A new era of automation and the explosion of IoT will shape the future wireless connectivity landscape, featuring scalable, energy-efficient, high-throughput, ultra-reliable, and low-latency wireless communication systems. These systems have stringent connectivity requirements, which may be very diverse for different applications. For instance, for emerging industrial automation use cases, the latency and cycle times can be less than 1-2 ms, data jitter requirements may be as low as 1 μs for some use cases, while throughputs are rather moderate. In addition, reliable end-to-end connectivity (of at least 99.9999%) must be guaranteed across the plant under dynamic and challenging wireless conditions (lots of metal and obstacles, moving robotic arms, AGVs...). Therefore, the design of end-to-end (E2E) connections becomes very challenging.
To establish more robust wireless systems, radio access is evolving from a cell-centric deployment where different users connect to a single access point (AP), to a user-centric paradigm where one user is connected to multiple cooperating APs. This emerging architecture is referred to as cell-free massive MIMO (CF- mMIMO) systems. Many distributed and coordinated APs offer improved radio access coverage, higher resilience to inter-cell-interference, and increased macro-diversity. A CF-mMIMO architecture allows uniform coverage as any wireless client device can always be served by a subset of APs, for instance, the nearest (line-of-sight) APs, which guarantees dead-spot free coverage at any time and at any location. According to recent theoretical studies, the CF-mMIMO technology is expected to provide a 10x improvement in spectral efficiency compared to a traditional small-cell network. Simulations predict a 5 to 20 dB higher channel gain owing to the cell-free network paradigm.
Despite the very promising performance gains predicted through extensive theoretical and simulation studies, there is still a huge gap towards the practical realization of the CF-mMIMO concept. The current research is mostly heading towards theoretical complex signal processing unhindered by limited hardware (HW) capabilities, deployment cost, energy efficiency and fronthauling (FH) technology, to name a few. There are only limited experiments and demonstrations. For instance, at the industrial side, main 5G players Nokia and AT&T, collaborated on a proof-of-concept technology where they process signals of two 5G mMIMO base stations to increase the uplink speed and capacity. However, such macro-cell base stations are extremely expensive and not suitable for smaller-scale private deployments. In the research community, CF-mMIMO research infrastructures generally consist of a large set of expensive Software Defined Radios (SDRs) that are connected to a centralized multi-FPGA card using inflexible and costly coaxial cabling seriously limiting scalability and reach. In addition, in most testbeds, PHY processing is done in software (SW) limiting the capabilities for real-time E2E applications and latency-sensitive protocols.
In this project, we aim to validate a low-cost Cell Free massive MIMO solution for ultra-reliable and low- latency wireless communication based on Wi-Fi technology.
