Icaro L. J. da Silva

5G Radio Access Network Architecture: Design Guidelines and Key Considerations

While there is clarity on the wide range of applications that are to be supported by 5G cellular communications, and standardization of 5G has now started in 3GPP, there is no conclusion yet on the detailed design of the overall 5G RAN. This article provides a comprehensive overview of the 5G RAN design guidelines, key design considerations, and functional innovations as identified and developed by key players in the field.1 It depicts the air interface landscape that is envisioned for 5G, and elaborates on how this will likely be harmonized and integrated into an overall 5G RAN, in the form of concrete control and user plane design considerations and architectural enablers for network slicing, supporting independent business-driven logical networks on a common infrastructure. The article also explains key functional design considerations for the 5G RAN, highlighting the difference to legacy systems such as LTE-A and the implications of the overall RAN design.

Impact of network slicing on 5G Radio Access Networks

Network slicing addresses the deployment of multiple logical networks as independent business operations on a common physical infrastructure. The concept has initially been proposed for the 5th Generation (5G) core network (CN) however, it has not been investigated yet what network slicing would represent to the design of the 5G radio access network (RAN). The paper explains how network slicing may impact several aspects of the 5G RAN design such as the protocol architecture, the design of network functions (NFs) and the management framework that needs to support both the management of the infrastructure to be shared among the slices and the slice operation.

A novel state model for 5G Radio Access Networks

With the trends towards Internet of Things (IoT) and massive Machine-Type Communications (mMTC) it is expected that the 5th Generation of mobile communications (5G) will have a significant amount of battery powered devices (e.g. sensors, baggage tags, etc.). Therefore, battery efficiency and duration will be essential, especially for those devices in remote locations and/or restricted areas. It would be difficult to predict all the 5G use cases, for example, that may arise from IoT however it is expected that for some of these the tradeoff between efficient power savings modes and low-latency system access might be essential. In order to solve this tradeoff, called herein User Equipment (UE) sleeping problem, the paper proposes a novel state model for 5G Radio Access Networks (RAN) that relies on a novel state called “connected inactive” where both the UE and the network does not throw away context information. The state is envisioned to be highly configurable in order to address unpredictable use cases possibly with different requirements. It is shown via protocol signaling diagrams that that the proposed solution enables a quick and lightweight transition from inactive to active data transmission.

Agile resource management for 5G: A METIS-II perspective

An explosive growth in the demand for higher data rates and capacity along with diverse requirements set by massive and ultra-reliable machine-type communications are the main drivers behind the development on new access technologies as part of the fifth generation (5G) networks. Currently, different air interface (AIF) and/or AIF variants, optimized based on the frequency band of operation and use case, are envisioned for such a network. Developing an agile resource management framework for 5G networks is one of the main goals of the METIS-II project. The METIS-II project builds strongly upon the EU flagship project METIS, which has laid the foundation of 5G. This framework will take into account the multi-link and multi-layer constraints currently envisioned for 5G. In this paper, we provide our first insights into agile resource management and the associated synchronous control functions. We will discuss the essential building blocks in terms of technology enablers and their mapping to 5G services and deployments. The introduced agile resource management framework for 5G is expected to enable enhanced interference management, dynamic traffic steering, fast radio access network (RAN) moderation, efficient context management, and optimized integration with legacy networks.

5G radio access above 6źGHz

Designing and developing a millimetre-wave mmWave-based mobile radio access technology RAT in the 6-100i¾źGHz frequency range is a fundamental component in the standardisation of the new 5G radio interface, recently kicked off by 3rd Generation Partnership Project. Such component herein called the new mmWave RAT will not only enable extreme mobile broadband services but also support ultra-high definition/three-dimensional streaming, offer immersive applications and ultra-responsive cloud services to provide an outstanding quality of experience to the mobile users. The main objective of this paper is to develop the network architectural elements and functions that will enable tight integration of mmWave technology into the overall 5G radio access network. A broad range of topics addressing mobile architecture and network functionalities will be covered-starting with the architectural facets of network slicing, multi-connectivity and cells clustering, to more functional elements of initial access, mobility, radio resource management and self-backhauling. The intention of the concepts presented here is to lay foundation for future studies towards the first commercial implementation of the mmWave RAT above 6i¾źGHz. Copyright

Multiuser receiver for PUCCH signaling with transmit diversity

This paper deals with a transmit diversity scheme to be applied in multiple-antenna signaling over the physical uplink control channel (PUCCH) of 3GPP LTE-Advanced (Release 10). Taking into account the signaling structure of this system, we show that received signal at the base station can be modeled using a tensor decomposition with constraints imposed on the control symbol matrix. By exploiting the proposed tensor model and its known structure, a receiver for joint multiuser channel estimation and detection is presented. The receiver is based on a semi-blind algorithm, by using known reference control symbols at the first iteration, and then proceeding with a data-aided channel and symbol estimation in subsequent iterations. Numerical results from Monte Carlo simulations are provided for performance assessment.

Event-based performance monitoring for inter-system cell reselection: A SON enabler

It has been observed that in overlaid 3G/2G networks certain user equipments (UE) may stay camped on 2G for long periods despite the fact there is available 3G coverage. In this paper we present a framework to enable network operators to identify these occurences, not easily recognized using counter-based observability. The proposed methodology relies on the post processing of performance monitoring (PM) events from the radio access and core networks, feature provided by most major network vendors. Based on that, new key performance indicators (KPI) are defined e.g. the time UEs camp on 2G. Then, we show how these event-based KPIs may be used as inputs to self-optimization algorithms, functioning as a self-organizing networks (SON) enabler. Results are shown using data from live 3G/2G networks.

5G Multi-RAT Integration Evaluations Using a Common PDCP Layer

5G is expected to operate in a wide frequency range to support new challenging use-cases. Multi- RATs (Radio Access Technologies): NR (New Radio) and evolved LTE (Long Term Evolution) will together constitute 5G. Utilizing NR at high frequencies will have a significant impact on radio propagation conditions with e.g. unfavorable higher path loss and increased outdoor-to-indoor penetration losses. In order to provide a reliable communication from the outset of 5G deployment and to minimize the standardization and implementation complexity, 5G UP (User Plane) instances of 5G AIs (Air Interface) related to evolved LTE and NR need to be aggregated on a certain layer of the protocol stack. This paper sheds light on how to integrate 5G AIs into a single 5G AI framework and explores which protocol stack layer could be used as aggregation layer. Inter-RAT hard handover is the state of the art technique to integrate multiple RATs in order to support mobility and reliability across different RATs. However, the hard handover incurs a transmission interruption which stands as an obstacle along the way of accomplishing 5G design. According to simulation results, a common PDCP (Packet Data Convergence Protocol) layer improves the hard handover functionality and stands out as a basis for tight interworking between evolved LTE and NR. By means of simulation, it is shown that the multi-RAT UP aggregation can achieve three times higher user throughput, when NR is using 28 GHz and LTE 2 GHz, compared to stand-alone NR.

Emerging network architecture and functional design considerations for 5G radio access

While there is already a common understanding of the services, which 5th generation 5G mobile communications systems should support, and the key technology components needed to achieve this, there is still the need for further clarification and consensus among key players on the overall 5G radio access network RAN architecture and its detailed functional design. The 5G public private partnership 5G PPP project METIS-II has the objective to foster exactly this consensus building before and in the early days of the standardisation work for 5G. This paper lists the 5G RAN design requirements as identified in the project and summarises the latest considerations of METIS-II on the air interface landscape in 5G, the envisioned logical RAN architecture and related aspects, as well as key functional design considerations in 5G, which have found wide endorsement within the project. Copyright

A Multi-user Receiver for Inter-Cell Interference Reduction in LTE PUCCH Signaling

In 3rd generation partnership project (3GPP) long term evolution (LTE) systems, when no resources has been assigned in the uplink to a given user equipment (UE), the control information associated with layers 1 and 2 in the protocol stack is conveyed back to the base station through the so-called physical uplink control channel (PUCCH). In PUCCH, the data streams transmitted by multiple UEs are multiplexed in the time-domain and in the frequency-domain with the aid of spreading codes. Although the spreading codes associated with UEs within the same cell can be assumed to be orthogonal, the presence of inter-cell interference (ICI) in multi-cell scenarios severely limits receiver performance. In particular, the Format 1 of PUCCH, which is associated with the transmission of hybrid automatic repeat request acknowledgements (ACK/NACK) and scheduling requests, has a major impact on system performance, since an incorrectly decoded ACK/NACK message may introduce significant delay in data transmission. In this contribution, we propose a new multi-user receiver for ICI reduction in PUCCH LTE that operates both in cooperative and non-cooperative multi-cell architectures. The proposed receiver relies on a constrained tensor modeling of the received signal in PUCCH signaling, and affords an iterative joint channel estimation and symbol detection by simultaneously exploiting the energy of the data symbols and the pilot tones present in PUCCH. The formulation of the proposed algebraic receiver model incorporates symbol-basis hopping and slot-basis hopping signaling schemes, which are interference randomization techniques existing in the 3GPP specifications of LTE system. Computer simulation results show the remarkable performance gains of the proposed receiver compared to the conventional time-frequency decorrelator based receiver.