Rendezvous for Cognitive Radios

Abstract

Abstract-Cognitive radios have been touted as a solution to communicating in a Dynamic Spectrum Access environment. This paper examines how cognitive radios initially find one another among the expanse of ever-changing open spectrum, termed the rendezvous problem. Specifically, it addresses the problem of rendezvous under varying levels of system capabilities, spectrum policies, and environmental conditions. The focus is on rendezvous when there are are no control channels or centralized controllers, which we term the blind rendezvous problem. Under these conditions, a sequence-based and modular clock blind rendezvous algorithms are proposed, and it is shown that the performance of these algorithms compares favorably to that of a random blind rendezvous algorithm. Specifically, the sequence-based algorithm provides a bounded Time To Rendezvous (TTR) and the ability to prioritize channels where rendezvous is more likely to occur; the modular clock algorithm reduces the expected TTR, requires little precoordination among radios attempting to rendezvous, and is robust to radios sensing different sets of available channels.

Optimization of Learning Time for Learning-Assisted Rendezvous Channel in Cognitive Radio System

“…However, the signaling overhead required for informing is huge. Reference [12]- [14] constructs the flexible hopping sequence by removing the channel numbers where the PS's access is sensed. However, Refs.…”

“…However, Refs. [12]- [14] does not obviously show the rule for excluding the channel number. The CR exploits the frequency channel during the temporal vacant period of PS.…”

Quorum system and random based asynchronous rendezvous protocol for cognitive radio ad hoc networks

“…In general, rendezvous approaches can be divided into three branches, first, non-quorum based solutions representing blind or pseudo-random RDV techniques ( [7][8][9] and more sophisticated [10,11]). To the second branch belong protocols proposed for a multichannel Medium Access Control (MAC) handling multi -rendezvous [12] (i.e., multiple transmissions pairs can accomplish handshaking simultaneously), missing receiver problem [13] or medium allocation in a hostile and jamming environment [14].…”

“…Most of them use probabilistic models to generate the channel hopping sequences of the operating CR devices. In the modular clock algorithm (MC) [8] and its modified version MMC [8] each CR node picks a proper prime number P and randomly selects a rate r which is less than P. Based on the two parameters, the user generates its channel search sequence via pre-defined modulo operations. The channel rendezvous sequence (CRSEQ) algorithm [23] uses a method based on triangle numbers and modular operations to calculate the channel hopping order.…”

“…This quorum-based approach generates a significantly greater number of CH sequences than the approach using Latin squares. In the recent study on the blind rendezvous for tactical networks [24], the performances of the MMC [8] and Random Channel Access (RA) [25] algorithms are compared on a testbed using USRP [26]. It is found out that added asynchronism can have a large beneficial effects reducing time to rendezvous.…”