Reseach

Wireless Communicaions Group

MIMO

図1:MIMO技術を用いた送受信機の構成例

Figure 1: MIMO transceiver technology scheme

MIMO技術とは,無線通信において,送信機と受信機に複数のアンテナを配置し,送受信機間で複数の空間チャネル(伝送路)を形成することで, 従来の単一アンテナ(SISO:Single Input Single Output)システムと比較して, 限られた周波数帯域で伝送速度と伝送品質を大幅に改善可能とすることができる技術である.
上図が,MIMO技術を用いた送受信機の構成例である.


MIMO技術には,複数のアンテナから同一の情報を複数のアンテナを介して同時に送信するSTC(Space Time Coding)方式と, 複数のアンテナから独立の情報を送信するSDM(Space Division Multiplexing)方式に大別される.
STC(Space Time Coding)方式を用いることにより,通信品質・精度の大幅な改善が可能となる.
一方,SDM(Space Division Multiplexing)方式を用いると,伝送容量・速度が大幅に改善される.

MIMO技術は,次世代無線LAN規格IEEE802.11nへの採用が予定されている.
尚,MIMO対応のIEEE802.11g規格の無線LANルータ,カードも開発されている.



MIMO is a technology that can greatly improve the transmission speed and the transmission quality compared with past, single antenna (SISO: Single Input Single Output) system. MIMO technology overcome limited bandwidth by the using two or more antennas in the transmitter and the receiver and formations of two or more space channels (transmission line) between the sending and receiving devices operate in the same frequency in wireless telecommunications.
The above figure is an example of composing the transmitting and receiving apparatus that uses the MIMO technology.


MIMO technology roughly divided into: SDM (Space Division Multiplexing) which is a method to transmit independent information and two or more antennas and STC (Space Time Coding) that is a method to transmit same information from two or more antennas at the same time through two or more antennas.
STC (Space Time Coding) method is use to significantly improve communication quality and precision.
On the other hand, SDM (Space Division Multiplexing) method is used to improve transmission capacity and the speed.


MIMO technology is adopted for next generation wireless LAN standard IEEE802.11n. Wireless LAN router and card of the IEEE802.11g standard for MIMO are developed.


RTL Development

近年,マルチメディアコンテンツの多様化・大容量化に伴い,無線LANの高速化が必要とされている.
現在,無線LAN(Local Area Network)において標準化活動が行われているIEEE802.11n規格では, 既存の無線LAN規格 IEEE802.11a/11b/11gに対してPHY(Physical)層およびMAC(Medium Access Control)層の拡張を行うことで, 100Mbps以上の実行スループットを目標としている.
無線LAN規格 IEEE802.11nに準拠する送受信機システムのモデルベースRTL 設計およびFPGA実装を行っている.



Recently, multimedia contents diversification grows rapidly. Hence, high speed wireless LAN is needed to support it.
Currently, wireless LAN (Local Area Network) activities have been standardized in IEEE802.11n Standard. The existing wireless LAN standard, IEEE802.11a/11b/11g, PHY (Physical) layer and MAC (Medium Access Control) layer throughput is less than 100Mbps.
IEEE802.11n standard-based wireless LAN transceivers that conform to the model of the system design and FPGA RTL implementation is ongoing.



Frame Synchronization

MIMO技術を導入したことにより,従来のSISO(Single-Input Single-Output)伝送で用いていたフレーム同期技術をそのまま用いることは困難である. また,同期点のズレによる性能劣化は,著しく大きいため,MIMO伝送技術に対応するフレーム同期が必要とされている. 現在,IEEE802.11n PHY準拠MIMO無線通信システムのフレーム同期補足方式を提案し,その提案方式がAWGNチャネルやマルチパスフェージングにおいて,良好な性能を示すことを確認している.



In the common data-packet based communication system, synchronization becomes one of the main issues in order to retrieve the received data. Errors during the synchronization stage may cause significant performance degradation. Like in the SISO communication system which uses a synchronization frame or some preamble symbols to detect the start of the data packets, the MIMO communication system also has specific preamble symbols or synchronization frame. In this research, a synchronization method for IEEE 802.11n MIMO wireless communication system has been proposed. It has been verified that the proposed method supports to provide excellent performance either in AWGN channel or multipath channel.





Interference Canceller

MIMO伝送では,受信機において複雑な信号処理を行うことによって空間的に多重化された信号の検出及び複合を行っており,精度や演算量を考慮した様々な干渉キャンセラが提案されている.本研究では,様々なアルゴリズムの演算量と精度の観点から評価を行っている.



In the MIMO communication systems there are many possible interferer signals, not only signals from other communication systems but also interference caused by other streams in MIMO systems, that may interfere the desired received signals. In this research, we compare and verify some interference cancellation techniques performance and complexity. Based on that study, we has been developing some interference cancellation methods which have better accuracy and lower complexity.





Wireless Synchronous Communication System

近年,様々な分野で通信の無線化が行われているが,FA(Factory Automation)においても, 産業用ロボット制御同期通信の無線化が望まれている.現在産業用イーサネットを用いた有 線通信により,高速高精度な同期通信が行われているが,有線による問題だけでなく,企業 独自規格のため,導入コストが高い問題もある. 本研究では,無線LAN規格IEEE802.11acをベースとした,複数ユーザに対して低容量データの 高速周期通信を実現する,FA-WLANシステムの開発を行っている.



Recently, wireless communication is progressing in various fields, and also in the production process of factory automation, wireless of Industrial Ethernet which is used to control synchronous communication of industrial robot is desired. Currently, they communicate with Industrial Ethernet which achieve fast and accurate synchronous communication. However, there are problems not only wired problem but also installation costs because the Industrial Ethernet are proprietary products. In this research, we develop FA-WLAN System based on IEEE802.11 which achieve a fast periodical communication to multiple users with small data.