}
+static int wpas_channel_width_offset(enum chan_width cw)
+{
+ switch (cw) {
+ case CHAN_WIDTH_40:
+ return 1;
+ case CHAN_WIDTH_80:
+ return 2;
+ case CHAN_WIDTH_80P80:
+ case CHAN_WIDTH_160:
+ return 3;
+ case CHAN_WIDTH_320:
+ return 4;
+ default:
+ return 0;
+ }
+}
+
+
+/**
+ * wpas_channel_width_tx_pwr - Calculate the max transmit power at the channel
+ * width
+ * @ies: Information elements
+ * @ies_len: Length of elements
+ * @cw: The channel width
+ * Returns: The max transmit power at the channel width, TX_POWER_NO_CONSTRAINT
+ * if it is not constrained.
+ *
+ * This function is only used to estimate the actual signal RSSI when associated
+ * based on the beacon RSSI at the STA. Beacon frames are transmitted on 20 MHz
+ * channels, while the Data frames usually use higher channel width. Therefore
+ * their RSSIs may be different. Assuming there is a fixed gap between the TX
+ * power limit of the STA defined by the Transmit Power Envelope element and the
+ * TX power of the AP, the difference in the TX power of X MHz and Y MHz at the
+ * STA equals to the difference at the AP, and the difference in the signal RSSI
+ * at the STA. tx_pwr is a floating point number in the standard, but the error
+ * of casting to int is trivial in comparing two BSSes.
+ */
+static int wpas_channel_width_tx_pwr(const u8 *ies, size_t ies_len,
+ enum chan_width cw)
+{
+#define MIN(a, b) (a < b ? a : b)
+ int offset = wpas_channel_width_offset(cw);
+ const struct element *elem;
+ int max_tx_power = TX_POWER_NO_CONSTRAINT, tx_pwr = 0;
+
+ for_each_element_id(elem, WLAN_EID_TRANSMIT_POWER_ENVELOPE, ies,
+ ies_len) {
+ int max_tx_pwr_count;
+ enum max_tx_pwr_interpretation tx_pwr_intrpn;
+ enum reg_6g_client_type client_type;
+
+ if (elem->datalen < 1)
+ continue;
+
+ /*
+ * IEEE Std 802.11ax-2021, 9.4.2.161 (Transmit Power Envelope
+ * element) defines Maximum Transmit Power Count (B0-B2),
+ * Maximum Transmit Power Interpretation (B3-B5), and Maximum
+ * Transmit Power Category (B6-B7).
+ */
+ max_tx_pwr_count = elem->data[0] & 0x07;
+ tx_pwr_intrpn = (elem->data[0] >> 3) & 0x07;
+ client_type = (elem->data[0] >> 6) & 0x03;
+
+ if (client_type != REG_DEFAULT_CLIENT)
+ continue;
+
+ if (tx_pwr_intrpn == LOCAL_EIRP ||
+ tx_pwr_intrpn == REGULATORY_CLIENT_EIRP) {
+ int offs;
+
+ max_tx_pwr_count = MIN(max_tx_pwr_count, 3);
+ offs = MIN(offset, max_tx_pwr_count) + 1;
+ if (elem->datalen <= offs)
+ continue;
+ tx_pwr = (signed char) elem->data[offs];
+ /*
+ * Maximum Transmit Power subfield is encoded as an
+ * 8-bit 2s complement signed integer in the range -64
+ * dBm to 63 dBm with a 0.5 dB step. 63.5 dBm means no
+ * local maximum transmit power constraint.
+ */
+ if (tx_pwr == 127)
+ continue;
+ tx_pwr /= 2;
+ max_tx_power = MIN(max_tx_power, tx_pwr);
+ } else if (tx_pwr_intrpn == LOCAL_EIRP_PSD ||
+ tx_pwr_intrpn == REGULATORY_CLIENT_EIRP_PSD) {
+ if (elem->datalen < 2)
+ continue;
+
+ tx_pwr = (signed char) elem->data[1];
+ /*
+ * Maximum Transmit PSD subfield is encoded as an 8-bit
+ * 2s complement signed integer. -128 indicates that the
+ * corresponding 20 MHz channel cannot be used for
+ * transmission. +127 indicates that no maximum PSD
+ * limit is specified for the corresponding 20 MHz
+ * channel.
+ */
+ if (tx_pwr == 127 || tx_pwr == -128)
+ continue;
+
+ /*
+ * The Maximum Transmit PSD subfield indicates the
+ * maximum transmit PSD for the 20 MHz channel. Suppose
+ * the PSD value is X dBm/MHz, the TX power of N MHz is
+ * X + 10*log10(N) = X + 10*log10(20) + 10*log10(N/20) =
+ * X + 13 + 3*log2(N/20)
+ */
+ tx_pwr = tx_pwr / 2 + 13 + offset * 3;
+ max_tx_power = MIN(max_tx_power, tx_pwr);
+ }
+ }
+
+ return max_tx_power;
+#undef MIN
+}
+
+
+/**
+ * Estimate the RSSI bump of channel width |cw| with respect to 20 MHz channel.
+ * If the TX power has no constraint, it is unable to estimate the RSSI bump.
+ */
+int wpas_channel_width_rssi_bump(const u8 *ies, size_t ies_len,
+ enum chan_width cw)
+{
+ int max_20mhz_tx_pwr = wpas_channel_width_tx_pwr(ies, ies_len,
+ CHAN_WIDTH_20);
+ int max_cw_tx_pwr = wpas_channel_width_tx_pwr(ies, ies_len, cw);
+
+ return (max_20mhz_tx_pwr == TX_POWER_NO_CONSTRAINT ||
+ max_cw_tx_pwr == TX_POWER_NO_CONSTRAINT) ?
+ 0 : (max_cw_tx_pwr - max_20mhz_tx_pwr);
+}
+
+
+int wpas_adjust_snr_by_chanwidth(const u8 *ies, size_t ies_len,
+ enum chan_width max_cw, int snr)
+{
+ int rssi_bump = wpas_channel_width_rssi_bump(ies, ies_len, max_cw);
+ /*
+ * The noise has uniform power spectral density (PSD) across the
+ * frequency band, its power is proportional to the channel width.
+ * Suppose the PSD of noise is X dBm/MHz, the noise power of N MHz is
+ * X + 10*log10(N), and the noise power bump with respect to 20 MHz is
+ * 10*log10(N) - 10*log10(20) = 10*log10(N/20) = 3*log2(N/20)
+ */
+ int noise_bump = 3 * wpas_channel_width_offset(max_cw);
+
+ return snr + rssi_bump - noise_bump;
+}
+
+
/* Compare function for sorting scan results. Return >0 if @b is considered
* better. */
static int wpa_scan_result_compar(const void *a, const void *b)
struct wpa_scan_res *wb = *_wb;
int wpa_a, wpa_b;
int snr_a, snr_b, snr_a_full, snr_b_full;
+ size_t ies_len;
/* WPA/WPA2 support preferred */
wpa_a = wpa_scan_get_vendor_ie(wa, WPA_IE_VENDOR_TYPE) != NULL ||
return -1;
if (wa->flags & wb->flags & WPA_SCAN_LEVEL_DBM) {
- snr_a_full = wa->snr;
- snr_a = MIN(wa->snr, GREAT_SNR);
- snr_b_full = wb->snr;
- snr_b = MIN(wb->snr, GREAT_SNR);
+ /*
+ * The scan result estimates SNR over 20 MHz, while Data frames
+ * usually use wider channel width. The TX power and noise power
+ * are both affected by the channel width.
+ */
+ ies_len = wa->ie_len ? wa->ie_len : wa->beacon_ie_len;
+ snr_a_full = wpas_adjust_snr_by_chanwidth((const u8 *) (wa + 1),
+ ies_len, wa->max_cw,
+ wa->snr);
+ snr_a = MIN(snr_a_full, GREAT_SNR);
+ ies_len = wb->ie_len ? wb->ie_len : wb->beacon_ie_len;
+ snr_b_full = wpas_adjust_snr_by_chanwidth((const u8 *) (wb + 1),
+ ies_len, wb->max_cw,
+ wb->snr);
+ snr_b = MIN(snr_b_full, GREAT_SNR);
} else {
/* Level is not in dBm, so we can't calculate
* SNR. Just use raw level (units unknown). */
unsigned int wpas_get_est_tpt(const struct wpa_supplicant *wpa_s,
const u8 *ies, size_t ies_len, int rate,
- int snr, int freq)
+ int snr, int freq, enum chan_width *max_cw)
{
struct hostapd_hw_modes *hw_mode;
unsigned int est, tmp;
if (hw_mode && hw_mode->ht_capab) {
ie = get_ie(ies, ies_len, WLAN_EID_HT_CAP);
if (ie) {
+ *max_cw = CHAN_WIDTH_20;
tmp = max_ht20_rate(snr, false);
if (tmp > est)
est = tmp;
ie = get_ie(ies, ies_len, WLAN_EID_HT_OPERATION);
if (ie && ie[1] >= 2 &&
(ie[3] & HT_INFO_HT_PARAM_SECONDARY_CHNL_OFF_MASK)) {
+ *max_cw = CHAN_WIDTH_40;
tmp = max_ht40_rate(snr, false);
if (tmp > est)
est = tmp;
if (ie) {
bool vht80 = false, vht160 = false;
+ if (*max_cw == CHAN_WIDTH_UNKNOWN)
+ *max_cw = CHAN_WIDTH_20;
tmp = max_ht20_rate(snr, true) + 1;
if (tmp > est)
est = tmp;
if (ie && ie[1] >= 2 &&
(ie[3] &
HT_INFO_HT_PARAM_SECONDARY_CHNL_OFF_MASK)) {
+ *max_cw = CHAN_WIDTH_40;
tmp = max_ht40_rate(snr, true) + 1;
if (tmp > est)
est = tmp;
}
if (vht80) {
+ *max_cw = CHAN_WIDTH_80;
tmp = max_vht80_rate(snr) + 1;
if (tmp > est)
est = tmp;
(hw_mode->vht_capab &
(VHT_CAP_SUPP_CHAN_WIDTH_160MHZ |
VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ))) {
+ *max_cw = CHAN_WIDTH_160;
tmp = max_vht160_rate(snr) + 1;
if (tmp > est)
est = tmp;
}
}
+ if (*max_cw == CHAN_WIDTH_UNKNOWN)
+ *max_cw = CHAN_WIDTH_20;
tmp = max_he_eht_rate(he20_table, snr, is_eht) + boost;
if (tmp > est)
est = tmp;
if (cw &
(IS_2P4GHZ(freq) ? HE_PHYCAP_CHANNEL_WIDTH_SET_40MHZ_IN_2G :
HE_PHYCAP_CHANNEL_WIDTH_SET_40MHZ_80MHZ_IN_5G)) {
+ if (*max_cw == CHAN_WIDTH_UNKNOWN ||
+ *max_cw < CHAN_WIDTH_40)
+ *max_cw = CHAN_WIDTH_40;
tmp = max_he_eht_rate(he40_table, snr, is_eht) + boost;
if (tmp > est)
est = tmp;
if (!IS_2P4GHZ(freq) &&
(cw & HE_PHYCAP_CHANNEL_WIDTH_SET_40MHZ_80MHZ_IN_5G)) {
+ if (*max_cw == CHAN_WIDTH_UNKNOWN ||
+ *max_cw < CHAN_WIDTH_80)
+ *max_cw = CHAN_WIDTH_80;
tmp = max_he_eht_rate(he80_table, snr, is_eht) + boost;
if (tmp > est)
est = tmp;
if (!IS_2P4GHZ(freq) &&
(cw & (HE_PHYCAP_CHANNEL_WIDTH_SET_160MHZ_IN_5G |
HE_PHYCAP_CHANNEL_WIDTH_SET_80PLUS80MHZ_IN_5G))) {
+ if (*max_cw == CHAN_WIDTH_UNKNOWN ||
+ *max_cw < CHAN_WIDTH_160)
+ *max_cw = CHAN_WIDTH_160;
tmp = max_he_eht_rate(he160_table, snr, is_eht) + boost;
if (tmp > est)
est = tmp;
if (is_6ghz_freq(freq) &&
(eht->phy_cap[EHT_PHYCAP_320MHZ_IN_6GHZ_SUPPORT_IDX] &
EHT_PHYCAP_320MHZ_IN_6GHZ_SUPPORT_MASK)) {
+ if (*max_cw == CHAN_WIDTH_UNKNOWN ||
+ *max_cw < CHAN_WIDTH_320)
+ *max_cw = CHAN_WIDTH_320;
tmp = max_he_eht_rate(eht320_table, snr, true);
if (tmp > est)
est = tmp;
if (!ie_len)
ie_len = res->beacon_ie_len;
- res->est_throughput =
- wpas_get_est_tpt(wpa_s, ies, ie_len, rate, snr, res->freq);
+ res->est_throughput = wpas_get_est_tpt(wpa_s, ies, ie_len, rate, snr,
+ res->freq, &res->max_cw);
/* TODO: channel utilization and AP load (e.g., from AP Beacon) */
}
projects / thirdparty / hostap.git / commitdiff
