The IEEE 1st Int. Workshop on D2D and Public Safety Communications (WDPC) took place on April 6, 2014 in Istanbul, in conduction with the IEEE WCNC conference. Petar was one of the keynote speakers, presenting the talk “What is in for D2D in 5G wireless and how to support underlay low-rate M2M links”. The slideshow of the talk can be downloaded here. The full program can be seen at:
The METIS project has released a document describing initial system concepts for the 5G wireless system. Our research group is actively involved in multiple aspects of METIS and in this document I have participated in the capacity as a driver of the topic Ultra-Reliable Communication (URC). In addition to the common approach to work on detailed wireless technologies, METIS has also defined multiple overarching topics, termed Horizontal Topics, URC being one of them. A horizontal topic covers the system-level aspect of a certain new feature that is envisioned for 5G wireless systems and this document is an initial report on the system concept per horizontal topic. The document is available here and the executive summary is given below.
The overall purpose of METIS is to develop a system concept that meets the requirements of the beyond-2020 connected information society and extend today’s wireless communication systems to support new usage scenarios. This is an immense task, residing at a level that is different from the level at which detailed technical innovations are created. Therefore, the task of overall METIS system concept has been segmented into system concepts related to five Horizontal Topics (HTs): (1) D2D – Direct Device-to-Device Communication, (2) MMC – Massive Machine Communication, (3) MN – Moving Networks, (4) UDN – Ultra-Dense Networks, and (5) URC – Ultra-Reliable Communication.
This document provides a first view on the system concepts associated with each HT and indicates the steps and directions towards integrating them into an overall METIS system concept in the remaining time frame of the project. Each HT creates a context for applying and optimizing the Technology Components (TeC) in the Work Packages (WPs). For example, Massive MIMO is a generic technology that can give rise to innovations applicable in UDN and supporting the performance requirements specified by URC. The five HTs are not independent and their interaction is the basis for creating the architecture that is capable to achieve the main objectives for METIS [MET13-D11]:
- 1000 times higher mobile data volume per area,
- 10 to 100 times higher typical user data rate,
- 10 to 100 times higher number of connected devices,
- 10 times longer battery life for low power devices,
- 5 times reduced E2E latency.
These objectives have to be met at a similar cost and energy consumption as today’s networks. The research challenge is amplified by considering that the wireless scenarios in 2020 will feature communication modes and services that are not merely “more and faster of what we have today”. As an example, the vehicles of the future that are interconnected with very high reliability and low latency, improving the efficiency and safety on the road. The METIS system will respond to the requirements for improved: 1) efficiency in terms of energy, cost and resource utilisation than today’s system 2) versatility to support a significant diversity of requirements, e.g. connections in Gbps from few devices vs. connections in kbps from many machine-type devices, inclusion of moving networks vs. statically deployed sensors, etc. 3) scalability in terms of number of connected devices, densely deployed access points, spectrum, energy and cost.
The concepts presented in this document are clearly demonstrating the capability of the HTs to channelize the technical innovations towards creating the overall METIS system. The highlights for the system concepts of the individual HTs are given as follows:
- The HT D2D concept addresses the utility of the local exchange of information among the devices and creates a framework for solving the associated technological challenges. Putting D2D connectivity as a basic architectural element in the 5G system, rather than having it as an add on to an already existing architecture, leads to multiple benefits: increased coverage (availability and reliability), offload backhaul (cost efficiency), provide a fall-back solution (reliability), improve spectrum usage (spectrum efficiency), typical user data rate and capacity per area (capacity density), and enable highly reliable, low-latency Vehicle-to-Infrastructure (V2X) connections. Efficient D2D operation critically depends on interference management, resource allocation, efficient relaying for coverage extension, etc.
- The HT MMC concept contains the technologies for radio access that will be capable to support an unprecedented number of devices. They are segmented into three types of radio access: (1) direct access, which devices transmit directly to the access node; (2) access through accumulation/aggregation point; and (3) machine-type communication between devices. The TeCs used to support these types of access fall in several categories: overlay of multiple transmissions (by means of quasi-orthogonal random access, sparse coding, successive interference cancellation, and reuse of resource by short-range links), smart pre-allocation of resources (persistent scheduling), techniques to lower the sync requirements and context/service-aware configuration of the radio access.
- The HT MN concept introduces innovative directions for the future relationship between vehicles and wireless communications. Three clusters are defined: (1) MN for mobility-robust high-data rate communication links (MN-M), to enable broadband as well as real-time services in mobile terminals and moving relays; (2) MN for nomadic network nodes (MN-N), to enable a flexible and demand-driven network deployment; (3) MN for V2X communications (MN-V), to enable reliable and low-latency services such as road safety and traffic efficiency. While the MN-M cluster represents an evolutionary improvement of the existent technology addressing highly mobile scenarios, the MN-N and MN-V clusters introduce a paradigm shift in the usage of mobile communications.
- The HT UDN has defined a core specific concept optimized for the potential stand- alone operation of a layer of ultra-densely deployed small cells. Beside considerations on a new spectrum flexible air interface, it foresees a potentially tight collaboration of nodes w.r.t. resource allocation coordination, a fast (de-)activation of cells and inbuilt self-backhauling support. An extended UDN concept offers additional performance improvement by: 1) Context awareness for mobility, resource and network management, 2) inter-RAT/ inter-operator collaboration, 3) tight interaction of a UDN layer with a macro layer holding superior role in control and management functions over common area, and 4) macro-layer based wireless backhaul for flexible and low- cost UDN deployments.
- The HT URC system concept targets operation modes that are not present in today’s systems. URC-L (Long-term URC) targets the following operation mode: when not possible to operate at the peak rate, provide reliable moderate rates to all users instead of failing some of them. URC-L will be instrumental for the cloud-based services of the future. URC-S (Short-term URC) aims to guarantee latency despite the competition from multiple users and varying channels and will be critical for e.g. V2X connectivity. URC-E (URC for Emergency) aims to provide minimal guaranteed connectivity upon infrastructure damage. A generic URC toolbox consists of: spectrum allocation and management, robust PHY mechanisms, signalling structure and interface management, Multi-RAT and reliable service composition.
Based on the current view on the system concept, METIS has selected two technology components for implementation test-beds. The technology components are “Direct network controlled device to device communication with interference cancellation” to be implemented on the Radio Resource Management test-bed, and “FBMC/OQAM new waveform” for the Digital Base-Band test-bed.
The HT-specific concepts will be integrated towards the overall METIS system, which will contain new air interfaces as well as the evolved versions of today’s systems. In order to deal with such a level of complexity and support the required reliability/scalability, the METIS system will feature Software-Defined Networking (SDN), Network Function Virtualization (NFV), and Self-Organizing Network (SON) technologies.
The next steps of the work on the METIS system concept in the project include: further integration of the specific HT concepts with the METIS architecture, further positioning of METIS technical goals by the evaluation criteria defined for 5G systems and establishment of a technology roadmap for the deployment of the METIS 5G system.