Implement dynamic MCS selection based on signal strength in vWIFI driver #80
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It seems that you are adjusting the MCS based on the current signal strength. However, what if a user wants to set the MCS manually using a command like iw dev wlan0 set bitrates ht-mcs-2.4 <mcs_index>?
To support this, you could consider implementing the set_bitrate_mask() callback in your cfg80211_ops and storing the specified MCS in the corresponding vwifi interface structure.
Thanks for you suggestion ,I can try to included the MCS for maunally adjust ! |
This commit enhances the vWIFI driver by implementing dynamic Modulation and Coding Scheme (MCS) selection in the `vwifi_get_station` function, adjusting the MCS index based on signal strength After implement dynamic MCS can avoid TX power waste for a bad channel quality
Implement the set_bitrate_mask callback in cfg80211_ops to support manual MCS settings using `iw dev <interface> set bitrates ht-mcs-2.4 <mcs_index>`, addressing reviewer feedback. Store the selected MCS in vwifi_vif->manual_mcs and track its state with vwifi_vif->manual_mcs_set. Support MCS indices 7, 15, 23, and 31, with validation and logging. Enable High Throughput (HT) in nf_band_2ghz with MCS 0–31, using IEEE80211_HT_CAP_SUP_WIDTH_20_40 for 20 MHz compatibility. Fix compilation errors by initializing rx_mask statically and removing const qualifiers from channel/rate arrays. Improve vwifi_connect to ensure stable association. Tested with `iw dev vw1 set bitrates ht-mcs-2.4 15`, achieving MCS 15 at 130.0 MBit/s (bitrate calculation pending refinement to ~52 MBit/s). Test commands format $sudo ip netns exec ns1 iw dev vw1 link $sudo ip netns exec ns1 iw dev vw1 set bitrates ht-mcs-2.4 15 /*(changable 7,15,23,31)*/ $sudo ip netns exec ns1 iw dev vw1 link
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vwifi.c
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| @@ -88,6 +88,8 @@ struct vwifi_vif { | |||
| struct wireless_dev wdev; | |||
| struct net_device *ndev; | |||
| struct net_device_stats stats; | |||
| int manual_mcs; /* ADDED: Store user-specified MCS */ | |||
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Remove "ADDED:" prefix from the comment
vwifi.c
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| @@ -88,6 +88,8 @@ struct vwifi_vif { | |||
| struct wireless_dev wdev; | |||
| struct net_device *ndev; | |||
| struct net_device_stats stats; | |||
| int manual_mcs; /* ADDED: Store user-specified MCS */ | |||
| bool manual_mcs_set; /* ADDED: Flag to indicate manual MCS override */ | |||
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Remove "ADDED:" prefix from the comment
vwifi.c
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| @@ -1728,13 +1743,8 @@ static int vwifi_start_ap(struct wiphy *wiphy, | |||
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| /* Initialize hrtimer of beacon */ | |||
| pr_info("vwifi: init beacon_timer.\n"); | |||
| #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 15, 0) | |||
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Don't modify unrelated code segment!
You should align with the latest version of vwifi.
First,the code handles MCS selection and modulation assignment, either manually (based on vif->manual_mcs_set and vif->manual_mcs) or automatically (based on signal strength). Second,The vWIFI driver constrains MCS indices to 7, 15, 23, and 31 to simplify rate calculation, testing, and implementation. This avoids the need for a comprehensive calculation of data-rates to handle all 32 MCS indices, varying streams, and channel widths. The chosen indices represent a range of modulations (BPSK to 64-QAM) for 4 streams, supporting both manual (iw commands) and automatic (signal-based) modes. The code’s design prioritizes simplicity for a virtual driver, ensuring functionality (as shown in your test output) while limiting complexity. And thanks for you thoughtful question,it might be the next PR to optimize it ! |
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Nit: It might be better to squash all the “Fix coding style” commits. |
| @@ -2,7 +2,7 @@ interface=vw0 | |||
| driver=nl80211 | |||
| debug=1 | |||
| ctrl_interface=/var/run/hostapd | |||
| ctrl_interface_group=0 | |||
| ctrl_interface_group=root | |||
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The changes to the MCS configuration logic and the hostapd.conf control group setting serve different purposes and should be separated into distinct PRs.
The MCS logic affects runtime behavior of the vwifi driver, while the ctrl_interface_group=root change only impacts permission control for the hostapd socket.
Splitting them would improve clarity, ease future debugging, and allow better tracking of changes.
| const char *modulation; | ||
| if (vif->manual_mcs_set) { | ||
| mcs_index = vif->manual_mcs; | ||
| switch (mcs_index) { |
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According to IEEE 802.11n, MCS indices 7, 15, 23, and 31 all use 64-QAM modulation.
You should revise the descriptions associated with each MCS index accordingly, or consider modifying your design if your intention was to differentiate based on modulation type.
ref:
mcsindex
This commit enhances the vWIFI driver by implementing dynamic Modulation and Coding Scheme (MCS) selection in the
vwifi_get_stationfunction, adjusting the MCS index based on signal strengthAfter implement dynamic MCS can avoid TX power waste for a bad channel quality