Communication complexity

About: Communication complexity is a research topic. Over the lifetime, 3870 publications have been published within this topic receiving 105832 citations.

Location-Independent Communication for Mobile Agents: A Two-Level Architecture

Abstract: We study communication primitives for interaction between mobile agents. They can be classified into two groups. At a low level there are location dependent primitives that require a programmer to know the current site of a mobile agent in order to communicate with it. At a high level there are location independent primitives that allow communication with a mobile agent irrespective of its current site and of any migrations. Implementation of these requires delicate distributed infrastructure. We propose a simple calculus of agents that allows implementations of such distributed infrastructure algorithms to be expressed as encodings, or compilations, of the whole calculus into the fragment with only location dependent communication. These encodings give executable descriptions of the algorithms, providing a clean implementation strategy for prototype languages. The calculus is equipped with a precise semantics, providing a solid basis for understanding the algorithms and for reasoning about their correctness and robustness. Two sample infrastructure algorithms are presented as encodings.

Lower Bounds on Information Complexity via Zero-Communication Protocols and Applications

Abstract: We show that almost all known lower bound methods for communication complexity are also lower bounds for the information complexity. In particular, we define a relaxed version of the partition bound of Jain and Klauck [Proceedings of the 2010 IEEE 25th Annual Conference on Computational Complexity, 2010, pp. 247--258] and prove that it lower bounds the information complexity of any function. Our relaxed partition bound subsumes all norm-based methods (e.g., the $\gamma_2$ method) and rectangle-based methods (e.g., the rectangle/corruption bound, the smooth rectangle bound, and the discrepancy bound), except the partition bound. Our result uses a new connection between rectangles and zero-communication protocols, where the players can either output a value or abort. We prove, using a sampling protocol designed by Braverman and Weinstein [in Approximation, Randomization, and Combinatorial Optimization, Lecture Notes in Comput. Sci. 7408, Springer, Heidelberg, 2012, pp. 459--470], the following compression l...

Efficient PDA synchronization

Abstract: Modern personal digital assistant (PDA) architectures often utilize a wholesale data transfer protocol known as "slow sync" for synchronizing PDAs with personal computers (PCs). This approach is markedly inefficient with respect to bandwidth usage, latency, and energy consumption since the PDA and PC typically share many common records. We propose, analyze, and implement a novel PDA synchronization scheme (CPIsync) predicated upon previous information-theoretic research. The salient property of this scheme is that its communication complexity depends on the number of differences between the PDA and PC, and is essentially independent of the overall number of records. Moreover, our implementation shows that the computational complexity and energy consumption of CPIsync is practical and that the-overall latency is typically much smaller than that of slow sync or alternative synchronization approaches based on Bloom (1970) filters. Thus, CPIsync has potential for significantly improving synchronization protocols for PDAs and, more generally, for heterogeneous networks of many machines.

Cryptography in radio frequency identification and fair exchange protocols

Abstract: This PhD thesis focuses on fair exchange protocols and radio frequency identification protocols Fair exchange stems from a daily life problem: how can two people exchange objects (material or immaterial) fairly, that is, without anyone being hurt in the exchange? More formally, if Alice and Bob each have objects mA and mB respectively, then the exchange is fair if, at the end of the protocol, both Alice and Bob have received mB and mA respectively, or neither Alice nor Bob have received the expected information, even partially Ensuring fairness in an exchange is impossible without introducing additional assumptions Thus, we propose two approaches to overcome this problem The first consists in attaching to each person, a guardian angel, that is, a security module conceived by a trustworthy authority and whose behavior cannot deviate from the established rules In such a model, the fairness of the exchange can be ensured with a probability as close to 1 as desired, implying however a communication complexity cost We then use results from the distributed algorithm to generalize this approach for n people Finally, we propose a second approach that consists in no more considering the exchange in an isolated manner, but to replace it in its context, in the heart of a network, where each person in the pair has a few honest neighbors In this framework, fairness can lie on these neighbors, who are solicited only in the case of a conflict during the exchange We then look into Radio Frequency Identification (RFID), which consists in remotely identifying objects or subjects having a transponder The great achievements that radio frequency identification has made today, lies essentially on the willingness to develop low cost and small size transponders Consequently, they have limited computation and storage capabilities Due to this reason, many questions have been asked regarding RFID's potential and limitations, more precisely in terms of security and privacy Since this is a recent problem, the works presented in this document first outline completely the framework by introducing certain basic concepts In particular, we present and classify threats, we show the link between traceability and the communication model, and we analyze existing RFID protocols We also present the complexity issues due to key management We show that the solution proposed by Molnar and Wagner has weaknesses and we propose another solution based on time-memory trade-offs Finally, we continue our time-memory trade-off analysis by proposing a method based on checkpoints, which allows detecting false alarms in a probabilistic manner

Symbol mapping diversity design for multiple packet transmissions

Abstract: In this paper, we present a simple, but effective method of enhancing and exploiting diversity from multiple packet transmissions in systems that employ nonbinary linear modulations such as phase-shift keying (PSK) and quadrature amplitude modulation (QAM). This diversity improvement results from redesigning the symbol mapping for each packet transmission. By developing a general framework for evaluating the upper bound of the bit error rate (BER) with multiple transmissions, a criterion to obtain optimal symbol mappings is attained. The optimal adaptation scheme reduces to solutions of the well known quadratic assignment problem (QAP). Symbol mapping adaptation only requires a small increase in receiver complexity but provides very substantial BER gains when applied to additive white Gaussian noise (AWGN) and flat-fading channels.