The more bits per transmission the more data that can be sent. Think of coding as how many bits can be packed into a transmission. This layer uses very complex coding techniques (DBPSK, DQPSK, BPSK, QPSK, CCK, QAM, ( WHAT IS QAM?)). PMD - The PMD layer is where data is converted into bits 0's and 1's. The PHY rate at which the (MPDU/PSDU) will be transmitted is determined at this layer. The preamble is used to synchronize radios that a pending frame is on its way. A preamble is a series of 0's and 1's modulated on the channel before a pending frame. PLCP - The PLCP role is to add the preamble and PHY header. LAYER 1 - Layer 1 has 2 sub layers (PLCP) Physical Layer Convergence Procedure and (PMD) Physical Medium Dependent. Lets look closely at those layers and detail what happens at each layer. Although we are expected and should know all layers! As you know, when wireless doesn't work, its a wireless problem regardless if it's routing or something else! The 802.11 protocol operates in two very specific layers of the OSI model LAYER 1 and LAYER 2. LAYER 4 - The transport layer is where TCP or UDP information is added.Ī wireless engineer lives in layers 1 - 2. This is also where your IP header is added. LAYER 3 - The network layer is where upper layer information (Layers 4 -7) is encapsulated into a IP packet. To be clear, at this layer your data is referenced as a frame and not an IP packet. This is also where the MAC address information is added. LAYER 2 - The data layer is where upper layer information (Layers 3-7) is encapsulated into a frame. This is also the layer where data gets transmitted / received into bits, 0's and 1's using complex coding and modulations. LAYER 1 - The physical layer in the wired world consist of connectors, cables, fiber, and gbics. Lets look at a few 802.3 (wired) examples. Understanding each layer is very important when troubleshooting and designing. Although today we are finding ourselves supporting all layers including layer 8 (People)!Įach layer has a role to play in passing data communication up and down the OSI stack. It was also a foreign language to some as they overheard us talking and using comments like, "It must be a layer 3 issue" or "Did you check Layer 2 because layer 1 looks good".Ī wired engineer lives in layers 1 - 4, typically. It gave a foundation to a rather complex communication. As I developed my craft the OSI model was very important. Remembering the layers took on a variety of memorizing techniques. Many years ago reading my first networking book, the first chapter was about the OSI model.
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