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Advanced Wide-Band Transceiver Architectures for Beyond 5G Wireless Systems

Periodic Reporting for period 2 - ADVANTAG5 (Advanced Wide-Band Transceiver Architectures for Beyond 5G Wireless Systems)

Reporting period: 2019-06-01 to 2020-05-31

"Emerging fifth generation (5G) mobile communications systems aim to multiply the wireless data transfer capacity by factor of 1000. The radio hardware of the current fourth generation (4G) wireless communications standard is incapable of handling the data rates and thus new radio hardware structures must be developed.

One of the main differences between 4G and 5G is the use of directed communication e.g. ""beam steering"", where the base stations ""direct"" their radio signals towards the user equipment. As the beams aredirected to the particular user, this effectively prevents on user to disturb the communication of the other user, thus reducing inter-user interference, which would otherwise become the limiting factor of communication capacity in very crowded 5G and beyond systems. Beam-forming directs the transmission to desired direction only, thus providing isolation between users in space. Separating user signals in space gives additional degree of freedom for resource allocation, called ""spatial multiplexing"". The core challenge of 5G and beyond radio systems is to implement spatial multiplexing capability in transceiver hardware and crucial for the communication capacity leap as it is the most promising method to increase available spectral communication resources visible for a single user.

Implementing directivity requires use of multiple antennas. e.g. Multi-User-MIMO (Mimo=Multiple In Multiple Out) antenna arrays. More antennas means more and better directivity. However, it is impossible to just increace the number of antennas and multiply the hardware as it would result in enormous pover consumption and multiply the communication capacity requirement between the system central processor and antenna tranceiver units. Finding innovative solutions to this problem is the core task of this project: We aim to develop transceiver units for 5G and beyond beam-steering transceiver arrays and optimize the cost, power consumption and performance of the hardware.

We aim to develop optimized partitioning between the signal processing blocks of beyond 5G antenna array, develop advanced integrated transceiver hardware structures, providing capabilities for agile carrier aggregation and beam-steering, and provide means for digitally assisted interference management. The aim is to find system-level tradeoffs for beam-steering radio structures, optimizing the power consumption, performance and overall cost of the system by utilizing the diversity provided by antenna arrays. Through diversity it is possible to maintain the system performance while individual transceiver units have less stringent performance requirements.

We aim to take full advantage over the semiconductor process scaling (e.g faster circuits with smaller power consumption) and provide new time-based radio architecture implementations that fully support 5G and beyond radio system, delay tuning and synchronization of distributed processing element of an transceiver array. 5G already aims to do a 10-fold leap on every aspect of a communication device, and generations to come will unavoidably obscure the boundaries between communications and computing. However, this cannot happen with the current radio architectures where technologies for communication and computing are very different.

As planned, we ahve developed develop advanced methods for linearization, interference detection and cancellation by merging adaptive DSP with transmitter and receiver design with active interferer and blocker detection and cancellation capabilities. In the future radio standards, it is mandatory to cope with the interference problem in a holistic manner in spatial, temporal and frequency dimensions to prevent the blocking of communication with interference generated by other users. Interferer management part of this project have merged the functions of transceiver array beam-steering, spectrum sensing /blocker detection and removal, and protection of the receiver signal band in frequencey domain."
During this project we have developed an integrated Multiuser-MIMO transceiver module for beam steering antenna array. This work aims to improve implementation methodology of large system of chip modules. During the project we have created a system modeling verification environment that seamlessly merges modeling, verification and hardware generetors so that programmatic design methods can be eventually deployed to optimize the system hardware. We have used Multiuser-MIMO module as an example design case for the methodology, and designed two prototype IC's. Furthermore, we have developed a programmatic SoC implementation flow that seamlessly merges the building blocks developed by several designer to a single IC SoC and performs the implementation flow in automated fashion, enabling the use of agile cycle-based design methodology. During the incoming phase of the project, the methodology has been adopted in three IC designs in Aalto University. The simulation and verification environment environment TheSyDeKick, initiated during the outgoing periad has been further developed to support two analog simulators, and RTL simulator part has been improved to automate the testbench generation. Support for VHDL hardware description language has also been added.

We have developed and measure a new outphasing transmitter sturucture called Tri-phasing. Tri-phasing is extremely digital radio architecture that fully utilizes time-based information handling and thus benefits from continuously improving speed and timing accuracy of modern semiconductor processes. Tri phasing architecture has been published in Journal of Solid-State circuits in 2019. In addition to transmitters, we have also developed interfererence tolerant RF-receiver front-end structures, RF-sampling True-time delay RF-front ends for beam steering receivers and FFT-based blocker detection and directivity control for RF receivers have been measured. Work related to interference tolerant RF-receiver has recently been published in conferences and journals.
The system verification and implementation methodology have been successfully applied to design and verification of two large SoC's. We will continue the development of the digital signal processing of the Multiuser-MIMO system and implemention methodology, and further improve and extend it's functionality for verification of analog circuits and measurement control. Furthermore, we have initiated teaching of the methodology by including the methodoly to the courses teached in Aalto University.

The Tri-hasing transmitter developed was not only first tri-phasing transmitter, but this circuit also featured the highest level of integration among published transmitters based on multilevel outphasing. The advantages of our design in terms of enhanced linearity and reconfigurability are demonstrated with extensive measurements, including scenarios of non-contiguous carrier aggregation, digital carrier generation, and the transmission of OFDM signals with up to 100-MHz RFbandwidth. Furthermore, most of the transmitter front-end is designed with digital CAD tools, enabling benefits from process scaling and reduced design time.

Furthermore, based on the measurement results of the first prototypes, We will continue development of RF-sampling true-time-delay front-end structures. Second prototype of this receiver is currently under design.
Block diagram of a Multi-user-MIMO radio array.