Multipaths and rate stability

Multipath solutions have been shown to help improve throughput, reliability and/or load balancing. This paper seeks to understand if and when they benefit rate stability. Rate stability is important to many real-time, interactive applications, e.g., streaming video, but whether multipath solutions can help is unclear. Of relevance is the time-scale at which bandwidth changes are detected and acted upon to rebalance transmissions across paths. Consider two boundary cases: instantaneous detection and rate re-allocation, and a static rate assignment based on long-term path statistics. When transmissions can be instantaneously rebalanced across paths based on real-time link rate information, a multipath solution trivially improves rate stability (it all but eliminates rate variations). In contrast, when rate allocations are static, we find that multipath cannot improve upon the best single-path solution when buffers are large. When buffers are small (and coding is used to overcome losses), a multipath solution can, however, be beneficial even under a static rate allocation. The paper provides insight into when and how multipath solutions can help improve rate stability.