BER vs. Eb/N0 plot – round III

So today a new “disclaimer” appeared on the xG Technology web page above the BER vs. Eb/N0 plot saying:

“Range and penetration are functions of both Eb/No and system characteristics. This chart depicts the Bit Error Rate (BER) of xMax vs. other typical modulation systems based solely on equal Eb/No, but does not depict the performance provided by xMax system gain which can add substantial advantage.”

Two communication systems differing by the modulation technique, such as xMax and a system using conventional modulation, but otherwise having the same parameters (data rate, transmit power, transmit/receive antenna gains, operating frequency, bandwidth, noise figure, etc.), will have the same range and penetration. In other words, in a fair one-to-one comparison of two communication systems, knowing that they require the same Eb/N0 to operate at a specified BER, immediately tells you that they will have the same range and penetration.

Having published a BER vs. Eb/N0 curve showing that xMax performance is very close to that of conventional communication systems, it makes no sense from a technical standpoint to argue that xMax has better range and penetration (again, assuming a fair comparison). As I tried to explain in an earlier post “Understanding the range of wireless systems”, the key issue is the maximum pathloss which the communication system can overcome. This pathloss can be calculated doing a link budget. The effect of the modulation technique enters the link budget only through the required Eb/N0.

To put this in simple and completely non technical terms: you can’t have your cake and eat it too ….


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