Powerline setup with various speeds

[SaladFingers]

Hello, I have been using a PLC setup to connect a room to my LAN. I want to add another unit, but I don't need the specific connection to be as fast as the other pair, could I use that without affecting the other two units? Here's a mockup:

 

 

I'm afraid that perhaps my initial pair will downgrade to the speed of the newly added unit to maintain compatibility. Ideally I would like the original pair to function at maximum possible speed (I understand that the first unit's bandwidth will be now used for the third unit as well though) without being affected by the third unit, which should run at its own optimal speed.

 

Is this possible? The unit I'm eyeing is same brand and similar specs apart from the bandwidth.

 

 

[jpfeif]

Bitwit has a vid up on this.

[SaladFingers]

2 minutes ago, jpfeif said:

Bitwit has a vid up on this.

Could you link pls? I found a video of his about powerlines but not about mixing different speeds.

[brwainer]

Powerline, like Wifi, is a broadcast technology. Only one device can talk at a time. In order to talk to the new unit, your central unit will have to spend part of its time talking at a lower frequency / lower symbol rate (QAM256 instead of QAM512 for example). Also whenever the new unit sends traffic, also at the lower rate, the other two devices can’t be doing stuff during that time. This means that sending 50Mb to the new unit takes longer to complete than the other existing one. Therefore I would expect some amount of degredation, but not a significant amount. 

[SaladFingers]

11 minutes ago, brwainer said:

Powerline, like Wifi, is a broadcast technology. Only one device can talk at a time. In order to talk to the new unit, your central unit will have to spend part of its time talking at a lower frequency / lower symbol rate (QAM256 instead of QAM512 for example). Also whenever the new unit sends traffic, also at the lower rate, the other two devices can’t be doing stuff during that time. This means that sending 50Mb to the new unit takes longer to complete than the other existing one. Therefore I would expect some amount of degredation, but not a significant amount. 

 

Are you sure about this? The "master" unit can only communicate with one "slave" at a time? And if that's indeed the case, then the connection speed when communicating with the older unit should not be affected (other than degradation), right?

 

Finally, what happens if both "slaves" require data at the same time? Some sort of queuing? Should I expect hiccups?

[brwainer]

14 minutes ago, SaladFingers said:

 

Are you sure about this? The "master" unit can only communicate with one "slave" at a time? And if that's indeed the case, then the connection speed when communicating with the older unit should not be affected (other than degradation), right?

 

Finally, what happens if both "slaves" require data at the same time? Some sort of queuing? Should I expect hiccups?

Actually there is no master / slave - all units can talk to each other at any time. So if the computers on the two that don’t connect to the lan want to share traffic, they will do so directly. Similarly, any traffic that is Broadcast on the ethernet is only sent out once as broadcast on the powerline. I had 4 powerline adaptos in my house, and I could directly communicate between any two of them. But, that communication was still a broadcast at a physical level. If you don’t believe me, you can research it yourself, but the power cables for Powerline, the coax cables for MoCA or original ethernet (10Base2), and the air for WiFi/etc is a shared medium in which all traffic is broadcast, and you can’t have more than one device transmitting at a time.

 

If both of your “slave” devices want data from the network at the same time, they will have to wait and take turns. It is just like Wifi. Wifi also has to do the same rate-switching, as even if all clients had the same rated speed, e.g. N300 or N600, their connection will be at different rates based on signal strength and quality.

[SaladFingers]

22 minutes ago, brwainer said:

Actually there is no master / slave - all units can talk to each other at any time. So if the computers on the two that don’t connect to the lan want to share traffic, they will do so directly. Similarly, any traffic that is Broadcast on the ethernet is only sent out once as broadcast on the powerline. I had 4 powerline adaptos in my house, and I could directly communicate between any two of them. But, that communication was still a broadcast at a physical level. If you don’t believe me, you can research it yourself, but the power cables for Powerline, the coax cables for MoCA or original ethernet (10Base2), and the air for WiFi/etc is a shared medium in which all traffic is broadcast, and you can’t have more than one device transmitting at a time.

 

If both of your “slave” devices want data from the network at the same time, they will have to wait and take turns. It is just like Wifi. Wifi also has to do the same rate-switching, as even if all clients had the same rated speed, e.g. N300 or N600, their connection will be at different rates based on signal strength and quality.

 

I understand now, thanks for the clarification. So I'm looking at the same inevitable time-outs you get on wi-fi then.

 

Here's a (probably weird) question though: What if my new "slave" unit is explicitly paired with the other "slave" unit and nothing else? Could this work? As in, using the available bandwidth between the two initial units only and not have the third unit connect directly to the "master". Could that alleviate time outs (albeit limiting my bandwidth)?

[brwainer]

8 minutes ago, SaladFingers said:

 

I understand now, thanks for the clarification. So I'm looking at the same inevitable time-outs you get on wi-fi then.

 

Here's a (probably weird) question though: What if my new "slave" unit is explicitly paired with the other "slave" unit and nothing else? Could this work? As in, using the available bandwidth between the two initial units only and not have the third unit connect directly to the "master". Could that alleviate time outs (albeit limiting my bandwidth)?

Using the encryption keys, you can have multiple powerline networks in the same power grid, but each powerline adaptor can only use one encryption key at a time, and the different networks will still have to share the common medium - like multiple wireless networks operating on the same channel.

[SaladFingers]

18 minutes ago, brwainer said:

Using the encryption keys, you can have multiple powerline networks in the same power grid, but each powerline adaptor can only use one encryption key at a time, and the different networks will still have to share the common medium - like multiple wireless networks operating on the same channel.

Ah, so in order to have one "master" connecting to two other "slaves" I can't do it. One last thing to clarify then - If one unit supports lower speed, would that mean that the connection between the other too would also get lowered to the same baseline? Or can they both connect at their maximum possible speeds even if they need to take turns?

[brwainer]

2 minutes ago, SaladFingers said:

Ah, so in order to have one "master" connecting to two other "slaves" I can't do it. One last thing to clarify then - If one unit supports lower speed, would that mean that the connection between the other too would also get lowered to the same baseline? Or can they both connect at their maximum possible speeds even if they need to take turns?

They should take turns between talking at the higher possible speed and the lower possible speed, depending on the recipient of the communication. At least, that is how it works for Wifi, I believe Powerline works the same. When I had 4 powerline adaptors in my house, the control software for them was able to show me what the "link speed" between any two of them was, and it would show a number of different speeds.

[SaladFingers]

Just now, brwainer said:

They should take turns between talking at the higher possible speed and the lower possible speed, depending on the recipient of the communication. At least, that is how it works for Wifi, I believe Powerline works the same. When I had 4 powerline adaptors in my house, the control software for them was able to show me what the "link speed" between any two of them was, and it would show a number of different speeds.

Alright, thanks for all the information man, much appreciated. I might just grab the unit and test.