diff --git a/README.md b/README.md
index 2cd0f44..2d14f96 100644
--- a/README.md
+++ b/README.md
@@ -37,11 +37,18 @@ then used to generate the digitized I/Q samples for the GPS signal.
 
 The bladeRF command line interface requires I/Q pairs stored as signed 
 16-bit integers, while the hackrf_transfer and gps-sdr-sim-uhd.py
-supports signed bytes.
+support signed bytes.
 
 HackRF and bladeRF require 2.6 MHz sample rate, while the USRP2 requires
 2.5 MHz (an even integral decimator of 100 MHz).
 
+The simulation start time can be specified if the corresponding set of ephemerides
+is available. Otherwise the first time of ephemeris in the RINEX navigation file
+is selected.
+
+The maximum simulation duration time is defined by USER_MOTION_SIZE to 
+the prevent output file from getting too large.
+
 ```
 Usage: gps-sdr-sim [options]
 Options:
@@ -49,23 +56,26 @@ Options:
   -u <user_motion> User motion file (dynamic mode)
   -g <nmea_gga>    NMEA GGA stream (dynamic mode)
   -l <location>    Lat,Lon,Hgt (static mode) e.g. 30.286502,120.032669,100
+  -t <date,time>   Scenario start time YYYY/MM/DD,hh:mm:ss
+  -d <duration>    Duration [sec] (max: 300)
   -o <output>      I/Q sampling data file (default: gpssim.bin)
   -s <frequency>   Sampling frequency [Hz] (default: 2600000)
-  -b <iq_bits>     I/Q data format [8/16] (default: 8)
+  -b <iq_bits>     I/Q data format [8/16] (default: 16)
+  -v <verbose>     Show details about simulated channels
 ```
 
 The user motion can be specified in either dynamic or static mode:
 
 ```
-> gps-sdr-sim -e brdc3540.14n -u circle.csv -b 16
+> gps-sdr-sim -e brdc3540.14n -u circle.csv
 ```
 
 ```
-> gps-sdr-sim -e brdc3540.14n -g triumphv3.txt -b 16
+> gps-sdr-sim -e brdc3540.14n -g triumphv3.txt
 ```
 
 ```
-> gps-sdr-sim -e brdc3540.14n -l 30.286502,120.032669,100 -b 16
+> gps-sdr-sim -e brdc3540.14n -l 30.286502,120.032669,100
 ```
 
 ### Transmitting the samples