Periodic Reporting for period 1 - DCAP (Distributed Coordinated Access Point)
Periodo di rendicontazione: 2024-07-01 al 2025-12-31
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.
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.
The following research innovations were explored:
- Accurate time synchronization of the distributed APs with the Bit-Interleaved Sigma-Delta-Over-Fiber Fronthaul Network (BISDoF). This novel fronthaul solution uses low-cost commercial optical transceiver modules connected with multi-mode optical fiber and is hence way more cost-effective and flexible than coaxial cables. A time synchronization accuracy below 10 ps is targeted.
- Low-latency operation of distributed APs by exploiting the new OFDMA (Orthogonal Frequency Division Multiple Access) feature in the Wi-Fi 6 standard and extending it with beyond Wi-Fi 6 and Wi-Fi 7 capabilities in UGent-IDLab’s open full-stack openwifi prototyping platform with embedded wireless Time-Sensitive Networking (TSN) capabilities.
- Full compliance of the highly customized APs with Wi-Fi 6 Commercial-Of-The-Shelf (COTS) clients.
- Distributed beamforming by coherently combining Resources Units (RUs) from multiple distributed APs, thereby adding an extra degree of flexibility and scalability to the system, as different RUs (subsets ofOFDMA subcarriers) in the same channel can simultaneously serve different Wi-Fi clients.
During the DCAP project, the ATTO fronthaul network has been adapted for integration with the openwifi platform . The openwifi platform has been extended towards distributed operation to enable multiuser coordinated OFDMA. Its performance has been verified and compliancy with the Wi-Fi standard has been validated. Besides these technical work packages also a pathway towards valorisation of the technology has been explored. Currently openwifi, including the beyond standard features developed in DCAP, is offered via a subscription model to industrial partners. Initial agreements have been signed and with multitude of partners initial discussions are still ongoing.
- Accurate time synchronization of the distributed APs with the Bit-Interleaved Sigma-Delta-Over-Fiber Fronthaul Network (BISDoF). This novel fronthaul solution uses low-cost commercial optical transceiver modules connected with multi-mode optical fiber and is hence way more cost-effective and flexible than coaxial cables. A time synchronization accuracy below 10 ps is targeted.
- Low-latency operation of distributed APs by exploiting the new OFDMA (Orthogonal Frequency Division Multiple Access) feature in the Wi-Fi 6 standard and extending it with beyond Wi-Fi 6 and Wi-Fi 7 capabilities in UGent-IDLab’s open full-stack openwifi prototyping platform with embedded wireless Time-Sensitive Networking (TSN) capabilities.
- Full compliance of the highly customized APs with Wi-Fi 6 Commercial-Of-The-Shelf (COTS) clients.
- Distributed beamforming by coherently combining Resources Units (RUs) from multiple distributed APs, thereby adding an extra degree of flexibility and scalability to the system, as different RUs (subsets ofOFDMA subcarriers) in the same channel can simultaneously serve different Wi-Fi clients.
During the DCAP project, the ATTO fronthaul network has been adapted for integration with the openwifi platform . The openwifi platform has been extended towards distributed operation to enable multiuser coordinated OFDMA. Its performance has been verified and compliancy with the Wi-Fi standard has been validated. Besides these technical work packages also a pathway towards valorisation of the technology has been explored. Currently openwifi, including the beyond standard features developed in DCAP, is offered via a subscription model to industrial partners. Initial agreements have been signed and with multitude of partners initial discussions are still ongoing.
The adapted fronthaul has been demonstrated towards industrial partners to show case the effect of distributed versus centralized processing of signals and to evaluate the effect of channel hardening obtained using distributed antenna placement. Novel algorithms were demonstrated that optimized power allocation. This enabled error-free simultaneous reception of four closely spaced users in a test set-up.
The openwifi’s original Wi-Fi 4 module has been extended with distributed and Coordinated OFDMA (Co-OFDMA) functionality. In the distributed Co-OFDMA setup, one AP acts as master and the other one acts as slave, the synchronization and coordination between two APs are achieved via a fiber link. Experimental validation shows the carrier frequency offset of the two boards stabilizes around 100 Hz with the fiber-based synchronization. Very clear advantages were illustrated in an experimental set-up where the throughput was doubled for shorter packets (order 500 Bytes).
Standard compliance of the results was confirmed.
More info on the Open-Wifi website: both technical information as well as commercial information(si apre in una nuova finestra).
The openwifi’s original Wi-Fi 4 module has been extended with distributed and Coordinated OFDMA (Co-OFDMA) functionality. In the distributed Co-OFDMA setup, one AP acts as master and the other one acts as slave, the synchronization and coordination between two APs are achieved via a fiber link. Experimental validation shows the carrier frequency offset of the two boards stabilizes around 100 Hz with the fiber-based synchronization. Very clear advantages were illustrated in an experimental set-up where the throughput was doubled for shorter packets (order 500 Bytes).
Standard compliance of the results was confirmed.
More info on the Open-Wifi website: both technical information as well as commercial information(si apre in una nuova finestra).