Cooperative Cellular Networks Research Articles

An Hybrid Heuristic optimal relay selection strategy for energy efficient multi hop cooperative cellular communication

One of the major constraints for mobile relay networks is energy-efficient communication owing to the restricted battery power of user terminals. Among them, the production method is cooperative cellular networks that focus on enhancing the data rate, network reliability, and network system capacity and also improving the spectrum resources in the Fifth Generation (5 G) networks. Thus, recent research works investigate the selection of mobile relays in vehicular networks and also the relay selection in cooperative communication. Here, the mobile relay is selected by the base station (operator) for every mobile user for reducing the cost with improved data rates and reducing the total transmission power. The selection of relay is performed by considering the benefits or utilities offered to three players such as mobile relay, mobile user, and operator. Conventional relay node selection approaches face challenges regarding reduced network lifetime, delay, increased energy consumption, and collusion attacks. For next-generation wireless networks, both energy efficiency and capacity are vital. To cope with these problems, a new multi-objective derived energy efficient accurate selection of relay in multi-hop cooperative cellular communication in the vehicular network through a hybrid heuristic strategy is implemented. The conventional approaches are utilized for probability-based multi-hop broadcasting for low latency. On the other hand, the major demerits of cellular communication are developing an effective multi-hop communication strategy that generates hidden node problems, and also it decreases the speed of the vehicles and the lack of infrastructure in network topology. Thus, this paper aims to propose a hybrid optimization model to choose the lowest count of multi-hops among the source and destination for the cooperative cellular vehicular communication network. The major issue well thought-out here is accurately choosing the count of hops or relays for appropriate communication, which is carried out through the multi-objective function regarding link reliability, energy consumption, outage probability, mobility factor, and transmission delay of the system. The adoption of the new hybrid algorithm with the aid of the Best Fitness-derived Crow Tunicate Swarm Optimization (BF-CTSO) algorithm is designed as the major contribution for optimally selecting the multi-hops between source and destination in a cooperative cellular communication network. Numerical results show that the proposed energy-efficient cooperative communication system outperforms traditional methods.

Uplink-Downlink Duality Between Multiple-Access and Broadcast Channels With Compressing Relays

Uplink-downlink duality refers to the fact that under a sum-power constraint, the capacity regions of a Gaussian multiple-access channel and a Gaussian broadcast channel with Hermitian transposed channel matrices are identical. This paper generalizes this result to a cooperative cellular network, in which remote access-points are deployed as relays in serving the users under the coordination of a central processor (CP). In this model, the users and the relays are connected over noisy wireless links, while the relays and the CP are connected over noiseless but rate-limited fronthaul links. Based on a Lagrangian technique, this paper establishes a duality relationship between such a multiple-access relay channel and broadcast relay channel, under the assumption that the relays use compression-based strategies. Specifically, we show that under the same total transmit power constraint and individual fronthaul rate constraints, the achievable rate regions of the Gaussian multiple-access and broadcast relay channels are identical, when either independent compression or Wyner-Ziv and multivariate compression strategies are used. The key observations are that if the beamforming vectors at the relays are fixed, the sum-power minimization problems under the achievable rate and fronthaul constraints in both the uplink and the downlink can be transformed into either a linear programming or a semidefinite programming problem depending on the compression technique, and that the uplink and downlink problems are Lagrangian duals of each other. Moreover, the dual variables corresponding to the downlink rate constraints become the uplink powers; the dual variables corresponding to the downlink fronthaul constraints become the uplink quantization noises. This duality relationship enables an efficient algorithm for optimizing the downlink transmission and relaying strategies based on the uplink.

Analysis and Comparison of Different Cooperative Cellular Networks

Analysis and Comparison of Different Cooperative Cellular Networks

Joint optimal resource allocation schemes for downlink cooperative cellular networks over orthogonal frequency division multiplexing carriers

This study concentrates on the study of a downlink cooperative cellular (DCC) network in which an access point is located in the centre of each cell and two relay stations are installed in the border between both sectors of a cell to obtain higher cell-edge throughput. To optimise the network efficiency, a joint optimal subcarrier and power allocation scheme is proposed which initially derives the highest achievable rate for a single-legacy user (LU), then, through further evaluation and analysis, this is generalised to the case of a multiple-LU environment. Next, to maximise the overall throughput and ensure fairness, a multi-objective lexicographical optimisation problem (MLOP) is formulated to maximise the minimum LUs rate while improving the overall throughput. As the proposed MLOP is a mixed-integer non-linear problem, finding optimal solutions is impractical and in general, there is no standard method for optimally obtaining a solution. Hence, two efficient algorithms are introduced in this study. Simulation results confirm that the proposed algorithms achieve a fair and near-optimal performance for the multi-LU DCC network based on two relay channels, which makes them desirable in practice compared to some of the sub-optimal well-known algorithms investigated in this study.

Resource allocation in power domain NOMA‐based cooperative multicell networks

In this paper, we propose a novel resource allocation scheme for non-orthogonal multiple access (NOMA) based cooperative cellular networks where in each cell, two pairs of transmitter-receiver want to communicate via the base station (BS) which serves as a decode-and-forward (DF) relay. In the first hop, the transmitters simultaneously transmit their information and the BS applies joint decoding method. The BS transmits the received information towards the receivers based on NOMA technique. The receivers apply the successive interference cancellation (SIC) where the SIC ordering of receivers is determined based on the direct channel gain. We formulate the resource allocation problem as an optimization problem which is non-convex. To tackle the non-convexity, we adopt the successive convex approximation (SCA) with difference of two concave functions (D.C.) as the approximation technique. We also study the computational complexity of our proposed scheme. Finally, we study the performance of our scheme by simulations and compare it with existing transmission schemes like the orthogonal frequency multiple access (OFDMA) and the case where both of the first hop and the second hop adopt PD-NOMA as well as the case where a special sort of subcarrier pairing is performed between the first and second hops.

Analysis and comparison of different cooperative cellular networks

SummaryThis paper addresses cochannel interference (CCI) in mobile networks. So enhancements of network performance by decreasing CCI are assessed using four diverse interference reduction techniques. These techniques signify traditional sectored fractional frequency reuse (FFR), sectored FFR with beamforming (BF), relay‐assisted (R‐A) sectored FFR, and R‐A sectored FFR with BF technique. Additionally, each BF cooperative technique applies the vertical BF, three‐dimensional (3D) BF, and horizontal BF. Consequently, sectored FFR with BF contains three cases. These cases indicate sectored FFR applies horizontal BF, sectored FFR deploys vertical BF, and sectored FFR uses 3D BF. Furthermore, there are three different arrangements of applying BF in R‐A sectored FFR with BF. These arrangements signify that relay station (RS) employs BF only, base station (BS) uses BF only, and both RS and BS apply BF. Therefore, each arrangement consists of three different cases according to the applied BF technique. Consequently, nine dissimilar cases are considered. Also, a comparison of all cases in different techniques is introduced to enhance the network performance. Analytical treatments are conducted. As a result, closed‐form expressions (CFEs) for worst cases cell‐center user's (CCU's) signal‐to‐interference ratio (SIR), cell‐edge user's (CEU's) SIR, and inner radius (IR) are implemented. These closed forms are used to complete the comparison of all techniques using numerous performance evaluation metrics. The results show, that as unpredicted, the performance of R‐A sectored FFR is close to that of R‐A sectored FFR BF in low SIR threshold and high path‐loss exponent (PLE) ranges. Therefore, R‐A sectored FFR is preferred to be used from the perspectives of network cost and power consumption. Furthermore, vertical BF shows performance close to that of 3D BF in low PLE range. Consequently, using vertical BF is preferable with regard to the energy preservation and network budget. Moreover, it is noticed that BS that applies BF arrangement outperforms other arrangements when vertical or horizontal BF technique is applied. Additionally, the arrangement of both RS and BS that apply BF is superior to the other arrangements when 3D BF is used. But, as expected, it does worse than the others if the other BF techniques are applied. The work results achieve much higher CEU SIR enhancement. Therefore, the probability of outage is decreased. Then, rate of served users by the network is heightened. Accordingly, the total network cost is reduced. So this study advances the network performance while maintaining lower network cost.

Base station assisted relay selection in device-to-device communications

The performance of cooperative cellular networks can be enhanced by using social information of users in the network. This paper presents a social-aware midpoint relay selection scheme that increas...

Base station assisted relay selection in device-to-device communications

The performance of cooperative cellular networks can be enhanced by using social information of users in the network. This paper presents a social-aware midpoint relay selection scheme that increas...

Coordinated multi-cell cooperation with user centric dynamic coordination station

Existing cellular wireless networks are facing fundamental challenges due to the exponential demand of mobile data traffic, the need of higher data rates, user coverage, lowering latency, and minimizing signaling overhead. In order to address these challenges, future cellular networks will require adopting a multi-cell multi-tier cooperative architecture. However, in multi-cell cooperation, the user equipment (UE) needs to estimate the channel state information (CSI) and feed it back to the base station (BS) scheduler for adaptive resource management. This results in a significant increase of signaling overhead and feedback latency into the cooperative networks. These overhead and latency are the two key challenges to achieve gains in coordinated multi-point (CoMP) operation. In this research, we study the control plane protocols for cooperative communications and propose a novel coordination architecture to improve the performance of multi-cell cooperative cellular networks. We examine the performance of the proposed CoMP coordination architecture by performing simulation on different homogeneous and heterogeneous scenarios. Simulations outcome of the multicell cooperative cellular networks show that the proposed coordination architecture has the potential to reduce the signaling overhead and feedback latency compared to conventional methods that eventually will improve the performance of cooperative cellular networks.

Outage and delay performance of content caching in two‐tier cooperative cellular networks

The authors consider a content-centric two-tier heterogeneous cellular network where the macro base stations (MBSs) and small base stations (SBSs) are spread based on two independent Poisson point processes. The set of contents are stored in the MBSs while a subset of the contents which are the most popular are cached in the SBSs. We assume that there is no direct link between the MBSs and the users, and users send their content requests to their nearest SBS. If the SBS has not the requested content, the nearest MBS to the serving SBS serves the user through that SBS. Furthermore, the authors incorporated the automatic repeat request (ARQ)-based transmission with a fixed number of the ARQ rounds, and analyse the delay experienced by users. The authors obtained closed-form expressions for the average outage probability and the average delay in case of successful ARQ transmission. It is shown that the content distribution based on popularity decreases the average outage probability and average delay. Also, it is shown that the transmission from MBS to the user through SBS improves the performance in terms of average outage probability and average delay. Finally, using simulations the authors study the proposed schemes for different network parameters.

Asymptotic Uplink Rates in Cooperative Multiantenna Cellular Networks With Mobiles at General Locations

We consider a user-centric cooperative-cellular network where ${K}$ base stations cooperate to detect the signal from a mobile user in the presence of infinitely many interfering mobiles, using a linear Minimum-Mean-Square-Error (MMSE) receiver. As the number of antennas per base station grows large, it is shown that the uplink spectral efficiency approaches an asymptote that has a simple form, which reveals the relationships between key system parameters. This result generalizes our recently reported findings, which were applicable to mobiles distributed as a Poisson Point Process (PPP), to any model for mobile locations as long as the mobile density exists.

Energy-Efficient Virtual Radio Access Networks for Multi-Operators Cooperative Cellular Networks

5G networks will be characterized by massive densification of base stations (BSs). To minimize the network power consumption due to the increased BS deployment, we leverage emerging paradigms to propose BS energy-saving strategies applicable to 5G networks. We explore the potentials of virtualized radio access and core networks to enable spectrum sharing among mobile network operators (MNOs) by harnessing inter-band non-contiguous carrier aggregation. We propose the sleep-mode with efficient beamformers and spectrum-sharing (SEBS) strategy, which minimizes BS power consumption of cooperative MNOs. The licensed bandwidth of each MNO is partitioned into private and shared bands to provision active BSs with sufficient spectrum resources for serving all UEs. Moreover, an optimization problem is formulated to obtain the optimal intra- and inter-RAN beamforming vectors for efficient BS transmission power and improved user signal reception. Numerical simulations show that the proposed strategies yield significant reductions of total power consumption as compared to other schemes. We present different bandwidth sharing ratio formulations to motivate the cooperation among MNOs by the spectrum-user support trading. We also show that the trading does not always yield a higher spectral efficiency in the cooperative cellular network.

Predicted mobility based profitable relay selection in cooperative cellular network with mobile relays

Cooperative cellular networks is productive approach to improve network system capacity, network reliability, data rate, and also increases the hold of spectrum resources in the fifth generation (5G) networks. For this purpose, selection of a relay in cooperative communication has been widely investigated in the past few years and with research in vehicular network, the selection of mobile relay has been studied. In cooperative communication, operator (base station) assigns mobile relay to each mobile user in order to minimize total transmission power and cost with improved data rates. The relay selection is based upon the utilities or benefits provided to three players, i.e. operator, mobile user (MU) and mobile relay (MR). Incentives must be given to mobile relays to make them cooperate for their utilized resources. Despite much effort that has been made in cooperative communication, mobility of a mobile relay along with selection and defining utility gains for three players involved is still left as an open research problem. In this paper, we propose an auction based scheme for relay selection in cooperative communication. For this purpose, we formulate utilities of three players while considering mobility of a mobile relay. Based on the random waypoint mobility model, a centralized Predicted Mobility Based Profitable Relay Selection Algorithm (PMPRSA) is proposed by using auction theory to select a mobile relay. Performance analysis shows that the proposed PMPRSA selects a mobile relay while providing higher data rate and incentives to all three players for their shared resources.

Uplink NOMA transmissions in a cooperative relay network based on statistical channel state information

Non-orthogonal multiple access (NOMA) has recently attracted a lot of attention as a promising multiple access technology to be used in the fifth generation (5G) cellular networks. In this study, the authors investigate uplink NOMA transmissions in a cooperative cellular network in the presence of frequency selective multipath fading channels. Specifically, two users communicate with the base station simultaneously with existence of a half-duplex relay employing the decode-and-forward scheme to assist the far user. At the transmitting nodes, the power allocation factors are decided based on the statistical channel state information (CSI) rather than perfect CSI, while at the receiving nodes, the decoding order between the users is pre-specified and the effect of imperfect successive interference cancellation implementation is taken into account. Under Rayleigh fading channels, the authors derive the exact ergodic rate for the near user and the upper bound of the ergodic rate for the far user, and present an ad-hoc approach to determine the power allocation factors when the target data rates are given. Simulation results show that NOMA consistently outperforms orthogonal multiple access, however, the performance of uplink NOMA depends heavily on the proper choices of the power allocation factors and the relay location.

A Stochastically Geometrical Poisson Point Process Approach for the Future 5G D2D Enabled Cooperative Cellular Network

Due to recent developments in the cellular communication system, stochastic process implementation is necessary. The cellular communication system exhibits random patterns in various domains, thereby compelling the utilization of stochastic processes to achieve an optimal output. User behaviors with respect to the variable geographical pattern, population density, architecture, data usage, and mobility over various cells are random in nature. Therefore, the stochastic-geometry-based Poisson point process (PPP) technique can be implemented to accurately analyze these random processes in device-to-device (D2D)-based cooperative cellular networks. The stochastic modeling entails the consideration of transmitters and receivers as the elements of stochastic point processes. The hexagonal method is not applicable for the implementation of heterogeneous network topologies, as it is not suitable for topologies, in which the cell size is not fixed. Therefore, a randomly designed heterogeneous network uses stochastic geometry as a viable solution for predicting the probabilistic parameters, including the cell interference, load distribution, coverage probability, base station (BS) mapping, and signal-to-interference-plus-noise ratio (SINR). Moreover, as a network architecture that is based on relay nodes (RNs), cellular and D2D users can be utilized in the domain of homogeneous random models. The associated phenomenon can be considered independent and Poisson. In this paper, the stochastic-geometric-based PPP approach is introduced for modeling the SINR, success probability, ergodic capacity, and outage probability for the D2D-enabled cooperative cellular network. The proposed PPP realistic model utilizes BS, RN, the cellular user (CU), and D2D user positioning method to design an interference-free network. The success probability, ergodic capacity, and outage probability for cellular and D2D users are used as metrics for evaluating the results with respect to various SINR threshold values and node densities. Moreover, the total success probability, ergodic capacity, and outage probability have been calculated for various multiple-input-multiple-output (MIMO) antenna configurations to validate the results. The results confirmed that the proposed PPP model approach outperforms the grid model and conventional multi-antenna ultra-dense network (UDN) approaches.

Stochastic Modeling and Analysis of User-Centric Network MIMO Systems

This paper provides an analytical performance characterization of both uplink (UL) and downlink (DL) user-centric network multiple-input multiple-output (MIMO) systems, where a cooperating BS cluster is formed for each user individually and the clusters for different users may overlap. In this model, cooperating BSs (each equipped with multiple antennas) jointly perform zero-forcing beamforming to the set of single-antenna users associated with them. As compared to a baseline network MIMO systems with disjoint BS clusters, the effect of user-centric clustering is that it improves signal strength in both UL and DL, while reducing cluster-edge interference in DL. This paper quantifies these effects by assuming that BSs and users form Poisson point processes and by further approximating both the signal and interference powers using Gamma distributions of appropriate parameters. We show that BS cooperation provides significant gain as compared to single-cell processing for both UL and DL, but the advantage of user-centric clustering over the baseline disjoint clustering system is significant for the DL cluster-edge users only. Although the analytic results are derived with the assumption of perfect channel state information and infinite backhaul between the cooperating BSs, they nevertheless provide architectural insight into the design of future cooperative cellular networks.

Uplink Performance of Multi-Antenna Cellular Networks With Co-Operative Base Stations and User-Centric Clustering

We consider a user-centric co-operative cellular network, where base stations (BSs) close to a mobile co-operate to detect its signal using a (joint) linear minimum-mean-square-error receiver. The BSs are at arbitrary positions and mobiles are modeled as a planar Poisson point process (PPP). Combining stochastic geometry and infinite-random-matrix theory, we derive a simple expression for the spectral efficiency of this complex system as the number of antennas grows large. This framework is applied to BS locations from PPPs and hexagonal grids and is validated through Monte Carlo simulations. The results reveal the influence of tangible system parameters, such as mobile and BS densities, number of antennas per BS, and number of co-operating BSs on achievable spectral efficiencies. Among other insights, we find that for a given BS density and a constraint on the total number of co-operating antennas, all co-operating antennas should be located at a single BS. On the other hand, in our asymptotic regime, for the same number of co-operating antennas, if the network is limited by the area density of antennas, then the number of co-operating BSs should be increased with a fewer antennas per BS.

Traffic-Aware Energy-Saving Base Station Sleeping and Clustering in Cooperative Networks

We consider energy efficient base station (BS) sleeping and clustering problems in cooperative cellular networks, where clusters of base stations jointly transmit to users. Our key idea of energy saving is to exploit spatio-temporal fluctuation of traffic demand, and use minimal energy to provide achievable data rate only slightly greater than varying traffic demand. However, it is highly challenging to design traffic-aware algorithms without the future traffic demand information. To overcome this difficulty, we develop joint BS sleeping and clustering algorithms using queue instead of the future traffic information. The queue length information captures spatio-temporal mismatch between traffic demand and offered data rate. For BS clustering problem, we propose an optimal algorithm under given BS sleep mode state that has polynomial complexity. We integrate the optimal clustering solution into the sleeping problem, which is a complex combinatorial problem, and develop a joint optimal clustering and sleeping algorithm with reduced complexity compared to the exhaustive search. We also develop a greedy algorithm that finds a near-optimal clustering and sleeping solution with polynomial complexity. Through extensive simulations, we show that the proposed algorithms can save significant energy when traffic load is low.

Optimal Cooperative Wireless Communication for Mobile User Data Offloading

We study the mobile data offloading problem in cooperative cellular networks, in which the cellular base station can offload a fraction of data traffic to its cooperative Wi-Fi networks. Both user satisfaction and benefit are important for the cellular network. Under the case that the cellular network cannot provide sufficient transmission resources, part of data traffic can be offloaded to its cooperative Wi-Fi networks to guarantee the user satisfaction, even though the benefit loss of the cellular network will be incurred. Meanwhile, considering the users are price sensitive, the operators, including cellular and Wi-Fi, can issue an appreciate unit price to attract more users and more traffic requirements to increase their total benefit. In this paper, we intend to design an optimal pricing scheme to maximize the user satisfaction and minimize the benefit losses of the operators simultaneously. First, we formulate the mobile data offloading problem as a joint optimization of “min–max” problem. Then, we convert the problem into a bi-level optimization problem, in which the lower level is to maximize the user satisfaction and the upper level is to minimize the benefit losses of the operators. Since the lower-level problem is convex, a centralized scheme based on the dynamic coordinate search-based method is employed to find the optimal solution of the bi-level problem. In addition, a distributed method is proposed to obtain the near-optimal solution quickly, where one-third-party agent is used to adjust the data traffic allocation. Simulation results show that the proposed method achieves the near-optimal solutions with limited iterations.

Increasing the Capacity of Cellular Network With Nested Deployed Cooperative Base Stations

This paper investigates the capacity of the cooperative cellular networks and proposes to use the 2-D nested deployment on the base stations. Further analysis of sum-rate capacity and spectrum efficiency shows that this approach provides significant improvement. The study leverages the traditional model of regarding the coverage of base stations as the hexagonal blocks and views each hexagon as a macro-cell. One of the theoretical contributions of this paper is to use the invariance in the difference co-array to cover the derive the entire set of the channel fading coefficients. Furthermore, this paper proves the validity of using the average sum-rate capacity to calculate the capacity of the networks in both Rayleigh fading and non-fading channels. We also use simulations to confirm the correctness of the proposed theories from another perspective. As a result, the proposed approach remarkably improves the capacity of the network with the same amount of base stations.