5G SA Carrier Aggregation Validation: DL 2FDD +3TDD and UL 1FDD+1TDD Configuratio

5G SA Carrier Aggregation Validation: DL 2FDD +3TDD and UL 1FDD+1TDD Configuratio

Syed Ashwaq Hussain

independent researcher

Abstract – This paper presents the results and technical analysis of a 5G Standalone (SA) 5-Component Carrier Aggregation (5CC CA) field trial conducted in a 5G network environment. The trial demonstrated simultaneous Downlink (DL) aggregation across five carriers (2 FDD + 3 TDD), achieving a peak PDSCH throughput of 2060 Mbps, and Uplink (UL) aggregation across two carriers (1 FDD + 1 TDD), achieving a peak PUSCH throughput of 212 Mbps. The trial was performed using Nokia AirScale Radio hardware (AQQS 64T64R, AEHC 64T64R, AHEGC 4T4R) with 5G Core (5GC) connected via dual AMF interfaces, operating on Release 23R4 software. The test device utilized a Qualcomm Snapdragon X75 (SDX-75) modem with defined UE bandwidth class restrictions. This work discusses spectrum configuration across NR bands n1, n3, n41, and n77, UE capability constraints, SSB coverage quality, and per-carrier PDSCH/PUSCH throughput breakdown. The findings confirm RAN network readiness with existing hardware and highlight the criticality of UE ecosystem maturity for full throughput realization.

Keywords – 5G Standalone; Carrier Aggregation; 5CC CA; NR-CA; FR1; PDSCH; PUSCH; mMIMO; Qualcomm SDX-75; NR Bands; Multi-Carrier Aggregation; 5G SA; RAN.

1. INTRODUCTION

   The evolution of 5G New Radio (NR) technology has brought unprecedented demands for high-throughput mobile broad- band, driven by the growth of video streaming, cloud gaming, and industrial IoT applications. Carrier Aggregation (CA), originally introduced in LTE, has been significantly advanced in 5G NR to support simultaneous transmission and reception across multiple component carriers (CC), thus multiplying the effective radio bandwidth available to a User Equipment (UE) [1].

   In Standalone 5G (SA) mode where the 5G Radio Ac- cess Network (RAN) connects directly to the 5G Core (5GC) without LTE anchor carrier aggregation capabilities are fully decoupled from the Non-Standalone (NSA) architec- tures constraints. This enables the exploitation of a hetero- geneous spectrum portfolio comprising both Frequency Di- vision Duplex (FDD) and Time Division Duplex (TDD) car- riers across the FR1 frequency range [2].

   Multi-band aggregation combining FDD carriers (n1, n3) which provide broad coverage through lower frequencies with TDD carriers (n41, n77) which contribute high capac- ity through wider bandwidths presents a complex but highly effective strategy for maximizing spectral efficiency and user throughput.

   This paper documents a field trial of 5G SA 5CC DL CA (2 FDD + 3 TDD) and 2CC UL CA (1 FDD + 1 TDD),

   measuring peak per-carrier and aggregated PDSCH/PUSCH throughputs in a live network scenario. The trial equipment, software version, spectrum configuration, UE modem restric- tions, and signal quality observations are presented and ana- lyzed.

   The remainder of the paper is organized as follows: Sec-tion

   II covers related work; Section III describes the system architecture and trial setup; Section IV presents the spec- trum and NR-ARFCN configuration; Section V discusses UE bandwidth restrictions; Section VI presents the SSB cover-

   age and signal quality results; Section VII presents the DL throughput results; Section VIII presents the UL throughput results; Section IX provides a discussion; and Section X con- cludes the paper.

2. RELATED WORK

   Carrier Aggregation in 5G NR has been studied extensively since the early releases of 3GPP specifications. 3GPP Re- lease 15 defined the foundational CA framework for NR, while Releases 16 and 17 extended support for higher-order CA combinations and cross-band scenarios [3].

   Prior work on NR-CA field trials has primarily focused on NSA architectures with LTE anchors or sub-6 GHz SA de- ployments with up to 4 CCs [4]. Studies on mmWave CA above FR2 have demonstrated extremely high peak rates but with limited coverage, making FR1 aggregation a more prac- tical approach for wide-area deployments [5].

   The combination of FDD and TDD carriers in a single CA group (known as asymmetric CA) introduces schedul- ing complexity due to differing UL/DL timing structures and UE capability classes [6]. Nokia has previously documented high-order CA achievements in NSA deployments [11]; how- ever, SA-mode 5CC CA combining multiple FDD and TDD bands simultaneously represents a more advanced capability. The Qualcomm Snapdragon X75 modem is among the first commercially available platforms supporting 5G Release 17 features including 5CC CA, AI-enhanced modem processing, and expanded bandwidth class support [8]. Understanding its UE capability restrictions is essential for realistic throughput benchmarking.

3. SYSTEM ARCHITECTURE AND TRIAL SETUP

   1. Network Configuration

      The trial was conducted on a single sector of a 5G SA net- work operating on Release 23R4 software (SW). The net-

      work connected to a 5G Core (5GC) with dual AMF inter-B. NR-ARFCN Reference Values

      faces (AMF-1 and AMF-2) and an NMS element manage- ment system. The BTS managed five NR cells across five component carriers simultaneously.

   2. Radio Hardware

      The sector was equipped with three types of Nokia AirScale radio modules, as summarized in Table 1:

      Table 1: Radio Hardware Configuration per Sector

      Module	Config	Bands Served
      AQQS	64T64R	n77 (3700 MHz), n77 (3800 MHz)
      AEHC	64T64R	n41 (2600 MHz)
      AHEGC	4T4R	n1 (2100 MHz), n3 (1800 MHz)

      The AQQS and AEHC radios support massive MIMO (mMIMO) with 64 transmit and 64 receive chains, while the

      The NR Absolute Radio Frequency Channel Numbers (NR- ARFCNs) and the corresponding global synchronization channel numbers (GSCNs) for each carrier are listed in Ta- ble 3.

      Table 3: NR-ARFCN and GSCN per Carrier

      Band	Freq (MHz)	GSCN	NR-ARFCN
      n1	2140 (UL: 2135.05)	5338	427010
      n3	1870 (UL: 1865.05)	4663	373010
      n41	2540.01	6351	508110
      n77	3750	8020	650016
      n77	3850.02	8089	656640

      The two n77 carriers at 3700 MHz and 3800 MHz are served by separate AQQS 64T64R radio units, enabling in- dependent mMIMO beam management per carrier.

      AHEGC serves the FDD bands with a 4T4R configuration.C. Uplink Carrier Configuration

      Baseband processing was handled by a combination of ABIO

      (two modules) and ASIB units.

   3. Test Device

      The test UE was a Qualcomm Mobile Test Platform (MTP) equipped with the Snapdragon X75 (SDX-75) modem. The measurement tool used for RF logging and analysis was the

      For Uplink 2CC CA, only two carriers were aggregated: n3 (FDD, 20 MHz) as the PCell and n77 (TDD, 100 MHz) as SCell1, as the UEs ULCA capability was limited to the F+T combination.

      V. UE BANDWIDTH RESTRICTIONS (QUALCOMM SDX-75)

      Accuver XCAL field tool. Ookla Speedtest was used for end-A. Downlink CA Bandwidth Classes

      to-end throughput benchmarking.

   4. Test Conditions

   The test was conducted during a Minimization of Drive Test- ing (MDT) period under controlled conditions to ensure ex- clusivity of radio resources. This allowed measurement of peak achievable throughput without inter-user interference effects.

4. SPECTRUM CONFIGURATION AND NR-ARFCN

1. Band Allocation

   Five NR bands were used in the trial, spanning FR1 FDD and TDD sub-6 GHz spectrum. The carrier role assignment (PCell and SCells) is listed in Table 2.

   Role	Band	Duplex	Freq (MHz)	BW (MHz)
   PCell	n3	FDD	1800	20
   SCell1	n77	TDD	3700	100
   SCell2	n41	TDD	2600	20
   SCell3	n77	TDD	3800	100
   SCell4	n1	FDD	2100	20

   Table 2: Carrier Configuration DL 5CC CA

   The Qualcomm SDX-75 modem supports a wide range of DL CA combinations (F+T, 2F+T, F+2T, 2F+2T, F+3T, 3F+T,

   2F+3T). For the 2F+3T combination applicable in this trial, the maximum UE-supported bandwidth under the SDX-75 is:

   BWUE,max = 40 MHz (FDD) + 220 MHz (TDD) (1)

   However, due to the FDD carrier bandwidths (n3: 20 MHz, n1: 20 MHz = 40 MHz total FDD) and TDD carrier band- widths, the effective per-band UE working bandwidths ap- plied in this trial are constrained as shown in Table 4.

   Table 4: UE Bandwidth Restriction per Band (DL 5CC)

   Band	Avail. BW	Config. BW	UE Working BW
   n3	20 MHz	20 MHz	5 MHz
   n1	20 MHz	20 MHz	10 MHz
   n41	100 MHz	20 MHz	20 MHz
   n77	100 MHz	100 MHz	100 MHz
   n77	100 MHz	100 MHz	100 MHz
   Total	340 MHz	260 MHz	235 MHz

   The UE-imposed restriction reduces the effective working bandwidth from 260 MHz (configured) to 235 MHz. Notably,

   n3 is limited to 5 MHz and n1 to 10 MHz by the UEs band- width part (BWP) selection behavior. Despite these restric-

   VII. DOWNLINK THROUGHPUT RESULTS

   tions, the UE successfully establishes the 5CC CA session,A. RF Measurement Summary

   confirming SDX-75s 5CC CA capability.

2. Uplink CA Bandwidth Classes

For UL CA, the SDX-75 supports the F+T combination with a maximum of 40 MHz (FDD) + 100 MHz (TDD). The UL 2CC configuration uses n3 (20 MHz FDD) and n77 (100 MHz TDD), totaling 120 MHz aggregated UL bandwidth with no UE restriction applied (Table 5).

Table 5: UE Bandwidth Configuration (UL 2CC)

VI. SSB COVERAGE AND SIGNAL QUALITY

1. Downlink SSB Measurements

   Synchronization Signal Block (SSB) coverage was evaluated using SS-RSRP measurements across all five carriers during the DL 5CC CA session. The PCell (n3) provided the ref- erence signal, with SS-RSRP of 63.23 dBm, reflecting the coverage advantage of the 1800 MHz band. The n41 SCell2

   The RF measurement summary from the Accuver XCAL tool captured per-carrier PDSCH throughput, SINR, SS-RSRP, and serving beam metrics during the DL 5CC CA session. Table 7 summarizes the parameters of the physical layer:

   Table 7: DL RF Measurement Summary (5CC CA)

   Parameter	PCell	SC1	SC2	SC3	SC4
   Band	n3	n77	n41	n77	n1
   Duplex	FDD	TDD	TDD	TDD	FDD
   BW (MHz)	5	100	20	100	10
   PCI	113	189	330	189	113
   SS-RSRP(dBm)	65.45	75.62	79.34	85.95	80.32
   SS-RSRQ(dB)	10.34	10.34	10.34	10.55	10.88
   SINR (dB)	33.36	38.14	24.83	39.96	9.90
   DL TP (Mbps)	42.20	782.33	139.54	680.94	105.05

   The n77 TDD carriers (SCell1 and SCell3) dominate the DL throughput contribution, collectively delivering over 1460 Mbps due to their 100 MHz bandwidth and 64T64R mMIMO capability. The n41 SCell2, configured at 20 MHz, contributed approximately 140 Mbps despite its narrower bandwidth.

   exhibited the weakest signal at 87.16 dBm, consistent with B. Peak Aggregated PDSCH Throughput

   the 2600 MHz propagation characteristics and the narrower (20 MHz) configured bandwidth.

   Table 6: SS-RSRP Summary DL 5CC CA

   Carrier Role	Band	NR-ARFCN	SS-RSRP (dBm)
   PCell	n3	373970	63.23
   SCell1	n77	650016	70.91
   SCell2	n41	508110	87.16
   SCell3	n77	656640	76.46
   SCell4	n1	427970	85.24

   The dual n77 carriers showed SS-RSRP values of 70.91 dBm (SCell1 at 3700 MHz) and 76.46 dBm (SCell3 at 3800 MHz), confirming adequate signal quality for 100 MHz mMIMO operation. All five carriers maintained stable NR- ARFCNs throughout the measurement period, validating ra- dio link stability.

2. Uplink SSB Measurements

For the UL 2CC CA session, the two carriers (n3 PCell and n77 SCell1) exhibited SS-RSRP values of 66.91 dBm and

The peak DL 5CC aggregated PDSCH throughput was 2060.903 Mbps ( 2.06 Gbps), measured at 100 ms inter- vals using the Accuver XCAL tool. The per-carrier and total throughput time-series data are summarized in Table 8.

Table 8: DL 5CC PDSCH Throughput Top Samples (Mbps)

The Ookla Speedtest confirmed a DL speed of 1,731 Mbps at the application layer, which is consistent with the PDSCH- layer peak considering PDCP and transport protocol over- head. This represents one of the highest recorded 5G SA DL throughput values in a live FR1 network deployment in the MEA region using a commercial-grade UE modem.

50.63 dBm respectively. The n77 SCell1 showed a higherC. Per-Carrier Throughput Distribution

SS-RSRP in the UL context due to the strong serving beam

alignment from the 64T64R AQQS mMIMO unit, demon- strating effective beam management capability.

The two 100 MHz n77 TDD carriers (SCell1 and SCell3) together contributed approximately 85% of the total DL

throughput, underscoring the critical role of wide TDD carri- ers in multi-CC aggregation scenarios. The FDD carriers (n3 PCell, n1 SCell4), constrained by UE bandwidth restrictions to 5 MHz and 10 MHz respectively, contributed modestly but are essential for PCell anchor stability and SCell3 SSB cov- erage assistance.

1. UPLINK THROUGHPUT RESULTS

   1. UL 2CC CA RF Measurements

      The UL 2CC CA session involved n3 (FDD PCell) and n77 (TDD SCell1). Table 9 summarizes the RF measurement pa- rameters:

      Table 9: UL RF Measurement Summary (2CC CA)

      Parameter	PCell (n3)	SCell1 (n77)	SCell2
      Band	n3	n77	n77
      Duplex	FDD	TDD	TDD
      BW (MHz)	20	100
      PCI	113	189	189
      SS-RSRP (dBm)	65.95	51.34	50.37
      SS-RSRQ (dB)	10.33	10.34	10.32
      SINR (dB)	28.73	39.39	39.11
      UL TP (Mbps)	104.63	122.07

   2. Peak Aggregated PUSCH Throughput

   The peak UL 2CC aggregated PUSCH throughput was

   212.567 Mbps, measured at 100 ms intervals. Table 10 pro- vides the per-carrier and combined UL PUSCH throughput for the top samples:

   Table 10: UL 2CC PUSCH Throughput Top Samples (Mbps)

   Timestamp	PCell (n3)	SCell1 (n77)	Total
   04:13:29.4	93.068	119.499	212.567
   04:13:30.8	93.071	116.353	209.424
   04:13:27.9	92.970	116.335	209.305
   04:13:28.7	93.186	115.137	208.323
   04:13:30.5	92.370	114.594	206.964

   The Ookla Speedtest confirmed an UL throughput of 187 Mbps at the application layer. The n77 TDD carrier con- tributed the larger share of UL throughput (approximately 56%), enabled by its wider 100 MHz bandwidth and the mMIMO radios uplink beamforming capabilities.

2. DISCUSSION

   1. Significance of 5CC CA in 5G SA

      The achievement of 5CC CA in a live 5G SA network without LTE anchor represents a significant milestone. In NSA deployments, UL aggregation typically relies on an LTE carrier as the anchor, constraining SA deployments to

      fewer UL CCs. The 2CC UL CA in SA mode demonstrated here proves that the 5GC architecture can efficiently manage multi-carrier UL scheduling without LTE assistance.

   2. UE Ecosystem Limitations

      A critical observation from this trial is the role of UE modem bandwidth restrictions in constraining achievable throughput. The SDX-75s application of 5 MHz BWP on n3 and 10 MHz on n1 despite both bands being configured at 20 MHz reduces the theoretical maximum DL throughput. With full UE bandwidth class support on all five carriers (i.e., 260 MHz total configured bandwidth), the expected peak throughput would approximately double:

      TPexpected 2 × 2060 Mbps 4.1 Gbps (2)

      This projection is consistent with theoretical 5CC CA ca- pacity estimates for 235260 MHz of aggregated FR1 band- width with 256-QAM and 64T64R mMIMO.

   3. mMIMO Impact

      The 64T64R AQQS and AEHC radios enabled spatial mul- tiplexing and beamforming gains that are evident in the high SINR values recorded on the n77 carriers (3839 dB) and the corresponding high per-carrier throughput (¿860 Mbps per n77 CC). The FDD 4T4R AHEGC unit, by contrast, showed lower SINR (9.9 dB on n1) due to its more limited antenna array.

   4. 5G Core Readiness

   The dual AMF interface configuration and 5GC operation confirmed full SA protocol stack functionality during the trial. No handover events or CA release incidents were recorded during the peak throughput measurement windows, indicating stable 5CC CA session management by the 5GC.

3. CONCLUSION

This paper presented a comprehensive field trial of 5G SA 5- Component Carrier Aggregation, achieving peak DL PDSCH throughput of 2060 Mbps (DL: 2FDD + 3TDD) and peak UL PUSCH throughput of 212 Mbps (UL: 1FDD + 1TDD) in a FR1 network.

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