Fumihide Kojima

Beam codebook based beamforming protocol for multi-Gbps millimeter-wave WPAN systems

In order to realize high speed, long range, reliable transmission in millimeter-wave 60 GHz wireless personal area networks (60 GHz WPANs), we propose a beamforming (BF) protocol realized in media access control (MAC) layer on top of multiple physical layer (PHY) designs. The proposed BF protocol targets to minimize the BF set-up time and to mitigate the high path loss of 60 GHz WPAN systems. It consists of 3 stages, namely the device (DEV) to DEV linking, sector-level searching and beam-level searching. The division of the stages facilitates significant reduction in setup time as compared to BF protocols with exhaustive searching mechanisms. The proposed BF protocol employs discrete phase-shifters, which significantly simplifies the structure of DEVs as compared to the conventional BF with phase-and-amplitude adjustment, at the expense of a gain degradation of less than 1 dB. The proposed BF protocol is a complete design and PHY-independent, it is applicable to different antenna configurations. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. Furthermore, based on the codebooks with four phases per element, around 15.1 dB gain is achieved by using eight antenna elements at both transmitter and receiver, thereby enabling 1.6 Gbps-data-streaming over a range of three meters. Due to the flexibility in supporting multiple PHY layer designs, the proposed protocol has been adopted by the IEEE 802.15.3c as an optional functionality to realize Gbps communication systems.

Beamforming Codebook Design and Performance Evaluation for 60GHz Wideband WPANs

The paper proposes a codebook design to support beamforming mechanism in a wide band millimeter-wave 60GHz wireless personal area networks (60GHz WPANs) in a realistic millimeter-wave environment. The codebooks are designed sym- metrically in order to mitigate the possible beam shift due to the large differences of wave lengthes at different sub-bands of a wide band communication system. In order to provide a high data rate and high performance with minimum power consumption in 60GHz systems, the codebooks are generated with 90 degree phase resolution without amplitude adjustment. The codebooks are designed for different numbers of antenna elements, supporting a multitude of antenna configurations. The paper provides codebook design mechanism, some example codebooks and some analysis on antenna gain loss due to phase shift errors of phase shifters. Simulation results shows that: (1) To keep the gain loss at the intersections of any two patterns inside the codebook lower than 1dB, the number of patterns inside the codebook shall be at least 2 times of the number of antenna elements used for pattern generation; (2) The designed codebooks are robust to phase shift errors: the gain loss is lower than 1dB with only 10% outage probability when standard deviation of phase shift errors at phase shifters is 0.5 (28.6 degree). The proposed codebooks are a feasible design, they are the key basis of the beamforming protocol in 60GHz WPANs (IEEE 802.15.3c).

A design of single carrier based PHY for IEEE 802.15.3c standard

This paper proposes an air interface for ultra high-speed millimeter wave (60 GHz) systems which have been under standardization process at IEEE 802.15.3c: the proposed channel plan permits ease of portable device implementation employing the major crystal oscillator used in CDMA cellar phones. The proposed transmission modes offer much greater scalability, covering from several tens Mbps to over 4 Gbps. The proposed preamble employs Golay codes, providing sufficient robustness against wireless environment being subject to the characteristics of millimeter wave with reduced hardware complexity. Common mode is a novel technique to communicate with single carrier (SC) and OFDM camps with multi rates up to around 1.5 Gbps. This technique gives the proposed systems easy expandability from SC to OFDM or other SCs and vice versa.

Beam Codebook Based Beamforming Protocol for Multi-Gbps Millimeter-Wave WPAN Systems

In this paper, we propose a feasible beamforming (BF) scheme realized in media access control (MAC) layer following the guidelines of the IEEE 802.15.3c criteria for millimeter-wave 60GHz wireless personal area networks (60GHz WPANs). The proposed BF targets to minimize the BF set-up time and mitigates the high path loss of 60GHz WPAN systems. It is based on designed multi-resolution codebooks, which generate three kinds of patterns of different half power beam widths (HPBWs): quasi-omni pattern, sector and beam. These three kinds of patterns are employed in the three stages of the BF protocol, namely device-to-device (DEV-to-DEV) linking, sector-level searching and beam-level searching. All the three stages can be completed within one superframe, which minimizes the potential interference to other systems during BF set-up period. In this paper, we show some example codebooks and provide the details of BF procedure. Simulation results show that the setup time of the proposed BF protocol is as small as 2% when compared to the exhaustive searching protocol. The proposed BF is a complete design, it re-uses commands specified in IEEE 802.15.3c, completely compliant to the standard; It has thus been adopted by IEEE 802.15.3c as an optional functionality to realize Giga-bit-per-second (Gbps) communication in WPAN Systems.

Relay with deflection routing for effective throughput improvement in Gbps millimeter-wave WPAN systems

In this paper, we propose a deflection routing scheme that improves effective throughput (defined as the successfully transmitted bits over the duration between two available sequential time slots) of millimeter-wave wireless personal area network (mmWave WPAN) systems. The upcoming mmWave WPAN is based on dynamic time division multiple access (TDMA) and designed to guarantee Gbps-order transmission capability for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. The decode-and-forward (DF) type of relay offers a simple solution to the issues of mmWave WPAN systems, such as limited coverage range and unexpected blockage. However, due to the required extra time, DF relay on the other hand decreases the effective throughput, and may not be sufficient to satisfy the requirement of the above data-rate-greedy applications. Inspired by the fact that the significant path loss of a millimeter-wave environment can provide good space isolation, we propose a deflection routing scheme to improve the effective throughput by sharing time slots for direct path with relay path. Based on the sub-exhaustive search, a routing algorithm, named as best fit deflection routing (BFDR), has been developed to find the relay path with the least interference that maximizes the system throughput. To reduce the computational complexity of the BFDR, we have also developed a sub-optimal algorithm named as random fit deflection routing (RFDR). The RFDR algorithm finds the sub-optimized relay path, where the interference may not be the least but is sufficiently low to guarantee the concurrent transmissions. Computer simulations show that, in realistic 60 GHz environments, the effective system throughput can be improved up to 28% under grid topology and 35% under random topology. RFDR achieves almost the same order of throughput improvement with only 10% of the computational complexity of BFDR.

MAC Enhancement for High Speed Communications in the 802.15.3c mmWave WPAN

Millimeter-wave (mmWave) is highly focused as a powerful mean enabling to perform very high data transmission. This paper proposes the enhancement of media access control (MAC) for the mmWave WPAN. The existing MACs have limits to achieve high data transmission over 1–2 Gbps by reasons of the low frame transmission efficiency and the high overhead of signal exchanges. In addition, the transmitting frames need to be protected in a poor channel condition for the high quality of service. The proposed MAC provides frame aggregation with unequal error protection (UEP) and block acknowledgment (Blk-ACK), which can solve the problems of the existing MACs and guarantee the high quality of service. Our theoretical throughput analysis shows that the proposed MAC does the high throughput enhancement compared to the existing MACs and achieves the MAC throughput over 2Gbps in the mmWave WPAN.

Necessary Modifications on Conventional IEEE802.15.3b MAC to Achieve IEEE802.15.3c Millimeter Wave WPAN

To achieve ultra high speed (several gigabits/s) transmission over 60 GHz system efficiently, this paper proposes Automatic Device Discover (ADD) and frame aggregation. The computer simulation results show good feasibility of handling directional antenna for ultra high speed transmission and highly efficient transmission up to 87 percent over 4.094 Gbps PHY-SAP with 8PSK modulation.

Coexistence of homogeneous and heterogeneous systems for IEEE 802.15.4g smart utility networks

This paper presents the overview on coexistence of homogeneous and heterogeneous systems for the IEEE 802.15.4g Smart Utility Network (SUN), a low rate wireless personal area network (WPAN) standard for advanced utility service. The 802.15.4g specifies three alternative physical (PHY) layer designs, thus having multiple homogeneous systems within the SUN system. The three homogeneous systems are allocated across shared frequency bands dependent on different regulatory domains. Besides coexistence for homogeneous systems, the SUN system is also sharing several frequency bands with multiple heterogeneous systems across various other 802 standards. Understanding the details of these coexisting dissimilar systems is an essential step to creating a harmonious radio environment. Therefore, this paper provides the outline of the coexisting homogeneous and heterogeneous systems, as well as the corresponding frequency bands that are allocated in different regulatory domains. Secondly, the overview on the coexistence mechanisms applicable in the 802.15.4g system is presented. Thirdly, coexistence analysis is performed on two dissimilar systems, where the performance degradation of a victim system is evaluated in the presence of an interferer. As a collective result, it is shown that with victim-interferer separation of beyond approximately 30m, dissimilar systems are able to coexist even without higher layer coexistence mechanisms.

Directional Relay with Spatial Time Slot Scheduling for mmWave WPAN Systems

In this paper, we propose a spacial time slot scheduling algorithm for relay operation to improve the throughput performance of millimeter-wave wireless personal area network (mmWave WPAN) systems which employ directional antenna. The upcoming mmWave WPAN is designed for high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. Based on the fact that the significant path loss of millimeter-wave environments provides good space isolation, we have proposed a coexistence mechanism by sharing time slots for relay with direct transmission to guarantee throughput for the above data-rate-greedy applications. This paper is an extension that addresses spacial time slot scheduling for relay operation taking the effect of directional antenna into consideration. We model the throughput maximization with scheduling as an integer optimization and solve it by transforming the problem to a max-weight matching problem of a bipartite graph. We propose a scheduling algorithm based on the Kuhn-Munkres algorithm which can be used to solve the max weight matching problem. Simulation results show that there is up to 25% throughput improvement achieved compared with random scheduling method.

On-demand device discovery enhancement of IEEE802.15.3 MAC for 60GHz WPAN system

Because of the unknown position of devices in ad-hoc network, it is difficult for the MAC to discover other devices by using directional antenna. This device discovery procedure needs extra signaling and costs considerable time, especially if there are a lot of devices. In this paper, on top of IEEE 802.15.3 MAC, we introduce the ultra superframe concept and propose an on-demand device discovery mechanism that significantly reduces signaling overhead, therefore speeds up the device discovery process and increases channel efficiency. Computer simulations show that, assuming up to 64 uniformly distributed devices, this MAC enhancement accomplishes device discovery procedure within 200 ms while keeping channel efficiency over 70% under 60 GHz channel environment.