Feature-Indexed Federated Recommendation with Residual-Quantized Codebooks

TL;DR

This paper introduces RQFedRec, a federated recommendation method that uses feature codebooks and residual quantization to reduce communication costs, improve generalization to non-interacted items, and enhance robustness against noisy feedback.

Contribution

It proposes a novel feature-indexed communication paradigm and a residual quantization-based codebook approach for federated recommendation systems, addressing key limitations of existing ID-indexed methods.

Findings

Outperforms state-of-the-art federated recommendation baselines.

Reduces communication overhead significantly.

Improves robustness to noisy client feedback.

Abstract

Federated recommendation provides a privacy-preserving solution for training recommender systems without centralizing user interactions. However, existing methods follow an ID-indexed communication paradigm that transmit whole item embeddings between clients and the server, which has three major limitations: 1) consumes uncontrollable communication resources, 2) the uploaded item information cannot generalize to related non-interacted items, and 3) is sensitive to client noisy feedback. To solve these problems, it is necessary to fundamentally change the existing ID-indexed communication paradigm. Therefore, we propose a feature-indexed communication paradigm that transmits feature code embeddings as codebooks rather than raw item embeddings. Building on this paradigm, we present RQFedRec, which assigns each item a list of discrete code IDs via Residual Quantization (RQ)-Kmeans. Each client generates and trains code embeddings as codebooks based on discrete code IDs provided by the server, and the server collects and aggregates these codebooks rather than item embeddings. This design makes communication controllable since the codebooks could cover all items, enabling updates to propagate across related items in same code ID. In addition, since code embedding represents many items, which is more robust to a single noisy item. To jointly capture semantic and collaborative information, RQFedRec further adopts a collaborative-semantic dual-channel aggregation with a curriculum strategy that emphasizes semantic codes early and gradually increases the contribution of collaborative codes over training. Extensive experiments on real-world datasets demonstrate that RQFedRec consistently outperforms state-of-the-art federated recommendation baselines while significantly reducing communication overhead.