2MAC Layer

2.1. Frame structure

2.1.1. Frame header

The MAC (Medium Access Control) header, described in Figure 2.1, encapsulates an LLC (Logical Link Control) frame whose size is less than or equal to 2,304 bytes.

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Figure 2.1. MAC header structure

Frame Control: this field consists of a sequence of several subfields:

  • – Protocol Version: this subfield is coded on two bits and takes the value 00;
  • – Type and Subtype: the subfields are coded, respectively, on two and four bits. They identify the function of the frame. There are three types of frames, namely the traffic frame, the control frame and the management frame. For each type of frame, subtypes are defined;
  • – To DS and From DS: these two subfields are coded on one bit. They indicate the direction of transmission of the frame (Table 2.1);
  • – More Fragments: this subfield is coded on a bit. It takes the value of ONE for traffic or management frames, if other fragments follow;
  • – Retry: this subfield is coded on a bit. It takes the value of ONE to signal the retransmission of a frame;
  • – Power Management: this subfield is coded on a bit. It takes the value of ONE when the station signals the switch to standby state;
  • – More Data: this subfield is coded on a bit. It takes the value of ONE when the access point signals to the terminal that frames are stored in the buffer;
  • – Protected Frame: this subfield is coded on a bit. It takes ...

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