Wearable Antennas for Body-Centric Wireless Networks

对个人和移动通信界来说，人体通信是一种相对未被开发的商品。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，在为第三代手机提供多媒体服务方面投入了大量资金。摄像头和低容量MP3播放器现在是标准配置。未来会是什么样子？宏伟的愿景是，人们出于健康、职业或娱乐原因佩戴大量传感器、处理器和数据存储，所有这些都可以通过无线或特殊服装中的有线连接起来。这些单元甚至可能在人体内提供医疗解决方案，如自动药物计量和膀胱控制等。众所周知的带有蓝牙耳机的移动电话是无线身体链接的一个例子。著名的白色iPod耳机可能就是有线系统需要被无线系统取代的一个例子。IPod的制造商苹果和耐克最近同意合作开发特别设计的鞋子，允许穿着者使用他们的iPod来监控时间、卡路里燃烧和速度，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中的发展方式。此外，一段时间以来，军方和特殊服务部门(如消防员)一直在使用车载系统在各种危险环境中为用户提供支持，使用无线技术移除或减少线束非常重要。需要什么才能实现这一宏伟愿景？制造商总是简单地将现有系统用于新的应用。手机耳机使用蓝牙就是一个例子。它是为另一种用途开发的无线系统，即将外围设备连接到计算机。但要优化操作，即提高可靠性和降低电池消耗，需要对人体上的无线电波传播信道和如何设计天线有更深入的了解。在之前的EPSRC拨款中，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，了解无线电频道并确定天线设计中的重要因素。通过对物体运动时通道以及接收到的信号衰落方式的广泛测量，已经发现了很多东西，并确定了基本的统计数据。然而，该研究计划只在2.45 GHz的蓝牙频率下工作，主要是描述窄带通道的特征，而不是现场视频通信所需的那种数据速率。拟议的研究是必要的，以便将这一地位向前推进，以便包括为该频率和其他频率设计优化天线的更多工作。例如，最佳辐射模式将使用统计方法来确定一系列身体类型和身体姿势，以及各种频率，包括比目前检查的要高得多的频率。例如，在40或60 GHz下运行可能会产生非常高的数据速率，而彼此靠近的实体网络之间的干扰也会非常低，但会受到衰落问题的影响。天线分集是一种众所周知的减少衰落的技术。它在身体上的使用将以不同的频率进行调查。FCC从3 GHz到10 GHz的频谱释放使超宽带系统成为现实，其高容量潜力、低功耗和良好的抗衰落性能使其成为未来车载系统的理想选择。然而，到目前为止制造的所有天线都太大了，无法现实地在身体上使用。我们将研究小型可穿戴设备的设计。最后，用于身体通信的天线对计算方法提出了巨大的挑战，并将研究改进的技术以支持整个研究计划。

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.