diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index f9361a0..646e5bf 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -307,6 +307,7 @@
 	uint8_t trx_nr,
 	RslChannelNr chan_nr,
 	RSL_IE_ChannelMode chan_mode,
+	RSL_IE_MultirateCfg mr_conf optional,
 	float t_guard,
 	ConnL1Pars l1_pars,
 	TestSpecUnion spec optional,
@@ -853,6 +854,10 @@
 		ch_act.ies := ch_act.ies & { valueof(t_RSL_IE(RSL_IE_ENCR_INFO, RSL_IE_Body:{encr_info :=
 encr_info})) };
 	}
+	if (mode.coding_alg_rate == RSL_CMOD_SP_GSM3) {
+		ch_act.ies := ch_act.ies & { valueof(t_RSL_IE(RSL_IE_MR_CONFIG,
+							      RSL_IE_Body:{multirate_cfg := g_pars.mr_conf})) };
+	}
 	ch_act.ies := ch_act.ies & more_ies;
 	f_rsl_transceive(ch_act, tr_RSL_CHAN_ACT_ACK(g_chan_nr), "RSL CHAN ACT");
 }
@@ -869,6 +874,7 @@
 	trx_nr := trx_nr,
 	chan_nr := valueof(chan_nr),
 	chan_mode := valueof(chan_mode),
+	mr_conf := omit,
 	t_guard := t_guard,
 	l1_pars := {
 		dtx_enabled := false,
@@ -2510,12 +2516,16 @@
 	/* Send TCH Mode Request to the L1 if needed */
 	if (match(g_pars.chan_mode.spd_ind, (RSL_SPDI_SPEECH, RSL_SPDI_DATA))) {
 		var L1ctlTchMode tch_mode;
+		var uint8_t amr_start_codec := 0;
+		var BIT8 amr_codecs_bitmask := '00000000'B;
 
 		select (g_pars.chan_mode.coding_alg_rate) {
 		case (RSL_CMOD_NO_RESOURCE) { tch_mode := L1CTL_CHAN_MODE_SIGN; }
 		case (RSL_CMOD_SP_GSM1) { tch_mode := L1CTL_CHAN_MODE_SPEECH_V1; }
 		case (RSL_CMOD_SP_GSM2) { tch_mode := L1CTL_CHAN_MODE_SPEECH_V2; }
-		case (RSL_CMOD_SP_GSM3) { tch_mode := L1CTL_CHAN_MODE_SPEECH_V3; }
+		case (RSL_CMOD_SP_GSM3) { tch_mode := L1CTL_CHAN_MODE_SPEECH_V3;
+					  amr_codecs_bitmask := g_pars.mr_conf.amr_codec_modes;
+					}
 		case else {
 			log("RSL channel mode := ", g_pars.chan_mode.coding_alg_rate,
 			    " is not supported by the L1, falling back to signalling");
@@ -2523,7 +2533,10 @@
 			}
 		}
 
-		f_L1CTL_TCH_MODE(L1CTL, tch_mode);
+		f_L1CTL_TCH_MODE(L1CTL,
+				 ts_L1CTL_TCH_MODE_REQ(tch_mode,
+						       amr_start_codec := amr_start_codec,
+						       amr_codecs_bitmask := amr_codecs_bitmask));
 	}
 
 	g_first_meas_res := true;