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<p style=“text-align: left;“>Eric,</p>
Running WDS with the 10mb image, for the same audio stream, the number of packets increased from 5000 to 30000 per minute, significantly increasing the CPU usage! It did sound really good, but the link was not stable and CPU spiking was quite evident (probably what you’re mentioning as jitter) I blamed this on the streamer not being fully compatible with 10mbs.B.
<p style=“text-align: left;“>Hi,</p>
Only saw the messages today… vacation time. Don’t have my pc with me to share the details for WDS setup. It is relatively simple, one only has to enable WDS on both, the sta (client) and the ap, and assign fixed IPs to both (on same subnet as the rest of your audio network). A truly minimal image is possible, without even relayd. Finally, a true, dumb switch like functionality is possible with all unnecessary components disabled/ removed. Also, as WDS is integral to openwrt you can enable it in existing minimal images Eric shared, the 100mbs and 10mbs. No need to develop new ones. Only drawback with wds is that it is a true backhaul so it works best in single ap, single client setups. Your control tablet or phone will have to be on a separate ssid. I’ve been running the WDS setup for almost half a year and have zero issues. CPU usage below 2% for decompressed 14/44 audio. What I did learn through WDS optimisation is that the wr902ac is really not a good access point. Literally, getting a cudy wr1300 V3 for around 30 euro will significantly reduce retries and CPU usage. Btw, had WDS active with the 10mbs minimal image and it worked, but there were issues with my streamer so I’m back at 100mbs. Hope I managed to shed some light. Also, keep in mind that a small change in orientation of the wr902ac can completely change the quality of the WiFi signal and the subsequent amount of retries.Cheers,
B.
Hi Eric,
It does sound better! Actually, I have never heard standard definition sound this good! It is the same type of sound uptick as when setting up the wr902ac for the first time – more bass, more details, but actually less bright. Just that this tweak did not give as much of an ugrade. Also, this setup allowed me to set things up with practically zero retries…this is another first.
With regards to the test…was literally thinking the same just that right now I don’t have the necessary setup. Ideally, one downloads a cd and creates a flac copy on a regular upnp nas. Simultaneously, creates two identically built wr902ac units except the Lan soeed. Finally uses mconnect app…. Free and with similar ways of packet movement and retry performance as the jplay app (bubble upnp is all over the place as it extremely burst in both WiFi directions). Then the test is simple. It just takes tons of time to prepare everything and I don’t have a Nas any more.
But your 10 Mbits build, combined with a banana pi openwrt one running on a wds setup, not relayd can get to a true wire without a wire setup for standard resolution. Literally can’t be better than this in terms of a wifi connection.
Cheers,
B.
Hi Eric,
Finally had a chance to try the 10 Mbits images. Both v4 work when connected with my laptop, but with the ps audio junior, only the option with negotiation turned off works. As it’s late I couldn’t test the sound, but streaming uncompressed files through roon everything works except the 24/192 high Res files. Don’t know how the others managed, but no go for me. Will let you know about the sound tomorrow. Also, I noticed you built it on the 25.12.4 openwrt variant. Just wanted to mention that the 24.10.xx series works just as fine if not better on the wr902ac, but uses a few percent less CPU. Same track it 99% idle on 24.10.xx Vs 93% idle on 25.12.xx series openwrt. Just mentioning in case you ever decide to build another image:)
Cheers and thank you for another tweak!
Cheers,
B.
… pressed submit too soon. All I wanted to say is that a more powerful ap with external antennas does improve the technical performance of the wr902ac as a client by giving a better and a more stable WiFi signal. Tested routers: Aruba IAP 325, cudy wr1300, bananapi openwrt one, wr902ac. When I get a bit of time I will share a bit more of the findings on the wr902ac thread.
Cheers,
B.
Hi Erik,
<p style=“text-align: center;“>Been away on a business trip and can’t wait to try the 10 MBtS image. Definitely like your idea to have an option to switch between two Lan speeds. Saves tons of tweaking time! I’ve been testing various routers as access points, primarily using openwrt wds setups, and just wanted to say that my original suspicion is correct when it comes to signal quality – the wr902ac is a really mediocre access point when looking through the prism of retries. For example I tested a cudy wr1300 which I got for 25 euro, installed a minimal openwrt image so it behaves like a wireless switch and it halved the retries and dropped the CPU utilisation to below 10% when streaming high Res uncompressed files on the wr902ac client. No matter what I did, the wr902ac as an ap always had much higher retries and gave higher cpu usage on the client. Also, for users of music servers, there was another drop when connecting the server directly to the cudy access point. Don’t ask me why, but I tested it a few times and the results were always the same.</p>Hi Eric,
Definitely looking forward to the script. I hope it will work with uncompressed high Res files. I’m theory it should just be enough.
Cheers,
B.
Hi Erik,
I’m away so can’t test. Did you try installing ethtool in openwrt to reduce the Lan speed on wr902ac?
Cheers,
B.
Hi Mario, Hubert,
I know I’m not Eric, but I have done tons of various tests and you should keep your server hard wired to the network. Ideally, you should have only the wr902ac connected to this 5ghz ssid. This will make sure your wr902ac processor is working the least as there will be least interruptions on that channel. On the other hand, make sure that your wired network is minimum 1gb on all LAN connections. Repeated tests of reducing the wired network elements to 100mb actually increases retries to the openwrt client! Don’t know why, but every option I tried gave the same result. You could enable the 2.4ghz radio and set it up as a separate said and then connect only the server to it. In theory it would be a better option then having both on the same ssid, but chances are there will be other users, devices using those 2.4 GHz frequencies and you will experience dropouts again. I would personally use the second 2.4 GHz ssid for the control device.
Hope this helps.
Boško
Hi Eric,
Definitely a good call out for the reasonings behind the additional settings modifications. I will try my best:
1. Transmit power at 0db – currently the distance between my access point and the 902AC is 60cm and I use a 10db gain external antenna on the the 902AC and while trying all the options I found out that even this 10db gain is almost too much power when the distance is so small. This means that I do not need any additional amplification from the 902AC. While negotiating interference in my place I found out that the antenna power setup on both, the access point and the 902AC, plays a significant role when it comes to retries. If too strong, or too weak, the retries will increase. If anybody is interested how a rough setup guide, continue reading… I found a way to quickly find this relatively „optimal“ strength. Basically, keep increasing the power on the access point (Tx) until you reach a plato value where the receiving unit (902AC) does not register extra signal (Rx) in db no matter how much you increase the transmit power. Set the the transmit power at the lowest setting that gives this max db reading in the 902AC (or even 1dbm less). Repeat the same exercise, but this time increasing the transmit signal (Tx) of the 902AC and monitoring the signal receiving strength (Rx) on the access point. Note that the amplification of both units should be in the similar range or the unit with a much stronger signal will choke the transmission of the other unit, again having a significant impact on retries. For example, currently antenna power settings I run are 12dbm on the access point and 10dbm on the 902AC (the strength of the external antenna alone). Finally, I found out that access point to client distance should not be too short. I had significantly lower retries at 1,5m distance than at 50cm. Yesterday I increased to 60cm and this helped much more then I hoped for, but due to my living room limitations this is the max distance I can have right now. Definitely, keep the distance 60cm or more. One final note, once the signal is stronger than -30db to -28db, it is too powerful and retries start increasing again.
2. NTP settings – this is something I had an experience many years ago in a completely non audio networking situation where I had encountered background processes when NTP settings were not synchronised. I can’t say I experienced or noticed any issues in the current setup, but since the 902AC with openwrt is still a router communicating between two IP subnets, I like it to have the least variables to try and sort out. Still not sure how to best implement this. Maybe the most efficient is to have it set to use the DHCP communicated values. This way it is automatic and will have the same setting as the main router and that is ideal.
3. Long vs short preamble – it is an error redundancy check and only recommended to use the long preamble in higher interference, low signal environments as it is more robust, but it is slower and makes the client work more as it relies on a larger and a slower header overhead. Ideally, both the access point and the client should have the same preamble enabled. In other words, if there is no interreference it is better to keep the short preamble.
4. Rx LDPC – it is a decoding „algorithm“ which is used to maximise the wifi network at full bandwidth usage by detecting and correcting errors in data transmission. In layman’s terms, it is created so that it reduces retries by fixing the received data and sending it downstream. It sounds good, but it involves many iterations to „fix“ the data and in turn requires significantly higher compute power to perform. If this option is disabled then is is a simple yes/no situation where good data gets send downstream and the corrupted data is requested again. Other than the processing power it also impacts latency due to time it takes to fix these errors. Bottom line, it is meant to enable high quality throughput in full bandwidth usage wifi scenarios. Streaming uncompressed audio is only using 1% bandwidth for 16/44 files and approximately 10% for 24/192 files on a 5ghz channel with 20mhz width. This is not even close to full bandwidth scenarios. I suggest to try disabling this one, it was some time ago I did it, but the impact was noticeable.
Through a bunch of tests I realised that the speed of wifi has nothing to do with audio streaming quality. The stability of the signal has everything to do with quality of audio streaming as impacts retries which impact the workload on the client (or even stream drops). Most of these tweaks are all geared towards this wifi stability and/or reduction of any kinds of processes in the 902 AC.
Hope I didn’t over complicate it:)
Cheers,
B.
PS. This is potentially a Pandora’s box, but if you are running two 902ACs, one as AP and one as client, I would love to se what happens if WDS or 802.11s protocols are used. Basically, they are supposed to create a completely transparent connection making the client act like a wireless switch where all the IPs are in the same IP subnet. I tried enabling it between the Aruba and the 902AC, but no luck (Even changed my main router’s (Fritzbox) IP to the openwrt range)
<p style=“text-align: left;“>Hi Stefan,</p>
In my case, openwrt has much more flexibility to fine tune the WiFi connection to the router or access point. Compared to openwrt the stock to link OS is very limited, especially in channels and power settings. In my, high WiFi interference environment I could never get a good enough signal to stream without drops. With openwrt I can get an almost perfect, interference free signal. Which I found has a very obvious impact on sound as it reduces all the work done by the 902ac to sort out all the retries. I did some tests yesterday and even a small amount of extra retries takes the 902ac load from under 10% up to 50% (this is seen within the overview section of the openwrt web interface).These are my reasons for the openwrt direction. Others might have different reasons.
Cheers,
B.
Hi Eric,
I did it again and it worked with the modified IP address to avoid IP conflict. Though, this time I used Putty to SSH into the 902AC and it worked like a charm. Thank you ! The idea of a headless setup is really making a lot of sense! Now I have to figure out how to tweak your script so that I can:
1. Set transmit power to a specific value (0dbm in my case)
2. Set up NTP connection
3. disable short preamble
4. disable Rx LDPC
The chase for the ultimate setup never ends:)
Cheers,
B.
Hi Eric,
Thank you for the detailed instructions, unfortunately I can’t get your image and script to work (yet). I only changed the LAN interface IP and inserted my wireless credential info. I’m stuck somewhere and don’t know where yet:(
Will try later again.
Cheers,
B.
Hi Eric,
Thank you for sharing. I am actually trying to install your image file, but my home router is set to the same ip as the LAN interface in the scrip (198.168.1.1). Am I correct to assume that this LAN interface IP address needs to be on a different IP subset? So if I was to change it to 198.168.2.1 it should work?
Thank you,
Bosko
Hi Eric,
Thank you for uploading the files and very detailed instructions! As I use a few other tweaks to the 902ac, can I ask you to share which final list of packages did you use? Ideally, I would like to try a similar build but with Luci interface so I can still modify some of the settings and be able to see signal strength and the load on the system. For example antenna strength, Rx ldpc, short preamble…
Thank you!
Cheers,
B.
