價格：免費
更新日期：2019-03-24
檔案大小：2.5M
目前版本：1.0.0
版本需求：Android 4.4 以上版本
官方網站：https://chandhar-labs.com
Email：prabhu@chandhar-labs.com
聯絡地址：12/26, East Club Road, Shenoy Nagar, Chennai - 600030, Tamil Nadu, India.
Shadow fading (or Shadowing) plays an important role in cellular network planning and operation as it significantly affects the coverage performance. As a result of shadow fading,for the same transmitter-receiver separation, the received signal strength
may be vastly different. If the received signal strength is measured in dB units, then the shadow fading is modeled as zero-mean Gaussian distributed random variable (in dB) with standard deviation (in dB). For theoretical understanding of shadow fading, you may refer to [Sec:4.9.2,1]. In practice, the standard deviation typically varies from 4 dB (Urban cellular) to 12 dB (Rural) [Tab:A1-2, 2].
Fortunately, you can use your smart phone to understand the Shadowing phenomenon. Through downlink transmissons from the base stations, your phone measures Reference Signal Received Power (RSRP) and some other metrics for performing cell selection/reselection and handover. For example, in LTE, there are 98 RSRP values defined ranging from -140 dBm to -40 dBm with 1 dB resolution [3].
The Shadow Lab app collects these RSRP samples at regular time intervals (currently for every second) and plots three different graphs: Histogram, PDF, and Line Chart. In the PDF graph, you can also see the mean and standard deviation of the collected RSRP samples.
The Shadow lab app is developed using an open source android app 'LTE Coverage Tool' developed by the National Institute of Standards and Technology (NIST), Public Safety Communications Research Division (PSCR), USA [4].
In future updates, more features will be added to the app so that you can send the samples to the CRF Repository.
You are welcome to provide your feedback at shadowlab.app@gmail.com
Instructions to use the app:
Measurements can be taken inside your building or across the street. After clicking 'New Recording' button slowly start walking. Take a step and stand for 5 to 10 seconds. Take another step and stand for 5 to 10 seconds. Continue this process until you covered the entire area of your building or street. If you are inside your home, take measurements in all rooms. If you are in the street, take measurements up to 20 m distance. If sufficient number of samples collected (more than 500) press the stop button.
References:
[1] T. Rappaport, “Wireless Communications: Principles and Practice,“ 2nd ed. Upper Saddle River, NJ, USA: Prentice Hall PTR, 2001.
[2] “Guidelines for evaluation of radio interface technologies for IMT-Advanced ITU,“ Tech. Rep. M2135.
[3] https://blog.arimas.com/78-rsrp-and-rsrq-measurement-in-lte
[4] https://github.com/usnistgov/LTECoverageTool