Frame Structure - DSSS and Optional PBCC

In 802.11 DSSS systems, information is transmitted in frames. The total frame length is variable. The N7617C Signal Studio for WLAN 2023 Update 1.0 software supports framing for both the long and short preambles, as detailed in the following figures. 

PPDU Frame with Long PLCP Preamble

Figure 1. PPDU frame with long PLCP preamble

PLCP Preamble

PLCP Header

PPDU Frame with Short PLCP Preamble

Figure 2. PPDU frame with short PLCP preamble

Payload Structure

The payload field is contained within the PPDU frame. A MAC header and FCS can be added to the data payload. The following table provides a summary of the payload characteristics for the 802.11b DSSS mode.

Table 1. DSSS mode summary  

Data Rate

Mbps

Chip Rate

Mcps

Spreading/Coding Scheme

Modulation

1

11

11 Chip Barker Code

DBPSK

2

11

11 Chip Barker Code

DQPSK

5.5

11

CCK

DQPSK

11

11

CCK

DQPSK

5.5

11

PBCC

BPSK

11

11

PBCC

QPSK

The following figure is an illustration of the MAC header structure. The description and details of each of these fields can be found in the IEEE 802.11 standard. The user has control over all of these fields.

Figure 3. MAC header structure