We consider the classical broadcast problem in ad-hoc (that is, unknown topology) directed radio networks with no collision detection, under the additional assumption that at most h transmissions (shots) are available per node. We focus on adaptive deterministic protocols for small values of h. We provide asymptotically matching lower and upper bounds for the cases h=2 and h=3. While for h=2 our bound is quadratic, similar to the bound obtained for oblivious protocols, for h=3 we prove a sub-quadratic bound of Theta(n^2 log log n / log n), where n is the number of nodes in the network. The latter is the first result showing an adaptive algorithm which is asymptotically faster than oblivious h-shot broadcast protocols, for which a tight quadratic bound is known for every constant h. Our upper bound for h=3 is constructive, making use of constructions of graphs with large girth. We also show an improved upper bound of O(n^(1+alpha/sqrt{h})) for h >= 4, where alpha is an absolute constant independent of h. Our upper bound for h >= 4 is non-constructive.
@InProceedings{pagourtzis_et_al:LIPIcs.MFCS.2018.80, author = {Pagourtzis, Aris and Radzik, Tomasz}, title = {{Tight Bounds for Deterministic h-Shot Broadcast in Ad-Hoc Directed Radio Networks}}, booktitle = {43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018)}, pages = {80:1--80:13}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-086-6}, ISSN = {1868-8969}, year = {2018}, volume = {117}, editor = {Potapov, Igor and Spirakis, Paul and Worrell, James}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2018.80}, URN = {urn:nbn:de:0030-drops-96629}, doi = {10.4230/LIPIcs.MFCS.2018.80}, annote = {Keywords: Ad-hoc radio networks, wireless networks, deterministic broadcast, adaptive protocols, limited transmissions} }
Feedback for Dagstuhl Publishing