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Experimental Validation of SBFD ISAC in an FR3 Distributed SIMO Testbed

Bixing Yan, Kwadwo Mensah Obeng Afrane, Achiel Colpaert, Andre Kokkeler, Sofie Pollin, Yang Miao

TL;DR

This work tackles the challenge of enabling continuous sensing and communication within limited FR3 spectrum by proposing a sub-band full-duplex ISAC framework (SBFD ISAC). It validates the approach on a distributed SIMO testbed using three USRP X410 devices at 6.8 GHz with 20 MHz channels, assigning two subbands for sensing (Zadoff–Chu) and one for QPSK communication, synchronized to a MOCAP ground truth. Experimental results show a sensing velocity resolution of $0.145$ m/s and a BER of $3.63 \times 10^{-3}$ for the communication link under NLoS, with SBFD achieving sensing performance comparable to a multiband benchmark while using only one-third of the spectrum. The findings demonstrate that SBFD enables efficient, continuous ISAC operation and highlight subcarrier allocation as the key determinant of performance trade-offs, informing future adaptive strategies for FR3/6G deployments.

Abstract

Integrated sensing and communication (ISAC) is a key enabler for future radio networks. This paper presents a sub-band full-duplex (SBFD) ISAC system that assigns non-overlapping OFDM subbands to sensing and communication, enabling simultaneous operation with minimal interference. A distributed testbed with three SIMO nodes is implemented using USRP X410 devices operating at 6.8 GHz with 20 MHz bandwidth per channel. A total of 2048 OFDM subcarriers are partitioned into three subbands: two for sensing using Zadoff-Chu sequences and one for communication using QPSK. Each USRP transmits one subband while receiving signals across all three, forming a 1 x 3 SIMO node. Time synchronization is achieved through host-server coordination without external clock distribution. Indoor measurements, validated against MOCAP ground truth, confirm the feasibility of the SBFD ISAC system. The results demonstrate monostatic sensing with a velocity resolution of 0.145 m/s, and communication under NLoS conditions with a BER of 3.63e-3. Compared with a multiband benchmark requiring three times more spectrum, the SBFD configuration achieves comparable velocity estimation accuracy while conserving resources. The sensing and communication performance trade-off is determined by subcarrier allocation strategy rather than mutual interference.

Experimental Validation of SBFD ISAC in an FR3 Distributed SIMO Testbed

TL;DR

This work tackles the challenge of enabling continuous sensing and communication within limited FR3 spectrum by proposing a sub-band full-duplex ISAC framework (SBFD ISAC). It validates the approach on a distributed SIMO testbed using three USRP X410 devices at 6.8 GHz with 20 MHz channels, assigning two subbands for sensing (Zadoff–Chu) and one for QPSK communication, synchronized to a MOCAP ground truth. Experimental results show a sensing velocity resolution of m/s and a BER of for the communication link under NLoS, with SBFD achieving sensing performance comparable to a multiband benchmark while using only one-third of the spectrum. The findings demonstrate that SBFD enables efficient, continuous ISAC operation and highlight subcarrier allocation as the key determinant of performance trade-offs, informing future adaptive strategies for FR3/6G deployments.

Abstract

Integrated sensing and communication (ISAC) is a key enabler for future radio networks. This paper presents a sub-band full-duplex (SBFD) ISAC system that assigns non-overlapping OFDM subbands to sensing and communication, enabling simultaneous operation with minimal interference. A distributed testbed with three SIMO nodes is implemented using USRP X410 devices operating at 6.8 GHz with 20 MHz bandwidth per channel. A total of 2048 OFDM subcarriers are partitioned into three subbands: two for sensing using Zadoff-Chu sequences and one for communication using QPSK. Each USRP transmits one subband while receiving signals across all three, forming a 1 x 3 SIMO node. Time synchronization is achieved through host-server coordination without external clock distribution. Indoor measurements, validated against MOCAP ground truth, confirm the feasibility of the SBFD ISAC system. The results demonstrate monostatic sensing with a velocity resolution of 0.145 m/s, and communication under NLoS conditions with a BER of 3.63e-3. Compared with a multiband benchmark requiring three times more spectrum, the SBFD configuration achieves comparable velocity estimation accuracy while conserving resources. The sensing and communication performance trade-off is determined by subcarrier allocation strategy rather than mutual interference.
Paper Structure (23 sections, 3 equations, 10 figures, 2 tables)

This paper contains 23 sections, 3 equations, 10 figures, 2 tables.

Table of Contents

  1. Introduction
  2. SBFD ISAC System Signal Model
  3. Subcarrier Allocation Strategy Among Distributed Nodes
  4. Transmit Signal Model for Distributed Nodes
  5. Receive Signal Model of Distributed Nodes
  6. SBFD ISAC Testbed Architecture
  7. Hardware Architecture of the Testbed
  8. Software Architecture of the Testbed
  9. Transmit OFDM Signal Implementation in the Testbed
  10. Measurement and Validation Methodology
  11. Experimental Configurations with Benchmark Groups
  12. Measurement Scenario
  13. System setup
  14. Coverage Area Validation
  15. Measurement procedure
  16. ...and 8 more sections

Figures (10)

  • Figure 1: The subband allocation strategy for each USRP
  • Figure 2: Software architecture of the testbed used for the indoor measurements
  • Figure 3: Power spectral density of the combined OFDM signal in SBFD mode, showing three subbands with guard-band separation
  • Figure 4: Measurement scenario for the SBFD ISAC testbed
  • Figure 5: Real measurement set up from the view of the target
  • ...and 5 more figures