Sub-6 GHz 5G: Advantages and Disadvantages

This page explores the pros and cons of Sub-6 GHz 5G networks compared to mmWave 5G. It outlines the benefits and drawbacks of using Sub-6 GHz frequencies for 5G deployment.

What is Sub-6 GHz 5G?

Introduction: Wireless carriers have been rolling out 5G networks since 2019, adhering to 3GPP Release 15 and later specifications.

The primary use cases for 5G technology are:

• eMBB (enhanced Mobile Broadband): Focuses on faster data rates and improved spectral efficiency.
• mMTC (massive Machine Type Communications): Designed for long battery life and high device density.
• URLLC (Ultra-Reliable Low Latency Communications): Emphasizes low latency and high reliability.

These three use cases are collectively known as the “5G Vision.”

Figure: A typical 5G network consisting of a gNB (gNodeB or Base Station), 5G small cells, and 5G mobile phones.

5G networks can be deployed in two main modes:

• Non-Standalone (NSA): Operates in conjunction with an existing LTE network. LTE handles control signaling, while 5G NR manages the data transmission.
• Standalone (SA): Functions independently of LTE. Both control and data signaling are handled by the 5G system.

The 5G NR system utilizes two primary frequency ranges:

• FR2: Employs mmWave frequencies (the “high band”).
• FR1: Uses sub-6 GHz frequencies, encompassing “low band” and “mid band” frequencies.

Benefits of Sub-6 GHz 5G

Here are the key advantages of Sub-6 GHz 5G:

• Lower Path Loss: Transmitted signals experience less path loss compared to mmWave frequencies.
• Better Penetration: Sub-6 GHz waves penetrate obstacles more effectively than mmWave, making them suitable for dense urban environments.
• Robust Signals with MIMO: Sub-6 GHz networks often employ MIMO (Multiple-Input Multiple-Output) at both transmitters and receivers. This leads to more robust signals and higher Signal-to-Noise Ratios (SNRs), resulting in faster data rates.
• Favorable Signal Reflections: Longer wavelengths in sub-6 GHz signals experience more reflections than mmWave. This can be advantageous when using MIMO, improving signal quality and coverage.
• Optimized Wireless Link via CSI: Channel State Information (CSI) helps maintain an optimized wireless link. Parameters like scattering, fading, path loss, and blocking are more predictable and repeatable within the sub-6 GHz frequency range. This provides a more favorable environment for signal propagation.

Drawbacks of Sub-6 GHz 5G

The main disadvantages of Sub-6 GHz 5G include:

• Complexity and Cost: Sub-6 GHz 5G often involves multiple bands, various standards, Carrier Aggregation (CA), and dual connectivity (LTE/5G). This complexity can increase implementation costs and make the overall system more expensive.