osmo-bts-trx/trx_if.c: introduce TRXD header version 0x01 support

The new version adds the following fields to the TRX2L1 message,
keeping the L12TRX message unchanged:

  +------+-----+-----+-----+--------------------+
  | RSSI | ToA | MTS | C/I | soft-bits (254..0) |
  +------+-----+-----+-----+--------------------+

  - MTS (1 octet)  - Modulation and Training Sequence info, and
  - C/I (2 octets) - Carrier-to-Interference ratio (big endian).

== Coding of MTS: Modulation and Training Sequence info

3GPP TS 45.002 version 15.1.0 defines several modulation types,
and a few sets of training sequences for each type. The most
common are GMSK and 8-PSK (which is used in EDGE).

  +-----------------+---------------------------------------+
  | 7 6 5 4 3 2 1 0 | bit numbers (value range)             |
  +-----------------+---------------------------------------+
  | . . . . . X X X | Training Sequence Code (0..7)         |
  +-----------------+---------------------------------------+
  | . X X X X . . . | Modulation, TS set number (see below) |
  +-----------------+---------------------------------------+
  | X . . . . . . . | IDLE / nope frame indication (0 or 1) |
  +-----------------+---------------------------------------+

The bit number 7 (MSB) is set to high when either nothing has been
detected, or during IDLE frames, so we can deliver noise levels,
and avoid clock gaps on the L1 side. Other bits are ignored,
and should be set to low (0) in this case.

== Coding of modulation and TS set number

GMSK has 4 sets of training sequences (see tables 5.2.3a-d),
while 8-PSK (see tables 5.2.3f-g) and the others have 2 sets.
Access and Synchronization bursts also have several synch.
sequences.

  +-----------------+---------------------------------------+
  | 7 6 5 4 3 2 1 0 | bit numbers (value range)             |
  +-----------------+---------------------------------------+
  | . 0 0 X X . . . | GMSK, 4 TS sets (0..3)                |
  +-----------------+---------------------------------------+
  | . 0 1 0 X . . . | 8-PSK, 2 TS sets (0..1)               |
  +-----------------+---------------------------------------+
  | . 0 1 1 X . . . | AQPSK, 2 TS sets (0..1)               |
  +-----------------+---------------------------------------+
  | . 1 0 0 X . . . | 16QAM, 2 TS sets (0..1)               |
  +-----------------+---------------------------------------+
  | . 1 0 1 X . . . | 32QAM, 2 TS sets (0..1)               |
  +-----------------+---------------------------------------+
  | . 1 1 1 X . . . | RESERVED (0)                          |
  +-----------------+---------------------------------------+

== C/I: Carrier-to-Interference ratio

The C/I value is computed from the training sequence of each burst,
where we can compare the "ideal" training sequence with the actual
training sequence, and then express that difference in centiBels.

== Limitations

  - The only supported modulation types are GMSK and 8-PSK.
    Messages with other modulation types will be rejected.

  - IDLE / NOPE indications are not (yet) handled.

  - The logical channel handlers do not (yet) handle optional
    fields, such as TSC and C/I. This will be implemented
    in the follow-up changes.

Change-Id: If61c71d20d590bf07bfd019afb33000a0b6135bd
Related: OS#4006

1 files changed, 14 insertions, 0 deletions

diff --git a/include/osmo-bts/scheduler.h b/include/osmo-bts/scheduler.h
index 9748d45c..4f406360 100644
--- a/include/osmo-bts/scheduler.h
+++ b/include/osmo-bts/scheduler.h
@@ -227,14 +227,28 @@ int find_sched_mframe_idx(enum gsm_phys_chan_config pchan, uint8_t tn);
 bool trx_sched_is_sacch_fn(struct gsm_bts_trx_ts *ts, uint32_t fn, bool uplink);
 extern const struct trx_sched_multiframe trx_sched_multiframes[];
 
+#define TRX_BI_F_NOPE_IND	(1 << 0)
+#define TRX_BI_F_MOD_TYPE	(1 << 1)
+#define TRX_BI_F_TS_INFO	(1 << 2)
+#define TRX_BI_F_CI_CB		(1 << 3)
+
 /*! UL burst indication with the corresponding meta info */
 struct trx_ul_burst_ind {
+	/* Field presence bitmask (see TRX_BI_F_*) */
+	uint8_t flags;
+
 	/* Mandatory fields */
 	uint32_t fn;		/*!< TDMA frame number */
 	uint8_t tn;		/*!< TDMA time-slot number */
 	int16_t toa256;		/*!< Timing of Arrival in units of 1/256 of symbol */
 	int8_t rssi;		/*!< Received Signal Strength Indication */
 
+	/* Optional fields (defined by flags) */
+	enum trx_burst_type bt;	/*!< Modulation type */
+	uint8_t tsc_set;	/*!< Training Sequence Set */
+	uint8_t tsc;		/*!< Training Sequence Code */
+	int16_t ci_cb;		/*!< Carrier-to-Interference ratio (in centiBels) */
+
 	/*! Burst soft-bits buffer */
 	sbit_t burst[EGPRS_BURST_LEN];
 	size_t burst_len;