C6670 AIF2: CPRI for FDD LTE. 15 bit sample width

Ricardo Martinez

Hi,

According to AIF2 User Guide, section 3.2.2, for FDD LTE, 15-bit I & 15-bit Q samples are supported. I have checked CPRI spec and it is OK with it :-)

But according to section 7.6 (CPRI input and output module), it states that for the Uplink, data width is 7-bits (for the "efficient" case). Which I think it equals to a resolution of 14 bits per sample, not 15.

So is that right? A 15-bit resolution for the DL and 14-bit resolution for the UL? I would like a confirmation, because I do not understand any clear reasons for this after checking the user guide and the CPRI specification.

Thank you very much in advance.

Regards,

Ricardo

over 12 years ago

0 Ricardo Martinez over 12 years ago

Intellectual 290 points

I answer myself. I miss-read that 7.6 section of AIF2 User Guide. It clearly states:

For OFDM (LTE, WiMAX, ...), both Uplink and Downlink can support 15 bit and 16 bit mode.

I was mistakenly assuming that table 7-10 applied to every protocol. My bad.

Sorry for the noise.

0 arda demiray over 11 years ago in reply to Ricardo Martinez

Prodigy 150 points

Hi,

For LTE Uplink the data width of CPRI data is 15 bit I and 15 bit Q. I want to learn how to convert it to 16 bit. I mean, for exampe if we connect the AIF and FFTC, AIF input data is 15 bit I and 15 bit Q, but FFTC input is 16 bit I and 16 bit Q. Does the AIF added padding bit for converting it to 16 bit? or something different ?

Regards,

Arda

0 Ricardo Martinez over 11 years ago in reply to arda demiray

Intellectual 290 points

AIF peripheral provides sign extension.

Reference: AIF2 User's Guide, section 7.6:

• For 15-bit format, IQ data sign extension to yield 16 bits

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C6670 AIF2: CPRI for FDD LTE. 15 bit sample width