EMLSR (Enhanced Multi-Link Single Radio)

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EMLSR (Enhanced Multi-Link Single Radio) is a key feature introduced in Wi-Fi 7 (IEEE 802.11be). Basically EMLSR is a multi-link operations (MLO) while using a single radio for transmission and reception.

Simple Operation Steps for EMLSR:

Link Setup: Device connects to an AP on multiple links (2.4GHz + 5GHz + 6GHz).

Monitoring: Listens to all links but transmits/receives on one (2.4/5/6GHz) at a time.

Fast Switching: AP schedules when the device switches link (for downlink/uplink).

EMLSR Phases:

Association Phase:

Device negotiates supported links (2.4/5/6GHz) with AP.

Monitoring Phase:

Device listens to all links but only decodes Beacons.

Active Phase:

AP schedules Tx/Rx windows via Trigger Frames (IEEE P802.11be D3.0).

EMLSR vs Traditional Wi-Fi:

Main comparison between EMLSR and EMLMR:

EMLSR: Uses one radio, switches between links (lower cost, moderate performance).

EMLMR: Uses multiple radios, true simultaneous multi-link (higher performance, more power & cost).

EMLSR Timing Parameters:

Parameter                          Value                    Description

Switching Delay                 16-32 μs               Time to retune radio between links

Beacon Interval                 100-200 ms        Link synchronization period

Trigger Frame Period      2-5 ms                  Active Tx/Rx slot duration

Benefits of EMLSR:

1. Lower Power Consumption (compared to EMLMR and STR).
2. Reduced Hardware Cost (only one radio is enough).
3. Better Efficiency than legacy Wi-Fi (avoids idle listening on unused channels).
4. Improved Latency & Reliability (faster switching between links than traditional single-link Wi-Fi).

Use Cases:

1. Smartphones & Tablets (balance performance and battery life).
2. IoT & Wearables (low-power devices with 11be features).
3. AR/VR Applications (low-latency requirements without multiple radios).

Real-World Example:

A Wi-Fi 7 smartphone uses EMLSR to:

1. Download a file on 5GHz.
2. Switch to 6GHz for a video call.
3. Monitor 2.4GHz for IoT device signals.

Limitations:

1. Not True Simultaneous: Lower throughput than EMLMR.
2. Switching Delay: Microseconds lag during transitions.
3. Scheduling Complexity: AP must manage link switching precisely.

Conclusion:

EMLSR enables Wi-Fi 7’s multi-link benefits without requiring multiple radios, making it ideal for power-sensitive and cost-constrained devices while still improving performance over Wi-Fi 6.