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	Typical Value	Description
Radio Switching Delay	16–32 µs	Time to retune the radio from one band to another.
Link Switching Interval	100–200 µs	Time between switching events (scheduled by AP).
Beacon Interval	100–200 ms	Time between beacon frames (used for synchronization).
EMLSR Wakeup Time	≤ 500 µs	Time for the radio to wake from sleep and switch links.
Minimum Switch Duration	≥ 1 ms	Minimum time spent on a link before switching again.

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.