In cloud radio access networks (C-RANs), the efficient mapping of remote radio units (RRUs) to baseband units (BBUs) presents persistent challenges, especially in large-scale deployments. These challenges are amplified by the dynamic nature of network loads and the frequency of handoff operations, necessitating solutions that can adapt swiftly to changing conditions. This research introduces an innovative approach to address these challenges through optimized RRU-BBU assignments that balance performance requirements with computational efficiency.In this paper, weighted adaptive load and handoff equilibrium (WHALE) framework, a novel optimization approach that simultaneously addresses handoff optimization and load balancing is proposed. Our prediction framework leverages a hybrid architecture combining long short-term memory (LSTM) networks with generalized autoregressive conditional heteroskedasticity (GARCH) models to achieve robust RRU load forecasting. Experimental results demonstrate the framework’s effectiveness across different scales of deployment. In moderate-scale environments, WHALE significantly outperforms conventional approaches, capturing a substantial proportion of potential handoff transitions while achieving marked reductions in execution time. When scaled to larger deployments, the framework demonstrates substantial improvements in computational efficiency, with execution times reduced by nearly an order of magnitude while maintaining performance parity with genetic algorithm (GA) implementations. The prediction-enhanced variant (WHALE-P) exhibits superior efficiency in handoff optimization performance while demonstrating enhanced load balancing capabilities compared to GA implementations, achieving better solution quality with significantly reduced computational overhead.

Molecular Communication via Diffusion (MCvD) is a prominent small-scale technology, which roots from the nature. With solid analytical foundations on channel response and advanced modulation techniques, molecular single-input-single-output (SISO) systems are one of the most studied molecular networks in the literature. However, the literature is yet to provide sufficient analytical channel modeling on molecular multiple-output systems with fully absorbing receivers, one of the common applications in the area. In this paper, a channel model for molecular single-input-multiple-output (SIMO) systems is proposed for estimating the channel response of such systems. With the model’s recursive nature, the closed-form solution of the channel response of molecular 2-Rx SIMO systems is analytically derived. A simplified model with lower complexity is also presented at a cost of slightly less accurate channel estimation. The models are extended to the molecular SIMO systems with more than two receivers. The performance of the methods are evaluated for several topologies with different parameters, and the accuracy of the model is verified by comparing to computer-simulated channel estimations in terms of quantitative error metrics such as root-mean-squared error. The performance of the simplified model is verified by the amount of deviation, indicating sufficient channel modeling performance with reduced computational power.

In this paper, we develop a novel throughput- maximizing OFDMA scheduler for the multi-user MAC framework for the IEEE 802.11ax networks. The scheduler works both in the downlink and uplink directions and assigns resource units to stations using a linear programming technique considering load of each client, possible resource unit configurations, modulation-coding scheme of each client, and ageing factor of each client's load. The performance of the proposed scheduler has been evaluated using the NS3 simulator and compared against the legacy MAC layer mechanism of IEEE 802.11 protocol (i.e., DCF/EDCA). Simulation results show that our proposed throughput-maximizing scheduler increases the total throughput in the network as well as decrease the average end-to-end delay regardless of the number of stations connected to the access point by prioritizing the traffic of clients connected via high modulation-coding schemes.

Multiple-input multiple-output (MIMO) transmission approaches have been recently considered in the context of molecular communications due to desirable improvements they provide in terms of communication efficiency. Among these methods, molecular index modulation (molecular-IM) schemes yield a significant improvement in throughput and show promising results for future molecular MIMO research. However, existing molecular-IM methods rely on perfect spatial alignment between corresponding antennas, which may not be the case in a possible practical scenario. Motivated by this practical constraint, this study proposes a novel receiver design for molecular-IM. The proposed decoder is an augmented version of the maximum count decoder (MCD) and operates by merging MCD with a simple linear combining technique. Our numerical results show that the proposed approach yields a desirable robustness against antenna misalignments while still maintaining a simplistic receiver structure.

Molecular communication via diffusion (MCvD) is a molecular communication method that utilizes the free diffusion of carrier molecules to transfer information at the nanoscale. Due to the random propagation of carrier molecules, intersymbol interference (ISI) is a major issue in an MCvD system. Alongside ISI, interlink interference (ILI) is also an issue that increases the total interference for the MCvD-based multiple-input-multiple-output (MIMO) approaches. Inspired by the antenna index modulation (IM) concept in traditional communication systems, this paper introduces novel IM-based transmission schemes for MCvD systems. In this paper, molecular space shift keying (MSSK) is proposed as a novel modulation for molecular MIMO systems, and it is found that this method combats ISI and ILI considerably better than the existing MIMO approaches. For nanomachines that have access to two different molecules, the direct extension of MSSK, quadrature MSSK (QMSSK) is also proposed. QMSSK is found to combat ISI considerably well while not performing well against ILI-caused errors. In order to combat ILI more effectively, another dual-molecule-based novel modulation scheme called the molecular spatial modulation (MSM) is proposed. Combined with the Gray mapping imposed on the antenna indices, MSM is observed to yield reliable error rates for molecular MIMO systems.

Inspired by the eye diagram in classical radio frequency (RF) based communications, the MOL-Eye diagram is proposed for the performance evaluation of a molecular signal within the context of molecular communication. Utilizing various features of this diagram, three new metrics for the performance evaluation of a molecular signal, namely the maximum eye height, standard deviation of received molecules, and counting SNR (CSNR) are introduced. The applicability of these performance metrics in this domain is verified by comparing the performance of binary concentration shift keying (BCSK) and BCSK with consecutive power adjustment (BCSK-CPA) modulation techniques in a vessel-like environment with laminar flow. The results show that, in addition to classical performance metrics such as biterror rate and channel capacity, these performance metrics can also be used to show the advantage of an efficient modulation technique over a simpler one.

In this paper, a transfer function that models Molecular Communication via Diffusion (MCvD) between a point transmitter and a fully absorbing circular receiver in an unbounded 2-D environment is analytically derived. The analytical derivation of the transfer function of the 2-D channel in MCvD is proposed for the first time in the literature. The transfer function is obtained by solving the molecule concentration equations around the receiver considering diffusion dynamics, using some initial and boundary conditions, and some reasonable assumptions. Analytical results are compared with the results of Monte Carlo simulations.

Location and power estimation of the radio transmitters is an efficient method of providing the radio environment maps in terms of database size and computation time. In this study, a novel efficient approach for estimating the power and location of active transmitters in the predefined geo‐location is presented and the excellent results of this method are compared with other methods. Then, the raising question about number of required receiver sensors in the network area is discussed and an analytical relation is derived for this purpose. To perform experiment, the authors used distributed receivers in a site and conveyed their collected information about the received power in the specified bandwidth to the fusion centre. The results of this study are verified by both numerical simulations and experimental tests.

In Cognitive Radio Networks medium access becomes more complex due to existence of competitive nodes with different detection and access strategies. Each node in a Cognitive Radio Network can try to utilize all or some of the channels that it detects as unused. Since the available spectrum can be shared selfishly or fairly among the candidate nodes, sharing the spectrum can be seen as a Prisoner's Dilemma Game. In a simple N times repeated Prisoner's Dilemma Game, it is proven that any rational player tends not to cooperate at all. Non-cooperative nodes try to consume all available channels for themselves, which in turn causes more collision and less effective utilization of the available channels. Punishment methods like Tit-For-Tat and Generous Tit-For-Tat are proposed to enforce cooperation according to the nodes' previous actions. However, such harsh punishment algorithms that are based solely on previous actions result in lower utilization when the probability of misbehavior or false positive detection of a cooperative action is high as in the case of cognitive radio networks. This paper proposes a novel protocol (CR-COOP) that provides new incentives for cooperation, forgiveness and punishment based on group communities where certain reputation is needed for joining a community. Through the simulations, the channel utilization of each method is compared and CR-COOP is shown to be more resilient to increased false positive detections. Moreover, smarter selfish nodes that misbehave by exploiting the reputation logic are introduced to the system, and it is shown that even under these circumstances the channel utilization of the CR-COOP is remarkably better than the existing solutions in the literature.

Latest regulations on TV white space communications and trend toward spectrum access through geolocation databases relax the regulatory constraints on cognitive radios. Radio environment map REM is a kind of improved geolocation database and an emerging topic with the latest regulations on TV white space communications. It constructs a comprehensive temperature map of the cognitive radio network operation area by utilizing multi-domain information from geolocation databases, characteristics of spectrum use, geographical terrain models, propagation environment, and regulations. REMs act as cognition engines by building long-term knowledge via processing spectrum measurements collected from sensors to estimate the state of locations without any measurement data. Active transmitter LocatIon Estimation based REM construction technique is proposed and compared with the well-known REM construction techniques such as Kriging and inverse distance weighted interpolation in shadow and multipath fading channels. The simulation results suggest that the LocatIon Estimation based REM construction outperforms the compared methods in terms of RMSE and correct detection zone ratio by utilizing additional information about channel parameters that can be estimated by classical least squares method easily.Copyright © 2013 John Wiley & Sons, Ltd.

In cognitive radio, current trend is to utilize geolocation database for TV bands. Considering more dynamic bands in terms of primary user activity, however, necessitates the use of Radio Environment Map (REM), which is an advanced knowledge base that stores live multidomain information on the entities in the network and the environment. In Cognitive Radio Networks (CRNs), mobile nodes that are capable of measuring the energy of the frequency bands are less capable compared to dedicated sensing nodes in the network. Therefore, deployment algorithm of the dedicated sensor nodes is of great importance and affects the constructed REM interference map quality. We propose a novel deployment algorithm for CRNs that considers user distribution probabilities. Numerical results confirm that the proposed deployment algorithm significantly improves the REM performance. The proposed algorithm is compared with random deployments and it is applied on Kriging and LIvE REM construction techniques.

In this paper, we formulate the energy-efficient cooperative sensing scheduling scheme for a cognitive radio network (CRN) with heterogeneous primary signal-to-noise ratio at each secondary user (SU). In the considered CRN, cognitive base station assigns a set of SUs for each frequency with the aim of minimizing the total energy consumption for sensing while meeting the asserted probability of detection and false alarm requirements by employing cooperation. Sensing duration for a target detection performance increases with degrading channel quality. Thus, an SU with better channel conditions consumes lower energy for sensing. Additionally, an SU also spends energy to switch to the next frequency in its sensing sequence. Our scheduling scheme discovers the appropriate set of SUs for each frequency by considering the sensing and channel switching energy as well as the energy consumed for reporting the sensing outcomes. We also present a polynomial time heuristic, Energy Aware Spectrum sEnsing (EASE) that performs close to the optimal solution.

Dynamic access to spectrum requires detecting the free spaces in close proximity. Since non-cooperative sensing methods cannot satisfy most of the basic requirements, different cooperative sensing algorithms have been proposed to overcome this problem. In the previous works, multiple secondary users cooperate to achieve better primary user detection. However, taking into account the measurements from distant users actually aggravates the detection decision. In this paper, we propose the Zone-based Sensing (ZoneS) method, which is a distributed cooperative sensing method that circumvents the problems that arise from the cooperation between distant nodes. The simulations are performed with different parameters and with majority cooperation rule for the users in each zone. The false alarm, missed detection, blocking and dropping probabilities, and channel utilization are examined to assess the effectiveness of ZoneS. The proposed method enables the utilization of spectrum bands that would be left unused otherwise, while keeping the probabilities of missed detection and false alarm bounded. Furthermore, the coordination among secondary users is achieved without any overhead.

Cooperative spectrum sensing is a key feature to increase sensing probability in Cognitive Radio. However, sensing observations may still be received in error when overhead due to error correction is avoided in bandwidth-limited imperfect reporting channels. This paper presents how decision logics are affected by the imperfect reporting channel. Firstly, we present performance analysis of three hard decision logics, which are Or Logic, 3/N Logic and Majority Logic. Our second analysis focuses on effect of probability of error between the Fusion Center and the Cognitive Radio Nodes. In this analysis, we also analyze two different error recovery methods. Analysis is done under three different channel models, which are Additive White Gaussian Noise Channel, flat fading Rayleigh Channel, and Nakagami Channel.

Abstract Cognitive radio heralds the next step in the evolution of wireless communications. In this paper, an analytical model for infrastructure based cognitive radio systems is proposed, and its performance is evaluated under bursty traffic scenarios in a multiple cell environment. Performance metrics like probabilities of dropping and blocking for primary and secondary users as well as forced termination and forced frequency handoff for secondary users are investigated, and the analytical model is verified with simulations. In addition to the analytical model, a new resource planning method is proposed to compensate for uneven traffic load distribution. The proposed method considers offered traffic, hop count to the heavily loaded cell, and velocity of mobile users during resource planning and performs better in terms of probability of blocking, dropping, and forced termination. The proposed method is promising in balancing the system performance measures, yet there is room for further improvement for finding a closed formula for the proposed analytical model. Copyright © 2010 John Wiley & Sons, Ltd.

Communication via diffusion of molecules is an effective method for transporting information in nanonetworks. In this paper, novel modulation techniques called Concentration Shift Keying (CSK) and Molecule Shift Keying (MSK) are proposed for coding and decoding information of the so-called messenger molecule concentration waves in nanonetworks. The first technique, CSK, modulates the information via the variation in the concentration of the messenger molecules whereas MSK utilizes different types of messenger molecules to represent the information. Using simulation, the performance of these modulation techniques is evaluated in terms of susceptibility to noise and transmission power requirements. The new techniques achieve high channel capacity values, in particular, the MSK technique exhibits more robustness against noise and requires less power.

Providing high bit-rates, WiMAX enables IPTV multicasting for several simultaneous broadcasting channels. WiMAX base stations can offer higher capacity to users with better signal quality values, and more robust but lower capacity modulations to users with worse connection quality. WiMAX Mesh mode allows user equipments to operate in ad-hoc mode, which can be used to relay IPTV channels to users with worse links to the base station and better links to relay users. Rescheduling of streaming multimedia data channels using parallel transmissions allows more users to get IPTV service from the same source and increases throughput.

Cooperative spectrum sensing for dynamic spectrum access to unused licensed spectrum has been proposed as a solution to the spectrum scarcity problem. In this paper, a novel sensing algorithm, Cooperative Sensing with Decision Vector (CSDV), that employs uniform quantizer and a weight vector for global decision logic, is proposed. CSDV method is based on energy detection and performs better than conventional hard decision algorithms such as MAJORITY and M/N in terms of probability of detection and false alarm at the cost of a marginal increase in overhead bits. Probability of detection is maximized for a given probability of false alarm by proposed method via convex optimization. For detailed analysis, CSDV is compared with equal gain combiner scheme, which performs far better than hard decision algorithms, via highest bandwidth requirement. Moreover, robustness of CSDV method to sensing error is analyzed when some nodes always report false decisions to the fusion center.

Overlapping coverage areas of the systems in next generation networks cause high signaling overhead if the users are tracked in multiple systems independently. Selecting the system over which paging can be done is yet another problem. In this paper, we present a general next generation wireless network architecture and propose a location registration scheme that updates the location information only in the relevant subsystems. We also propose an efficient paging scheme that exploits the location information in multiple subsystems. User preferences, network availability, and connection history are considered while determining the subsystems to be used for location registration and paging.

Abstract The validity of the mobility model used to evaluate a cellular network determines the validity of the evaluation. In the literature, unrealistic assumptions on mobility are exercised for the sake of simplicity. In this paper, we present a novel mobility model which is realistic in the sense that it captures themoving‐in‐groups,conscious travelingandinertialbehaviours of the subscribers while respecting thenon‐pass‐throughfeature of structures like households and preserving the autonomy of the subscribers. The mobility and call patterns of the subscribers are determined according to the locus of the subscriber over a real map. Thus, our model allows the subscribers to leave home or arrive home, walk or drive in the streets, get on the highways at specific entry points together with numerous hot and blind spots in the terrain, like city centers and lakes. The call pattern of a subscriber is affected by the type of structure he is in. The model can work on real maps to simulate the mobility patterns in real life. We have evaluated the proposed model against the well‐known way point mobility model. We also analyzed the effect of the mobility model on systems with and without guard channels. Copyright © 2004 John Wiley & Sons, Ltd.

The existence of multiple subsystems complicates connection admission in next generation wireless systems (NGWS) while providing alternatives. The accessibility of the subsystems at the time of connection or handoff request plays a key role in connection admission. In this paper, we propose a connection admission control scheme that selects the subsystem for connection establishment and handoff in NGWS. We also give an analytical model of the connection admission problem in NGWS. Accessibility of the subsystems, availability of the resources, service class, and user preferences are considered while determining the subsystem over which the connection will be setup.