What and how much to gain by spectrum agility? (original) (raw)

Opportunistic spectrum access: challenges, architecture, protocols

2006

We consider the concept of opportunistic spectrum access (OSA) -whereby radios identify unused portions of licensed spectrum, and utilize that spectrum without adverse impact on the primary licensees. OSA allows both dramatically higher spectrum utilization and near-zero deployment time, with an obvious and significant impact on both civilian and military communications. We discuss two broad classes of challenges to OSA: spectrum agility, which involves wideband sensing, opportunity identification, coordination and use; and policy agility, which enables regulatory policies to be applied dynamically using machine understandable policies. Focusing on spectrum agility, we present an architecture based on an OSA adaptation layer. We describe protocols for OSA, including a hole information protocol, idle channel selection and use, and an access protocol for the coordination channel. We present a simulation study, discuss insights, and show that even a simple protocol for opportunistic spectrum allocation can provide an order-of-magnitude performance improvement in throughput over a legacy system.

Efficient Spectrum Management: Challenges and Solutions

Cognitive Radio (CR) technology has been proposed in recent years as a revolutionary solution towards more efficient utilization of the scarce spectrum resources in an adaptive and intelligent way. By tuning the frequency to the temporarily unused licensed band and adapting operating parameters to environment variations, cognitive radio technology provides future wireless devices with additional bandwidth, reliable broadband communications, and versatility for rapidly growing data applications. To realize the goal of spectrum aware communication, the CR devices need to incorporate the spectrum sensing, decision, sharing, and mobility functionalities. The main challenge in CRAHNS is to integrate these functions in the layers of the protocol stack, so that the CR users can communicate reliably in a distributed manner over multi-hop/multi-spectrum environment without infrastructure support.. In this book chapter, current research challenges of the CRAHNs are presented. First, spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination.

Opportunistic Spectrum Access: From Theory to Practice

2012

Opportunistic Spectrum Access (OSA) is foreseen as the future of wireless communications. OSA relies on the cognitive radio transceiver that tracks the spectral opportunities over a wide spectrum range (multiple GHz). The cognitive radio should be able to analyze the huge amount of acquired spectral information, decide the best course of action, and reconfigure its transceiver parameters accordingly in a very short time due to the highly dynamic nature of the radio environment. This poses stringent requirements on the hardware and processing power of the transceiver. Despite the recent advances in the radio transceiver technologies, existing radios do not allow for exploiting OSA to its full potential. Furthermore, the absence of a centralized entity that controls the spectrum access decisions in distributed ad-hoc networks makes implementing OSA more challenging. In this article, we experimentally demonstrate the ability of implementing distributed OSA schemes given the practical limitations of existing low-cost transceiver technologies. Furthermore, we evaluate the performance of different OSA approaches.

IEEE 802.11e/802.11k wireless LAN: spectrum awareness for distributed resource sharing

Wireless Communications and Mobile Computing, 2004

Coordinating priorities in wireless medium access is difficult when radio networks operate with contention-based medium access. Contention-based medium access protocols such as listen-before-talk are widely employed today, and for example used in the popular IEEE 802.11 protocol. Contention-based protocols are used for wireless communication in unreliable radio environments such as the unlicensed frequency bands with their typically irregular and unpredictable interferences. However, to support time-bounded traffic with a certain quality of service (QoS) support is extremely difficult, because it requires the knowledge of how aggressive other radio stations, which also contend for radio resources, access the medium. In this contribution, we discuss a new measurement in the IEEE 802.11k draft standard, together with the IEEE 802.11e draft standard for coordinating priorities. By combining the two extensions of IEEE 802.11, we develop an algorithm that allows radio stations to estimate the achievable throughput per radio station (the saturation throughput) in the presence of other radio stations. Our algorithm further allows predicting the saturation throughput per radio station in the presence of other non-802.11 radio networks, because it only relies on the information about how the medium is used by other stations, i.e. for what duration other stations have to sense the medium as idle before initiating transmissions. The algorithm does not require knowledge about the contention-parameters (like, e.g. minimum contention window sizes) used by other radio stations, and only relies on medium sensing information. For this reason, we refer to spectrum awareness in this work. We modify an existing model that was originally developed for calculating the saturation throughput in IEEE 802.11, to calculate the saturation throughput for IEEE 802.11e with one single priority. We then describe a new measurement, which is part of the IEEE 802.11k draft standard. The measurement provides information about medium access probabilities of other radio stations per contention window slots. These probabilities provide the information about how aggressive the medium is utilized by other stations. The probabilities are used in our model for approximating the saturation throughput per station and priority in the presence of other radio stations. As a result, with the help of the new model, a radio station is able to estimate its own expected saturation throughput. The comparison of the model with stochastic simulation stations indicates that our model approximates the saturation throughput per station and priority sufficiently in many scenarios, and hence allows to predict expected saturation throughputs per radio station.

Opportunistic Spectrum Access in Cognitive Radio Network

Foundation of Cognitive Radio Systems, 2012

Cognitive Radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum aware communication paradigm in wireless communications. Such networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse Quality-of-Service (QoS) requirements. Specifically, in Cognitive Radio Ad Hoc Networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, current research challenges of the CRAHNs are presented. First, spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. Moreover, the influence of these functions on the performance of the upper layer protocols are investigated and open research issues in these areas are also outlined. Finally, the proposed tools, and best simulator to solve research challenges in spectrum management are explained. This gives an insight in choosing the suitable tool, and the suitable simulator that fit for solving different challenges.

Opportunistic Spectrum Access in Cognitive Radio Ad Hoc Networks

International Journal of Computer Science Issues, 2014

PREDATOR: A Protocol for Ad-hoc and Brokered Dynamic Spectrum Management

… and Networking Conference, …, 2007

If technological trends are any indication, we are coming upon a future where we will have highly-cognitive transmitters and receivers capable of using many different frequencies, transmission powers, modulation schemes and MAC protocols. Future generations of mobile devices will be able to bid for the spectrum that they require from a broker, or will have ways of automatically reducing interference by negotiation with other devices. Despite the many different algorithms and policies that could be used to support this, to the best of our knowledge, there is currently a lack of a unified protocol to allow negotiation of spectrum for brokered and non-brokered environments. The proposed protocol, PREDATOR (PRotocol for Equitable, Dynamic AllocaTion of Radio spectrum), accommodates both brokered and ad hoc configurations. In this paper, we provide a detailed description of how the protocol works, as well as results from a sample application environment to show its efficacy.

A Spectrum Sharing Framework for Intelligent Next Generation Wireless Networks

2018

The explosive emergence of wireless technologies and standards, covering licensed and unlicensed spectrum bands has triggered the appearance of a huge amount of wireless technologies, with many of them coexisting in the same band. Unfortunately, the wireless spectrum is a scarce resource, and the available frequency bands will not scale with the foreseen demand for new capacity. Certain parts of the spectrum, in particular the license-free ISM bands, are overcrowded, while other parts, mostly licensed bands, may be significantly underutilized. As such, there is a need to introduce more advanced techniques to access and share the wireless medium, either to improve the coordination within a given band, or to explore the possibilities of intelligently using unused spectrum in underutilized (e.g., licensed) bands. Therefore, in this paper, we present an open source SDR-based framework that can be employed to devise disruptive techniques to optimize the sub-optimal use of radio spectrum ...

Spectrum and radio resource management

IEEE Vehicular Technology Magazine - IEEE VEH TECHNOL MAG, 2008

Wireless technologies are rapidly evolving to allow operators to deliver more advanced multimedia services. High-speed packet access (HSPA) for uplink and downlink is seen as an intermediate evolutionary step since the first wave of wideband code division multiple access (WCDMA)-based networks rollout, while evolved universal mobile telecommunications system (UMTS) terrestrial radio access networks (E-UTRAN) are the long term perspective for the Third Generation Partnership Project (3GPP) technology family. Similar paths are drawn from the 3GPP2 around the evolution of code division multiple access 2000 (CDMA2000). Moreover, the IEEE 802 working groups are producing an evolving family of standards, such as 802.11 local, 802.15 personal, 802.16 and 802.20 metropolitan and 802.22 regional area networks.

What and how much to gain by spectrum agility? (original) (raw)

Related papers