Eb/No Different requirements

[Mdaf]

Hi
Sorry for this basic question but we know that each service has it's own Eb/No requirements.
Eb/No is basically a ratio between bit energy of the desired signal over all intefernce energy. Now for speech, Eb/No requirements let's say it's 5 dB now a lot of references mention that the Eb/No might be change due to UE speed, fading...etc for the same service
My question is the Eb/No is a ratio , and as long as it's a ratio why it should be changed for the same service according to different radio conditions?
Many thanks.

[Philippe]

The Eb/No targets represents the signal to interference ratio (here ratio of density C/I = Eb/No - Processing Gain) that you should reach to maintain a good quality generally measured in BLER (Block Error Rate). Due to multipath fading (fast fading), it is more or less difficult for the receiver to achieve the BLER and so the required level of signal above interference varies. The speed is also affecting the multipath fading properties (Doppler effect).

This is signal theory and you need to simulate mutipath fading effect on the receiver/transmitter chain performance (including correlation/decorrelation, coding /decoding, rate matching, etc...). Link level simulations (or lab test measurements) are performed to assess the required Eb/No according to the multipah profile (e.g. PedA, VehA, TU, AWGN) and the speed of the mobile: they give for each multipath environment the required Eb/No as a function of the BLER.