======= Understanding RX1 and RX2 with Network Latency =======

This page presents three simple examples to explain how LoRaWAN downlink reception works depending on network latency and responsiveness.

The device always opens two reception windows after each uplink:

  * **RX1** – opens shortly after sending  
  * **RX2** – opens later, giving the network more time  

If the network is slow or unstable, the response may arrive too late for RX1 and only RX2 will be usable.



===== Fast & Nearby Network =====

{{:wiki:lora:rx1_example_fast_network.png?800|Fast & Nearby Network – RX1 OK}}

**Key Points:**

  * Low latency (100–300 ms)
  * Server close to gateways
  * Downlink ready quickly

**Result:**
  * **RX1 = OK ✔️**
  * RX2 is not needed


===== Unstable Network =====

{{:wiki:lora:rx1_example_unstable_network.png?800|Unstable Network – RX1 Borderline}}

**Key Points:**

  * Cloud-hosted server (AWS / Azure)
  * Gateway in 4G
  * Latency fluctuates (800 ms to 1.5 s)

**Result:**
  * **RX1 = Borderline ⚠️**
  * Sometimes RX1 works, sometimes the response arrives too late  
  * **RX2 used as fallback ✔️**

**Recommendation:** Increase RX1Delay (ex: 1 → 3 seconds)



===== Very Slow Network =====

{{:wiki:lora:rx1_example_slow_network.png?800|Very Slow Network – RX1 Impossible}}

**Key Points:**

  * Weak cellular or satellite links
  * High backend processing load
  * Latency above 2–3 seconds

**Result:**
  * **RX1 = FAIL ❌**
  * **RX2 = Only reliable option ✔️**



===== Summary Table =====

^ Network Scenario           ^ RX1 Behavior            ^ RX2 Behavior                 ^
| Fast & Nearby              | ✔️ Works reliably        | Not needed                   |
| Unstable                   | ⚠️ Sometimes too late     | ✔️ Used as fallback             |
| Very Slow                  | ❌ Always too late        | ✔️ Only reliable option      |



===== Notes =====

  * RX1 requires the network to respond quickly.
  * RX2 provides a safety margin when the network is slow.
  * Increasing RX1Delay helps but cannot fix very slow networks.