diff --git a/pdu/submit.go b/pdu/submit.go
index 5834186..3f380ce 100644
--- a/pdu/submit.go
+++ b/pdu/submit.go
@@ -60,9 +60,9 @@ type (
 	SUBMIT_MULTI_RESP struct{}
 )
 
-func (p *SUBMIT_SM) Encode() ([]byte, error) {
-	buf := make([]byte, p.Size())
-	err := p.EncodeInto(&buf)
+func (p *SUBMIT_SM) Encode() (*[]byte, error) {
+	buf := ByteBufferPool.GetBuffer(uint(p.Size()))
+	err := p.EncodeInto(buf)
 	return buf, err
 }
 func (p *SUBMIT_SM) EncodeInto(buf *[]byte) error {