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Thomas Tsou thomastsou at gmail.comOn Wed, Jun 20, 2012 at 12:33 AM, Alexander Chemeris <alexander.chemeris at gmail.com> wrote: > Actually interesting would be to test UmTRX with your multi-ARFCN code > to see how many channels we could fit into. I tried this briefly but the transmit output was cutoff by LPF. I'll try it again with different LMS settings at the end of the week. > I wonder how do you select/measure rx_smpl_offset. My guess is that > you write both Tx and Rx I/Q streams to files, plot them and try to > align frame starts. Is that how do you do this? I mainly use two approaches. In the first method, feed the baseband output to a scope (optionally set the transceiver filler table with easy to recognizable values). Set one output of a dual function generator to trigger the scope at the frame rate. Use the second function generator output (with low duty cycle) to select individual timeslots and also trigger an RF signal generator that feeds back to the device. The offset can then be detected using the receiver energy detector. The second much quicker (and generally more effective) approach is to simply measure with a handset. Disable upper layer RACH handling and average the RACH burst TOA values over a few attempts and different handsets. This delay value is the effective combined group delay (relative to the sample counter) of host and device filters, RF components, feed line, etc. I rarely use first approach, but sometimes absolutely nothing works and the test equipment needs to be used to get a better picture. > PS Could you record a short video of making 7 calls through UmTRX? We > should make some noise or people forget what we're doing. I could record a (low quality) video with my phone. That is the only video recorder I have available right now. I can take pretty good pictures though. Thomas