Implemented channel hopping for CX channels
diff --git a/lib/receiver/cx_channel_hopper_impl.cc b/lib/receiver/cx_channel_hopper_impl.cc
index 10371ab..3e23910 100644
--- a/lib/receiver/cx_channel_hopper_impl.cc
+++ b/lib/receiver/cx_channel_hopper_impl.cc
@@ -25,32 +25,35 @@
#endif
#include <gnuradio/io_signature.h>
+#include <grgsm/gsmtap.h>
#include "cx_channel_hopper_impl.h"
namespace gr {
namespace gsm {
cx_channel_hopper::sptr
- cx_channel_hopper::make(int ma, int maio, int hsn)
+ cx_channel_hopper::make(const std::vector<int> &ma, int maio, int hsn)
{
- return gnuradio::get_initial_sptr
- (new cx_channel_hopper_impl(ma, maio, hsn));
+ return gnuradio::get_initial_sptr
+ (new cx_channel_hopper_impl(ma, maio, hsn));
}
/*
* The private constructor
*/
- cx_channel_hopper_impl::cx_channel_hopper_impl(int ma, int maio, int hsn)
- : gr::block("cx_channel_hopper",
- gr::io_signature::make(0, 0, 0),
- gr::io_signature::make(0, 0, 0))
+ cx_channel_hopper_impl::cx_channel_hopper_impl(const std::vector<int> &ma, int maio, int hsn)
+ : gr::block("cx_channel_hopper",
+ gr::io_signature::make(0, 0, 0),
+ gr::io_signature::make(0, 0, 0)),
+ d_ma(ma),
+ d_maio(maio),
+ d_hsn(hsn)
{
- d_ma = ma;
- d_maio = maio;
- d_hsn = hsn;
+ d_narfcn = ma.size();
- message_port_register_in(pmt::mp("CX"));
- message_port_register_out(pmt::mp("bursts"));
+ message_port_register_in(pmt::mp("CX"));
+ set_msg_handler(pmt::mp("CX"), boost::bind(&cx_channel_hopper_impl::assemble_bursts, this, _1));
+ message_port_register_out(pmt::mp("bursts"));
}
/*
@@ -60,6 +63,75 @@
{
}
+ /**
+ * Random number table used for calculating the
+ * hopping sequence. Defined in GSM 05.02.
+ */
+ unsigned char RNTABLE[114] = {
+ 48, 98, 63, 1, 36, 95, 78, 102, 94, 73, \
+ 0, 64, 25, 81, 76, 59, 124, 23, 104, 100, \
+ 101, 47, 118, 85, 18, 56, 96, 86, 54, 2, \
+ 80, 34, 127, 13, 6, 89, 57, 103, 12, 74, \
+ 55, 111, 75, 38, 109, 71, 112, 29, 11, 88, \
+ 87, 19, 3, 68, 110, 26, 33, 31, 8, 45, \
+ 82, 58, 40, 107, 32, 5, 106, 92, 62, 67, \
+ 77, 108, 122, 37, 60, 66, 121, 42, 51, 126, \
+ 117, 114, 4, 90, 43, 52, 53, 113, 120, 72, \
+ 16, 49, 7, 79, 119, 61, 22, 84, 9, 97, \
+ 91, 15, 21, 24, 46, 39, 93, 105, 65, 70, \
+ 125, 99, 17, 123 \
+ };
+
+ /*
+ * Slow Frequency Hopping (SFH) MAI calculation based
+ * on airprobe-hopping by Bogdan Diaconescu.
+ */
+ int cx_channel_hopper_impl::calculate_ma_sfh(int maio, int hsn, int n, int fn)
+ {
+ int mai = 0;
+ int s = 0;
+ int nbin = floor(log2(n) + 1);
+ int t1 = fn / 1326;
+ int t2 = fn % 26;
+ int t3 = fn % 51;
+
+ if (hsn == 0)
+ mai = (fn + maio) % n;
+ else {
+ int t1r = t1 % 64;
+ int m = t2 + RNTABLE[(hsn ^ t1r) + t3];
+ int mprim = m % (1 << nbin);
+ int tprim = t3 % (1 << nbin);
+
+ if (mprim < n)
+ s = mprim;
+ else
+ s = (mprim + tprim) % n;
+
+ mai = (s + maio) % n;
+ }
+
+ return (mai);
+ }
+
+ /**
+ * Given MA, MAIO, HSN, and FN, decide which frames
+ * to forward to the demapper.
+ */
+ void cx_channel_hopper_impl::assemble_bursts(pmt::pmt_t msg)
+ {
+ pmt::pmt_t header_plus_burst = pmt::cdr(msg);
+ gsmtap_hdr *header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst);
+
+ uint32_t frame_nr = be32toh(header->frame_number);
+ uint16_t frame_ca = be16toh(header->arfcn);
+ int mai = calculate_ma_sfh(d_maio, d_hsn, d_narfcn, frame_nr);
+
+ if(d_ma[mai] == frame_ca) {
+ message_port_pub(pmt::mp("bursts"), msg);
+ }
+ }
+
} /* namespace gsm */
} /* namespace gr */