gprs_gb: Add more comments to code

Change-Id: I89ab4d8be112ca44a64fecbadc60ca8ac3e6bbea
diff --git a/gprs_gb/Test.ttcn b/gprs_gb/Test.ttcn
index 732b3f5..e9cb40e 100644
--- a/gprs_gb/Test.ttcn
+++ b/gprs_gb/Test.ttcn
@@ -156,6 +156,7 @@
 
 	const octetstring gmm_auth_req := '081200102198c72477ea104895e8b959acc58b108182'O;
 
+	/* Wrap downlink GMM into LLC, encode + send it via BSSGP to PCU */
 	function tx_gmm(BIT1 c_r, in octetstring gmm_pdu, BIT4 sapi := c_LLC_SAPI_LLGMM) runs on dummy_CT {
 		var PDU_LLC llc;
 
@@ -171,6 +172,7 @@
 		BSSGP.send(ts_BSSGP_DL_UD(g_mmctx.tlli, enc_PDU_LLC(llc)));
 	}
 
+	/* Establish BSSGP connection to PCU */
 	function f_bssgp_establish() runs on dummy_CT {
 		timer T:= 60.0;
 
@@ -185,6 +187,7 @@
 		log("BSSGP successfully initialized");
 	}
 
+	/* Send PS-PAGING via BSSGP to PCU, expect it to show up on L1/Um */
 	testcase TC_paging() runs on dummy_CT {
 		var hexstring imsi := '262420123456789'H;
 		var BssgpBvci bvci := 196;
@@ -207,6 +210,7 @@
 		}
 	}
 
+	/* Establish an UL TBF: Tune to ARFCN, send RACH, receive AGCH, enable TBF Rx */
 	function f_establish_ul_tbf() runs on dummy_CT {
 		timer T := 5.0;
 		var BCCH_tune_req tune_req := { { false, 871 }, true };
@@ -225,6 +229,7 @@
 		T.stop;
 	}
 
+	/* Template fro uplink Data block */
 	template RlcmacUlBlock t_RLCMAC_UL_DATA(template uint5_t tfi, template uint4_t cv, template uint7_t bsn,
 						template LlcBlocks blocks := {}, template boolean stall := false) := {
 		data := {
@@ -260,6 +265,7 @@
 		usf := usf
 	}
 
+	/* Receive Template for Downlink ACK/NACK */
 	template RlcmacDlBlock tr_RLCMAC_ACK_NACK(template uint5_t ul_tfi, template GprsTlli tlli := ?) := {
 		ctrl := {
 			mac_hdr := {
@@ -293,12 +299,14 @@
 		}
 	}
 
+	/* Template for Uplink MAC Control Header */
 	template UlMacCtrlHeader t_RLCMAC_UlMacCtrlH(template MacPayloadType pt, template boolean retry := false) := {
 		payload_type := pt,
 		spare := '00000'B,
 		retry := retry
 	}
 
+	/* Template for Uplink Conntrol ACK */
 	template RlcmacUlBlock ts_RLCMAC_CTRL_ACK(GprsTlli tlli, CtrlAck ack := MS_RCVD_TWO_RLC_SAME_RTI_DIFF_RBSN) := {
 		ctrl := {
 			mac_hdr := t_RLCMAC_UlMacCtrlH(MAC_PT_RLCMAC_NO_OPT),
@@ -314,6 +322,7 @@
 		}
 	}
 
+	/* Template for a LlcBlock (part of a LLC frame inside RlcMac?lDataBlock */
 	template LlcBlock t_RLCMAC_LLCBLOCK(octetstring data, BIT1 more := '0'B, boolean e := true) := {
 		hdr := {
 			length_ind := lengthof(data),
@@ -323,11 +332,13 @@
 		payload := data
 	}
 
+	/* compute a random TLLI; FIXME: what about TLLI prefix / local/foreign/...? */
 	function f_random_tlli() return GprsTlli {
 		var GprsTlli tlli := float2int(rnd()* 4294967295.0);
 		return tlli;
 	}
 
+	/* Send a single Uplink Block via Um; Verify reception on BSSGP; Expect UL_ACK on Um */
 	function f_single_ul_block(GprsCodingScheme cs) runs on dummy_CT {
 		var GprsTlli tlli := f_random_tlli();
 		var octetstring payload := '01020304'O;