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.

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Type:

Report

Date:

2014-11-07

Department:

Communication systems

Eurecom Ref:

4443