Tuesday, 9 April 2019

Distributed Massive MIMO using Ericsson Radio Stripes

One of the interesting things that caught my attention in MWC 2019 was the Ericsson Radio Stripes.

Emil Björnson explains it nicely in his blog as to how this works.

Distributed MIMO deployments combine the best of two worlds: The beamforming gain and spatial interference suppression capability of conventional Massive MIMO with co-located arrays, and the bigger chance of being physically close to a service antenna that small cells offer. Coherent transmission and reception from a distributed MIMO array is not a new concept but has been given many names over the years, including Distributed Antenna System and Network MIMO. Most recently, in the beyond-5G era, it has been called ubiquitous Cell-free Massive MIMO communications and been refined based on insights and methodology developed through the research into conventional Massive MIMO.

One of the showstoppers for distributed MIMO has always been the high cost of deploying a large number of distributed antennas. Since the antennas need to be phase-synchronized and have access to the same data, a lot of high-capacity cables need to be deployed, particularly if a star topology is used. 

For those who cannot attend MWC, further conceptual details can be found in a recent overview paper on Cell-free Massive MIMO. An even more detailed description of radio stripes can be found in Ericsson’s patent application from 2017.

The paper explains the Radio stripe system design and also lists the advantages of such a system:

The radio stripe system facilitates a flexible and cheap cell-free Massive MIMO deployment. Cheapness comes from many aspects: (i) deployment does not require highly qualified personnel. Theoretically, a radio stripe needs only one (plug and play) connection either to the front-haul network or directly to the CPU; (ii) a conventional distributed massive MIMO deployment requires a star topology, i.e., a separate cable between each APs and a CPU, which may be economically infeasible. Conversely, radio stripe installation complexity is unaffected by the number of antenna elements, thanks to its compute-and-forward architecture. Hence, cabling becomes much cheaper; (iii) maintenance costs are cut down as a radio stripe system offers increased robustness and resilience: highly distributed functionality offer limited overall impact on the network when few stripes being defected; (iv) low heat-dissipation makes cooling systems simpler and cheaper. While cellular APs are bulky, radio stripes enable invisible installation in existing construction elements as exemplified in Fig. below. Moreover, a radio stripe deployment may integrate for example temperature sensors, microphones/speakers, or vibration sensors, and provide additional features such as fire alarms, burglar alarms, earthquake warning, indoor positioning, and climate monitoring and control.

According to the Ericsson post:

One of the inventors and researchers behind the concept, Jan Hederén, Strategist at Ericsson 4G5G Development, says: 

"Although a large-scale installation of distributed MIMO can provide excellent performance, it can also become an impractical and costly "spaghetti-monster" of cables in case dedicated cables are used to connect the antenna elements.

To be easy to deploy, we need to connect and integrate the antenna elements inside a single cable. We call this solution the "radio stripe" which is an easy way to create a large scale distributed, serial, and integrated antenna system." Says, also inventors and researcher behind the concept."

This visionary concept is an extension of how to build and enhance the capability of current networks. The Radio Stripe systems offers, so to say, new colors and flavors in how we increase the performance of mobile networks.

The Radio Stripe vision is focused on improvements to the reach and quality of radio connectivity in the access part of the mobile network. It shares all other resources (transport, baseband, management, core) with current mobile solutions.

I am looking forward to reading a lot more about this kind of approach in the future and probably some deployment videos too.

Related post:


I am running a webinar this week looking at 5G @ MWC 2019 on behalf of Parallel Wireless (#PWTechTrain) . Along with antennas, I plan to talk about lot more things. Register here.

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