A new dynamic spectrum access scheme based on prioritized secondary data traffics for realistic networking scenarios with finite number of users

In this letter, we carry out analysis to derive the closed form sum rate for a general multi-antenna random beamforming system with an arbitrary but finite number of users. A simple and analytical useful expansion with general utility is first developed to decompose and interpret the probability density function of the selected user's signal-to-interference-plus-noise ratio. By using this decomposition, along with standard integration techniques, the closed form result for the sum rate is obtained. The established result explains the interplay between the system parameters for arbitrary but finite number of users.

In traditional cellular networks with fixed base stations, spectrum access is static and deterministic. However, networks with mobile base stations require dynamic spectrum access so as to avoid interference caused by mobility of a mobile base station. Recently, several dynamic spectrum access schemes using cognitive radio, which opportunistically accesses available spectrums, have been proposed to address the problem. These schemes, in general, sense unused spectrums using cognitive radio functions and allocate them to mobile base stations requesting spectrum. Then, if there is no spectrum available, the mobile base station requesting spectrum bands should drop the request and wait until unused spectrums appear. This will result in significant unfairness with respect to the resource access especially when mobile base stations are densely located. We model the opportunistic spectrum access scheme with a Markov chain and show the unfairness problem. Motivated by the unfairness of the opportunistic scheme, we propose a distributed dynamic spectrum access scheme based on sharing spectrum bands in the time domain, not only to avoid interference caused by the mobility of mobile base stations, but to ensure that all mobile base stations located in the same interference range can fairly access spectrum bands at a certain period in time. The results of numerical analysis and simulation show that the proposed scheme can achieve fairness without degrading the overall network performance compared with a conventional opportunistic spectrum access scheme.

The sustained increase of users and the request for advanced multimedia services are amongst the key motivations for designing new high-capacity cellular telecommunication systems. The proposals that are being pursued by several studies and field implementations consider hierarchical architectures and dynamic resource allocation. A hierarchical cellular communication network is analyzed, taking user mobility into account and exploiting dynamic channel-allocation schemes. In particular, a finite number of users has been considered, moving at different speeds in a geographical region covered by a finite number of cells structured in two hierarchical levels: micro- and macrocells. For such a system, mobility and traffic models have been developed, both based on queueing networks analyzing maximum packing (MP), a dynamic channel-allocation scheme. The obtained results, validated by simulation experiments, allow the evaluation of main system-performance parameters in terms of new-call and handoff blocking probabilities, and forced-termination probability as a function of load and system parameters.

Future cellular mobile communication networks will exploit microcellular architectures and dynamic channel allocation in order to meet the rapidly increasing traffic demand. In this paper, an analytical model has been developed in order to evaluate the performance of maximum packing, a dynamic channel allocation scheme for cellular communication networks. Specifically, a finite number of users has been assumed, moving in a geographical region, covered by a finite set of cells. The considered users are characterized by a variable degree of mobility, which allows both variable sized cells and different user speeds to be analyzed. The model, based on queueing networks, allows the evaluation of the main system performance parameters in terms of blocking probability of new calls, handoff blocking probability, forced termination probability, unsuccessful probability, and throughput. Performance predictions are confirmed by simulation in a wide range of load conditions and user mobility.

This paper investigates a dynamic spectrum access (DSA) scheme for ultra low power sensor networks (ULPSN) in an open spectrum where multiple systems coexist and interfere with each other. Low transmission power and simple communication protocol are significant obstacles for ULPSN to operate in the open spectrum. The DSA has been researched to solve this problem by assuming that coexisting systems can perfectly detect each other. However, this assumption is limited for ULPSN because detection of ULPSN in coexisting system is difficult due to sensitivity limitation of spectrum sensing. As a result, available spectrum is more scarce for ULP system than other coexisting systems. Thus, we derive a new Markov chain model of open spectrum access. Based on the Markov chain mode, we design a DSA scheme to maximize the energy efficiency and investigate the channel access and switch policy of the proposed DSA within the framework of partially observable Markov decision process (POMDP). The simulation results demonstrate that the proposed DSA scheme yields improved energy efficiency and lifetime compared to a random channel selection for ULPSN.

This paper presents a contention resolution scheme for multiple random access based on tree algorithms. The proposed scheme, called dynamic collision resolution (DCR), is a variation of the tree algorithm. Given that plural users are transmitting packets to a shared communication medium, the tree algorithm will divide the transmitting users into n parts upon detecting a collision condition and, in the later retransmission, collisions will only occur in between the users that fall into the same part. It was well known that the optimal value of n is 3 under the condition that n is fixed and the number of users is infinite. The proposed DCR scheme adopts a dynamically change on the value of n for a better contention resolution. The performance is evaluated through the simulation over a finite number of users and the result shows that the DCR scheme gives a non-trivial improvement on the tree algorithms under a moderate number of users.

As a new technology, deep reinforcement learning (DRL) has been applied in many fields of wireless communication in recent years. In this paper, we propose a centralized dynamic spectrum access (DSA) scheme based on DRL and convolutional neural network (CNN). The traditional distributed DSA scheme encounters two important issues, namely, interference suppression for primary users (PU) and interference coordination for secondary users (SU). In order to cope with these two issues, a centralized DSA scheme implemented with deep convolution Q-network is proposed in this paper. Operating with the proposed centralized deep convolution Q-network spectrum access (CDCQSA) algorithm, a central unit (CU) uses DRL to unify the spectrum access actions in the network, allowing multiple SU to share spectrum resources with multiple PU without requiring any prior information. Simulation results show that this proposed scheme improves the channel utilization and reduces the conflict probability between PU and SU while avoiding the collisions between SU as well.

In this paper, we present a machine learning (ML) based dynamic spectrum access (DSA) scheme which can be used in a system in which the primary user (PU) spectrum occupancy can be represented as a sequence of busy (on) and idle (off) periods. We use real world data collected from Long Term Evolution (LTE) systems at two locations for our study. We experiment with different feed forward artificial neural network (ANN) architectures to choose from for our DSA scheme. A simple perceptron based ANN architecture was determined to provide good performance. We compare performance of our ML based DSA scheme with a traditional DSA scheme based on analytical model that uses survival analysis. Our results show that our ML based scheme outperforms the survival analysis based scheme in terms of utilization of idle periods. In terms of probability of interference to the PU, our scheme is better in some configurations and slightly worse in some other configurations.

Dynamic spectrum access (DSA) scheme in Cognitive Radio (CR) can solve the current problem of scarce spectrum resource effectively, in which the unlicensed users (i.e. Second Users, SUs) can access the licensed spectrum in opportunistic ways without interference to the licensed users (i.e. Primary Users, PUs). However, SUs have to vacate the spectrum because of PUs coming, in this case the spectrum switch occurs, and it leads to the increasing of SUs’ delay. In this paper, we proposed a Variable Service Rate (VSR) scheme with the switch buffer as to real-time traffic (such as VoIP, Video), in order to decrease the average switch delay of SUs and improve the other performance. Different from previous studies, the main characteristics of our studying of VSR in this paper as follows: 1) Our study is on the condition of real-time traffic and we establish three-dimension Markov model; 2) Using the internal optimization strategy, including switching buffer, optimizing buffer and variable service rate; 3) As to the real-time traffic, on the condition of meeting the Quality of Service(QoS) on dropping probability, the average switch delay is decreased as well as improving the other performance. By extensive simulation and numerical analysis, the performance of real-time traffic is improved greatly on the condition of ensuring its dropping probability. The result fully demonstrates the feasibility and effectiveness of the variable service rate scheme.

This study proposes a coordinated dynamic spectrum access (DSA) scheme for LTE based on cognitive radio (CR) technology, where a central entity, a Spectrum Policy Server (SPS), performs the spectrum management in a LTE multi-operator heterogeneous network (HetNet). More specifically, the scenario analyzed is based on a system deployment formed by two Mobile Network Operators (MNOs), each operating a macro cell network and a pico cell network. The spectrum allocation for macro base stations (BSs) is fixed, as it is the case in current deployments, while the spectrum for pico BSs is shared among operators and allocated dynamically. Increased throughput with high spectrum efficiency is demonstrated on this paper and simulation results for this scenario are presented.

Dynamic Spectrum Access (DSA) has got tremendous attention and research, but most of the existing dynamic spectrum access schemes assume that all Secondary Users (SUs) are of the same priority. In this paper, prioritized SU traffic is considered. The SU traffic in the system is classified into two priority classes based on Quality of Service (QoS) requirements, namely delay-sensitive SU and delay-insensitive SU. Considering that the higher priority users can preempt the transmission of the lower priority users, we develop the analytical model by applying Preemptive Repeat Priority (PRP) M/G/1 queueing theory. Based on the model, we evaluate the overall system time of the prioritized SUs and separately design different spectrum access strategies for them. The results demonstrate that the proposed dynamic spectrum access schemes can simultaneously reduce the overall system time of SUs with different priority classes significantly.

A dynamic spectrum access strategy based on two channel sensing is proposed for the spectrum access model in multi-channel multi-user scenarios. The strategy reduces the contention of cognitive users to the channel by sensing the dynamic allocation of spectrum channels. The number of the perceptual access channels is adaptively allocated according to the number of access users, and the collision interference to the authorized channel is reduced. Then based on the above model, a hybrid dynamic spectrum access strategy is proposed, and the Overlay/Underlay hybrid access mode is adopted instead of the original single Overlay access mode. By setting the probability threshold to reduce the perception of the channel with lower credibility, the cognitive user adopts the Underlay access mode shared transmission at a lower transmission rate. The simulation results show that the proposed two dynamic spectrum access strategies can effectively reduce the collision probability and improve the network service quality.

Dynamic spectrum access (DSA) schemes allow the users to share spectrum resources by taking advantage of the variations in spectrum demand over time and space. Carrying out dynamic spectrum allocation centrally, however, can be a complex task. For this reason, distributed schemes in which users can access the available channels independently may be preferable to centralized DSA schemes. Cognitive radio systems, which enable user terminals to sense their environment and form their action accordingly, are particularly well-suited for distributed systems. On the other hand, the freedom in distributed schemes gives the users the option to act selfishly, which has decisive effects on system performance. In this paper we consider a distributed multichannel wireless random access system where users selfishly access the channels in the system. We analyze the behavior of the selfish users by modeling the system as a non-cooperative game and we identify all stable operating points (Nash equilibria) of this game. We then compare the performance of this system with a number of cooperative distributed DSA schemes in terms of user utilities. Our results show that the performance of the selfish multichannel random access system can be comparable to cooperative schemes.

Are you involved in designing the next generation of wireless networks? With spectrum becoming an ever scarcer resource, it is critical that new systems utilize all available frequency bands as efficiently as possible. The revolutionary technology presented in this book will be at the cutting edge of future wireless communications. Dynamic Spectrum Access and Management in Cognitive Radio Networks provides you with an all-inclusive introduction to this emerging technology, outlining the fundamentals of cognitive radio-based wireless communication and networking, spectrum sharing models, and the requirements for dynamic spectrum access. In addition to the different techniques and their applications in designing dynamic spectrum access methods, you'll also find state-of-the-art dynamic spectrum access schemes, including classifications of the different schemes and the technical details of each scheme. This is a perfect introduction for graduate students and researchers, as well as a useful self-study guide for practitioners.

Joint power control and spectrum access in cognitive radio networks