What is Ec/Io vs Eb/No | difference between Ec/Io and Eb/No WCDMA

This page on Ec/Io vs Eb/No describes difference between Ec/Io, Ec/No and Eb/No concept in WCDMA. Link to difference between S/N ratio, C/N ratio and Eb/No is also mentioned.

Figure-1 depicts radio channel. Usually channel introduce co-channel interference, adjacent channel interference and other types of interference. This results into Io.

Channel also introduce AWGN, cosmic noise and so on. This results into No.

Ec/Io vs Eb/No, difference between Ec/Io and Eb/No

Figure depicts part of WCDMA transmit and receiver systems. As shown in the figure, Ec/No and Ec/Io relates to signal to noise ratio before despreading(i.e. before rake receiver).

Ec/Io - Energy per chip to Interference power ratio

Ec/Io stands for Energy per chip to Interference power ratio. It is measured before despreading.

Eb/No - Energy per bit to noise power density ratio

Eb/No stands for Energy per bit to noise power density ratio. It is measured after despreading.

Ec/Io and Eb/No terms are very useful for RF and Wireless system engineers to measure the performance of any wireless system. In general S/N ratio or C/N ratio or Eb/No terms are used. Ec/Io is specific to WCDMA technology. S/N stands for Signal to Noise ratio and used before modulation. C/N stands for Carrier to Noise rario and used after modulation. Refer C/N vs S/N ratio for more information.

Relation between Ec and Eb

From following equations and figure-2, difference between Ec/Io and Eb/No can easily be derived.

Ec vs Eb, relation between energy per chip vs energy per bit

The figure-2 depicts time diagram for chips and their bit representation. As shown here 8 chips constitute 1 bit.

Here Ec = Energy per chip = (A2* Tc)/2

Eb = Energy per bit = (A2* Tb)/2

Eb = Ec * SF
Where SF is Spreading Factor which is 8 here.

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