arXiv subjects

Xin Zhe Khooi

Publications and source records attributed to Xin Zhe Khooi.

5 recordsLinked to original sources

arXiv2026

Weaver: A System for AI-RAN Compute Sharing with Foundation Model Training

The emergence of AI-RAN infrastructure, which equips cell sites with GPU-accelerated hardware, creates an opportunity to colocate non-RAN workloads with primary RAN processing. We explore using this spare capacity for decentralized training of foundation models (FMs), one of the most compute-intensive AI workloads. We present the first characterization of spare GPU capacity in AI-RAN systems at both micro-scale--across transmission slots within a cell site--and macro-scale--across sites. Our analysis finds that 40-85% of GPU capacity is unused; although this capacity is temporally bursty at individual sites, it is spatially complementary across sites. To safely and efficiently harness these resources, we present Weaver, a system that opportunistically trains FMs alongside latency-critical RAN workloads without degrading RAN performance. Weaver adopts a RAN-first design: a spare-compute controller integrated into the MAC scheduler uses compute-aware scheduling to smooth RAN GPU demand and exposes more usable spare GPU capacity. A two-level elastic training framework then adapts to dynamic, heterogeneous spare capacity within and across sites. Experiments on an O-RAN-aligned system prototype show that Weaver creates up to 4.9x more usable spare compute and utilizes up to 83% of the available spare capacity. On a multi-site testbed, Weaver improves training throughput by 2.1-3.7x over baseline approaches.

cs.DC↗

arXiv2026

Towards Operator-Empowered Vulnerability Hotfixing for 5G Radio Access Networks

Cellular protocol vulnerabilities can remain exploitable for months or years while standards bodies, vendors, and mobile network operators (MNOs) coordinate permanent fixes. We present Buckler, a framework that enables an MNO to deploy temporary, local, and reversible hotfixes in its radio access network (RAN) during this exposure window. Buckler places reusable hooks at standardized L2/L3 channel boundaries and exposes a closed, stateful match-action interface with three preventive actions: DROP, MODIFY, and RELEASE. We evaluate whether this bounded design provides useful coverage without requiring extensive changes to existing RANs. From 23 papers, we identify 64 attacks rooted in standard L2/L3 protocol behavior, of which 43 provide a preventive intervention point at the RAN, and we construct Buckler hotfixes for 20 of them. All 20 hotfixes use the same rule vocabulary and only five standardized channel hooks, while the unsupported attacks expose endpoint dependencies that a RAN cannot satisfy alone. We implement the five hooks on srsRAN and OpenAirInterface with small, structurally similar changes, and demonstrate all three actions against representative availability and privacy attacks. These results establish operator-empowered hotfixing as a practical and portable interim defense and delineate the architectural limits of RAN-only prevention.

cs.CR↗

arXiv2026

Symphony: Taming Step Misalignments in the Network for Ring-based Collective Operations

Ring-based collective operations are widely used in distributed AI training due to their efficient bandwidth utilization. While ring communication excels at pipelining, its performance is heavily dependent on having synchronized step-wise progression. This presents a mismatch to the underlying network conditions in practice: collective operations are vulnerable to network jitter and congestion, leading to step misalignment and increased collective completion time. To that end, we propose Symphony, an in-network solution that detects pipeline step misalignment and mitigates its impact. Symphony introduces (1) a lightweight mechanism to track per-job pipeline progress and (2) a novel use of congestion signals to selectively throttle outpacing flows, allowing lagging flows to catch up without global coordination. Through simulations using Astra-Sim, we show that Symphony effectively mitigates step misalignments in ring-based collectives, resulting in up to 54% improvement in job/collective communication time. Finally, we prototype and validate Symphony on an Intel Tofino2 programmable switch to demonstrate its practicality.

cs.NI↗

arXiv2025

ProtO-RU: An O-RAN Split-7.2 Radio Unit using SDRs

We present ProtO-RU, the first open source, software-defined O-RAN Split-7.2 Radio Unit built using SDRs and commodity CPUs. Unlike proprietary hardware-based commercial O-RUs, ProtO-RU is built on the open-source srsRAN software stack, and it is fully programmable. We demonstrate that ProtO-RU integrates with the srsRAN and OpenAirInterface5G CU/DU stacks, supports both TDD and FDD duplexing modes, and interoperates with commercial 5G UEs. Our evaluation shows that ProtO-RU remains stable under sustained load with multiple UEs and delivers throughput comparable to Split-8 and commercial O-RUs. ProtO-RU opens up new opportunities for RU-level innovations and lowers the barrier of entry for end-to-end O-RAN research.

cs.NI↗

arXiv2022

The Case for Accelerating BFT Protocols Using In-Network Ordering

Mission critical systems deployed in data centers today are facing more sophisticated failures. Byzantine fault tolerant (BFT) protocols are capable of masking these types of failures, but are rarely deployed due to their performance cost and complexity. In this work, we propose a new approach to designing high performance BFT protocols in data centers. By re-examining the ordering responsibility between the network and the BFT protocol, we advocate a new abstraction offered by the data center network infrastructure. Concretely, we design a new authenticated ordered multicast primitive (AOM) that provides transferable authentication and non-equivocation guarantees. Feasibility of the design is demonstrated by two hardware implementations of AOM -- one using HMAC and the other using public key cryptography for authentication -- on new-generation programmable switches. We then co-design a new BFT protocol, Matrix, that leverages the guarantees of AOM to eliminate cross-replica coordination and authentication in the common case. Evaluation results show that Matrix outperforms state-of-the-art protocols on both latency and throughput metrics by a wide margin, demonstrating the benefit of our new network ordering abstraction for BFT systems.

cs.DC↗