Cellular Uplink Research Articles

Correlated Blocking in mmWave Cellular Networks: Macrodiversity, Outage, and Interference

In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to non-LOS (NLOS). We identify macrodiversity as an important strategy for mitigating blocking, as with macrodiversity the user will attempt to connect with two or more base stations. Diversity is achieved because if the closest base station is blocked, then the next base station might still be unblocked. However, since it is possible for a single blockage to simultaneously block the paths to two base stations, the issue of correlated blocking must be taken into account by the analysis. Our analysis characterizes the macrodiverity gain in the presence of correlated random blocking and interference. To do so, we develop a framework to determine distributions for the LOS probability, Signal to Noise Ratio (SNR), and Signal to Interference and Noise Ratio (SINR) by taking into account correlated blocking. We validate our framework by comparing our analysis, which models blockages using a random point process, with an analysis that uses real-world data to account for blockage. We consider a cellular uplink with both diversity combining and selection combining schemes. We also study the impact of blockage size and blockage density along with the effect of co-channel interference arising from other cells. We show that the assumption of independent blocking can lead to an incorrect evaluation of macrodiversity gain, as the correlation tends to decrease macrodiversity gain.

Stochastic Geometry Modeling of Cellular V2X Communication Over Shared Channels

To overcome the limitations of Dedicated Short Range Communications (DSRC) with short range, non-supportability of high density networks, unreliable broadcast services, signal congestion and connectivity disruptions, cellular vehicle-to-everything (C-V2X) communication networks, standardized in 3rd Generation Partnership Project (3GPP) Release 14, have been recently introduced to cover broader vehicular communication scenarios including vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P) and vehicle-to-infrastructure/network (V2I/N). In C-V2X, vehicles can directly communicate over PC5 based dedicated sidelinks called direct mode or V2V communication. However, high vehicle densities may require reuse of cellular spectrum for V2V. Moreover, infrastructure mode communication through V2I/N links can augment V2V communication by enhancing communication range and reliability for enhanced safety along with consistent performance under traffic congestions. Motivated by the stringent connection reliability, spectral efficiency, and coverage requirements in C-V2X, this paper presents the first comprehensive and tractable analytical framework for performance of C-V2X networks over shared V2V and cellular uplink channels, where the transmitting vehicles can deliver their information via infrastructure or direct mode, based on their distances, propagation environments and the bias factor. By practically modeling the vehicles on the roads using the doubly stochastic Cox process and the base-stations, we derive new association probabilities, new success probabilities of infrastructure and direct mode, and overall success probability of the C-V2X communication over shared channels, which are validated by the simulations results. Our results reveal the benefits of our proposed model (possibility of selecting both direct and infrastructure modes over shared channels) compared to V2V network in terms of success probability.

Multi-Beam UAV Communication in Cellular Uplink: Cooperative Interference Cancellation and Sum-Rate Maximization

Integrating unmanned aerial vehicles (UAVs) into the cellular network as new aerial users is a promising solution to meet their ever-increasing communication demands in a plethora of applications. Due to the high UAV altitude, the channels between UAVs and the ground base stations (GBSs) are dominated by the strong line-of-sight (LoS) links, thus severe interference may be generated to/from the GBSs in the uplink/downlink, which renders the interference management with coexisting terrestrial and aerial users a more challenging problem to solve. In this paper, we study the uplink communication from a multi-antenna UAV to a set of GBSs in its signal coverage region. Among these GBSs, we denote available GBSs as the ones that do not serve any terrestrial users at the assigned resource block (RB) of the UAV, and occupied GBSs as the rest that are serving their respectively associated terrestrial users in the same RB. We propose a new cooperative interference cancellation strategy for the multi-beam UAV uplink communication, which aims to eliminate the co-channel interference at each of the occupied GBSs and in the meanwhile maximize the sum-rate to the available GBSs. Specifically, the multi-antenna UAV sends multiple data streams to selected available GBSs, which in turn forward their decoded data streams to their backhaul-connected occupied GBSs for interference cancellation. To draw useful insights, the maximum degrees-of-freedom (DoF) achievable by the multi-beam UAV communication for sum-rate maximization in the high signal-to-noise ratio (SNR) regime is first characterized, subject to the stringent constraint that all the occupied GBSs do not suffer from any interference in the UAV's uplink transmission. Then, based on the DoF-optimal design, the achievable sum-rate at finite SNR is maximized, subject to given maximum allowable interference power constraints at each occupied GBS.

Interference-aware channel assignment and power allocation for device-to-device communication underlaying cellular network

Device-to-device (D2D) communication is a promising technology in 5G new radio (NR) interface to improve the system performance in terms of high data rate, low latency, coverage extension, traffic offloading, and higher spectrum and energy efficiency. In this study, channel assignment and power allocation techniques for D2D communication underlaying cellular network are proposed, those in turn, lead to a spectrum-efficient system. Firstly, the channel assignment problem is solved by employing channel-characteristics of target link and interference links. Then the power allocation problem is solved by allocating the optimal power to the D2D transmitters with allowable interference. This optimal power allocation approach allows multiple D2D communications to reuse the available cellular uplink resources. Numerical results demonstrate significant throughput gains for D2D communication for different transmission and interference power settings. Network throughput comparison with other existing approaches is provided to confirm the efficacy of the proposed approach. In addition, energy efficiency analysis is carried out by considering D2D transmission power, circuit power consumption, D2D link distance, and D2D user density.

A Resource Allocation Mechanism Based on Weighted Efficiency Interference-Aware for D2D Underlaid Communication.

Device-to-device (D2D) communication is a promising technique for direct communication to enhance the performance of cellular networks. In order to improve the system throughput and utilization of spectrum resource, a resource allocation mechanism for D2D underlaid communication is proposed in this paper where D2D pairs reuse the resource blocks (RBs) of cellular uplink users, adopting a matching matrix to disclose the results of resource allocation. Details of the proposed resource allocation mechanism focused are listed as: the transmit power of D2D pairs are determined by themselves with the distributed power control method, and D2D pairs are assigned to different clusters that are the intended user sets of RBs, according to the threshold of the signal-to-interference-plus-noise ratio (SINR). The weighted efficiency interference-aware (WE-I-A) algorithm is proposed and applied subsequently to promote the system throughput by optimizing the matching of D2D pairs and RBs, where each D2D pair is weighted based on the SINR to compete for the priority of RBs fairly. Simulation results demonstrate that the proposed algorithm contributes to a good performance on the system throughput even if the uplink state is limited.

Energy-efficient power allocation for massive M2M communication over LTE-A cellular uplink

In order to enable massive machine-to-machine (M2M) communication in Long Term Evolution-Advanced (LTE-A) cellular network, a machine-type communication gateway (MTCG) is introduced to solve the issue of control signaling overheads. In this paper, a power allocation algorithm based on the method of Lagrange multipliers is proposed for massive M2M communication over LTE-A cellular uplink. The proposed algorithm can decrease the signaling overheads by enabling the machine-type communication device (MTCD) to access the base station (BS) via a MTCG that collects the data from a group of M2M devices and forward it to the BS. The core objective of the proposed algorithm is to maximize the total energy efficiency of a group of M2M devices, while satisfying the time delay of the M2M devices, by coordinating the power transmission of the MTCDs and the MTCG. The simulation results demonstrate that the proposed algorithm outperforms the heuristic algorithm and has relatively close performance to the optimal design.

Virtual Reality Over Wireless Networks: Quality-of-Service Model and Learning-Based Resource Management

In this paper, the problem of resource management is studied for a network of wireless virtual reality (VR) users communicating over small cell networks (SCNs). In order to capture the VR users' quality-of-service (QoS) in SCNs, a novel VR model, based on multi-attribute utility theory, is proposed. This model jointly accounts for VR metrics such as tracking accuracy, processing delay, and transmission delay. In this model, the small base stations (SBSs) act as the VR control centers that collect the tracking information from VR users over the cellular uplink. Once this information is collected, the SBSs will then send the three dimensional images and accompanying surround stereo audio to the VR users over the downlink. Therefore, the resource allocation problem in VR wireless networks must jointly consider both the uplink and downlink. This problem is then formulated as a noncooperative game and a distributed algorithm based on the machine learning framework of echo state networks (ESNs) is proposed to find the solution of this game. The use of the proposed ESN algorithm enables the SBSs to predict the VR QoS of each SBS and guarantees the convergence to a mixed-strategy Nash equilibrium. The analytical result shows that each user's VR QoS jointly depends on both VR tracking accuracy and wireless resource allocation. Simulation results show that the proposed algorithm yields significant gains, in terms of total utility value of VR QoS, that reach up to 22.2% and 37.5%, respectively, compared to Q-learning and a baseline proportional fair algorithm. The results also show that the proposed algorithm has a faster convergence time than Q-learning and can guarantee low delays for VR services.

Performance Tradeoff in Relay Aided D2D-Cellular Networks

With the explosive growth of multitudinous wireless services and high-data-rate required applications, relay aided Device-to-Device (D2D) communications have attracted increasing attentions. In this correspondence, we investigate the performance tradeoff in relay aided D2D-cellular networks, where D2D users reuse the resource of cellular uplink transmissions. To optimize the performance of relay aided D2D communications, we first study the tradeoff between spectral efficiency (SE) and energy efficiency, and propose a source-relay joint power allocation scheme. The optimal transmit powers for both source and relay users are derived, based on which we further introduce a SE-variation function to explicitly evaluate the impact of enabling D2D communications on D2D-cellular networks. Theoretical analysis and simulation results demonstrate the viability of the proposed scheme and provide comprehensive insights into the coexistence of different systems.

Energy-Efficient Power Allocation and Relay Selection Schemes for Relay-Assisted D2D Communications in 5G Wireless Networks

Device-to-device (D2D) communications allows user equipment (UE) that are in close proximity to communicate with each other directly without using a base station. Relay-assisted D2D (RA-D2D) communications in 5G networks can be applied to support long-distance users and to improve energy efficiency (EE) of the networks. In this paper, we first establish a multi-relay system model where the D2D UEs can communicate with each other by reusing only one cellular uplink resource. Then, we apply an adaptive neuro-fuzzy inference system (ANFIS) architecture to select the best D2D relay to forward D2D source information to the expected D2D destination. Efficient power allocation (PA) in the D2D source and the D2D relay are critical problems for operating such networks, since the data rate of the cellular uplink and the maximum transmission power of the system need to be satisfied. As is known, 5G wireless networks also aim for low energy consumption to better implement the Internet of Things (IoT). Consequently, in this paper, we also formulate a problem to find the optimal solutions for PA of the D2D source and the D2D relay in terms of maximizing the EE of RA-D2D communications to support applications in the emerging IoT. To solve the PA problems of RA-D2D communications, a particle swarm optimization algorithm is employed to maximize the EE of the RA-D2D communications while satisfying the transmission power constraints of the D2D users, minimum data rate of cellular uplink, and minimum signal-to-interference-plus-noise-ratio requirements of the D2D users. Simulation results reveal that the proposed relay selection and PA methods significantly improve EE more than existing schemes.

Optimal Mode Selection Algorithms in Multiple Pair Device-to-Device Communications

Device-to-Device (D2D) communications have been proposed to improve spectrum and energy efficiency of cellular networks. One of the most critical issues in D2D networks is the selection of the communication modes for multiple D2D pairs in a cell. In this article, relay-assisted mode, in addition to basic cellular and direct D2D modes, is taken into account to improve the link performance of D2D pairs. We investigate the optimal mode selection schemes to maximize cell-wise capacity based on the reuse of cellular uplink channels in different multi-pair D2D communication scenarios. We discover that the optimal mode selection problem can be transformed into a linear programming problem with polynomial computational complexity. The exact analytical solutions for optimal mode selection are derived and can be useful to cellular operators to maximize the cellwise capacity.

Cooperative Device-to-Device Communication for Uplink Transmission in Cellular System

The rapid development of the Internet of Things has brought new challenges to cellular networks with super-dense devices and deep-fading channels. These challenges may substantially decrease the transmission efficiency and increase the device’s power consumption, especially in the uplink. A pressing issue is to improve enhanced Node B’s (eNB) scheduler considering a large number of users. In this paper, a semi-centralized cooperative control method is proposed for the cellular uplink transmissions, where the user equipment (UE) relays are randomly selected according to a certain density decided by the eNB. Two specific cooperative schemes based on device-to-device (D2D) communications are proposed, which are the random UE relay scheme and the one further applying network coding. The D2D interference is considered and modeled based on stochastic geometry. The proposed schemes are analyzed based on two distinct traffic models, i.e., the machine type communications traffic with the small-data feature and the full-buffer traffic. Extensive Monte Carlo simulations have been conducted for the small-data traffic and the closed-form theoretical results have been derived for the full-buffer traffic. Performance gains are achieved in various scenarios and the comparisons between two cooperative schemes are made as well. The results provide an important guideline for the eNB to determine how to select and configure cooperative D2D communication for uplink.

Two-stage coalition formation and radio resource allocation with Nash bargaining solution for inband underlaid D2D communications in 5G networks

For D2D communications in the inband underlaid 5G networks, to improve the utilization of cellular uplink spectrum, a two-stage coalition formation and resource allocation scheme is proposed to allocate the radio resources based on the numbers of resource blocks (RBs) requested by D2D pairs. Any set of D2D pairs whose pairwise distances longer than a threshold value are organized into a Stage-1 coalition by the Bron-Kerbosch algorithm. Otherwise, they are organized into Stage-2 coalitions based on the total number of RBs they requested. Since D2D pairs in a Stage-1 coalition are far away from each other, the co-channel interference can be ignored. To improve the RB utilization, RBs that can be used by D2D pairs in the same Stage-1 coalition are first allocated to that Stage-1 coalition. Then, based on the total number of RBs requested by D2D pairs in a Stage-2 coalition, RBs are allocated to Stage-2 coalitions. Since RBs allocated to a Stage-2 coalition cannot be shared by D2D pairs in that Stage-2 coalition, the Nash bargaining solution (NBS) is used to further allocate RBs to D2D pairs in that Stage-2 coalition. Simulation results show that, the proposed two-stage coalition formation and resource allocation scheme allocates more number of equivalent RBs to D2D pairs than the number of RBs allocated by the greedy algorithm. Specifically, based on the simulation results, the total number of equivalent RBs allocated by the proposed scheme can be up to 325.52% of that allocated by the greedy algorithm.

Beam-domain hybrid time-switching and power-splitting SWIPT in full-duplex massive MIMO system

In this paper, we consider the beam-domain hybrid time-switching (TS) and power-splitting (PS) simultaneous wireless information and power transfer (SWIPT) protocol design in full-duplex (FD) massive multiple-input multiple-output (MIMO) system, where the FD base station (BS) simultaneously serves a set of downlink half-duplex (HD) users (cellular users) and a set of fixed uplink HD users (fixed sensor nodes) which are uniformly distributed in its coverage area. In order to reduce the computational complexity, we investigate the beam-domain representation of massive MIMO channels based on the basis expansion model, and then the beam-domain SWIPT protocol which lies in intelligently scheduling the users and sensors based on the beam-domain distributions of their associated channels to mitigate SI and enhance transmission efficiency is designed for full-duplex massive MIMO system. The whole beam-domain hybrid TS and PS SWIPT protocol is divided into two phases based on the ideal of TS. The first phase is used for cellular users uplink training and sensor nodes energy harvesting as well as downlink training, wherein the cellular users transmit uplink pilots for uplink channel estimation at the BS, while the BS simultaneously transmits energy signals to the sensor nodes. Based on the idea of PS, the sensor nodes utilize the received energy signals for energy harvesting and downlink channel estimation. In the second phase, the BS forms the transmit beamformers for information transmission to the users as well as the receive beamformers for the sensors transmit their data to the BS simultaneously. By optimizing the TS ratio and transmit powers at the BS in two phases, the system achievable sum rate performance is maximized. Simulation results show the superiority of the proposed protocol on spectral efficiency compared with the existing massive MIMO SWIPT protocol.

Improving the Coverage and Spectral Efficiency of Millimeter-Wave Cellular Networks Using Device-to-Device Relays

The susceptibility of millimeter waveform propagation to blockages limits the coverage of millimeter-wave (mmWave) signals. To overcome blockages, we propose to leverage two-hop device-to-device (D2D) relaying. Using stochastic geometry, we derive expressions for the downlink coverage probability of relay-assisted mmWave cellular networks when the D2D links are implemented in either uplink mmWave or uplink microwave bands. We further investigate the spectral efficiency (SE) improvement in the cellular downlink, and the effect of D2D transmissions on the cellular uplink. For mmWave links, we derive the coverage probability using dominant interferer analysis while accounting for both blockages and beamforming gains. For microwave D2D links, we derive the coverage probability considering both line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. Numerical results show that downlink coverage and SE can be improved using two-hop D2D relaying. Specifically, microwave D2D relays achieve better coverage because D2D connections can be established under NLOS conditions. However, mmWave D2D relays achieve better coverage when the density of interferers is large because blockages eliminate interference from NLOS interferers. The SE on the downlink depends on the relay mode selection strategy, and mmWave D2D relays use a significantly smaller fraction of uplink resources than microwave D2D relays.

Power Allocation for Maximizing Uplink Rate Over Full-Duplex Relay-Based D2D Communication Underlying Cellular Networks

Device-to-device (D2D) communications, which can increase system throughput, allow two cellular devices to communicate directly with each other. Compared with half-duplex relay, full-duplex relay can significantly improve the spectrum efficiency if the self-interference can be efficiently eliminated. This paper proposes a D2D communication scheme, which assigns the fixed D2D transmitter as full-duplex amplify-and-forward relay to assist cellular uplink transmission. Cellular user close to the fixed D2D transmitter can directly download the video by D2D communications. An optimization problem is formulated to maximize the uplink rate of cellular user while guaranteeing the rate requirement of D2D user. We first obtain the feasible region of the power splitting factor, which characterizes the proportion of fixed D2D transmitter power allocated to cellular uplink and D2D communications. Then, a closed-form expression of the optimal power allocation scheme is derived. Also simulation results are presented to validate the proposed optimal power allocation scheme for uplink rate maximization.

Decentralized Opportunistic Access for D2D Underlaid Cellular Networks

In this paper, we propose a decentralized access control scheme for interference management in device-to-device (D2D) underlaid cellular networks. Our method combines signal-to-interference ratio (SIR)-aware link activation with cellular guard zones in a system, where D2D links opportunistically access the licensed cellular spectrum when the activation conditions are satisfied. Analytical expressions for the success/coverage probability of both cellular and D2D links are derived. We characterize the impact of the guard zone radius and the SIR threshold on the D2D potential throughput and cellular coverage. A tractable approach is proposed to find the SIR threshold and guard zone radius that maximize the potential throughput of the D2D communication while ensuring sufficient coverage probability for the cellular uplink users. Simulations validate the accuracy of our analytical results and show the performance gain of the proposed scheme compared to prior state-of-the-art solutions.

Benchmarking the Robustness of Cellular Up-Links in Automatic Weather Station Networks

We present a problem for benchmarking the robustness of cellular up-links, in an automatic weather station (AWS) testbed. Based on the problem, we conduct a small-scale measurement study of robustness, where the AWS is equipped with four (4) cellular modems for weather data delivery. The effectiveness of up-links is challenging because of overlapping spatial-temporal factors such as the presence of good reflectors that lead to multi-path effects, interference, network load or other reasons. We argue that, there is a strong need for independent assessments of their robustness, to perform end-to-end network measurement. However, it is yet difficult to go from a particular measurement to an assessment of the entire network. We extensively measure the variability of Radio Signal Strength (RSSI) as link metric on the cellular modems. The RSSI is one of the important link metrics that can determine the robustness of received RF signals, and explore how they differed from one another at a particular location and instant time. We also apply the statistical analysis that quantifies the level of stability by considering the robustness, referring short-term variation, and determines good up-link in comparison to weak one. The results show that the robustness of cellular up-links exists for an unpredictable period of time and lower than one could hope. More than 50% of up-links are intermittent. Therefore, we plan to extend our work by exploring RSSI thresholds, to develop a classification scheme supporting a decision whether a link is either intermittent or not. This will help in normalizing the level of stability, to design the RSSI estimation metric for the robust routing protocol in weather data networks.

Performance Analysis of Uplink SCMA With Receiver Diversity and Randomly Deployed Users

This paper considers the performance analysis of sparse code multiple access (SCMA) with receive diversity arrays and randomly deployed users in a cellular uplink scenario. The impact of path loss on the performance of SCMA is characterized, by assuming independent Rayleigh fading and joint maximum likelihood (ML) receivers. A tight upper bound on the probability of symbol detection error is derived, and the achievable diversity and coding gains are investigated. The analytical results are validated by using simulations, and show that a diversity order which is equal to the product of the number of receive antennas and the signal-space diversity can be achieved, and the large-scale path-loss decreases only the coding gain.

Minimizing Uplink Cellular Outage Probability in Interference Limited Rayleigh and Nakagami Wireless Fading Channels

We propose a game theoretic non-cooperative algorithm to optimize theinduced outage probability in an uplink cellular interference limited wireless Rayleighand Nakagami fading channels. We achieve this target by maximizing the certaintyequivalent margin (CEM). We derive a closed-form formula of the outage probabilityin Nakagami flat-fading channels, then we show that minimizing the induced outagefading probability for both Rayleigh and Nakagami channels is equivalent to maxi-mizing CEM. We present a non-cooperative power control algorithm using the gametheory framework. Through this non-cooperative game, we argue that the best de-cision in such an environment is for all users to transmit at the minimum power intheir corresponding strategy profiles. This finding considerably simplifies the imple-mentation of the proposed game.

Relay-Aided NOMA in Uplink Cellular Networks

A new relay-aided non-orthogonal multiple access (NOMA) technique is proposed for multi-cell uplink cellular networks in which each cell supports $K$ single-antenna users by its respective base station (BS) equipped with $N (\ll K)$ antennas. Cooperative relaying transmission is used to accommodate more than one user per orthogonal resource block in the context of interference-limited cellular networks. With the proposed relay-aided NOMA, an Alamouti structure of the desired symbol can further be generated at each BS free of interference, which gives rise to diversity gain of two. The proposed scheme does not require any channel state information (CSI) at users. Further, only limited CSI is required at relays and BSs, which can greatly reduce the control overhead.