diff --git a/example/transceiver_with_auto_response/main.go b/example/transceiver_with_auto_response/main.go
index 37b9532..3392eb2 100644
--- a/example/transceiver_with_auto_response/main.go
+++ b/example/transceiver_with_auto_response/main.go
@@ -73,7 +73,7 @@ func sendingAndReceiveSMS(wg *sync.WaitGroup) {
 }
 
 func handlePDU() func(pdu.PDU, bool) {
-	concatenated := map[uint8][]string{}
+	concatenated := map[uint16][]string{}
 	return func(p pdu.PDU, _ bool) {
 		switch pd := p.(type) {
 		case *pdu.SubmitSMResp:
diff --git a/pdu/UDH.go b/pdu/UDH.go
index de01743..68af3ed 100644
--- a/pdu/UDH.go
+++ b/pdu/UDH.go
@@ -7,7 +7,8 @@ import (
 	"github.com/linxGnu/gosmpp/data"
 )
 
-// For now, this package only support message uses of UDH for message concatenation
+// This package supports message uses of UDH for message concatenation
+// Both 8-bit and 16-bit reference numbers are supported for concatenated messages
 // No plan for supporting other Enhanced Messaging Service
 // Credit to https://github.com/warthog618/sms
 
@@ -149,17 +150,29 @@ func (u UDH) FindInfoElement(id byte) (ie *InfoElement, found bool) {
 }
 
 // GetConcatInfo return the FIRST concatenated message IE,
-func (u UDH) GetConcatInfo() (totalParts, partNum, mref byte, found bool) {
+// For 8-bit reference, mref will be a byte value (0-255)
+// For 16-bit reference, mref will be a uint16 value (0-65535) converted to uint
+func (u UDH) GetConcatInfo() (totalParts, partNum byte, mref uint16, found bool) {
 	if len(u) == 0 {
 		found = false
 		return
 	}
 
+	// Check for 8-bit reference
 	if ie, ok := u.FindInfoElement(data.UDH_CONCAT_MSG_8_BIT_REF); ok && len(ie.Data) == 3 {
-		mref = ie.Data[0]
+		mref = uint16(ie.Data[0])
 		totalParts = ie.Data[1]
 		partNum = ie.Data[2]
 		found = ok
+		return
+	}
+
+	// Check for 16-bit reference
+	if ie, ok := u.FindInfoElement(data.UDH_CONCAT_MSG_16_BIT_REF); ok && len(ie.Data) == 4 {
+		mref = uint16(ie.Data[0])<<8 | uint16(ie.Data[1])
+		totalParts = ie.Data[2]
+		partNum = ie.Data[3]
+		found = ok
 	}
 
 	return
@@ -173,7 +186,7 @@ type InfoElement struct {
 	Data []byte
 }
 
-// NewIEConcatMessage  turn a new IE element for concat message info
+// NewIEConcatMessage creates a new IE element for 8-bit concat message info
 // IE.Data is populated at time of object creation
 func NewIEConcatMessage(totalParts, partNum, mref byte) InfoElement {
 	return InfoElement{
@@ -182,6 +195,16 @@ func NewIEConcatMessage(totalParts, partNum, mref byte) InfoElement {
 	}
 }
 
+// NewIEConcatMessage16Bit creates a new IE element for 16-bit concat message info
+// IE.Data is populated at time of object creation
+// mref is a uint16 value (0-65535)
+func NewIEConcatMessage16Bit(totalParts, partNum byte, mref uint16) InfoElement {
+	return InfoElement{
+		ID:   data.UDH_CONCAT_MSG_16_BIT_REF,
+		Data: []byte{byte(mref >> 8), byte(mref), byte(totalParts), byte(partNum)},
+	}
+}
+
 // UnmarshalBinary unmarshal IE from binary in src, only read a single IE,
 // expect src at least of length 2 with correct IE format:
 //
diff --git a/pdu/UDH_test.go b/pdu/UDH_test.go
index 66ac447..7782fab 100644
--- a/pdu/UDH_test.go
+++ b/pdu/UDH_test.go
@@ -24,10 +24,23 @@ func TestUserDataHeader(t *testing.T) {
 		require.True(t, found)
 		require.Equal(t, totalParts, byte(2))
 		require.Equal(t, sequence, byte(1))
-		require.Equal(t, reference, uint8(12))
+		require.Equal(t, reference, uint(12))
 	})
 
-	t.Run("unmarshalBinaryUDHConcatMessage", func(t *testing.T) {
+	t.Run("marshalBinaryUDHConcatMessage (16 bit)", func(t *testing.T) {
+		u := UDH{NewIEConcatMessage16Bit(2, 1, 1234)}
+		b, err := u.MarshalBinary()
+		require.NoError(t, err)
+		require.Equal(t, "06080404d20201", toHex(b))
+
+		totalParts, sequence, reference, found := u.GetConcatInfo()
+		require.True(t, found)
+		require.Equal(t, totalParts, byte(2))
+		require.Equal(t, sequence, byte(1))
+		require.Equal(t, reference, uint(1234))
+	})
+
+	t.Run("unmarshalBinaryUDHConcatMessage (8 bit)", func(t *testing.T) {
 		u, rd := new(UDH), []byte{0x05, 0x00, 0x03, 0x0c, 0x02, 0x01}
 		read, err := u.UnmarshalBinary(rd)
 		require.False(t, read <= 0)
@@ -39,10 +52,29 @@ func TestUserDataHeader(t *testing.T) {
 		require.Equal(t, "0500030c0201", toHex(b))
 	})
 
+	t.Run("unmarshalBinaryUDHConcatMessage (16 bit)", func(t *testing.T) {
+		u, rd := new(UDH), []byte{0x06, 0x08, 0x04, 0x04, 0xd2, 0x02, 0x01}
+		read, err := u.UnmarshalBinary(rd)
+		require.False(t, read <= 0)
+
+		require.NoError(t, err)
+
+		totalParts, sequence, reference, found := u.GetConcatInfo()
+		require.True(t, found)
+		require.Equal(t, totalParts, byte(2))
+		require.Equal(t, sequence, byte(1))
+		require.Equal(t, reference, uint(1234))
+
+		b, err := u.MarshalBinary()
+		require.NoError(t, err)
+		require.Equal(t, "06080404d20201", toHex(b))
+	})
+
 	t.Run("unmarshalBinaryUDHConcatMessage failed", func(t *testing.T) {
 		failedList := [][]byte{
-			{0x04, 0x00, 0x02, 0x02, 0x01},
-			{0x04, 0x08, 0x02, 0x02, 0x01},
+			{0x04, 0x00, 0x02, 0x02, 0x01},       // Invalid 8-bit UDH (wrong length)
+			{0x04, 0x08, 0x02, 0x02, 0x01},       // Invalid 16-bit UDH (wrong length)
+			{0x05, 0x08, 0x03, 0x04, 0xd2, 0x01}, // Invalid 16-bit UDH (missing part number)
 		}
 		u := new(UDH)
 		for _, data := range failedList {