Adaptive Momentum-Based Motion Detection Approach and Its Application on Handoff in Wireless Networks

Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., power consumption and monetary cost) and supply systems (e.g., network fingerprint server). This paper proposes a Momentum of Received Signal Strength (MRSS) based motion detection method and its application on handoff. MRSS uses the exponentially weighted moving average filter with multiple moving average window size to analyze the received radio signal. With MRSS, an MN can predict its motion state and make a handoff trigger at the right time without any assistance from positioning systems. Moreover, a novel motion state dependent MRSS scheme called Dynamic MRSS (DMRSS) algorithm is proposed to adjust the motion detection sensitivity. In our simulation, the MRSS- and DMRSS-based handoff algorithms can reduce the number of unnecessary handoffs up to 44% and save battery power up to 75%

Mobility-based predictive call admission control and resource reservation for next-generation mobile communications networks.

Recently, the need for wireless and mobile communications has grown tremendously and it is expected that the number of users to be supported will increase with high rates in the next few years. Not only the number of users, but also the required bandwidth to support each user is supposed to increase especially with the deploying of the multimedia and the real time applications. This makes the researchers in the filed of mobile and wireless communications more interested in finding efficient solutions to solve the limitations of the available natural radio resources. One of the important things to be considered in the wireless mobile environment is that the user can move from one location to another when there is an ingoing call. Resource reservation ( RR ) schemes are used to reserve the bandwidth ( BW ) required for the handoff calls. This will enable the user to continue his/her call while he/she is moving. Also, call admission control ( CAC ) schemes are used as a provisioning strategy to limit the number of call connections into the network in order to reduce the network congestion and the call dropping. The problem of CAC and RR is one of the most challenging problems in the wireless mobile networks. Also, in the fourth generation ( 4G ) of mobile communication networks, many types of different mobile systems such as wireless local area networks ( WLAN s) and cellular networks will be integrated. The 4G mobile networks will support a broad range of multimedia services with high quality of service.New Call demission control and resource reservation techniques are needed to support the new 4G systems. Our research aims to solve the problems of Call Admission Control (CAC), and resource reservation (RR) in next-generation cellular networks and in the fourth generation (4G) wireless heterogeneous networks. In this dissertation, the problem of CAC and RR in wireless mobile networks is addressed in detail for two different architectures of mobile networks: (1) cellular networks, and (2) wireless heterogeneous networks (WHNs) which integrate cellular networks and wireless local area networks (WLANs). We have designed, implemented, and evaluated new mobility-based predictive call admission control and resource reservation techniques for the next-generation cellular networks and for the 4G wireless heterogeneous networks. These techniques are based on generating the mobility models of the mobile users using one-dimensional and multidimensional sequence mining techniques that have been designed for the wireless mobile environment. The main goal of our techniques is to reduce the call dropping probability and the call blocking probability, and to maximize the bandwidth utilization n the mobile networks. By analyzing the previous movements of the mobile users, we generate local and global mobility profiles for the mobile users, which are utilized effectively in prediction of the future path of the mobile user. Extensive simulation was used to analyze and study the performance of these techniques and to compare its performance with other techniques. Simulation results show that the proposed techniques have a significantly enhanced performance which is comparable to the benchmark techniques

環境適応型ベースバンド無線に関する研究

近年，周波数枯渇の問題解決策として，コグニティブ無線の研究が盛んになっている．コグニティブ無線は，電波利用状況や電波伝搬特性を認識することにより，最適なパラメータを自律的に判断して，時々刻々変化する環境に適応した通信を行うことである．環境適応通信を実現するためには，通信パラメータを柔軟に制御する必要があり，プログラミングによって様々な無線機の機能を実現するソフトウェア無線技術が重要な役割を担っている．従来の無線通信は，低い周波数帯域で信号処理をし，高い周波数帯へ変調してから，アンテナより電波を送出して通信を行っている．将来的には，D/A 変換器やA/D 変換器などの処理性能が上がり，ベースバンド信号をそのままアンテナから送信するという時代が来ることも予想できる．この機能を実現する先駆的な研究として，ベースバンドの連続波形(アナログ波形)を実空間に放射する「無線ベースバンド伝送」が提案されている．しかし，超広帯域なスペクトルを連続的に占有するため，干渉対策や電波法的な面で応用上の問題がある．無線ベースバンド伝送の問題を克服した方式として，環境適応型ベースバンド無線がある．ベースバンド無線とは，デｨジタル信号処理で得た信号を直接D/A 変換器に送り出し，電波領域を含む高周波帯域信号そのものもベースバンド信号として扱う無線システムである．ベースバンド無線，ソフトウェア無線及びコグニティブ無線の技術が一体化したのが「環境適応型ベースバンド無線」である．先行技術としての環境適応型ベースバンド無線の提案では，原理確認のため，コイルを用いた磁界結合による伝送実験を行っている．しかしながら，実際の電波環境(マルチパス伝搬環境，干渉波が存在する環境など)での実現評価や問題点の抽出，その対策技術にまで及んでいない．また、ベースバンド無線の特徴を生かした新しい通信方式の開拓も必要になっている．さらに，ベースバンド無線では，バンドフリーの状態で広帯域な周波数空間を縦横に利用するため，受信系でも広帯域で待ち受ける必要があるが，そのような待ち受けをしていると，突発的に強い干渉波が待ち受け帯域内に入射する場面が起き，その際の受信系飽和（非線形問題）による特性劣化が問題になる．このため，受信フロントエンドでの干渉波抑圧が必要になる．本論文では，二つの問題をテーマとする．一つは，環境適応型ベースバンド無線に適した伝送方式の提案と，マルチパス環境での原理実証である．二つ目は，広帯域待ち受け受信に起因する，強い干渉波の入力に伴う受信増幅器の非線形問題の解析と対策技術提案である．第一の通信方式の提案では，環境適応型ベースバンド無線の理想の姿として，制御チャネルを用いて周波数空間に任意にデータが配置でき，かつ，環境変化にフレキシブルに対応する周波数領域パケット通信の概念を提示し，電波暗室及び電波反射箱を用いたマルチパス環境で定量的評価を行い，柔軟な情報伝送が可能であることを実証している.また，第二の提案の，受信系の非線形問題と対策の研究では，干渉周波数認識と抑圧法に，環境適応性を採り入れた独自の方法（ベースバンド無線の特徴を生かしたスペクトル制御法）を提案している．これについても，電波反射箱を用いたマルチパス環境下での実証実験を行い，問題の定量的評価と，対策法の有効性を明らかにしている．電気通信大学201