Model: Ubiquiti UniFi-AC-PRO
Architecture: Qualcomm Atheros QCA956X ver 1 rev 0
Firmware: OpenWrt 18.06.1 r7258-5eb055306f / LuCI openwrt-18.06 branch (git-18.228.31946-f64b152)
Kernel: 4.9.120
I'm trying to understand a couple key bits on how OpenWRT channel selection works for the 5.0MHz band with this AP. Output of 'iw list' (below) only shows 20MHz channels, but also that the unit supports 80MHz widths. LuCi presents these same channels, and offers widths of 20, 40 and 80MHz. I have two questions.
First, how do I configure hostapd for a 80MHz signal? With the stock UBNT firmware, it is possible to select the first 20MHz channel of an 80MHz band and then indicate bonding of higher, adjacent 20MHz channels to achieve 40MHz or 80MHz. Or, the top of an 80MHz band and indicate bonding of lower, adjacent 20MHz channels. In a nutshell, that's what the Ubiquiti engineers are describing in:
Do hostapd configuration options support a grammar for expressing this? Setting channel 36 or 149 at 80MHz width shows only 40MHz in Wavemon. Channel set to 'auto' and width at 80MHz goes for channel 36 at 40MHz.
Second, with hostapd does the 20MHz channel selection + 80MHz width just center on the selected channel and impinge on -40MHz and +40MHz of adjacent space? The cited article mentions a way for directing bonding upward or downward. So I'm wondering if hostapd is silently doing something similar. Or to ask this a slightly different way, should I pick 20MHz channels closer to the center of the 80MHz widths, say, 40, 44, 153, or 157?
Wiphy phy0
max # scan SSIDs: 16
max scan IEs length: 199 bytes
max # sched scan SSIDs: 0
max # match sets: 0
max # scan plans: 1
max scan plan interval: -1
max scan plan iterations: 0
Retry short limit: 7
Retry long limit: 4
Coverage class: 1 (up to 450m)
Device supports AP-side u-APSD.
Available Antennas: TX 0x7 RX 0x7
Configured Antennas: TX 0x7 RX 0x7
Supported interface modes:
* managed
* AP
* AP/VLAN
* monitor
* mesh point
Band 2:
Capabilities: 0x19ef
RX LDPC
HT20/HT40
SM Power Save disabled
RX HT20 SGI
RX HT40 SGI
TX STBC
RX STBC 1-stream
Max AMSDU length: 7935 bytes
DSSS/CCK HT40
Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
Minimum RX AMPDU time spacing: 8 usec (0x06)
HT TX/RX MCS rate indexes supported: 0-23
VHT Capabilities (0x338001b2):
Max MPDU length: 11454
Supported Channel Width: neither 160 nor 80+80
RX LDPC
short GI (80 MHz)
TX STBC
RX antenna pattern consistency
TX antenna pattern consistency
VHT RX MCS set:
1 streams: MCS 0-9
2 streams: MCS 0-9
3 streams: MCS 0-9
4 streams: not supported
5 streams: not supported
6 streams: not supported
7 streams: not supported
8 streams: not supported
VHT RX highest supported: 0 Mbps
VHT TX MCS set:
1 streams: MCS 0-9
2 streams: MCS 0-9
3 streams: MCS 0-9
4 streams: not supported
5 streams: not supported
6 streams: not supported
7 streams: not supported
8 streams: not supported
VHT TX highest supported: 0 Mbps
Frequencies:
* 5180 MHz [36] (23.0 dBm)
* 5200 MHz [40] (23.0 dBm)
* 5220 MHz [44] (23.0 dBm)
* 5240 MHz [48] (23.0 dBm)
* 5260 MHz [52] (23.0 dBm) (radar detection)
* 5280 MHz [56] (23.0 dBm) (radar detection)
* 5300 MHz [60] (23.0 dBm) (radar detection)
* 5320 MHz [64] (23.0 dBm) (radar detection)
* 5500 MHz [100] (23.0 dBm) (radar detection)
* 5520 MHz [104] (23.0 dBm) (radar detection)
* 5540 MHz [108] (23.0 dBm) (radar detection)
* 5560 MHz [112] (23.0 dBm) (radar detection)
* 5580 MHz [116] (23.0 dBm) (radar detection)
* 5600 MHz [120] (23.0 dBm) (radar detection)
* 5620 MHz [124] (23.0 dBm) (radar detection)
* 5640 MHz [128] (23.0 dBm) (radar detection)
* 5660 MHz [132] (23.0 dBm) (radar detection)
* 5680 MHz [136] (23.0 dBm) (radar detection)
* 5700 MHz [140] (23.0 dBm) (radar detection)
* 5720 MHz [144] (23.0 dBm) (radar detection)
* 5745 MHz [149] (30.0 dBm)
* 5765 MHz [153] (30.0 dBm)
* 5785 MHz [157] (30.0 dBm)
* 5805 MHz [161] (30.0 dBm)
* 5825 MHz [165] (30.0 dBm)
* 5845 MHz [169] (disabled)
valid interface combinations:
* #{ AP, mesh point } <= 8, #{ managed } <= 1,
total <= 8, #channels <= 1, STA/AP BI must match, radar detect widths: { 20 MHz (no HT), 20 MHz, 40 MHz, 80 MHz }
HT Capability overrides:
* MCS: ff ff ff ff ff ff ff ff ff ff
* maximum A-MSDU length
* supported channel width
* short GI for 40 MHz
* max A-MPDU length exponent
* min MPDU start spacing
Device supports VHT-IBSS.