Mdthbs

I have TpLink WA901 ND access point with OpenWRT installed, which supports up to 450 Mbps.

Unfortunately, from my Ubuntu notebook I see only Bit Rate=52 Mb/s according to iwconfig even within few meters from AP.

Notebook is Dell Inspiron with Intel Centrino Wireless N 2230, which supports up to 300 Mbps.

What to check to ensure all capabilities are activated?

On Ubuntu Notebook

$ iwconfig wlp2s0

wlp2s0    IEEE 802.11bgn  ESSID:"In The Moon Network"  

          Mode:Managed  Frequency:2.437 GHz  Access Point: 60:E3:27:8D:7A:A6   

          Bit Rate=52 Mb/s   Tx-Power=16 dBm   

          Retry short limit:7   RTS thr:off   Fragment thr:off

          Power Management:off

          Link Quality=70/70  Signal level=-29 dBm  

          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0

          Tx excessive retries:4  Invalid misc:336   Missed beacon:0







$ iw dev wlp2s0 info

Interface wlp2s0

    ifindex 3

    wdev 0x1

    addr 68:17:29:9a:e0:75

    type managed

    wiphy 0

    channel 6 (2437 MHz), width: 20 MHz, center1: 2437 MHz





$ iw dev wlp2s0 link

Connected to 60:e3:27:8d:7a:a6 (on wlp2s0)

    SSID: In The Moon Network

    freq: 2437

    RX: 39568332 bytes (83031 packets)

    TX: 4846489 bytes (30088 packets)

    signal: -29 dBm

    tx bitrate: 1.0 MBit/s



    bss flags:  CTS-protection short-preamble short-slot-time

    dtim period:    2

    beacon int: 100

On OpenWRT AP

# iw wlan0 info

Interface wlan0

        ifindex 6

        wdev 0x2

        addr 60:e3:27:8d:7a:a6

        ssid In The Moon Network

        type AP

        wiphy 0

        channel 6 (2437 MHz), width: 20 MHz, center1: 2437 MHz

        txpower 28.00 dBm



# iwinfo wlan0 info

wlan0     ESSID: "In The Moon Network"

          Access Point: 60:E3:27:8D:7A:A6

          Mode: Master  Channel: 6 (2.437 GHz)

          Tx-Power: 28 dBm  Link Quality: 66/70

          Signal: -44 dBm  Noise: -89 dBm

          Bit Rate: 144.4 MBit/s

          Encryption: WPA2 PSK (CCMP)

          Type: nl80211  HW Mode(s): 802.11bgn

          Hardware: unknown [Generic MAC80211]

          TX power offset: unknown

          Frequency offset: unknown

          Supports VAPs: yes  PHY name: phy0





# iwinfo wlan0 assoclist

68:17:29:9A:E0:75  -39 dBm / -89 dBm (SNR 50)  930 ms ago

        RX: 6.0 MBit/s                                 32886 Pkts.

        TX: 144.4 MBit/s, MCS 15, 20MHz                38245 Pkts.







root@tplink1:/etc/config# cat wireless

config wifi-device  radio0

        option type     mac80211

        option channel  auto

        option hwmode   11g

        option path     'platform/qca956x_wmac'

        option htmode   HT40+

        # REMOVE THIS LINE TO ENABLE WIFI:

        option disabled 0



config wifi-iface

        option device   radio0

        option network  lan

        option mode     ap

        option ssid     'In The Moon Network'

        option encryption psk2

This are a lot of little reasons that all add up to wireless networking being slower than the advertised rate. Ars Technica recently did a really good article about why real-life speeds never live up to what was promised, and I'll do my best to summarize it into a few succinct points. I still encourage you to read the article in whole, the author is a lot more knowledgeable and experienced than I.

To start, networked devices can only operate at the highest speed of the slowest device, which in your case is the 300 Mb/s of the laptop's wireless card. But that's the maximum theoretical bandwidth which doesn't include overhead, the things like dropped packets, headers, and random waits to ensure no packet collisions are happening on the channel. Your 300 Mb/s wifi card is really two MIMO streams of 150 Mb/s, which have a real throughput of ~42 Mb/s each due to the overhead on the channel. Two channels of 42 is 84 Mb/s, but wifi is also half duplex, which means that you can not transmit or receive at the same time. This is because the whole channel is a single collision domain meaning that to prevent packet loss only a single device can communicate on the channel at a given time, even devices that aren't on your network but are on the same channel must obey this.

So then we are reduced to ~42 Mb/s real throughput. ~42 Mb/s doesn't match any standard for throughput, so I'm guessing your operating system probably rounds it to the nearest standard it knows (don't quote me on that part though), which is how you end up with 52 Mb/s on a 300 Mb/s interface.

Bitrate in iwconfig is (approximately) the base channel rate, not what you are experiencing. Higher speeds are achieved by using more channels at once, to put it way too simply. Wikipedia has plenty of detail on it.

Your driver may support different "modulations", e.g. you can perhaps select N only and get better throughput.

lwlist modulation should show what's available.

The reported speed from iwconfig is the radio channel base rate -- what do you actually see with, say, iperf or similar?