Changes between Version 27 and Version 28 of WIMXCOLUM/CUWIMAX

07/11/11 14:42:12 (11 years ago)




    v27 v28  
    190190       - Note: The file of /var/lib/wimax/WiMAX_DB.bin is changed whenever performing 'wimaxcu scan'
    192 == 9. Signal quality measurements ==
    193 After deploying the BS on site, we will need to measure the signal quality such as Received Signal Strength Indication (RSSI) and Carrier to Interference plus Noise Ratio (CINR).
    194 The measured signal quality information may help to configure the transmission power of the radio signal from antenna at the BS to control the coverage area and the propagation range of the WiMAX system.
    196 === Measurement tools  ===
    197 We use the signal measurement application ''wimax_gps_oml2'' for WiMAX which can be found in the following site: []
    198 This tool utilizes signal quality measurement according to the location which is gathered by GPS receiver (GlobalSat BU-383, connected via USB).
    200 === First measurement survey ===
    201  1. Measurement procedure
    202     - Set the transmission power of the antenna (''bs_tx_power'') to 30dBm
    203     - Defined 30 locations at Columbia Campus
    204     - Mesured WiMAX signal strehgth parameters (RSSI, CINR, Client Transmission Power)
    205     - Recorded WiMAX radio link parameters with corresponding GPS coordinates on the WiMAX client
    206  1. Results
    207     - A wide outdoor area of the campus is exposed to the WiMAX signal so that WiMAX clients are capable to get Internet connectivity via WiMAX base station
    208     - Areas behind buildings and near the edge of the campus are bad covered, or rather not covered
    209     - The results of the RSSI and CINR measurement are shown in the following figures (drawn through ):
    211 || a. Measured RSSI || b. Measured CINR ||
    212 || [[ThumbImage(0626_mexp1_30dBm.png, thumb=450)]] || [[ThumbImage(0626_mexp1_30dBm_cinr.png, thumb=450)]] ||
    214     - Identified two major problems with the recording through ''wimax_gps_oml2'':
    215        i. The recorded GPS data are inaccurate.
    216           Caused by the urban area with a lot of high buildings the number of reachable GPS satellites alternates between two and ten and consequently the accuracy the calculated GPS position is low and the calculated position alternates between locations that are several hundred feet apart.
    217        ii. The recorded RSSI is not synchronized with the calculated GPS position.
    218        We identified that the GPS position is recorded delayed in comparison to the RSSI. The longer the measurement survey the more delayed is the recorded GPS position. Due this delay the recorded data are not meaningful.
    220 === Measurement survey to create a coverage map ===
    221  1. Measurement procedure
    222     - We solved the synchronization problem of GPS and RSSI data
    223     - We could not solve the accurancy problem. We tried to use an other GPS receiver (HOLUX GR-213 instead of  GlobalSat BU-383) but the results were worst.
    224     - Consequently, we decided to select 128 locations on the campus to create the coverage map
    225     - Additionally, we increased the transmission power of the WiMAX BS to 40dBm (max. ODU) to cover a wider area of the campus
    226  1. Results
     192== 9. Signal Strength Measurements ==
     193We measured the signal quality such as Received Signal Strength Indication (RSSI) and Carrier to Interference plus Noise Ratio (CINR) across campus using the 'wimax_gps_oml2' tool. The tool writes the current location obtained from a GPS received connected via USB and various WiMAX signal parameters and writes them into an sqlite based database. The data from the database was then used to plot the results using
     195The base station TX power was set to 40 dBm. We also had to fix the 'wimax_gps_oml2' tool in the process to make sure that the measured WiMAX signal strength is paired with correct GPS location.
    228197|| a. Coverage map of measured RSSI || b. Coverage map of measured CINR ||