Joint Radio Resource Management in Cognitive Networks

The IEEE 802.22 is a standard for wireless regional area networks to opportunistically operate in TV bands; however, sharing TV White Space (TVWS) spectrum creates a problem of coexistence because no mechanism is defined for coordinating channel usage among secondary networks. We propose a White Space Resource Sharing mechanism (WSRS) for fixed secondary and mobile IEEE 802.22 networks to improve network coexistence and spectrum efficiency. Based on power control and channel allocation, our mechanism allows the TVWS system to serve vehicular networks in scenarios where there are active secondary fixed networks and no more TVWS channels available for opportunistic usage. Unlike state-of-the-art mechanisms for coexistence in TVWS spectrum, our mechanism allocates resources to vehicles even when the density of fixed nodes and the transmission power of the fixed network cause high interference to the vehicular network. Our results show the offered channel capacity increases up to 50% using the proposed WSRS mechanism compared to the recent IEEE 802.22 standard that does not have a defined TVWS channel sharing mechanism. Furthermore, our WSRS mechanism implements a strategy to protect the fixed secondary network from interference caused by vehicular transmissions while promoting fair usage for both secondary networks.

Spectrum scarcity demands for additional bandwidth where new services can be deployed on. However, today's spectrum allocation leaves almost no bands unallocated. Thus, Cognitive Radio has been studied to bring relief to the lack of spectrum, moving towards a more efficient and dynamic spectrum access. In this domain TV White Space have been proposed as a possible solution to bring new, valuable spectrum for opportunistic services. However, their availability is quite low in highly populated areas, and thus their viability is limited. This is mainly because the availability of TV White Space is typically considered at the rooftop, through two-dimensional propagation models which do not account for possible spectrum re-utilization policies within a building, or in a small-scale area. In this paper, we show that much more communication opportunities can be found when we consider also the third-dimension, i.e. the height from the terrain, and novel per-floor allocation policies. We propose three main contributions in this paper. First, we describe an analytical model through which we derive the number of available spectrum resources for indoor secondary networks, considering PU protection policies in the same building, and in surrounding buildings. Second, we estimate the number of TV Gray Space (TVGS) over realistic scenarios in candidate cities, considering realistic street topology and buildings locations, and we show that this value can be much higher than what reported in the spectrum database. Finally, we investigate co-existence of secondary networks on TVWS, when novel per-floor spectrum sharing models are used.

The explosive growth of capacity-hungry wireless services are presenting challenges to the scarce spectrum resource. Operating LTE systems on TV white space may meet the capacity demand due to the good propagation characteristic. However, according to the decision on World Radiocommunication Conference 2012, TV white space is unable to be used by LTE systems exclusively in the near further in China. Cognitive technologies throw light on sharing TV white space between LTE and TV broadcasting systems. Taking 470– 806 MHz band as an example, the availability of deploying LTE systems on TV white spaces in China is studied in this paper. Firstly, the separation distance from LTE stations to the edge of TV coverage area is calculated. Then, the inter-site distance between TV and LTE stations are figured out using the separation distance and TV coverage radius. Combining the theoretical calculation with the deployment information of both analog and digital TV stations stored in the national station database, simulation results on the capacity distribution of cognitive LTE system in typical cities are given. The simulation results inferred that approximately 67% of TV channels are unused averaged over the cities. This result confirms quantitatively the often-stated expectation that white spaces can be shared by LTE systems to meet the capacity demand as well as improve the spectrum efficiency.

Genetic algorithm for autonomic joint radio resource management in end-to-end reconfigurable systems

TV White Space (TVWS) spectrum utilization is totally a new idea in wireless communication technology. It refers to some portion of TV spectrum that is not used by TV channels and available for other applications. This unused spectrum has been opened up for the free and unlicensed users. This spectrum can be utilized greatly if a noninterference environment is created between the users of this spectrum. Therefore, a coexistence of multiple networks requires interference management. In this paper, an interference management algorithm is developed. It ensures that a network can access the TVWS spectrum without causing interference to other networks. This is done by using three stages. The first stage is for finding the group of networks that will not cause interference to one another. For this graph coloring algorithm is used. The second stage is for assigning different channels to each group of networks. Here, channel assignment gives priority to the user requirement of each group. If any bandwidth is left after second stage, then the third stage is performed where performance of each network will be increased. This is done by considering the number of networks in a group. Simulation results show that the proposed scheme provides better channel assignment along with bandwidth utilization.

TV White Space (TVWS) refers to frequency band reserved only for licensed terrestrial TV broadcasting and is opened to unlicensed use under regulatory conditions. While regulations protect licensed systems from interference, interference among unlicensed systems is left mainly to manufacturers. Consequently, there is a need to develop new coexistence approaches between TVWS networks. Busy tone broadcasting is a coexistence method, which can be used by TVWS networks to announce the selected frequency band is occupied. In this paper, a busy tone based coexistence algorithm is proposed for IEEE 802.11af and IEEE 802.22 networks and analyzed by considering different client distributions experiencing log-normal shadowing, where the exact interfering packet rate and successful packet transmission rate expressions are obtained and validated by simulations for different scenarios. The results show that with the proposed coexistence approach, a WLAN can reliably detect the busy tone signal to change its frequency band and can reduce interference to WRAN. Even if there is no available frequency band for the WLAN, the WRAN still maintains its enhanced successful packet transmission performance. The deployment of the proposed algorithm is important for successful coexistence between cognitive wireless networks, where interference is not regulated, such as in TVWS bands.

Monitoring and sensing of spectrum are becoming more and more important, as the subject of using underused TV White Spaces (TVWS) spectrum by software defined radios (SDR) and cognitive radios is advanced forward towards practical applications. Correctly identifying available TVWS bands is critical for success of TVWS based broadband communications, not causing interference to reception of TV broadcast by TV receivers. This paper discusses side effects encountered with a popular design of a wire discone antenna. AntennaCraft model ST4 is exampled as an inexpensive candidate for spectrum monitoring and sensing in UHF frequency band. The study was done by both simulation and measurements, with well matching results. The candidate antenna was found to introduce notch banded loss in the system sensitivity. The influence of a potential mechanical damage onto the sensitivity of the antenna system has also been considered, and was found to be relatively small, under 3 dB.

The paradigm of cognitive radio recently received considerable interest to address the so called `spectrum scarcity' problem. In the USA, the Federal Communications Commission issued the regulatory for the use of cognitive radio in the TV white space spectrum. The primary objective is the design of cognitive devices able to combine the use of spectrum sensing and GEO-location information with the concept of the cognitive control channel to manage the cognitive devices. The recent standard ECMA-392 defines physical layer techniques and medium access control protocols to enable a cognitive network managed in a fully distributed fashion. In this work, we pursue the design of an efficient medium access control protocol for the cognitive control channel to flexibly and reliably exchange messages inside the cognitive radio network. In particular, we explore how the cognitive devices can raise their awareness of spectrum vacancies of spectrum vacancies by means of sensing when the distributed beaconing defined by ECMA-392 is used. Our main contributions are the following: (1) we propose a proprietary medium access control protocol based on the Standard ECMA-392; (2) we model the behavior of the cognitive radio network by means of an innovative urn model approach, (3) we investigate the access of the cognitive devices to the frequency channels with and without spoofing attacks and (4) we investigate the ability of the cognitive devices to identify frequency holes accounting for perfect and imperfect spectrum sensing, as well as we study the network throughput.

Localization is the enabling technology of geolocation database assisted Cognitive Radio Networks (CRN) in TV White Space (TVWS), as the location is required in the implementation of geolocation database approach by regulators such as FCC and Ofcom. This paper proposes a novel Sensing enAbled Localization and Tracking (SALT) system, which locates Secondary Users (SUs) and tracks their movements. In particular, the system localize SUs based on their measurement of Primary User (PU) signals in the TV spectrum. SALT also uses the SU movement information to dynamically manage the available spectrum with an optimal spectrum allocation algorithm based on the location estimation, so as to maximize the uplink throughput of the entire network. The performance of the proposed localization and tracking algorithm is verified with field measurement data from complex environment through extensive experimentation.

In this paper, we propose a reinforcement learning-based approach for enabling vehicles to make intelligent channel selection choices across TV whitespace spectrum. In order for vehicle communication networks to dynamically access TV whitespace in a secondary manner, it is imperative that these communication systems be capable of coexisting with other types of secondary wireless networks operating within the same frequency range. Consequently, we first propose a TV whitespace channel sharing scheme that would facilitate the coexistence between WLAN, WRAN, and vehicular communication networks. Using the channel utilization variations observed by a collection of mobile vehicular communication systems, we then devised a reinforcement learning-based adaptive channel selection algorithm that employs channel utilization sensing in order to reinforce the decisions made by the vehicular communication system. Moreover, the parameters of the proposed learning approach are adaptively tuned in order to achieve better adaptation to a particular environment. A computer emulation environment composed of actual real-world sensing measurement data and a simulated TV whitespace network is created in order to accurately model the characteristics of future wireless environment, as well as to test the proposed learning-based channel access approach. Experimental results show a significant performance improvement with respect to vehicle communication.

Opportunistic secondary usage of underutilised radio spectrum is currently of great interest and the use of TV White Spaces (TVWS) has been considered for Long Term Evolution (LTE) broadband services. However, wireless microphones operating in TV bands pose a challenge to TVWS opportunistic access. Efficient and proactive spectrum sensing could prevent harmful interference between collocated devices, but existing spectrum sensing schemes such as energy detection and schemes based on Random Matrix Theory (RMT) have performance limitations. We propose a new blind spectrum sensing scheme with higher performance based on RMT supported by a new formula for the estimation of noise variance. The performance of the proposed scheme has been evaluated through extensive simulations on wireless microphone signals. The proposed scheme has also been compared to energy detection schemes, and shows higher performance in terms of the probability of false alarm (P fa ) and probability of detection (P d ).

As a cognitive radio (CR) modulation technique, transform domain communication system (TDCS) has been proposed by utilizing white space spectrum for the network access and achieving low probability of interception (LPI). In the previously reported TDCS- based cognitive radio networks (CRN), however, the non-zero periodic correlation function between any pair of users results in multiuser interference (MUI). In this paper, a novel framework under the CR constraints is presented by employing a two- dimension spreading scheme (i.e., time and frequency domains). We first obtain a class of spreading sequences with almost perfect periodic correlation function for arbitrary spectrum utilization pattern. Then, an universal criteria is presented for synchronous MUI-free CRNs when employing TDCS. Simulation results demonstrate that the proposed TDCS-based CRN architecture is a preferable candidate for distribution wireless networks, such as CR Ad-hoc wireless sensor networks.

It is envisaged that next generation wireless networks (NGWN) will be heterogeneous, consisting of multiple radio access technologies (RATs) coexisting in the same geographical area. In these heterogeneous wireless networks, mobile terminals of different capabilities (heterogeneous terminals) will be used by subscribers to access network services. We investigate the effect of using heterogeneous mobile terminals (e.g. single-mode, dual-mode, triple-mode, etc.) on call blocking and call dropping probabilities in cooperative heterogeneous wireless networks. We develop analytical models for heterogeneous mobile terminals and joint radio resource management in heterogeneous wireless networks. Using a two-class three-RAT heterogeneous wireless network as an example, the effect of using heterogeneous terminals in the network is evaluated. Results show the overall call blocking/dropping probability experienced by subscribers in heterogeneous wireless networks depends on the capabilities of mobile terminals used by the subscribers. In the worst case scenario, when all subscribers use single-mode mobile terminals, each subscriber is confined to a single RAT and consequently, joint radio resource management in heterogeneous wireless network has no improvement on new call blocking and handoff call dropping probabilities. However, in the best case scenario, when all subscribers use three-mode terminals, new class-1 call blocking probability decreases from 0.37 (for 100% single-mode terminals) to 0.05, at the arrival rate of 6 calls per minute. New class-2 call blocking probability also decreases from 0.8 to 0.52. Similarly, handoff class-1 call dropping probability decreases from 0.14 to 0.003, and handoff class-2 call dropping probability decreases from 0.44 to 0.09.

We consider the use of dynamic auctions for coordinating spectrum sharing among secondary users, and propose an online multi-unit, iterative auction mechanism called VERUM that is truthful and efficient (the item is always won by the bidder who values it the most). VERUM is an adaptation of the well known Ausubel's clinching auction [1] to suit the dynamic spectrum sharing context. As a use case for VERUM, we consider TV white space (TVWS) spectrum sharing among home networks, and compare VERUM with two existing efficient and truthful multi-unit spectrum auction schemes, VERITAS and SATYA. Our evaluations, using real distributions of homes in a dense urban neighborhood in London and realistic TVWS spectrum availability maps for the UK, show that VERUM outperforms the other two schemes in terms of revenue, spectrum utilization and percentage of winning bidders.

Due to the heterogeneity and versatility of emerging services and applications in wireless networks, it has been a great challenge on improving the network utility by taking advantage of the spatial and temporal diversity of radio resource consumption. This paper is committed to solving this problem by introducing a service-aware spectrum sharing algorithm (SSA) in a joint radio resource management (JRRM) architecture, where a spectrum pool is adopted for leisure spectrum resource management in heterogeneous wireless networks. Based on an objective utility function, the JRRM unit could optimize the spectrum scheduling decisions for the composing networks with awareness of the related supporting services. Moreover, to facilitate a precise decision process, we illustrate an transmission rate requirement prediction model (TRPM) that is adaptive to the system condition variants to forecast service requests. Experiment results show that the proposed SSA can solidly enhance the system performance in terms of radio resource usage ratio, system throughput, user service access ratio, and eventually achieve better network utility.