Precise and accurate measurement of human limb movement finds applications in gait analysis in rehabilitation clinics and for athletic performance analysis. State of the art method for gait analysis consists of optical motion capture systems and force sensing platforms, which are complex, costly, require calibration procedures to work and are affected by variations in the lighting conditions. This paper presents a wireless sensor network with Ultrawideband(UWB) antennas to track the 3D trajectory of the foot for a long duration during treadmill walks. Our system uses only UWB sensors and avoids complications due to the fusion of information from multiple kinds of sensors. The system consists of one mobile node attached to a foot and four anchor nodes. Decawave DW1000 sensors with two way ranging are utilized for range estimation between nodes, and 3D foot trajectories are benchmarked with the motion capture system. Results show that the accuracy of tracking along the walking direction is high enough to extract spatial and temporal gait parameters. The main advantage of the system is that it can provide accurate tracking performance without complex calibration procedures. The system's small and light form factor, lower cost requirement compared to the motion capture system and convenience of use make the proposed system a good candidate for clinical gait analysis in unrestrained environments.

Energy is scarce in mobile computing devices including wearable and implantable devices in a wireless body area network. In this paper, an adaptive routing protocol is developed and analyzed which minimizes the energy cost per bit of information by using the channel information to choose the best strategy to route data. In this approach, the source node will switch between direct and relayed communication based on the quality of the link and will use the relay only if the channel quality is below a certain threshold. The mathematical model is then validated through simulations which shows that the adaptive routing strategy can improve energy efficiency significantly compared with existing methods.

Techniques that could be used to monitor human motion precisely are helpful in various applications such as rehabilitation, gait analysis, and athletic performance analysis. This paper focuses on the 3-D foot trajectory measurements based on a wearable wireless ultrasonic sensor network. The system consists of an ultrasonic transmitter (mobile) and several receivers (anchors) with fixed known positions. In order not to restrict the movement of subjects, a radio frequency (RF) module is used for wireless data transmission. The RF module also provides the synchronization clock between mobile and anchors. The proposed system measures the time-of-arrival (TOA) of the ultrasonic signal from mobile to anchors. Together with the knowledge of the anchor's position, the absolute distance that the signal travels can be computed. Then, the range information defines a circle centered at this anchor with radius equal to the measured distance, and the mobile resides within the intersections of several such circles. Based on the TOA-based tracking technique, the 3-D foot trajectories are validated against a camera-based motion capture system for ten healthy subjects walking on a treadmill at slow, normal, and fast speeds. The experimental results have shown that the ultrasonic system has sufficient accuracy of net root-mean-square error ( 4.2 cm) for 3-D displacement, especially for foot clearance with accuracy and standard deviation ( 0.62 ±7.48 mm) compared to the camera-based motion capture system. The small form factor and lightweight feature of the proposed system make it easy to use. Such a system is also much lower in cost compared to the camera-based tracking system.

In this paper, a new method for measuring and monitoring human body joint angles, which uses wearable ultrawideband (UWB) transceivers mounted on body segments, is proposed and investigated. The model is based on providing a high ranging accuracy (intersensor distance) between a pair of transceivers placed on the adjacent segments of the joint center of rotation. The measured distance is then used to compute the joint angles based on the law of cosines. The performance of the method was compared with a flexible goniometer by simultaneously measuring joint flexion-extension angles at different angular velocities, ranging between 8 and 90(°) /s. The measurement errors were evaluated by the average differences between two sets of data (ranging from 0.8(°) for slow movement to 2.8(°) for fast movement), by standard deviation (ranging from 1.2(°) to 4.2(°) for various movement speeds) and by the Pearson correlation coefficient (greater than 0.99) which demonstrates the very good performance of the UWB-based approach. The experimental results have shown that the system has sufficient accuracy for clinical applications, such as rehabilitation.

In wireless sensor networks, nodes can retransmit their neighbours' packets to provide redundancy and decrease packet error rate. However, this comes at the expense of increased energy consumption in the cooperating nodes. Cooperation between nodes in routing data is a necessity in sensor networks. This work exploits features of UWB-IR modulations to create redundancy in wireless sensor networks. We introduce a physical layer coding framework for UWB-IR and compare it with conventional UWB-IR modulation in terms of energy usage. Simulation results show that the proposed methods can decrease the energy usage of the nodes while enhancing packet error rate performance of the system.

An accurate approach in locating a source based on the intersections of hyperboloids defined by the time difference of arrival (TDOA) of a signal received at a number of reference nodes is proposed and investigated. The demonstrated system consists of a UWB transmitter, irradiating a UWB Gaussian pulse, and eight coherent receivers where positions are known. Techniques like optimal template-based estimator used for time delay estimation are discussed. The effect of errors in range measurement on the accuracy of positioning is reduced by adopting Taylor-series-based minimization procedures. Furthermore, we evaluate the performance of the proposed method by comparing with traditional LSE minimization procedure in both simulation and experimental results. The experimental results show that the target positioning error is only about (0.7198±0.271)cm (mean±standard deviation), which is accurate for potential applications such as robot navigation, personal tracking and monitoring.

Wireless body area network (WBAN) is an interesting application of sensor networks which can revolutionize our interaction with the outside world. WBAN like any other sensor network suffers limited energy resources and hence preserving the energy of the nodes is of great importance. Unlike typical sensor networks WBANs have few and dissimilar sensors. In addition, the body medium has its own propagation characteristic which means that the existing solution for preserving energy in wireless sensor networks might not be efficient in WBANs. The quality of the links between the nodes in WBAN is changing frequently due to the moving nature of the body. This can pose a major problem especially in the energy efficiency merit. In this work we have proposed an opportunistic scheme to exploit the body movements during the walking to increase the life time of the network. The results show that comparing to the existing methods this work can increase the life time of the network.

In this paper, we explore the application of cooperative communications in ultra-wideband (UWB) wireless body area networks (BANs), where a group of on-body devices may collaborate together to communicate with other groups of on-body equipment. Firstly, time-domain UWB channel measurements are presented to characterize the body-centric multipath channel and to facilitate the diversity analysis in a cooperative BAN (CoBAN). We focus on the system deployment scenario when the human subject is in the sitting posture. Important channel parameters such as the pathloss, power variation, power delay profile (PDP), and effective received power (ERP) crosscorrelation are investigated and statistically analyzed. Provided with the model preliminaries, a detailed analysis on the diversity level in a CoBAN is provided. Specifically, an intuitive measure is proposed to quantify the diversity gains in a single-hop cooperative network, which is defined as the number of independent multipaths that can be averaged over to detect symbols. As this measure provides the largest number of redundant copies of transmitted information through the body-centric channel, it can be used as a benchmark to access the performance bound of various diversity-based cooperative schemes in futuristic body sensor systems.

Linear block codes over Gaussian integers and Eisenstein integers were used for coding over two-dimensional signal space. A group of Gaussian integers with 2/sup 2n/ elements was constructed to code quadrature amplitude modulation (QAM) signals such that a differentially coherent method can be applied to demodulate the QAM signals. This paper shows that one subgroup of the multiplicative group of units in the algebraic integer ring of any quadratic number field with unique factorization, modulo the ideal (P/sup n/), can be used to obtain a QAM signal space of 2p/sup 2n-2/ points, where p is any given odd prime number. Furthermore, one subgroup of the multiplicative group of units in the quotient ring Z[/spl omega/]/(p/sup n/) can be used to obtain a QAM signal space of 6p/sup 2n-2/ points; one subgroup of the multiplicative group of units in the quotient ring Z[i](p/sup n/) can be used to obtain a QAM signal space of 4p/sup 2n-2/ points which is symmetrical over the quadrants of the complex plane and useful for differentially coherent detection of QAM signals; the multiplicative group of units in the quotient ring Z[/spl omega/]/(2/sup n/) can be used to obtain a QAM signal space of 3/spl middot/2/sup 2n-2/ points, where i=/spl radic/-1, /spl omega/=(-1+/spl radic/-3)/2=(-1+i/spl radic/3)/2, p is any given odd prime number, Z[i] and Z[/spl omega/] are, respectively, the Gaussian integer ring and the Eisenstein integer ring. These multiplicative groups can also be used to construct block codes over Gaussian integers or Eisenstein integers which are able to correct some error patterns.

This paper deals with the optimization of the design and radio network resource planning for cellular mobile communication systems. The key element to be considered for mobile network planning is cost. A hierarchical optimization planning method (HOP) is utilized since there are so many factors like system performance, terrain features, base station parameters, and cost factors which are involved in the large-scale system design. We present a three-level optimization approach for designing a cellular mobile system. It determines the cell number, cell site allocation, and the specific base station parameters in order to minimize the total system cost and to comply with the required system performance. The problem is formulated as a large combinatorial optimization model which can determine the optimal number of cells and select the best base stations' locations. The simulated annealing approach is developed to solve the hard combinatorial problem. Simulation results demonstrate the feasibility and effectiveness of the HOP approach for radio network planning.

For (n,q)=p/sup s/, where p=ch(F/sub q/), s/spl ges/1, V a q/sup m/-ary repeated-root cyclic code of length n with generator polynomial g(x), we give a partial answer about whether the q-ary image of V is cyclic or not with respect to a certain basis for F/sub q/m over F/sub q/.

With the trend towards higher performance in cellular networks, traffic control methods that assign available channel to cells dynamically provide more benefits than the conventional fixed assignment in generating better capacity and lesser forced termination. Previous studies of dynamic methods are based mainly on event driven simulation. A theoretical model for a cellular mobile communication system is presented in the paper. The comparison techniques are illustrated by examining a channel borrowing scheme. The characteristics obtained from the dynamic model and from event driven simulation are in agreement.>