transceiver: simplify transmit power control

UHD will internally accept floats with a range of +/-1.0,
which corresponds to a 16-bit signed integer range of
apporximately +/- 32000. Set the default amplitude to .3,
which is a safe value agaist saturation elsewhere in the
transmit chain.

The non-UHD maximum amplitude is unchanged at 13500.

Remove digital gain control because it's unnecessary and
causes extra load on enbedded systems.

Signed-off-by: Thomas Tsou <ttsou@vt.edu>

public-trunk/Transceiver/Transceiver.cpp

@@ -397,8 +397,7 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime,
 			    *DFEFeedback[timeslot]);
     }
     wTime = rxBurst->time();
-    // FIXME:  what is full scale for the USRP?  we get more that 12 bits of resolution...
-    RSSI = (int) floor(20.0*log10(9450.0/amplitude.abs()));
+    RSSI = (int) floor(20.0*log10(rxFullScale/amplitude.abs()));
     LOG(DEBUG) << "RSSI: " << RSSI;
     timingOffset = (int) round(TOA*256.0/mSamplesPerSymbol);
   }

public-trunk/Transceiver/UHDDevice.cpp

@@ -38,12 +38,15 @@
                         on the RF side of the timestamping point of the device.
                         This value is generally empirically measured.
 
-    smpl_buf_sz       - The receive sample buffer size in bytes. 
+    smpl_buf_sz       - The receive sample buffer size in bytes.
+
+    tx_ampl           - Transmit amplitude must be between 0 and 1.0
 */
 const bool use_ext_ref = false;
 const double master_clk_rt = 100e6;
 const double rx_smpl_offset = .00005;
 const size_t smpl_buf_sz = (1 << 20);
+const float tx_ampl = .3;
 
 /** Timestamp conversion
     @param timestamp a UHD or OpenBTS timestamp
@@ -158,8 +161,8 @@ public:
 	inline TIMESTAMP initialWriteTimestamp() { return 0; }
 	inline TIMESTAMP initialReadTimestamp() { return 0; }
 
-	inline double fullScaleInputValue() { return 13500.0; }
-	inline double fullScaleOutputValue() { return 9450.0; }
+	inline double fullScaleInputValue() { return 32000 * tx_ampl; }
+	inline double fullScaleOutputValue() { return 32000; }
 
 	double setRxGain(double db);
 	double getRxGain(void) { return rx_gain; }

public-trunk/Transceiver/radioInterface.cpp

@@ -58,7 +58,6 @@ RadioInterface::RadioInterface(RadioDevice *wUsrp,
   receiveOffset = wReceiveOffset;
   samplesPerSymbol = wSamplesPerSymbol;
   mClock.set(wStartTime);
-  powerScaling = 1.0;
 }
 
 RadioInterface::~RadioInterface(void) {
@@ -82,12 +81,7 @@ double RadioInterface::fullScaleOutputValue(void) {
 
 void RadioInterface::setPowerAttenuation(double atten)
 {
-  double HWatten = usrp->setTxGain(usrp->maxTxGain() - atten);
-  atten -= HWatten;
-  if (atten < 1.0)
-    powerScaling = 1.0;
-  else
-    powerScaling = 1.0 / sqrt(pow(10, (atten / 10.0)));
+  usrp->setTxGain(usrp->maxTxGain() - atten);
 }
 
 short *RadioInterface::USRPifyVector(signalVector &wVector) 
@@ -155,7 +149,7 @@ void RadioInterface::pushBuffer(void) {
   delete inputVector;
  
   // Set transmit gain and power here.
-  scaleVector(*resampledVector, powerScaling * usrp->fullScaleInputValue());
+  scaleVector(*resampledVector, usrp->fullScaleInputValue());
 
   short *resampledVectorShort = USRPifyVector(*resampledVector);
 

public-trunk/Transceiver/radioInterface.h

@@ -142,8 +142,6 @@ private:
 
   bool mOn;				      ///< indicates radio is on
 
-  double powerScaling;
-
   /** format samples to USRP */ 
   short *USRPifyVector(signalVector &wVector);
 

public-trunk/Transceiver52M/Transceiver.cpp

@@ -401,7 +401,6 @@ SoftVector *Transceiver::pullRadioVector(GSM::Time &wTime,
 			    *DFEFeedback[timeslot]);
     }
     wTime = rxBurst->time();
-    // FIXME:  what is full scale for the USRP?  we get more that 12 bits of resolution...
     RSSI = (int) floor(20.0*log10(rxFullScale/amplitude.abs()));
     LOG(DEBUG) << "RSSI: " << RSSI;
     timingOffset = (int) round(TOA*256.0/mSamplesPerSymbol);

public-trunk/Transceiver52M/UHDDevice.cpp

@@ -38,12 +38,15 @@
                         on the RF side of the timestamping point of the device.
                         This value is generally empirically measured.
 
-    smpl_buf_sz       - The receive sample buffer size in bytes. 
+    smpl_buf_sz       - The receive sample buffer size in bytes.
+
+    tx_ampl           - Transmit amplitude must be between 0 and 1.0
 */
 const bool use_ext_ref = false;
 const double master_clk_rt = 52e6;
 const double rx_smpl_offset = .0000869;
 const size_t smpl_buf_sz = (1 << 20);
+const float tx_ampl = .3;
 
 /** Timestamp conversion
     @param timestamp a UHD or OpenBTS timestamp
@@ -158,8 +161,8 @@ public:
 	inline TIMESTAMP initialWriteTimestamp() { return 0; }
 	inline TIMESTAMP initialReadTimestamp() { return 0; }
 
-	inline double fullScaleInputValue() { return 13500.0; }
-	inline double fullScaleOutputValue() { return 9450.0; }
+	inline double fullScaleInputValue() { return 32000 * tx_ampl; }
+	inline double fullScaleOutputValue() { return 32000; }
 
 	double setRxGain(double db);
 	double getRxGain(void) { return rx_gain; }

public-trunk/Transceiver52M/radioInterface.cpp

@@ -91,7 +91,6 @@ RadioInterface::RadioInterface(RadioDevice *wRadio,
   receiveOffset = wReceiveOffset;
   samplesPerSymbol = wRadioOversampling;
   mClock.set(wStartTime);
-  powerScaling = 1.0;
 }
 
 RadioInterface::~RadioInterface(void) {
@@ -109,18 +108,11 @@ double RadioInterface::fullScaleOutputValue(void) {
 
 void RadioInterface::setPowerAttenuation(double atten)
 {
-  double HWatten = mRadio->setTxGain(mRadio->maxTxGain() - atten);
-  atten -= HWatten;
-  if (atten < 1.0)
-    powerScaling = 1.0;
-  else
-    powerScaling = 1.0 / sqrt(pow(10, (atten / 10.0)));
+  mRadio->setTxGain(mRadio->maxTxGain() - atten);
 }
 
-short *RadioInterface::radioifyVector(signalVector &wVector, short *retVector, double scale, bool zeroOut) 
+short *RadioInterface::radioifyVector(signalVector &wVector, short *retVector, bool zeroOut) 
 {
-
-
   signalVector::iterator itr = wVector.begin();
   short *shortItr = retVector;
   if (zeroOut) {
@@ -130,13 +122,6 @@ short *RadioInterface::radioifyVector(signalVector &wVector, short *retVector, d
       itr++;
     }
   }
-  else if (scale != 1.0) { 
-    while (itr < wVector.end()) {
-      *shortItr++ = (short) (itr->real()*scale);
-      *shortItr++ = (short) (itr->imag()*scale);
-      itr++;
-    }
-  }
   else {
     while (itr < wVector.end()) {
       *shortItr++ = (short) (itr->real());
@@ -146,7 +131,6 @@ short *RadioInterface::radioifyVector(signalVector &wVector, short *retVector, d
   }
 
   return retVector;
-
 }
 
 void RadioInterface::unRadioifyVector(short *shortVector, signalVector& newVector)
@@ -254,7 +238,7 @@ void RadioInterface::driveTransmitRadio(signalVector &radioBurst, bool zeroBurst
 
   if (!mOn) return;
 
-  radioifyVector(radioBurst, sendBuffer+sendCursor, powerScaling, zeroBurst);
+  radioifyVector(radioBurst, sendBuffer+sendCursor, zeroBurst);
 
   sendCursor += (radioBurst.size()*2);
 

public-trunk/Transceiver52M/radioInterface.h

@@ -161,7 +161,7 @@ private:
   double powerScaling;
 
   /** format samples to USRP */ 
-  short *radioifyVector(signalVector &wVector, short *shortVector, double scale, bool zeroOut);
+  short *radioifyVector(signalVector &wVector, short *shortVector, bool zeroOut);
 
   /** format samples from USRP */
   void unRadioifyVector(short *shortVector, signalVector &wVector);