Yasuteru Kohda

Wireless data center networking with steered-beam mmWave links

This paper presents a new type of wireless networking applications in data centers using steered-beam mmWave links. By taking advantage of clean LOS channels on top of server racks, robust wireless packet-switching network can be built. The transmission latency can be reduced by flexibly bridging adjacent rows of racks wirelessly without using long cables and multiple switches. Eliminating cables and switches also reduces equipment costs as well as server installation and reconfiguration costs. Security can be physically enhanced with controlled directivity and negligible wall penetration. The aggregate data transmission BW per given volume is expected to scale as the fourth power of carrier frequency. The paper also deals with the architecture of such network configurations and a preliminary demonstration system.

MIMO link design strategy for wireless data center applications

This paper deals with mm Wave MIMO link design strategy for wireless data center applications where the MIMO degrees of freedom is taken into account in multi-node packet networking environments. The problem is treated differently from the coordinated multiuser MIMO situation and the link design is optimized independently in each node with meeting control and data plane requirements for contention-based packet switching. In particular, we propose using an interference-aligned out-of-band control plane to improve the unidirectional bonded in-band data plane collision-related performance degradation with a limited number of antenna elements per node. We also present a high-level implementation plan.

Multi-Gbps 60-GHz single-carrier system using a low-power coherent detection technique

We describe a multi-Gbps 60-GHz single-carrier system using a low-power coherent detection technique. To realize low-power operation at such a high data rate, it is crucial to design the system with reduced oversampling factor and bit depth. A table-based IQ phase rotator and a time-domain polyphase equalizer have been designed for realizing a robust and low-power coherent link under these conditions with rounding-error-free operations and effective interpolations. The entire baseband signal processing is implemented in FPGAs and we are successful in multi-Gbps per-packet transmissions per the IEEE 802.15.3c single-carrier PHY (SC-PHY) format for π/2-BPSK and π/2-QPSK modulations at a full data rate. We confirmed that the 60-GHz single-carrier system can be robust to the carrier and sampling frequency offsets within 50 ppm, even with 2× oversampling factor and 3-bit ADCs, which can lower the power consumption.

Single-channel full-duplex mmWave link using phased-array for Ethernet

In this paper we report on a wireless Ethernet link over 60GHz mmWave, which is a full-duplex wireless link in the same frequency channel. To provide a dense wireless network, beam forming with a phased-array transceiver is a key technology for frequency reuse. We introduced a particle swarm optimization algorithm for beam forming with effective interference cancellation in each field. This method works independent of the transceiver arrangement and is free from device-specific variability and non-linearity. We prototyped the wireless Ethernet link system and achieved a BER less than 1.0E-11 at a 3m distance. We were able to prove its feasibility at system-level application.

Multimedia content-downloading system using millimeter-wave attached memory

This paper presents a high-speed multimedia content-downloading system using 60GHz millimeter wave (mmWave) technology. For a cost-effective solution, the system makes use of conventional 802.11 for the interactive controls between an access point and smart mobile devices, handling such services as access point discovery, authentication, mmWave link establishment, beam steering, and lost packet recovery. The high-speed one-way mmWave link is dedicated to the transfer of content data. The smart mobile device only has an mmWave receiver so that it can keep its power dissipation and hardware costs low. The content data is downloaded from an access point to such a smart mobile device via an external storage component of the mobile device. To use the high bandwidth of the mmWave, the mmWave receiver writes directly to the external storage as a wireless attached memory, which is accessed by the smart mobile device via its SD interface. We built a proof-of-concept prototype with a smartphone receiving data from an mmWave system, and evaluated the performance.

Instant multimedia contents downloading system using a 60-GHZ-2.4-GHZ hybrid wireless link

This paper presents a cost-effective high-speed multimedia-content download system using a hybrid wireless link consisting of a 60-GHz (mmWave) link and a conventional wireless link, such as IEEE 802.11. The capability gap between the components of existing systems and a mmWave link caps system-level performance and degrades resource utilization. We developed an FPGA-based prototype system to investigate system-level performance for well balanced systems. Our performance evaluation involved changing the PHY parameters, data acknowledgement (ACK) methods and link quality. Under the point-to-point network, our results confirmed that a hybrid system with a unidirectional mmWave link using software burst ACK and well optimized packet and burst sizes can achieve competitive performance.

60-GHz single-carrier coherent detection system with robust 16-QAM signal recovery

This paper describes a millimeter wave wireless system using the 60-GHz frequency band, focusing on the data recovery algorithm and implementation to compensate for both the phase noise and the DC offset. Our robust baseband system supports data transfers at 7.04 Gbps using 16-QAM single-carrier with effective digital compensation, an improved adaptive equalizer, and a post-phase rotator and post-shifter. We use a low-overhead frame format without training symbols in the payload and RS(255, 239) as the error correction code so that we can retain spectral efficiency with an effective data rate around 6.6 Gbps with a bit error rate of 4.0E-5 at 3 m distance. Our results show how millimeter wave technology can provide higher data rates and higher aggregated channel capacities for future dense networks.