# Longley Rice propagation model and reciprocity

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Joel Johnson2021-10-9

Code snippet below seems to show that MATLAB's Longley-Rice propagation model may not always be reciprocal - is this correct? Thanks!
close all; clear all;
% A test to show that the Matlab LR functions don't seem to be reciprocal
pm = propagationModel('longley-rice','AntennaPolarization','vertical');
freq = 469e6; % Tx freq (MHz)
S1 = [39.420200,-82.875300]; % Lat/Lon of Site 1
S2 = [39.413000,-82.896111]; % Lat/Lon of Site 2
s1ht = 1:50; % Antenna height @ site 1
s2ht = 2.08; % Antenna height @ site 2
% Link from S1 to S2
tx = txsite('Latitude',S1(1),'Longitude',S1(2),'AntennaHeight',s1ht,'TransmitterFrequency',freq);
rx = rxsite('Latitude',S2(1),'Longitude',S2(2),'AntennaHeight',s2ht);
PL1 = pathloss(pm,rx,tx);
tx = txsite('Latitude',S2(1),'Longitude',S2(2),'AntennaHeight',s2ht,'TransmitterFrequency',freq);
rx = rxsite('Latitude',S1(1),'Longitude',S1(2),'AntennaHeight',s1ht);
PL2 = pathloss(pm,rx,tx);
plot(PL1,s1ht,'linewidth',2); set(gca,'Xdir','Reverse'); set(gca,'Fontsize',20); xlabel('Path loss (dB)'); ylabel('Tx Antenna height (m)')
hold on
grid on
plot(PL2,s1ht,'x','linewidth',2);
legend('S1 to S2','S2 to S1')
##### 1 个评论显示隐藏 无
Joel Johnson 2021-10-9
I subsequently noticed that there is no difference in the two in R2021b so probably this got fixed somewhere between R2018 and R2021.

### 采纳的回答

Tanmay Das 2021-10-14
Hi,
As pointed out by Joel, the bug has been fixed in the future releases. So it is recommended to update the MATLAB version in order to leverage its full functionality.
##### 1 个评论显示隐藏 无
Joel Johnson 2021-10-14
Thanks!

R2018b

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