Foundational models have shown remarkable potential in natural language processing and computer vision, yet remain in their infancy in wireless communications. While a few efforts have explored image-based modalities such as channel state information (CSI) and frequency spectrograms, foundational models that operate directly on raw IQ data remain largely unexplored. This paper presents, IQFM, the first I/Q signal foundational model for wireless communications. IQFM supporting diverse tasks: modulation classification, angle-of-arrival (AoA), beam prediction, and RF fingerprinting, without heavy preprocessing or handcrafted features. We also introduce a task-aware augmentation strategy that categorizes transformations into core augmentations, such as cyclic time shifting, and task-specific augmentations. This strategy forms the basis for structured, task-dependent representation learning within a contrastive self-supervised learning (SSL) framework. Using this strategy, the lightweight encoder, pre-trained via SSL on over-the-air multi-antenna IQ data, achieves up to 99.67% and 65.45% accuracy on modulation and AoA classification, respectively, using only one labeled sample per class, outperforming supervised baselines by up to 7x and 145x. The model also generalizes to out-of-distribution tasks; when adapted to new tasks using only 500 samples per class and minimal parameter updates via LoRA, the same frozen encoder achieves 94.15% on beam prediction (vs. 89.53% supervised), 50.00% on RML2016a modulation classification (vs. 49.30%), and 96.05% on RF fingerprinting (vs. 96.64%). These results demonstrate the potential of raw IQ-based foundational models as efficient, reusable encoders for multi-task learning in AI-native 6G systems.

Radio signal recognition is a crucial task in both civilian and The application of convolutional neural networks (CNNs) military applications, as accurate and timely identification of to automatic modulation classification (AMC) was introduced unknown signals is an essential part of spectrum management by [8]. Their early works [9, 10] together with the release and electronic warfare. The majority of research in this field of several public datasets [11] initiated a wave of interest in has focused on applying deep learning for modulation classification, DL-based RSR. Recently, several alternative DL approaches leaving the task of signal characterisation as an understudied that adopt recurrent neural networks (RNNs) and hybrid architectures area. This paper addresses this gap by presenting [12] were able to consistently achieve above 90% an approach for tackling radar signal classification and characterisation modulation classification accuracy in relatively high signalto-noise as a multi-task learning (MTL) problem. We propose ratio (SNR) settings. Despite the success of DNNs, the IQ Signal Transformer (IQST) among several reference many recent approaches still rely on handcrafted features to architectures that allow for simultaneous optimisation of pre-process the complex-valued, in-phase and quadrature (IQ) multiple regression and classification tasks. We demonstrate data into image-based representations, such as spectrograms the performance of our proposed MTL model on a synthetic [12], prior to training. These approaches effectively transform radar dataset, while also providing a first-of-its-kind benchmark RSR into an image classification problem, and thus limits the for radar signal characterisation.