LITE: Lightweight Channel Gain Estimation with Reduced X-Haul CSI Signaling in O-RAN David Góez ∗ , Marco Piazzola † , Giulia Costa † Achiel Colpaert ‡ Rodney Martinez Alonso § Esra Aycan Beyazıt ∗ Nina Slamnik-Kriještorac ∗ , Johann M. Marquez-Barja ∗ , Miguel Camelo Botero ∗ ∗ University of Antwerp - imec, IDLab, Belgium † Spindox Labs SRL, Italy ‡ imec, Kapeldreef 75, 3001 Leuven, Belgium
arXiv:2604.08458v1 [cs.NI] 9 Apr 2026
§ ESAT, KULEUVEN, Leuven, Belgium
Abstract—Cell-Free Massive Multiple-Input Multiple-Output (CF-MaMIMO) in Open Radio Access Network (O-RAN) promises high spectral efficiency but is limited by frequent Channel State Information (CSI) exchanges, which strain fronthaul/midhaul/backhaul (X-haul) bandwidth and exceed the capabilities of existing approaches relying on uncompressed CSI or heavy predictors. To overcome these constraints, we propose LITE, a lightweight pipeline combining a 1-D convolutional Autoencoder (AE) at the O-RAN Distributed Unit (O-DU) with a Squeeze-and-Excitation (SE)-enhanced Bidirectional Long Short-Term Memory (BiLSTM) predictor at the Near-RealTime RAN Intelligent Controller (Near-RT-RIC), enabling shorthorizon trajectory-unaware forecasting under strict transport and processing budgets. LITE applies 50% CSI compression and an asymmetric SE-BiLSTM, reducing model complexity by 83.39% while improving accuracy by 5% relative to a baseline BiLSTM. With compression-aware training, the Lightweight Intelligent Trajectory Estimator (LITE) incurs only 6% accuracy loss versus the BiLSTM baseline, outperforming independent and end-to-end strategies. A TensorRT-optimized implementation achieves 147k Queries per Second (QPS), a 4.6x throughput gain. These results demonstrate that LITE delivers X-haul-efficient, low-latency, and deployment-ready channel-gain prediction compatible with O-RAN splits. Index Terms—Channel Estimation, 5G-NR, OFDM, Deep Learning, Neural Attention, Neural Network Acceleration.
I. I NTRODUCTION S wireless connectivity demand continues to surge, nextgeneration networks must deliver high spectral efficiency, robust mobility support, and uniform quality of experience [1]. CF-MaMIMO has emerged as a promising architecture by combining massive Multiple-Input Multiple-Output (MIMO) array gains with distributed coverage [2], jointly serving all users across shared time–frequency resources. By removing cell borders, CF-MaMIMO mitigates inter-cell interference and improves rate fairness, with reported spectral-efficiency gains up to 95% [3]. Despite its potential, scaling CF-MaMIMO presents practical challenges. Computational and coordination overheads
A
This work is supported by the 6G-BRICKS project, which has received funding from the European Union’s Horizon Europe program under Grant Agreement No 101096954 and by the Flemish Government under the “Onderzoeksprogramma Artificiële Intelligentie (AI) Vlaanderen” program. The work of Rodney Martinez Alonso is supported by the Research Foundation–Flanders (FWO) under Grant 1211926N.
grow with the number of Access Points (APs) and User Equipments (UEs), while frequent transport of high-dimensional CSI over the X-haul can exceed realistic bandwidth limits [4]. User-centric clustering and scheduling strategies have been proposed to mitigate these constraints [5], [4], [6], yet they often rely on quasi-static assumptions and fail to fully account for dynamic mobility, causing performance degradation when trajectories are unknown [7]. Recent works have explored short-term channel-gain prediction from CSI evolution rather than explicit spatial coordinates [8], but these methods either use uncompressed CSI, imposing excessive transport load, or rely on computationally heavy predictors unsuitable for realtime O-RAN deployment. The O-RAN architecture offers a flexible and open framework for deploying data-driven control in CF-MaMIMO, leveraging disaggregated processing and standardized interfaces [9]. However, its distributed nature intensifies X-haul limitations: frequent CSI transport or measurement reporting can overload midhaul links. Prior studies investigated functional split optimization [10] and lightweight CSI compression [11], [12], yet the combined impact of compression and predictive modeling on short-horizon channel-gain forecasting remains insufficiently characterized. To address these gaps, we introduce LITE, an end-to-end pipeline for trajectory-unaware channel-gain prediction in CF-MaMIMO under O-RAN constraints. LITE integrates a compact 1-D convolutional AE at the O-DU for CSI compression with an asymmetric, SE-enhanced BiLSTM predictor at the Near-RT-RIC. This architecture is designed to lower transport overhead and computational complexity while enabling accurate short-horizon channel prediction without requiring explicit trajectory information. Compared with existing symmetric BiLSTM-based approaches, LITE provides a more efficient model structure and supports real-time inference within O-RAN processing constraints. The remainder of the paper is structured as follows. Section II details the LITE system architecture. Section III presents the CSI compression and prediction algorithms. Section IV reports experimental results, and Section V concludes the paper and outlines directions for future work.
Fig. 1. Overview of the LITE system architecture, illustrating the four processing layers
II. LITE A RCHITECTURE As a first step toward realizing LITE, a compact system architecture is designed and illustrated in Fig. 1. The framework operates across a CF-MaMIMO deployment and an O-RAN Near-RT-RIC environment while maintaining full compatibility with existing O-RAN interfaces. No modifications are introduced to the APs or O-RAN Radio Units (O-RUs), ensuring seamless integration with standard RAN processing pipelines. The architecture comprises the fololwing four tightly coupled processing layers: CF-MaMIMO Radio Access Layer: Uplink signals transmitted by user devices are received by a distributed array of APs, from which standard pilot-based estimation yields full complex-valued CSI following the O-RAN 7.2x functional split. As shown in [8], the resulting tensor of the channel can be represented as: H(t) ∈ CNAP ×Nant ×Nsb ,
(1)
For a flat fading channel, this can be further reduced to a per-AP large-scale channel-gain vector via antenna–subcarrier averaging: β(t) ∈ RNAP . (2) To ensure a uniform temporal structure, the sequence β(t) is reorganized into a fixed-size window representation: S ∈ RNAP ×Z ,
(3)
where Z denotes the temporal window length, corresponding to the number of consecutive CSI snapshots {β(t − Z + 1), . . . , β(t)} stacked along the time dimension. This representation serves as the canonical input to the LITE processing chain, while the raw tensors H(t) remain accessible for validation and reference. O-DU Processing Layer: At the O-DU, the harmonized representation S is normalized and passed to a Deep Neural Network (DNN)-based AE that learns a compact latent encoding. This generates a low-dimensional representation L(t) satisfying |L| ≪ |H|, enabling efficient transport while preserving the temporal and spatial characteristics necessary for prediction.
Midhaul Transport Layer: The latent representation is forwarded to the Near-RT-RIC via the E2 Interface (E2) interface. The sharp reduction in dimensionality alleviates midhaul bandwidth consumption and aligns with the O-RAN disaggregated processing paradigm. Near-RT-RIC Execution Layer: Within the RAN Intelligent Controller (RIC), the latent representation is decoded to reconstruct a high-resolution sequence suitable for temporal analysis. A prediction module then processes this reconstructed sequence to forecast short-horizon channel dynamics relevant for downstream Radio Resource Management (RRM) functions such as scheduling or beamforming. The RIC-native Application (xApp) includes: • CSI Decompression (LITE-Decompress) • Temporal Dynamics Modeling • Short-Horizon CSI Prediction • RIC Output Adaptation The processing chain thus maps raw CSI measurements H(t), locally estimated at the radio access layer, to future channel-state predictions consumed by RIC-hosted control functions. The harmonized temporal sequences S form the stable input domain, and the predicted channel states form the actionable output. Realizing this End-to-End (E2E) functionality requires jointly optimized learning modules that operate under strict dimensionality and accuracy constraints. A DNN-based encoder produces a compact representation for efficient transport, a decoder reconstructs a high-resolution feature space required for reliable temporal modeling, and a predictor processes this reconstructed sequence using architectures trained on the full dataset. This design ensures that compression reduces only transport overhead, without compromising predictive capability. The encoder, decoder, and predictor must therefore satisfy stringent Key Performance Indicators (KPIs), including high compression efficiency, high reconstruction fidelity, and robust prediction accuracy under aggressive compression. Together, these components constitute the core of the LITE E2E learning model. III. CSI COMPRESSION AND CHANNEL GAIN PREDICTION Fig. 2 introduces the E2E Deep Learning (DL) architecture empowering LITE that jointly optimizes CSI compres-
AP
1...8 [t+1...19]
NAP Dimensional Sequential Input Layer AP
SE-->BiLSTM_layer-->FC
(SE) Squeeze & Excitation
NAP Dimensional BiLSTM Layer
NAP Dimensional Sequential Output
Fully Connected Layer
Dropout Layer
AP
1 .
..
1 .
AP1...8 [t+2...20]
.. A
P
AP
8
8
Z equals 20 steps
(SE) Squeeze & Excitation
Fig. 2. Detailed LITE DL architecture showing the symmetric 1-D convolutional AE and the SE-enhanced BiLSTM predictor. Optional SE blocks are illustrated at intermediate and output stages for comparison
sion and trajectory-unaware channel-gain forecasting under strict Near-RT-RIC constraints. Unlike prior work, our design combines (i) a convolutional AE tailored for temporal CSI sequences and (ii) a lightweight BiLSTM predictor augmented with SE attention, achieving substantial compression while preserving predictive accuracy. A. Autoencoder for CSI Compression NAP ×Nant ×Nsc
X-haul transport of raw CSI tensors H(t) ∈ C constitutes a major scalability bottleneck. To mitigate this, LITE learns a compact latent representation of per-AP channel-gain sequences using a DNN-based AE, as such architectures have demonstrated strong performance in radio signal processing tasks [13], [14], [15]. Specifically, the AE maps aggregated CSI windows: S ∈ RNAP ×W
(4)
to a lower-dimensional latent representation: L(t) ∈ RNAP ×Z ,
Z ≪ W,
(5)
where S aggregates per-AP large-scale channel gains over fixed-length temporal windows. The proposed AE adopts a lightweight symmetric 1-D convolutional design. As shown in Table I, the encoder consists of five strided Conv1d layers that progressively reduce the temporal dimension while increasing feature depth, mapping an input of shape [B, 1, 152] to a latent representation of size [B, 15, 5] through successive stride-2 temporal downsampling. ReLU activations are used in all intermediate layers, while the latent layer is linear. The decoder mirrors the encoder using ConvTranspose1d layers to restore the original temporal resolution, reconstructing Ŝ ∈ R[B,1,152] . The AE design achieves an approximate 2× reduction in representation size, i.e., a 50% compression ratio, by compressing the input from 152 to 75 real-valued features. This operating point provides a practical trade-off between X-haul bandwidth reduction and reconstruction fidelity, as supported by prior work [12]. It halves the CSI payload exchanged between the O-DU and the Near-RT-RIC while preserving dominant temporal correlations and large-scale fading characteristics relevant for downstream prediction. Fixing the compression ratio further enables a controlled analysis of
TABLE I A RCHITECTURE OF THE SYMMETRIC 1-D CONVOLUTIONAL AE USED FOR CSI COMPRESSION , INCLUDING ENCODER AND DECODER LAYER CONFIGURATIONS , KERNEL SIZES , STRIDES , AND ACTIVATION FUNCTIONS
Stage E1 E2 E3 E4 E5 D1 D2 D3 D4 D5
Type Conv1d Conv1d Conv1d Conv1d Conv1d ConvT1d ConvT1d ConvT1d ConvT1d ConvT1d
Channels 1 → 64 64 → 512 512 → 256 256 → 128 128 → 15 15 → 128 128 → 256 256 → 512 512 → 64 64 → 1
Kernel 5 3 3 3 3 3 3 3 3 5
Stride 2 2 2 2 2 2 2 2 2 2
Activation ReLU ReLU ReLU ReLU Linear ReLU ReLU ReLU ReLU Linear
dataset augmentation and trajectory diversity, without introducing additional architectural degrees of freedom, as will be shown in Section IV. B. Lightweight Attention-Based Predictor Trajectory-unaware forecasting must capture non-linear temporal dependencies and inter-AP coupling without relying on explicit position information. Although Transformer variants were considered, their quadratic sequence complexity and memory footprint are ill-suited to Near-RT-RIC constraints. LITE therefore adopts a BiLSTM [16] backbone, which has shown strong accuracy–efficiency trade-offs for CF-MaMIMO channel prediction [8]. Bidirectional processing leverages past and future context to limit error accumulation in single-step, short-horizon prediction, and naturally supports multi-AP joint modelling. To reduce computational load, we employ lightweight and asymmetric BiLSTM configurations that decrease the hiddenstate dimensionality of the forward/backward paths while maintaining stable accuracy. To further strengthen feature selectivity, a SE block [17] is inserted before the recurrent layers, performing channel-wise reweighting of AP features. This early recalibration dampens noisy or redundant inputs and enables smaller recurrent layers without compromising temporal modelling. Alternative placements were explored, such as after the BiLSTM and the regression head, and found to be less effective at preserving temporal dependencies. The adopted placement best balances robustness and efficiency. This architectural decision is validated in Section IV. C. End-to-End Integration and Training The LITE pipeline is implemented as a modular yet tightly coupled workflow that spans the O-DU and Near-RT RIC, integrating four stages: compression → midhaul transport → decompression → prediction. This design ensures that CSI is compressed at the edge before transport, reconstructed at the RIC, and then consumed by the predictor without introducing distribution mismatches. Achieving this requires careful alignment between the latent representation learned by the autoencoder and the temporal dependencies modeled by the predictor.
To address this, we explored three complementary training strategies: 1) Independent Training: The autoencoder and predictor are trained separately on their respective objectives. This approach simplifies optimization and stabilizes convergence, but risks a domain gap because the predictor learns from raw sequences while inference uses reconstructed ones. 2) Compression-Aware Training: Here, the autoencoder is trained first and frozen, and the predictor is trained on decompressed sequences. This strategy adapts the predictor to compression artifacts without altering the encoder–decoder weights, striking a balance between modularity and robustness. It proved most effective for maintaining prediction accuracy under aggressive compression. 3) End-to-End (Joint) Training: Both modules are pipelined and trained simultaneously. While conceptually appealing for global optimization, this approach exhibited instability due to conflicting gradients. The reconstruction objective favors smooth latent codes, whereas the forecasting task benefits from preserving fine-grained temporal variations. This tension led to suboptimal latent representations and degraded prediction accuracy, as will be shown in Section IV. From a system perspective, compression-aware training was adopted for deployment because it offers predictable behavior, modular retraining capability, and resilience to X-haul constraints. This design also aligns with O-RAN principles: the encoder runs at the O-DU to minimize transport overhead, while the decoder and SE-BiLSTM predictor can be executed as a containerized xApp within the Near-RT-RIC, ensuring portability and providing higher computing capacity compared to the O-DU. Together, these choices enable LITE to deliver X-haul-efficient, trajectory-unaware forecasting without compromising integration stability or real-time performance. IV. P ERFORMANCE E VALUATION R ESULTS In this section, we present the performance evaluation of the LITE framework, covering its individual components (AE and SE-BiLSTM) as well as the end-to-end integration. For CSI data, we use the Ultra Dense Indoor MaMIMO CSI Dataset introduced in [18], following the methodology in [8]. Since the original traces correspond to static measurements, we apply a data-augmentation procedure based on the virtualized channel gain evolution algorithm from [8], where the mean variation in channel gain due to user movement, ∆β, is modeled as a stochastic process evolving as the user moves from (XA , YA ) to (XB , YB ) over a time interval ∆t, capturing the spatial dependence of channel variations. As mentioned in Section III-A, the AE uses a fixed 50% compression ratio, halving the X-haul payload while preserving key temporal correlations and large-scale fading characteristics as demonstrated in [12]. Fixing the compression ratio enables a controlled evaluation of reconstruction fidelity,
predictor performance, and the impact of dataset augmentation in LITE. Performance evaluations (Sections IV-A, IV-B, and IV-C) use 2500 synthetically generated trajectories, larger than the 200 samples in [8]. The rationale for this dataset size and its influence on the AE design are discussed in Section IV-D. The dataset is split into training and validation sets using a 9:1 ratio, as in [8]. All models were trained for at least 1000 iterations with early stopping, using a learning rate of 0.01 and a minibatch size of 32, while inference with TensorRT was performed using a batch size of 250 samples. All experiments were conducted in a Docker container running Ubuntu 20.04.5 LTS, leveraging an NVIDIA GeForce GTX 1650 GPU (∼4,GB VRAM) with CUDA Toolkit 11.8, CUDA Runtime (PyTorch) 11.6, and cuDNN 8.3 for hardware acceleration. The software stack included PyTorch 1.13.1, TensorRT 8.5.1, and ONNX 1.17.0. A. Channel gain prediction with SE-enhanced BiLSTM In LITE, we evaluate three SE placements, before the BiLSTM, after the BiLSTM (pre-Fully-Connected/Dense (FC)), and after the FC layer, across multiple asymmetric and symmetric (f, b) hidden-size configurations. The number of forward (f ) and backward (b) hidden units significantly impacts both prediction accuracy and model complexity, as increasing hidden units generally improves temporal modeling, but larger configurations offer diminishing returns relative to parameter growth, especially when SE is applied late in the network. As shown in Table II, placing SE before the BiLSTM consistently provides the most favorable accuracy, complexity trade-off. The asymmetric (64, 128) configuration achieves the lowest Root Mean Squared Error (RMSE) of 0.127, a 5.03% improvement over the baseline, with only 91169 parameters. A smaller configuration, (64, 96), reaches RMSE = 0.129 (3.57% improvement) with just 60961 parameters, highlighting that moderate backward units effectively enhance temporal encoding without excessive complexity. These results indicate that early channel-wise recalibration enables the BiLSTM to focus its limited recurrent capacity on the most informative input dimensions, maximizing the impact of temporal modeling. For SE after the BiLSTM (pre-FC), larger hidden-size configurations, such as (128, 160), are needed to achieve competitive accuracy (RMSE = 0.130), reflecting the reduced influence of post-recurrent recalibration on the temporal features. Applying SE after the FC layer is largely insensitive to hiddensize scaling, as even the best configuration, (64, 128), yields only marginal improvement (RMSE = 0.133), indicating that recalibration at this stage cannot compensate for errors accumulated during sequence encoding. Overall, the analysis shows that asymmetric hidden-unit allocation before the BiLSTM maximizes predictive performance while maintaining parameter efficiency, the (64, 128) configuration emerges as the optimal design, offering the best balance between RMSE reduction and computational cost,
TABLE II I MPACT OF SE BLOCK PLACEMENT ON RMSE AND MODEL COMPLEXITY ACROSS VARIOUS B I LSTM HIDDEN - SIZE CONFIGURATIONS . T HE BASELINE SYMMETRIC (256, 256) MODEL FROM [8] ACHIEVES AN RMSE OF 0.134.
SE Before BiLSTM
SE After BiLSTM (pre-FC)
SE After FC
LSTM (f,b) RMSE ∆ (%) Params Red. (%) RMSE ∆ (%) Params Red. (%) RMSE ∆ (%) Params Red. (%) (32,32) (32,64) (64,32) (64,64) (64,96) (96,64) (64,128) (128,64) (96,128) (128,96) (128,128) (128,160) (160,128) (160,160) (128,192) (192,128) (192,192) (128,256) (256,128)
0.139 0.130 0.142 0.132 0.129 0.134 0.127 0.136 0.132 0.133 0.131 0.132 0.131 0.130 0.130 0.135 0.133 0.128 0.133
-3.80 2.43 -6.11 1.29 3.57 -0.20 5.03 -1.94 1.55 0.51 1.70 1.35 1.61 2.58 2.97 -0.74 0.64 3.91 0.35
11297 25121 25121 38945 60961 60961 91169 91169 113185 113185 143393 181793 181793 220193 228385 228385 313377 346145 346145
97.94 95.42 95.42 92.90 88.89 88.89 83.39 83.39 79.38 79.38 73.87 66.88 66.88 59.88 58.39 58.39 42.91 36.94 36.94
0.144 0.134 0.146 0.138 0.132 0.139 0.132 0.141 0.134 0.137 0.134 0.130 0.134 0.132 0.131 0.135 0.134 0.132 0.137
TABLE III E ND - TO - END PREDICTION PERFORMANCE UNDER DIFFERENT TRAINING STRATEGIES VS . BASELINE B I LSTM AND SE-B I LSTM. Model BiLSTM SE-BiLSTM AE → BiLSTM AE → SE-BiLSTM AE → SE-BiLSTM AE → SE-BiLSTM
Training Strategy Without AE (Baseline) Without AE Independent Independent Compression-aware End-to-end
RMSE
∆ RMSE(%)
0.134
0.00
0.127 0.152 0.146 0.142 0.166
+5.03 -13.36 -9.07 -6.58 -24.02
making it the preferred choice for edge-deployable channelgain prediction in resource-constrained scenarios. B. End-to-end prediction performance We evaluate the E2E performance of the full LITE pipeline, where the AE encoder–decoder and the SE-enhanced BiLSTM predictor operate jointly under a fixed 50% CSI compression ratio. Table III summarizes the impact of different training strategies described in Section III-C (independent, compression-aware, and fully end-to-end), compared against the BiLSTM baseline and the lightweight SE-BiLSTM trained on the original dataset (i.e., without AE compression/decompression) as references. Introducing the AE inevitably degrades performance due to reconstruction artifacts. In the independent-training setting, where the AE and the predictor are trained separately using uncompressed CSI, the AE+BiLSTM and AE+SE-BiLSTM configurations yield RMSE values of 0.152 (-13.36%) and 0.146 (-9.07%), respectively. These results highlight the mismatch between separate training and joint inference conditions.
-7.52 0.54 -9.13 -3.26 1.11 -4.12 0.98 -5.11 -0.17 -2.17 -0.01 2.67 -0.39 1.08 1.68 -1.33 -0.18 1.24 -2.56
12368 27508 27508 43160 67516 67516 100576 100576 125956 125956 160040 202828 202828 246128 254320 254320 350648 383416 383416
97.75 94.99 94.99 92.14 87.70 87.70 81.68 81.68 77.05 77.05 70.84 63.05 63.05 55.16 53.66 53.66 36.11 30.14 30.14
0.146 0.139 0.150 0.142 0.134 0.140 0.133 0.144 0.135 0.139 0.136 0.136 0.139 0.136 0.134 0.139 0.136 0.135 0.141
-9.03 -3.62 -12.1 -5.85 -0.10 -5.04 0.58 -7.47 -0.62 -4.34 1.90 -2.05 -3.67 -1.66 -0.40 -3.80 -1.65 0.90 -5.67
11297 25121 25121 38945 60961 60961 91169 91169 113185 113185 143393 181793 181793 220193 228385 228385 313377 346145 346145
97.94 95.42 95.42 92.90 88.89 88.89 83.39 83.39 79.38 79.38 73.87 66.88 66.88 59.88 58.39 58.39 42.91 36.94 36.94
TABLE IV GPU MEMORY USAGE OF THE T ENSOR RT- OPTIMIZED B I LSTM AND SE-B I LSTM ENGINES DURING DEPLOYMENT. Metric Engine Device Memory [MiB]
BiLSTM 12.06
SE-BiLSTM 24.06
TABLE V L ATENCY – THROUGHPUT TRADE - OFFS FOR T ENSOR RT- OPTIMIZED B I LSTM AND SE-B I LSTM. L ATENCY PER SAMPLE IS MEASURED WITH BATCH SIZE 250; IMPROVEMENT (%) IS RELATIVE TO THE NON - OPTIMIZED B I LSTM BASELINE . Model BiLSTM BiLSTM SE-BiLSTM SE-BiLSTM
Optimized No Yes No Yes
Lat/sample (ms) 0.03155 0.01775 0.01174 0.00679
QPS 31697 56332 85157 147267
Imp. (%) 0 +77.7 +168.6 +364.5
The compression-aware strategy addresses this issue by training the SE-BiLSTM on AE-decoded trajectories, allowing it to adapt to distortions introduced during reconstruction. This improves performance to RMSE = 0.142 (-6.58%), reducing the accuracy degradation and confirming that separating reconstruction adaptation from temporal prediction provides the most robust outcome under fixed-compression constraints. Fully end-to-end training underperforms, producing RMSE = 0.166 (-24.02%), due to unstable gradients and conflicting objectives between reconstruction and forecasting. These results corroborate that, for aggressive compression, disentangling the learning of reconstruction and temporal prediction is more effective than joint optimization.
TABLE VI E ND - TO - END EFFECT OF DATASET SIZE N ON TRAJECTORY DIVERSITY (P EARSON CORRELATION ), AE RECONSTRUCTION , AND PREDICTOR PERFORMANCE . F OR EACH N , THE SAME AE FEEDS ALL PREDICTORS . H IGHLIGHTED ROW (N = 2500) SHOWS THE BEST TRADE - OFF BETWEEN RECONSTRUCTION ACCURACY AND EFFECTIVE DIVERSITY UNDER 50% CSI COMPRESSION . N
Mean
200 1000 1500 2000 2500 3000 3500 4000
0.513 0.689 0.714 0.712 0.707 0.787 0.776 0.793
Pearson Corr. Std Median 0.079 0.158 0.137 0.133 0.132 0.056 0.060 0.053
0.529 0.733 0.746 0.745 0.738 0.794 0.785 0.800
MSE 0.352 0.035 0.025 0.018 0.009 0.002 0.001 0.001
Autoencoder RMSE R2 0.593 0.187 0.158 0.133 0.094 0.047 0.037 0.028
0.636 0.964 0.975 0.982 0.991 0.998 0.999 0.999
Baseline (without AE) SE-BiLSTM BiLSTM 0.213 0.220 0.131 0.143 0.143 0.154 0.136 0.142 0.127 0.134 0.181 0.183 0.182 0.182 0.188 0.192
Prediction RMSE (Same AE per N) Independent Comp.-aware AE→BiLSTM AE→SE-BiLSTM AE→SE-BiLSTM 0.575 0.570 0.555 0.216 0.211 0.208 0.215 0.210 0.210 0.180 0.179 0.174 0.152 0.146 0.142 0.189 0.187 0.183 0.186 0.186 0.181 0.194 0.190 0.188
End-to-end AE→SE-BiLSTM 0.567 0.212 0.205 0.190 0.166 0.218 0.208 0.220
C. Memory and prediction time at deployment While previous Sections focuses on lowering model memory requirements at inference through the use of an efficient attention mechanism (Section IV-A and IV-B), this section analyzes the impact of model architecture and optimization on memory footprint and inference latency at deployment. We evaluated the BiLSTM and SE-BiLSTM models using identical TensorRT configurations (trtexec) with FP16 mixed precision and matched dynamic shape profiles. Table IV reports the persistent device memory allocated by the TensorRT engines during runtime. The SE-BiLSTM engine requires 24.06 MiB of device memory, compared to 12.06 MiB for the BiLSTM, representing an increase of approximately 2×. In TensorRT, device memory at runtime includes not only the model weights, but also persistent state and enqueue memory for intermediate activations and scratch buffers required during network execution. Focusing on latency and throughput, Table V summarizes the results for both models under TensorRT-optimized inference with a fixed batch size of 250 sequences. For the TensorRT-optimized BiLSTM model, the latency per sample decreases to 0.01775 ms, corresponding to a throughput of 56332 QPS and a 77.7% improvement relative to the nonoptimized baseline. The inference throughput, measured in QPS, is computed as 1/ls, where ls is latency per sample (s). The TensorRT-optimized SE-BiLSTM achieves a latency per sample of 0.00679 ms and a throughput of 147267 QPS, which corresponds to a 364.5% improvement relative to the BiLSTM non-optimized baseline. Compared to the nonoptimized SE-BiLSTM throughput of 85157 QPS, TensorRT provides an additional throughput gain of 72.9%. Although the SE-BiLSTM exhibits an approximately 2× higher TensorRT engine memory footprint, it remains within the capacity of typical Near-RT RIC platforms. While this increase may affect multi-model deployment on resourceconstrained systems, the efficient squeeze-and-excitation mechanism and TensorRT optimization enable substantially lower inference latency and higher throughput. These results indicate that the LITE architecture is well-suited for edge deployment scenarios requiring low-latency, high-throughput CSI prediction.
Fig. 3. Step-wise Pearson correlation of CSI trajectories for increasing dataset sizes N.
D. Data Augmentation: Impact on AE and Predictor Performance The AE plays a central role in this framework by compressing the CSI, reducing the communication overhead over the X-haul while enabling accurate reconstruction at the receiver. To achieve this, it must be trained on a sufficiently large and diverse set of trajectories. Excessively correlated synthetic trajectories, however, induce averaging behavior during training, which degrades the reconstruction of fine-grained channel-gain variations and limits the usefulness of the compressed representation for both accurate recovery and efficient transmission. Table VI and Fig. 3 summarize the impact of dataset size N on trajectory correlation (measured using Pearson correlation), AE reconstruction performance, and downstream prediction error. For small datasets, such as N = 200, corresponding to the largest dataset used in [8], the low mean correlation (0.513) reflects high variability, but insufficient coverage of the trajectory space results in poor AE reconstruction (MSE 0.352, RMSE 0.593) and lowest performance among all predictors. As N increases to 1000–2000, the mean Pearson correlation rises (0.689–0.712) while sufficient variability remains, leading to substantial improvements in AE reconstruction (RMSE 0.187–0.133) and better predictive performance across the BiLSTM variants. The AE accurately reconstructs the generated sequences, providing high-quality inputs to the predictors
while retaining meaningful temporal dynamics. The best trade-off between dataset size and effective trajectory diversity is observed at N = 2500. Here, the AE achieves very low reconstruction error (RMSE 0.094, R2 = 0.991) and the predictors reach optimal performance (BiLSTM RMSE 0.134, SE-BiLSTM RMSE 0.127) while the mean Pearson correlation remains moderate (0.707) with non-negligible variance. This indicates that the dataset is sufficiently large for accurate learning yet still preserves trajectory variability, allowing the BiLSTM models to capture relevant temporal patterns effectively. For N > 2500, AE reconstruction continues to improve (RMSE 0.047–0.028) and mean correlation increases (0.776– 0.793), but the variance of the correlation drops sharply, indicating highly homogeneous trajectories. This homogenization reduces the effective diversity of the inputs: sequences are reconstructed accurately, yet their temporal nuances become too uniform for the BiLSTM to extract additional information, leading to plateaued or slightly degraded predictor performance (e.g., SE-BiLSTM RMSE 0.181–0.188 for N = 3000–4000). These observations align with prior studies on synthetic time series and sequence modeling [19], which show that adding synthetic samples without preserving diversity can produce redundant patterns that limit predictors’ ability to capture temporal dynamics. In our case, this explains why increasing N beyond 2500 improves AE reconstruction but does not further benefit BiLSTM performance, supporting the choice of N = 2500 as the balanced dataset size for evaluating LITE. V. C ONCLUSION AND F UTURE W ORK This work introduced LITE, a lightweight end-to-end pipeline for trajectory-unaware channel-gain prediction in CFMaMIMO systems under O-RAN constraints. By combining a compact 1-D convolutional autoencoder at the O-DU with an asymmetric SE-enhanced BiLSTM at the Near-RT RIC, LITE reduces X-haul transport load and computational footprint while maintaining short-horizon prediction accuracy. The evaluation demonstrates that: (i) asymmetric SEBiLSTM architectures improve accuracy with significantly lower model complexity compared to symmetric baselines; (ii) compression-aware training effectively compensates for AE-induced distortions, limiting accuracy loss to 6% under a fixed 50% CSI compression ratio versus the BiLSTM baseline; and (iii) a TensorRT implementation delivers a 4.6× throughput improvement, enabling real-time inference at the RIC. Collectively, these results show that LITE provides a practical, deployment-aligned solution for mobility-driven channel prediction in open, disaggregated RAN environments. Future research directions include: (i) evaluating LITE on real dynamic CSI traces to assess robustness under realistic propagation and hardware conditions; (ii) jointly optimizing compression ratio and predictor architecture for adaptive Xhaul utilization based on traffic and mobility; (iii) integrating LITE into closed-loop Near-RT RIC control pipelines, e.g., mobility-aware clustering, handover optimization, or beam
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