I am a total noob with OpenWrt but have a bit of experience with coding. I recently bought a Linksys WRT 1200ac V2 router and installed OpenWrt Chaos Calmer 15.05.1. My intention was to disable the diversity and configure the antennas on the router such that; one antenna is TX and the other antenna is RX.

I used the following commands to configure the antennas

1. First I disabled the radios in Luci
2. uci set wireless.radio1.diversity=0
3. uci set wireless.radio1.txantenna=1
4. uci set wireless.radio1.rxantenna=2
5. uci commit wireless
6. wifi

This is what i get when for the /etc/config/wireless file:

************************************************************************************************************************************
root@OpenWrt:/etc/config# cat wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option channel '36'
        option hwmode '11a'
        option path 'soc/soc:pcie-controller/pci0000:00/0000:00:01.0/0000:01:00.0'
        option htmode 'VHT80'
        option country 'US'
        option txpower '23'

config wifi-iface
        option device 'radio0'
        option mode 'ap'
        option ssid 'OpenWrt'
        option network 'lan'
        option encryption 'psk2'
        option key 'abcdefghijkl'

config wifi-device 'radio1'
        option type 'mac80211'
        option channel '11'
        option hwmode '11g'
        option path 'soc/soc:pcie-controller/pci0000:00/0000:00:02.0/0000:02:00.0'
        option htmode 'HT20'
        option country 'US'
        option diversity '0'
        option txantenna '1'
        option rxantenna '2'
        option txpower '0'

config wifi-iface
        option device 'radio1'
        option mode 'ap'
        option ssid 'OpenWrt'
        option network 'lan'
        option encryption 'psk2'
        option key 'abcdefghijkl'
************************************************************************************************************************************
I then turned back on the radios in Luci and tested to check if the antenna configuration has worked but it did not. I then checked the available antennas using the command: iw phy phy1 info

************************************************************************************************************************************
root@OpenWrt:/etc/config# iw phy phy1 info
Wiphy phy1
        max # scan SSIDs: 4
        max scan IEs length: 2242 bytes
        Retry short limit: 7
        Retry long limit: 4
        Coverage class: 0 (up to 0m)
        Available Antennas: TX 0 RX 0
        Supported interface modes:
                 * managed
                 * AP
                 * AP/VLAN
                 * monitor
        Band 1:
                Capabilities: 0x6f
                        RX LDPC
                        HT20/HT40
                        SM Power Save disabled
                        RX HT20 SGI
                        RX HT40 SGI
                        No RX STBC
                        Max AMSDU length: 3839 bytes
                        No DSSS/CCK HT40
                Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
                Minimum RX AMPDU time spacing: 4 usec (0x05)
                HT TX/RX MCS rate indexes supported: 0-15, 32
                VHT Capabilities (0x33801931):
                        Max MPDU length: 7991
                        Supported Channel Width: neither 160 nor 80+80
                        RX LDPC
                        short GI (80 MHz)
                        SU Beamformer
                        SU Beamformee
                        RX antenna pattern consistency
                        TX antenna pattern consistency
                VHT RX MCS set:
                        1 streams: MCS 0-9
                        2 streams: MCS 0-9
                        3 streams: not supported
                        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: not supported
                        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:
                        * 2412 MHz [1] (30.0 dBm)
                        * 2417 MHz [2] (30.0 dBm)
                        * 2422 MHz [3] (30.0 dBm)
                        * 2427 MHz [4] (30.0 dBm)
                        * 2432 MHz [5] (30.0 dBm)
                        * 2437 MHz [6] (30.0 dBm)
                        * 2442 MHz [7] (30.0 dBm)
                        * 2447 MHz [8] (30.0 dBm)
                        * 2452 MHz [9] (30.0 dBm)
                        * 2457 MHz [10] (30.0 dBm)
                        * 2462 MHz [11] (30.0 dBm)
                        * 2467 MHz [12] (disabled)
                        * 2472 MHz [13] (disabled)
                        * 2484 MHz [14] (disabled)
        valid interface combinations:
                 * #{ AP } <= 16, #{ managed } <= 1,
                   total <= 16, #channels <= 1, 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

************************************************************************************************************************************
I noticed that the available antennas are assigned TX0 and RX0 which if I am not mistaken means that there are no antennas available for configuration. How do I enable antenna configuration for my router? Is there something I am missing or you cannot configure antennas for this device?

Thanks in advance

I don't think that you can, nor would you really want to.  Diversity reception was used by g hardware.  n and ac use MIMO and STBC, which involve transmitting different data on two or more antennas at the same time.  That improves the bit rate and reliability of the connection.

Why?

@ mk24 - I think you made a mistake in your comment because diversity and MIMO are one in the same thing, MIMO makes use of spatially diverse streams to increase the channel capacity. So any router that has multiple antennas uses diversity ( which is what MIMO is all about) regardless of the standard g/n/ac.

The "diversity" setting is a holdover from g chips and drivers that may have had multiple receive antennas but always a single transmit chain.  g does not implement any true MIMO concepts, it was simple parallel reception to have two chances of a correct decode.

(Last edited by mk24 on 28 Aug 2017, 14:03)

The link below is a discussion on how to select the Tx/Rx antenna for a TP-Link  WDR4300 which supports both n and ac standards:

xttps://forum.openwrt.org/viewtopic.php?id=39262

NB: PLEASE REPLACE THE xttps with an h ttps in the links

The link below gives the output of    iw list   for this router:

xttps://pastebin.com/ZCu5RhhB

As can be seen from the output, there are available antennas that can be configured for Tx/Rx for standards the n and ac standards. So I am sure that you should be able to configure the antennas for any MIMO router.

(Last edited by elichidude on 28 Aug 2017, 15:52)

Why would one want to do so?

@tmo26 I would like to do some signal processing on the Wi-Fi RF signal using the bladeRF SDR board and in order for me to do so I need the router to transmit on one port and receive on the other port.