NR Max Throughput

Unlike in LTE, estimation of expected max throughput is relatively straightforward. You would estimate LTE max throughput depending on UE category based on well defined table like 36.306 - Table 4.1A-1, but it is not that straightfoward in NR mainly because framestructure, subcarrier scheduling, possibility of partial slot schedule, dmrs configuration etc. One suggested method of max throughput estimation with a certain condition is to use a formula shown below.

NOTE : Even with this formula, it is hard to reflect all the dynamic nature of physical layer scheduling into the formual. So in reality, you would get much lower throughput than what is estimated from this formula. I think it is normal to have lower throughput than what you get from this equation.  

  

<  38.306 - 4.1.2 Supported max data rate for DL/UL >

What you need to notice from this formula is what are the factors affecting the throughput. Just directly reading from the formula, you can list those factors as shown below.

• Number of Carriers (in case of Carrier Aggregation)
• Number of Layers
• Modulation Scheme
• Max Code Rate
• Scheduled OFDM symbols per subframe
• Overhead
• Scaling Factor

NOTE : There are some additional factors that are not explicitely included in the formula (probably can implcitely be reflected), but has very big impact on maximum achievable throughput. Those are listed below :

• TDD UL-DL Pattern
• DMRS Configuration (e.g, DMRS symbol length, Number of Additional DMRS, Configuration Type)
• PUCCH format and CSI/HARQ report mechanism

Table of Contents

• NR Max Throughput
• Introduction
• Summary of the Tutorial
• SA TDD 1CC 100Mhz 4x4 addpos 1
• NSA TDD 1CC 100Mhz 4x4 addpos 1
• Possible Further Improvement

Introduction

5G New Radio (NR) represents a significant evolution in mobile wireless communication, designed to meet the diverse requirements of enhanced mobile broadband, ultra-reliable low-latency communications, and massive machine-type communications. Unlike its predecessor LTE, NR introduces a highly flexible and scalable architecture, enabling dynamic adaptation to various deployment scenarios, frequency bands, and use cases. At the core of NR’s technical advancements are features such as scalable numerology, advanced modulation schemes, flexible frame structures, and support for carrier aggregation and massive MIMO. These innovations allow NR to achieve much higher data rates, lower latency, and improved spectral efficiency. However, this flexibility also introduces complexity in key performance estimation tasks, such as calculating the maximum achievable throughput. While LTE throughput estimation was often straightforward—relying on static UE categories and standardized tables—NR’s dynamic and configurable parameters (including frame structure, subcarrier scheduling granularity, partial slot allocations, and diverse demodulation reference signal (DMRS) configurations) make throughput estimation a more intricate process. Understanding the factors that influence NR throughput and learning how to estimate it under standardized conditions is essential for engineers, researchers, and practitioners who seek to optimize network planning, device development, or performance analysis in real-world 5G environments. This tutorial provides a comprehensive introduction to NR maximum throughput estimation, highlighting the architectural differences from LTE, the mathematical foundations of throughput calculation, and the practical considerations necessitated by NR’s dynamic scheduling and physical layer features.

• Context and Background
  • 5G NR is the global standard for a unified, more capable wireless air interface, supporting a wide array of deployment options, spectrum bands, and connectivity requirements.
  • It is architected to deliver high throughput, ultra-low latency, and reliable connectivity for diverse applications ranging from mobile broadband to industrial IoT.
  • The flexibility of NR’s physical layer—such as variable subcarrier spacing, configurable slot durations, and support for advanced MIMO—directly influences throughput performance and estimation methodologies.
  • Unlike LTE, where maximum throughput was tied to static UE categories and defined tables, NR’s dynamic frame structure and scheduling mechanisms require a more nuanced approach to throughput estimation.
• Relevance and Importance of the Tutorial Topic
  • Accurate estimation of NR maximum throughput is critical for device manufacturers, network operators, and engineers involved in performance benchmarking and network optimization.
  • Understanding the impact of different physical layer parameters—such as the number of carriers, modulation schemes, code rates, and scheduling strategies—enables more effective planning and resource allocation.
  • This topic is particularly relevant for those transitioning from LTE to NR, as it addresses the challenges introduced by the new radio architecture and more complex physical layer configurations.
• Learning Outcomes
  • Gain a comprehensive understanding of the technical and architectural factors that influence maximum throughput in NR.
  • Learn the mathematical approach to estimating NR maximum throughput using standardized formulas and parameters.
  • Recognize the limitations of theoretical throughput estimation and understand the role of real-world scheduling dynamics and overhead.
  • Be able to identify and analyze the key parameters affecting throughput, including carrier aggregation, MIMO layers, modulation, and overhead factors such as DMRS and control signaling.
• Prerequisite Knowledge and Skills
  • Basic understanding of wireless communication concepts, including modulation schemes, coding, and radio resource management.
  • Familiarity with LTE and/or NR physical layer architecture and terminology.
  • Some experience with 3GPP technical specifications (e.g., TS 38.306 for NR, TS 36.306 for LTE) is beneficial but not strictly required.
  • Ability to interpret standard technical diagrams and formulas related to throughput calculation and resource allocation.

Summary of the Tutorial

This tutorial describes test procedures for achieving maximum throughput in both Standalone (SA) and Non-Standalone (NSA) TDD configurations using 1CC, 100 MHz bandwidth, and 4x4 MIMO with DMRS additional position 1. The procedures focus on system configuration, resource allocation visualization, and performance validation steps, primarily using Amarisoft test setups.

• SA TDD 1CC 100Mhz 4x4 addpos 1 Test Procedure:
  • The system is configured for Single Cell Standalone (SA) TDD operation
  • Resource Planning: Prior to testing, visualize the configuration in terms of slot and symbol allocation, and estimate overheads (PBCH, PDCCH, DMRS, etc.) that may impact throughput.
  • Test Execution: Run the throughput test using Amarisoft with the above configuration.
    •   During the test, monitor the 'retx' column; all values should be '0' for optimal performance (indicating no retransmissions and low BLER).
    •   If 'retx' is high, refer to troubleshooting guidelines for BLER issues.
    •   If throughput is still below expectation with 'retx' at 0, verify that the 'txok' column value is high enough; low values could indicate insufficient IP layer data injection.
  • Expected Result: Achieve maximum DL throughput (around 1.7 Gbps) as per system capability.
• NSA TDD 1CC 100Mhz 4x4 addpos 1 Test Procedure:
  •   The system is configured for Single Cell NSA TDD operation (1 LTE cell + 1 NR cell)
    •   Slot pattern and PUCCH/PDSCH configurations are identical to those used in the SA scenario.
  • Resource Planning: As with SA, visualize and estimate slot/symbol allocation and overheads to understand throughput limitations.
  • Test Execution: Perform the throughput test using Amarisoft.
    •   Monitor 'retx' and 'txok' columns as in the SA test, ensuring 'retx' stays at 0 and 'txok' is sufficiently high.
  • Expected Result: Achieve aggregate throughput of ~2 Gbps (1.7 Gbps NR + 0.4 Gbps LTE).
• Possible Further Improvement:
  •   To further increase throughput, set dmrs_add_pos: 0 to reduce DMRS overhead and potentially gain an additional ~10% throughput.
  • Note: Many UE modems may not stably decode PDSCH with only one DMRS symbol in a slot when a large number of OFDM symbols are scheduled. Use this configuration with caution and only if the modem supports stable decoding under these conditions.

SA TDD 1CC 100Mhz 4x4 addpos 1

This is to show the configuration for Single Cell SA TDD maximum throughput. Around 1.7 Gbps was achieved with 4x4 MIMO and DMRS addpos 1.

This test was done by this configuration : gnb-sa-max-tput_100Mhz_4x4_addpos_1_pucch3.cfg.  Highlights of the configuration is as shown below. Highlights of the configuration is as shown below. Here NR_BANDWIDTH is set to 100Mhz, N_ANTENNA_DL is set to 4 (i.e, 4x4 MIMO).

#define NR_BANDWIDTH         100  // NR cell bandwidth #define N_ANTENNA_DL         4   // Values: 1 (SISO), 2 (MIMO 2x2), 4 (MIMO 4x4) #define N_ANTENNA_UL         1   // Values: 1, 2, 4 #define NR_LONG_PUCCH_FORMAT 3   // Values: 2, 3, 4         pattern1: {         period: 5, /* in ms */         dl_slots: 8,         dl_symbols: /* 6 */ 2,         ul_slots: 1,         ul_symbols: 2,       },           pucch3: {           bpsk: false,           additional_dmrs: false,           freq_hopping: true,           n_prb: 1,           simultaneous_harq_ack_csi: true,           max_code_rate: 0.25,         },       pdsch: {       mapping_type: "typeA",       dmrs_add_pos: 1,       dmrs_type: 1,       dmrs_max_len: 1,       /* k0 delay in slots from DCI to PDSCH: automatic setting */       /* k1 delay in slots from PDSCH to PUCCH/PUSCH ACK/NACK: automatic setting */       mcs_table: "qam256",       rar_mcs: 2,       si_mcs: 9,       /* If defined, force the PDSCH MCS for all UEs. Otherwise it is computed        * based on DL channel quality estimation */       /* mcs: 24, */     },

When you want to achieve high throughput, it is strongly recommended to visualize your configuration in terms of resource allocation and possible scheduling and have some rough estimate first. It would not be easy to consider every possible details affecting the throughput in the illustration, but it would be helpful if you can visualize at least slot and symbol allocation and mark possible overhead in terms of throughput. (e.g, PBCH, PDCCH, DMRS etc)  

Following is the output from test setup in Amarisoft. ( NOTE : When you do the test in your setup. The first thing to make it sure is that you should get all '0' in 'retx' column. If you have any high numbers in this column indicating high BLER, refer to this note for troubleshoot. If you still don't get the expected max throughput, then check the number of in txok column. If you have the value much lower than this even with retx = 0, it imply that IP layer is not pushing high enough data into radio stack.)

 

 

NSA TDD 1CC 100Mhz 4x4 addpos 1

This is to show the configuration for Single Cell NSA TDD maximum throughput. Around 2 Gbps(1.7Gb in NR + 0.4Gb in LTE) was achieved with 4x4 MIMO and DMRS addpos 1. NOTE : The single cell NSA in this context mean 1 LTE cell + 1 NR cell.

This test was done by this configuration : gnb-nsa-max-tput_100Mhz_4x4_addpos_1_pucch3.cfg.  Highlights of the configuration is as shown below. Here NR_BANDWIDTH is set to 100Mhz, N_ANTENNA_DL is set to 4 (i.e, 4x4 MIMO).

#define NR_BANDWIDTH         100  // NR cell bandwidth #define N_ANTENNA_DL         4   // Values: 1 (SISO), 2 (MIMO 2x2), 4 (MIMO 4x4) #define N_ANTENNA_UL         1   // Values: 1, 2, 4 #define NR_LONG_PUCCH_FORMAT 3   // Values: 2, 3, 4         pattern1: {         period: 5, /* in ms */         dl_slots: 8,         dl_symbols: 2,         ul_slots: 1,         ul_symbols: 2,       },           pucch3: {           bpsk: false,           additional_dmrs: false,           freq_hopping: true,           n_prb: 1,           simultaneous_harq_ack_csi: true,           max_code_rate: 0.25,         },       pdsch: {       mapping_type: "typeA",       dmrs_add_pos: 1,       dmrs_type: 1,       dmrs_max_len: 1,       /* k0 delay in slots from DCI to PDSCH: automatic setting */       /* k1 delay in slots from PDSCH to PUCCH/PUSCH ACK/NACK: automatic setting */       mcs_table: "qam256",       rar_mcs: 2,       si_mcs: 9,       /* If defined, force the PDSCH MCS for all UEs. Otherwise it is computed        * based on DL channel quality estimation */       /* mcs: 24, */     },

 

When you want to achieve high throughput, it is strongly recommended to visualize your configuration in terms of resource allocation and possible scheduling and have some rough estimate first. It would not be easy to consider every possible details affecting the throughput in the illustration, but it would be helpful if you can visualize at least slot and symbol allocation and mark possible overhead in terms of throughput. (e.g, PBCH, PDCCH, DMRS etc)  

 

Following is the output from test setup in Amarisoft. (NOTE : When you do the test in your setup. The first thing to make it sure is that you should get all '0' in 'retx' column. If you have any high numbers in this column indicating high BLER, refer to this note for troubleshoot. If you still don't get the expected max throughput, then check the number of in txok column. If you have the value much lower than this even with retx = 0, it imply that IP layer is not pushing high enough data into radio stack.)

 

 

Possible Further Improvement

 

One possible improvement you can make would be to set dmrs_add_pos: 0. Then you would get less overhead by DMRS as illutrated below. It would give you around 10% of increased throughput. (NOTE : Based on our experience (and it is understandable), many of the UE side modem may have difficulties decoding PDSCH stably with only one DMRS symbol in one slot with large number of OFDM symbols scheduled. Therefore, we would not guarantee about this configuration in real operation, but you may try it if you think your modem can stably decode PDSCH in this configuration)