With this post, I want to take some time to take a deeper dive into this 802.11be feature and how this feature I think is going to bring substantial benefits to wireless networks.
Multi-link operation (MLO) enables the use of multiple bands rather than single band in the previous WiFi specs. This allows Wi-Fi 7 clients to have better throughput, lower latency and better reliability due to connecting multiple bands at the same time.
Better Throughput
- Since a MLD client (Multi-Link Device) can connect to multiple bands at the same time, it can achieve much higher performance using this functionality. As an example, a WiFi 7 enabled client can connect to 5 GHz and 6 GHz band at the same time!
Lower Latency
- With Pre-WiFi 7 clients, when one of the band was having poor experience, clients would need to go through a complete association/disassociation process, which would introduce latency.
- With MLO functionality, this change is much more graceful where client and AP can use a different band without impacting end user experience.
Redundancy
- Since a STA MLD can establish multiple links over different bands to an AP, it can also send duplicate packets to different links, ensuring reliable performance in the event of packet loss due to poor channel environment with one of the bands.
There are multiple modes of MLO
First of all, many modes of MLO only refers to STA MLDs, not AP MLDs. APs are likely to support all of different MLO modes. I can confirm that Cisco Wi-Fi 7 APs do support all MLO modes.
Different modes of MLO are divided into two broad categories -
Single Radio and Multi-Radio
| Single Radio | Multi Radio |
|---|---|
| Multi-link Single Radio (MLSR) - Only one link operational at a given time | Enhanced Multi-Link Single Radio (eMLSR) - clients uses one radio chain to listen to one band. Many clients today are 2x2 with 2 spatial streams support. So with this mode, it can use one radio change to listen to 5 GHz and one to listen on 6 GHz. Depending on the transmit opportunity, it dynamically switches all the radio changes to that band and goes back to listening mode. |
| Multi-link Multi Radio (MLMR) STR - TX and RX, each link is working independently for TX and RX | Multi-link Multi Radio (MLMR) nSTR - TX or RX at the same time, on different links |
In summary, MLSR is supported by all MLO devices. MLMR brings the most in terms of throughput so it's good to consider which mode of MLO a client supports if you are troubleshooting any WiFi 7 performance related issues. MLSR or eMLSR allows clients to have less power consumption, which means improved battery life for endpoints.