| 75 | 1. Indoor testing at IRT on Feb 25, 2011 |
| 76 | - Succeeded to scan and connect one of our WiMAX clients (Linux OS) to BS |
| 77 | 1. Purchase of a server rack cabinet and a PDU (power distribution unit) via Diasy Nguyen (CRF) and Elias Tesfaye (CS Department) on May 19, 2011 |
| 78 | - Triplite 12U rack ($444,73) |
| 79 | - APC PDU for remote power ($425.45) |
| 80 | 1. Meeting with Donald A. Schlosser (Assistant Vice President of Campus Opers-Custodial Services, Columbia Facilities) on Jun 09, 2011 |
| 81 | - Site survey at 16th floor, Mudd building |
| 82 | 1. Started to mount and install WiMAX equipment on site on Jun 14, 2011 |
| 83 | - Technicians from Facilities and Nathan Schulzrinne (CRF intern) helped us for the deployment, including: Drilling holes on railings, fixing the mask and the antenna, mounting ODU on wall inside the building, and connecting the coaxial cable between antenna and ODU |
| 84 | - Wired opticla fiber and power cables |
| 85 | - Activation of Ethernet by CUIT (Two ports of Giga-bit Ethernet for Internet connection and for PDU management) |
| 86 | 1. Finished installation of the WiMAX BS on Jun 23, 2011 |
| 87 | 1. First singnal measurement survey on Jun 26, 2011 |
| 88 | 1. Measurement survey to create the coverage map on Jun 30, 2011 |
| 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. |
| 195 | |
| 196 | === Measurement tools === |
| 197 | We use the signal measurement application ''wimax_gps_oml2'' for WiMAX which can be found in the following site: [http://wimax.orbit-lab.org/wiki/WiMAX/30/02#WimaxMeasurementApplication:wimax_gps_oml2 Orbit-Lab.org] |
| 198 | This tool utilizes signal quality measurement according to the location which is gathered by GPS receiver (GlobalSat BU-383, connected via USB). |
| 199 | |
| 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 http://gpsvisualizer.com ): |
| 210 | |
| 211 | || a. Measured RSSI || b. Measured CINR || |
| 212 | || [[ThumbImage(0626_mexp1_30dBm.png, thumb=450)]] || [[ThumbImage(0626_mexp1_30dBm_cinr.png, thumb=450)]] || |
| 213 | |
| 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. |
| 219 | |
| 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 |
| 227 | |
| 228 | || a. Coverage map of measured RSSI || b. Coverage map of measured CINR || |
| 229 | || [[ThumbImage(063011_mexp2_40dBm_map_rssi.png, thumb=450)]] || [[ThumbImage(063011_mexp2_40dBm_map_cinr.png, thumb=450)]] || |
| 230 | |
| 231 | |