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fixeria gerrit-no-reply at lists.osmocom.orgfixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-gsm-manuals/+/22867 )
Change subject: TRXD: add initial proposal for TRXDv2
......................................................................
TRXD: add initial proposal for TRXDv2
Change-Id: I03b2beeb535848b31fd629ba3cd330b43072c08b
Related: SYS#4895, OS#4941, OS#4006
---
M common/chapters/trx_if.adoc
1 file changed, 217 insertions(+), 2 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-gsm-manuals refs/changes/67/22867/1
diff --git a/common/chapters/trx_if.adoc b/common/chapters/trx_if.adoc
index d1aa566..c9d502e 100644
--- a/common/chapters/trx_if.adoc
+++ b/common/chapters/trx_if.adoc
@@ -18,6 +18,9 @@
The corresponding interface for every socket is at `P+100` on the BTS side.
+NOTE: Starting from TRXDv2, it's possible to use only one socket for all
+channels. See <<trx_if_pdu_batching>> for more details.
+
[[trx_if_clock_ind]]
=== Indications on the Master Clock Interface
@@ -354,7 +357,7 @@
=== TRXD protocol
-PDUs on the data interface carry one radio burst per one UDP packet.
+PDUs on the data interface carry one or multiple radio bursts per one UDP packet.
Two kinds of TRXD PDU exist:
* `TRX -> L1` (from transceiver to the L1): Uplink messages received from the MS,
@@ -386,6 +389,11 @@
** New field: MTS (Modulation and Training Sequence);
** New field: C/I (Carrier-to-interface) ratio;
** Downlink messages mostly unchanged.
+* TRXDv2 (proposed in January 2021):
+** Introduced the concept of burst batching (many bursts in one message);
+** Changed the field ordering (facilitating aligned access);
+** New field: batching indicator;
+** New field: SCPIR for VAMOS.
==== Uplink Data Burst
@@ -448,6 +456,47 @@
}
----
+.TRXDv2 Uplink message structure
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: VER(2)
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-23: SPARE (0)
+ 24-31: RSSI
+ 32-47: TOA256
+ 48-63: C/I
+ 64-95: FN
+ 96-127: Soft-bits
+}
+----
+
+.TRXDv2 NOPE / IDLE indication message structure
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: VER(2)
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-23: SPARE (0)
+ 24-31: RSSI
+ 32-47: TOA256
+ 48-63: C/I
+ 64-95: FN
+}
+----
+
VER: 4 bits::
TRXD header version, common for both `TRX -> L1` and `L1 -> TRX` directions.
@@ -557,7 +606,7 @@
==== Downlink Data Burst
-.TRXD Downlink data burst message structure
+.TRXDv0 and TRXDv1 Downlink data burst message structure
[packetdiag]
----
{
@@ -573,6 +622,45 @@
}
----
+.TRXDv2 Downlink data burst message structure
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: VER
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-23: SPARE (0)
+ 24-31: PWR
+ 32-63: FN
+ 64-95: Hard-bits
+}
+----
+
+.TRXDv2 Downlink data burst message structure for AQPSK
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: VER
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-19: SPARE (0)
+ 20-23: SCPIR
+ 24-31: PWR
+ 32-63: FN
+ 64-95: Hard-bits for V0/V1
+}
+----
+
VER: 4 bits::
TRXD header version, common for both `TRX -> L1` and `L1 -> TRX` directions.
@@ -583,6 +671,10 @@
Reserved, shall be 0. It can be used in the future to extend the TDMA TN range
to (0..15), in case anybody would need to transfer UMTS bursts.
+MTS: 8 bits (1 byte)::
+Contains the Modulation and Training Sequence information. See <<coding-mts>>
+for more information on the encoding.
+
FN: 32 bits (4 bytes)::
GSM frame number, big endian.
@@ -591,6 +683,129 @@
in dB. The absolute value is set on the control interface, so the resulting
power is calculated as follows: `full_scale - (absolute_red + relative_red)`.
+SCPIR: 4 bits::
+SCPIR (Subchannel Power Imbalance Ratio) - the ratio of power between Q and I
+channels for a VAMOS pair. Value range: 0 .. 10. This field shall be present
+when `MTC` field indicates the use of _AQPSK_ modulation. Otherwise all bits
+shall be set to 0.
+
Hard-bits: 148 bytes for GSM, 444 bytes for EDGE::
Contains the downlink burst. Each hard-bit (1 or 0) of the burst is represented
using one byte (0x01 or 0x00 respectively).
+
+Hard-bits for V0/V1: 148 bytes each, 296 bytes total::
+This field contains two sequences of hard-bits (148 bytes each) for an _AQPSK_
+moduleted burst (VAMOS mode). The two sequences are *not* interleaved: one
+complete sequence for subscriber `V0` takes the first 148 bytes, then another
+complete sequence for subscriber `V1` takes the subsequent 148 bytes.
+
+[[trx_if_pdu_batching]]
+==== Burst batching
+
+Starting from TRXDv2, it's possible to combine several bursts into a single
+PDU - this is called _burst batching_. The purpose of _burst batching_ is
+to reduce socket load and eliminate possible PDU reordering, especially in
+a multi-TRX setup.
+
+.TRXDv2 Uplink PDU structure (batched part)
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: TRXNR
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-23: SPARE (0)
+ 24-31: RSSI
+ 32-47: TOA256
+ 48-63: C/I
+ 64-95: Soft-bits
+}
+----
+
+.TRXDv2 Downlink PDU structure (batched part)
+[packetdiag]
+----
+{
+ colwidth = 32
+ node_height = 40
+
+ 0-3: TRXNR
+ 4: RES
+ 5-7: TN
+ 8-15: MTS
+ 16: BATCH
+ 17-23: SPARE (0)
+ 24-31: PWR
+ 32-63: Hard-bits
+}
+----
+
+TRXNR: 4 bits::
+Transceiver number (FIXME).
+
+BATCH: 1 bit::
+This bit indicates whether a batched burst follows.
+
+The ordering of bursts may be different with the only requirement that all
+_batched_ bursts must belong to the same TDMA frame number indicated in the
+first part. Thus the following combinations are possible:
+
+* a) one PDU contains bursts with the same TDMA timeslot number for all
+transceivers (8 PDUs per a TDMA frame);
+* one PDU contains complete TDMA frame with bursts for all 8 timeslots:
+** b) either for a single transceiver (N PDUs per a TDMA frame),
+** c) or for all transceivers (one PDU per a TDMA frame).
+
+.Example: batched PDU structure for a)
+----
++-------+----------------+----------------------------------+
+| TRX=0 | TDMA FN=F TN=T | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=1 | TDMA FN=F TN=T | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=2 | TDMA FN=F TN=T | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=T | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+----
+
+.Example: batched PDU structure for b)
+----
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=0 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=1 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=2 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=7 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+----
+
+.Example: batched PDU structure for c)
+----
++-------+----------------+----------------------------------+
+| TRX=0 | TDMA FN=F TN=0 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=0 | TDMA FN=F TN=1 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=0 | TDMA FN=F TN=2 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=5 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=6 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+| TRX=N | TDMA FN=F TN=7 | Hard-/Soft-bits |
++-------+----------------+----------------------------------+
+----
--
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Gerrit-Project: osmo-gsm-manuals
Gerrit-Branch: master
Gerrit-Change-Id: I03b2beeb535848b31fd629ba3cd330b43072c08b
Gerrit-Change-Number: 22867
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-MessageType: newchange
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