diff --git a/src/egprs_rlc_compression.cpp b/src/egprs_rlc_compression.cpp
index f4e6bde..82605ff 100644
--- a/src/egprs_rlc_compression.cpp
+++ b/src/egprs_rlc_compression.cpp
@@ -84,8 +84,203 @@
 	}
 }
 
-/* The code words for one run length and zero run length are described in
- * table 9.1.10.1 of 3gpp 44.060
+/*
+ * Terminating codes for uninterrupted sequences of 0 and 1 up to 64 bit length
+ * according to TS 44.060 9.1.10
+ */
+static const unsigned t4_term[2][64] = {
+	{
+		0b0000110111,
+		0b10,
+		0b11,
+		0b010,
+		0b011,
+		0b0011,
+		0b0010,
+		0b00011,
+		0b000101,
+		0b000100,
+		0b0000100,
+		0b0000101,
+		0b0000111,
+		0b00000100,
+		0b00000111,
+		0b000011000,
+		0b0000010111,
+		0b0000011000,
+		0b0000001000,
+		0b00001100111,
+		0b00001101000,
+		0b00001101100,
+		0b00000110111,
+		0b00000101000,
+		0b00000010111,
+		0b00000011000,
+		0b000011001010,
+		0b000011001011,
+		0b000011001100,
+		0b000011001101,
+		0b000001101000,
+		0b000001101001,
+		0b000001101010,
+		0b000001101011,
+		0b000011010010,
+		0b000011010011,
+		0b000011010100,
+		0b000011010101,
+		0b000011010110,
+		0b000011010111,
+		0b000001101100,
+		0b000001101101,
+		0b000011011010,
+		0b000011011011,
+		0b000001010100,
+		0b000001010101,
+		0b000001010110,
+		0b000001010111,
+		0b000001100100,
+		0b000001100101,
+		0b000001010010,
+		0b000001010011,
+		0b000000100100,
+		0b000000110111,
+		0b000000111000,
+		0b000000100111,
+		0b000000101000,
+		0b000001011000,
+		0b000001011001,
+		0b000000101011,
+		0b000000101100,
+		0b000001011010,
+		0b000001100110,
+		0b000001100111
+
+	},
+	{
+		0b00110101,
+		0b000111,
+		0b0111,
+		0b1000,
+		0b1011,
+		0b1100,
+		0b1110,
+		0b1111,
+		0b10011,
+		0b10100,
+		0b00111,
+		0b01000,
+		0b001000,
+		0b000011,
+		0b110100,
+		0b110101,
+		0b101010,
+		0b101011,
+		0b0100111,
+		0b0001100,
+		0b0001000,
+		0b0010111,
+		0b0000011,
+		0b0000100,
+		0b0101000,
+		0b0101011,
+		0b0010011,
+		0b0100100,
+		0b0011000,
+		0b00000010,
+		0b00000011,
+		0b00011010,
+		0b00011011,
+		0b00010010,
+		0b00010011,
+		0b00010100,
+		0b00010101,
+		0b00010110,
+		0b00010111,
+		0b00101000,
+		0b00101001,
+		0b00101010,
+		0b00101011,
+		0b00101100,
+		0b00101101,
+		0b00000100,
+		0b00000101,
+		0b00001010,
+		0b00001011,
+		0b01010010,
+		0b01010011,
+		0b01010100,
+		0b01010101,
+		0b00100100,
+		0b00100101,
+		0b01011000,
+		0b01011001,
+		0b01011010,
+		0b01011011,
+		0b01001010,
+		0b01001011,
+		0b00110010,
+		0b00110011,
+		0b00110100
+	}
+};
+static const unsigned t4_term_length[2][64] = {
+	{10, 2, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12},
+	{8, 6, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8}
+};
+
+static const unsigned t4_min_term_length[] = {2, 4};
+static const unsigned t4_min_make_up_length[] = {10, 5};
+
+static const unsigned t4_max_term_length[] = {12, 8};
+static const unsigned t4_max_make_up_length[] = {13, 9};
+
+static const unsigned t4_make_up_length[2][15] = {
+	{10, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13},
+	{5, 5, 6, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9}
+};
+
+static const unsigned t4_make_up_ind[15] = {64, 128, 192, 256, 320, 384, 448, 512, 576, 640, 704, 768, 832, 896, 960};
+
+static const unsigned t4_make_up[2][15] = {
+	{
+		0b0000001111,
+		0b000011001000,
+		0b000011001001,
+		0b000001011011,
+		0b000000110011,
+		0b000000110100,
+		0b000000110101,
+		0b0000001101100,
+		0b0000001101101,
+		0b0000001001010,
+		0b0000001001011,
+		0b0000001001100,
+		0b0000001001101,
+		0b0000001110010,
+		0b0000001110011
+	},
+	{
+		0b11011,
+		0b10010,
+		0b010111,
+		0b0110111,
+		0b00110110,
+		0b00110111,
+		0b01100100,
+		0b01100101,
+		0b01101000,
+		0b01100111,
+		0b011001100,
+		0b011001101,
+		0b011010010,
+		0b011010011,
+		0b011010100
+	 }
+};
+
+/* The code words for one run length and zero
+ * run length are described in table 9.1.10.1
+ * of 3gpp 44.060
  */
 const char *one_run_len_code_list[EGPRS_CODEWORDS] = {
 	"00110101",
@@ -359,3 +554,138 @@
 	decode_tree_init();
 }
 
+/* Compress received block bitmap
+ * \param run_len_cnt[in] Count of number of 1's and 0's
+ * \param codewrd_bitmap[in] Code word for coresponding run length.
+ * \param crbb_vec[out] compressed bitvector.
+ */
+static void compress_bitmap(
+		uint16_t *run_len_cnt,    /* cnt: run length count */
+		uint16_t *codewrd_bitmap, /* code word */
+		int16_t *codewrd_len, /* number of bits in the code word */
+		bitvec *crbb_vec,  /* bitmap buffer to put code word in */
+		bool start)
+{
+	int i = 0;
+	unsigned writeIndex = crbb_vec->cur_bit;
+	*codewrd_bitmap = 0;
+	*codewrd_len = 0;
+	if (*run_len_cnt >= 64) {
+		for (i = 0; i < 15; i++) {
+			if (t4_make_up_ind[i] == *run_len_cnt) {
+				*codewrd_bitmap = t4_make_up[start][i];
+				*codewrd_len = t4_make_up_length[start][i];
+			}
+		}
+	} else {
+		*codewrd_bitmap = t4_term[start][*run_len_cnt];
+		*codewrd_len = t4_term_length[start][*run_len_cnt];
+	}
+	bitvec_write_field(crbb_vec, writeIndex, *codewrd_bitmap, *codewrd_len);
+}
+
+/* Compress received block bitmap */
+int egprs_compress::osmo_t4_compress(struct bitvec *bv)
+{
+	uint8_t crbb_len = 0;
+	uint8_t uclen_crbb = 0;
+	uint8_t crbb_bitmap[127] = {'\0'};
+	bool start = (bv->data[0] & 0x80)>>7;
+	struct bitvec crbb_vec;
+
+	crbb_vec.data = crbb_bitmap;
+	crbb_vec.cur_bit = 0;
+	crbb_vec.data_len = 127;
+	bv->data_len = bv->cur_bit;
+	bv->cur_bit = 0;
+	if (egprs_compress::compress_rbb(bv, &crbb_vec, &uclen_crbb, 23*8)) {
+		memcpy(bv->data, crbb_bitmap, (crbb_len+7)/8);
+		bv->cur_bit = crbb_len;
+		bv->data_len = (crbb_len+7)/8;
+		return start;
+	}
+	else
+		printf("Encode failed\n");
+	return -1;
+}
+
+/*! \brief compression algorithm using T4 encoding
+ *  the compressed bitmap's are copied in crbb_bitmap
+ *  \param[in] rbb_vec bit vector to be encoded
+ *  \return 1 if compression is success or 0 for failure
+ */
+int egprs_compress::compress_rbb(
+		struct bitvec *urbb_vec,
+		struct bitvec *crbb_vec,
+		uint8_t *uclen_crbb,  /* Uncompressed bitmap len in CRBB */
+		uint8_t  max_bits)     /* max remaining bits */
+{
+	bool run_len_bit;
+	int buflen = urbb_vec->cur_bit;
+	int total_bits = urbb_vec->cur_bit;
+	uint16_t rlen;
+	uint16_t temprl = 0;
+	uint16_t cbmap = 0;     /* Compressed code word */
+	int16_t nbits;          /* Length of code word */
+	uint16_t uclen = 0;
+	int16_t clen = 0;
+	bool start;		/* Starting color code see 9.1.10, 3GPP 44.060 */
+	urbb_vec->cur_bit = 0;
+	run_len_bit = (urbb_vec->data[0] & 0x80)>>7;
+	while (buflen > 0) {
+		temprl = 0;
+		/* Find Run length */
+		if (run_len_bit == 1)
+			rlen = bitvec_rl_curbit(urbb_vec, true, total_bits);
+		else
+			rlen = bitvec_rl_curbit(urbb_vec, false, total_bits);
+		buflen = buflen - rlen;
+		/* if rlen > 64 need Makeup code word */
+		/*Compress the bits */
+		if (run_len_bit == 0) {
+			start = 0;
+			if (rlen >= 64) {
+				temprl = (rlen/64)*64;
+				compress_bitmap(&temprl, &cbmap, &nbits,
+						crbb_vec, start);
+				clen = clen + nbits;
+			}
+			temprl = MOD64(rlen);
+			compress_bitmap(&temprl, &cbmap, &nbits,
+						crbb_vec, start);
+			/* next time the run length will be Ones */
+			run_len_bit = 1;
+		} else {
+			start = 1;
+			if (rlen >= 64) {
+				temprl = (rlen/64)*64;
+				compress_bitmap(&temprl, &cbmap, &nbits,
+						crbb_vec, start);
+				clen = clen + nbits;
+			}
+			temprl = MOD64(rlen);
+			compress_bitmap(&temprl, &cbmap, &nbits,
+						crbb_vec, start);
+
+			/* next time the run length will be Zeros */
+			run_len_bit = 0;
+		}
+		uclen = uclen + rlen;
+		clen = clen + nbits;
+		/*compressed bitmap exceeds the buffer space */
+		if (clen > max_bits) {
+			uclen = uclen - rlen;
+			clen = clen - nbits;
+			break;
+		}
+	}
+	crbb_vec->cur_bit = clen;
+	*uclen_crbb = uclen;
+	if (clen >= uclen)
+		/* No Gain is observed, So no need to compress */
+		return 0;
+	else
+		LOGP(DRLCMACUL, LOGL_DEBUG, "CRBB bitmap = %s\n", osmo_hexdump(crbb_vec->data, (crbb_vec->cur_bit+7)/8));
+		/* Add compressed bitmap to final buffer */
+		return 1;
+}
diff --git a/src/egprs_rlc_compression.h b/src/egprs_rlc_compression.h
index c5f0f1a..4d2501b 100644
--- a/src/egprs_rlc_compression.h
+++ b/src/egprs_rlc_compression.h
@@ -5,6 +5,7 @@
 #pragma once
 
 struct egprs_compress_node;
+#define	 MOD64(X)	(((X) + 64) & 0x3F)
 
 /* Singleton to manage the EGPRS compression algorithm. */
 class egprs_compress
@@ -14,6 +15,9 @@
 		bool start, const uint8_t *orig_buf,
 		bitvec *dest);
 	egprs_compress();
+	int osmo_t4_compress(struct bitvec *bv);
+	static int compress_rbb(struct bitvec *urbb_vec, struct bitvec *crbb_vec,
+		uint8_t *uclen_crbb, uint8_t  max_bits);
 
 private:
 	egprs_compress_node *ones_list;
diff --git a/src/encoding.cpp b/src/encoding.cpp
index 8fa4bf6..ea38b77 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -24,6 +24,7 @@
 #include <bts.h>
 #include <tbf.h>
 #include <gprs_debug.h>
+#include <egprs_rlc_compression.h>
 
 extern "C" {
 #include <osmocom/gprs/protocol/gsm_04_60.h>
@@ -699,20 +700,44 @@
 
 static void write_packet_ack_nack_desc_egprs(
 	struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
-	gprs_rlc_ul_window *window, bool is_final)
+	gprs_rlc_ul_window *window, bool is_final, unsigned& rest_bits)
 {
-	int urbb_len = 0;
-	int len;
+	unsigned int urbb_len = 0;
+	uint8_t crbb_len = 0;
+	uint8_t len;
 	bool bow = true;
 	bool eow = true;
 	int ssn = window->mod_sns(window->v_q() + 1);
-	int num_blocks = window->mod_sns(window->v_r() - window->v_q());
+	unsigned int num_blocks = window->mod_sns(window->v_r() - window->v_q());
 	int esn_crbb = window->mod_sns(ssn - 1);
-	/* Bit 0 at the end is mandatory Table 11.2.28.1 in 44.060 */
-	int rest_bits = dest->data_len * 8 - wp - 1;
+	static  uint8_t rbb[RLC_EGPRS_MAX_WS] = {'\0'};
+	uint8_t iter = 0;
 	int is_compressed = 0;
+	bool try_compression = false;
+	uint8_t ucmp_bmplen;
+	uint8_t crbb_bitmap[23] = {'\0'};
+	bitvec ucmp_vec;
+	bitvec crbb_vec;
+	uint8_t uclen_crbb = 0;
 	bool len_coded = true;
+	uint8_t crbb_start_clr_code;
 	uint8_t i;
+#if 0
+	/* static size of 16 bits*/
+	 ..0. .... = ACKNACK:  (Union)
+        Desc
+
+            ...0 .... = FINAL_ACK_INDICATION: False
+
+            .... 1... = BEGINNING_OF_WINDOW: 1
+
+            .... .1.. = END_OF_WINDOW: 1
+
+            .... ..10  0101 0001  1... .... = STARTING_SEQUENCE_NUMBER: 1187
+
+            .0.. .... = CRBB Exist: 0
+#endif
+	rest_bits -= 16;
 
 	if (num_blocks > 0)
 		/* V(Q) is NACK and omitted -> SSN = V(Q) + 1 */
@@ -720,27 +745,67 @@
 
 	if (num_blocks > window->ws())
 		num_blocks = window->ws();
-	/* TODO Compression support */
-	if (is_compressed == 0) {
-		/* Union bit takes 1 bit */
-		/* Other fields in descr for uncompresed bitmap takes 15 bits*/
+	/* Try Compression  as number of blocks does not fit */
+	if (num_blocks > rest_bits) {
+		try_compression = true;
+	}
+	if (try_compression == true) {
+		ucmp_bmplen = window->update_egprs_rbb(rbb);
+		ucmp_vec.data = rbb;
+		ucmp_vec.cur_bit = ucmp_bmplen;
+		ucmp_vec.data_len = 127;
+		crbb_vec.data = crbb_bitmap;
+		crbb_vec.cur_bit = 0;
+		crbb_vec.data_len = 127;
+		LOGP(DRLCMACUL, LOGL_DEBUG,
+		"rest_bits=%d uncompressed len %d and uncompressed bitmap = %s\n",
+		 rest_bits, ucmp_bmplen,
+		osmo_hexdump(ucmp_vec.data, (ucmp_bmplen+7)/8));
 
-		if (num_blocks > rest_bits - 15 - 1) {
+		is_compressed = egprs_compress::compress_rbb(&ucmp_vec, /* Uncompressed bitmap*/
+			&crbb_vec, /*Compressed bitmap vector */
+			&uclen_crbb,
+			(rest_bits - 16));/* CRBBlength:7 colourcode:1 dissector length:8*/
+		LOGP(DRLCMACUL, LOGL_DEBUG,
+		"the ucmp len=%d uclen_crbb=%d num_blocks=%d crbb length %d, "
+		"and the CRBB bitmap  = %s\n",
+		ucmp_bmplen, uclen_crbb, num_blocks, crbb_vec.cur_bit,
+		osmo_hexdump(crbb_bitmap, (crbb_vec.cur_bit+7)/8));
+		crbb_len = crbb_vec.cur_bit;
+	}
+
+	if (is_compressed == 0) {
+		/* length field takes 8 bits*/
+		if (num_blocks > rest_bits - 8) {
 			eow = false;
-			urbb_len = rest_bits - 15 - 1;
+			urbb_len = rest_bits;
 			len_coded = false;
-		} else if (num_blocks == rest_bits - 15 - 1) {
-			urbb_len = rest_bits - 15 - 1;
+		} else if (num_blocks == rest_bits) {
+			urbb_len = rest_bits;
 			len_coded = false;
-		/* Union bit takes 1 bit length field takes 8 bits*/
-		} else if (num_blocks > rest_bits - 15 - 9) {
-			eow = false;
-			urbb_len = rest_bits - 15 - 9;
 		} else
 			urbb_len = num_blocks;
+
 		len = urbb_len + 15;
 	} else {
-		/* TODO Compressed bitmap */
+		if (num_blocks > uclen_crbb) {
+			eow = false;
+			urbb_len = num_blocks - uclen_crbb;
+		}
+		/* Union bit takes 1 bit */
+		/* Other fields in descr of compresed bitmap takes 23 bits
+		 * -8 = CRBB_STARTING_COLOR_CODE + CRBB_LENGTH */
+		if (urbb_len > (rest_bits - crbb_len - 8)) {
+			eow = false;
+			len_coded = false;
+			urbb_len = rest_bits - crbb_len - 8;
+		/* -16 =  ACKNACK Dissector length + CRBB_STARTING_COLOR_CODE + CRBB_LENGTH */
+		} else if (urbb_len > (rest_bits - crbb_len - 16)) {
+			eow = false;
+			len_coded = false;
+			urbb_len = rest_bits - crbb_len - 16;
+		}
+		len = urbb_len + crbb_len + 23;
 	}
 
 	/* EGPRS Ack/Nack Description IE */
@@ -756,14 +821,32 @@
 	bitvec_write_field(dest, wp, eow, 1); // END_OF_WINDOW
 	bitvec_write_field(dest, wp, ssn, 11); // STARTING_SEQUENCE_NUMBER
 	if (is_compressed) {
-		/* TODO Add CRBB support */
-	} else
+		bitvec_write_field(dest, wp, 1, 1); // CRBB_Exist
+		bitvec_write_field(dest, wp, crbb_len, 7); // CRBB_LENGTH
+		crbb_start_clr_code = (0x80 & ucmp_vec.data[0])>>7;
+		bitvec_write_field(dest, wp, crbb_start_clr_code, 1); // CRBB_clr_code
+		LOGP(DRLCMACUL, LOGL_DEBUG,
+			"EGPRS CRBB, crbb_len = %d, crbb_start_clr_code = %d\n",
+			crbb_len, crbb_start_clr_code);
+		while (crbb_len != 0) {
+			if (crbb_len > 8) {
+				bitvec_write_field(dest, wp, crbb_bitmap[iter], 8);
+				crbb_len = crbb_len - 8;
+				iter++;
+			} else {
+				bitvec_write_field(dest, wp, crbb_bitmap[iter], crbb_len);
+				crbb_len = 0;
+			}
+		}
+		esn_crbb = window->mod_sns(esn_crbb + uclen_crbb);
+	} else {
 		bitvec_write_field(dest, wp, 0, 1); // CRBB_Exist
+	}
 	LOGP(DRLCMACUL, LOGL_DEBUG,
 		"EGPRS URBB, urbb len = %d, SSN = %d, ESN_CRBB = %d, "
 		"len present = %s,desc len = %d, "
 		"SNS = %d, WS = %d, V(Q) = %d, V(R) = %d%s%s\n",
-		urbb_len, ssn, esn_crbb, len_coded ? "yes" : "No", len,
+		urbb_len, ssn, esn_crbb, len_coded ? "yes" : "No" , len,
 		window->sns(), window->ws(), window->v_q(), window->v_r(),
 		bow ? ", BOW" : "", eow ? ", EOW" : "");
 
@@ -795,7 +878,9 @@
 	bitvec_write_field(dest, wp, 0, 1); // 0: don't have Power Control Parameters
 	bitvec_write_field(dest, wp, 0, 1); // 0: don't have Extension Bits
 
-	write_packet_ack_nack_desc_egprs(bts, dest, wp, &tbf->m_window, is_final);
+	/* -2 for last bit 0 mandatory and REL5 not supported */
+	unsigned bits_ack_nack = dest->data_len * 8 - wp - 2;
+	write_packet_ack_nack_desc_egprs(bts, dest, wp, &tbf->m_window, is_final, bits_ack_nack);
 
 	bitvec_write_field(dest, wp, 0, 1); // fixed 0
 	bitvec_write_field(dest, wp, 0, 1); // 0: don't have REL 5
diff --git a/src/rlc.cpp b/src/rlc.cpp
index 2bffccb..d13045e 100644
--- a/src/rlc.cpp
+++ b/src/rlc.cpp
@@ -83,6 +83,32 @@
 	return resend;
 }
 
+/* Update the receive block bitmap */
+uint16_t gprs_rlc_ul_window::update_egprs_rbb(uint8_t *rbb)
+{
+	int i;
+	uint16_t bsn;
+	uint16_t bitmask = 0x80;
+	int8_t pos = 0;
+	int8_t bit_pos = 0;
+	for (i = 0, bsn = (v_q()+1); ((bsn < (v_r())) && (i < ws())); i++,
+					bsn = this->mod_sns(bsn + 1)) {
+		if (m_v_n.is_received(bsn)) {
+			rbb[pos] = rbb[pos] | bitmask;
+		} else {
+			rbb[pos] = rbb[pos] & (~bitmask);
+		}
+		bitmask = bitmask >> 1;
+		bit_pos++;
+		bit_pos = bit_pos % 8;
+		if (bit_pos == 0) {
+			pos++;
+			bitmask = 0x80;
+		}
+	}
+	return i;
+}
+
 int gprs_rlc_dl_window::count_unacked()
 {
 	uint16_t unacked = 0;
@@ -219,6 +245,8 @@
 
 void gprs_rlc_window::set_ws(uint16_t ws)
 {
+	LOGP(DRLCMAC, LOGL_INFO, "ws(%d)\n",
+		ws);
 	OSMO_ASSERT(ws >= RLC_GPRS_SNS/2);
 	OSMO_ASSERT(ws <= RLC_MAX_SNS/2);
 	m_ws = ws;
diff --git a/src/rlc.h b/src/rlc.h
index b2fcd95..7db205d 100644
--- a/src/rlc.h
+++ b/src/rlc.h
@@ -347,6 +347,7 @@
 	bool is_received(uint16_t bsn) const;
 
 	void update_rbb(char *rbb);
+	uint16_t update_egprs_rbb(uint8_t *rbb);
 	void raise_v_r_to(int moves);
 	void raise_v_r(const uint16_t bsn);
 	uint16_t raise_v_q();
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 657255d..33d94a8 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -827,14 +827,16 @@
 	if (egprs_ms_class > 0 && bts->egprs_enabled) {
 		tbf->enable_egprs();
 		tbf->m_window.set_sns(RLC_EGPRS_SNS);
-		/* TODO: Allow bigger UL windows when CRBB encoding is supported */
-		tbf->m_window.set_ws(RLC_EGPRS_MIN_WS);
 		setup_egprs_mode(bts, ms);
 		LOGP(DRLCMAC, LOGL_INFO, "Enabled EGPRS for %s, mode %s\n",
 			tbf->name(), GprsCodingScheme::modeName(ms->mode()));
 	}
 
 	rc = setup_tbf(tbf, ms, use_trx, ms_class, egprs_ms_class, single_slot);
+
+	if (tbf->is_egprs_enabled())
+		tbf->egprs_calc_ulwindow_size();
+
 	/* if no resource */
 	if (rc < 0) {
 		talloc_free(tbf);
diff --git a/src/tbf.h b/src/tbf.h
index adb7dcc..0389595 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -523,6 +523,8 @@
 		struct gprs_rlc_data *block,
 		uint8_t *data, const uint8_t block_idx);
 
+	void egprs_calc_ulwindow_size();
+
 	void update_coding_scheme_counter_ul(const GprsCodingScheme cs);
 
 	/* Please note that all variables here will be reset when changing
diff --git a/src/tbf_ul.cpp b/src/tbf_ul.cpp
index 0de0127..2598174 100644
--- a/src/tbf_ul.cpp
+++ b/src/tbf_ul.cpp
@@ -29,6 +29,8 @@
 #include <decoding.h>
 #include <pcu_l1_if.h>
 
+#include "pcu_utils.h"
+
 extern "C" {
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/talloc.h>
@@ -587,3 +589,22 @@
 		}
 	}
 }
+
+void gprs_rlcmac_ul_tbf::egprs_calc_ulwindow_size()
+{
+	struct gprs_rlcmac_bts *bts_data = bts->bts_data();
+	unsigned int num_pdch = pcu_bitcount(ul_slots());
+	unsigned int ws = bts_data->ws_base + num_pdch * bts_data->ws_pdch;
+	ws = (ws / 32) * 32;
+	ws = OSMO_MAX(64, ws);
+
+	if (num_pdch == 1)
+		ws = OSMO_MIN(192, ws);
+	else
+		ws = OSMO_MIN(128 * num_pdch, ws);
+
+	LOGP(DRLCMAC, LOGL_INFO, "%s: Setting EGPRS window size to %d, base(%d) slots(%d) ws_pdch(%d)\n",
+		name(), ws, bts_data->ws_base, num_pdch, bts_data->ws_pdch);
+
+	m_window.set_ws(ws);
+}