CTO Series: 3 | Overcoming mmWave complexities

22nd June 2022 by Ray McConnell

In the third blog in our ‘mmWave and the 5G wireless revolution’ series, CTO and Founder Ray McConnell explores how the complexities related to mmWave wireless technology are overcome to unlock the new possibilities that mmWave technology presents.

mmWave wireless technologies offer ultra-fast, low latency networks that provide impressive advantages for companies that require high performance wireless for applications such as backhaul to trains, fronthaul to 5G small cells, or high-speed data upload from mobility based systems such as on board CCTV systems or captured sensor data.

But mmWave technologies also come with some complexities due to their high frequencies.

The physics of propagation means the channel pathloss increases by the square of the frequency. As we move to higher frequencies the antenna becomes smaller with the shorter wavelength. Essentially a 10x increase of the operating frequency can lead to a 100x increase in losses.

High frequency pathloss is overcome by scaling antenna size independently of wavelength

Recent advances in high-speed, mixed-signal integration with low-cost digital circuits provide high-speed radio frequency (RF) analogue and smart digital systems combined into a single device. These integrated RF subsystems integrate all the RF systems including Power Amplifiers (PAs) antenna drivers, which are directly controlled from the digital system.

The single chip RF subsystem is mounted closely on a specialised Printed Circuit Board (PCB) with an array of antenna. Increasing the number of both the TX and RX antennas, means that the physical size of the antenna array can be, to a first order, independent of the frequency. It also allows increases in the scaling of power.

Fine phase control of each antenna means a low-cost beamforming Phased Array antenna is created. The on-board digital controller has high speed selective control of each of the PAs, which provides a rapid selection of a number of beams, known as a beam book, to both the TX and RX antennas.

By rapidly choosing which beam book index to use, the system can control the direction of high gain beams. Thus any pathloss associated with the physics of high frequency mmWave is then managed with the use of smart high gain, electronically steered beamforming.

To help you assess the capacity of mmWave systems, Blu Wireless has created a link budget calculator. It is a useful tool to analyse and experiment with range and throughput estimation for a point-to-point connection.

Automated mmWave beam management for wide area mesh networks and why it’s needed

But with beamforming, a receiver RX device can be completely deaf to a TX antenna if its RX beam is not pointing at the TX, and vice versa. This has two rather fundamental outcomes, classic omni based collision detect CSMA/DCF WiFi protocols no longer work and reuse of interference free spectrum in dense scenarios is a reality.

From this we see that mmWave beams need to be carefully managed to ensure systems can communicate. At Blu Wireless, we use a Directional Media Access Controller (DMAC) to automatically manage these (and other) mmWave wireless complexities associated with beam management.

The DMAC initially performs a beam search, so devices can locate each other. Once located, the DMAC shares management information between the devices, creating a link. Then further management exchanges take place between the devices, known as an association.

From then on, the DMAC automatically maintains the association of mmWave beams with the network MAC address it learned in the association. This maps a conventional network onto the links that the beams provide. From this a conventional network can be established, including the complex network security management.

The DMAC responds to the network MAC address of each packet to schedule slots with the directional beam of each associated device, and also slots for upload and download traffic according to the network load. Both aspects are runtime data dependant activities that respond efficiently to the actual network load requirements.

There are many different connectivity options, depending on the application. The simplest is single point to point connection (PtP) between an Access Point (AP) and a Station. Useful for massive ad-hoc data upload applications, where a bus or train pulls into a station and has a short interval to upload a large amount of on-board data it has collected on the journey.

An AP can also manage multiple Station devices, which is known as a Point to Multi-Point (PtMP) system. This allows multiple wireless devices to participate in a DMAC orchestrated shared schedule and which can operate over a wide physical area. This is useful for broadband access distribution networks or adding redundant connections to moving vehicles.

Multiple APs can be formed into a hub with 360o of connectivity, automatically choosing a directional AP to steer traffic to any quadrant branch. Using an additional connectivity layer, multiple hubs are able to associate and connect to form a wide area mesh network, stretching over many kilometres, useful for fronthauling of street based 5G-NR small cells.

Bringing all this together, we see multiple connectivity layers autonomously forming and maintaining secure, failsafe 5G mmWave multi-gigabit wireless networks that can scale over wide areas and can even connect to high-speed moving vehicles.

If you’ve followed this whistle stop tour of mmWave beam management, you may start to see the benefits of 5G mmWave and why we’re building products for high-speed train backhaul, products for fronthauling 5G-NR small cells and products for secure military vehicular applications.

If you’re interested in learning more about Blu Wireless, get in touch with us today.