Transceiver52M: Setup dual sample rate transceiver
This patch applies oversampling, when selected with 4 sps,
to the downlink only, while running the receiver with
minimal sampling at 1 sps. These split sample rates allow
us to run a highly accurate downlink signal with minimal
distortion, while keeping receive path channel filtering
on the FPGA.
Without this patch, we oversample the receive path and
require a steep receive filter to get similar adjacent
channel suppression as the FPGA halfband / CIC filter
combination, which comes with a high computational cost.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
diff --git a/Transceiver52M/radioInterface.h b/Transceiver52M/radioInterface.h
index 2a83417..98d0f9d 100644
--- a/Transceiver52M/radioInterface.h
+++ b/Transceiver52M/radioInterface.h
@@ -23,8 +23,6 @@
/** samples per GSM symbol */
#define SAMPSPERSYM 4
-#define INCHUNK (625)
-#define OUTCHUNK (625)
static const unsigned gSlotLen = 148; ///< number of symbols per slot, not counting guard periods
@@ -38,7 +36,9 @@
VectorFIFO mReceiveFIFO; ///< FIFO that holds receive bursts
RadioDevice *mRadio; ///< the USRP object
-
+
+ int mSPSTx;
+ int mSPSRx;
signalVector *sendBuffer;
signalVector *recvBuffer;
unsigned sendCursor;
@@ -54,7 +54,6 @@
RadioClock mClock; ///< the basestation clock!
- int sps; ///< samples per GSM symbol
int receiveOffset; ///< offset b/w transmit and receive GSM timestamps, in timeslots
bool mOn; ///< indicates radio is on