What about the future? What are the new applications? And can we really use this to communicate with exoplanets?
How can operators benefit from digital beamforming? What is the capacity gain and why does it work so much better?
Drilling into the hart of the matter for BeammWave! Digital beamforming – to-be-or-not-to-be?
The mmWave frequency range is highly suitable for sensing and radar purposes due to the short radio wavelength enabling localization and positioning in the mm to cm range. Joint sensing and communication is being discussed, where a communication system not only communicates but also senses the environment and basically uses mmWave radar for the detection and positioning of objects.
Traditionally when designing analog or hybrid beamforming solutions for mmWave the design has been targeting a single application. A certain antenna panel/array has been designed for a certain purpose, such as a handheld device, and if another mmWave transceiver architecture is needed for another application that needs more antennae, such as a fixed wireless access point, or a small base station, another larger antenna panel has typically needed to be designed.
The 5G-NR mmWave communication devices range from a simple IoT device, via smartphones and fixed wireless access points, to devices for non-terrestrial communication as well as base stations. Designing different antenna panels with analog beamforming solutions for each of these use cases comes with a cost.
It would be an advantage to develop a scalable beamforming solution covering several of the use cases above, thereby reducing the development cost and enabling innovation of potential not-yet-known applications (possibly having almost unlimited bandwidth) as is the case in the mmWave radio spectrum.
Fortunately a digital beamforming architecture where one integrates the radio transceiver (RF) chip and antenna in a single encapsulation has this scaling possibility. The radio chip comprises the analog front end radio components, including down and upconverters, taking the mmWave radio signal from mmWave radio frequency down to an analog baseband signal on the receiver side and converting the transmitted analog baseband signal to mmWave radio signals on the transmitter side. The analog baseband signals have a bandwidth corresponding to the 5G-NR mmWave bandwidth and therefore are in the range of 100-400 MHz, those signals being easy to route on the PCB to a digital baseband processor.
The above integrated antenna and RF chip, when combined with digital beamforming algorithms that are implemented in the digital baseband processor, can be tailored to a flexible amount of antennae. Thus a scalable, low cost mmWave implementation for various use cases can be achieved by just applying as many RF chips as are needed for the particular use case. For instance, if we consider a mmWave IoT device that is only transmitting a small amount of data over short ranges, then it may only need two RF chips, plus associated SW that handles beamforming, to be configured for connection to two antennae to create such a device.
A more complex use case relates to a mmWave smartphone implementation. This needs to solve the challenges associated with handheld devices (these have been discussed in previous posts) and therefore need a distributed antenna architecture with, say, 8-16 Antennas and RF chips, with the corresponding digital beamforming algorithms adapted to that amount of antennae. Considering even more complexity, such as a Fixed Wireless Access Point, then 32-64 RF chips may be needed so as to achieve the desired data rate (several Gb/s).
The same set of mmW RF chips are reused for all types of devices. However, in order to meet any requirements for higher transmitting power and better receiver sensitivity, typical for more advanced use cases, then these are solved by adding more RF chips. The level of scaling can also continue to base stations, devices used for non-terrestrial communications such as drones and aeroplanes (requiring 100+ antennae) and to devices communicating with satellites (1000+ antennae). One can even imagine extending the scaling idea of digital beamforming radio architectures to inter-planetary and interstellar communication, where the number of antennae in these cases need to be in the range of hundreds of thousands to hundreds of millions of antennae. However, there might be some challenges with the 5G latency requirements in the communication that need to be solved as well 
BeammWave develops a scalable digital beamforming architecture enabling the mmWave mass market on earth as well as in the sky.
5G, as well as previous generations of cellular communication, relies on standardized communication protocols for the interactions between mobile terminal and the base station. With new and evolved features, and support of higher data rates, the complexity of the standards has increased for each new generation of mobile communication.
Previous generations of cellular communication standards are using frequencies up to about 3 GHz, for which reliable communication can be maintained using one or a few omnidirectional antennas on the terminal side. With the introduction of NR frequency range 2 (24-71 GHz) (FR2), also known as mmWave, this is about to change as the radio propagation path loss at higher frequencies calls for beamforming based on multiple antenna elements to achieve sufficient sensitivity on both transmitter and receiver sides.
At a first glance it may seem that the requirements for beamforming in NR FR2 would only affect the radio front-end parts of the modem in a handheld device or the radio units in the base station, and by that only the radio frequency requirements of the 3GPP specifications. However, basically all aspects of the communication protocol for NR are affected when introducing mmWave communication.
The figure below shows a block scheme over the cellular modem part in a multi-RAT 5G-NR smartphone, supporting all communication generations from 2G to 5G. The modem can be partitioned into (1) radio components supporting the sub 6 GHz communication (i.e. all legacy communication 2G-4G and also the sub 6 GHz communication mode (FR1) in 5G), (2) radio components supporting the mmWave communication introduced in 5G-NR, and (3) a baseband processor performing all algorithms needed to process a received radio signal to an information signal in the receiver and generate a radio signal from the transmitted information signal in the transmitter. The figure also shows which parts of the radio blocks and baseband processor algorithms that need to be updated for mmWave communication, such as (with reference to respective 3GPP standardization document number)
- Radio frequency requirements (38.101-2)
- Demodulation performance requirements (38.101-4)
- Radio resource management (38.133)
- Physical channels and modulation (38.211)
- Physical layer procedures for control and data (38.213, 38.214)
- Physical layer measurements (38.215)
- Media access control (38.321)
- Radio resource control (38.331)
As can be seen mmWave communication is not only about radio design but it affects basically all algorithms and procedures in the modem, from the physical layer, up to the RRC layer .
Figure: a block scheme of a modem in a handheld device and corresponding parts affected by mmWave communication.
BeammWave understands all these aspects of the standard and how mmWave will impact the system design in handheld and fixed wireless devices, as well as in base stations, and will deliver a sustainable, scalable digital beamforming solution that enables the mass market for mmWave communication for 5G-NR.