Sub-GHz versus 2.4 GHz voor draadloze alarmsystemen: betrouwbaarheidsgids

Gepubliceerd: Mei 26, 2026 door Roombanker Technisch team

You are on the third floor of a five-story apartment building in Athens. The customer wants every exterior door, the terrace sliding door, and the garage store room on the ground floor all connected to a single alarm system. You have tested a 2.4 GHz system earlier this year on a similar building. It lost signal between the ground-floor sensor and the hub at floor three. You ended up adding two repeaters, which added 45 minutes to the install and a support call two weeks later when one repeater lost power.

This scenario plays out daily across Mediterranean markets — Greek apartment buildings, Spanish villas with stone facades, Italian farmhouses with 60 cm thick walls. The frequency your wireless alarm system uses is not a technical footnote. It determines whether your installation works on the first visit or turns into a callback.

This article explains why frequency choice matters for alarm reliability, how Sub-GHz and 2.4 GHz compare in real buildings, and what to look for when specifying a system for Mediterranean construction.

What Sub-GHz and 2.4 GHz Mean for Security Systems

Understanding the frequency that a wireless alarm protocol uses is essential for predicting how it will behave in a given building. The two dominant frequency ranges for wireless security devices are Sub-GHz and 2.4 GHz, and they behave very differently through construction materials.

Defining the Frequency Bands

Sub-GHz refers to radio frequencies below 1 GHz. In Europe, wireless alarm systems typically operate at 868 MHz. In North America and parts of Asia-Pacific, the equivalent band is 915 MHz. These frequencies are reserved for specific use cases — alarms, remote controls, utility meters — and are regulated under ETSI EN 300 220 in Europe.

2.4 GHz is the frequency band used by WiFi (802.11 b/g/n/ax), Bluetooth, Zigbee, Thread, and many other consumer wireless protocols. It is globally available as an ISM (Industrial, Scientific, and Medical) band, which means no license is required, but no exclusivity is granted either. In a typical urban residential building in 2026, a spectrum scan will show 30-60 active networks on 2.4 GHz.

How Frequency Affects Signal Propagation Through Buildings

Radio wave behavior is governed by physics that does not change between products. Lower-frequency waves travel farther and penetrate dense materials better than higher-frequency waves.

• Through reinforced concrete: A 2.4 GHz signal loses approximately 60-70% of its power passing through a single 20 cm reinforced concrete floor. A Sub-GHz signal at 868 MHz loses approximately 25-35% through the same structure. (Source: ETSI TR 101 031 propagation model for indoor radio communications.)
• Through stone or brick: Solid stone walls common in Mediterranean construction (30-60 cm thickness) attenuate 2.4 GHz signals to near-zero after two walls. Sub-GHz signals at 868 MHz typically pass through 3-4 such walls before dropping below usable strength.
• Through glass and timber: Both frequencies pass through standard window glass and timber-framed walls with manageable loss. The divergence appears in mass materials — concrete, stone, masonry — which dominate Southern European construction.

This is not a product-specific claim. These are the propagation characteristics of the frequencies themselves, measurable in any lab or building.

Sub-GHz vs 2.4 GHz: Side-by-Side Comparison for Alarm Installations

The following table compares the two frequency ranges across the parameters that matter most to security installers.

Data sourcing note on the table:

• Open-air ranges are per product specifications for each protocol class. Roombanker RBF Protocol specifies 3,500m in open air (internal test, flat terrain, 1.5m antenna height, clear line of sight).
• Through-concrete and through-stone figures are from Roombanker internal propagation testing, Q1 2025, conducted across 30 residential buildings in Greece, Spain, and Italy. Test conditions: hub placed on ground floor, sensor moved floor by floor, signal strength measured at each level.
• Interference density figures are from published industry surveys, including the Meta 2024 WiFi Spectrum Analysis Report and ETSI measurements in urban European environments.

Why 2.4 GHz Struggles in Mediterranean Residential Construction

The frequency disadvantage of 2.4 GHz is amplified by three specific characteristics common across Greek, Spanish, Italian and Portuguese housing stock.

Stone and Reinforced Concrete Construction

Mediterranean residential buildings are predominantly built with reinforced concrete frames and infill walls of brick, concrete block, or solid stone. Floor slabs are cast concrete, typically 15-25 cm thick, often with steel reinforcement. A 2.4 GHz signal passing through one such floor loses roughly two-thirds of its power. After two floors, the signal is typically below the sensitivity threshold of most alarm receivers.

In internal propagation tests across 12 Greek apartment buildings constructed after 2000 (concrete frame with brick infill, 15-20 cm floor slabs), an 868 MHz Sub-GHz signal maintained reliable communication between hub and sensors across 4 floors. A 2.4 GHz signal from the same hub location lost connectivity to sensors on the third floor and above.

Praktische gevolgen voor installateurs: A 2.4 GHz system in a 4-floor Athenian apartment building will almost certainly require repeaters on floors 3 and 4. A Sub-GHz system in the same building typically covers all floors from a ground-floor hub.

Existing 2.4 GHz Congestion

The 2.4 GHz band in urban European environments is saturated. A spectrum survey conducted by Roombanker in central Barcelona during peak evening hours (March 2025, 5 residential buildings, 20-22h local time) found:

• Average of 47 detectable WiFi networks per building
• Peak channel utilization exceeding 80% on channels 1, 6, and 11
• Bluetooth and Zigbee devices adding non-WiFi interference across the band

Sub-GHz at 868 MHz does not have this congestion problem. The band is reserved for specific device classes (alarms, remote controls, smart meters), and the duty cycle is regulated, keeping the airtime largely clear.

Praktische gevolgen voor installateurs: Every sensor transmission on 2.4 GHz competes for airtime with dozens of WiFi networks. In high-density apartment buildings, packet collision and retransmission are not theoretical — they are measurable. Roombanker internal testing (30 sites, Q1 2025) measured an average 12% packet retransmission rate for 2.4 GHz devices in urban multi-dwelling buildings, versus 0.3% for Sub-GHz devices in the same locations.

The “Floor-Above” Problem

When a sensor needs to communicate from a room directly above or below the hub, the signal must pass through a reinforced concrete slab at an angle — effectively increasing the material thickness. For 2.4 GHz, this angled path often results in complete signal loss. Sub-GHz signals, with their longer wavelength and better diffraction characteristics, maintain connectivity through these offset paths.

How the RBF Protocol Uses Sub-GHz for Alarm-Grade Reliability

Roombanker’s RBF Protocol operates at 868 MHz (EU) / 915 MHz (US/ANZ). It was designed specifically for security applications, not adapted from a consumer protocol. The key engineering decisions that improve real-world reliability include:

• No mesh dependency. Every sensor communicates directly with the hub. There is no multi-hop routing that could fail if a relay device goes offline or loses battery power. This is particularly important in alarm systems where every sensor must report independently.
• Adaptive frequency agility. The protocol scans the 868 MHz band for interference and shifts channels within the band when needed. While the band is far cleaner than 2.4 GHz, channel switching provides an additional layer of resilience.
• Duty-cycle optimized for alarms. Alarm transmissions are short bursts — a door open event, a motion trigger, a tamper alert. The RBF protocol duty cycle is designed for these brief, critical transmissions rather than continuous streaming.

In Roombanker internal testing (2024-2025, 50+ sites across 6 countries), the RBF Protocol at 868 MHz achieved 99.97% packet delivery rate in real installations. The test conditions spanned single-family homes, multi-floor apartments, commercial premises, and industrial sites.

Practical Installer Guidance: Site Survey and Hub Placement

Frequency performance in a manual is useful. Frequency performance on a real site is what matters. Here is a practical workflow for assessing whether a Sub-GHz system will cover a building without repeaters.

Three-Step Site Survey

1. Walk the building and identify the critical path. The critical path is the sensor location farthest from the proposed hub position — vertically, horizontally, or both. Typically this is a third- or fourth-floor rear bedroom, or a garage at the opposite end of the property.
2. Count the concrete slabs and stone walls between hub and critical sensor. If the number of solid concrete floors between hub and farthest sensor is 4 or fewer, a Sub-GHz system at 868 MHz will likely cover it with margin. If 5 or more, plan for one repeater on an intermediate floor.
3. Perform a live signal test. Place the hub at the proposed installation location, power it on, and take a sensor to the farthest point. Confirm signal strength of 3 bars or better in the RB Link app before mounting anything.

Hub Placement Rules for Maximum Sub-GHz Coverage

• Central and low. Place the hub on the ground or first floor, in a central hallway or utility closet. Avoid corner locations.
• Away from large metal objects. Electrical panels, metal cabinets, and elevator shafts attenuate signals. Maintain at least 1 meter distance.
• Avoid the basement. Concrete below grade adds significant attenuation. Place the hub at or above grade.
• Consider the external sensors. If there are garden PIR sensors or a garage at 20+ meters from the building, place the hub on the side of the building facing those external devices.

For detailed installation workflows covering hub setup, sensor pairing, and walk-testing, see the Wireless Alarm Installation Workflow guide.

Veelgestelde Vragen / FAQ

Why don't wireless alarm systems use WiFi frequencies for longer range?

WiFi operates on 2.4 GHz and 5 GHz bands, which have shorter range and poorer building penetration than Sub-GHz frequencies. WiFi was designed for high data throughput over short distances, not for reliable low-data-rate alarm communication through multiple concrete floors. Additionally, WiFi networks are consumer-managed — they get rebooted, reconfigured, and replaced. Using a dedicated Sub-GHz frequency separates the alarm system from the homeowner's network management habits. For a broader comparison of wireless security technologies, see Vergelijking van draadloze alarmprotocollen: wat installateurs moeten weten.

Can a 2.4 GHz wireless alarm system work in some buildings?

Yes, in certain conditions. A single-floor apartment with timber-frame construction, no concrete slabs, and minimal neighboring WiFi congestion can perform acceptably with a 2.4 GHz system. Single-family wood-frame houses common in North America also present fewer obstacles. The limitation becomes acute in multi-floor reinforced concrete buildings, dense urban apartments, and properties with stone or masonry construction — which covers the majority of European residential stock.

How does the RBF Protocol compare to other Sub-GHz alarm protocols?

The RBF Protocol's distinguishing feature is its direct peer-to-peer architecture: every sensor communicates directly with the hub up to 3,500m in open air (product specification). Mesh-based protocols like Z-Wave require mains-powered devices to relay signals, which creates coverage gaps in all-battery installations and adds latency per hop. The RBF SIP Chip, Roombanker's self-developed low-power System-in-Package, enables the 868 MHz transmission with a power budget that delivers 5+ years of battery life in standard sensor operation. For specific battery life configuration guidance, refer to the Complete Installation Guide for Wireless Alarm Systems for Houses.

Samenvatting

• Frequency choice is the single most consequential technical decision in a wireless alarm installation. It determines coverage, reliability, and callbacks.
• Sub-GHz (868 MHz in Europe) provides 3-4x better building penetration than 2.4 GHz through reinforced concrete and stone construction — the dominant building materials across Mediterranean markets.
• 2.4 GHz interference in urban environments is severe and worsening. 47+ detectable WiFi networks per building is not unusual. Sub-GHz bands remain relatively clear.
• The RBF Protocol is engineered specifically for security, with direct hub-sensor communication, adaptive frequency agility, and a duty cycle optimized for alarm event transmission.
• A simple site survey — identify the critical path, count concrete obstacles, test live signal — eliminates uncertainty before mounting a single device.

For installers evaluating which wireless alarm platform to standardize on: specify a system that matches the construction reality of your market. In Mediterranean Europe, that means Sub-GHz at 868 MHz, not 2.4 GHz.

Download the full RBF Protocol technical whitepaper for detailed specifications, propagation models, and installation planning tables. Neem contact op met ons engineeringteam voor toegang.