diff --git a/src/bts.cpp b/src/bts.cpp
index 6da8cdd..d14420c 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1147,3 +1147,32 @@
 	LOGP(DRLCMAC, LOGL_INFO, "PDCH(TS %d, TRX %d): Detaching %s, %d TBFs.\n",
 		ts_no, trx_no(), tbf->name(), m_num_tbfs[tbf->direction]);
 }
+
+void gprs_rlcmac_pdch::reserve(enum gprs_rlcmac_tbf_direction dir)
+{
+	m_num_reserved[dir] += 1;
+}
+
+void gprs_rlcmac_pdch::unreserve(enum gprs_rlcmac_tbf_direction dir)
+{
+	OSMO_ASSERT(m_num_reserved[dir] > 0);
+	m_num_reserved[dir] -= 1;
+}
+
+void gprs_rlcmac_trx::reserve_slots(enum gprs_rlcmac_tbf_direction dir,
+	uint8_t slots)
+{
+	unsigned i;
+	for (i = 0; i < ARRAY_SIZE(pdch); i += 1)
+		if (slots & (1 << i))
+			pdch[i].reserve(dir);
+}
+
+void gprs_rlcmac_trx::unreserve_slots(enum gprs_rlcmac_tbf_direction dir,
+	uint8_t slots)
+{
+	unsigned i;
+	for (i = 0; i < ARRAY_SIZE(pdch); i += 1)
+		if (slots & (1 << i))
+			pdch[i].unreserve(dir);
+}
diff --git a/src/bts.h b/src/bts.h
index f6cc88f..093a8e3 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -71,6 +71,10 @@
 	void detach_tbf(gprs_rlcmac_tbf *tbf);
 
 	unsigned num_tbfs(enum gprs_rlcmac_tbf_direction dir) const;
+
+	void reserve(enum gprs_rlcmac_tbf_direction dir);
+	void unreserve(enum gprs_rlcmac_tbf_direction dir);
+	unsigned num_reserved(enum gprs_rlcmac_tbf_direction dir) const;
 #endif
 
 	uint8_t m_is_enabled; /* TS is enabled */
@@ -100,6 +104,7 @@
 #endif
 
 	uint8_t m_num_tbfs[2];
+	uint8_t m_num_reserved[2];
 };
 
 struct gprs_rlcmac_trx {
@@ -112,6 +117,11 @@
 	/* back pointers */
 	struct BTS *bts;
 	uint8_t trx_no;
+
+#ifdef __cplusplus
+	void reserve_slots(enum gprs_rlcmac_tbf_direction dir, uint8_t slots);
+	void unreserve_slots(enum gprs_rlcmac_tbf_direction dir, uint8_t slots);
+#endif
 };
 
 /**
@@ -311,6 +321,12 @@
 	return m_num_tbfs[dir];
 }
 
+inline unsigned gprs_rlcmac_pdch::num_reserved(
+	enum gprs_rlcmac_tbf_direction dir) const
+{
+	return gprs_rlcmac_pdch::m_num_reserved[dir];
+}
+
 inline struct rate_ctr_group *BTS::rate_counters() const
 {
 	return m_ratectrs;
diff --git a/src/gprs_ms.cpp b/src/gprs_ms.cpp
index 4c0ecfd..f62facf 100644
--- a/src/gprs_ms.cpp
+++ b/src/gprs_ms.cpp
@@ -91,7 +91,10 @@
 	m_ref(0),
 	m_list(this),
 	m_delay(0),
-	m_nack_rate_dl(0)
+	m_nack_rate_dl(0),
+	m_reserved_dl_slots(0),
+	m_reserved_ul_slots(0),
+	m_current_trx(NULL)
 {
 	LOGP(DRLCMAC, LOGL_INFO, "Creating MS object, TLLI = 0x%08x\n", tlli);
 
@@ -115,6 +118,8 @@
 {
 	LOGP(DRLCMAC, LOGL_INFO, "Destroying MS object, TLLI = 0x%08x\n", tlli());
 
+	set_reserved_slots(NULL, 0, 0);
+
 	if (osmo_timer_pending(&m_timer))
 		osmo_timer_del(&m_timer);
 
@@ -240,8 +245,12 @@
 	if (tbf->ms() == this)
 		tbf->set_ms(NULL);
 
-	if (!m_dl_tbf && !m_ul_tbf && tlli() != 0)
-		start_timer();
+	if (!m_dl_tbf && !m_ul_tbf) {
+		set_reserved_slots(NULL, 0, 0);
+
+		if (tlli() != 0)
+			start_timer();
+	}
 
 	update_status();
 }
@@ -529,6 +538,28 @@
 	return -1;
 }
 
+void GprsMs::set_reserved_slots(gprs_rlcmac_trx *trx,
+	uint8_t ul_slots, uint8_t dl_slots)
+{
+	if (m_current_trx) {
+		m_current_trx->unreserve_slots(GPRS_RLCMAC_DL_TBF,
+			m_reserved_dl_slots);
+		m_current_trx->unreserve_slots(GPRS_RLCMAC_UL_TBF,
+			m_reserved_ul_slots);
+		m_reserved_dl_slots = 0;
+		m_reserved_ul_slots = 0;
+	}
+	m_current_trx = trx;
+	if (trx) {
+		m_reserved_dl_slots = dl_slots;
+		m_reserved_ul_slots = ul_slots;
+		m_current_trx->reserve_slots(GPRS_RLCMAC_DL_TBF,
+			m_reserved_dl_slots);
+		m_current_trx->reserve_slots(GPRS_RLCMAC_UL_TBF,
+			m_reserved_ul_slots);
+	}
+}
+
 gprs_rlcmac_tbf *GprsMs::tbf(enum gprs_rlcmac_tbf_direction dir) const
 {
 	switch (dir) {
diff --git a/src/gprs_ms.h b/src/gprs_ms.h
index 2c6061c..910ccb8 100644
--- a/src/gprs_ms.h
+++ b/src/gprs_ms.h
@@ -37,6 +37,7 @@
 #include <stddef.h>
 
 struct BTS;
+struct gprs_rlcmac_trx;
 
 class GprsMs {
 public:
@@ -79,6 +80,11 @@
 	uint8_t current_cs_dl() const;
 
 	int first_common_ts() const;
+	uint8_t reserved_dl_slots() const;
+	uint8_t reserved_ul_slots() const;
+	gprs_rlcmac_trx *current_trx() const;
+	void set_reserved_slots(gprs_rlcmac_trx *trx,
+		uint8_t ul_slots, uint8_t dl_slots);
 
 	gprs_llc_queue *llc_queue();
 	const gprs_llc_queue *llc_queue() const;
@@ -144,6 +150,9 @@
 
 	pcu_l1_meas m_l1_meas;
 	unsigned m_nack_rate_dl;
+	uint8_t m_reserved_dl_slots;
+	uint8_t m_reserved_ul_slots;
+	gprs_rlcmac_trx *m_current_trx;
 };
 
 inline uint32_t GprsMs::tlli() const
@@ -199,3 +208,17 @@
 	return m_nack_rate_dl;
 }
 
+inline uint8_t GprsMs::reserved_dl_slots() const
+{
+	return m_reserved_dl_slots;
+}
+
+inline uint8_t GprsMs::reserved_ul_slots() const
+{
+	return m_reserved_ul_slots;
+}
+
+inline gprs_rlcmac_trx *GprsMs::current_trx() const
+{
+	return m_current_trx;
+}