User Plane Research Articles

Virtual mesh networking for achieving multi-hop D2D communications in 5G networks

In 5G networks, when D2D communications or the quality of a cellular link fails to support data transmission of a terminal, it is indispensable to exploit data transmission opportunities via multi-hop D2D communications. However, to achieve multi-hop D2D communications, two problems need to be solved: 1) A routing and packet forwarding protocol is required to enable terminals to forward data packets across multi-hop D2D or cellular links; 2) This protocol must conform to the existing specifications of D2D communications. To this end, a framework of virtual mesh networking is developed in this paper to support multi-hop D2D communications in 5G networks. More specifically, based on the 5G network architecture, routing and packet forwarding are split into two separate mechanisms in the control plane and the user plane, respectively. In the control plane, base stations collect link and topology information of terminals and then form a virtual mesh network among terminals accordingly. The routing path for end-to-end communications is then determined by a virtual mesh routing algorithm, which also takes into account terminal mobility and link failure. In the user plane, a packet forwarding mechanism is designed to deliver data packets following the routing path as determined by the routing algorithm in the control plane. This mechanism extends but also conforms to the existing specifications of D2D communications. The virtual mesh networking protocol and its underlying algorithms are evaluated via simulations. Performance results demonstrate the effectiveness of multi-hop D2D communications via virtual mesh networking.

Performance Analysis of Cellular Radio Access Networks Relying on Control- and User-Plane Separation

In a cellular radio access network relying on control- and user-plane separation, control base stations (CBSs) form the control plane (CP) and take care of control coverage as well as low-speed data delivery. In contrast, traffic base stations (TBSs) in the user plane (UP) are used for transmitting high-speed data. Based on queuing theory and stochastic geometry, we derive the coverage probability of the CP under non-line-of-sight (NLoS) transmissions, and derive the energy efficiency of the UP under coexisting line-of-sight and NLoS propagation modes. Numerical results show that when the traffic load is high, the coverage probability of the CP increases with the increasing CBSs' data rate or the density of CBSs. We also found that the maximum energy efficiency of the UP can be achieved by optimizing the TBS density while achieving a high area spectral efficiency.

Narrowband Internet of Things (NB-IoT): From Physical (PHY) and Media Access Control (MAC) Layers Perspectives.

Narrowband internet of things (NB-IoT) is a recent cellular radio access technology based on Long-Term Evolution (LTE) introduced by Third-Generation Partnership Project (3GPP) for Low-Power Wide-Area Networks (LPWAN). The main aim of NB-IoT is to support massive machine-type communication (mMTC) and enable low-power, low-cost, and low-data-rate communication. NB-IoT is based on LTE design with some changes to meet the mMTC requirements. For example, in the physical (PHY) layer only single-antenna and low-order modulations are supported, and in the Medium Access Control (MAC) layers only one physical resource block is allocated for resource scheduling. The aim of this survey is to provide a comprehensive overview of the design changes brought in the NB-IoT standardization along with the detailed research developments from the perspectives of Physical and MAC layers. The survey also includes an overview of Evolved Packet Core (EPC) changes to support the Service Capability Exposure Function (SCEF) to manage both IP and non-IP data packets through Control Plane (CP) and User Plane (UP), the possible deployment scenarios of NB-IoT in future Heterogeneous Wireless Networks (HetNet). Finally, existing and emerging research challenges in this direction are presented to motivate future research activities.

Overview of LTE-NR Dual Connectivity

The initial components of New Radio (NR) technology are being discussed within the 3GPP with the aim of not only satisfying the urgent needs of the 5G market but also the long-term requirements that network operators want to provide to customers. An expected solution to start delivering value immediately for the 5G systems is represented by LTE-NR tight-interworking, also known in the 3GPP specifications as EN-DC. With this new network architecture, existing LTE radio and core networks are used as a master entity for mobility management and coverage while adding a new secondary 5G carrier. In this article, we will illustrate the concepts and key features that 3GPP has specified for LTE-NR tight-interworking regarding the control and user plane domains. Our supporting performance evaluations highlight that EN-DC, at least in certain scenarios expected to exist in early deployments, is able to deliver better coverage and capacity compared to standalone LTE and NR technologies deployed alone.

Conceptual Verification of Integrated Heterogeneous Network Based on 5G Millimeter Wave Use in Gymnasium

Aiming at the problem that the optical link may be too expensive or even impossible to achieve in a large number of locations in the central part of the backhaul line, the proof-of-concept (PoC) verification of a millimeter-wave integrated heterogeneous network (HetNet) is proposed. HetNet includes a traditional macrocell network and a new small unit that uses a millimeter wave for backhaul line and link access. The concept of a segmentation control plane and user plane was introduced. In the HetNet integrated millimeter wave, the control plane and the user plane were segmented to support the uninterrupted connection and enhance the capacity of the millimeter wave small base station. Millimeter wave communication could be used not only for access links, but also for wireless backhaul links, which will facilitate the installation of small millimeter wave cells. Through conceptual verification (PoC), the feasibility of millimeter-wave integrated HetNet prototype with millimeter wave technology used for return lines and link access is proved.

A Satellite LTE Delay Tolerant Capabilities Tunnelling: Design and Performance Evaluation

This paper presents basic considerations regarding IP-based tunneling support for transmissions for 4G-LTE communication networks that will pass satellite transmissions. In this paper, a delayed tolerance approach to traffic management in LTE via satellite links will be presented. Contribution to this paper will generate quality of service values on satellite communications by bringing 4G-LTE data traffic. We design, implement and evaluate the performance of transport protocol solutions based on the GRE RFC 1701 architecture in the LTE-satellite system. Our paper proposal, is (i) analyzing the current performance and design and implementing it for 4G via satellite using IP tunneling (ii) utilizing the GRE RFC 1701 standards, which creates an ethernet tunnel between two sending data communications on VLAN User Plane, MME and OAM in 4G. The resulting value parameters are throughput index, delay, and performance bandwidth and packet loss. The parameter values generated are Index ∑ Throughput (bit/s) number of data reaching the allocated bandwidth of 6836 Kbps, bandwidth utilization Index = ∑ bandwidth utilization inbound and outbound reaches 100% and packet loss value the resulting one is 0% on transmission connectivity.

A Flexible Network Architecture for 5G Systems

In this paper, we define a flexible, adaptable, and programmable architecture for 5G mobile networks, taking into consideration the requirements, KPIs, and the current gaps in the literature, based on three design fundamentals: (i) split of user and control plane, (ii) service-based architecture within the core network (in line with recent industry and standard consensus), and (iii) fully flexible support of E2E slicing via per-domain and cross-domain optimisation, devising inter-slice control and management functions, and refining the behavioural models via experiment-driven optimisation. The proposed architecture model further facilitates the realisation of slices providing specific functionality, such as network resilience, security functions, and network elasticity. The proposed architecture consists of four different layers identified as network layer, controller layer, management and orchestration layer, and service layer. A key contribution of this paper is the definition of the role of each layer, the relationship between layers, and the identification of the required internal modules within each of the layers. In particular, the proposed architecture extends the reference architectures proposed in the Standards Developing Organisations like 3GPP and ETSI, by building on these while addressing several gaps identified within the corresponding baseline models. We additionally present findings, the design guidelines, and evaluation studies on a selected set of key concepts identified to enable flexible cloudification of the protocol stack, adaptive network slicing, and inter-slice control and management.

Anticipatory Session Management and User Plane Function Placement for AI-Driven Beyond 5G Networks

In this paper we aim at facilitating the flexible 5G core network architecture with foresighted session management. To achieve this we propose a 5G-native architecture utilizing a three-stage learning approach, which covers the dimensions of interest to manage sessions in a foresighted manner. In this perspective we exploit the 5G concepts of per-user mobility and activity patterns, apply our CODIPAS RL Framework to anticipate the user behavior and network requirements, and utilize the outcome for learning-based network optimization on the session level and transport network stretch utilizing our Learning of Learning approach. We further contribute with a model that exploits the foresighted session management approach by utilizing the prediction of user behavior for optimized intermediate User Plane Function (iUPF) placement.

Testbed for ICN media distribution over LTE radio access networks

Information-centric networking (ICN) is one of the most promising research topics for the future Internet. ICN aims at circumventing several issues of current Internet protocol (IP) solutions such as efficient multimedia distribution. Given the huge growth rate of video transmission over mobile networks, it is sensible to consider how 4G/5G networks can leverage on ICN. There is a substantial body of work considering ICN for fixed networks and also for the core of mobile networks. Less attention has been dedicated to ICN on the radio access network (RAN) or ICN-RAN, which has currently a user plane based on many connection-oriented protocols. To fully benefit from ICN, mobile networks must enable it on the RAN, not only on the core. This work details an ICN deployment on the RAN of fourth and fifth generation of mobile networks (4G/5G) and also presents a testbed that enables proofs of concept of this ICN-RAN using 4G. Complementing theoretical and simulation-based works, such testbeds are essential for a technology that aims to be adopted in a scenario with a vast number of well-established (IP-based) legacy solutions. A couple of applications for the testbed are demonstrated: low-latency and real-time applications and video distribution. The results indicate, for example, that evolving ICN features can be tested with currently available tools, but the lack of hardware accelerators and optimized code limit the bit rate that can be achieved in real-time processing.

Performance of Splitting LTE-WLAN Aggregation

LTE-WLAN aggregation (LWA) combines the radio resources of LTE and WLAN to take advantage of Wi-Fi’s high availability and indoor coverage, which provides better usage of both WLAN and LTE. In LWA, a user data radio bearer (DRB) is split if its packets are delivered through both LTE and Wi-Fi. For a split DRB, it is important to determine the LTE-to-WLAN ratio (LWR) or the ratio of packets delivered by LTE over WLAN. Based on WLAN’s Received Signal Strength Indicator (RSSI), we propose a simple LWR selection rule. Using this rule, we describe a user plane implementation for LWA, where the adaptive LWA routing procedure can be easily implemented in the Radio Resource Management (RRM) and the Packet Data Convergence Protocol (PDCP) layer at the LTE eNB. In our implementation, the maximum LWA throughput is 99.14 percent of the optimal cases, and the packet loss rates are less than 0.0042 percent.

Mosaic5G

Network slicing is one of the key enablers to provide the required flexibility and to realize the service-oriented vision toward fifth generation (5G) mobile networks. In that sense, virtualization, softwarization, and disaggregation are core concepts to accommodate the requirements of an end-to-end (E2E) service to be either isolated, shared, or customized. They lay the foundation for a multi-service and multi-tenant architecture, and are realized by applying the principles of software-defined networking (SDN), network function virtualization (NFV), and cloud computing to the mobile networks. Research on these principles requires agile and flexible platforms that offer a wide range of real-world experimentations over different domains to open up innovations in 5G. To this end, we present Mosaic5G, a community-led consortium for sharing platforms, providing a number of software components, namely FlexRAN, LL-MEC, JOX and Store, spanning application, management, control and user plane on top of OpenAirInterface (OAI) platform. Finally, we show several use cases of Mosaic5G corresponding to widely-mentioned 5G research directions.

Effects of C/U Plane Separation and Bearer Aggregation in Mobile Core Network

In response to the growing demand for cellular networks, it is essential to improve the capacity of mobile core networks. Especially, in terms of accommodating machine-to-machine/Internet-of-Things (M2M/IoT) terminals into cellular networks, the load on the control and the user planes of the mobile core network increases massively. To deal with this problem, it is possible to apply virtualization technologies, such as software-defined network and network function virtualization. However, few existing studies evaluate such solutions for mobile core networks numerically and in detail. In this paper, we first evaluate mobile core network architectures with virtualization technologies and control/user (C/U) plane separation using the mathematical analysis. We also propose a novel bearer aggregation method to reduce the control plane load to accommodate massive M2M/IoT terminals. The result of numerical evaluation shows that the capacity of the mobile core network can be increased by up to 32.8% with node virtualization and C/U plane separation, and further by 201.4% by using bearer aggregation. Moreover, to maintain the performance of the mobile core network, we should carefully determine where the bearer aggregation is applied and when the shared bearer for each terminal is determined based on application characteristics and the number of accommodated M2M/IoT terminals.

Coalitional Game for the Creation of Efficient Virtual Core Network Slices in 5G Mobile Systems

Many ongoing research activities relevant to 5G mobile systems concern the virtualization of the mobile core network, including the evolved packet core (EPC) elements, aiming for system scalability, elasticity, flexibility, and cost-efficiency. Virtual EPC (vEPC)/5G core will principally rely on some key technologies, such as network function virtualization, software defined networking, and cloud computing, enabling the concept of mobile carrier cloud. The key idea beneath this concept, also known as core network as a service, consists in deploying virtual instances (i.e., virtual machines or containers) of key core network functions [i.e., virtual network functions (VNF) of 4G or 5G], such as the mobility management entity (MME), Serving GateWay (SGW), Packet Data network gateWay (PGW), access and mobility management function (AMF), session management function (SMF), authentication server function (AUSF), and user plane functions, over a federated cloud. In this vein, an efficient VNF placement algorithm is highly needed to sustain the quality of service (QoS) while reducing the deployment cost. Our contribution in this paper is twofold. First, we devise an algorithm that derives the optimal number of virtual instances of 4G (MME, SGW, and PGW) or 5G (AMF, SMF, and AUSF) core network elements to meet the requirements of a specific mobile traffic. Second, we propose an algorithm for the placement of these virtual instances over a federated cloud. While the first algorithm is based on mixed integer linear programming, the second is based on coalition formation game, wherein the aim is to build coalitions of cloud networks to host the virtual instances of the vEPC/5G core elements. The obtained results clearly indicate the advantages of the proposed algorithms in ensuring QoS given a fixed cost for vEPC/5G core deployment, while maximizing the profits of cloud operators.

Energy Efficiency and Delay in 5G Ultra-Reliable Low-Latency Communications System Architectures

Emerging 5G URLLC wireless systems are characterized by minimal over-the-air latency and stringent decoding error requirements. The low latency requirements can cause conflicts with 5G EE design targets. Therefore, this work provides a perspective on various trade-offs between energy efficiency and user plane delay for upcoming URLLC systems. For network infrastructure EE, we propose solutions that optimize base station on-off switching and distributed access network architectures. For URLLC devices, we advocate solutions that optimize EE of discontinuous reception (DRX), mobility measurements, and the handover process, respectively, without compromising on delay.

5G for Ultra-Reliable Low-Latency Communications

The articles in this special section focus on fifth generation (5G) mobile communication for ultra-reliable low-latency communications. With the expected superior performance to the current generation of mobile networks, 5G systems are poised to support new and diverse usage scenarios and applications, thus enriching the lives of citizens and the productivity of industry and public sectors. The widely accepted scenarios for 5G include enhanced mobile broadband (eMBB), addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable low-latency communications (URLLC) with strict requirements, especially in terms of latency and reliability; and massive machine type communications (mMTC) for a very large number of connected devices typically transmitting a relatively low volume of non-delay-sensitive data. The articles in this section present the most relevant scenarios, prominent research outcomes, and state-of-the-art advances of 5G systems for URLLC achieving the Third Generation Partnership Project (3GPP) targets on latency and reliability requirements to successfully deliver delay-sensitive information. In 3GPP, the performance target for control plane latency is 10 ms, and for user plane latency it is 0.5 ms for downlink and uplink directions, separately.

MIoT Slice for 5G Systems: Design and Performance Evaluation.

Network slicing is a key feature of the upcoming 5G networks allowing the design and deployment of customized communication systems to integrate services provided by vertical industries. In this context, massive Internet of Things (mIoT) is regarded as a compelling use case, both for its relevance from business perspective, and for the technical challenges it poses to network design. With their envisaged massive deployment of devices requiring sporadic connectivity and small data transmission, yet Quality of Service (QoS) constrained, mIoT services will need an ad-hoc end-to-end (E2E) slice, i.e., both access and core network with enhanced Control and User planes (CP/UP). After revising the key requirements of mIoT and identifying major shortcomings of previous generation networks, this paper presents and evaluates an E2E mIoT network slicing solution, featuring a new connectivity model overcoming the load limitations of legacy systems. Unique in its kind, this paper addresses mIoT requirements from an end-to-end perspective highlighting and solving, unlike most prior related work, the connectivity challenges posed to the core network. Results demonstrate that the proposed solution, reducing CP signaling and optimizing UP resource utilization, is a suitable candidate for next generation network standards to efficiently handle massive device deployment.

Coverage and Handover Analysis of Ultra-Dense Millimeter-Wave Networks With Control and User Plane Separation Architecture

The control and user plane separation (CUPS) architecture becomes more appealing for higher mobility profiles with the densification of networks. Compared with the conventional architecture where the control plane and the user plane are closely coupled, CUPS architecture is envisioned to provide enhancement for networks in a flexible way, e.g., reducing latency on application service, while not affecting the functionality of the existing base stations (BSs). In this paper, we compare the performance of ultra-dense millimeter-wave networks with the CUPS architecture and the conventional architecture. An analytical framework is proposed to study the coverage probability, which takes the propagation characteristic of millimeter wave into consideration. The proposed framework is then simplified in an ultra-dense scenario, where two optimization problems are formulated to achieve the minimum handover cost subject to a certain coverage probability requirement. Numerical results show that the CUPS architecture outperforms the conventional architecture in terms of the coverage probability as well as the handover cost. Moreover, new insights are obtained on the deployment of ultra-dense millimeter-wave networks. To be specific, the handover cost of networks with the conventional architecture can be effectively reduced by adding more macrocell BSs, while it is beneficial to add smaller cell BSs into networks with the CUPS architecture.

Scalable Intelligence-Enabled Networking with Traffic Engineering in 5G Scenarios for Future Audio-Visual-Tactile Internet

In order to improve future network performance, this paper proposes scalable intelligence-enabled networking (SIEN) with eliminating traffic redundancy for audio-visual-tactile Internet in 5G scenarios, such as enhanced mobile broadband, ultra-reliable and low latency communication, and massive machine-type communication. The SIEN consists of an intelligent management plane (ImP), an intelligence-enabled plane (IeP), a control plane, and a user plane. For the ImP, the containers with decision execution are constructed by a novel graph algorithm to organize objects such as network elements and resource partitions. For the IeP, a novel learning system is designed with decision-making using a congruity function for generalization and personalization in the presence of imbalanced, conflicting, and partial data. For the control plane, a scheme of identifier-locator mapping is designed by referring to information-centric networking and software-defined networking. For the user plane, the user-related traffic, which may include identifiers, registrations, requests and named data objects, is forwarded to implement the SIEN and test its performance. The evaluation shows the SIEN outperforms four state-of-the-art techniques for redundant traffic reduction by up to 46.04% based on a mix of assumption, simulation, and proof-of-concept implementation for audio-visual-tactile Internet multimedia service. To confirm the validity, the best case and the worst case for traffic offloading are tested with the data rate, latency, and density. The evaluation only focused on the scalability issue, while the SIEN would be beneficial to improve more issues such as inter-domain security, ultra-low latency, on-demand mobility, multi-homing routing, and cross-layer feature incongruity.

Performance Evaluation of a Live Multi-Site LTE Network

In this paper, to quantify the field performance of a live long term evolution (LTE) network, we design and implement a multi-layered performance monitoring system. This monitoring system delivers an accurate and thorough picture of the network behavior including switching, cellular, transmission, IP, and data networks. The designed system enables measurement results gathered from different network layers and from both user and control planes through a mediation platform, paving the way for the collection of synchronous performance measurement results, including latency, handover ratios, and throughput from network entities. Network performance metrics and the terminal-based measurement are jointly reported to reflect the subscriber perspective. Two field trials are conducted to highlight performance results of LTE networks, in a congested multi-cell with release 12 support, and a sparsely populated cell with release 14 support. Different multiple-input multiple-output (MIMO) configurations, including spatial multiplexing, transmit diversity, beamforming, and $64\times 64$ massive MIMO support, along with a selection of bandwidths and frequency bands are considered. The measurement results show that, without any significant latency cost, using more antenna elements provides higher user throughput, which also affects the overall cell throughput. However, doubling the number of antennas may not necessarily double the average data rates. Additionally, the average intrafrequency and interfrequency handover success ratios are observed to be acceptable, hence the changes among the selected the diversity and multiplexing technique does not have a visible deteriorating effect on the handover performance.

Exploitation of Mobile Edge Computing in 5G Distributed Mission-Critical Push-to-Talk Service Deployment

There is a growing interest in adapting mission critical public-safety communications from traditional private radio technologies toward 5G. The need for resiliency and strong delay requirements has resulted in mobile edge computing (MEC) emerging as a key technology to improve the deployment of public safety applications over the mobile network. This paper presents a non-standalone 5G ETSI MEC-based architecture for mission-critical push-to-talk (MCPTT) services. The proposal suggests a hierarchical distributed MCPTT architecture that allocates the user plane at the edge, keeping the control plane (CP) centralized for synchronization and assistance purposes. The MEC architecture enables the deployment of low latency services, due to the proximity of functional servers to the end-user, releases user equipment from heavy workloads, and benefits from horizontal scalability to provide dynamic allocation of network resources at specific locations. The proposed architecture is also beneficial in an isolated E-UTRAN operation situation, where in the case of backhaul connection loss, local MCPTT services can be straightforwardly deployed within an isolated group of eNodeBs.