Dramatic Wireless Improvement

For some years I have monitored and logged connection speeds within the house network. Typically this is a non event because the network is mostly static and unchanging. I enjoy tinkering with the computers, but I tend to resist tinkering with network connectivity. Only occasionally do I check the speed test logs because I do not expect connectivity to change.

Yet I do check the logs. I noticed the laptop wireless speeds had deteriorated. I had been using the laptop occasionally but not for any common web surfing. Mostly non network tasks. Further, often when I use the laptop to test shell scripts and configuration changes I tend to use Ethernet. Thus likely I would not have observed any wireless connection performance degradation.

The test script uses iperf. Testing Ethernet showed a consistent good connection. The problem was wireless only.

The laptop is a Lenovo T400 with an Intel PRO/Wireless 5100 AGN wireless adapter. The router supports 802.11ac, but the laptop is limited to 802.11n.

Commonly I connect the laptop wireless with 5 GHz because the speeds have been faster than 2.4 GHz. Never expecting these kinds of anomalies, I designed the speed test log to be generic and not distinguish between the radios or frequency channels. Without this distinction, my fuzzy memory is with 2.4 GHz I would see about 50 Mbps and with 5 GHz about 95 Mbps. With my recent review the log showed the 5 GHz speeds to be about the same as I might expect with 2.4 GHz.

I do not know what happened but I suspected the debacle with rebuilding DD-WRT from scratch contributed partly.

Outside the router and ISP CPE, there are no other wireless devices in the house. No bluetooth, baby monitors, walkie-talkies, smart phones, etc.

Originally the shell script to log house network speeds was designed to send email notifications when the speed was well below (80%) average speed. I had disabled that feature and thus was unaware of the reduced speeds with the house wireless. I plan to restore that feature.

Without knowing the root cause I had little choice but to start tinkering with the router configuration. Eventually I restored the expected 5 GHz speeds although the final configuration was not what I had used before the router rebuild event. Originally I used a 40 MHz width with 5 GHz but now used an 80 MHz width.

I noticed the 2.4 GHz speeds were horrible at about 25 Mbps. Unlike urban areas, living in a rural area I do not worry about the 2.4 GHz band being congested. The ISP CPE is a 5 GHz device. I never noticed any 2.4 GHz interference. Yet something changed to degrade the 2.4 GHz speeds. I tinkered again with the router configuration. I ended up using channel 11 with a 40 MHz channel width rather than letting the router select the channel with Auto mode and a default 20 MHz channel width. The 2.4 GHz speeds skyrocketed to consistently between 110 to 130 Mbps.

The laptop has two other operating systems installed. To be more certain of the improvement I rebooted into each system and tested the 2.4 GHz connection. Same pleasant results.

Some days later I again tested both radios. Speeds remained consistent with 2.4 GHz at 110 to 130 Mbps and 5 GHz at 140 to 160 Mbps.

I admit my laziness through the years with not digging deeper into improving local wireless speeds, but I have no clue what caused the recent degradation. Probably I should not complain. Without the lower speeds I might never have tinkered and found the dramatic improvements.

Posted: Category: Usability Tagged: DD-WRT

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