Post-Doctoral Research Visit F/M Modern Grant-Free Access Techniques for Cellular Networks (Theory and Experimentation)

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Contract type : Fixed-term contract

Level of qualifications required : PhD or equivalent

Fonction : Post-Doctoral Research Visit

About the research centre or Inria department

The Inria Saclay-Île-de-France Research Centre was established in 2008. It has developed as part of the Saclay site in partnership with Paris-Saclay University and with the Institut Polytechnique de Paris .

The centre has 40 project teams , 32 of which operate jointly with Paris-Saclay University and the Institut Polytechnique de Paris; Its activities occupy over 600 people, scientists and research and innovation support staff, including 44 different nationalities.

Context

This post-doctoral position is part of the PEPR Future Networks, and its PERSEUS project. PERSEUS focuses on the technologies, processing and optimization of next-generation cellular cell-free networks. This includes the development of robust physical and MAC layers and the proofs of concept for the practical assessment of the performance of selected algorithms.

The position will be based at Inria Saclay, with expected collaboration with other sites and partners. The start and end dates are flexible, subject to administrative constraints, and the contract is for 12 months.

Assignment

The proposed position will focus on the development of grant-free access techniques for IoT applications.

One common communication scenario in IoT applications is massive machine-type communications (mMTC), where a large number of devices transmit sporadic, small packets. In traditional cellular systems, each device is allocated orthogonal resources prior to uplink transmission via a grant mechanism. However, this allocation requires signaling on control channels, which can exceed the data payload size and lead to inefficient resource use. Consequently, grant-free methods [1] that eliminate or reduce control traffic are well suited for these scenarios. Removing coordination introduces non-orthogonality, resulting in the superposition of signals from some or all devices.

A recent family of random access protocols—sometimes called "modern random access"—aims to address and even exploit this phenomenon. The IRSA protocols (Irregular Repetition Slotted ALOHA) [2,3,4] use Successive Interference Cancellation (SIC) and represent one form of grant-free technique, but they can also operate with any packet transmission scheme. Adapting these methods for grant-free mMTC in cellular networks is therefore of prime interest and the main objective of this position.

Main activities

The initial research direction in this post-doctoral position is to study variants of modern random access, incorporating realistic physical-layer features and methods (e.g., [5]), including cell-free systems.

Our main objectives are to enhance performance and practicality in cellular networks. IRSA-based protocols can operate with any modulation scheme, including existing transmission techniques, and do not necessarily require NOMA features such as advanced multi-user detection. However, they can benefit from NOMA methods that improve SIC.

We are particularly interested in improving the selection of transmission opportunities (e.g., using precomputed sequences), possibly constructed with machine learning techniques. We could also consider lightweight node synchronization to reduce signal superposition.
An important aspect is that we plan to do actual experiments on the CortexLab platform in INSA/Inria Lyon using available software.

[1] Muhammad Basit Shahab, Rana Abbas, Mahyar Shirvanimoghaddam, and Sarah J. Johnson. "Grant-free non-orthogonal multiple access for iot: A survey.IEEE Communications Surveys & Tutorials", ,2020.
[2] Gianluigi Liva. "Graph-Based Analysis and Optimization of Contention Resolution Diversity Slotted ALOHA." IEEE Transactions on Communications, 59(2):477–487, 2011.
[3] Clazzer, Federico, Andrea Munari, Gianluigi Liva, Francisco Lazaro, Cedomir Stefanovic, and Petar Popovski. "From 5G to 6G: Has the time for modern random access come?." arXiv preprint arXiv:1903.03063 (2019).
[4] "Modern Random Access for Grant-Free Cellular Networks,"" C. Adjih, Tutorial, https://indo-french-seminar-6g.github.io/slides/Modern_Random_Access_for_Grant-Free_Cellular_Networks--Cedric-Adjih.pdf
[5] Saeed Alsabbagh, Cédric Adjih, Amine Adouane, and Nadjib Aitsaadi. "Optimization of Irregular Repetition Slotted ALOHA with Imperfect SIC in 5G CIoT". IEEE International Conference on Communi-cations (ICC) 2025.

Skills

- Ph. D. in Computer Science, Telecommunications, Electrical Engineering, or a related field.
- Excellent programming skills (e.g., Python) and good knowledge of wmachine learning frameworks.
- Strong background in communication theory, random access, machine learning, or artificial intelligence.
- Experience in programming SDR (Software Defined Radio) is a plus.

Benefits package

  • Subsidized meals
  • Partial reimbursement of public transport costs
  • Leave: 7 weeks of annual leave + 10 extra days off due to RTT (statutory reduction in working hours) + possibility of exceptional leave (sick children, moving home, etc.)
  • Possibility of teleworking (after 6 months of employment) and flexible organization of working hours
  • Professional equipment available (videoconferencing, loan of computer equipment, etc.)
  • Social, cultural and sports events and activities
  • Access to vocational training
  • Social security coverage

Remuneration

2788€ gross/month