Introduction
Signal strength is the heartbeat of every wireless communication system.
Whether you’re deploying a 5G private network, broadcasting digital TV, or setting up a long-range IoT link, the stability and adequacy of your signal directly determine whether your project delivers or fails.
In telecommunications engineering, the right signal level means fewer retransmissions, higher throughput, and compliance with regional coverage standards. The wrong level means wasted investment, unhappy customers, and regulatory headaches.
In this guide, I’ll explain what signal strength really is, how to measure it correctly, what international thresholds you should be aware of, and—most importantly—how to improve it in the field without breaking compliance rules. This is written from a B2B engineering perspective for network planners, integrators, OEMs, and procurement teams.
1. Understanding Signal Strength: Units and Metrics
1.1 Definition and Core Units
Signal strength refers to the received power at a receiver’s antenna terminal.
According to Wikipedia – Signal Strength in Telecommunications, it can be expressed in:
- dBm — decibels relative to 1 milliwatt (most common in telecoms)
- dBµV/m — decibels relative to one microvolt per meter (used in broadcast field strength measurements)
A higher (less negative) dBm value indicates a stronger signal, but it does not tell the whole story—quality matters too.
1.2 Related Metrics You’ll Encounter
- RSSI (Received Signal Strength Indicator) — A chipset-reported indicator, may include noise and interference. See Wikipedia – RSSI for standard definitions.
- RSRP (Reference Signal Received Power) — LTE/5G-specific measure of average reference signal power.
- RSRQ (Reference Signal Received Quality) — Combines power and quality; more negative = worse quality.
- SINR / SNR — Signal-to-Interference-plus-Noise Ratio; a high SINR allows higher modulation rates.
- EIRP (Equivalent Isotropically Radiated Power) — Combined transmitter power and antenna gain, important for compliance.
Reference:
- Ubiquiti – Understanding Cellular Signal Strength and Quality
- Campbell Scientific – Signal Strength & Quality
2. Why Signal Strength Matters in Real Deployments
Strong, clean signal levels:
- Reduce packet loss and retransmissions
- Improve battery life for wireless devices
- Ensure compliance with coverage regulations
- Enable higher spectral efficiency (more Mbps per Hz)
Example: A cellular IoT gateway operating at –85 dBm RSRP with a SINR of 25 dB can maintain stable low-latency links, but the same RSRP with a SINR of 5 dB will struggle with throughput.
3. International Standards and Thresholds
3.1 United States – Public Safety and FCC Requirements
Public safety in-building coverage codes often require:
- Downlink signal ≥ –95 to –109 dBm inside buildings
- Delivered Audio Quality (DAQ) thresholds for voice clarity
Example: Town of Flower Mound ERCES Specification — specifies –109 dBm for emergency responder coverage at 700/800 MHz.
3.2 Europe – ComReg 5G and LTE Benchmarks
Ireland’s ComReg defines minimum outdoor RSRP and SINR levels to ensure adequate 5G service quality (ComReg Document 21/118a):
| Metric | Min Threshold | Notes |
|---|---|---|
| RSRP | –95 dBm | Outdoor coverage |
| SINR | ≥ 10 dB | Minimum for usable throughput |
3.3 Ofcom (UK) and Other Regulators
The UK’s Ofcom coverage obligation for mobile operators often specifies outdoor coverage targets in population and geographic terms, indirectly driving minimum RSRP thresholds in the –95 to –105 dBm range.
3.4 Threshold Reference Table
| Application | Metric | Target | Reference |
|---|---|---|---|
| Wi-Fi VoIP | RSSI | ≥ –67 dBm | IEEE 802.11 guidelines |
| LTE Data | RSRP | ≥ –90 dBm | 3GPP |
| 5G URLLC | SINR | ≥ 25 dB | ITU-R M.2410 |
| DTV Broadcast | Field Strength | ≥ 50 dBµV/m | ITU-R BT.1368 |
4. Signal Strength vs Signal Quality
As LinkedIn – Signal Strength by Raju Gajavelly notes, bars on your device mean very little without knowing quality metrics.
Example:
Two LTE links can have –85 dBm RSRP. One has SINR 25 dB and delivers 80 Mbps; the other has SINR 5 dB and delivers 5 Mbps.
5. Link Budget – Predicting Performance
5.1 Formula
Rx Power (dBm) = Tx Power (dBm) + Tx Antenna Gain (dBi) – Path Loss (dB) – Cable Loss (dB) + Rx Antenna Gain (dBi) – Misc Losses (dB)
See Wikipedia – Link Budget for detailed explanation.
5.2 Cable Loss Impact
At 2.4 GHz:
| Cable Type | Loss (dB/10 m) |
|---|---|
| RG58 | 5.3 |
| LMR195 | 3.9 |
| LMR400 | 1.5 |
Replacing RG58 with LMR400 over 30 m can improve received power by ~11 dB — often the margin between pass and fail.
Example product: RF coaxial jumper LMR400 cable type N male SMA RP male LMR400 50Ω coaxial cable assembly.
5.3 Worked Example
Given:
- Tx Power: 30 dBm
- Tx Antenna Gain: 9 dBi
- Path Loss: 110 dB
- Cable Loss: 1.5 dB (LMR400, 10 m)
- Rx Antenna Gain: 9 dBi
- Misc Losses: 1 dB
Calculation: Rx Power = 30 + 9 – 110 – 1.5 + 9 – 1 = –64.5 dBm This easily meets LTE and Wi-Fi thresholds.
6. Proven Ways to Improve Signal Strength
6.1 Upgrade Cables and Connectors
Use low-loss coax like LMR400 or LMR600, paired with corrosion-resistant connectors.
Example: N female bulkhead waterproof crimp connector for LMR400 cable.
6.2 Antenna Selection and Placement
- Increase height to reduce obstructions
- Select gain appropriate for coverage pattern
- Maintain First Fresnel Zone clearance
6.3 Reduce Losses in the Path
- Shorten cable runs
- Avoid unnecessary adapters
- Use high-quality jumpers: 50ohm antenna RG174 coaxial cable jumper assembly
6.4 Waterproofing and Ruggedization
For outdoor links, IP67 connectors prevent corrosion and maintain low VSWR.
Example: Waterproof N type female to N male connector adapter.
6.5 Use Repeaters and DAS (Distributed Antenna Systems)
When compliant, these can extend coverage into deep indoor areas without exceeding legal EIRP.
7. Quick Decision Tools
7.1 Threshold Table
| Scenario | RSSI/RSRP | SINR | Recommended Action |
|---|---|---|---|
| Excellent | ≥ –70 dBm | ≥ 20 dB | Maintain |
| Fair | –85 dBm | 13–20 dB | Improve cable/antenna |
| Poor | ≤ –95 dBm | < 10 dB | Add booster or high-gain antenna |
7.2 BOM Template for Improvement
- Low-loss feeder cable (LMR400 or better)
- Weatherproof connectors
- High-gain directional antenna
- Mast and mounting kit
- Grounding kit
8. Industry Case Studies
8.1 Industrial Plant
A metal-heavy manufacturing plant had –92 dBm RSRP indoors. By replacing 25 m RG58 with LMR400 jumpers and installing a 9 dBi panel antenna, indoor RSRP improved to –82 dBm, enabling reliable VoIP.
8.2 Remote Monitoring Station
A solar-powered site in rural terrain used RF coaxial cable and a 12 dBi Yagi to improve LoRa link margin from 4 dB to 15 dB, ensuring 99.5% message delivery.
8.3 Offshore Platform
Salt spray corroded standard connectors within 6 months. Switching to IP67-rated stainless connectors preserved performance for 3+ years.
9. FAQ
Q1: Is –60 dBm always better than –70 dBm?
A: Yes for strength, but quality metrics matter.
Q2: Why is my signal strong but throughput low?
A: Likely due to poor SINR or interference.
Q3: How can I measure accurately?
A: Use calibrated tools as per Campbell Scientific guidelines.
Q4: Can better cables improve my link?
A: Absolutely. Reducing loss improves fade margin and link stability.
10. Welcome Your Inquiry
Need help selecting the right coax cables, connectors, or antennas to meet your project’s signal targets?
Contact our RF engineering team today:
Email: sales@bafitop.com
Phone: +86-15817341810
Request free engineering samples or a project-specific quotation now.
