4 ms·

This is absolutely correct. I don't know the inner workings of the modulation scheme selection but suspect that the downshift is solely based on the ratio of re

This is absolutely correct. I don't know the inner workings of the modulation scheme selection but suspect that the downshift is solely based on the ratio of received to unreceived acks from the client -- without knowing the reason for the non-receipt. As far as I know, the wifi standard does not contain any provision for the client device to report its received signal level to the AP. The signal levels you typically see in the AP are the levels that the AP is hearing the client at. Some access points allow you to lock the modulation at a certain rate -- if you know for a fact all of the clients will be able to receive the signal at the required level for that modulation scheme, you can increase your overall effective capacity. Unfortunately this is not usually the case. We almost never get to control the client devices and positions, and without that control, received signal levels can't be effectively predicted.

semi-extrinsic 11y ago
With this type of stupidity, along with the string of failures when it comes to Wifi security (WEP, WPS, the clusterfuck that is Probe Request frames, etc.), shouldn't we stop listening to the IEEE and get someone who understands hardware AND networks AND cryptography AND software to start writing the next generation of standards?
- sathackr 11y ago
  IEEE has gotten a bunch of things wrong, but they have gotten a bunch of things right as well. How many other vendor-agnostic technologies are there that work as well as Wifi? For the most part my wifi-enabled device will work with any device made by any manufacturer, from the high end ones down to the cheapest junk. That level of compatibility is rare in a standard in which participation is entirely voluntary. I think the IEEE struck a balance between simplicity and ease of implementation and features. I don't think the goal was ever to design a standard that could handle thousands of endpoints on commodity hardware. For what it is, wifi works great. It falls apart when you try to make it do what it wasn't designed to do. There have been missteps along the way, but overall I think the good outweighs the bad. Lets not throw the baby out with the bathwater.
  - semi-extrinsic 11y ago
    I dunno; between USB, HDMI, Bluetooth, CAN-bus, DisplayPort, PCI Express, SATA, GSM/CDMA/HSPA/LTE, etc. etc. (none of which are IEEE organized) I don't think Wifi is that unique. In particular the various cellular network technologies face many of the same challenges as Wifi and have not had major security fails (crypto implementation errors) like Wifi has had several times.
    - sathackr 11y ago
      You've brought up some great examples of successful standards. Each of them in their current implementation work well for the task they were designed to do. Many of them have not been without their failures. GSM had several long-standing security issues, some of which went on uncorrected after disclosure [1]. WEP was designed in the 90s and I believe there are a large number of security/encryption methods designed in the 90s that have since been proven flawed, either in design or implementation (RC4/MD5/SHA1 to name a few) Bluetooth has gone a completely different direction than it's original design and is also not without its failures. But the main difference is, each of the standards you listed was designed for a specific task, and works well in doing what it was designed to do. When you leave that area of designed function, they start to break down. In relation to the wireless technologies(GSM/HSPA/CDMA/LTE, et al...), their design goal was indeed massive systems with 1000's of clients. They employ various technologies that would generally be cost-prohibitive or otherwise impractical (such as GPS synchronization) in the commodity consumer market. I haven't seen the price tag for an LTE tower site, but I bet it is several orders of magnitude larger than a $120 consumer router. Wifi was never designed to do this. I agree that wifi is not unique in its success, nor is it unique in its failures. This extends to most entities in general. All have their failures and successes, including IEEE. On a side note, I have never been that concerned with wifi encryption. The vast majority of wifi access is access to the internet. If you are not securing your data before it leaves your control, the short hop over to the access point is the least of your problems. [1]: https://en.wikipedia.org/wiki/GSM#GSM_Security https://en.wikipedia.org/wiki/GSM#GSM_Security

semi-extrinsic 11y ago

With this type of stupidity, along with the string of failures when it comes to Wifi security (WEP, WPS, the clusterfuck that is Probe Request frames, etc.), shouldn't we stop listening to the IEEE and get someone who understands hardware AND networks AND cryptography AND software to start writing the next generation of standards?

sathackr 11y ago
IEEE has gotten a bunch of things wrong, but they have gotten a bunch of things right as well. How many other vendor-agnostic technologies are there that work as well as Wifi? For the most part my wifi-enabled device will work with any device made by any manufacturer, from the high end ones down to the cheapest junk. That level of compatibility is rare in a standard in which participation is entirely voluntary. I think the IEEE struck a balance between simplicity and ease of implementation and features. I don't think the goal was ever to design a standard that could handle thousands of endpoints on commodity hardware. For what it is, wifi works great. It falls apart when you try to make it do what it wasn't designed to do. There have been missteps along the way, but overall I think the good outweighs the bad. Lets not throw the baby out with the bathwater.
- semi-extrinsic 11y ago
  I dunno; between USB, HDMI, Bluetooth, CAN-bus, DisplayPort, PCI Express, SATA, GSM/CDMA/HSPA/LTE, etc. etc. (none of which are IEEE organized) I don't think Wifi is that unique. In particular the various cellular network technologies face many of the same challenges as Wifi and have not had major security fails (crypto implementation errors) like Wifi has had several times.
  - sathackr 11y ago
    You've brought up some great examples of successful standards. Each of them in their current implementation work well for the task they were designed to do. Many of them have not been without their failures. GSM had several long-standing security issues, some of which went on uncorrected after disclosure [1]. WEP was designed in the 90s and I believe there are a large number of security/encryption methods designed in the 90s that have since been proven flawed, either in design or implementation (RC4/MD5/SHA1 to name a few) Bluetooth has gone a completely different direction than it's original design and is also not without its failures. But the main difference is, each of the standards you listed was designed for a specific task, and works well in doing what it was designed to do. When you leave that area of designed function, they start to break down. In relation to the wireless technologies(GSM/HSPA/CDMA/LTE, et al...), their design goal was indeed massive systems with 1000's of clients. They employ various technologies that would generally be cost-prohibitive or otherwise impractical (such as GPS synchronization) in the commodity consumer market. I haven't seen the price tag for an LTE tower site, but I bet it is several orders of magnitude larger than a $120 consumer router. Wifi was never designed to do this. I agree that wifi is not unique in its success, nor is it unique in its failures. This extends to most entities in general. All have their failures and successes, including IEEE. On a side note, I have never been that concerned with wifi encryption. The vast majority of wifi access is access to the internet. If you are not securing your data before it leaves your control, the short hop over to the access point is the least of your problems. [1]: https://en.wikipedia.org/wiki/GSM#GSM_Security https://en.wikipedia.org/wiki/GSM#GSM_Security