diff --git a/src/tbf_ul_ass_fsm.c b/src/tbf_ul_ass_fsm.c
new file mode 100644
index 0000000..a55309d
--- /dev/null
+++ b/src/tbf_ul_ass_fsm.c
@@ -0,0 +1,309 @@
+/* tbf_ul_ass_fsm.c
+ *
+ * Copyright (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * Author: Pau Espin Pedrol <pespin@sysmocom.de>
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#include <unistd.h>
+
+#include <talloc.h>
+
+#include <osmocom/core/bitvec.h>
+
+#include <tbf_ul_ass_fsm.h>
+#include <gprs_rlcmac.h>
+#include <gprs_debug.h>
+#include <gprs_ms.h>
+#include <encoding.h>
+#include <bts.h>
+#include <tbf.h>
+#include <tbf_ul.h>
+
+#define X(s) (1 << (s))
+
+const struct osmo_tdef_state_timeout tbf_ul_ass_fsm_timeouts[32] = {
+	[TBF_UL_ASS_NONE] = {},
+	[TBF_UL_ASS_SEND_ASS] = {},
+	[TBF_UL_ASS_SEND_ASS_REJ] = {},
+	[TBF_UL_ASS_WAIT_ACK] = {},
+};
+
+const struct value_string tbf_ul_ass_fsm_event_names[] = {
+	{ TBF_UL_ASS_EV_SCHED_ASS, "SCHED_ASS" },
+	{ TBF_UL_ASS_EV_SCHED_ASS_REJ, "SCHED_ASS_REJ" },
+	{ TBF_UL_ASS_EV_CREATE_RLCMAC_MSG, "CREATE_RLCMAC_MSG" },
+	{ TBF_UL_ASS_EV_RX_ASS_CTRL_ACK, "RX_ASS_CTRL_ACK" },
+	{ TBF_UL_ASS_EV_ASS_POLL_TIMEOUT, "ASS_POLL_TIMEOUT" },
+	{ 0, NULL }
+};
+
+static struct msgb *create_packet_access_reject(const struct tbf_ul_ass_fsm_ctx *ctx)
+{
+	struct msgb *msg;
+	struct GprsMs *ms = tbf_ms(ctx->tbf);
+
+	msg = msgb_alloc(GSM_MACBLOCK_LEN, "rlcmac_ul_ass_rej");
+
+	struct bitvec *packet_access_rej = bitvec_alloc(GSM_MACBLOCK_LEN, ctx->tbf);
+
+	bitvec_unhex(packet_access_rej, DUMMY_VEC);
+
+	write_packet_access_reject(packet_access_rej, ms_tlli(ms),
+				   osmo_tdef_get(ms->bts->T_defs_bts, 3172, OSMO_TDEF_MS, -1));
+
+	bts_do_rate_ctr_inc(ms->bts, CTR_PKT_ACCESS_REJ);
+
+	bitvec_pack(packet_access_rej, msgb_put(msg, GSM_MACBLOCK_LEN));
+
+	bitvec_free(packet_access_rej);
+	return msg;
+
+}
+
+struct msgb *create_packet_ul_assign(const struct tbf_ul_ass_fsm_ctx *ctx,
+				     const struct tbf_ul_ass_ev_create_rlcmac_msg_ctx *d)
+{
+	struct msgb *msg = NULL;
+	struct gprs_rlcmac_ul_tbf *new_tbf = NULL;
+	RlcMacDownlink_t *mac_control_block = NULL;
+	struct GprsMs *ms = tbf_ms(ctx->tbf);
+	uint32_t tlli;
+	int rc;
+	unsigned int rrbp;
+	uint32_t new_poll_fn;
+
+	rc = tbf_check_polling(ctx->tbf, d->fn, d->ts, &new_poll_fn, &rrbp);
+	if (rc < 0)
+		return NULL;
+
+	new_tbf = ms_ul_tbf(ms);
+	if (!new_tbf) {
+		LOGPTBF(ctx->tbf, LOGL_ERROR,
+			"We have a schedule for uplink assignment, but there is no uplink TBF\n");
+		tbf_ul_ass_fsm_state_chg(ctx->fi, TBF_UL_ASS_NONE);
+		return NULL;
+	}
+
+	msg = msgb_alloc(GSM_MACBLOCK_LEN, "rlcmac_ul_ass");
+	if (!msg)
+		return NULL;
+
+	/* Initialize a bit vector that uses allocated msgb as the data buffer. */
+	struct bitvec bv = {
+		.data = msgb_put(msg, GSM_MACBLOCK_LEN),
+		.data_len = GSM_MACBLOCK_LEN,
+	};
+	bitvec_unhex(&bv, DUMMY_VEC);
+
+	LOGPTBFUL((const struct gprs_rlcmac_tbf *)new_tbf, LOGL_INFO, "start Packet Uplink Assignment (PACCH)\n");
+	mac_control_block = (RlcMacDownlink_t *)talloc_zero(ctx->tbf, RlcMacDownlink_t);
+	tlli = ms_tlli(ms);
+	write_packet_uplink_assignment(mac_control_block, tbf_tfi(ctx->tbf),
+		(tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF), ms_tlli(ms),
+		 tlli != GSM_RESERVED_TMSI, new_tbf, 1, rrbp, bts_get_ms_pwr_alpha(ms->bts),
+		the_pcu->vty.gamma, -1, tbf_is_egprs_enabled(ctx->tbf));
+
+	LOGP(DTBF, LOGL_DEBUG, "+++++++++++++++++++++++++ TX : Packet Uplink Assignment +++++++++++++++++++++++++\n");
+	rc = encode_gsm_rlcmac_downlink(&bv, mac_control_block);
+	if (rc < 0) {
+		LOGP(DTBF, LOGL_ERROR, "Encoding of Packet Uplink Ass failed (%d)\n", rc);
+		goto free_ret;
+	}
+	LOGP(DTBF, LOGL_DEBUG, "------------------------- TX : Packet Uplink Assignment -------------------------\n");
+	bts_do_rate_ctr_inc(ms->bts, CTR_PKT_UL_ASSIGNMENT);
+
+	tbf_set_polling(ctx->tbf, new_poll_fn, d->ts, PDCH_ULC_POLL_UL_ASS);
+
+	talloc_free(mac_control_block);
+	return msg;
+
+free_ret:
+	talloc_free(mac_control_block);
+	msgb_free(msg);
+	return NULL;
+}
+
+static void st_none_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state)
+{
+	struct tbf_ul_ass_fsm_ctx *ctx = (struct tbf_ul_ass_fsm_ctx *)fi->priv;
+	unsigned long val;
+	unsigned int sec, micro;
+
+	/* Start release after rejecting only if it is UL TBF */
+	if (prev_state == TBF_UL_ASS_SEND_ASS_REJ &&
+	    tbf_direction(ctx->tbf) == GPRS_RLCMAC_UL_TBF) {
+		/* tbf_free() called upon trigger */
+		fi->T = -2000;
+		val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1);
+		sec = val / 1000;
+		micro = (val % 1000) * 1000;
+		LOGPTBF(ctx->tbf, LOGL_DEBUG, "starting timer X2000 [reject (PACCH)] with %u sec. %u microsec\n",
+			sec, micro);
+		osmo_timer_schedule(&fi->timer, sec, micro);
+	}
+
+}
+
+static void st_none(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	switch (event) {
+	case TBF_UL_ASS_EV_SCHED_ASS:
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_SEND_ASS);
+		break;
+	case TBF_UL_ASS_EV_SCHED_ASS_REJ:
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_SEND_ASS_REJ);
+		break;
+	default:
+		OSMO_ASSERT(0);
+	}
+}
+
+static void st_send_ass(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	struct tbf_ul_ass_fsm_ctx *ctx = (struct tbf_ul_ass_fsm_ctx *)fi->priv;
+	struct tbf_ul_ass_ev_create_rlcmac_msg_ctx *data_ctx;
+
+	switch (event) {
+	case TBF_UL_ASS_EV_CREATE_RLCMAC_MSG:
+		data_ctx = (struct tbf_ul_ass_ev_create_rlcmac_msg_ctx *)data;
+		data_ctx->msg = create_packet_ul_assign(ctx, data_ctx);
+		if (!data_ctx->msg)
+			return;
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_WAIT_ACK);
+		break;
+	default:
+		OSMO_ASSERT(0);
+	}
+}
+
+static void st_send_ass_rej(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	struct tbf_ul_ass_fsm_ctx *ctx = (struct tbf_ul_ass_fsm_ctx *)fi->priv;
+	struct tbf_ul_ass_ev_create_rlcmac_msg_ctx *data_ctx;
+
+	switch (event) {
+	case TBF_UL_ASS_EV_CREATE_RLCMAC_MSG:
+		data_ctx = (struct tbf_ul_ass_ev_create_rlcmac_msg_ctx *)data;
+		data_ctx->msg = create_packet_access_reject(ctx);
+		if (!data_ctx->msg)
+			return;
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_NONE);
+		break;
+	default:
+		OSMO_ASSERT(0);
+	}
+}
+
+static void st_wait_ack(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	switch (event) {
+	case TBF_UL_ASS_EV_RX_ASS_CTRL_ACK:
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_NONE);
+		break;
+	case TBF_UL_ASS_EV_ASS_POLL_TIMEOUT:
+		/* Reschedule Pkt Ul Ass */
+		tbf_ul_ass_fsm_state_chg(fi, TBF_UL_ASS_SEND_ASS);
+		break;
+	default:
+		OSMO_ASSERT(0);
+	}
+}
+
+static int tbf_ul_ass_fsm_timer_cb(struct osmo_fsm_inst *fi)
+{
+	struct tbf_ul_ass_fsm_ctx *ctx = (struct tbf_ul_ass_fsm_ctx *)fi->priv;
+	switch (fi->T) {
+	case -2000:
+		tbf_free(ctx->tbf);
+		break;
+	default:
+		OSMO_ASSERT(0);
+	}
+	return 0;
+}
+
+static struct osmo_fsm_state tbf_ul_ass_fsm_states[] = {
+	[TBF_UL_ASS_NONE] = {
+		.in_event_mask =
+			X(TBF_UL_ASS_EV_SCHED_ASS) |
+			X(TBF_UL_ASS_EV_SCHED_ASS_REJ),
+		.out_state_mask =
+			X(TBF_UL_ASS_SEND_ASS) |
+			X(TBF_UL_ASS_SEND_ASS_REJ),
+		.name = "NONE",
+		.action = st_none,
+		.onenter = st_none_on_enter,
+	},
+	[TBF_UL_ASS_SEND_ASS] = {
+		.in_event_mask = X(TBF_UL_ASS_EV_CREATE_RLCMAC_MSG),
+		.out_state_mask = X(TBF_UL_ASS_WAIT_ACK),
+		.name = "SEND_ASS",
+		.action = st_send_ass,
+	},
+	[TBF_UL_ASS_SEND_ASS_REJ] = {
+		.in_event_mask = X(TBF_UL_ASS_EV_CREATE_RLCMAC_MSG),
+		.out_state_mask = X(TBF_UL_ASS_NONE),
+		.name = "SEND_ASS_REJ",
+		.action = st_send_ass_rej,
+	},
+	[TBF_UL_ASS_WAIT_ACK] = {
+		.in_event_mask =
+			X(TBF_UL_ASS_EV_RX_ASS_CTRL_ACK) |
+			X(TBF_UL_ASS_EV_ASS_POLL_TIMEOUT),
+		.out_state_mask =
+			X(TBF_UL_ASS_NONE) |
+			X(TBF_UL_ASS_SEND_ASS),
+		.name = "WAIT_ACK",
+		.action = st_wait_ack,
+	},
+};
+
+struct osmo_fsm tbf_ul_ass_fsm = {
+	.name = "UL_ASS_TBF",
+	.states = tbf_ul_ass_fsm_states,
+	.num_states = ARRAY_SIZE(tbf_ul_ass_fsm_states),
+	.timer_cb = tbf_ul_ass_fsm_timer_cb,
+	.log_subsys = DTBF,
+	.event_names = tbf_ul_ass_fsm_event_names,
+};
+
+static __attribute__((constructor)) void tbf_ul_ass_fsm_init(void)
+{
+	OSMO_ASSERT(osmo_fsm_register(&tbf_ul_ass_fsm) == 0);
+}
+
+
+struct msgb *tbf_ul_ass_create_rlcmac_msg(const struct gprs_rlcmac_tbf* tbf, uint32_t fn, uint8_t ts)
+{
+	int rc;
+	struct tbf_ul_ass_ev_create_rlcmac_msg_ctx data_ctx = {
+		.fn = fn,
+		.ts = ts,
+		.msg = NULL,
+	};
+
+	rc = osmo_fsm_inst_dispatch(tbf_ul_ass_fi(tbf), TBF_UL_ASS_EV_CREATE_RLCMAC_MSG, &data_ctx);
+	if (rc != 0 || !data_ctx.msg)
+		return NULL;
+	return data_ctx.msg;
+}
+
+bool tbf_ul_ass_rts(const struct gprs_rlcmac_tbf* tbf)
+{
+	struct osmo_fsm_inst *fi = tbf_ul_ass_fi(tbf);
+	return fi->state == TBF_UL_ASS_SEND_ASS || fi->state == TBF_UL_ASS_SEND_ASS_REJ;
+}