ISAC is an emerging paradigm in 6G networks that enables environmental sensing using wireless communication infrastructure. Current O-RAN specifications lack the architectural primitives for sensing integration: no service models expose physical-layer observables, no execution frameworks support sub-millisecond sensing tasks, and fronthaul interfaces cannot correlate transmitted waveforms with their reflections. This article proposes three extensions to O-RAN for monostatic sensing, where transmission and reception are co-located at the base station. First, we specify sensing dApps at the O-DU that process IQ samples to extract delay, Doppler, and angular features. Second, we define E2SM-SENS, a service model enabling xApps to subscribe to sensing telemetry with configurable periodicity. Third, we identify required Open Fronthaul metadata for waveform-echo association. We validate the architecture through a prototype implementation using beamforming and Full-Duplex operation, demonstrating closed-loop control with median end-to-end latency suitable for near-real-time sensing applications. While focused on monostatic configurations, the proposed interfaces extend to bistatic and cooperative sensing scenarios.

翻译：ISAC是6G网络中的一种新兴范式，它利用无线通信基础设施实现环境感知。当前的O-RAN规范缺乏支持感知集成的架构原语：没有服务模型能够暴露物理层可观测量，没有执行框架支持亚毫秒级感知任务，且前传接口无法关联发射波形与其反射信号。本文针对收发端共址于基站的单站感知场景，提出了对O-RAN的三项扩展。首先，我们在O-DU层设计了感知型分布式应用，用于处理IQ样本以提取时延、多普勒频移与角度特征。其次，我们定义了E2SM-SENS服务模型，使xApps能够以可配置周期订阅感知遥测数据。第三，我们明确了实现波形-回波关联所需的Open Fronthaul元数据。通过采用波束成形与全双工操作的原型系统验证了该架构，其端到端延迟中位数满足近实时感知应用的闭环控制需求。虽然本文聚焦于单站配置，所提出的接口可扩展至双站及协作感知场景。