Graduate School and Research Center in Digital Sciences

Underlay vs. interweave: Which one is better?

Mehmeti, Fidan; Spyropoulos, Thrasyvoulos

Research Report RR-14-296

Cognitive Networks have been proposed to opportunistically discover and exploit licensed spectrum bands, in which the secondary users' (SU) activity is subordinated to primary users (PU). Depending on the nature of the interaction between the SU and PU, there are two frequently encountered types of spectrum access: underlay and interweave. While a lot of research effort has been devoted to each mode, there is no clear consensus aboutwhich type of access performs better in different scenarios and for differentmetrics. To this end, in this paper we approach this question analytically, and provide closed-form expressions that allow one to compare the performance of the two types of access under a common network setup. We focus on two key metrics, delay and throughput, which we analyze using queueing theory and renewal-reward theory. This allows an SU to decide when one type of access technique or the other would provide better performance, as a function of the metric of interest and key network parameters. What is more, based on this analysis, we propose dynamic (hybrid) policies, that can decide at any point to switch from the one type of access to the other, offering up to another 50% of additional performance improvement, compared to the optimal "static" policy in the scenario at hand. We provide extensive validation results using a wide range of realistic simulation scenarios. Index Terms

Document Bibtex

Title:Underlay vs. interweave: Which one is better?
Keywords:Cognitive radio networks,Markov chains, Interweave, Underlay, Queueing
Department:Communication systems
Eurecom ref:4443
Copyright: © EURECOM. Personal use of this material is permitted. The definitive version of this paper was published in Research Report RR-14-296 and is available at :
Bibtex: @techreport{EURECOM+4443, year = {2014}, title = {{U}nderlay vs. interweave: {W}hich one is better?}, author = {{M}ehmeti, {F}idan and {S}pyropoulos, {T}hrasyvoulos}, number = {EURECOM+4443}, month = {11}, institution = {Eurecom}, url = {},, }
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