中文 3480 字 英文資料翻譯 ZigBee/IEEE 802.15.4 Networking Examples ZigBee networking has a diverse range of applications, including but not limited to home automation, inventory tracking, and healthcare. This chapter reviews a number of the application scenarios in which ZigBee devices can increase efficiency and/or reduce cost. Full ZigBee protocol implementation has the advantage of reliable mesh networking capability. However, if the application is simple, it might be possible to implement only IEEE 802.15.4 layers. 2.1 Home Automation Home automation is one of the major application areas for ZigBee wireless networking. In this section, a number of these use cases are reviewed. The typical data rate in home automation is only 10Kbps. Figure 2.1 shows some of the possible ZigBee applications in a typical residential building. Most of the applications shown in Figure 2.1 are briefly reviewed in this chapter. 2.1.1 Security Systems A security system can consist of several sensors, including motion detectors, glass-break sensors, and security cameras. These devices need to communicate with the central security panel through either wire or a wireless network. ZigBee-based security systems simplify installing and upgrading security systems. Despite ZigBees low data rate, it is still possible to transfer images wirelessly with acceptable quality. For example, ZigBee has been used in a wireless camera system that records videos of visitors at a homes front door and transmits them to a dedicated monitor inside the house. 2.1.2 Meter-Reading Systems Utility meters need to be read on a regular basis to generate utility bills. One way to do so is to read the meters manually at homeowners premises and enter the values into a database. A ZigBee-based automatic meter-reading (AMR) system can create self-forming wireless mesh networks across residential complexes that link meters with utilities corporate offices. AMR provides the opportunity to remotely monitor a residences electric, gas, and water usage and eliminate the need for a human visiting each residential unit on a monthly basis. An AMR can do more than simply deliver the total monthly usage data; it can gather detailed usage information, automatically detect leaks and equipment problems, and help in tamper detection. ZigBee-based wireless devices not only perform monitoring tasks, they can manage the usage peak by communicating with the appliances inside the house. For example, when there is a surge in electricity usage, a ZigBee-enabled electric water heater can be turned off for a short period of time to reduce the peak power consumption. 2.1.3 Irrigation Systems A sensor-based irrigation system can result in efficient water management. Sensors across the landscaping field can communicate to the irrigation panel the soil moisture level at different depths. The controller determines the watering time based on moisture level, plant type, time of day, and the season. A distributed wireless sensor network eliminates the difficulty of wiring sensor stations across the field and reduces the maintenance cost. 2.1.4 Light Control Systems Light control is one of the classic examples of using ZigBee in a house or commercial building. In traditional light installation, to turn on or off the light it is necessary to bring the wire from the light to a switch. Installation of a new recess light, for example, requires new wiring to a switch. If the recess light and the switch are equipped with ZigBee devices, no wired connection between the light and the switch is necessary. In this way, any switch in the house can be assigned to turn on and off a specific light. Figure 2.2 is an example of wireless connections between wall switches and lights. In our example, the lights are located in a residential building entrance, living area, and hallway. The wall switch in the entrance can turn on and off any of the four lights. The living area wall switch, in contrast, communicates only with the lights in the living area. Living area lights are in close proximity to each other, and therefore a single ZigBee device can be used for both lights. The concept of using binding tables (see Section 1.12) is applicable in the example of Figure 2.2. Wall switch 1 is logically connected to all four lights. Wall switch 2 is bound only to the lights in the living area. One of the devices in the network has the task of storing and updating the binding table. A ZigBee-enabled recess light can be more expensive than a regular recess light, but the installation cost of a ZigBee-enabled light is lower because it requires no additional wiring to a wall switch. Using wireless remotes to control the lights is not a new concept. ZigBee provides the opportunity to implement this concept on a large scale by ensuring long battery life and interoperability of products from various vendors in a reliable and low-cost network. In addition to potential cost savings, ZigBee-enabled lights can have other benefits in a house. For example, the ZigBee devices embedded in the recess lights can act as routers to relay a message across the house, or the lights can be programmed to dim whenever the television set is turned on. The ZigBee light control mechanism has been used for street light controls as well. 2.1.5 Multizone HVAC Systems The multizone control system allows a single heating, ventilation, and air-conditioning (HVAC) unit to have separate temperature zones in the house. Zoning the HVAC system can help save energy by controlling the flow of air to each room and avoiding cooling or heating unnecessary areas. Figure 2.3 is a simplified diagram that shows motors controlling air dampers and regulating the flow of air to different zones. ZigBee devices control these motors based on the commands they receive from the main HVAC zone control panel and temperature sensors. An alternative way of implementing a multizone control system is to connect the zone control panel, motors, and temperature sensors via wires instead of a wireless network. A wired system has less flexibility and additional labor cost for wiring, but the cost of the parts might be slightly lower. Total system cost and flexibility for future modifications should be the decision factors in selecting between these two implementation methods. 2.2 Consumer Electronics: Remote Control In consumer electronics, ZigBee can be used in wireless remote controls, game controllers, a wireless mouse for a personal computer, and many other applications. In this section, we briefly review the application of ZigBee in wireless remotes. An infrared (IR) remote controller communicates with televisions, DVDs, and other entertainment devices via infrared signals. The limitation of IR remotes is that they provide only one-way communication from the remote to the entertainment device. Also, IR signals do not penetrate walls and other objects and therefore require line of sight to operate properly. Radio frequency (RF) signals, however, easily penetrate walls and most objects. IEEE 802.15.4 is a proper replacement for IR technology in remote controls because of the low cost and long battery life of ZigBee-based wireless communication. IEEE 802.15.4 can be used to create two-way communications between the remote control and the entertainment device. For example, song information or on-screen programming options can be downloaded in to the remote itself, even when the remote control is not in the same room as the entertainment device. 2.3 Industrial Automation At the industrial level, ZigBee mesh networking can help in areas such as energy management, light control, process control, and asset management. In this section, application of ZigBee in asset management and personnel tracking is briefly reviewed. Asset Management and Personnel Tracking Passive radio frequency identification (RFID) tags have been in use for several years. Although a passive RFID tag does not have any battery, the RFID reader unit can be a battery-powered instrument. A passive RFID tag can transmit only simple information such as an ID number, which is sufficient for many asset management applications. Active RFIDs, such as ZigBee devices, are battery powered and generally are more expensive than passive RFIDs. ZigBee-based active RFIDs have longer range than passive RFIDs and can provide additional services such as estimating the location of assets or personnel. Chapter 7 covers the details of ZigBee-based location methods. The basic concept of location estimation is shown in Figure 2.4, where location of personnel is tracked inside a typical office building with offices and cubes. There are three fixed ZigBee nodes with known locations. The mobile ZigBee node, carried by an employee, broadcasts a signal that is received by all three fixed nodes. The signal becomes weaker as it travels longer; therefore, the amplitude of the signal received by each of the fixed nodes can be different. There are several algorithms that can take the received signal strength at the three fixed nodes and calculate the approximate location of the mobile node. The signal transmitted from the mobile node is reflected from walls and other objects in the room before it reaches the fixed nodes, which results in reduced accuracy of the location estimation. Chapter 7 reviews some of the methods developed to improve the location estimation accuracy. 2.3.2 Livestock Tracking Livestock are vulnerable to disease, and it is important to track and identify a diseased animal quickly. Rapid disease response reduces the number of producers impacted by a disease outbreak or other animal health events 6 . Passive RFID tags have been used as an inexpensive solution for livestock tracking and can be sufficient for some applications. Passive RFID tags have limited range and can only provide previously stored information such as an identification number. IEEE 802.15.4-based active tags can cost more than passive ones, but the IEEE 802.15.4 tags have extended range and can provide additional information such as animal heartbeat and the animals approximate location. 2.4 Healthcare One of the applications of IEEE 802.15.4 in the healthcare industry is monitoring a patients vital information remotely. Consider a patient who is staying at his home but for whom it is important that his physician monitor his heart rate and blood pressure continuously. In this system, an IEEE 802.15.4 network can be used to collect data from various sensors connected to the patient. The 802.15.4 standard uses 128-bit Advanced Encryption Standard (AES) technology to securely transfer data between ZigBee devices and other networks. Figure 2.5 is a simplified diagram of a remote monitoring system. A patient wears a ZigBee device that interfaces with a sensor, such as a blood pressure sensor, that gathers the information on a periodic basis. Then this information is transmitted to a ZigBee gateway. A ZigBee gateway provides the interface between a ZigBee network and other networks, such as an Internet Protocol (IP) network. The patient information is then transmitted over the Internet to a personal computer that the physician or nurse uses to monitor the patient. This system could help hospitals improve patient care and relieve hospital overcrowding by enabling them to monitor patients at home. 2.5 Other Applications 2.5.1 Hotel Guest Room Access ZigBee-based systems can replace the magnetic key card systems used in hotels to access guest rooms. The traditional room access plastic cards have a magnetic strip on their back; the card reader installed on the guest door reads the information encoded into the magnetic strip to allow or deny access to the room. Installing this reader for each door requires wiring through the door. Alternatively, a ZigBee- based room access system includes a portable ZigBee device that acts as the key and a battery-powered ZigBee device inside the door that locks and unlocks it. Unlike the traditional method, the ZigBee-based room access system does not require wiring each door, which reduces the installation cost. 2.5.2 Fire Extinguishers Fire extinguishers should be checked every 30 days to make sure all the canisters are charged and pressures are correct. Instead of checking the extinguishers manually, in a ZigBee-based monitoring system a sensor is attached to each extinguisher to monitor its status and wirelessly communicate with the coordinator when maintenance is needed. A ZigBee-based monitoring system not only saves time and labor cost, it also helps improve fire safety by immediately alerting authorities if a fire extinguisher is not working properly. ZigBee/IEEE 802.15.4 網絡應用實例 ZigBee 非常廣泛的應用，包括智能家居、庫存跟蹤和醫療保健，但又不僅限于此。 本章 回顧了 許多可以 運用 ZigBee設備提高效率和降低成本 的應用實例 。完整的 ZigBee 協議 具備 可靠的 網狀 網絡 性能的優點 。然而 ， 如果應用 很簡單 ，也 可能 僅使用 IEEE 802.15.4層。 1.1 智能家居 智能家居 是 ZigBee 無線網絡 的 一個主要應用領域 。 在本節中 ， 回顧 了 大量這樣的 用例 。 在 智能家居 中 典型的數據率只有 10 Kbps。 圖 1.1展示 了在一個典型的住宅建筑 中的 一些 可行 的 ZigBee 應用 。 在 本 章 中對 圖 1.1 中 展 示 的 大多數應用 作了簡要 介紹 。 1.1.1 安全系統 一個安全系統可以由多個傳感器 組成 ， 包括運動探測器、玻璃破碎傳感器和安全 攝像頭。這些設備需要通過 有 線或無線網絡與 中央 安全 面板通訊 。 基于ZigBee的 安全系統 簡化了安全系統的 安裝和 更新過程 。盡管 ZigBee的數據率 很低 ，但 它 仍然 可以 無線傳輸 質量 可接受的 圖像。例如 ， ZigBee 已被應用于 一個錄制門外訪客 視頻傳送到 住宅 里 一個專用 監控 器的 無線攝像系統 。 圖 1.1 可能 啟用 ZigBee 設備 的 典型居住建筑 1.1.2 抄表系統 電表需要定期 讀取數據 生成水電費 賬單 。 一種 方法是手動 讀 取 房主 房屋前 的電表數值，然后 輸入到一個數據庫。 一個基于 ZigBee的 自動抄表 系統 （ AMR）可以 自發 創建 一個連接 住宅區 電表 與 電表 公司辦公室的無線網狀網絡。 AMR 通過 遠程監控住宅的電力、煤氣和水的使用 的機會，并且淘汰了人力每月挨家挨戶去查電表的方式。 AMR 的 作用 不僅僅是 傳輸每月水電 使用量數據 ； 它 還 可以收集 詳細的使用信息 ， 自動檢測泄漏和設備問題 ，協助入侵檢測 。基于 ZigBee 的 無線設備不僅執行監控 任務 ， 他們 還 可以 通過和室內的裝置通信來管理使用高峰期 。例如 ， 當用電量激增 時， 可以關閉 ZigBee電 熱水器一段時間來 降低 高峰期用電量 。 1.1.3 灌溉系統 一個 基于 傳感器 的 灌溉系統能 使 水資源管理 更有效率 。 田野里的傳感器能夠把不同深度土壤的濕潤程度傳給灌溉面板。控制器根據土壤的濕度，植物種類，一天中的時間和季節等情況來確定灌溉時間。 分布式無線傳感器網絡消除了 在田野中建立有線傳感器基站的困難， 降低 了 維修成本。 1.1.4 燈控系統 燈 光控制是 在室內或商業建筑中使用 ZigBee 的一個典型例子。 在傳統的照明裝置 中，必須從電燈到開關扯一根電線 來開啟或關閉 電 燈。 例如，安裝一個新壁燈的時候，需要一條新的到開關的電線。如果壁燈和開關都配備了 ZigBee 設備的話，那么電燈和開關之間將不再需要電線連接。這樣，室內的任何開關都可以被指派來打開和關閉一盞特定的電燈。 圖 1.2 是一個墻上開關和電燈間無線連接的例子 。在我們的示例中 , 電燈位于居民建筑的入口處，居住區和走廊。 在入口處的墻壁開關可以打開或關閉任何四個燈。相反 , 居住區墻上的開關僅與位于居住區的電燈進行通信 。 居住區的電燈彼此挨得很近，因此一個 ZigBee設備就能夠控制這兩個燈。 使用綁定表的概念也適應于圖 1.2的例子。墻上開關 1邏輯上與所有的 4盞燈相連，開關 2只與居住區的電燈綁定，網絡的其中一個設備負 責存儲和更新綁定表。 一個 支持 ZigBee 的壁燈要比常規的壁燈更貴，但是它的安裝費用卻較低，因為它不需要額外的電線連接到墻上的開關。使用無線來遙控電燈已經不是一個新的概念，通過確保較長的電池壽命和來自不同經銷商的產品的互操作性，ZigBee提供了在可靠的，低成本的網絡中大范圍實現這個概念的機會。 除了潛在的成本節省外，在室內， ZigBee 電燈還有其他的好處。例如，嵌入到壁燈內的 ZigBee 設備可以充當路由器，在房間內轉發信息，或者，壁燈可以被編程設計為當電視打開時變暗。 ZigBee 燈控機制同樣也已經被用于路 燈控制。 圖 1.2 住宅建筑 中的 ZigBee 無線網絡光控 系統 1.1.5 多層 供暖 系統 在多層的控制系統允許 單個的供暖，通風和空調單元在室內有各自的溫度區域 。 HVAC分區系統通過控制每個房間的空氣流動可以幫助節省能源，避免對不必要的區域進行冷卻或加熱。圖 1.3是一個簡化的圖表，它顯示了發動機控制空氣濕度和管理不同房間的空氣流動。 ZigBee 設備根據它們從主 HVAC 區域控制面板和溫度傳感器接收到的命令來控制這些發動機。另一種使用多區域控制系統的方法是通過有線而非無線網絡的方式來連接區域控制面板，發動機和溫度傳感器。無線系統有較低的復雜度和額外的布線成本，但是這部分的成本可能會稍微低一些。總共的系統花費和將來的更新復雜度是在這兩種應用方法間進行選擇的決定因素。 . 圖 1.3 采用 ZigBee 空氣阻尼器 的 多層空調 1.2 消費電子 ： 遠程控制 在消費電子中， ZigBee 可以被用在遠程無線控制，游戲控制器，個人電腦的無線鼠標和許多其他應用中 。在這部分中，我們簡單的介紹了 ZigBee 在遠程無線控制中的應用。 紅外（ IR）遠程控制器通過紅外信號與電視， DVD 和其他娛樂設備進行通信，紅外遙控的限制就是它們只提供從遙控端到娛樂設備的單方向通信。此外，紅外信號不能穿透墻壁和其他物體，因此需要對紅外線進行適當操作。然而，射頻信號可以很輕易的穿透大部分物體。 在遠程控制方面， IEEE 802.15.4是對 IR 技術的一個合適的替代，因為基于ZigBee的無線通信具有低成本和較長的電池壽命的優點。 IEEE 802.15.4能夠在遠程控制和娛樂設備間建立雙向的通 信。例如，歌曲信息和在屏幕編程選項能夠被下載到遙控器本身，即使被遠程控制的娛樂設備與遙控器不是在同一個房間。 1.3 工業自動化 在工業級水平上， ZigBee 網狀網絡可以用于能源管理，照明控制，過程