We introduce Themis, a scheme for introducing fair ordering of transactions into (permissioned) Byzantine consensus protocols with at most ƒ faulty nodes among n ≥ 4ƒ + 1. Themis enforces the strongest notion of fair ordering proposed to date. It also achieves standard liveness, rather than the weaker notion of previous work with the same fair ordering property.

A key performance metric in blockchains is the latency between when a transaction is broadcast and when it is confirmed (the so-called, confirmation latency). While improvements in consensus techniques can lead to lower confirmation latency, a fundamental lower bound on confirmation latency is the propagation latency of messages through the underlying peer-to-peer (p2p) network (in Bitcoin, the propagation latency is several tens of seconds). The de facto p2p protocol used by Bitcoin and other blockchains is based on random connectivity: each node connects to a random subset of nodes. The induced p2p network topology can be highly suboptimal since it neglects geographical distance, differences in bandwidth, hash-power and computational abilities across peers. We present Perigee, a decentralized algorithm that automatically learns an efficient p2p topology tuned to the aforementioned network heterogeneities, purely based on peers' interactions with their neighbors. Motivated by the literature on the multi-armed bandit problem, Perigee optimally balances the tradeoff between retaining connections to known well-connected neighbors, and exploring new connections to previously-unseen neighbors. Experimental evaluations show that Perigee reduces the latency to broadcast by 33%. Lastly Perigee is simple, computationally lightweight, adversary-resistant, and compatible with the selfish interests of peers, making it an attractive p2p protocol for blockchains.

With an intention to provide robust broadband connection to rural areas, Government of India is laying out optical fiber cables across the country connecting the rural offices (named Gram Panchayat) under the initiative BharatNet. This work explores the feasibility of implementing a middle-mile network from these Gram Panchayats to the nearby villages, where wireless clusters will be set up, using LTE-Advanced over TV White Spaces owing to excellent propagation characteristics of the frequencies in TV UHF band. A proportionally fair radio resource allocation over the middle-mile network is proposed that uses Coordinated Multipoint Technology offered by Long Term Evolution — Advanced (LTE-A) which satisfies the broadband requirement. The simulation results have shown that for a cell radius of Coordination Region below 5 km, a rate of 1 Mbps per end-user for rural population density of India is achievable, which is more than the 512 Kbps target rate prescribed by the Telecom Regulatory Authority of India (TRAI).