osmocom-bb/src/target/trx_toolkit/trxd_proto.py

# -*- coding: utf-8 -*-

'''
TRXD PDU definitions based on declarative codec.
'''

# TRX Toolkit
#
# (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
# Author: Vadim Yanitskiy <vyanitskiy@sysmocom.de>
#
# All Rights Reserved
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

import codec

class Header(codec.BitFieldSet):
	''' Header constructor for TRXD PDUs. '''

	def __init__(self, ver: int, batched: bool = False):
		f = [ # Dynamically generated field list
			codec.BitField('ver', bl=4, val=ver) if not batched
				else codec.BitField.Spare(bl=4), # RFU
			codec.BitField.Spare(bl=1),
			codec.BitField('tn', bl=3),
		]

		if ver >= 2: # TRXDv2 and higher
			f.append(codec.BitField('batch', bl=1))
			f.append(codec.BitField('shadow', bl=1) if batched
			    else codec.BitField.Spare(bl=1))
			f.append(codec.BitField('trxn', bl=6))

		codec.BitFieldSet.__init__(self, set=tuple(f))

class MTS(codec.BitFieldSet):
	''' Modulation and Training Sequence. '''

	DEF_LEN = 1
	STRUCT = (
		codec.BitField('nope', bl=1),
		codec.BitField('mod', bl=4),
		codec.BitField('tsc', bl=3),
	)

	@staticmethod
	def get_burst_len(mod: int) -> int:
		''' Get burst length by modulation type. '''

		GMSK_BURST_LEN = 148

		if (mod >> 2) == 0b00: # GMSK
			return 1 * GMSK_BURST_LEN
		elif (mod >> 2) == 0b11: # AQPSK
			return 2 * GMSK_BURST_LEN
		elif (mod >> 1) == 0b010: # 8-PSK
			return 3 * GMSK_BURST_LEN
		elif (mod >> 1) == 0b100: # 16QAM
			return 4 * GMSK_BURST_LEN
		elif (mod >> 1) == 0b101: # 32QAM
			return 5 * GMSK_BURST_LEN
		elif mod == 0b0110: # GMSK (Access Burst)
			return 1 * GMSK_BURST_LEN
		raise ValueError('Unknown modulation type')

class BurstBits(codec.Buf):
	''' Soft-/hard-bits with variable length. '''

	def __init__(self, name: str, *args, **kw):
		codec.Buf.__init__(self, name, *args, **kw)

		# This field has a variable length that depends on moduletion type
		self.get_len = lambda v, _: MTS.get_burst_len(v['mod'])
		# This field is not present in NOPE / IDLE indications
		self.get_pres = lambda v: not v['nope']


class PDUv0Rx(codec.Envelope):
	STRUCT = (
		Header(ver=0),
		codec.Uint32BE('fn'),
		codec.Uint('rssi', mult=-1),
		codec.Int16BE('toa256'),
		codec.Buf('soft-bits'),
		codec.Buf('pad'), # Optional
	)

	def __init__(self, *args, **kw):
		codec.Envelope.__init__(self, *args, **kw)

		# Field 'soft-bits' is either 148 (GMSK) or 444 (8-PSK) octets long
		self.STRUCT[-2].get_len = lambda _, data: 444 if len(data) > 148 else 148

class PDUv0Tx(codec.Envelope):
	STRUCT = (
		Header(ver=0),
		codec.Uint32BE('fn'),
		codec.Uint('pwr'),
		codec.Buf('hard-bits'),
	)


class PDUv1Rx(codec.Envelope):
	STRUCT = (
		Header(ver=1),
		codec.Uint32BE('fn'),
		codec.Uint('rssi', mult=-1),
		codec.Int16BE('toa256'),
		MTS(),
		codec.Int16BE('cir'),
		BurstBits('soft-bits'),
	)

class PDUv1Tx(PDUv0Tx):
	# Same structure as PDUv0Tx, only the version is different
	STRUCT = (
		Header(ver=1),
		*PDUv0Tx.STRUCT[1:]
	)


class PDUv2Rx(codec.Envelope):
	class BPDU(codec.Envelope):
		''' Batched PDU part. '''
		STRUCT = (
			Header(ver=2, batched=True),
			MTS(),
			codec.Uint('rssi', mult=-1),
			codec.Int16BE('toa256'),
			codec.Int16BE('cir'),
			BurstBits('soft-bits'),
		)

	STRUCT = (
		Header(ver=2),
		MTS(),
		codec.Uint('rssi', mult=-1),
		codec.Int16BE('toa256'),
		codec.Int16BE('cir'),
		codec.Uint32BE('fn'),
		BurstBits('soft-bits'),
		codec.Sequence(item=BPDU()).f('bpdu'),
	)

class PDUv2Tx(codec.Envelope):
	class BPDU(codec.Envelope):
		''' Batched PDU part. '''
		STRUCT = (
			Header(ver=2, batched=True),
			MTS(),
			codec.Uint('pwr'),
			codec.Int('scpir'),
			codec.Spare('spare', len=3),
			BurstBits('hard-bits'),
		)

	STRUCT = (
		Header(ver=2),
		MTS(),
		codec.Uint('pwr'),
		codec.Int('scpir'),
		codec.Spare('spare', len=3),
		codec.Uint32BE('fn'),
		BurstBits('hard-bits'),
		codec.Sequence(item=BPDU()).f('bpdu'),
	)