1. Florida Institute of technologies ECE 5221 Personal Communication Systems Prepared by: Dr. Ivica Kostanic Lecture 5: Example of a macroscopic propagation model (Lee model) Spring 2011

2. Florida Institute of technologies Page 2  Lee model equation  Propagation prediction over terrain database  Nominal cell radius calculation  Examples Outline Important note: Slides present summary of the results. Detailed derivations are given in notes.

3. Florida Institute of technologies Page 3 Macroscopic propagation modeling  More input descriptors – more accurate models  As the models become more accurate, the standard deviation of the unexplained portion of path loss becomes smaller  The unexplained portion still retains log normal character Page 3 Log distance path loss model More general models  Some popular macroscopic propagation models o Lee model o Hata-Okumura o COST 231 o Longley-Rice o Walfish-Ikagami, etc.

4. Florida Institute of technologies Lee model  Developed by W.C.Y Lee in 1970s  Statistical, empirical model  Popular due to is simplicity and relatively good accuracy  Valid for frequencies 800-2000MHz  Straight forward extension of log distance path loss model  Expected model accuracy: 6-9dB standard deviation of the prediction error  Model introduces reference conditions  Prediction conducted in two steps oStep 1. Predict the propagation path losses for standard conditions oStep 2. Correct the prediction for all differences between actual and standard conditions  Parameters of the environment are specified for standard conditions  Two parameters of the environment are given oSlope of the path loss in dB/dec (m) oReference distance intercept in dBm (or reference distance path loss in dB) Page 4 ParameterReference value Transmit power10W (40dBm) BS antenna height100 ft (30m) BS antenna gain6dB MS antenna height10 ft (3m) MS antenna gain0dB Reference distance1 mile (or 1km) Illustration of Lee model reference conditions

5. Florida Institute of technologies Lee model – RSL form RLS 0 – reference distance intercept (dBm) m – slope (dB/dec) P T – transmit power (dBm) h te – effective antenna height of the transmitter h r – height of the receiver G T – transmit antenna gain G m – mobile antenna gain d – distance between transmitter and receiver Page 5 Form 1: RSL form Correction coefficients have default values C = 15dB F = 10dB Parameter explanations: Environment @ f=850MHz Intercept (dBm)Slope (dB/dec) Open area-54.543.5 Suburban-63.038.4 Urban-67.040.0 Dense urban-77.043.1 Frequency correction: slope stays the same intercept adjusted as

6. Florida Institute of technologies Lee model – path loss form Page 6 PL 0 – reference distance path loss (dB) m – slope (dB/dec) h te – effective antenna height of the transmitter h r – height of the receiver G T – transmit antenna gain G m – mobile antenna gain d – distance between transmitter and receiver Correction coefficients have default values C = 15dB F = 10dB Parameter explanations: Environment @ f=850MHz Intercept (dBm)Slope (dB/dec) Open area100.543.5 Suburban10938.4 Urban11340.0 Dense urban12443.1 Frequency correction: slope stays the same PL 0 adjusted as Form 2: PL form

7. Florida Institute of technologies Effective antenna height – slope method  Lee model uses slope method for effective antenna height calculation  Slope of the local terrain of the receiver – extended  Effective antenna height – determined by intersection of the slope and the vertical through TX antenna  Two cases oUp-sloping terrain – effective height greater than actual height oDown sloping terrain – effective height smaller then effective height  Effective antenna height is a local parameter, i.e. it is different for every point within coverage region Page 7 Note: calculation of effective height requires knowledge of terrain elevations with the coverage area

8. Florida Institute of technologies Diffraction losses  Diffraction losses – additional losses due to terrain blockage  Terrain obstacle – replaced by knife edge  Two steps for additional loss calculation oStep 1. Calculate Fresnel-Kirchoff parameter oStep 2. Estimate losses using diffraction formulas Page 8 Illustration of KED calculations

9. Florida Institute of technologies Propagation over terrain  Terrain database – fundamental input into propagation modeling  Accuracy of terrain database – bin size  Typical bin size 30-100m  Using terrain -> radio profile is generated  Through radio profile 3D propagation problem becomes 2D problem  Radio profile is used by propagation model to estimate path loss  Path loss is calculated between the transmitter and every bin within surrounding region Page 9 Example of radio profile Terrain data

10. Florida Institute of technologies Example 1 Consider a transmitter located in suburban environment. The effective height of the transmitter is 45m, its power is 20W and the gain of the transmit antenna is 8dB. Calculate the path loss and RSL at the mobile located at distance of 5miles. The gain of the mobile antenna is 0dB and its height is 1.5m. The frequency of operation is 850MHz. Use Lee model. Answers: RSL = -85.2dBm PL = 136.2dB Page 10

11. Florida Institute of technologies Example 2 Consider a system deployed in urban environment. Assume that the operating frequency is 1900Mhz and that the minimum RSL at the receiver is -95dBm. The base station has ERP of 50dBm and effective height of 40m. The mobile height is 1.5m and its antenna gain is 0dB. The error of propagation modeling is characterized by standard deviation of 8dB. a)Determine the contour for 90% are reliability. b)Using Lee model estimate distance to contour calculated in part a) c)Repeat a) and b) for reliability of 95% d)Estimate increase of the cell site count that corresponds to the increase of reliability requirement. Answers: a) RSLp=-89.96dBm b) d = 3 miles c) RSLp = -86.6dBm, d = 2.43 mile d) 95% reliability requires 50% more cells Page 11