Tx-vector and Rx-vector

Medium Access Layer (MAC Layer) State-machines need to interact with the PHY Layer to meet certain Physical Medium dependent (PMD) restrictions. The Parameter list which defines the MAC-PHY interface is the Txvector and Rxvector parameters.

The Txvector and Rxvector Parameter list are defined in the PHY specific parameter list of each PHY sub-clause in the standard (e.g section 18.2 in the standard defines the OFDM phy service Parameter list)

A few examples of the Txvector parameter list for OFDM are shown below

FIG COURTESY: 802.11-2012TM

From the above table – explaining one Txvector – the Length field determines the maximum length of an individual MPDU in bytes that the MAC layer is requesting the PHY Layer to transmit. This field will determine the number of bytes that are transferred between the MAC layer and the PHY layer after the MAC Layer indicates a start of transmission to the PHY layer.

A few examples of the Rxvector parameters is provided below

FIG COURTESY: 802.11-2012TM

Explaining the Length field again – the length field indicates the number of bytes of the packet indicated in the received PLCP header. The MAC and PHY layers use this parameter to determine the number of bytes that are transferred between the PHY and the MAC layer on the receipt of a frame at the receiver.

For further reading – kindly refer the 802.11 standard for the specific PHY layer that you intend to look into.

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