Global Mobile Frequency Bands Explained: A Practical Guide to IoT SIM and Module Selection

In cross-border IoT deployments, a common issue arises where SIM cards are active and device hardware is functioning correctly. While connectivity remains stable during lab tests in major cities, the devices experience network dropouts, get stuck on 2G networks, or suffer from extremely low data rates when deployed in suburban, rural, or remote areas. Many attribute these issues to poor SIM quality or weak local signal coverage. However, the root cause is often a mismatch between the frequency bands supported by the IoT module and the actual mobile network bands deployed by local carriers.

Radio spectrum planning varies significantly across countries and continents; no single module can support all regions globally. RF propagation follows clear physical principles: lower frequencies offer better diffraction and wall penetration, enabling longer range but limited bandwidth and peak speeds; higher frequencies provide wider bandwidth and faster transmission rates but suffer from rapid signal attenuation and poor coverage in obstructed environments. Low bands ensure reliable device connectivity, while mid-to-high bands deliver high-speed data. When selecting IoT modules for overseas markets, focus not only on urban mainstream bands but also prioritize low-band wide-coverage options for rural and remote areas—this directly determines real-world device usability.

I. Basics of Mobile Communication Frequency Bands

1.1 Band Numbering Naming Convention

The industry follows a unified frequency band naming standard to facilitate consistent communication among hardware vendors, carriers, and platform providers:

1. LTE-4G band, identified with the prefix B (Band), e.g., B3, B8, B28;
2. 5G NR new radio frequency bands, identified by the prefix n, such as n3, n78;
3. Spectrum resources support refarming and reuse: the same physical frequency band can be used to deploy both 4G LTE and 5G NR networks.

1.2 FDD and TDD duplexing modes

Mobile communication uses two duplexing methods: FDD (Frequency Division Duplex) and TDD (Time Division Duplex). They differ in operation, coverage capabilities, and application scenarios. Understanding these differences is essential for IoT development.

• FDD (Frequency Division Duplex)Uplink data transmission from the terminal and downlink data delivery from the base station each occupy separate, independent frequency resources—similar to a two-way separated highway, allowing simultaneous transmission and reception. Key advantages include extended network coverage, high stability in mobile scenarios, and low latency. Globally, most wide-area, low-frequency bands (e.g., B3, B8, B20, B28) operate in FDD mode, making it the primary network technology relied upon by IoT devices overseas.
• TDD (Time Division Duplexing)Uplink and downlink share the same frequency band, using time slots to switch between transmission and reception—similar to a single-lane road with bidirectional traffic alternating by time. Advantages: high spectrum efficiency, ideal for urban capacity expansion. Disadvantages: limited coverage radius and weaker stability in high-mobility scenarios compared to FDD. In Southeast Asia, TDD bands such as B40 and B41 are widely used to supplement urban capacity.

Business Tip: For IoT devices deployed in remote, vehicle-mounted, or long-distance monitoring scenarios, prioritize FDD low-band. TDD is better suited as an urban supplement and is not ideal for wide-area rural coverage.

1.3 Frequency Layering and IoT Business Scenarios

Frequency range	Typical Frequency Bands	Key Features	IoT Application Scenarios
Low Frequency < 1 GHz (700-960 MHz)	B8(900), B20(800), B28(700-APT)	Long-range transmission, strong wall penetration and diffraction, limited bandwidth, moderate data rates	Ensures basic connectivity for rural, remote, vehicle-mounted, and underground devices.
Medium Frequency 1-3GHz	B1(2100)、B3(1800)	Balanced coverage and speed, the most widely deployed globally.	City-wide network connectivity; the core frequency band for overseas IoT
>3GHz	B7(2600), n78(3.5 GHz)	High speed, high user capacity; severe attenuation in obstructed environments results in a small coverage radius.	High-speed data in urban hotspots; no signal in rural areas.

In simple terms, low-frequency bands determine whether a device has signal coverage, while mid-to-high frequency bands determine how fast the connection is. Many overseas projects passed urban testing with no issues, but deployments in remote areas frequently dropped connections. The root cause is the missing low-frequency wide-coverage band on the module.

1.4 5G FR1 vs. FR2

• FR1 (Sub-6G, below 6 GHz): Currently, the mainstream commercial standard for global IoT is 8, which offers excellent performance. Both n78 and n3 in the table below belong to FR1. Most overseas IoT modules only support the Sub-6G band.
• FR2 (mmWave, above 24 GHz)Extremely high data rates, but coverage is limited to hundreds of meters. High deployment costs make it unsuitable for wide-area IoT; standard IoT projects do not need to consider millimeter-wave bands.

1.5 The Two Major Camps of Global Hardware Modules

Spectrum planning varies significantly across continents. Module hardware RF filters are factory-fixed and cannot be modified via flashing or firmware updates to support different frequency bands.

1. EU/NA Version ModCore supports B1/B3/B7/B8/B28; Europe adds B20. Hardware does not include North American bands B2/B4/B5/B12/B66. When using the Eurasia module in North America, it will fall back to 2G and cannot access 4G.
2. Americas Region ModSupports B2/B4/B5/B12/B17/B66 only; lacks B20. Not directly usable in Europe or Asia-Pacific.

II. Overview of Major Global Commercial Frequency Bands

Frequency Band	Frequency	Duplex Mode	Primary Deployment Region	Business Purpose Description
B1	2100 MHz	FDD	Asia-Pacific, Europe	Urban Capacity Band
B3	1800 MHz	FDD	Most countries worldwide	4G urban main frequency band; essential IoT band overseas
B7	2600 MHz	FDD	Asia, Europe, Latin America	High capacity, short range; designed for urban areas.
B8	900 MHz	FDD	Asia-Pacific, Europe, Africa; not deployed in North America	Wide coverage with strong signal penetration in suburban areas and through walls.
B20	800 MHz	FDD	Europe only	Low-frequency in rural Europe; Southeast Asia and Mongolia do not use B20.
B28	700MHz-APT	FDD	APAC, Mongolia, Southeast Asia, Latin America	Asia-Pacific Rural Gold Low-Frequency: Missing this band causes severe suburban connectivity loss.
B40	2300 MHz	Test-Driven Development	Southeast Asia, South Asia	Mainstream TDD 4G Expansion Bands in Southeast Asia
n78	3300-3800 MHz	Test-Driven Development	Global Mainstream 5G	Primary mid-band for 5G; most countries prioritize deploying n78

Key ReminderIn countries like Mongolia, Malaysia, and Indonesia, B28 is essential for suburban and rural connectivity. Since the module's hardware does not support B28, you will have normal 4G service in urban areas but lose 4G coverage once you move to the suburbs, causing the device to fall back to 2G or drop off the network entirely.

III. Summary of Key Mobile Communication Frequency Bands in Major Global Regions

Asia (Mongolia, Southeast Asia; high-frequency usage regions for international IoT SIMs)

Country	2D code	2G GSM	4G-LTE FDD	4G-LTE TDD	5G-NR
Mongolia	MN	900,1800	B3,B8,B20,B28	-	n3, n7 8
China	CN	900,1800	B1,B3,B5,B8	B38,B40,B41	n1, n3, n5, n8, n28, n41, n78, n79
Vietnam	Vietnam	900,1800	B1,B3,B7,B8	B40	n1, n3, n7 8
Malaysia	MY	900,1800	B1,B3,B7,B8,B28	B40	n28,n78
Indonesia	ID	900,1800	B3,B5,B8,B28	B40	n1, n3, n4 0, n7 8
Thailand	TH	900,1800	B1,B3,B7,B8,B20,B28	B40	n1, n3, n7 8
Singapore	SG	900,1800	B1,B3,B7,B8	B40	n1,n78
Philippines	PH	900,1800	B1,B3,B5,B7,B28	B41	n1, n3, n7 8
Cambodia	KH	900,1800	B1,B3,B7,B8	B40	n78
Laos	LA	900,1800	B1,B3,B8	B40	n78
Myanmar	MM	900,1800	B1,B3,B8	B40	n78
Brunei	BN	900,1800	B1,B3,B7,B8	B40	n78
Timor-Leste	TL	900,1800	B1,B3,B8	B40	-
India	IN	900,1800	B1,B3,B5,B8	B40,B41	n1, n3, n5, n78

Europe (most EU countries have harmonized spectrum)

General benchmarks: 2G GSM 900/1800; 4G FDD B1, B3, B7, B8, B20, B28; TDD B38; 5G mainstream n1, n3, n78.

Country	Code	4G-FDD	4G-TDD	5G-NR
Germany	DE	B1,B3,B7,B8,B20,B28	B38	n1, n3, n7 8
France	FR	B1,B3,B7,B8,B20,B28	B38	n1, n3, n7 8
United Kingdom	GB	B1,B3,B7,B8,B20,B28	B38	n1, n3, n7 8
Italy	IT	B1,B3,B7,B8,B20,B28	B38	n1, n3, n7 8
Spain	ES	B1,B3,B7,B8,B20,B28	B38	n1, n3, n7 8

Note: B20 is a Europe-exclusive low-frequency band and has no practical network coverage in Southeast Asia or Mongolia.

Americas (Hardware not compatible with Eurasia)

Country	Code	2G	4G-FDD	4G-TDD	5G-NR
United States	US	850,1900	B2,B4,B5,B12,B17,B66	-	n2, n5, 6, n77, n78
Canada	CA	850,1900	B2,B4,B5,B12,B17,B28	-	n2, n5, n6 6, n7 8
Brazil	Brazil	850,900,1800,1900	B1,B3,B7,B28	-	n3, n7 8
Argentina	AR	850,1900	B1,B2,B4,B7,B26,B28	-	n78

Note: To enter the North American market, you must procure the Americas version hardware module. The Eurasia version lacks key frequency bands required for North America and cannot connect to local 4G networks.

Oceania

Country	Code	4G-FDD	4G-TDD	5G-NR
Australia	Australia	B1,B3,B5,B7,B8,B28	B40	n1, n3, n5, n78
New Zealand	New Zealand	B1,B3,B7,B8,B28	-	n1,n78

Typical African Countries

Country	Code	4G-FDD	4G-TDD	5G-NR
South Africa	ZA	B1,B3,B8,B20,B28	B40	n78
Nigeria	NG	B1,B3,B8	B40	n78
Egypt	Egypt	B1,B3,B8,B20	B40	n78

IV. Key Selection Criteria for Implementing IoT Solutions

1. The frequency band is determined by the RF hardware and cannot be modified by software.The supported frequency bands depend on the hardware RF components. An EMEA module cannot be converted into a North America module by flashing firmware. During the early project selection phase, you must verify the module datasheet to ensure full coverage of all critical bands for the target countries.
2. Urban testing availability does not equate to nationwide service availability.Testing only in major cities is insufficient. Low-frequency, wide-coverage bands like B8, B28, and B20 determine a device's ability to maintain connectivity in suburban and rural areas. For example, in Mongolia, a module supporting only B3 can connect in Ulaanbaatar city but requires B28 for stable 4G registration in rural scenarios.
3. Suggest adding a frequency band field to the platform database.: For the international IoT SIM platform, add two business fields to the plan database: lte_band (LTE bands required for this country) and nr_band (5G NR bands available in this country). Example data for Mongolia: Mongolia, MN, B3, B8, B20, B28,, n3, n78. This facilitates backend business validation and R&D reference.
4. A Balanced View on 5G's Value in the IoTFor most overseas IoT deployments, 4G network stability is prioritized. In many countries, 5G coverage is limited to urban centers, with no signal in suburban areas. Although n78 is a global mainstream mid-band 5G frequency, local operator deployment must be evaluated. Since IoT applications typically involve small data uploads, 4G Cat-1 is often sufficient; there is no need to blindly pursue 5G hardware.
5. Prioritize radio compliance certificationIn addition to frequency matching, device exports must obtain mandatory certifications for the target market (e.g., CE in Europe, FCC in the US). RF transmit power and parameters must comply with local radio regulations to avoid network access issues and compliance penalties. Spectrum planning is managed by each country's national radio authority; even within the same country, deployed bands may vary across operators.

V. Troubleshooting Common Network Issues

1. Urban areas have stable connectivity; rural zones experience frequent dropouts: likely missing low-frequency wide-coverage bands (B28/B8/B20).
2. Europe operates normally; in the US, only 2G networks are available. The module is the Eurasia version and lacks key North American bands such as B2/B4/B12.
3. Can register on the network, but data speeds are low: missing high-frequency capacity bands; devices remain camped on narrow-bandwidth low-frequency carriers.
4. Same IoT card: Module A connects successfully, but Module B fails. Compare the supported frequency bands listed in the hardware specifications for both modules.

Disclaimer

This content is for reference only in IoT solution selection. Carrier spectrum allocations are subject to ongoing optimization. Before project launch, consult the target carrier's official spectrum documentation and the hardware specifications from your IoT module vendor.