1. Downlink rates The next slide was presented to Jonathans’ flux review
It was based on the UW background runs, for which the generated and trigger rates are available, and which sampled a full orbit-day at 10%.
An important parameter: downlink limit is 1.2 Mbit/sec (average).
THB C&A presentation 12/12/05

2. Simulating rates: the big picture
Incoming rate into the 6 m2 sphere: is it right?
Corresponding trigger rate: implies 15% deadtime: too high!
Downlink rate: saturates our bandwidth allocation?
one full day
THB C&A presentation 12/12/05

3. The downlink rates from the SLAC/Lyon 1B background run
Note: it was not a full day
If we throw out “no-cal” events here, rather than later, save a factor of two
THB C&A presentation 12/12/05

4. What is the limit? Are we in trouble?
Depends on
amount of event data (including noise, which for the tracker is probably overestimated)
JJ’s skill at lossless compression
Current status, from JJ, via Atwood:
OVERHEAD: ~12 bytes (fixed)  
GEM: 40 bytes (fixed) (a little work could bring this done to <20 bytes, I'll do it at some time cause its cheap)
ACD : 7 addressing bits
           5 bit hit mask (The 5 bits are-> Hit A:B side. Pha Accept A:B side, GEM Veto hit)
           12 bits for each PHA side (up to 2)
           example: A tile with only one PHA reporting in: 24 bits
                         A tile with both       PHA's reporting in: 36 bits
CAL: bits overhead
       : 4-5 bits addressing / log
       : 12:17 bits for the ADC value /log (both ends)
          [Empirically I am measuring about a factor of compression over the data encoding
          of  16 towers * (32 bits + 32 bits * nlogs)]
          Example 50 logs::  64 + (5+15) * 50 bits => 133 bytes
TKR: 12:13 bits per strip address
          5-6  bits per TOT
          Example 100 strips::         100 * 18 bits => 225 bytes
THB C&A presentation 12/12/05

5. OK, these are (almost) linear in the number of DIGIS: what do we see for these events?
THB C&A presentation 12/12/05

6. Apply the JJ analysis Event size analysis All events NoCal n bits
All events
NoCal n
bits
total
tota
overhead
1.0
480
ACD
1.8 30 54
0.8 24
TKR*
9.8 18
176
6.7
121
CAL
19.0 20
380
 20  0
1090
625
*TRK is overestimate, assuming 1 TOT/hit
THB C&A presentation 12/12/05

7. The bottom line Preliminary!
1.2 Mbits/s / 1.1 kbit/event = 1.1 kHz event rate
Preliminary!
THB C&A presentation 12/12/05