Multi-message Broadcast Research Articles

An Exact Implementation of the Abstract MAC Layer via Carrier Sensing in Dynamic Networks

In this paper, we present the first algorithm to precisely implement the abstract MAC (absMAC) layer under the physical SINR model in dynamic networks. The absMac layer, first presented by (Kuhn et al., 2009), provides reliable local broadcast communications, with timing guarantees stated in terms of a collection of abstract delay functions, based on which high-level algorithms can be designed, independent of specific channel behaviors. The implementation of absMAC requires the design of a distributed algorithm for the local broadcast communication primitives over a particular communication model that defines concrete channel behaviors, and the objective is to minimize the bounds of the abstract delay functions. Halldórsson et al. (2015) showed that under the standard SINR model (synchronous communications without physical carrier sensing or location information), there exist no efficient exact implementations. In this work, we demonstrate that physical carrier sensing, a commonly seen function performed by wireless devices, can help get efficient exact implementation algorithms. Specifically, we propose an algorithm that precisely implements the absMAC layer under the SINR model in dynamic networks. The algorithm provides asymptotically optimal bounds for both acknowledgement and progress functions defined in the absMAC layer. Our algorithm leads to many new faster algorithms for solving high-level problems under the SINR model in dynamic networks. We demonstrate this by exemplifying problems of Consensus, Multi-Message Broadcast, and Single-Message Broadcast. It deserves to point out that our implementation algorithm is designed based on an optimal algorithm for a General Local Broadcast (GLB) problem, which takes the number of distinct messages into consideration for the first time. The GLB algorithm can handle many communication scenarios apart from those defined in the absMAC layer. Simulation results show that our proposed algorithms perform well in reality.

Decomposing broadcast algorithms using abstract MAC layers

In much of the theoretical literature on global broadcast algorithms for wireless networks, issues of message dissemination are considered together with issues of contention management. This combination leads to complicated algorithms and analysis, and makes it difficult to extend the work to more difficult communication problems. In this paper, we present results aimed at simplifying such algorithms and analysis by decomposing the treatment into two levels, using abstract “MAC layer” specifications to encapsulate contention management. We use two different abstract MAC layers: the basic layer of [1,2] and a new probabilistic layer.We first present a typical randomized contention-management algorithm for a standard graph-based radio network model and show that it implements both abstract MAC layers. Then we combine this algorithm with greedy algorithms for single-message and multi-message global broadcast and analyze the combinations, using both abstract MAC layers as intermediate layers. Using the basic MAC layer, we prove a bound of ODlogn∊log(Δ) for the time to deliver a single message everywhere with probability 1−∊, where D is the network diameter, n is the number of nodes, and Δ is the maximum node degree. Using the probabilistic layer, we prove a bound of OD+logn∊log(Δ), which matches the best previously-known bound for single-message broadcast over the physical network model. For multi-message broadcast, we obtain bounds of O(D+kΔ)logn∊log(Δ) using the basic layer and OD+kΔlogn∊log(Δ) using the probabilistic layer, for the time to deliver a message everywhere in the presence of at most k concurrent messages.

The abstract MAC layer

A diversity of possible communication assumptions complicates the study of algorithms and lower bounds for radio networks. We address this problem by defining an abstract MAC layer. This service provides reliable local broadcast communication, with timing guarantees stated in terms of a collection of abstract delay functions applied to the relevant contention. Algorithm designers can analyze their algorithms in terms of these functions, independently of specific channel behavior. Concrete implementations of the abstract MAC layer over basic radio network models generate concrete definitions for these delay functions, automatically adapting bounds proven for the abstract service to bounds for the specific radio network under consideration. To illustrate this approach, we use the abstract MAC layer to study the new problem of Multi-Message Broadcast, a generalization of standard single-message broadcast in which multiple messages can originate at different times and locations in the network. We present and analyze two algorithms for Multi-Message Broadcast in static networks: a simple greedy algorithm and one that uses regional leaders. We then indicate how these results can be extended to mobile networks.

Universally composable one-time signature and broadcast authentication

Broadcast authentication is a vital security primitive for the management of a copious number of parties. In the universally composable framework, this paper investigates broadcast authentication using one-time signature based on the fact that one-time signature has efficient signature generation and verification suitable for low-power devices, and gives immediate authentication, which is a favorable property for time-critical messages. This paper first formulates a broadcast authentication model with the ideal functionalities such as one-time signature and broadcast authentication, and proposes a broadcast authentication scheme in the hybrid model. This paper then improves HORS, which is secure based on a strong assumption (i.e., a subset-resilient hash function) and presents the improved version as HORS+, which differs from HORS such that it is a secure one-time signature based on weaker assumptions, i.e. one-way functions, one-way hash functions and collision-resistant hash functions. At the same time, a protocol OWC using one-way chains is proposed to provide more registered keys for multi-message broadcast authentication. Our broadcast authentication scheme constructed by the combined use of HORS+ and OWC is universally composable secure and suitable for low-power devices.