5G Channel Models: Requirements and Deployment Scenarios

5G, Tech Fundas

Propagation Channel Model:

A channel model is also known as radio wave propagation model, it characterizes radio wave propagation as a function of frequency, distance, environment, and other factors. In other words, we can say that channel model provides us rough idea how much distance a signal can travel in a certain environment (morphology like urban, suburban or rural etc.) with the known transmitter and receiver height.

A channel model is usually developed to predict the behavior of propagation of radio signal, for all similar channel under and similar constraints (environment, channel fading, multi-path etc). Channel models typical predict the path loss along a wireless link or effective coverage area of a transmitter.

Channel Models for 5G:

At 3GPP TSG RAN #69 meeting the Study Item Description on “Study on channel model for frequency spectrum above 6 GHz” was approved. This study item covers the identification of the status/expectation of existing information on high frequencies e.g. spectrum allocation, scenarios of interest, measurements, etc, and the channel model(s) for frequencies above 6 GHz up to 100 GHz.

Next generation 5G cellular systems will operate in frequencies ranging from around 500 MHz up to 100 GHz. Till now with LTE and Wi-Fi technologies, we were operating below 6GHz and the channel models were designed and evaluated for operation at frequencies only as high as 6 GHz. The new 5G systems is to operate in bands above 6 GHz and existing channel models will not be valid, hence there is a need for accurate radio propagation models for these higher frequencies, hence it requires new channel models

The objective for New 5G Channel Models:

The requirements of the new channel model that can support 5G operation across frequency bands up to 100 GHz is based on the existing 3GPP channel models along with extensions to cover additional 5G modeling requirement and some of these requirements are listed below:

  • New channel model should support large antenna arrays, especially at higher-frequencies in millimeter-wave bands, it will very likely to be 2D and dual-polarized both at the access point (AP) and the user equipment (UE)
  • New channel model must accommodate a wide frequency range up to 100 GHz.
  • It needs to include joint propagation characteristics over different frequency bands to evaluate multiband operation, e.g., low-band and high-band carrier aggregation configurations.
  • New channel model must support large channel bandwidths (up to 2 GHz), where the individual channel bandwidths may be in the range of 100 MHz to 2 GHz and may support a carrier aggregation
  • The new channel model must accommodate mobility, in particular, the channel model structure should be suitable for mobility up to 500 km/hr,
  • The mobility channel model should be extendable to support scenarios such as device to device (D2D) or vehicle to vehicle (V2V).
  • New channel model must ensure spatial/temporal/frequency consistency,
  • Model should also ensure that the channel states, such as line-of-sight (LOS)/non-LOS (NLOS) for outdoor/indoor locations

5G Deployment Scenarios:

As per 3GPP TR 38.900 following are the key deployment scenarios of interest identified:

  • Urban Micro (UMi) with Outdoor to Outdoor (O2O) and Outdoor to Indoor (O2I): In deployment scenario the Base Stations (BS) are mounted below rooftop levels of surrounding buildings. UMi open area model is intended to capture real-life scenarios such as a city or station square. The width of the typical open area is in the order of 50 to 100 m. Example: [Tx height:10m, Rx height: 1.5-2.5 m, ISD: 200m]
  • Urban Macro (Uma) with Outdoor to Outdoor (O2O) and Outdoor to Indoor (O2I): In deployment scenarios where Base Stations are mounted above rooftop levels of surrounding buildings. Example: [Tx height:25m, Rx height: 1.5-2.5 m, ISD: 500m]
  • Indoor: These deployment scenarios are intended to capture various typical indoor deployment scenarios, including office environments, and shopping malls. The typical office environment is comprised of open cubicle areas, walled offices, open areas, corridors etc. Here Base Stations are mounted at a height of 2-3 m either on the ceilings or walls. The shopping malls are often 1-5 stories high and may include an open area (or “atrium”) shared by several floors. The BSs are mounted at a height of approximately 3 m on the walls or ceilings of the corridors and shops. Example: [Tx height: 2-3m, Rx height: 1.5m, area:  500 square meters]
  • Backhaul, including outdoor above rooftop backhaul in urban area and street canyon scenario where small cell BSs are placed at lamp posts.
  • D2D/V2V. Device-to-device access in the open area, street canyon, and indoor scenarios. V2V is a special case where the devices are mobile.

Groups and Ongoing activities for 5G Channel Models:

Groups and projects with channel models:

  • METIS (Mobile and wireless communications Enablers for the Twenty-twenty Information Society)
  • MiWEBA (MIllimetre-Wave Evolution for Backhaul and Access)
  • ITU-R M
  • COST2100
  • IEEE 802.11
  • NYU WIRELESS: interdisciplinary academic research center
  • Fraunhofer HHI has developed the QuaDRiGa channel model

Groups and projects which intend to develop channel models:

  • 5G mmWave Channel Model Alliance: NIST initiated, North America based
  • mmMAGIC (Millimetre-Wave Based Mobile Radio Access Network for Fifth Generation Integrated Communications): Europe based
  • IMT-2020 5G promotion association: China-based

METIS Channel Models:

  • Identified 5G requirements (e.g., wide frequency range, high bandwidth, massive MIMO, 3-D and accurate polarization modeling)
  • Performed channel measurements at various bands between 2GHz and 60 GHz
  • Provided different channel model methodologies (map-based model, stochastic model or hybrid model). For stochastic model, the proposed channel is focused on the outdoor square, Indoor cafeteria, and indoor shopping mall scenarios.

MiWEBA Channel Models:

  • Addressed various challenges: Shadowing, spatial consistency, environment dynamics, spherical wave modeling, dual mobility Doppler model, ratio between diffuse and specular reflections, polarization
  • Proposed Quasi-deterministic channel model
  • Performed channel measurements at 60 GHz
  • Focused on the university campus, street canyon, hotel lobby, backhaul, and D2D scenarios.

ITU-R M Channel Models:

  • Addressed the propagation loss and atmospheric loss on mmW
  • Introduced enabling antenna array technology and semiconductor technology
  • Proposed deployment scenarios, focused on a dense urban environment for high data rate service: indoor shopping mall, indoor enterprise, in home, an urban hotspot in a square/street, mobility in the city.

COST2100 and COST IC1004 Channel Models:

  • Geometry-based stochastic channel model that reproduce the stochastic properties of MIMO channels over time, frequency and space. It is a cluster-level model where the statistics of the large-scale parameters are always guaranteed in each series of channel instances.

NYU WIRELESS Channel Models:

  • Conducted many urban propagation measurements on 28/38/60/73 GHz bands for both outdoor and indoor channels, measurements are continuing.
  • Proposed 3 areas for 5G mmWave channel modeling which are small modifications or extensions from 3GPP’s current below 6GHz channel models
  • (1) LOS/NLOS/blockage modeling (a squared exponential term); (2). Wideband power delay profiles (time clusters and spatial lobes for a simple extension to the existing 3GPP SSCM model); (3). Physics-based path loss model (using the existing 3GPP path loss equations, but simply replacing the “floating” optimization parameter with a deterministic 1 m “close-in” free space reference term in order to provide a standard and stable definition of “path loss exponent” across all different parties, scenarios, and frequencies).

802.11 ad/ay Channel Models:

  • Conducted ray-tracing methodology on 60 GHz band indoor channels, including conference room, cubicle, living room scenarios
  • Intra cluster parameters were proposed in terms of ray excess delay and ray power distribution
  • Human blockage models were proposed in terms of blockage probability and blockage attenuation

5G mmWave Channel Model Alliance:

  • Will provide a venue to promote fundamental research into the measurement, analysis, identification of physical parameters, and statistical representations of mmWave propagation channels.
  • Divided into six collaborative working groups that include a Steering Committee; Modeling Methodology Group; Measurement Methodology Group; and groups that focus on defining and parameterizing Indoor, Outdoor, and Emerging Usage Scenarios.
  • Sponsored by Communications Technology Research Laboratory within the NIST.

mmMAGIC:

  • Brings together major infrastructure vendors, major European operators, leading research institutes and universities, measurement equipment vendors and one SME.
  • Will undertake extensive radio channel measurements in the 6-100 GHz range.
  • Will develop and validate advanced channel models that will be used for rigorous validation and feasibility analysis of the proposed concepts and system, as well as for usage in regulatory and standards fora.

IMT-2020 5G promotion association

  • Jointly established by three ministries of China based on the original IMT-Advanced promotion group
  • Members including the main operators, vendors, universities and research institutes in China
  • The major platform to promote 5G technology research in China and to facilitate international communication and cooperation

QuaDRiGa (Fraunhofer HHI)

  • QuaDRiGa (QUAsi Deterministic RadIo channel GenerAtor) was developed at the Fraunhofer Heinrich Hertz Institute within the Wireless Communications and Networks Department to enable the modeling of MIMO radio channels for specific network configurations, such as indoor, satellite or heterogeneous configurations.
  • Besides being a fully-fledged 3D geometry-based stochastic channel model (well aligned with TR36.873), QuaDRiGa contains a collection of features created in SCM(e) and WINNER channel models along with novel modeling approaches which provide features to enable quasi-deterministic multi-link tracking of users (receiver) movements in changing environments. QuaDRiGa supports Massive MIMO modeling enabled through a new multi-bounce scattering approach and spherical wave propagation. It will be continuously extended with features required by 5G and frequencies beyond 6 GHz. The QuaDRiGa model is supported by data from extensive channel measurement campaigns at 10 / 28 / 43 / 60 / 82 GHz performed by the same group.

Reference: 3GPP TR 38.900 V14.3.1 (2017-07) Study on channel model for frequency spectrum above 6 GHz (Release 14)