Android : Appending bytes

i am developing an Android application and I am having some issues with adding bytes to compose a data packet. I have created a method to get the MAC Address of the client and the return value is a string (MACAdd).

private String getMACAddress() {
    WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    WifiInfo info = manager.getConnectionInfo();
    MACAdd= info.getMacAddress();
    return MACAdd;
}

I have declared MACAddrs as a static String and have done the following assignment in createPackect() method. MACAddrs = getMACAddress(); byte [] MACAddres = MACAddrs.getBytes();

In the same createPacket() method, I have declared following data as well.

    byte Node = (byte)0x3039;
    byte Cost = (byte)0x1;
    byte MaxMsgSize = (byte) 0x100000;
    byte KeepAlivePiriod = (byte)0x2710;
    byte NetworkID = (byte)0x1;

I need to add these bytes into a single array to compose the data packet.

byte[] BroadcastPacket = new byte[Node + Cost + SerialNumber + MaxMsgSize + KeepAlivePiriod + NetworkID + MACAddres + IPAddress];

as I am adding two different byte types, I am having a error. Please advise me how to solve this issue......