Wearable Antennas for Body-Centric Wireless Networks

对于个人和移动通信社区来说，人体通信是一个相对未开发的商品。到目前为止，移动电话技术已经允许用户随时随地通话。但在发达国家，这一市场正趋于饱和，为提供具有多媒体服务的第三代手机投入了大量资金。相机和小容量MP3播放器现在是标配。未来会怎样？大的愿景是人们为了健康、职业或娱乐的原因而穿戴大量的传感器、处理器、数据存储设备，所有这些都通过无线或特殊服装的电线连接起来。这些装置甚至可以在体内提供医疗解决方案，如自动药物计量和膀胱控制等。众所周知，带有蓝牙耳机的手机就是无线身体连接的一个例子。著名的白色iPod耳机或许就是有线系统需要被无线系统取代的一个例子。iPod的制造商苹果公司（Apple）和耐克公司（Nike）最近同意合作开发一种特殊设计的鞋子，这种鞋子可以让穿着者用iPod来监控时间、卡路里消耗和步伐，并在iPod和鞋子之间使用无线通信链路。这些例子显示了技术在大众市场上的发展方式。此外，一段时间以来，军队和特殊服务，如消防员，一直在使用身体系统来支持各种危险环境中的用户，使用无线来移除或减少线束是很重要的。实现这一宏伟愿景需要什么？制造商总是简单地将现有系统用于新的应用。在手机耳机上使用蓝牙就是一个例子。它是为另一种用途而开发的无线系统，即连接外围设备到计算机。但为了优化操作，即提高可靠性和减少电池消耗，需要更深入地了解身体上的无线电波传播通道以及如何设计天线。在之前的EPSRC资助下，伯明翰大学和伦敦玛丽女王大学开始了这项开创性的工作，以了解无线电频道并确定天线设计中的重要因素。通过对人体运动时信道和接收信号衰减方式的广泛测量，以及对潜在统计数据的确定，已经揭示了很多问题。然而，该研究项目只在蓝牙频率2.45GHz下工作，主要是窄带信道的特征，而不是实时视频通信所需的那种数据速率。拟议的研究是必要的，以推动位置，包括更多的优化天线的设计，为这个频率和其他频率。例如，最佳的辐射模式将使用统计方法来确定，适用于一系列身体类型和身体姿势，以及各种频率，包括比目前研究的高得多的频率。例如，40 ghz或60GHz的运行将提供非常高的数据速率，并且彼此靠近的实体网络之间的干扰也非常低，但会受到衰落问题的困扰。天线分集是一种众所周知的减少衰落的技术。它在人体上的使用将以不同的频率进行研究。FCC从3 GHz到10 GHz的频谱释放使超宽带系统成为可能，其高容量潜力，低功耗和良好的抗衰落特性使其成为未来车载系统的理想选择。然而，到目前为止，所有的天线都太大了，无法实际用于人体。研究小型可穿戴类型的设计。最后，为支持整个研究计划，将研究用于身体通信的天线对计算方法和改进技术提出的巨大挑战。

Communications on the human body is a relatively unexplored commodity for the personal and mobile communications community. Up to now mobile phone technologies have allowed the user to talk anytime anywhere. But in the developed world this market is becoming saturated and so much has been invested into providing third generation phones with multimedia services. Cameras and low capacity MP3 players are now standard. What does the future hold? The big vision is of people wearing a multitude of sensors, processors, data storage for health or occupational or entertainment reasons and all of these being connected either by wireless or by wires in special clothing. These units may even be inside the body to provide medical solutions such as automatic drug metering and bladder control etc. The well known mobile phone with Bluetooth headset is an example of a wireless on-body link. The famous white iPod headset is perhaps an example of a wired system that needs to be replaced by wireless. Apple, the makers of the iPod, and Nike have recently agreed to collaborate on specially designed footwear that would allow the wearer to use their iPod to monitor time, calories burned and pace, and which uses a wireless communication link, between the iPod and the shoe. These examples show the way that technology is moving in the mass market. In addition, for some time now both the military and the special services, such as firefighters, have been using on-body systems to support their users in various hazardous environments and the use of wireless to remove or reduce the wiring harness is important. What is needed to make the big vision happen? Manufacturers will always simply use existing systems for new applications. The use of Bluetooth for the mobile phone headset is an example of this. It is a wireless system developed for another use, namely connection of peripherals to computers. But to optimise the operation, that is to improve the reliability and reduce battery consumption, requires a deeper understanding of both the radiowave propagation channel on the body and how to design the antennas. In a previous EPSRC grant the University of Birmingham and Queen Mary University of London, began this pioneering work of understanding the radio channel and identifying the factors important in antenna design. Much has been uncovered via extensive measurements of the way in which the channel and hence the received signal fades when the body moves have been made and the underlying statistics determined. However the research programme has only been working at the Bluetooth frequency, 2.45GHz, and mainly been characterising narrowband channels, but not the kinds of data rates needed in communications of live video. The proposed research is necessary to move the position forward to include more work on the design of optimised antennas both for this frequency and for others. For example, the best radiation pattern will be determined using statistical methods for a range of body types and body postures, and various frequencies, including much higher ones than examined so far. For example, operation at 40 or 60GHz would give the possibility of very high data rates and also very low interference between body networks close to each other, but will suffer from fading problems. Antenna diversity is a well known technique for fading reduction. Its use on the body will be investigated at various frequencies. The release of the spectrum from 3 to 10 GHz by the FCC has made ultra wideband systems a real possibility and its high capacity potential, low power and good anti-fading properties make it ideal for future on-body systems. However all of the antennas so far made are too big for realistic on-body use. Design of small wearable types will be investigated. Finally antennas for on body communications throw up immense challenges for computational methods and improved techniques will be investigated to support the whole research programme.