Raw IEEE 802.11 packet transmission
The nRF70 Series device supports the transmission of raw IEEE 802.11 packets. Raw IEEE 802.11 packets are packets that are not modified by the 802.11 Medium Access Control (MAC) layer during transmission by the nRF70 Series device.
It is the responsibility of the application that intends to send the raw 802.11 packet to construct and provide a fully-conformant 802.11 packet along with the required set of packet TX and PHY parameters. The MAC layer on the nRF70 Series device will transmit the raw 802.11 packets over-the-air using the provided packet data, TX, and PHY parameters.
Enabling raw packet transmit feature
To use the raw packet transmit feature in your applications, you must enable the CONFIG_NRF70_RAW_DATA_TX Kconfig option in the project configuration.
TX injection mode
The nRF70 Series device supports raw 802.11 packet transmission when TX injection mode is enabled in the nRF Wi-Fi driver.
The TX injection mode can be enabled when the primary mode of operation for the nRF70 Series device is set to either Station mode or Monitor mode. When the nRF70 Series device is configured in Station mode, TX injection mode can be enabled regardless of whether the device is connected to an Access Point (AP) or not.
Use the net_eth_txinjection_mode functional API to enable or disable TX injection mode in the nRF Wi-Fi driver as required by the application.
You can also use the NET_REQUEST_ETHERNET_SET_TXINJECTION_MODE network management API to enable or disable TX injection mode, however it is recommended to use the functional API (net_eth_txinjection_mode).
The network management API NET_REQUEST_ETHERNET_GET_TXINJECTION_MODE can be used to obtain the current TX injection configured setting in the nRF Wi-Fi driver.
When TX injection mode is enabled, you need to configure the operating channel. This channel will be used as the transmit channel when the nRF70 Series device operates in Station mode, but is not connected to an AP. When the nRF70 Series device operates in Station mode and is connected to an AP on a given channel, the connected channel will be used for raw 802.11 packet transmission. When the nRF70 Series device operates in Monitor mode, the configured channel for Monitor mode will be used as the transmit channel for TX injection operation.
To set the desired channel for raw 802.11 packet transmission, you can use the NET_REQUEST_WIFI_CHANNEL network management API.
See the Wi-Fi: Shell sample for more information on configuring mode and channel settings for raw packet transmission through shell commands.
The following table lists the shell commands and network management APIs used to switch the primary modes of operation needed for raw packet transmission.
Network management APIs |
Wi-Fi shell command |
Example usage |
Description |
|---|---|---|---|
net_mgmt(NET_REQUEST_WIFI_MODE) |
|
|
Configure interface instance 1 to Monitor mode |
net_mgmt(NET_REQUEST_WIFI_MODE) |
|
|
Configure interface instance 1 to Station mode |
The following table provides the parameter details for the net_eth_txinjection_mode API, which is used to enable or disable TX injection mode for raw packet transmission.
API parameter |
description |
|---|---|
iface |
Network interface on which TX injection mode is to be enabled |
enable |
Boolean value to enable or disable TX injection mode |
The following table provides the network management API used to set the channel of operation for raw packet transmission.
Network management APIs |
Wi-Fi shell command |
Example usage |
Description |
|---|---|---|---|
net_mgmt(NET_REQUEST_WIFI_CHANNEL) |
|
|
Set the raw transmission channel to |
TX injection mode usage requirements
The raw packet to be transmitted by an application must be a fully conformant IEEE 802.11 packet and must ensure that:
The packet has a valid 802.11 MAC header.
The Frame Check Sequence (FCS) is not added to the packet by the application and is concatenated by the nRF70 Series device.
Note
If the packet is not a properly framed 802.11 packet, it will be dropped by the nRF70 Series device and will not be transmitted over-the-air.
Additionally, the raw packet must provide transmit parameters that inform the nRF Wi-Fi driver on how the packet must be transmitted. It must also provide a packet marker identifying itself as a special packet, which must be handled differently by the nRF Wi-Fi driver. The transmit parameters and the packet marker together form the raw packet transmit header. The raw packet transmit header is prepended to the 802.11 conformant raw packet before the packet is passed to the nRF Wi-Fi driver by the application.
The following table lists the raw packet transmit header elements:
Transmit and PHY parameters |
Description |
|---|---|
magic_num |
Magic number to identify a raw packet. It is set to |
data_rate |
Data rate at which a packet is to be transmitted. It depends on the |
packet_length |
Packet length of the 802.11 raw packet, excluding the raw transmit packet header length. |
tx_mode |
Mode describing if the packet is VHT, HT, HE, or Legacy. |
queue |
Wi-Fi access category mapping for packet. |
raw_tx_flag |
Flag indicating raw packet transmission. This is reserved for driver use. |
You can refer to the relevant structures at:
nrfxlib/nrf_wifi/fw_if/umac_if/inc/default/fmac_structs.h/raw_tx_pkt_header - for the raw packet header.
nrfxlib/nrf_wifi/fw_if/umac_if/inc/default/fmac_structs.h/nrf_wifi_fmac_ac - for setting the queue parameter in the raw packet transmit header.
nrfxlib/nrf_wifi/fw_if/umac_if/inc/default/fmac_structs.h/nrf_wifi_fmac_rawtx_mode - for setting the tx_mode parameter in the raw packet transmit header.
Raw 802.11 packet transmit operation
The raw packet data has to be encompassed in an 802.11 packet and prepended with the raw transmit header before it is transmitted through raw socket to the nRF Wi-Fi driver for transmission. The packet is forwarded to the nRF70 Series device, which transmits the packet over-the-air. All 802.11 MAC layer rules for the 802.11 packet (such as, link-layer acknowledgements, retransmissions) are handled by the nRF70 Series device.
The following figure illustrates the packet structure and raw packet operation flow:
Raw packet transmit packet structure and raw packet operation flow
Operating channel for raw packet transmission
The channel configuration for raw packet transmission will be applied as follows:
Non-connected Station with TX injection mode configured and channel not set: The raw packet is transmitted on channel 1.
Non-connected Station with TX injection mode configured and channel set by the user: The raw packet is transmitted on configured channel.
Connected Station with TX injection mode configured: The raw packet is transmitted on the channel on which the device is connected to the AP.
Station disconnected from the AP and TX injection mode configured (channel configured before connection to the AP): The raw packet is transmitted on the configured channel
Station disconnected from the AP and TX injection mode configured (channel not configured before connection to the AP): The raw packet is transmitted on channel 1 (fallback channel).
Note
You must explicitly configure the channel for raw packet transmission when the device operates in non-connected Station mode. The device will use a fallback channel for raw packet transmission if one is not configured.
Error handling for raw packet transmission
The raw packet transmission errors can be obtained by invoking the NET_REQUEST_STATS_GET_WIFI network management API.
After invoking the API, you can use the struct net_stats_wifi struct in the zephyr/include/zephyr/net/net_stats.h header file.
The error member in struct net_stats_wifi will provide the transmit errors for all packets including raw packet transmit failure.