Channel estimation and transmit power control in wireless body area networks

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on-body to on-body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature

Diseños de capa cruzada para redes inalámbricas de área corporal energéticamente eficientes: una revisión

RESUMEN: El diseño de capa cruzada se considera una poderosa alternativa para dar solución a las complejidades introducidas por las comunicaciones inalámbricas en redes de área corporal (WBAN), donde el modelo clásico de comunicaciones no ha exhibido un desempeño adecuado. Respecto al problema puntual de consumo de energía, hemos preparado la presente revisión de las publicaciones más relevantes que tratan la eficiencia energética para WBAN usando diseño de capa cruzada. En este artículo se proporciona una revisión exhaustiva de los avances en aproximaciones, protocolos y optimizaciones de capa cruzada cuyo objetivo es incrementar el tiempo de vida de las redes WBAN mediante el ahorro de energía. Luego, se discute los aspectos relevantes y deficiencias de las técnicas de capa cruzada energéticamente eficientes. Además, se introducen aspectos de investigación abiertos y retos en el diseño de capa cruzada para WBAN. En esta revisión proponemos una taxonomía de las aproximaciones de capa cruzada, de modo que las técnicas revisadas se ajustan en categorías de acuerdo a los protocolos involucrados en el diseño. Una clasificación novedosa se incluye para hacer claridad en los conceptos teóricos involucrados en cada esquema de capa cruzada y para luego agrupar aproximaciones similares evidenciando las diferencias con otras técnicas entre sí. Nuestras conclusiones consideran los aspectos de movilidad y modelamiento del canal en escenarios de WBAN como las direcciones para futura investigación en WBAN y en aplicaciones de telemedicina.ABSTRACT: Cross-layer design is considered a powerful alternative to solve the complexities of wireless communication in wireless body area networks (WBAN), where the classical communication model has been shown to be inaccurate. Regarding the energy consumption problem, we have prepared a current survey of the most relevant scientific publications on energy-efficient cross-layer design for WBAN. In this paper, we provide a comprehensive review of the advances in cross-layer approaches, protocols and optimizations aimed at increasing the network lifetime by saving energy in WBANs. Subsequently, we discuss the relevant aspects and shortcomings of these energy-efficient cross-layer techniques and point out the open research issues and challenges in WBAN cross-layer design. In this survey, we propose a taxonomy for cross-layer approaches to fit them into categories based on the protocols involved in the cross-layer scheme. A novel classification is included to clarify the theoretical concepts behind each cross-layer scheme; and to group similar approaches by establishing their differences from the other strategies reviewed. Our conclusion considers the aspects of mobility and channel modeling in WBAN scenarios as the directions of future cross-layer research for WBAN and telemedicine applications

Energy-efficient Two-hop Extension Protocol for Wireless Body Area Networks

[[abstract]]Recent technological advances in integrated circuits, wireless communications and physiological sensing have allowed ultra-low power, intelligent-monitoring tiny devices to settle around the human body, forming a wireless body area network (WBAN) to collect information for a particular purpose. As these tiny devices are low-weighted and energy-restricted, ‘energy efficiency’ becomes a key issue. Built in 2012 to facilitate the development of WBAN, the ‘IEEE 802.15.6’ standard operates with one-hop star and two-hop restricted tree topologies. Its two-hop extension protocol has relaying nodes (working as a microhub), process node joining and schedule two-hop transmissions, thus reducing their lifetime. To reduce the energy consumption and overhead for relaying nodes, the authors introduce a new two-hop extension protocol which lets the generally better resource-equipped hub directly transmit packets to the downlink relayed nodes. Analytical and experimental evaluations show that when advancing ‘IEEE 802.15.6’ in extending the lifetime of relaying nodes with less energy consumption and overhead, the authors’ new protocol also retains its advantages, including longer lifetime for relayed nodes and lower bit error rates.[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子

[[alternative]]An energy-efficient two-hop extension protocol for wireless body area networks

博士[[abstract]]隨著無線通訊技術的進步，越來越多的新應用陸續被提出來，例如：穿戴式或置入式的生理感測器。這些生理感測器被安置在人體皮膚上，或內置於身體內，或安裝在身體周圍收集資訊形成無線人體區域網路。這些生理感測器通常很輕薄，並且能源有限，因此能源效率就變成無線人體區域網路中最重要的問題了。 IEEE 802.15.6工作群組在2012年二月制定並發佈了第一套無線人體區域網路的國際標準。在IEEE 802.15.6標準當中，制定了單躍星狀拓墣和雙躍延伸樹狀拓墣，在雙躍延伸的協定中，中繼節點(relaying node)的身分類似於微型的集線器(hub)，必須要處理新雙躍節點(relayed node)的加入與安排雙躍節點的傳輸，這會增加中繼節點耗能並縮短中繼節點的工作時間。 本篇論文基於IEEE 802.15.6標準提出新的兩躍傳輸模型，希望能夠節省能源並改善傳輸效率，我們利用無線人體區域網路中的節點特性達成這兩個目標。在無線人體區域網路應用上，因為節點通常安裝在人體上或甚至放入體內，因此節點體積往往受限，造成能源與計算能力匱乏，而集線器則是人體外用來負責控制一切傳輸之節點，較容易進行更換電池或充電，因此我們假設集線器具有比一般節點更多的資源與能源，本論文根據此假設，將所有兩躍控制所需執行的運算與控制，儘可能的交由資源較多的集線器去執行，藉此降低一般節點的能源消耗，並且透過適當的安排，讓各種存取方式能夠順利且有效率的套用到新的兩躍傳輸模型上。 效能分析及實驗評估的結果顯示新的兩躍傳輸模型能夠有效降低一般節點的能源消耗，將能源消耗集中到集線器上，在傳輸效能方面的表現，新協定能夠有效降低兩躍傳輸時的網路成本(overhead)，而且在新協定中，中繼節點不需具備額外複雜的功能即可幫忙轉傳資料給集線器，可以降低中繼節點的複雜度並降低能源消耗，延長中繼節點的工作時間。[[abstract]]Wireless body area networks (WBANs) are small range communication, and the number of nodes is typically 10-15, fewer than 256. The main challenge in WBANs is to balance the energy efficiency and quality of service. In some applications, battery powered nodes are impossible to replace batteries or recharge, and therefore to reduce energy consumption is an important requirement. There are many WBANs applications with data rate from 0.01bps to 10 Mbps. In order to satisfy each application requirement, WBANs need considering transmission efficiency. Energy efficiency and transmission throughput are important in WBANs. Based on the above observation, this thesis presents a novel two-hop extension model which utilizes the special usage of wireless body area networks to achieve power efficiency and high throughput. In WBANs applications, sometimes nodes wear or implant on human body restricting the volume, energy, and computing ability of nodes. Hubs are used to collect the data from sensors, it have sufficient energy, higher computing ability and can be recharged easily. Therefore the proposed model tries to move all of the complicated computing from relaying nodes to the hub, and reduce the energy consumption of nodes. This thesis modifies each kind of access methods, and let those methods workable on new two-hop extension model. Performance analysis and experimental evaluation shows that the proposed model can reduce energy consumption of each node and move the energy consumption to hub. The transmit performance is almost the same as IEEE 802.15.6 draft. The relaying nodes of the proposed model can help relaying data to hub without any other equipment, therefore the proposed two-hop extended model can lower the complexity of node and also can reduce the energy consumption.[[tableofcontents]]目 錄 誌 謝 I 中文摘要 II 英文摘要 IV 目 錄 VII 圖 目 錄 XI 表 目 錄 XV 第一章 緒論 1 1.1 前言 1 1.2 章節大綱 4 第二章 相關研究背景 5 2.1 背景介紹 5 2.2 採用分時多工之媒體存取控制協定 7 2.2.1 Marinkovic et al.’s method [13] 7 2.2.2 MedMAC [14] 7 2.3 採用排程競爭之媒體存取控制協定 8 2.3.1 Omeni et al.’s method [15] 8 2.3.2 Kwon et al.’s method [16] 11 2.3.3 BodyMAC [17] 13 2.3.4 IEEE 802.15.6 通訊標準 [12] 17 2.3.5 各方法與IEEE 802.15.6之差異 28 第三章 Two-Hop Direct Downlink (2HDD) 29 3.1 2HDD新協定概念 29 3.2 未連線節點透過中繼點加入網路之程序 31 3.3 兩躍節點存取模式運作 34 3.3.1 隨機存取 34 3.3.2 排程存取 42 3.3.3 臨時存取 43 3.3.4 未排程存取 45 3.4 工作模式與省電模式 46 第四章 效能評估 48 4.1 分析使用之變數說明 48 4.2 兩躍傳輸下能源消耗分析 50 4.2.1 能源消耗分析 50 4.2.2 理想工作狀態分析 55 4.2.3 非理想工作狀態分析 69 4.3 兩躍傳輸下傳輸負載分析 82 4.4 兩躍傳輸下吞吐量分析 85 4.5 模擬結果 87 4.5.1 模擬環境及模擬參數 87 4.5.2 節點加入程序 88 4.5.3 排程下載 90 4.5.4 兩躍傳輸下的負載模擬 92 4.5.5 兩躍傳輸下的吞吐量模擬 94 第五章 結論 96 第六章 未來工作 98 參考文獻 99 著作列表 103 圖 目 錄 圖2. 1 Omeni et al.’s method之拓墣示意圖 8 圖2. 2 三個工作程序的流程圖 10 圖2. 3 BodyMAC之訊框結構 13 圖2. 4 IEEE 802.15.6之拓墣示意圖 17 圖2. 5 Beacon之封包格式 21 圖2. 6 IEEE 802.15.6中由Beacon所定義之訊框結構 22 圖2. 7 集線器廣播連線詢問封包示意圖 22 圖2. 8 新節點建立連線示意圖 23 圖2. 9 資料與管理封包之兩躍傳輸示意圖 26 圖2. 10 兩躍傳輸之排程存取示意圖 27 圖3. 1 IEEE 802.15.6兩躍擴展傳輸示意圖 29 圖3. 2 新協定兩躍擴展傳輸示意圖 30 圖3. 3 未連線節點透過中繼點加入網路之示意圖 32 圖3. 4 兩躍傳輸之載波偵測多重存取/碰撞避免機制示意圖 35 圖3. 5 兩躍傳輸之時槽式Aloha機制示意圖 37 圖3. 6 中繼點傳輸延遲問題之示意圖 39 圖3. 7 解決中繼點傳輸延遲問題之示意圖 40 圖3. 8 兩躍傳輸之排程存取資料下載示意圖 42 圖3. 9 兩躍傳輸之臨時存取資料上傳示意圖 43 圖4. 1 IEEE 802.15.6訊框架構 50 圖4. 2 連線要求封包之封包內容 57 圖4. 3 連線指派封包之封包內容 57 圖4. 4 IEEE 802.15.6 通訊標準之節點加入程序示意圖 58 圖4. 5 2HDD之節點加入流程 60 圖4. 6 節點加入程序之能源消耗比較圖 63 圖4. 7 IEEE 802.15.6 通訊標準之排程下載示意圖 64 圖4. 8 2HDD之排程下載示意圖 66 圖4. 9 排程下載之能源消耗比較圖 68 圖4. 10 單躍資料傳送之機率分析 69 圖4. 11 雙躍資料傳送之機率分析 70 圖4. 12 節點加入程序之能源消耗比較圖( =0.005%) 75 圖4. 13 節點加入程序之能源消耗比較圖( =0.01%) 75 圖4. 14 節點加入程序之能源消耗比較圖( =0.02%) 76 圖4. 15 排程下載之能源消耗比較圖( =0.005%) 80 圖4. 16 排程下載之能源消耗比較圖( =0.01%) 80 圖4. 17 排程下載之能源消耗比較圖( =0.02%) 81 圖4. 18 排程下載之網路負載比較圖( =0%) 83 圖4. 19 排程下載之網路負載比較圖( =0.005%) 83 圖4. 20 排程下載之網路負載比較圖( =0.01%) 84 圖4. 21 排程下載之吞吐量比較圖( =0%) 85 圖4. 22 排程下載之吞吐量比較圖( =0.005%) 86 圖4. 23 排程下載之吞吐量比較圖( =0.01%) 86 圖4. 24 節點加入程序之能源消耗模擬圖( =0.005%) 88 圖4. 25 節點加入程序之能源消耗模擬圖( =0.01%) 89 圖4. 26 節點加入程序之能源消耗模擬圖( =0.02%) 89 圖4. 27 排程下載之能源消耗模擬圖( =0.005%) 90 圖4. 28 排程下載之能源消耗模擬圖( =0.01%) 91 圖4. 29 排程下載之能源消耗模擬圖( =0.02%) 91 圖4. 30 排程下載之網路負載模擬圖( =0%) 92 圖4. 31 排程下載之網路負載模擬圖( =0.005%) 93 圖4. 32 排程下載之網路負載模擬圖( =0.01%) 93 圖4. 33 排程下載之吞吐量模擬圖( =0%) 94 圖4. 34 排程下載之吞吐量模擬圖( =0.005%) 95 圖4. 35 排程下載之吞吐量模擬圖( =0.01%) 95 表 目 錄 表2. 1 生理感測器傳輸的資料型態及與協調者的距離統整表 12 表2. 2 競爭機制之相關參數 19 表2. 3 各媒體存取機制與IEEE802.15.6之比較 28 表4. 1 分析用變數一覽表 48 表4. 2 第6頻帶與第7頻帶的實體層參數 51 表4. 3 Nordic nRF24L01+ 傳輸模組耗能表 [23] 55 表4. 4 實驗模擬參數一覽表 87[[note]]學號: 896440061, 學年度: 10