QoS-aware distributed spectrum sharing for heterogeneous wireless cognitive networks

This paper presents an alternative to existing dynamic spectrum allocation (DSA) schemes, in a flexible spectrum licensing environment where multiple networks coexist and interfere with each other. The proposed virtually bounded DSA scheme (VBS) takes a different approach to fairly manage the spectrum resources in response to temporal deviation in spectrum demands. In particular, a new concept of dynamic virtual boundary is introduced. Based on this concept, the VBS dynamically adjusts the virtual boundaries of spectrum blocks dedicated for the primary systems to reduce the occurrences where the insertion of guard bands is obligatory and consequently provides better spectral efficiency than existing Fragmented and Contiguous DSA schemes.

Dynamic transmission power based dynamic spectrum allocation (DSA) schemes are extensively adopted in cognitive ratio (CR) networks due to their flexible spectrum access strategies to improve spectrum utility. However such DSAs suffer from high sensitivity to the environment change. Based on the protocol model of wireless communications, a notion of interference threshold (IT) is introduced into the DSA model such that the intricate interactions among CRs can be decoupled and CRs' adaptations only affect the local area. With IT modeling, CRs' strategy profile number turns into finite such that an exhaustive search based IT DSA (ES-IT DSA) scheme is feasible to enumerate all strategy profiles for finding the optimal one. To address the scalability issue in ES-IT-DSA, a suboptimal RGF-IT DSA is developed in virtue of restricted growth function theory. Simulation results concur that the IT based DSA algorithms can keep high spectrum utility while achieving simplicity.

In this paper, we propose a dynamic spectrum allocation (DSA) scheme DeepBlocks at the backdrop of sixth-generation (6G) communication networks that address the challenges of fixed spectrum allocations (FSA). The scheme exploits the advantages of deep-Q-network (DQN) and minimizes the search state explosion through a reward-penalty framework. A dynamic allocation of unallocated resource blocks (RBs) to mobile units (MUs) is carried out and once the allocation of RBs is complete, we integrate blockchain (BC) to record the transactional ledgers. The resource usage of MUs is recorded through smart contracts (SCs). We model the proposed scheme as a convex optimization problem, and subproblems are decomposed into a Pareto-optimal solution via Techebyecheff decomposition. In the simulation, we compare our scheme against FSA, and fifth-generation (5G) based DSA schemes like reinforcement learning (RL), deep neural networks (DNN)-based, and duelling DQN based schemes. The comparative analysis of 6G-DQN is modeled in terms of reward formulation, scalability of 6G-DQN-assisted DSA, and profit scenarios of BC-based allocation through intelligent channel control. The scheme proposes significant findings, with the best fit learning rate of 0.0001, and takes 500 episodes to converge to 60 total resource blocks. The servicing latency of the scheme is 272.4 ms, compared to 2010 ms in the duelling DQN approach. In spectrum allocation, an improvement of 26.32% is observed against non-DQN approaches, and 13.57% in the fairness parameter for spectrum allocation due to BC inclusion. The findings present the scheme efficacy for DSA over the aforementioned conventional approaches.

Allowing Secondary Users (SUs) to access the licensed spectrum without causing harmful interference to the Primary Users (PUs) is crucial in enabling the Cognitive Radio (CR) technology. In order to increase the utilization of the spectrum bands, we propose a Dynamic Spectrum Allocation (DSA) algorithm that integrates both interweave and underlay spectrum access schemes. The proposed algorithm will jointly take into account the geographical locations of the nodes, the correlated shadow fading, the interference between the primary and the secondary networks, the interference between SUs that are transmitting on the same channel, and the communications activity of the users. Moreover, a suboptimal heuristic DSA algorithm that jointly takes into consideration all of the aforementioned issues, while requiring low computational- and time-costs, is developed. Simulation results show that the proposed algorithm provides a good success rate and outperforms classical spectrum allocation algorithms.

This paper presents and evaluates the performance of a temporal dynamic spectrum allocation (DSA) scheme based on the CDMA networks as an alternative to the fixed spectrum allocation (FSA) methods. The paper considers the spectrum allocation between two code division multiple access (CDMA) systems with different time-varying traffic pattern. The traffic pattern is based on the real CDMA traffic data from Daegu urban area in Korea. A proposed algorithm is investigated by the simulation based on CDMA call processing and shows that can produce significant gains for the radio access network (RAN) in DSA.

Dynamic spectrum allocation can improve spectrum efficiency by exploiting the traffic loads variations of multiple wireless network systems, when they share neighboring band. In this study, we use a centralized approach in which a spectrum manager periodically re-allocates spectrum among two networks in a single cell. We propose a two levels model (a spectrum level model and a call level model) to characterize the dynamic spectrum allocation. We have further validated the approximated numerical results by simulations. Numerical and simulation results show that the performances of networks with the dynamic spectrum allocation are better than those with fixed allocation and complete its performance analysis via approximation and iterative approach. Hence, we conclude that our model and scheme can improve Quality of Service (QoS) of wireless networks when spectrum is limited.

Several interference mitigation strategies can be used in LTE networks to meet the consumers' increasing need for faster data speeds. Dynamic Spectrum Allocation (DSA), which maintains spectrum in a converged radio system and distributes it across all participating radio terminals, is one of the most promising solutions. However, the fundamental obstacle to achieving increased network capacities is increased inter-cell interference. The aim of this paper is to analyse the effectiveness of a newly proposed DSA technique by comparing its bit error rate (BER) and throughput (TP) with a typical uplink LTE configuration. To maximise throughput in a heterogeneous network, the suggested DSA technique utilises the Nash Bargaining Solution (NBS) scheme, a cooperative game theory that could correlate with the bit error rate. The software tool GNU Radio, which offers signal-processing blocks to develop softwaredefined radios and signal-processing systems, was used to create the setups. After the simulations were performed, the BER values were recorded and compared, while the TP values were established and computed appropriately. According to the results, the uplink (UL-LTE) architecture with DSA has an improved TP and a lower BER value. As a result, spectral efficiency can also be improved.

At present, the fixed spectrum allocation is the accepted strategy employed by the wireless industry and regulators and a large number of spectrum resources have been wasted because of the traffic load variation in different heterogeneous wireless networks. Through the analysis of recent research about dynamic spectrum allocation (DSA), vertical handoff and multi-mode base stations, the authors have proposed the shared carrier vertical network transformation (SCVNT) algorithm, which is based on minimum total blocking probability (MTBP) or minimum redundant channel difference (MRCD). In order to evaluate the performance of SCVNT, the cellular system model and user mobility model are established, and using fixed channel allocation and dynamic channel allocation in each network, the theoretical analysis and simulation experiments are made in different user mobility conditions, different SCVNT judgment periods and different thresholds of the redundant channel difference. The results indicate that SCVNT can effectively reduce total blocking probability and enhance fairness in heterogeneous wireless networks with good compatibility and applicability.

In order to improve spectrum utilization, dynamic spectrum allocation DSA schemes with interference management have been widely investigated, and a special interest is in the current heterogeneous wireless network HWN environment. In the previous work, the approach that guarantees quality of service for the cell-boundary user is extensively used in the DSA scheme. However, such approach gives a pessimistic result. In this paper, we design a DSA scheme for the HWN system, which adopts relatively accurate interference constraints. First, considering that users may randomly locate over the cell, we propose interference constraints across the cell coverage, in which the interference experienced at a point is controlled below the level suffered when using fixed spectrum allocation in only a single network, and the proportion of the cell area where interference is controlled reaches the required area coverage probability. Then under the interference constraints, we formulate the downlink DSA scheme as a combinatorial optimization problem. As the problem is NP-hard, to reduce the computational complexity, we propose two greedy heuristic algorithms for its solution. Simulation results show that the DSA scheme could improve the total spectrum utility for operators and increase the satisfaction rate of spectrum demands for base stations. Copyright © 2013 John Wiley & Sons, Ltd.

In order to fully utilize scarce spectrum resources, dynamic spectrum allocation becomes a promising approach to increase the spectrum efficiency for wireless networks. However, the collusion among selfish network users may seriously deteriorate the efficiency of dynamic spectrum sharing. The network users' behaviors and dynamics need to be taken into consideration for efficient and robust spectrum allocation. In this paper, we model the spectrum allocation in wireless networks with multiple selfish legacy spectrum holders and unlicensed users as multi-stage dynamic games. In order to combat user collusion, we propose a pricing-based collusion-resistant dynamic spectrum allocation approach to optimize overall spectrum efficiency, while not only keeping the participating incentives of the selfish users but also combating possible user collusion. The simulation results show that the proposed scheme achieves high efficiency of spectrum usage even with the presence of severe user collusion.

For wideband Cognitive Radio (CR) devices, the availability of primary user (PU) activity prediction model can save sensing energy and time, track spectrum variations, reduce switching overhead, improve spectrum usage and lower interference to PU. Using Universal Software Radio Peripheral (USRP) generated data, this paper has verified the superiority of Hidden Semi-Markov model (HSMM) over the conventional HMM in learning and predicting temporal correlations in PU spectral activity under non-geometric distribution of state durations. Numerical simulations further show that in a coordinated multi-SU/PU scenario, compared to the traditional random Carrier Sense Multiple Access (CSMA), the proposed HSMM-dynamic spectrum allocation (DSA) protocol significantly reduces aggregate interference to PU. Depending on the number of SU, there exists a trade-off between “interference-free coexistence with PU” and “self-existence of a large number of SU”. This problem is addressed further by statistically modeling probability of free channels and using it to optimize the number of SU that can be allocated. The proposed scheme outperforms the conventional sensing based dynamic spectrum allocation (DSA) in terms of reduced PU interference, lower spectrum handoff requirements and higher spectrum utilization efficiency. The predictive optimized HSMM-DSA can be used as an additional layer of intelligence for any CR device for efficient spectrum sharing.

Orthogonal Frequency Division Multiple Access (OFDMA) with Dynamic spectrum allocation (DSA) is able to provide a wide range of data rate requirements. This paper is focused on the design of preamble sequences in OFDMA systems with low peak-to-mean envelope power ratio (PMEPR) property in the context of DSA. We propose a systematic preamble sequence design which gives rise to low PMEPR for possibly non-contiguous spectrum allocations. With the aid of Golay-Davis-Jedwab (GDJ) sequences, two classes of preamble sequences are presented. We prove that their PMEPRs are upper bounded by 4 for any DSA over a chunk of four contiguous resource blocks.

Presently a new technology which is highly preferred is wireless ADHOC networks. The traffic of the wireless ADHOC networks day by day is growing up due to this the scarcity problem arises in the available spectrum. The channel resources are allocated in Cognitive Radio Network (CRN) with a Dynamic Access methods of available sensed radio environment. The Dynamic Spectrum Allocation (DSA) is a suitable technique which solves the issue of spectrum scarcity in the CRNs. This DSA will coordinate with the channel access for schedule sensing , release connection etc. when two networks are active at the same moment. Here this research paper provides an analysis of reliable channels exclusively used for CRNs with respect to distribution of license-exempt bands and also determining the potential and limitations of every methods.

We focus on dynamic crosstalk-aware lightpath provisioning in translucent space-division multiplexing (SDM) elastic optical networks, in which spectral super-channels are carried over multi-core fibers (MCFs), distance-adaptive transmission is considered, and back-to-back (B2B) signal regeneration is applied. We aim at establishing lightpaths for connection requests in such a way that the inter-core crosstalk (XT) impairment affecting the quality of lightpaths in the network does not exceed allowable threshold levels. To this end, we propose and analyze a method that is based on per-core static/worst-case XT estimation. This method is implemented in a dynamic XT-aware routing, spatial mode, and spectrum allocation (RSSA) algorithm, which is used to solve the lightpath provisioning problem in an efficient way, such that the bandwidth blocking probability is minimized. The performed extensive simulation experiments in realistic network scenarios show a significant impact of this method on network performance and motivate for its application instead of commonly used per-fiber worst-case XT estimation.

Recently, femtocells (HeNBs) are deployed in heterogeneous network (HetNets) attributable to the addition of coverage, capacity and impeccable spectrum efficiency in private buildings/office complexes surroundings. This unplanned placement of HeNBs creates co-channel interference (CCI) in orthogonal frequency division multiple access (OFDMA). As a result service, disruption occurred at the macrocell user and femtocell user. Therefore, with always expanding interest for frequency spectrum, there is have to make available more resource allocation in order to permit more quantities of unlicensed clients to transmit their signals in the authorized groups. Cognitive-based approaches may increase the spectrum efficiency by sharing resources opportunistically from unlicensed/licensed network. However, spectrum management processes quite difficult, and a lot of chance to occur interference at the cell-edge users. Therefore, a dynamic spectrum allocation scheme is proposed for OFDMA based HetNets. The proposed scheme efficiently reduces the interferences through subchannel detection. To accomplish the CCI mitigation, the proposed scheme is functioning using the energy exposure with group creation algorithm for subchannel detection. Finally, the detected subchannel is allocated through applying power allocation algorithm. The simulation results represent that proposed scheme is able to maximize the spectrum detection and enhanced the spectral efficiency. The improved spectral efficiency recuperates the CCI situation at underlay HetNets.