Relate CSI information between devices (AEGHB-655)

[Wuhao Liu]

Now I am trying to do key generation from CSI data. I am collecting CSI data by sending probe packets. A sender sends a probe packet with an identifier and the receiver responds with the same identifier. In this case, both should have a matching CSI record. The problem is that the CSI data might get lost. Sometimes the sender gets more CSI data than the receiver or vice versa.

How can I match the CSI data from each side? One simple way would be to also store the identifier, but it seems packet data is not accessible in CSI received callback function.

[MacChu0315-Espressif]

The functionality you mentioned is already achievable. On the master IDF, under components/esp_wifi/include/local/esp_wifi_types_native.h, the wifi_csi_info_t already offers a more comprehensive set of data. You can adapt this on your own to implement the desired features.

[Wuhao Liu]

Thanks for your answer.
In this wifi_csi_info_t structure, I can get the source MAC address and the destination MAC address, so I can match who is the sender and who is the recipient. This is good. However, I cannot know which packet this CSI is associated with.

typedef struct {
    wifi_pkt_rx_ctrl_t rx_ctrl;/**< received packet radio metadata header of the CSI data */
    uint8_t mac[6];            /**< source MAC address of the CSI data */
    uint8_t dmac[6];           /**< destination MAC address of the CSI data */
    bool first_word_invalid;   /**< first four bytes of the CSI data is invalid or not */
    int8_t *buf;               /**< buffer of CSI data */
    uint16_t len;              /**< length of CSI data */
} wifi_csi_info_t;

I want to know the corresponding packet data. For example, provide a data parameter in csi callback function. Namely from typedef void (* wifi_csi_cb_t)(void *ctx, wifi_csi_info_t *data); to typedef void (* wifi_csi_cb_t)(void *ctx, wifi_csi_info_t *data, const uint8_t *packet_data);.

[MacChu0315-Espressif]

There may have been some misunderstandings in the communication. What I meant to convey is that the wifi_csi_info_t structure on the master branch of IDF already provides more information, as shown below:

typedef struct wifi_csi_info_t {
    wifi_pkt_rx_ctrl_t rx_ctrl; /**< received packet radio metadata header of the CSI data */
    uint8_t mac[6];             /**< source MAC address of the CSI data */
    uint8_t dmac[6];            /**< destination MAC address of the CSI data */
    bool first_word_invalid;    /**< first four bytes of the CSI data are invalid or not; true indicates the first four bytes are invalid due to hardware limitations */
    int8_t *buf;                /**< valid buffer of CSI data */
    uint16_t len;               /**< valid length of CSI data */
    uint8_t *hdr;               /**< header of the wifi packet */
    uint8_t *payload;           /**< payload of the wifi packet */
    uint16_t payload_len;       /**< payload length of the wifi packet */
    uint16_t rx_seq;            /**< rx sequence number of the wifi packet */
} wifi_csi_info_t;

After adapting this to our project, it allows you to match the transmitter and receiver using the payload of the wireless packet.

[Wuhao Liu]

Problem solved. Thank you.