We throw a lot of terms around when we discuss LTE data transmissions, especially when we get into some of the details of sending data over the PDSCH using multiple antenna techniques. We describe transport blocks as holding the data we’re trying to send, but how do they relate to codewords? Assigning bits to different layers can be used to improve reliability or throughput, but are layers the same as antenna ports? Let’s have a closer look at what’s going on down in the Physical (PHY) Layer.
User data and signaling messages are processed by the PDCP, RLC and MAC layers before being passed down to the PHY layer to be sent over the air. A lot happens to a data packet before PHY gets it, but for the moment, let’s just treat the MAC PDU (Protocol Data Unit) that PHY receives from MAC as “data”. To PHY, it’s just a string of bits anyway. This will be our transport block. Read more