diff --git a/bts/BTS_Tests_LAPDm.ttcn b/bts/BTS_Tests_LAPDm.ttcn
index 07b785e88..ffa3aa939 100644
--- a/bts/BTS_Tests_LAPDm.ttcn
+++ b/bts/BTS_Tests_LAPDm.ttcn
@@ -845,7 +845,97 @@ testcase TC_segm_concat_sacch() runs on test_CT {
 	f_testmatrix_each_chan(pars, refers(f_TC_segm_concat_sacch));
 }
 
+/* TS 04.06 Section 5.8.2.1 */
+private function f_n200_by_chan_nr(RslChannelNr chan_nr, RslLinkId link_id) return integer {
+	/* SACCH irrespective of physical channel type */
+	if (match(link_id, tr_RslLinkID_SACCH(?))) {
+		return 5;
+	}
+	/* DCCH below */
+	select (chan_nr) {
+	case (t_RslChanNr_SDCCH4(?, ?)) { return 23; }
+	case (t_RslChanNr_SDCCH8(?, ?)) { return 23; }
+	case (t_RslChanNr_Bm(?)) { return 34; }
+	case (t_RslChanNr_Lm(?, ?)) { return 29; }
+	}
+	setverdict(fail, "Unknown chan_nr ", chan_nr, " or link_id ", link_id);
+	return -1;
+}
 
+/* Test if there are exactly N200+1 transmissions of I frames; inspired by 25.2.4.1 */
+private function f_TC_t200_n200(charstring id) runs on ConnHdlr {
+	var RslLinkId link_id := valueof(ts_RslLinkID_DCCH(0));
+	var integer sapi := link_id.sapi;
+	var boolean is_sacch := false;
+	if (link_id.c == SACCH) {
+		is_sacch := true;
+	}
+	var integer n200 := f_n200_by_chan_nr(g_chan_nr, link_id);
+	var integer num_retrans := 0;
+	timer T := 3.0;
+	var default d;
+
+	fp_common_init();
+
+	/* some common altstep for meas res and other background noise */
+	d := activate(as_ignore_background(true));
+	RSL.clear;
+	LAPDM.clear;
+
+	var octetstring l3_mo := f_rnd_octstring(20);
+	LAPDM.send(t_PH_DATA(0, is_sacch, ts_LAPDm_SABM(sapi, c_r:=cr_MO_CMD, p:=true, l3:=l3_mo)));
+	RSL.receive(tr_RSL_EST_IND(g_chan_nr, link_id, l3_mo));
+	LAPDM.receive(t_PH_DATA(0, is_sacch, tr_LAPDm_UA(sapi, cr_MT_RSP, f:=true, l3:=l3_mo)));
+
+	var octetstring l3_mt := f_rnd_octstring(20);
+	RSL.send(ts_RSL_DATA_REQ(g_chan_nr, link_id, l3_mt));
+	/* first transmission, P = 0 */
+	LAPDM.receive(t_PH_DATA(0, is_sacch, tr_LAPDm_I(sapi, c_r:=cr_MT_CMD, p:=false,
+							nr:=0, ns:=0, l3:=l3_mt)));
+	deactivate(d);
+
+	alt {
+	/* re-transmission, P = 1 */
+	[] LAPDM.receive(t_PH_DATA(0, is_sacch,
+				tr_LAPDm_I(sapi, c_r:=cr_MT_CMD, p:=true, nr:=0, ns:=0, l3:=l3_mt))) {
+		num_retrans := num_retrans + 1;
+		if (num_retrans < n200) {
+			repeat;
+		} else if (num_retrans == n200) {
+			T.start; /* wait for some more time if there are more retransmissions */
+			repeat;
+		} else {
+			/* break */
+		}
+		}
+	[] LAPDM.receive(t_PH_DATA(0, false, tr_LAPDm_I(sapi, ?, ?, ?, ?, ?))) {
+		setverdict(fail, "Received unexpected I frame");
+		}
+	[not is_sacch] as_lapdm_acch();
+	[is_sacch] as_lapdm_dcch();
+	[] as_lapdm_idle();
+	[] as_rsl_meas_rep();
+	[num_retrans == n200] RSL.receive(tr_RSL_ERROR_IND(g_chan_nr, link_id, '01'O)) {
+		/* break */
+		}
+	[] T.timeout {
+		setverdict(fail, "Missing RSL RLL ERROR INDICATION");
+		}
+	}
+
+	if (num_retrans == n200) {
+		setverdict(pass, "Received ", num_retrans, " on channel ", g_chan_nr, " link ", link_id);
+	} else if (num_retrans < n200) {
+		setverdict(fail, "Too few retransmissions (", num_retrans, "); N200=", n200,
+			   " on channel ", g_chan_nr, " link ", link_id);
+	}
+
+	fp_common_fini();
+}
+testcase TC_t200_n200() runs on test_CT {
+	var ConnHdlrPars pars := valueof(t_Pars(t_RslChanNr_Bm(1), ts_RSL_ChanMode_SIGN));
+	f_testmatrix_each_chan(pars, refers(f_TC_t200_n200));
+}
 
 control {
 	execute(TC_foo());
@@ -863,6 +953,7 @@ control {
 	execute(TC_iframe_timer_recovery());
 	execute(TC_segm_concat_dcch());
 	execute(TC_segm_concat_sacch());
+	execute(TC_t200_n200());
 }
 
 }