Return on Investment (roi) for Multi-Technology son juan Ramiro, Mark Austin and Khalid Hamied

276 Appendix B: X-Map Estimation for LTE

Figure B.2 X-maps based on approach 1 (left) and based on approach 2 (right).
and time are used together with a ray tracer to determine the number of visible satellites for each user position in the scenario. A satellite is assumed to be visible if a direct path between the UE position and the satellite exists. The information about the number of visible satellites and about the geometry between the UE position and the satellite, as well as about the standard deviation of the measurement error, is utilized to model the position error based on the approach described in [11]. The calculated position errors are then added to the real positions provided by the scenario in order to obtain the estimated user positions. If less than four satellites are visible, e.g. in dense urban canyons, it is assumed that positioning with GPS is not possible. In such cases, other positioning methods should be used.
In Figure B.2, two examples of X-maps with a resolution of 10 m × 10 m showing RSRP in dBm for a specific site of the scenario can be seen. On the left side, approach 1 is used to create the X-map, whereas the X-map on the right side is based on approach 2. For both X-maps, the real positions as provided by the scenario are applied.
The advantage of approach 1 is that the resulting X-map reflects the real situation in the network since the measurement data is used directly for creating the X-map. However, the disadvantage of this approach is that the X-map provides RSRP values only for those pixels that are covered by the UEs as can be seen in Figure B.2 (the dark area means that there is no RSRP value available). In contrast, every pixel in the area has an RSRP value when using approach 2, i.e. the coverage of the X-map is greater compared to approach 1. The accuracy, however, is not as high as for the X-map based on approach 1 with a mean error of 2.1 dB and a standard deviation of 6.6 dB as shown in Table B.1. Note that the accuracy is determined by comparing every pixel with an available RSRP value with the reference values, i.e. pixels that are not included in the calibration process are also considered when determining the accuracy of the X-map based on approach 2.
The accuracy for approach 2 is comparable to what can be achieved with today’s calibrated propagation models for small macro- and microcells. For the models presented in [7], for example, about 7 dB up to 9 dB is mentioned as the average standard deviation of the prediction error. The absolute values of the mean errors typically range from about 0 dB up to 6 dB. For the corresponding analyses, building data and measurement data at 947 MHz were available for an area in downtown Munich [7].
Appendix B: X-Map Estimation for LTE 277