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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.

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.

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.