====== Tidbits ======




===== DMA-considerations =====
Size of the slots and FIFOs:
<htmlonly><br clear="all" /></htmlonly>
| For 1 slot | Rx - ics554 | Tx - ics564 |
| Samples | 2560*2=5120=5k | 2560*2=5120=5k |
| Bytes | 5120*16=81920=80k | 5120*4=20480=20k |
| FIFO-size [bytes] | 65536*8=512k | 65536*4*2=512k |
| Max samples | <latex>\frac{512k}{2*16}=16k</latex> |  <latex>\frac{512k}{2*4}=64k</latex> |


The samples per slot is given by the pseudo-UMTS system of the software-radio
and is fixed for the moment at 2560 samples.
As we do an oversampling by a factor of 2, this gives 2560*2=5120 samples per
slot, for both the ics554 and ics564.

The total bytes is calculated as
<latex>samples*bytes_ per_ samples</latex>, where
<latex>bytes_
per_ samples</latex>
is:

<ldl>
<ldt>4</ldt><ldd>= 16bit real + 16bit imaginary</ldd>
<ldt>16</ldt><ldd>= 32bit real + 32bit imaginary, but for two channels, as we can't treat only one channel at a time in the ics554-card</ldd>
</ldl>

According to the ics-554 documentation E10681 Rev.B p. 55, the FIFO is sized at
65536 * 64bit-values, which gives 512kBytes.
The ics-564 documentation E10734 Rev.- p. 9 gives the size 65536 16bit-samples
as {}``approximately one quarter of the FIFO-size''.
So the total is 65536*4*2 = 512kBytes.

==== Conclusion ====

The DMA-size will be dependant on the slot-size. So, there will be 1 slot per
DMA-transfer. This limits the slot-length to
16kSamples for the Rx-part, but that should be OK.

Care has to be taken for small slot-sizes, as the DMA-transfer happens in two
steps:

  - Fill up the FIFOs on the ics564
  - Start the transfer
  - Wait for underflow of the FIFOs and re-transmit

===== Server =====

The old implementation of the server takes DMA_BLOCK-sized packets and works on
these. In order to rewrite only what is
necessary, I adjusted the Base/Antenna/Simul_ics in a way to chop down the
slots into DMA_BLOCK-sized packets. Too bad
if it is not a multiple of these. There is no check against that.

===== Resampler =====

A big mess that nobody understands. Hopefully the work of the student this
summer sheds some light on this.

===== Samples, Chips and Symbols =====

The current setup has 2 Samples for 1 Chip, and 1 Chip for 1 Symbol (without a
spreading-sequence). This means, that there
is a 2 x oversampling.