diff --git a/pcu/GPRS_Components.ttcn b/pcu/GPRS_Components.ttcn
index ee2c38f..2807b92 100644
--- a/pcu/GPRS_Components.ttcn
+++ b/pcu/GPRS_Components.ttcn
@@ -44,6 +44,32 @@
 import from Native_Functions all;
 import from SGSN_Components all;
 
+type record TsTrxBtsNum {
+	uint3_t		ts_nr,
+	uint3_t		trx_nr,
+	uint8_t		bts_nr,
+	uint8_t		blk_nr
+};
+
+template (value) TsTrxBtsNum ts_TsTrxBtsNum(uint3_t ts_nr := 7,
+					    uint3_t trx_nr := 0,
+					    uint8_t bts_nr := 0,
+					    uint8_t blk_nr := 0) := {
+	ts_nr := ts_nr,
+	trx_nr := trx_nr,
+	bts_nr := bts_nr,
+	blk_nr := blk_nr
+};
+template TsTrxBtsNum tr_TsTrxBtsNum(template uint3_t ts_nr := ?,
+				    template uint3_t trx_nr := ?,
+				    template uint8_t bts_nr := ?,
+				    template uint8_t blk_nr := ?) := {
+	ts_nr := ts_nr,
+	trx_nr := trx_nr,
+	bts_nr := bts_nr,
+	blk_nr := blk_nr
+};
+
 type union PacketDlAssignChan {
 	PacketDlAssign		ccch,
 	PacketDlAssignment	pacch
@@ -281,12 +307,13 @@
 }
 
 function f_ms_rx_pkt_ass_pacch(inout GprsMS ms, out uint32_t poll_fn,
-			       template RlcmacDlBlock t_pkt_ass := ?)
+			       template RlcmacDlBlock t_pkt_ass := ?,
+			       template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return RlcmacDlBlock {
 	var RlcmacDlBlock dl_block;
 	var uint32_t dl_fn;
 
-	f_rx_rlcmac_dl_block(dl_block, dl_fn);
+	f_rx_rlcmac_dl_block(dl_block, dl_fn, nr := nr);
 	if (not match(dl_block, t_pkt_ass)) {
 		setverdict(fail, "Failed to match Packet Assignment:", t_pkt_ass);
 		f_shutdown(__BFILE__, __LINE__);
@@ -311,30 +338,34 @@
 	return dl_block;
 }
 
-function f_ms_establish_ul_tbf(inout GprsMS ms)
+function f_ms_establish_ul_tbf(inout GprsMS ms, template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var GsmRrMessage rr_imm_ass;
 
-	rr_imm_ass := f_pcuif_tx_rach_rx_imm_ass(ms.ra, ms.ra_is_11bit, ms.burst_type, ms.ta);
+	rr_imm_ass := f_pcuif_tx_rach_rx_imm_ass(ms.ra, ms.ra_is_11bit, ms.burst_type, ms.ta, nr := nr);
 	ms.ul_tbf := f_ultbf_new_from_rr_imm_ass(rr_imm_ass);
 }
 
 function f_ms_exp_dl_tbf_ass_ccch(inout GprsMS ms, template PCUIF_Sapi sapi := PCU_IF_SAPI_AGCH,
-				  template GsmRrMessage t_imm_ass := tr_IMM_TBF_ASS(true, ?, ?))
+				  template GsmRrMessage t_imm_ass := tr_IMM_TBF_ASS(true, ?, ?),
+				  template (present) TsTrxBtsNum nr := tr_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var GsmRrMessage rr_imm_ass;
 
-	rr_imm_ass := f_pcuif_rx_imm_ass(sapi, t_imm_ass);
+	rr_imm_ass := f_pcuif_rx_imm_ass(sapi, t_imm_ass, nr := nr);
 	ms.dl_tbf := f_dltbf_new_from_rr_imm_ass(rr_imm_ass, tr_PacketDlAssign(ms.tlli));
 }
 
 /* Enqueue DATA.ind (both TDMA frame and block numbers to be patched) */
-function f_ms_tx_data_ind(inout GprsMS ms, octetstring data, uint32_t fn := 0)
+function f_ms_tx_data_ind(inout GprsMS ms, octetstring data, uint32_t fn := 0,
+			  template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
-	f_pcuif_tx_data_ind(data, ms.lqual_cb, fn);
+	f_pcuif_tx_data_ind(data, ms.lqual_cb, fn, nr := nr);
 }
 
-function f_ms_tx_ul_block(inout GprsMS ms, template (value) RlcmacUlBlock ul_data, uint32_t fn := 0, template (omit) CodingScheme force_cs_mcs := omit)
+function f_ms_tx_ul_block(inout GprsMS ms, template (value) RlcmacUlBlock ul_data,
+			  uint32_t fn := 0, template (omit) CodingScheme force_cs_mcs := omit,
+			  template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return integer {
 	var octetstring data;
 	var integer padding_len;
@@ -362,12 +393,14 @@
 	data := f_pad_oct(data, cs_mcs_len, '00'O);
 
 	/* Enqueue DATA.ind (both TDMA frame and block numbers to be patched) */
-	f_ms_tx_data_ind(ms, data, fn);
+	f_ms_tx_data_ind(ms, data, fn, nr := nr);
 	return padding_len;
 }
 
 /* FIXME: Only supports sending CS-1 so far */
-function f_ms_tx_ul_data_block(inout GprsMS ms, octetstring payload, uint4_t cv := 15, boolean with_tlli := false, uint32_t fn := 0)
+function f_ms_tx_ul_data_block(inout GprsMS ms, octetstring payload,
+			       uint4_t cv := 15, boolean with_tlli := false, uint32_t fn := 0,
+			       template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return integer {
 	var template (value) RlcmacUlBlock ul_data;
 	ul_data := t_RLCMAC_UL_DATA(tfi := ms.ul_tbf.tfi,
@@ -379,11 +412,12 @@
 		ul_data.data.tlli := ms.tlli;
 	}
 	f_ultbf_inc_bsn(ms.ul_tbf);
-	return f_ms_tx_ul_block(ms, ul_data, fn);
+	return f_ms_tx_ul_block(ms, ul_data, fn, nr := nr);
 }
 
 /* Send random payload for last "num_blocks" blocks in Ul TBF (ending with CV=0). */
-function f_ms_tx_ul_data_block_multi(inout GprsMS ms, integer num_blocks := 1, boolean with_tlli := false)
+function f_ms_tx_ul_data_block_multi(inout GprsMS ms, integer num_blocks := 1, boolean with_tlli := false,
+				     template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return octetstring {
 	var octetstring total_payload := ''O;
 
@@ -395,7 +429,7 @@
 		if (cv > g_bs_cv_max) {
 			cv := 15;
 		}
-		padding_len :=  f_ms_tx_ul_data_block(ms, payload, cv := cv, with_tlli := with_tlli)
+		padding_len := f_ms_tx_ul_data_block(ms, payload, cv := cv, with_tlli := with_tlli, nr := nr);
 		total_payload := total_payload & payload & f_pad_oct(''O, padding_len, '00'O);
 	}
 	return total_payload;
@@ -494,11 +528,12 @@
 }
 
 ////////////////////////
-// OLD APIs
+// Low level APIs
 ////////////////////////
 
 function f_pcuif_rx_imm_ass(template PCUIF_Sapi sapi := PCU_IF_SAPI_AGCH,
-			    template GsmRrMessage t_imm_ass := ?)
+			    template GsmRrMessage t_imm_ass := ?,
+			    template (present) TsTrxBtsNum nr := tr_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return GsmRrMessage {
 	var GsmRrMessage rr_imm_ass;
 	var PCUIF_Message pcu_msg;
@@ -507,7 +542,7 @@
 
 	T.start(2.0);
 	alt {
-	[] BTS.receive(tr_PCUIF_DATA_REQ(bts_nr := 0, trx_nr := 0, ts_nr := 0,
+	[] BTS.receive(tr_PCUIF_DATA_REQ(nr.bts_nr, nr.trx_nr, ts_nr := 0,
 					 sapi := sapi, data := ?)) -> value pcu_msg {
 		/* On PCH the payload is prefixed with paging group (3 octets): skip it.
 		 * TODO: add an additional template parameter, so we can match it. */
@@ -549,7 +584,8 @@
 function f_pcuif_tx_rach_rx_imm_ass(uint16_t ra := bit2int(chan_req_def),
 				    uint8_t is_11bit := 0,
 				    PCUIF_BurstType burst_type := BURST_TYPE_0,
-				    TimingAdvance ta := 0)
+				    TimingAdvance ta := 0,
+				    template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return GsmRrMessage {
 	var uint32_t fn;
 
@@ -558,7 +594,7 @@
 
 	/* Send RACH.ind */
 	log("Sending RACH.ind on fn=", fn, " with RA=", ra, ", TA=", ta);
-	BTS.send(ts_PCUIF_RACH_IND(bts_nr := 0, trx_nr := 0, ts_nr := 0,
+	BTS.send(ts_PCUIF_RACH_IND(nr.bts_nr, nr.trx_nr, ts_nr := 0,
 				   ra := ra, is_11bit := is_11bit,
 				   burst_type := burst_type,
 				   fn := fn, arfcn := 871,
@@ -569,15 +605,16 @@
 	 * we assume that 11 bit RA always contains EGPRS Packet Channel Request. */
 	if (is_11bit != 0) { ra := 127; }
 
-	/* Expect Immediate (TBF) Assignment on TS0/AGCH */
-	return f_pcuif_rx_imm_ass(PCU_IF_SAPI_AGCH, tr_IMM_TBF_ASS(false, ra, fn));
+	/* Expect Immediate (TBF) Assignment on the same TS/TRX/BTS */
+	return f_pcuif_rx_imm_ass(PCU_IF_SAPI_AGCH, tr_IMM_TBF_ASS(false, ra, fn), nr);
 }
 
 /* Enqueue DATA.ind (both TDMA frame and block numbers to be patched) */
-function f_pcuif_tx_data_ind(octetstring data, int16_t lqual_cb := 0, uint32_t fn := 0)
+function f_pcuif_tx_data_ind(octetstring data, int16_t lqual_cb := 0, uint32_t fn := 0,
+			     template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var template RAW_PCU_EventParam ev_param := {tdma_fn := ? };
-	BTS.send(ts_PCUIF_DATA_IND(bts_nr := 0, trx_nr := 0, ts_nr := 7, block_nr := 0,
+	BTS.send(ts_PCUIF_DATA_IND(nr.bts_nr, nr.trx_nr, nr.ts_nr, nr.blk_nr,
 				   sapi := PCU_IF_SAPI_PDTCH, data := data,
 				   fn := fn, arfcn := 871, lqual_cb := lqual_cb));
 	if (fn != 0) {
@@ -587,18 +624,20 @@
 }
 
 /* Enqueue RTS.req, expect DATA.req with UL ACK from the PCU */
-function f_pcuif_rx_data_req(out PCUIF_Message pcu_msg)
+function f_pcuif_rx_data_req(out PCUIF_Message pcu_msg,
+			     template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
-	BTS.send(ts_PCUIF_RTS_REQ(bts_nr := 0, trx_nr := 0, ts_nr := 7,
+	BTS.send(ts_PCUIF_RTS_REQ(nr.bts_nr, nr.trx_nr, nr.ts_nr,
 				  sapi := PCU_IF_SAPI_PDTCH, fn := 0,
-				  arfcn := 871, block_nr := 0));
-	BTS.receive(tr_PCUIF_DATA_REQ(bts_nr := 0, trx_nr := 0, ts_nr := 7,
+				  arfcn := 871, block_nr := nr.blk_nr));
+	BTS.receive(tr_PCUIF_DATA_REQ(nr.bts_nr, nr.trx_nr, nr.ts_nr,
 				      sapi := PCU_IF_SAPI_PDTCH)) -> value pcu_msg;
 }
 
 /* Expect a Paging Request Type 1 from PCU on PCUIF on specified sapi.  */
 function f_pcuif_rx_pch_pag_req1(template MobileIdentityV mi1 := ?,
-				 template integer pag_group := ?)
+				 template integer pag_group := ?,
+				 template (present) TsTrxBtsNum nr := tr_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT return GsmRrMessage {
 	var GsmRrMessage rr_pag_req1;
 	var PCUIF_Message pcu_msg;
@@ -606,7 +645,7 @@
 	var integer pag_group_rx;
 	var octetstring macblock;
 
-	BTS.receive(tr_PCUIF_DATA_REQ(bts_nr := 0, trx_nr := 0, ts_nr := 0,
+	BTS.receive(tr_PCUIF_DATA_REQ(nr.bts_nr, nr.trx_nr, nr.ts_nr,
 				      sapi := PCU_IF_SAPI_PCH)) -> value pcu_msg;
 
 	/* First 3 bytes contain IMSI suffix to calculate paging group: */
@@ -633,10 +672,12 @@
 	return rr_pag_req1;
 }
 
-function f_rx_rlcmac_dl_block(out RlcmacDlBlock dl_block, out uint32_t dl_fn, template (present) CodingScheme exp_cs_mcs := ?)
+function f_rx_rlcmac_dl_block(out RlcmacDlBlock dl_block, out uint32_t dl_fn,
+			      template (present) CodingScheme exp_cs_mcs := ?,
+			      template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var PCUIF_Message pcu_msg;
-	f_pcuif_rx_data_req(pcu_msg);
+	f_pcuif_rx_data_req(pcu_msg, nr := nr);
 	dl_block := dec_RlcmacDlBlock(pcu_msg.u.data_req.data);
 	dl_fn := pcu_msg.u.data_req.fn;
 
@@ -650,11 +691,12 @@
 
 function f_rx_rlcmac_dl_block_exp_ack_nack(out RlcmacDlBlock dl_block, out uint32_t poll_fn,
 					   template RlcmacDlBlock acknack_tmpl := (tr_RLCMAC_UL_ACK_NACK_GPRS(ul_tfi := ?),
-										   tr_RLCMAC_UL_ACK_NACK_EGPRS(ul_tfi := ?)))
+										   tr_RLCMAC_UL_ACK_NACK_EGPRS(ul_tfi := ?)),
+					   template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var uint32_t dl_fn;
 
-	f_rx_rlcmac_dl_block(dl_block, dl_fn);
+	f_rx_rlcmac_dl_block(dl_block, dl_fn, nr := nr);
 	if (match(dl_block, acknack_tmpl)) {
 		poll_fn := f_rrbp_ack_fn(dl_fn, dl_block.ctrl.mac_hdr.rrbp);
 		return;
@@ -663,22 +705,24 @@
 	f_shutdown(__BFILE__, __LINE__);
 }
 
-function f_rx_rlcmac_dl_block_exp_dummy(out RlcmacDlBlock dl_block)
+function f_rx_rlcmac_dl_block_exp_dummy(out RlcmacDlBlock dl_block,
+					template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var uint32_t dl_fn;
 
-	f_rx_rlcmac_dl_block(dl_block, dl_fn);
+	f_rx_rlcmac_dl_block(dl_block, dl_fn, nr := nr);
 	if (not match(dl_block, tr_RLCMAC_DUMMY_CTRL())) {
 		setverdict(fail, "Failed to match Packet DUMMY DL");
 		f_shutdown(__BFILE__, __LINE__);
 	}
 }
 
-function f_rx_rlcmac_dl_block_exp_pkt_pag_req(out RlcmacDlBlock dl_block)
+function f_rx_rlcmac_dl_block_exp_pkt_pag_req(out RlcmacDlBlock dl_block,
+					      template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	var uint32_t dl_fn;
 
-	f_rx_rlcmac_dl_block(dl_block, dl_fn);
+	f_rx_rlcmac_dl_block(dl_block, dl_fn, nr := nr);
 	if (not match(dl_block, tr_RLCMAC_PACKET_PAG_REQ())) {
 		setverdict(fail, "Failed to match Packet Paging Request: ", dl_block, " vs ", tr_RLCMAC_PACKET_PAG_REQ());
 		f_shutdown(__BFILE__, __LINE__);
@@ -754,13 +798,14 @@
 function f_rx_rlcmac_dl_block_exp_data(out RlcmacDlBlock dl_block, out uint32_t dl_fn,
 				       template (present) octetstring data := ?,
 				       template (present) uint7_t exp_bsn := ?,
-				       template (present) CodingScheme exp_cs := ?)
+				       template (present) CodingScheme exp_cs := ?,
+				       template (value) TsTrxBtsNum nr := ts_TsTrxBtsNum)
 runs on MS_BTS_IFACE_CT {
 	/* FIXME: ideally we should use an alt statement with timeout here, rather than
 	 * having +100500 layers of abstraction. This would facilitate developing the
 	 * multi-TBF/-TRX/-BTS tests, where you cannot expect that the first received
 	 * block is exactly what you need. */
-	f_rx_rlcmac_dl_block(dl_block, dl_fn);
+	f_rx_rlcmac_dl_block(dl_block, dl_fn, nr := nr);
 
 	/* Make sure it's either GPRS or EGPRS data block */
 	if (not match(dl_block, tr_RLCMAC_DATA)) {