diff --git a/src/linklayer/lte/mac/HARQEntity.h b/src/linklayer/lte/mac/HARQEntity.h
index 10950da3ae2c644d27d4d29c38edae80123d7598..41f933e12567cbfa3f81d765246bc6b01ed57d8c 100644
--- a/src/linklayer/lte/mac/HARQEntity.h
+++ b/src/linklayer/lte/mac/HARQEntity.h
@@ -20,7 +20,7 @@
 
 class HARQEntity {
 private:
-    std::vector<HARQProcess*> procs;
+    std::map<unsigned, HARQProcess*> procs;
 public:
     HARQEntity();
     virtual ~HARQEntity();
diff --git a/src/linklayer/lte/mac/MAC.cc b/src/linklayer/lte/mac/MAC.cc
index c86172fbf428a10db66c2ce8d5191c44320e8e44..90eda0e3be3432f5554db5a999fbeaecf70295b7 100644
--- a/src/linklayer/lte/mac/MAC.cc
+++ b/src/linklayer/lte/mac/MAC.cc
@@ -24,7 +24,8 @@
 Define_Module(MAC);
 
 MAC::MAC() {
-    // TODO Auto-generated constructor stub
+    // TODO Auto-generated constructor stub
+    ttiId = 0;
 }
 
 MAC::~MAC() {
@@ -40,14 +41,22 @@ void MAC::initialize(int stage) {
             rnti = uniform(RA_RNTI_MIN_VALUE, RA_RNTI_MAX_VALUE);
             sendDown(new cPacket("RandomAccessRequest"), PRACH, RandomAccessRequest, RaRnti, rnti, 1);
         }
+
+        ttiTimer = new cMessage("TTI-TIMER");
+        this->scheduleAt(simTime() + TTI_TIMER_TIMEOUT, ttiTimer);
+        ttiTimer->setContextPointer(this);
     }
 }
 
 void MAC::handleMessage(cMessage *msg) {
-    if (msg->arrivedOn("lowerLayerIn")) {
-        handleLowerMessage(msg);
+    if (msg->isSelfMessage()) {
+
     } else {
-        handleUpperMessage(msg);
+        if (msg->arrivedOn("lowerLayerIn")) {
+            handleLowerMessage(msg);
+        } else {
+            handleUpperMessage(msg);
+        }
     }
 }
 
diff --git a/src/linklayer/lte/mac/MAC.h b/src/linklayer/lte/mac/MAC.h
index f8ff3de920b172e0ab669e495fd7c4aa8a75becc..afe4b846271fe75ea0182a2deaecfb72427d4b1e 100644
--- a/src/linklayer/lte/mac/MAC.h
+++ b/src/linklayer/lte/mac/MAC.h
@@ -25,6 +25,7 @@
 #define RA_RNTI_MAX_VALUE   60
 #define C_RNTI_MIN_VALUE    1
 #define C_RNTI_MAX_VALUE    65523
+#define TTI_TIMER_TIMEOUT   1
 
 class MAC : public cSimpleModule, public INotifiable {
 protected:
@@ -33,6 +34,9 @@ protected:
     NotificationBoard *nb;
 
     virtual void receiveChangeNotification(int category, const cPolymorphic *details) {}
+
+    cMessage *ttiTimer;
+    unsigned ttiId;
 public:
     MAC();
     virtual ~MAC();