We consider the SINR wireless model with uniform power. In this model the success of a transmission is determined by the ratio between the strength of the transmission signal and the noise produced by other transmitting processors plus ambient noise. The local broadcasting problem is a fundamental problem in this setting. Its goal is producing a schedule in which each processor successfully transmits a message to all its neighbors. This problem has been studied in various variants of the setting, where the best currently-known algorithm has running time O(Δ+log2n) in n-node networks with feedback, where Δ is the maximum neighborhood size . In the latter setting processors receive free feedback on a successful transmission. We improve this result by devising a local broadcasting algorithm with time O(Δ+lognloglogn) in networks with feedback. Our result is nearly tight in view of the lower bounds Ω(Δ) and Ω(logn) . Our results also show that the conjecture that Ω(Δ+log2n) time is required for local broadcasting  is not true in some settings. We also consider a closely related problem of distant-k coloring. This problem requires each pair of vertices at geometrical distance of at most k transmission ranges to obtain distinct colors. Although this problem cannot be always solved in the SINR setting, we are able to compute a solution using an optimal number of Steiner points (up to constant factors). We employ this result to devise a local broadcasting algorithm that after a preprocessing stage of O(log∗n⋅(Δ+lognloglogn)) time obtains a local-broadcasting schedule of an optimal (up to constant factors) length O(Δ). This improves upon previous local-broadcasting algorithms in various settings whose preprocessing time was at least O(Δlogn) [3,10,5,]. Finally, we prove a surprising phenomenon regarding the influence of the path-loss exponent α on performance of algorithms. Specifically, we show that in vacuum (α = 2) any local broadcasting algorithm requires Ω(Δlogn) time, while on earth (α > 2) better results are possible as illustrated by our O(Δ+lognloglogn)-time algorithm.
|Title of host publication||Structural Information and Communication Complexity - 22nd International Colloquium, SIROCCO 2015, Post-Proceedings|
|Number of pages||15|
|State||Published - 2015|
|Event||22nd International Colloquium on Structural Information and Communication Complexity, SIROCCO 2015 - Montserrat, Spain|
Duration: 14 Jul 2015 → 16 Jul 2015
|Name||Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)|
|Conference||22nd International Colloquium on Structural Information and Communication Complexity, SIROCCO 2015|
|Period||14/07/15 → 16/07/15|
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© Springer International Publishing Switzerland 2015.