an eight-element single-polarized patch antenna array at 3.6 GHz. The same antenna array also serves as the probe array with only a 10-cm distance between the antenna under test (AUT) and the probe array. The diagnosis results for different types of connecting faults with numerical simulations and measurement validations have verified the effectiveness and robustness of the proposed method in practical applications.</p

An Optimal Method For Product Selection By Using Online Ratings And Considering Search Costs

With the collecting and publishing data about consumers purchasing and browsing products at the platform of online, this data prodives new ways to better understand the consumers search behavior before purchase. How to base on consumers online search behavior and simutaneously consider offline experience costs is worth studying. An optimal method based on the utility of the attribute of product is proposed. The proposed method follows steps below. Firstly, based on the multi-attribute utility theory, the overall utility of product is calculated by using ratings data. Secondly, the overall utility is combined into the original sequential search model to find the optimal selection strategy. Thirdly, the candidate product sets arranged in descending order of the reservation utilities are finally obtained. Finally, taking the online ratings data provided by a comprehensive automobile website as an example, lastly the proposed method is simulated and compared with other method. The result shows that the proposed method is feasible and effective