Spring 2019 Gavel Spring Gavel 2019 - Page 23

along with their corresponding code names. The icons for the cell sites represent three-sector cells. The heatmap colors are the coverage or serving areas for each cell sector. The boundary area between colors is where the handoffs occur from one cell sector to the next. If a mobile phone was being served by the sector indicated by the black arrow, then it would be deemed to be located within the red area indicated by the red arrow. As Figure 7 demonstrates, the coverage areas of the cells look nothing like circles or arcs. Most coverage areas are shown generally downstream from the antenna, but the shape and size are dependent on all the factors mentioned previously. This modeling is based on scientific calculations and real-world data. Figure 7: Best server coverage plot Measured Data Drive testing can be performed to further improve the RF coverage model. Drive testing uses a device such as the one in Figure 8. The drive test equipment consists of a high speed cellular scanner, GPS receiver, cellphones, and a tablet or laptop computer. The equipment is installed in a vehicle and then driven around the area of interest to gather actual signal strength measurements being received from the cell sites. The scanner collects signal strength and cell site parameters for multiple technologies simultaneously. The GPS receiver tags a location to the signal data once per second and stores it on the hard drive of the tablet or laptop computer. A phone can be connected Figure 8: Drive to the equipment in test equipment order to simulate a user experience and try to duplicate the mobile phone in question. Network data collected from the phone indicates the serving cell, signal levels, and a host of other data. While it is desired to use the same model of phone as the defendant used, it is not necessary because most phones use similar technology. In addition, radio frequency specifications for the mobile phone are set by FCC requirements.8 The resulting signal strength measurements and their GPS locations are imported into the modeling software. The modeling software uses the actual measured data to fine tune the model and make it more accurate. Network-related parameters are also collected via a proprietary interface to the USB port on the cellphone. This provides information equivalent to the mobile phone of interest and provides the best duplication of the RF experience.   Information Requested from Wireless Operators When requesting information from the mobile wireless operator with a subpoena, it is important to be proactive and timely. Records may be stored for a few months up to several years, depending on the wireless operator. The subpoena should contain the following in order to determine the phone’s location: All subscriber information, call detail(s), caller identification(s), cell site location information, call detail records. List of cell sites within a *** radius of *** containing the following for each cell sector (required for RF modeling of actual coverage): · Latitude · Longitude · Ground Elevation (feet) · Antenna Centerline (feet) · Antenna Azimuth (degrees from True North) · Antenna Model · Antenna Mechanical Down tilt · Antenna Electrical Down tilt · Cable Losses (dBm) · EiRP (Watts) · Technology (LTE, UMTS, CDMA, EVDO, GSM, etc.) · MIMO configuration (2 x 2, none, etc.) · Frequency Band · Channel Number (Channel number for CDMA, UARFCN for UMTS, EARFCN for LTE) · Cell site identification code per technology (PN for CDMA, PSC for UMTS, PCI for LTE) SPRING 2019 23