1. Wearable computers and wearable wireless networks A wearable computer wearable computer is a new concept of mobile computing system. Its concept originated in the 1960s. Since the 1990s, with the rapid development of large-scale and very large-scale integrated circuits, research on wearable computers has entered a new stage. Currently, there is no exact definition of the concept of a wearable computer. In general, wearable computers should have the following basic characteristics: Can it be used in motion? Can you free yourself or do other things while using it? Can the user control? Sustainable? Diversity, that is, wearable computers with different applications should be different in composition, function, etc. From the above features, wearable computers are more closely integrated with people than traditional computers. This requires that the wearable computer must adopt a new human-machine interaction technology to achieve a harmonious human-machine. This is also a hot issue in the current research on wearable computers and the difficulty that must be overcome. Wearable Wireless Network In the wearable computer system described above, the hardware devices are mainly connected by a communication cable, and the operating platform used is also based on a wired device. Although this kind of system has its applicability in certain occasions, its shortcomings are obvious: First, it is not flexible enough. Because of the "hard" connection of communication cables, it is bound to affect the activity space and amplitude of the user's body, which is necessary in some applications, such as physical exercise. Second, it does not consider integration with existing personal communication terminals (such as mobile phones, PDAs, MP3s, etc.). This would make existing communication terminals a separate and functionally overlapping device from the wearable computer entity. In response to this situation, this paper proposes the concept of a wearable wireless network. Compared to wearable computers, wearable wireless networks have the following characteristics: (1) Better flexibility. (2) Fully consider the integration with existing personal communication terminals. (3) It is possible to perform distributed control. This is because each communication terminal has certain computing processing power and storage capacity (and with the development of very large scale integrated circuits, the performance in this aspect is bound to be further improved). (4) More humane. The user can select the appropriate primary communication device to control the entire network according to different applications, convenience levels, and personal preferences. It can be seen that the wearable wireless network should have better applicability and wider application prospect than the wearable computer, and it can be developed on the basis of various existing wireless local area network technologies. Since the existing wireless LAN technologies are relatively mature, they have obvious advantages in development difficulty and development cycle compared to wearable computers. 2. System model of wearable wireless network 2.1 Network Model Currently, technologies suitable for building wearable wireless networks include Bluetooth and ZigBee. Both wireless technologies belong to the IEEE 802.15 family and operate in the ISM band. The differences between them are shown in Table 1-1 below. Because they are completely consistent in networking, the wearable network models built with them are basically the same. Table 1-1 Comparison between Bluetooth and ZigBee (1) Wearable wireless network structure built with Bluetooth and ZigBee technology The networking methods of Bluetooth and ZigBee can be divided into three forms: star network, peer-to-peer network and hybrid network [2]. Wearable wireless networks built with Bluetooth and ZigBee technology should be in a hybrid form, as shown in Figure 2.1. It is a loose Ad Hoc network that fits the needs of wear. Figure 2.1 Wearable Bluetooth Network Model The entire network in the above figure is divided into two levels of hierarchy. The master device of the Class I Peak Network is connected to the master devices of each Class II Peak Network, and the master devices of each Class II Peak Network act as slave devices in the Class I Peak Network. Each level of the piconet is maintained and managed by the main equipment. In order to facilitate maintenance and management of the entire network, the primary device of the Level I Peak Network acts as a LAP to the external network, and the primary device does not act as the primary (slave) device of the Level II Peak Network. Of course, the LAP here is not directly connected to the wired network. There may be more than one device that can act as a LAP role, but regardless of which device acts as a gateway device, the above networking principles should be followed. (2) Wearable wireless network equipment In the above two types of wearable wireless networks, devices in the entire network can be classified into two basic types according to different roles: Sensors or other terminal equipment: This type of equipment only needs to transfer the collected data to the Master, and does not undertake any task of managing and maintaining the network. This type of equipment mainly includes sensors, detectors, headsets and cameras. Network interconnection equipment: Network interconnection equipment is not only responsible for forwarding data transmitted from terminal equipment, but also must manage and maintain each level II network. At the same time, a new network must be formed between these interconnected devices. Therefore, network interconnection equipment should have a certain storage capacity and data processing capabilities. In theory, each Master can act as a LAP, but in reality there is no such need. In this model, the LAP acting as a gateway acts only as a member of the Level I network and is responsible for managing and maintaining the Level I network, not as a base station for Level II networks. The purpose of this is to prevent the same device from playing too many roles, which will increase the complexity of the device. Devices that can act as network interconnection devices include PDAs, GPS, headsets, MP3s, mobile phones, and PTT (Push To Talk), among which mobile phones and the like can also act as gateways for contacting external networks. 2.2 Service Principle Regardless of the wireless technology used to build a wearable wireless network, basic service and management capabilities should be provided, including internal data transfer, web-based services, and network management services. (1) Internal data transmission Internal data transfer is the most basic service requirement for wearable wireless networks. Within the network, the Level I network and the Level II network can adopt different data transmission modes. In the Level II network, the point-to-point transmission mode is usually adopted between the terminal device such as a sensor and the Master. This is because the terminal in the Level II network usually only needs to transmit data in a single item, and generally not between the communication terminals. There are a large number of communication services that need to establish a direct route to complete. In the I-level network, the Master can use both point-to-point transmission and point-to-multipoint transmission. However, if point-to-point communication between slaves is required, the original Peak network must be separated from the original Peak network. Obviously, if data transmission is required between terminal devices in the same Level II network, it must be forwarded by the Master. If a terminal device in a Level II network wants to send data to a terminal device in another Level II network, it must be forwarded through the LAP in the Level I network. When a device in a Level I network needs to transmit data to an external network, it may be considered to forward through a LAP as a gateway or establish a virtual connection. (2) Web access Typically, only devices in a Level I network have the requirements and conditions for Web access. Web access should be done through the gateway, mainly considering the security of the network. After establishing a connection to a Web site, you can consider using the C/S model to provide services. These services should include FTP services, E-mail services, and audio and video services. For voice services, VoIP technology can be considered. (3) Network management services The task of network management is to maintain reliable operation of the entire network. In order to establish communication connections between devices and maintain the management network, it is common to assign logical addresses to devices in the network. Before IPv6 is not enabled, it is difficult to make the actual IP address the logical address of each communication device. However, the device acting as a gateway should have an actual IP address, which is good for web access. Of course, if necessary, you can also consider the gateway device as a DHCP server, but this will obviously increase the workload of the gateway device. In fact, each wireless technology's own address addressing and allocation scheme can also be utilized. To detect the activity status of devices inside the network, broadcast messages can be sent to the entire network or to a specific Level II network. The entire network is diagnosed based on the feedback, so that the user can be alerted in time. Of course, broadcast messages containing specific network device addresses can also be published, which typically occurs when the message publisher needs to establish contact with the device.
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