M5HESTIA: mmW Multi-user Massive MIMO Hybrid Equipments for Sounding, Transmissions and HW ImplementAtion

 

UMR CNRS 6164 - IETR - Institut d’Electronique et de Télécommunications de Rennes

UMR CNRS 6285 - Lab-STICC - Laboratoire des Sciences et Techniques de l'Information, de la Communication et de la Connaissance

 

Abstract: Exploiting millimetre-wave (mmW) radio spectrum will unlock ultra-large bandwidths for future 5th generation (5G) – and beyond – wireless systems. Developments of innovative cost-effective antenna / beamforming architectures and new processing techniques play a key role in those frequency bands, in order to allow massive deployment of consumer products in the coming years.

To meet growing demand for higher throughputs, advanced digital communication techniques based on multicarrier modulations, multiple antenna systems (MIMO) and their extension to massive MIMO (M-MIMO), powerful coding schemes or interference coordination are under study and could be combined with solutions based on network densification and deployment of heterogeneous infrastructures. An alternative but complementary way to increase throughputs is to deploy cellular systems operating in mmW bands (typically in V-band from 57 to 66 GHz, and in E-bands from 71-76 GHz and 81-86 GHz). These high frequency bands offer very large bandwidths (some of them are unlicensed) that are one of the simplest ways to increase system capacity, and also lead to enhanced miniaturisation of radio-frequency architectures. In such a context, M-MIMO systems, with up to hundreds of radiating elements at the access point (AP), are extremely attractive solutions to achieve very high data rates (multi-gigabit / sec) for multiple users sharing the same spectrum at the same time, with low power consumption thanks to the use of specific analogue/digital precoding techniques. Moreover, any effective hardware implementation of such systems must rely on a realistic knowledge of channel impairments and mmW propagation / antenna characteristics, especially for outdoor and mobile communications for which the results available in the most recent literature are very limited.

M5HESTIA project aims at designing advanced M-MIMO antennas, characterizing / modelling the outdoor mmW channel and proposing innovative algorithms in order to demonstrate, a full M-MIMO hardware (HW) platform operating in the 60-GHz band.

To reach the very ambitious goals of the M5HESTIA project, a closed collaboration has been set up with a complementary project funded by IRT b<>com (internal project at IRT) and also dedicated to mmW transmissions; this project is entitled 5M (Mm-Waves Multi-User Massive MIMO).

Therefore, the two projects M5HESTIA and 5M will run in parallel to reach common and shared objectives:
i) comparison between different MIMO processing techniques, by using the propagation channel model provided by the M5HESTIA project and ii) integration in the HW platform developed by IRT of the M-MIMO antenna array developed in the framework of M5HESTIA.

 

 Scientific challenge

Massive MIMO is one of the main enablers that will allow a drastic increase of data throughput and capacity of the 5G radio network. This increased demand of capacity will mainly occur in dense environments such as city centres, streets, stadium that will be considered as typical use cases targeted by the M5HESTIA project. In these environments, massive MIMO technology will be needed to support such increase for outdoor small cells deployment. Such a use case is considered by the M5HESTIA project via the implementation of a massive MIMO demonstrator that could be related to an outdoor small cell.

 

Figure 1: Target HW demonstration of M5HESTIA and project topics.

 

 

Figure 1 illustrates the main project scenario for HW demonstrations. It consists in implementing a 60-GHz HW platform able to focus/collimate the right signal in the desired (user) direction while reducing interference between different users. The selected demonstration use case is the following: the transmitter (Tx) - a typical small cell composed of a maximum of 64 radiating elements and operating in the 60-GHz band in outdoor environment - will encode and process two different video streams towards two different user equipments (UE1 & UE2 using a maximum of 2 receive antennas).

The main goal of M5HESTIA crystalizes in four scientific and technological objectives, all dedicated to M-MIMO in the 60-GHz band.

Objective 1: Real-time HW implementation for Multi-User MIMO (MU-MIMO)

The objective is to implement an HW platform demonstrating that users, geographically attached to a given small cell, can be spatially discriminated thanks to the combination of “appropriate antenna design and digital processing techniques”. Indeed, we want to demonstrate that it is possible to simultaneously transmit towards isolated users, different signals by focusing millimetre-wave power in a given direction, optimising the radiated power while minimizing the interference between users. This corresponds to the so-called Multi-User MIMO (MU-MIMO) concept. Therefore the HW platform will implement eNodeB and user equipment. At Tx side, the demonstrator will integrate an adaptive antenna array (the total number of elements and the beamforming techniques will be defined during the project) implemented on RF and a digital board, the latter one integrating the digital/baseband processing. The digital board will be dynamically programmed to take into account real-time constraints, to target at the same time different users with different contents. Different SDMA schemes allowing for MU M-MIMO will be chosen for HW implementation among the studied algorithms (optimisation of the feedback compression, solution based on channel reciprocity, etc.) depending on the theoretical results obtained with realistic channel models and complexity issues.

Objective 2: design and demonstration of 60-GHz front-end radios for channel sounding and M-MIMO communications

Various advanced 60-GHz RF front-ends will be designed and prototyped for M-MIMO channel sounding and M-MIMO communications integrating analogue and digital beamforming. The front-end specifications and architectures are different for these two cases. However, the ultimate objective is to design a 60-GHz front-end with up to 64 IQ links. To mitigate the risks associated to this extremely challenging objective, various intermediate antenna systems, still at the state-of-the-art, will be implemented.

Objective 3: SIMO channel sounding, characterisation and modelling

An accurate and reliable knowledge of the transmission channel model is strategic for an optimised design of communication systems. The outdoor radio channel has been recently characterized and modelled for SISO channel in the FP7 project MiWeba. M5HESTIA proposes to model the M-MIMO channel at mmW, based in a first step, on literature and theoretical investigations, and, in a second step, on its own mmW SIMO channel measurements campaign. To the best of our knowledge, this work is pioneer at the international level. The results obtained will be used opportunely for a realistic description of the M-MIMO transmission channel (including the important effect of antenna arrays and RF/baseband architecture) for further studies on beamforming and precoding schemes.

Objective 4: Signal processing algorithm optimisation for mmW M-MIMO transmissions

Signal processing algorithms accounting for the mmW M-MIMO channel characteristics (including antenna and RF front-end) are of high importance to propose efficient communication strategies, especially to exploit the system spatial dimension for SDMA purpose. We will propose, develop and compare algorithms for M-MIMO transmissions optimised for mmW outdoor propagation in a multi-user context. The most promising solutions will be selected for implementation in the HW platform.

Consortium

The consortium of M5HESTIA project gathers two academic partners members of CominLabs (IETR and Lab-STICC) and two industrial partners (Orange and IRT b<>com).

Figure 2: Skills and expertise of the M5HESTIA consortium

The consortium involves the following people and teams:

- INSA of Rennes, IETR : Maryline Hélard, Matthieu Crussière

- Télécom-Bretagne, Lab-STICC: François Gallée, Patrice Pajusco, Camilla Karnfelt, Daniel Bourreau

- University of Rennes, IETR : Ronan Sauleau, Bernard Uguen

- B-Com: Rodolphe Legouable, Jean Dion, Stéphane Paquelet

- Orange Labs: Nadine Malhouroux, Christian Gallard, Philippe Ratajczak, Jean-Pierre Rossi