UCODEN

UCODEN · Underwater Cooperative Detection Networks

Jiajie Xu

Postdoctoral Research Fellow & Lab Manager
Communication Theory Laboratory, KAUST

I build deployable systems and theory for ocean networks that both communicate and sense — from space-air-ground-sea integrated coverage to multimodal underwater links and cooperative detection.

EmailGoogle ScholarPublications

Jiajie Xu

About

Biography

Jiajie Xu is a Postdoctoral Research Fellow and Lab Manager in the Communication Theory Laboratory at King Abdullah University of Science and Technology (KAUST), led by Prof. Mohamed-Slim Alouini. He received his Ph.D. in Electrical and Computer Engineering from KAUST in 2023 and was retained by the group as a postdoctoral researcher upon graduation; in 2023 he was a visiting scholar at the University of Oxford with Prof. Justin P. Coon.

His research develops deployable systems and theory for space-air-ground-sea integrated networks (SAGSIN) and underwater cooperative detection: stochastic-geometry coverage modeling, robust multimodal (optical/acoustic/mmWave) hybrid communication, and robust localization under multiple unknown parameters. He introduced the concept of Underwater COllaborative DEtection Networks (UCODENs), which gives this site its name, and supervises master's and Ph.D. students at KAUST and collaborating institutions, including the University of Oxford and Tsinghua University.

Research

Networks that communicate and sense

Three mutually reinforcing lines of work address the network-architecture, link-transmission and detection-application bottlenecks of wide-area ocean communication and sensing — each validated on real deployments.

01

SAGSIN coverage modeling and wide-area link extension

  • 15 → 500 kmreliable surface coverage
  • 1.5 km → full depthunderwater coverage
  • 6papers · TWC, IoTJ, WCM
  • First unified stochastic-geometry coverage framework spanning onshore stations, surface nodes, tethered balloons, high-altitude platforms, satellites and underwater acoustic networks.
  • Reliable surface coverage extended from ~15 km (onshore) to ~500 km (HAP); underwater coverage depth from ~1.5 km to full ocean depth with a vertical K-tier + horizontal SOFAR three-hop design.
  • 6 papers in IEEE TWC, IoTJ and Wireless Communications.

02

Robust multimodal hybrid communication

  • −20%transmit power with offset pointing
  • ≈14 dBlower SNR at BER 10⁻²
  • 99.10%FSO–mmWave availability
  • “Passive robustness outperforms active tracking”: a deliberate receiver offset for underwater optical links cuts the required transmit power by ~20%.
  • Generalized code–frequency–space index modulation: ~2× energy efficiency and ~14 dB lower SNR at BER 10⁻².
  • Parallel FSO–mmWave backhaul on a 1.2-km Red Sea link: 99.10% availability (FSO alone 81.90%, mmWave alone 90.99%).

03

Robust localization and networked cooperative detection

  • 14×faster than SDP solvers
  • 50nodes in the outdoor testbed
  • 5papers · TVT, IoTJ, TWC, TIM
  • Shifted-Gamma model of composite ranging noise with closed-form parameters and a tighter Cramér–Rao bound than the Gaussian model.
  • Weighted-RSS/GTRS estimator ~14× faster than SDP methods (0.09 s vs 1.24 s), and a rank-one SDP formulation without accuracy loss.
  • The UCODENs concept and the hybrid SDP–SOCP algorithm CTUP, validated on a 50-node outdoor testbed.

In the field

Systems deployed and tested

IEEE 802.11ax maritime mesh network, KAUST Beacon Bay
IEEE 802.11ax maritime mesh network, KAUST Beacon Bay17–92 Mbps links for surface vessels and buoys at about 90% lower cost than satellite links, with underwater cameras and water-quality sensors on the buoys.
FSO + 60 GHz mmWave backhaul, KAUST ↔ MACC
FSO + 60 GHz mmWave backhaul, KAUST ↔ MACCHybrid optical/mmWave links behind a Terragraph community Wi-Fi for about 3,000 residents; coverage rose from 80% to 100%.
  • Shushah Island coral-reef monitoring100 ha in the northern Red Sea; cross-medium RF/acoustic monitoring cut the data-collection cycle from monthly to 10 seconds.
  • Low-cost FSO terminal1 Gbps over 1 km at USD 2–4 K per unit; an airborne variant is prepared for UAV and HAPS trials.
  • Fire EyeIntelligent firefighting navigation system, selected for Global Grad Show 2022 in Dubai.

Funding

Projects

  • Integrated FSO/RF Testbed for Space-Air-Ground-Sea CommunicationsKAUST · 2024–2026 · Co-Investigator / Lead R&D Investigator
    USD 816 K
  • Delay-Tolerant Networking for Underwater and Maritime Wireless CommunicationsKAUST / NEOM · 2023–2025 · Co-Investigator
    USD 949 K
  • Local Design and Development of Low-Cost RF-over-FSOC SystemsKAUST · 2024–2026 · Co-Investigator, sub-project lead
    USD 705 K
  • Maritime Mesh Network and Underwater Hybrid Wireless Communication SystemKAUST · 2024–2025 · Project lead
    USD 225 K
  • Towards a Fully Connected Smart OceanKAUST / NEOM · 2023–2024 · Co-Investigator
    USD 136 K
  • Connect the Unconnected: Optical/mmWave Wireless CommunicationKAUST with Meta, Google and CST · 2022–2023 · Sub-project leader

Earlier: key member of four NSFC General Program projects on underwater cooperative localization, acoustic communication and multi-robot cooperative detection (2016–2024).

Publications

Selected papers

  1. IEEE TWC · 2023

    Space-Air-Ground-Sea Integrated Networks: Modeling and Coverage Analysis

    Jiajie Xu, Mustafa Kishk#, and Mohamed-Slim Alouini

    IEEE Transactions on Wireless Communications, vol. 22, no. 9, pp. 6298–6313, Sept. 2023.

  2. IEEE OJ-COMS · 2025

    UCODENs: Underwater COllaborative DEtection Networks

    Jiajie Xu#, Mustafa Kishk, Xabier Irigoien, and Mohamed-Slim Alouini

    IEEE Open Journal of the Communications Society, vol. 6, pp. 77–89, 2025.

  3. IEEE IoTJ · 2026

    A Shifted-Gamma Noise Model for Practical Underwater Acoustic Target Localization

    Jiajie Xu, Heyou Liu#, and Mohamed-Slim Alouini

    IEEE Internet of Things Journal, vol. 13, no. 4, pp. 7067–7082, Feb. 2026.

  4. IEEE TWC · 2024

    Performance Analysis and Optimal Resource Allocation for Large Scale Joint Sensing and Communication

    Jiajie Xu, Mustafa Kishk#, Justin P. Coon, and Mohamed-Slim Alouini

    IEEE Transactions on Wireless Communications, vol. 23, no. 10, pp. 14350–14364, Oct. 2024.

  5. IEEE WCM · 2025

    Implementation of an IEEE 802.11ax-Based Maritime Mesh Network in the Red Sea

    Yingquan Li, Jiajie Xu#, Narek Khachatrian, and Mohamed-Slim Alouini

    IEEE Wireless Communications, vol. 32, no. 5, pp. 212–218, Oct. 2025.

  6. IEEE OJ-COMS · 2025

    Enhancing Wireless Backhaul Networks with Parallel FSO-mmWave Systems: Experimental Analysis and Availability Assessment

    Fahad S. Alqurashi, Jiajie Xu#, Luis Barreiro Goiriz, and Mohamed-Slim Alouini

    IEEE Open Journal of the Communications Society, vol. 6, pp. 10219–10228, 2025.

Full list of publications →

Recognition

Honors and awards

2026

URSI GASS Young Scientist Award — International Union of Radio Science, triennial, for scientists under 35

  1. 2024Honorary Certificate of Appreciation, IEEE Communications Society Student Competition
  2. 2023Academic Excellence Award, KAUST (second consecutive year; 1 of 225)
  3. 2023Second Place, Student Poster Contest, IEEE SusTech 2023, Portland
  4. 2022Academic Excellence Award, KAUST
  5. 2022Global Grad Show 2022, Dubai — Fire Eye selected among 100 of 1,000+ entries
  6. 2020–2023KAUST Full Scholarship for doctoral study

Invited talks

  • URSI GASS 2026, Poland — Young Scientist Award talk (Aug. 2026)
  • Reef Futures 2024, Riviera Maya, Mexico — “Wireless-Enabled Reef Restoration” (Dec. 2024)
  • IEEE SusTech 2023, Portland, USA — three-hop UWAC based on the SOFAR plane (Apr. 2023)
  • EuCNC & 6G Summit 2022, Grenoble, France — coverage of integrated networks for large-scale ocean applications
  • Invited seminars: Beijing Institute of Technology; Northwestern Polytechnical University; Shenzhen University of Advanced Technology

Service

  • Guest Editor, npj Wireless Technology (Nature Portfolio) — “Underwater Wireless Communication and Networking”
  • Guest Editor, Electronics — “Towards IoT in Space-Air-Ground-Sea Integrated Networks”
  • TPC member: IEEE INFOCOM 2025 workshop and poster session, IEEE/CIC ICCC 2025, IWCMC 2025, IEEE ICCT 2024
  • Author of the “Towards a Fully Connected Smart Ocean” report for NEOM

Mentoring

Supervises or co-supervises master's and Ph.D. students at KAUST, Oxford, Tsinghua and NPU — eight students to date, with 11 student-led papers in leading journals as sole corresponding author. Lab Manager of the Communication Theory Laboratory, coordinating equipment, experiments and partners including NEOM, CST, Meta, Google and Saudi Aramco.

In the media

Contact

Get in touch

Questions about collaboration, students or the systems above are welcome.

jiajie.xu.1@kaust.edu.sa

Send an emailGoogle Scholar

Building 1, Office 3133, KAUST, Thuwal 23955-6900, Saudi Arabia