mmWave WLAN Research Articles

Scaling Multi-User mmWave WLANs: The Case for Concurrent Uplink Transmissions on a Single RF Chain

Today’s mmWave WLANs can realize simultaneous multi-user multi-stream transmission solely on the downlink. In this paper, we present <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</b> plink <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</b> ulti-user <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</b> eamforming on single <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</b> F chain <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</b> P (UMBRA), a novel framework for supporting multi-stream multi-user uplink transmissions via a single RF chain. We design multi-user overlayed constellations and multi-user receiver mechanisms to enable concurrent time-triggered uplink multi-user transmissions received on a single RF chain AP. We devise exemplary beam selection policies to jointly adapt beams at users and the AP for targeting aggregate rate maximization without increasing training requirements compared to single-user systems. We implement the key components of using a programmable WLAN testbed using software-defined radios and commercial 60-GHz transceivers and collect over-the-air measurements using phased-array antennas and horn antennas with varying beamwidth. We find that in comparison to single-user transmissions, achieves more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.45 \times $</tex-math> </inline-formula> improvement in aggregate rate regardless of the choice of the user group, geometric separation, receiver beamwidth, and also under LOS blockage.

CoBF: Coordinated Beamforming in Dense mmWave Networks

With MIMO and enhanced beamforming features, IEEE 802.11ay is poised to create the next generation of mmWave WLANs that can provide over 100 Gbps data rate. However, beamforming between densely deployed APs and clients incurs unacceptable overhead. On the other hand, the absence of up-to-date beamforming information restricts the diversity gains available through MIMO and multi-users, reducing the overall network capacity. This paper presents a novel approach of "coordinated beamforming" (called CoBF) where only a small subset of APs are selected for beamforming in the 802.11ay mmWave WLANs. Based on the concept of uncertainty, CoBF predicts the APs whose beamforming information is likely outdated and needs updating. The proposed approach complements the existing per-link beamforming solutions and extends their effectiveness from link-level to network-level. Furthermore, CoBF leverages the AP uncertainty to create MU-MIMO groups through interference-aware scheduling in 802.11ay WLANs. With extensive experimentation and simulations, we show that CoBF can significantly reduce beamforming overhead and improve network capacity for 802.11ay WLANs.

Low-Complexity User Selection Algorithms for Multiuser Transmissions in mmWave WLANs

In this paper, we propose a low-complexity user selection algorithm for an uplink multiuser transmission in millimeter wave (mmWave) WLAN. We first formulate the user selection problem, taking hybrid beamforming (HBF), an NP-hard problem, into consideration. We then develop a three-step HBF algorithm that incorporates user selection. Specifically, users can be selected based on semi-orthogonality instead of collecting perfect channel state information (CSI) from all potential users. We optimize the digital beamforming to mitigate residual interference among the selected users. Furthermore, we provide analytical validation for the proposed user selection algorithm and study the impact of angle correlation, analog beam pattern, and beamwidth on the achievable rate of the selected users. Extensive simulations validate the performance of the proposed overall HBF algorithm when compared with existing solutions.

Cloud Based mmWave WLANs: Architectural Paradigms, Proposals and Perspectives

With the explosive growth of data traffic over wireless access networks, the use of the millimeter- wave band becomes inevitable due to the spectrum scarcity in lower frequencies and the availability of large chunks of underutilized spectrum in this band. The rapid evolution of wireless technologies and co-existence of legacy and emerging wireless infrastructures are leading to complex network operation scenarios. For instance, to achieve the orchestration of co-existed networks and a large number of devices, dynamic operations of conventional distributed WLANs will become extremely challenging. Various technologies such as dense network deployment, dual-band cooperation, C-RAN, and AI, which have been developed for cellular networks, could be adopted to achieve intelligent and efficient WLAN operations. To meet the future traffic requirements of evolving WLAN, this article first outlines the architecture of future WLAN and the corresponding challenges. A centralized control architecture, named WLAN C-RAN, is proposed to achieve orchestrated coordination and improved network throughput. Critical technologies of WLAN C-RAN, for example, dual-band protocol stack and resource management schemes are also developed, and the simulation results demonstrate the improvements on system capacity. Finally, we present some potential challenges and feasible solutions for the future WLAN.

Study on Indoor Wireless Environment of mmWave WLAN Communication

Study on Indoor Wireless Environment of mmWave WLAN Communication

Heterogeneous control and data sub-network for millimeter-wave communications

Millimeter-wave (mmWave) communications are highly focused as a powerful mean enabling to perform very high data transmission. However it has several inherent shortcomings like directional transmission and serious attenuation in atmosphere. So it is difficult to implement random access in mmWave WLANs. In this paper, a heterogeneous control and data sub-network architecture is presented, which decouples the traditional WLAN into 2.4 or 5GHz control sub-network and mmWave data sub-network in both PHY and MAC layers. In control sub-network, DCF is adopted to transmit control information and in data sub-network, PCF is adopted to ensure the QoS. Moreover, an omnidirectional transmission is employed in the control sub-network to support users� random access. The data sub-network only covers the required serving area by using directional antennas for specific users and can be adjusted dynamically based on control information. Simulations indicate that compared with the conventional WLANs, heterogeneous mmWave WLANs can provide both random access and high throughput.

Empirical capacity of mmWave WLANS

The 60 GHz spectrum gives us the opportunity to deliver gigabit rates to users in a WLAN (wireless local area network) setting. The constrained propagation of signals at this frequency band ensures limited coverage which in turn enables the construction of very efficient STDMA (spatial time division multiple access) schedules. In this paper we study the achievable aggregate capacity in a room when using two types of smart antenna arrays - linear and circular. Using detailed Matlab simulations, we show that with just 400 MHz of the spectrum, aggregate data rates of 9 Gbps (4.5 Gbps) can be achieved with linear (circular) arrays. We also study the energy efficiency of the communication and show that the energy/bit is as low as 0.2 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> (0.2 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> )Joules/Bit by using variable transmit powers at different parts of the room. Finally, we study the problem of coverage due to blocking of the LoS (line of sight) path. To mitigate this problem we study the use of static reflectors and show that coverage in the entire room can indeed be maintained.