A utility-based approach for secondary spectrum sharing

Dashouk Maxim, Alanyali, Alanyali Murat

Description

This paper provides a social welfare framework for coexistence of secondary users of spectrum in the presence of static primary users. We consider a formulation that captures spatial differences in available spectrum while considering general system topologies and utility functions: a collection of wireless sessions is considered under an arbitrary conflict graph that indicates the sessions which cannot transmit simultaneously on a common channel. It is assumed that each session has a utility associated with its spectrum utilization. A carrier sense multiple access-based randomized channel selection technique is considered to maximize the resulting sum of utilities. A measurement-based gradient ascent method is used to improve the channel selection performance and to achieve local maxima of the social welfare. Distributed versions of the method are discussed and shown to outperform previously published work in a variety of simulation scenarios that study effects of primary user presence, varying secondary user density, varying total channel availability.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2011
• Nombre de lectures: 1
• Langue: English

Extrait

Dashouk and AlanyaliEURASIP Journal on Wireless Communications and Networking2011,2011:32 http://jwcn.eurasipjournals.com/content/2011/1/32

R E S E A R C H

A utilitybased approach sharing * Maxim Dashouk and Murat Alanyali

for

secondary

Open Access

spectrum

Abstract This paper provides a social welfare framework for coexistence of secondary users of spectrum in the presence of static primary users. We consider a formulation that captures spatial differences in available spectrum while considering general system topologies and utility functions: a collection of wireless sessions is considered under an arbitrary conflict graph that indicates the sessions which cannot transmit simultaneously on a common channel. It is assumed that each session has a utility associated with its spectrum utilization. A carrier sense multiple access based randomized channel selection technique is considered to maximize the resulting sum of utilities. A measurementbased gradient ascent method is used to improve the channel selection performance and to achieve local maxima of the social welfare. Distributed versions of the method are discussed and shown to outperform previously published work in a variety of simulation scenarios that study effects of primary user presence, varying secondary user density, varying total channel availability.

1 Introduction Recent regulatory proceedings in wireless telecommuni cations offer tremendous potential for efficient spectrum usage via novel operational models of spectrum access. An important legislative development in the US, for an example, is the FCC’s recent release [1] of a part of VHF/UHF band for fixed broadband access systems to address the problem of spectrum scarcity. This develop ment introduces the concept of secondary spectrum users that are allowed to use the spectrum while avoid ing conflicts with primary users, which, in this particular case, are TV broadcast services. Similar primary  sec ondary usage scenarios are also likely to arise due to regulatory reforms that grant full property rights to spectrum licensees, thereby allowing them to provide services in secondary markets. While isolation of primary users is challenging due to the cognitive capabilities imposed on the secondary users, yet another technical challenge arises in how the available spectrum can be shared among secondary users. This latter issue is closely related to the concept of wireless coexistence. However, it poses further com plications due to the spatial variability of available spec trum in the presence of primary users, and due to

* Correspondence: [e-mail] Department of Electrical and Computer Engineering, Boston University, 8 Saint Mary’s Street, Boston, MA 02446, USA

possible heterogeneity of secondary users. Resolution of spectrum access can be addressed by cooperative techni ques that are based on coordinative messaging, or by noncooperative techniques that are based on an eti quette [2]. The former approach requires overtheair messaging or exchange through a backhaul network and it is suitable for homogenous systems. Examples of this approach can be found in [3] that describes a distributed handshake mechanism to share timespectrum blocks, and in [4,5] that propose spectrum sharing techniques for OFDMbased air interfaces. In addition, selfcoexis tence in the IEEE 802.16 WiMax standard [6] and the developing cognitive radiobased IEEE 802.22 standard [7] are based on this approach. Such protocols require tight network synchronization and capability of direct message exchange between parties to coordinate spec trum sharing activities. These assumptions do not hold for heterogeneous systems of technologically incompati ble spectrum users. In heterogeneous systems treating all interference as noise or applying a listenbeforetalk (LBT) technique are often the only available options for spectrum sharing [8]. A common goal in distributed channel selection is to achieve minimal collaborative communication among secondary users. A gametheoretic viewpoint is employed in [9,10] to address the problem of noncoop erative multiradio channel allocation. Chen et al. [11]

© 2011 Dashouk and Alanyali; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.