2,709 research outputs found
A Novel Opportunistic Spectrum Sharing Scheme for Cognitive Ad Hoc Networks
Nowadays, wireless ad hoc networks are using a static spectrum allocation which leads to congestion in this spectrum parts as the number of devices increases. On the contrary, a significant portion of the spectrum in licensed band (e.g. TV band) is not utilized. Cognitive radio (CR) is a promising technology to solve the spectrum inefficiency problem in ad hoc networks. Based on CR, the unlicensed (secondary) users will utilize the unused spectrum of the licensed (primary) users in an opportunistic manner. As a result, the average spectrum usage will be increased. However, the sudden appearance of primary users will have a negative impact on the performance of secondary users, since secondary users must evacuate the occupied channel and handoff to another unutilized one. This process continues till an unlicensed user finishes his transmission. We will name this process consecutive spectrum handoff (CSH). In order to increase the performance of CR, the number of consecutive spectrum handoffs should be reduced. In this paper, a novel opportunistic spectrum sharing scheme under a heterogeneous spectrum environment of licensed and unlicensed bands is introduced. In this scheme, the licensed channels will be used as operating channels and the unlicensed channels will be used as backup channels when the primary user appears. Since the unlicensed channels are not interrupted by primary users, no more spectrum handoff is needed
CROSS-LAYER RESOURCE ALLOCATION SCHEME UNDER HETEROGENEOUS CONSTRAINTS FOR NEXT GENERATION HIGH RATE WPAN
International audienceIn the next generation wireless networks, the growing demand for new wireless applications is accompanied with high expectations for better quality of service (QoS) fulfillment especially for multimedia applications. Furthermore, the coexistence of future unlicensed users with existing licensed users is becoming a challenging task in next generation communication systems to overcome the underutilization of the spectrum. A QoS and interference aware resource allocation is thus of special interest in order to respond to the heterogeneous constraints of the next generation networks. In this work, we address the issue of resource allocation under heterogeneous constraints for unlicensed multi-band ultra-wideband (UWB) systems in the context of Future Home Networks, i.e. WPAN. The problem is first studied analytically using a heterogeneous constrained optimization problem formulation. After studying the characteristics of the optimal solution, we propose a low-complexity suboptimal algorithm based on a cross-layer approach that combines information provided by the PHY and MAC layers. While the PHY layer is responsible for providing the channel quality of the unlicensed UWB users as well as their interference power that they cause on licensed users, the MAC layer is responsible for classifying the unlicensed users using a two-class based approach that guarantees for multimedia services a high-priority level compared to other services. Combined in an efficient and simple way, the PHY and MAC information present the key elements of the aimed resource allocation. Simulation results demonstrate that the proposed scheme provides a good tradeoff between the QoS satisfaction of the unlicensed applications with hard QoS requirements and the limitation of the interference affecting the licensed users
A novel opportunistic spectrum sharing scheme for cognitive ad hoc networks
Nowadays, wireless ad hoc networks are using a static spectrum allocation
which leads to congestion in this spectrum parts as the number of devices
increases. On the contrary, a significant portion of the spectrum in licensed band
(e.g. TV band) is not utilized. Cognitive radio (CR) is a promising technology to
solve the spectrum inefficiency problem in ad hoc networks. Based on CR, the unlicensed
(secondary) users will utilize the unused spectrum of the licensed (primary)
users in an opportunistic manner. As a result, the average spectrum usage will be
increased. However, the sudden appearance of primary users will have a negative
impact on the performance of secondary users, since secondary users must evacuate
the occupied channel and handoff to another unutilized one. This process continues
till an unlicensed user finishes his transmission. We will name this process consecutive
spectrum handoff (CSH). In order to increase the performance of CR, the
number of consecutive spectrum handoffs should be reduced. In this paper, a novel
opportunistic spectrum sharing scheme under a heterogeneous spectrum environment
of licensed and unlicensed bands is introduced. In this scheme, the licensed
channels will be used as operating channels and the unlicensed channels will be used
as backup channels when the primary user appears. Since the unlicensed channels
are not interrupted by primary users, no more spectrum handoff is needed
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
A Multi-Game Framework for Harmonized LTE-U and WiFi Coexistence over Unlicensed Bands
The introduction of LTE over unlicensed bands (LTE-U) will enable LTE base
stations (BSs) to boost their capacity and offload their traffic by exploiting
the underused unlicensed bands. However, to reap the benefits of LTE-U, it is
necessary to address various new challenges associated with LTE-U and WiFi
coexistence. In particular, new resource management techniques must be
developed to optimize the usage of the network resources while handling the
interdependence between WiFi and LTE users and ensuring that WiFi users are not
jeopardized. To this end, in this paper, a new game theoretic tool, dubbed as
\emph{multi-game} framework is proposed as a promising approach for modeling
resource allocation problems in LTE-U. In such a framework, multiple,
co-existing and coupled games across heterogeneous channels can be formulated
to capture the specific characteristics of LTE-U. Such games can be of
different properties and types but their outcomes are largely interdependent.
After introducing the basics of the multi-game framework, two classes of
algorithms are outlined to achieve the new solution concepts of multi-games.
Simulation results are then conducted to show how such a multi-game can
effectively capture the specific properties of LTE-U and make of it a
"friendly" neighbor to WiFi.Comment: Accepted for publication at IEEE Wireless Communications Magazine,
Special Issue on LTE in Unlicensed Spectru
- …