## 1 Introduction  
Wearable technologies are electronic devices located in everyday clothing and accessories. Nowadays, there is an increasing demand to monitor performance of various activities in sports [1], daily routines [2] and health care scenarios [3]. The goals include measurement of biological and physical parameters with subsequent processing for different applications. These wearable devices are required to be small to avoid user discomfort. They may be integrated in a belt [4], necklace [5], shirt [6] or shoes [7]. Normally the sensor position depends on the biological and physical parameters to be measured. Sensors are placed in footwear to measure various biological parameters, including plantar pressure [8], speed [9], walking and running gait [10]. These data are useful to monitor everyday activity, to detect gait abnormality [9] and to detect the onset of various medical conditions [11].  
These sensors need to be simple and consume low power. Combining information from different on-body deployed sensors requires a smarter and more complex node. This hub is responsible for collecting all the information to be processed, simplifying it and ultimately displaying it to the final user. The position and the technology used in the communication link between the different nodes and the main hub is important for overall system reliability. The main hub is typically located at the waist area of the body [12, 13] which is equidistant to other on-body nodes thereby reducing the maximum communication distance over the whole body. It has been demonstrated that using directional antennas on footwear achieves equal or better performances than a waist-centric paradigm with omnidirectional antennas [14]. However, the expansion of advanced handheld devices such as smartphones and smartwatch is shifting the hub-centric scenario from waist to the hand area. This on-body area is critical because of the rapid changes of the body posture responsible for shadowing and multipath fading behavior. The communication link must be reliable during everyday activities, including walking.  
Different technologies are already used in the communication layer in the 2.45 GHz frequency band such as Bluetooth [15] and WiFi [16]. These technologies are well known and widely used in many systems. However, new emerging technologies have greater data rates and are more secure. Within this framework, UWB technologies are characterized by wider bandwidths, lower power consumption and smaller range in comparison to the narrowband systems. Because of these advantages, UWB is a promising technology for the development of Body Area Networks [17]. The antenna design must take the operational environment into consideration [18]. On-body scenarios are characterized by close proximity to high water-content and low water-content materials which can influence the antenna performance. Besides it is important to include body movement because of fading and shadowing.  
In this paper a communication link between the footwear and the wrist is studied for three different frequency ranges for a subject while walking. The footwear can be a hub location or can relay footwear sensor information to a handheld device.  
Performances for footwear located antennas should consider the rapid and repetitive movement of the foot for a walking/running subject and the close proximity to the ground. The performance of a monopole antenna on the toe cap is not impaired by the ground proximity because the foot behaves as a screen, decreasing the back lobe radiation.  
An antenna is designed to cover the 2.4 GHz and UWB bands and can be integrated with multimode transceivers to mitigate on-body multipath effects and to adjust the data rate to the particular request.  
In the first section of the paper the antenna performances are shown in the free space and in close proximity to the body. In the second section the three frequency ranges are compared for a subject walking using S\({}_{21}\) measurements.