5G NR SSB ARFCN Calculator

Introduction

The 5G NR SSB ARFCN Calculator is a comprehensive web-based tool designed for telecommunications engineers, network planners, and RF specialists working with 5G New Radio (NR) networks. This calculator performs precise conversions and calculations related to Synchronization Signal Blocks (SSB) and Absolute Radio Frequency Channel Numbers (ARFCN) based on 3GPP specifications.

What is SSB?

The Synchronization Signal Block (SSB) is a fundamental component in 5G NR that contains:

• Primary Synchronization Signal (PSS)

• Secondary Synchronization Signal (SSS)

• Physical Broadcast Channel (PBCH)

SSB enables initial cell search, cell identification, and time/frequency synchronization for User Equipment (UE).

What is ARFCN?

Absolute Radio Frequency Channel Number (ARFCN) is a standardized numbering scheme used to designate specific radio frequency channels in 5G NR networks. It provides a unique identifier for each channel across different frequency ranges.

Tool Description

This calculator provides three powerful calculation modes:

1. From Point A (ARFCN)

Calculate SSB ARFCN and frequency using:

• Point A ARFCN (reference point at the lower edge of the channel)

• Offset to Point A (in Resource Blocks)

• K_SSB (subcarrier offset)

• Subcarrier Spacing (SCS)

2. From Center Frequency

Calculate SSB parameters from:

• Center frequency ARFCN

• Channel bandwidth

• SSB offset from center

• Subcarrier Spacing

3. Direct SSB Calculation

Bidirectional conversion between:

• SSB Frequency ↔ SSB ARFCN

Key Features

✅ Accurate 3GPP Compliance - Based on TS 38.104 and TS 38.211 specifications

✅ Multiple Calculation Modes - Three different input methods for flexibility

✅ Frequency Range Support - Covers FR1 (410 MHz - 7125 MHz) and FR2 (24.25 GHz - 52.6 GHz)

✅ Visual Frequency Domain Representation - Interactive graphical visualization with annotated values

✅ Real-time Calculations - Instant results with verification

✅ Comprehensive Results - Displays all intermediate calculations and conversions

✅ Formula Display - Shows step-by-step calculation process

✅ Error Validation - Built-in verification and error checking

Understanding the Concepts

Point A

Point A is a reference point defined in 3GPP specifications that represents the lower edge of the channel bandwidth. It serves as the starting point for calculating other frequency parameters.

offsetToPointA

This parameter defines the offset in Resource Blocks (RBs) from Point A to the center of the SSB. One RB consists of 12 subcarriers.

K_SSB

K_SSB is the subcarrier offset within the Resource Block where the SSB is located. It provides fine-grained frequency positioning within an RB.

Subcarrier Spacing (SCS)

The frequency spacing between adjacent subcarriers. 5G NR supports multiple SCS values:

• 15 kHz - Used in FR1 for wide area coverage

• 30 kHz - Common in FR1 for balanced coverage and capacity

• 60 kHz - Used in FR1 for high-speed scenarios

• 120 kHz - Used in FR2 (mmWave)

• 240 kHz - Used in FR2 for ultra-high bandwidth

Frequency Ranges

• FR1 (Frequency Range 1): 410 MHz to 7125 MHz (sub-6 GHz)

  • FR1 Low: 0 - 3000 MHz (ARFCN: 0 - 599999)

  • FR1 High: 3000 - 24250 MHz (ARFCN: 600000 - 2016666)

• FR2 (Frequency Range 2): 24250 MHz to 52600 MHz (mmWave)

  • ARFCN: 2016667 - 3279165

🧮 Formulas and Calculations

1. ARFCN to Frequency Conversion

The fundamental formula for converting NR-ARFCN to frequency (3GPP TS 38.104):

F_REF = F_REF_OFFS + (ΔF_Global × (N_REF - N_REF_OFFS)) / 1000

Where:

• F_REF = Reference frequency in MHz

• N_REF = NR-ARFCN value

• F_REF_OFFS = Reference frequency offset (MHz)

• N_REF_OFFS = Reference ARFCN offset

• ΔF_Global = Global frequency raster step size (kHz)

Parameters by Frequency Range:

Range	Frequency	ΔF_Global	N_REF_OFFS	F_REF_OFFS
FR1 Low	0 - 3000 MHz	5 kHz	0	0 MHz
FR1 High	3000 - 24250 MHz	15 kHz	600000	3000 MHz
FR2	24250 - 100000 MHz	60 kHz	2016667	24250.08 MHz

2. Frequency to ARFCN Conversion

N_REF = N_REF_OFFS + round((F_REF - F_REF_OFFS) × 1000 / ΔF_Global)

3. SSB Frequency from Point A

F_SSB = F_PointA + ((offsetToPointA × 12 + K_SSB) × SCS) / 1000

Where:

• F_SSB = SSB center frequency (MHz)

• F_PointA = Point A frequency (MHz)

• offsetToPointA = Offset in Resource Blocks from Point A

• K_SSB = Subcarrier offset (0-11)

• SCS = Subcarrier spacing (kHz)

• 12 = Number of subcarriers per Resource Block

4. Point A from Center Frequency

F_PointA = F_Center - (Channel_BW / 2)

Where:

• F_Center = Center frequency of the channel (MHz)

• Channel_BW = Channel bandwidth (MHz)

5. SSB Bandwidth

The SSB occupies exactly 20 Resource Blocks (240 subcarriers):

SSB_BW = 240 × SCS / 1000 (MHz)

Examples:

• SCS = 15 kHz: SSB_BW = 3.6 MHz

• SCS = 30 kHz: SSB_BW = 7.2 MHz

• SCS = 120 kHz: SSB_BW = 28.8 MHz

User Guide

Getting Started

1. Open the Calculator

   • Load the HTML file in any modern web browser

   • The interface will display three calculation modes as tabs

2. Select Calculation Mode

   • Click on the appropriate tab based on your available input parameters

   • Each mode has different input fields

Mode 1: From Point A

Use Case: When you know the Point A ARFCN and offset parameters.

Steps:

1. Select Frequency Range (FR1 or FR2)

2. Enter Point A ARFCN (e.g., 428000)

3. Enter Offset to Point A in RBs (e.g., 13)

4. Enter K_SSB value (typically 0)

5. Select Subcarrier Spacing (e.g., 30 kHz)

6. Click "Calculate SSB ARFCN"

Results Displayed:

• Point A ARFCN and Frequency

• Offset to Point A (RBs)

• K_SSB value

• Subcarrier Spacing

• SSB Frequency (calculated)

• SSB ARFCN (calculated)

• Verified SSB Frequency

• Frequency Error (should be minimal)

Mode 2: From Center Frequency

Use Case: When you know the channel center frequency and bandwidth.

Steps:

1. Select Frequency Range (FR1 or FR2)

2. Enter Center Frequency ARFCN (e.g., 428400)

3. Select Channel Bandwidth (e.g., 20 MHz)

4. Enter SSB Offset from center in RBs (e.g., 13)

5. Select Subcarrier Spacing

6. Click "Calculate SSB ARFCN"

Results Displayed:

• Center ARFCN and Frequency

• Channel Bandwidth

• Point A ARFCN and Frequency (calculated)

• SSB Offset

• SSB Frequency (calculated)

• SSB ARFCN (calculated)

Mode 3: Direct SSB Calculation

Use Case: Simple conversion between SSB frequency and ARFCN.

Steps:

1. Enter SSB Frequency in MHz (e.g., 2140.08) OR

2. Enter SSB ARFCN (if converting from ARFCN to frequency)

3. Click "Convert"

Results Displayed:

• SSB Frequency or ARFCN (depending on input)

• Frequency Range classification

• Verification values

💡 Practical Examples

Example 1: N78 Band (3.5 GHz) Calculation

Scenario: Calculate SSB for n78 band with 100 MHz channel

Inputs:

• Point A ARFCN: 632628 (corresponds to ~3450 MHz)

• Offset to Point A: 68 RBs

• K_SSB: 0

• SCS: 30 kHz

Calculation:

Step 1: Point A Frequency F_PointA = 3000 + (15 × (632628 - 600000)) / 1000 F_PointA = 3489.42 MHz Step 2: SSB Frequency F_SSB = 3489.42 + ((68 × 12 + 0) × 30) / 1000 F_SSB = 3489.42 + 24.48 F_SSB = 3513.90 MHz Step 3: SSB ARFCN N_SSB = 600000 + round((3513.90 - 3000) × 1000 / 15) N_SSB = 634260

Example 2: N41 Band (2.5 GHz) TDD Configuration

Scenario: Calculate SSB for n41 band with 40 MHz channel

Inputs:

• Center Frequency ARFCN: 520000 (2600 MHz)

• Channel Bandwidth: 40 MHz

• SSB Offset: 7 RBs

• SCS: 30 kHz

Calculation:

Step 1: Center Frequency F_Center = 3000 + (15 × (520000 - 600000)) / 1000 F_Center = 2600.00 MHz Step 2: Point A Frequency F_PointA = 2600.00 - (40 / 2) F_PointA = 2580.00 MHz Step 3: SSB Frequency F_SSB = 2580.00 + ((7 × 12) × 30) / 1000 F_SSB = 2580.00 + 2.52 F_SSB = 2582.52 MHz Step 4: SSB ARFCN N_SSB = 600000 + round((2582.52 - 3000) × 1000 / 15) N_SSB = 572168

Example 3: N257 Band (28 GHz) mmWave

Scenario: Calculate SSB for FR2 mmWave band

Inputs:

• Point A ARFCN: 2054166 (corresponds to ~26250 MHz)

• Offset to Point A: 20 RBs

• K_SSB: 0

• SCS: 120 kHz

Calculation:

Step 1: Point A Frequency F_PointA = 24250.08 + (60 × (2054166 - 2016667)) / 1000 F_PointA = 26499.02 MHz Step 2: SSB Frequency F_SSB = 26499.02 + ((20 × 12) × 120) / 1000 F_SSB = 26499.02 + 28.80 F_SSB = 26527.82 MHz Step 3: SSB ARFCN N_SSB = 2016667 + round((26527.82 - 24250.08) × 1000 / 60) N_SSB = 2054629

Example 4: Direct Frequency to ARFCN Conversion

Scenario: Convert a known SSB frequency to ARFCN

Input: SSB Frequency = 1805.04 MHz

Calculation:

Since 1805.04 MHz is in FR1 Low range (0-3000 MHz): ΔF_Global = 5 kHz N_REF_OFFS = 0 F_REF_OFFS = 0 MHz N_SSB = 0 + round((1805.04 - 0) × 1000 / 5) N_SSB = 0 + round(361008) N_SSB = 361008

References:

• TS 38.104: https://www.3gpp.org/ftp/Specs/archive/38_series/38.104/

• TS 38.211: https://www.3gpp.org/ftp/Specs/archive/38_series/38.211/

• 5G NR Frequency Bands: https://www.3gpp.org/technologies/keywords-acronyms/103-nr-5g-bands

• Sharetechnote - 5G/NR: https://www.sharetechnote.com/html/5G/5G_Index.html

• Techplayon - 5G NR: https://www.techplayon.com/5g-nr-arfcn-and-frequency-conversion/

• 3GPP ARFCN Calculator: https://www.sqimway.com/nr_refA.php

• 5G NR Calculators: https://5g-tools.com/