Research and Design of a Large Model for Location-Based Service Awareness and Feature Extraction Based on a Mobile 5G Single Station
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摘要: 随着复杂室内场景下位置业务与定位需求持续增长,基于5G无线信号的室内定位成为重要研究方向。现有5G定位方案多依赖多站协同或固定单站部署,在非视距 (NLOS)、基站稀疏环境下容易失效。传统指纹定位方法通过融合多站的信号特征,能够在一定程度上克服非视距带来的问题,但存在泛化能力有限、对未知位置特征提取能力不足的问题,造成定位精度下降。为此,本文提出一种可移动5G单站大模型定位方法,构建专用定位大模型LLM4CSI-RS,采用参数高效微调 (PEFT) 策略优化训练,融合单站动态感知与大模型推理能力,建立无线测量指纹到参考点 (RP) 的映射关系,从而在无需终端主动配合的条件下,实现复杂室内环境下的被动式定位。真实室内NLOS场景下的实验验证了该方法的有效性,可达到1.25 m平均定位误差,为室内复杂场景下的位置业务感知提供了基于可移动5G单站指纹定位的技术路径。Abstract:
Objective The growing demand for high-precision localization in complex indoor scenarios such as industrial warehouses and smart buildings has made 5G integrated sensing and communication (ISAC) a promising enabling technology. However, existing 5G localization schemes are predominantly designed for multi-station cooperation or fixed single-station deployment. Multi-station approaches rely heavily on dense base station deployment, which fails to work in infrastructure-sparse scenarios. Fixed single-station solutions suffer from severe performance degradation in non-line-of-sight (NLOS) and multipath environments due to the limited observation perspective, and conventional fingerprint localization algorithms have limited generalization ability for unknown positions. To address these limitations, this paper proposes a mobile 5G single-station localization framework based on large models, which enables passive localization without active terminal cooperation. Methods A mobile 5G single-station sensing prototype is developed based on the OpenAirInterface (OAI) platform, USRP B210 software-defined radio and automated guided vehicle (AGV) platform ( Fig. 1 ). By reusing the native channel state information reference signal (CSI-RS) measurement and CSI Report reporting mechanism in 5G NR, CSI reports are parsed at the gNB side and reference signal received power (RSRP) sequences are extracted to construct a dedicated localization fingerprint dataset, without introducing additional dedicated sensing signals (Fig. 2 ). A specialized localization large model named LLM4CSI-RS is built upon the Llama-3.2-3B-Instruct backbone. Parameter-efficient fine-tuning (PEFT) is implemented via low-rank adaptation (LoRA), where only the low-rank matrices in attention projection layers are updated while the pre-trained weights remain frozen, significantly reducing training overhead and mitigating overfitting (Table 1 ). During online inference, the model outputs confidence scores of candidate reference points, and the final position is estimated through a Top-K weighted fusion strategy.Results and Discussions Extensive experiments are conducted in a real-world indoor NLOS scenario ( Fig. 6 ). The proposed LLM4CSI-RS method achieves a mean localization error of 1.25 m, a 95th percentile error of 2.45 m, and an accuracy of 86.06% within the 2 m error threshold, with the steepest rise in cumulative probability in the low-error range (Fig. 7 ). Systematic hyperparameter tuning confirms that the baseline low-rank adaptation configuration yields the optimal performance for this task (Table 2 ). Ablation studies validate the effectiveness of each key module, and the full configuration — with low-rank adaptation applied to all attention projection matrices, a single-layer linear classifier, global mean pooling and Top-4 weighted fusion — delivers the best overall performance (Table 3 ). Comparative experiments across multiple backbone models show that Llama-3.2-3B strikes the optimal balance between feature representation capability and computational cost, avoiding underfitting in smaller models and overfitting in larger ones (Fig. 8 ). Compared with conventional deep learning baselines including CNN, DNN and LSTM, the proposed method consistently outperforms all benchmarks (Fig. 9 ).Conclusions The proposed framework integrates the multi-perspective dynamic sensing capability of mobile single stations and the deep sequence modeling ability of large models, effectively alleviates the performance degradation caused by NLOS and sparse infrastructure, and significantly improves localization accuracy and robustness. It provides a low-deployment-cost and scalable technical path for indoor localization in complex scenarios, and offers a practical reference for industrial-grade indoor location-based services. -
表 3 消融实验结果
消融配置 平均误差 95%累计误差 Acc@2m 基线 (Top-4) 1.25 2.45 86.06 微调模块:$ q,k,v $ 1.51 2.20 83.89 多层分类头 1.68 2.90 65.67 末Token池化 1.70 2.63 75.61 Top-3加权融合 1.42 3.04 74.94 Top-5加权融合 1.37 2.24 85.33 表 1 实验参数配置
参数类别 参数名称 配置说明 基座模型 预训练模型 Llama-3.2-3B-Instruct 微调 LoRA超参数 $ r $=8, $ \alpha $=32 LoRA目标模块 q, k, v, o 模型结构 序列池化方式 全局均值池化 分类头结构 单层线性分类头 训练优化 学习率 $ 2\times 1{0}^{-4} $ 优化器 AdamW 损失函数 标签平滑交叉熵 推理策略 加权融合方式 Top-4概率加权融合 表 2 不同LoRA配置的实验结果
LoRA配置 $ (r,\alpha ) $ 平均误差 95%累计误差 Acc@2m 基线(8,32) 1.25 2.45 86.06 (4,8) 1.34 2.44 85.44 (8,16) 1.30 2.41 82.11 (16,32) 1.42 2.47 80.22 -
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