Source: learn.sparkfun.com

In LTE + GNSS modules, the real engineering challenge is not simply integrating two radios. The true difficulty is enabling continuous GNSS reception while LTE transmission and reception are occurring simultaneously.

This is what “parallel reception” really means in practice:

Maintaining uninterrupted GNSS satellite signal reception during active LTE operation.

Whether you need it depends entirely on the application.

1. The RF Reality: Why Reception Is the Core Issue

GNSS and LTE operate under vastly different signal conditions:

• GNSS signals arrive at approximately –130 dBm
• LTE transmit power can reach +23 dBm

That is a power difference of more than 150 dB.

Because GNSS signals are extremely weak, even minor leakage from the LTE transmitter into the GNSS front-end can cause:

• Desensitize the GNSS receiver
• Break satellite tracking loops
• Force reacquisition
• Increase TTFF (Time to First Fix)
• Degrade speed and heading estimation

Figure: LTE’s powerful signal is interfering with the weak GNSS receiver

So the true question becomes:

Can the module keep receiving GNSS signals while LTE is actively transmitting?

2. Two Architectural Approaches

2.1. True Parallel GNSS Reception

In modules that support true parallel reception:

• GNSS has a dedicated RF front-end
• Proper RF filtering and isolation are implemented
• LTE transmission does not interrupt GNSS tracking

This means:

• GNSS carrier tracking loops remain locked
• Doppler tracking continues
• No reacquisition is needed after LTE transmission bursts
• Position output remains stable and continuous

Example Modules Supporting Concurrent GNSS Reception

✔ u-blox SARA-R5 Series

• LTE-M / NB-IoT
• Independent GNSS RF path
• Explicit support for concurrent GNSS and LTE operation

✔ u-blox SARA-R52 / LEXI-R52

• Integrated GNSS
• Designed for simultaneous connectivity and positioning

✔ Quectel EC25 / EG25 Series

• LTE Cat-4
• Integrated GNSS engine
• Designed for telematics and continuous tracking applications

Note: Always verify coexistence notes in the hardware design guide, not just the feature list.

2.2. Time-Multiplexed GNSS Reception

In lower-cost designs:

• GNSS reception pauses during LTE transmission
• The RF chain is shared or insufficiently isolated between LTE and GNSS
• GNSS reacquires satellites after LTE activity

This causes:

• Tracking gaps
• Speed noise
• Position jumps
• Increased power consumption
• Reduced accuracy in moving systems

However, this architecture is acceptable when:

• Position updates are infrequent
• Device is mostly stationary
• Power savings outweigh tracking precision

Figure: Parallel vs time-multiplexed GNSS reception architecture

3. Why Parallel GNSS Reception Is Important

3.1. Continuous Tracking in Motion

When GNSS reception is continuous and uninterrupted:

• Velocity estimation remains accurate
• Distance calculation is precise
• Heading remains stable

On the other hand, if GNSS reception pauses every time LTE transmits:

• Tracking loops reset
• Speed becomes noisy
• Distance calculations accumulate error over time

This is critical in:

• Fleet tracking
• Wearable tracking
• Micromobility systems
• Automotive telematics

Figure: Continuous GPS tracking in motion

3.2. Reduced TTFF and Better Sensitivity

When GNSS reception is continuous:

• Satellite ephemeris remains valid
• No reacquisition delay
• Warm-start behavior is preserved

In time-multiplexed systems, repeated interruptions can effectively simulate mini cold-starts, adding unnecessary delays.

Figure:A GPS satellite continuously transmitting signal to Earth.

3.3. Lower Real-World Power Consumption

Although parallel reception modules may seem more complex and power-hungry:

• Reacquisition consumes energy
• Restarting tracking loops costs processing power

Continuous reception often results in lower overall power usage in actively transmitting systems.

Figure: Low-power embedded IoT module running on a coin cell battery

4. When Parallel Reception Is NOT Necessary

Parallel GNSS reception may not provide any meaningful benefit if:

• Position is transmitted every few minutes
• Device remains stationary
• Ultra-low power is the primary goal
• GNSS operates briefly and then sleeps

In such cases, time-multiplexed architectures are perfectly sufficient, and many LPWA IoT sensor nodes fall exactly into this category.

Figure: A stationary IoT node where time-multiplexed GNSS is sufficient

5. Hardware Practices Required for Reliable Parallel Reception

Even if the module supports concurrency, the PCB and board design ultimately determine whether GNSS reception truly remains stable.

5.1 Separate Antennas

Advantages:

• Maximum isolation
• Reduced desensitization
• Improved GNSS SNR (Signal-to-Noise-Ratio)

5.2 Proper RF Filtering

Recommended components and techniques:

• SAW filters in GNSS path
• LTE harmonic suppression
• Proper impedance matching

This is critical because LTE harmonics can overlap the GNSS L1 frequency band, causing direct interference.

5.3 Antenna Placement and Isolation

• Physically separate LTE and GNSS antennas
• Avoid routing LTE Power Amplifier (PA) traces near the GNSS feed line
• Maintain a clean RF ground reference

5.4 Shielding and Ground Integrity

• Solid and continuous ground plane
• Keep GNSS RF trace as short as possible
• Avoid digital noise near the GNSS front-end

5.5 Active GNSS Antenna

An active antenna with an integrated LNA (Low Noise Amplifier):

• Improves margin against LTE leakage
• Maintains better sensitivity in noisy environments

Figure: Separate GNSS and LTE antenna connectors with RF shielding on a single PCB

6. Engineering Decision Framework

Choose parallel GNSS reception when:

• Update rate ≤ 1 second
• Device transmits frequently while moving
• Speed and distance accuracy matter
• Real-time tracking is required

On the other hand, time-multiplexed reception is acceptable when:

• Updates are infrequent
• Device is static
• Lowest BOM (Bill of Materials) cost is the priority

Figure: Parallel GNSS or time-multiplexed, a simple decision framework

Conclusion

Parallel GNSS and LTE reception is fundamentally about protecting continuous GNSS signal reception during LTE activity.

It is not merely a marketing feature; it is an RF architecture decision that directly affects:

• Tracking stability
• Speed accuracy
• Power consumption
• System reliability

For motion-based, real-time connected systems, true parallel GNSS reception is often essential. For low-duty-cycle IoT devices, however, it may be unnecessary.

The critical insight for engineers is this: true parallel reception requires module-level RF architecture support and careful PCB and antenna design to fully realize its benefit.

Facing challenges with GNSS and LTE integration in your embedded modules? Feel free to Contact Us for electronic hardware design, embedded systems, and firmware development services.