5G mmWave n257 Deployment with 800 MHz Carrier Aggregation

5G mmWave n257 Deployment with 800 MHz Carrier Aggregation

Syed Ashwaq Hussain (1), Mohammed Babar Ahmed (2), Mohammed Yahiya Pasha Gulam (3)

Saudi Telecom Company

Abstract – Fifth-generation (5G) millimeter-wave (mmWave) technology operating in the N257 band (26.529.5 GHz) rep- resents a transformative leap in wireless broadband capacity. This paper presents a comprehensive performance evaluation of a live 5G mmWave trial deployment conducted at Site XYZ in a congested city. The trial operated in Non-Standalone (NSA) mode with LTE as the anchor layer, employing 4-component carrier aggregation (4×200 MHz) to achieve 800 MHz of total downlink bandwidth. Theoretical peak throughput calculationsbased on Effective Resource Elements, 64 QAM modulation, 0.95 coding rate, 2-layer digital beamforming, and a 4:1 TDD ratioproject a maximum downlink rate of approximately 4 Gbps per cell. Live test measurements under Line-of-Sight (LOS) conditions recorded peak downlink throughputs of 1509 Mbps at near- point, 1159 Mbps at mid-point, and 944 Mbps at far-point, with corresponding uplink rates of 358 Mbps, 216 Mbps, and 186 Mbps respectively. The paper also details the NSA Secondary Cell Group (SCG) addition strategy with prioritized handoff parameters, Carrier Aggregation (CA) conguration scripts, and practical deployment constraints. Key limitations including CPE Ethernet port bottleneck at 1.5 Gbps, NLOS coverage gaps, and lack of indoor measurement scenarios are documented. The results validate the viability of mmWave 5G as a high- capacity layer for dense urban deployments while highlighting areas requiring further optimization.

Index Terms5G NR; mmWave; N257 band; carrier ag- gregation; Non-Standalone (NSA); throughput; SCG addition; beamforming; TDD; link budget

1. Introduction

   The global proliferation of data-intensive applications including ultra-high-denition video streaming, augment- ed/virtual reality, Industry 4.0 automation, and smart city infrastructurehas placed unprecedented demand on mobile network capacity. The International Telecommunication Union (ITU) denes 5G as a system capable of delivering peak data rates of 20 Gbps in downlink [6], largely achievable through the exploitation of millimeter-wave (mmWave) spectrum bands above 24 GHz.

   Among the key spectrum assets enabling ultra-high- throughput 5G services is the N257 band (26.529.5 GHz), which offers contiguous wideband allocations that are unavail- able in sub-6 GHz spectrum.

   mmWave propagation presents a unique set of challenges: higher free-space path loss, severe attenuation through obsta- cles, sensitivity to atmospheric absorption, and strong direc- tionality that demands precise beam management. These char- acteristics necessitate careful site selection, antenna design, and RF parameter optimization to achieve adequate coverage and throughput.

   This paper documents and analyzes a pilot trial deploy- ment of 5G NR mmWave technology at Site XYZ in, using Huaweis AAU5323 massive MIMO antenna solution. The objectives of the paper were to: (i) validate theoretical peak throughput calculations; (ii) characterize DL/UL performance across near, mid, and far test points in LOS environments;

   (iii) demonstrate the NSA layer strategy and SCG addition mechanism; and (iv) identify deployment-specic challenges for future optimization.

   The paper is structured as follows: Section II reviews background on mmWave 5G. Section III describes site cong- uration and link budget analysis. Section IV presents the NSA layer strategy. Section V details CA conguration. Section VI reports test results. Section VII discusses limitations and future work. Section VIII concludes.

2. Background and Related Work

   mmWave communications in the 5G context have been extensively studied. Rappaport et al. [1] provided foundational propagation measurements in urban environments at 28 GHz and 73 GHz, demonstrating that dense small-cell deployments can overcome high path loss through directional beamforming. Rangan et al. [2] formalized the system-level implications of mmWave channel models, emphasizing the importance of blockage statistics and spatial consistency.

   From a standards perspective, 3GPP Release 15 introduced New Radio (NR) support for FR2 (Frequency Range 2: 24.25 52.6 GHz) [5], dening physical layer proceduresincluding synchronization signal blocks (SSBs), beam management, and numerology with 120 kHz subcarrier spacingthat underpin the trial described in this paper. The NSA architecture dened in Release 15 enables operators to leverage existing LTE infrastructure as the control-plane anchor while adding NR as a data-plane supplement.

   Prior eld trials of mmWave 5G have reported peak through- puts ranging from 1 to 4 Gbps under ideal LOS conditions, with rapid degradation beyond 200300 m in NLOS scenarios. Polese et al. [3] highlight the importance of carrier aggrega- tion across multiple component carriers to achieve aggregate bandwidths approaching 1 GHz. The work presented here contributes operational eld data from an active commercial trial deployment in the Arabian Gulf region, a geography with limited published mmWave measurement datasets.

3. Site Configuration and Theoretical Analysis

   A. Site Selection and Physical Setup

   The site was selected based on multiple RF design criteria: a clear open-area sector with minimal obstruction, sufcient tower load capacity for an additional 4th sector, and existing BBU5900 baseband infrastructure with an available slot for the UBBP card.

   The hardware deployment comprises a Huawei AAU5323 antenna unit operating in the N257 band, co-located with an RRU5909 supporting the LTE 1800 MHz anchor layer. The AAU5323 is mounted at 25 m antenna height with az- imuth 120, providing a designed cell radius of approximately 1500 m under open-area LOS conditions. Table I summarizes the hardware parameters.

   TABLE I

   Site XYZ Hardware Parameters

   Parameter Value

   Vendor Huawei

   City Dammam, Saudi Arabia

   Site Name XYZ

   Frequency Band N257 (26.529.5 GHz) Total Bandwidth 800 MHz (4×200 MHz CA) TX Power 36.5 dBm

   Antenna Height 25 m

   Antenna Type Huawei Massive MIMO (AAU5323) Antenna Gain 29 dBi

   Designed Cell Radius 1500 m

   Sectors 1 (Azimuth 120)

   B. Theoretical Peak Throughput Calculation

   The theoretical single-user downlink peak rate is derived us- ing the parametric formula adapted from 3GPP TS 38.306 [4]:

   TABLE II

   Key mmWave Configuration Parameters

   Parameter Value

   Frequency Band N257 (26.529.5 GHz) Component Carriers 4 × 200 MHz Aggregate Bandwidth 800 MHz

   Subcarrier Spacing 120 kHz TTI Duration 0.125 ms Modulation (Peak) 64 QAM Coding Rate 0.95

   MIMO Layers 2 (Digital Beamforming) DL:UL TDD Ratio 4:1 (DL factor 0.8) IBLER 10%

   Working Mode NSA (LTE Anchor)

   Target Peak DL Rate 4 Gbps

   (SCG) for high-throughput data-plane ofoad. The C-band NR N78 (100 MHz) layer acts as an intermediate SCG tier.

   The SCG addition priority is congured to strongly prefer mmWave attachment when signal conditions are adequate: N257 SCG priority is set to 7 versus N78 priority of 1, ensur- ing UEs within mmWave coverage are aggressively connected to the high-throughput layer. Table III shows the full priority matrix.

   TABLE III

   NSA SCG Frequency Priority Configuration

   RAT Freq. Band SCG Priority Anchor Priority

   NR N78 (3.5 GHz) 1 N/A

   NR N257 (26 GHz) 7 N/A

   LTE L1800 20 MHz N/A 6

   LTE L1800 15 MHz N/A 5

   Reak =

   NRE · Bmod · Rc · NL · DL · NCC · (1 IBLER)

   TTTI

   (1)

   B. SCG Addition Recommended Parameters

   The SCG addition trigger uses Event B1 measurement reporting, where the UE signals the eNB when the NR

   where NRE is the effective resource elements per DL slot

   (15,389 bits), Bmod is the bits per RE for 64 QAM (= 6), Rc is the coding rate (0.95), NL is the number of MIMO layers (2), DL is the DL ratio of TDD frame (0.8 for 4:1), NCC is the number of component carriers (4), IBLER is the initial block error rate (0.10), and TTTI = 0.125 ms.

   Substituting these values into (1) yields a theoretical ag- gregate peak downlink rate of approximately 4 Gbps. Table II summarizes the key conguration parameters.

4. NSA mmWave Layer Strategy and SCG Addition

   A. Layer Strategy Overview

   The trial operates in 5G Non-Standalone (NSA) architec- ture, where LTE 1800 MHz serves as the Master Cell Group (MCG) anchor providing control-plane connectivity, while the NR mmWave N257 layer is added as a Secondary Cell Group

   secondary cell RSRP exceeds a congurable threshold. For the N257 layer, the B1 RSRP threshold (NsaDcB1ThldRsrp) is relaxed from the default 105 dBm to 115 dBm to maximize mmWave SCG addition probability within the coverage foot- print. The B1 Time-to-Trigger is set to 512 ms for connection stability. The SCG DL frequency priority is planned with N78 = 1 and N257 = 6 to enforce mmWave preference.

5. Carrier Aggregation Configuration

   1. Intra-Band CA Architecture

      To achieve 800 MHz aggregate downlink bandwidth, four 200 MHz component carriers are aggregated using intra- band contiguous CA within the N257 band. NR DU cells (NrDuCellId 50, 54, 58, 62) are enabled with both down- link and uplink CA switches (INTRA_BAND_CA_SW and INTRA_BAND_UL_CA_SW).

      The Primary Component Carrier (PCC) serves as the scheduling anchor, with three Secondary Component Carri- ers (SCCs) added using a blind SCC conguration strategy (SCC_BLIND_CONFIG_SW), which avoids measurement gap overhead and accelerates full-bandwidth aggregation. The A2 RSRP threshold is 109 dBm and A5 RSRP threshold is

      105 dBm.

   2. CA Frequency Group Conguration

   The four component carriers are congured as CA fre- quency group CaFreqGroupId = 1 with the following NAR- FCNs: 2055833, 2059165, 2062497, and 2065829, with cor-

   responding SSB positions at 2054825, 2058157, 2061489, and 2064821 respectively. All carriers use 120 kHz subcarrier spacing consistent with FR2 numerology. A representative extract of the radio conguration commands is shown in Listing 1.

   // Enable NRDUCELL CA switch MOD NRDUCELLALGOSWITCH:

   NrDuCellId=50,

   CaAlgoSwitch=INTRA_BAND_CA_SW-1

   &INTRA_BAND_UL_CA_SW-1;

   // Enable SCC blind config MOD NRCELLCAMGMTCONFIG:

   NrCellId=50, CaA2RsrpThld=-109, CaA5RsrpThld2=-105, CaA6Offset=2,

   CaStrategySwitch=SCC_BLIND_CONFIG_SW-1;

   // Configure CA frequency group ADD GNBCAFREQUENCY:

   CaFreqGroupId=1, DlNarfcn=2055833, SsbFreqPos=2054825;

Listing 1. Extract of CA Conguration Commands (NrDuCellId 50)

1. Test Setup and Results

   1. Test Setup

      Field measurements were conducted using a CPE Win device positioned at three representative test locationsnear- point, mid-point, and far-pointalong the azimuth 120 main lobe of Site ZND897s mmWave sector, all under open-area LOS conditions. The transport network employed a 10G PON backhaul via an OLT and PE aggregation node, providing adequate backhaul capacity for mmWave peak throughput tests.

      MAC layer padding tests were rst conducted to charac- terize the maximum MAC-layer throughput per component carrier. Results conrmed that each 200 MHz CC achieves approximately 1 Gbps maximum MAC throughput, aligning with theoretical predictions and validating CA conguration integrity.

   2. DL/UL Point Measurement Results

      Table IV presents the measured DL and UL throughput results at each test point under LOS conditions.

      The near-point DL result of 1509 Mbps represents the maximum throughput achievable by the CPE Win device,

      TABLE IV

      DL and UL Throughput Results LOS Conditions (Site ZND897)

      Test Point	DL Throughput (Mbps)	UL Throughput (Mbps)
      Near	1509	358
      Mid	1159	216
      Far	944	186

      * CPE Ethernet port limits DL to 1.5 Gbps max.

      which is limited by its Ethernet interface to 1.5 Gbps. MAC Padding tests conrm actual air-interface throughput exceeds this ceiling. The UL peak of 358 Mbps is consistent with the 4:1 TDD ratio allocating approximately one-fth of frame resources to the uplink.

      Throughput degrades gracefully with distance in the LOS scenario: DL reduces from 1509 to 944 Mbps (37.4%) from near to far, while UL reduces from 358 to 186 Mbps (48.0%). This degradation is attributable to increasing path loss, reduc- tion in received RSRP, and corresponding MCS adaptation to lower-order constellations to maintain link reliability.

   3. Discussion

   The results conrm that mmWave 5G N257 with 800 MHz CA can deliver multi-gigabit throughput at practical deploy- ment distances in LOS environments. The near-point through- put of 1.5 Gbps with a single 2R CPE terminal, combined with the 4 Gbps theoretical maximum, demonstrates the tech- nologys capacity advantage over sub-6 GHz 5G in dense deployment scenarios.

   The NSA architecture with elevated N257 SCG priority (7 vs. 1 for N78) and relaxed B1 RSRP threshold (115 dBm) demonstrated effective preferential mmWave attachment. The blind SCC conguration strategy minimized CA activation overhead, enabling rapid multi-carrier aggregation without measurement gap delays.

2. Limitations and Future Work

   Several deployment-specic constraints were encountered during the trial:

   • CPE Ethernet Port Bottleneck: The CPE Win devices Ethernet interface imposes a 1.5 Gbps ceiling, preventing measurement of full air-interface capacity. Future trials should use multi-gigabit (10GbE) test equipment to re- move this bottleneck.

   • UE Mobility Limitations: The CPE is designed for stationary operation; signal instability during mobility tests rendered drive-test measurements unreliable. 5G NR mmWave handset terminals with full beam tracking are required to characterize mobility performance.

   • Indoor Measurement Gap: No buildings were located within the sector coverage footprint, preventing character- ization of indoor penetration lossa critical factor where typical building losses of 1530 dB substantially reduce indoor coverage.

   • NLOS Coverage Characterization: NLOS measure- ment locations could not be identied due to device limitations. Dedicated NLOS propagation measurements using directional spectrum analyzers are recommended.

   Future work should include: (i) NLOS and indoor propaga- tion modeling using ray-tracing simulations calibrated against eld measurements; (ii) multi-user MIMO performance eval- uation with beamformed spatial multiplexing; (iii) handover performance assessment between mmWave, C-band, and LTE layers; (iv) capacity and coverage trade-off analysis for dense urban small-cell grid planning; and (v) SA (Standalone) mode activation to evaluate native 5G core network performance.

3. Conclusion

This paper has presented a detailed performance evaluation of a 5G NR mmWave trial deployment at Site ZND97 in Dammam, Saudi Arabia, operating in NSA mode on the N257 band with 4-component carrier aggregation deliver- ing 800 MHz of aggregate bandwidth. Theoretical analysis projects a peak downlink throughput of approximately 4 Gbps per cell, while live eld measurements recorded 1509 Mbps DL and 358 Mbps UL at the near-point under LOS conditions. The NSA SCG addition framework with elevated mmWave priority (N257 = 7) and relaxed B1 RSRP threshold (115 dBm) demonstrated effective preferential mmWave at- tachment. The blind SCC conguration strategy minimized CA activation overhead and enabled rapid multi-carrier aggrega-

tion.

The trial validates mmWave 5G as a viable ultra-high- throughput capacity layer for urban 5G deployments, infras- tructure objectives. The documented limitations provide a clear roadmap for subsequent phases of mmWave network optimiza- tion and expansion. These ndings contribute to the growing body of eld-validated mmWave 5G measurement data and offer practical guidance for network engineers deploying high- frequency 5G installations in the 5G network.

References

1. T. S. Rappaport, S. Sun, R. Mayzus, H. Zhao, Y. Azar, K. Wang, G. N. Wong, J. K. Schulz, M. Samimi, and F. Gutierrez, Millimeter wave mobile communications for 5G cellular: It will work! IEEE Access, vol. 1, pp. 335349, 2013.

2. S. Rangan, T. S. Rappaport, and E. Erkip, Millimeter-wave cellular wireless networks: Potentials and challenges, Proceedings of the IEEE, vol. 102, no. 3, pp. 366385, Mar. 2014.

3. M. Polese, M. Giordani, M. Mezzavilla, S. Rangan, and M. Zorzi, Improved handover through dual connectivity in 5G mmWave mobile networks, IEEE J. Sel. Areas Commun., vol. 35, no. 9, pp. 20692084, Sep. 2017.

4. 3GPP TS 38.306, NR; User Equipment (UE) radio access capabilities, Release 15, 2018.

5. 3GPP TS 38.104, NR; Base Station (BS) radio transmission and reception, Release 15, 2018.

6. ITU-R M.2083-0, IMT Vision Framework and overall objectives of the future development of IMT for 2020 and beyond, Sep. 2015.

7. M. Giordani, M. Polese, A. Roy, D. Castor, and M. Zorzi, A tutorial on beam management for 3GPP NR at mmWave frequencies, IEEE Commun. Surveys Tuts., vol. 21, no. 1, pp. 173196, 2019.

8. Huawei Technologies Co., Ltd., 5G mmWave AAU5323 Product Doc- umentation, Internal Technical Reference, 2022.