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Weightless

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Weightless

Category: Wireless

Overview

Weightless is an open LPWAN standard by the Weightless SIG with three variants: Weightless-N (uplink-only simplex), Weightless-P (full duplex, adaptive), and legacy Weightless-W (TV whitespace). It targets IoT similar to Sigfox/LoRa but fully open and royalty-free.

1. Theory & Fundamentals

  • Weightless-N: 12.5 kHz channels, simplex uplink, ~5 km range
  • Weightless-P: 12.5 kHz, full duplex, adaptive modulation BPSK/QPSK/8PSK
  • Frequency: 868 MHz (EU), 915 MHz (US) sub-GHz ISM
  • Data rate: Weightless-P 0.2–100 kbps; Weightless-N ~100 kbps burst
  • Power: 10-year coin cell target
  • Open standard: Royalty-free, fully published

2. Frame / Packet Structure

Weightless-P Frame:
  Preamble | Sync | Header | Payload(up to ~200B) | CRC
  Header: device address | frame type | sequence
  Adaptive Modulation: BPSK → QPSK → 8PSK based on SNR

Weightless-N (Sigfox-like):
  3 transmissions on different frequencies for diversity
  Payload: 12 bytes max
  Uplink only; no downlink

3. Protocol Mechanics

  • Weightless-P: TDMA with frequency hopping, ACKed uplink/downlink
  • Weightless-N: Unacknowledged; frequency diversity
  • ADR: Base station commands device to adjust modulation
  • AES-128 security on both variants
  • Network: Private base stations or Weightless operator (Telensa)

4. Hardware Implementation

  • Limited chipset; primarily Telensa/Unidata hardware
  • Sub-GHz radio similar to LoRa hardware
  • Antenna: 1/4-wave monopole 868/915 MHz
  • UART AT command interface
  • Private networks: Deploy own base stations

5. Register-Level / Configuration

void Weightless_Send(uint8_t *data, uint8_t len) {
    char cmd[60] = "AT+WLSEND=";
    for(int i=0;i<len;i++)
        sprintf(cmd+10+i*2,"%02X",data[i]);
    strcat(cmd, "\r\n");
    UART_Send(cmd);
    WaitOK(10000);
}
// AT+WLSQ  → signal quality
// AT+WLRECV → check for downlink (Weightless-P)

6. Driver / Software Development

  • UART AT command driver (same pattern as LoRa/Sigfox modules)
  • Handle ACK polling for Weightless-P
  • Retry logic for N (no ack)
  • Simple byte-array payload; encode at application level

7. Debugging & Testing

  • AT terminal for send/receive test
  • Limited commercial tooling vs LoRa
  • Check signal quality with AT+WLSQ
  • Verify base station is configured and reachable

8. Real-World Applications

  1. Smart street lighting (Telensa Weightless-P network)
  2. Smart metering
  3. Parking sensors
  4. Environmental monitoring
  5. Private campus IoT networks

9. Advanced Topics & Edge Cases

  • Ecosystem limitation: Far fewer devices/tools vs LoRaWAN
  • Telensa: Main Weightless-P commercial deployer
  • Vs LoRa: Both open; LoRa has vastly wider chipset/module ecosystem
  • Private deployment advantage: Self-contained, no operator dependency

10. Standards & Variants

Variant Direction Range Rate
Weightless-N Uplink only 5 km 100 kbps burst
Weightless-P Full duplex 2 km 0.2–100 kbps
Weightless-W Full duplex 5 km Up to 16 Mbps (deprecated)

💡 Practical Examples

Ex 1: Uplink: AT+WLSEND=0102030405 sends 5-byte payload.

Ex 2: Downlink check (P): AT+WLRECV → returns buffered downlink.

Ex 3: Adaptive rate: Base station sends ADR cmd, device switches BPSK→QPSK.

🧪 Practice Questions

Beginner: 1) Three Weightless variants? 2) What makes it open? 3) Frequency bands? 4) Weightless-N limitation? 5) Main commercial deployer?

Intermediate: 1) Compare to LoRaWAN. 2) Implement Weightless-N driver. 3) ADR mechanism. 4) AES-128 key provisioning. 5) Build private network.

Advanced: 1) SDR-based Weightless base station. 2) Compare N vs Sigfox. 3) Multi-region device. 4) 10,000-device city deployment. 5) Vs NB-IoT for metering.

Checklist

  • [ ] Configure Weightless module via AT commands
  • [ ] Send uplink payload
  • [ ] Receive downlink (Weightless-P)
  • [ ] Check signal quality
  • [ ] Configure AES-128 security
  • [ ] Compare to LoRa objectively
  • [ ] Deploy private Weightless-P base station
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