Gengfa Fang

BodyMAC: Energy efficient TDMA-based MAC protocol for Wireless Body Area Networks

Wireless Body Area Networks (WBANs) enable placement of tiny biomedical sensors on or inside the human body to monitor vital body signs. The IEEE 802.15.6 task group is developing a standard to optimize WBAN performance by defining the physical layer (PHY) and media access control (MAC) layer specifications. In this paper an energy efficient MAC protocol (BodyMAC) is proposed. It uses flexible bandwidth allocation to improve node energy efficiency by reducing the possibility of packet collisions and by reducing radio transmission times, idle listening and control packets overhead. BodyMAC is based on a Downlink and Uplink scheme in which the Contention Free Part in the Uplink subframe is completely collision free. Three types of bandwidth allocation mechanisms allow for flexible and efficient data and control communications. An efficient Sleep Mode is introduced to reduce the idle listening duration, especially for low duty cycle nodes in the network. Simulation results show superior performance of BodyMAC compared to that of the IEEE 802.15.4 MAC.

Distributed Inter-Network Interference Coordination for Wireless Body Area Networks

In this paper we consider the inter-network interference problem in Wireless Body Area Networks (WBANs). We propose a distributed inter-network interference aware power control algorithm motivated by game theory. A power control game is formulated considering both interference between nearby networks and energy efficiency of WBANs. We derive a distributed power control algorithm called ProActive Power Update (PAPU), which can efficiently find the Nash Equilibrium representing the best tradeoff between energy and network utility. A realistic power control procedure is proposed assuming limited cooperation between WBANs. We compare our algorithm with the ADP algorithm where users are punished for interfering with others and we show that our solution can utilize energy much more efficiently by only sacrificing a small amount of network utility. In addition, we show that by adjusting the energy price, PAPU provides a methodology for application scenarios where WBANs have different energy constraints and quality of service requirements.

Inter-network interference mitigation in Wireless Body Area Networks using power control games

In this paper, we propose a non-cooperative power control game to mitigate inter-network interference in Wireless Body Area Networks (WBANs), which use emerging short-range wireless communication technology inside, on or around the human body for healthcare, entertainment and ubiquitous computing purposes. Interference endangers the reliability of WBANs especially in critical medical applications and also leads to more power consumption in very energy-constrained WBANs. Coordinating transmission power levels, we increase the system total throughput in the presence of interference using as little power as possible. We utilize non-linear and adaptive power pricing functions to penalize high power users and increase capacity in better channels. We investigate the Nash equilibrium existence and uniqueness and propose the best response strategy in the game to reach the Nash equilibrium.

Multiple ECG Fiducial Points-Based Random Binary Sequence Generation for Securing Wireless Body Area Networks

Generating random binary sequences (BSes) is a fundamental requirement in cryptography. A BS is a sequence of

Improved performance of spectrum cartography based on compressive sensing in cognitive radio networks

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Encryption for Implantable Medical Devices Using Modified One-Time Pads

bits, and each bit has a value of 0 or 1. For securing sensors within wireless body area networks (WBANs), electrocardiogram (ECG)-based BS generation methods have been widely investigated in which interpulse intervals (IPIs) from each heartbeat cycle are processed to produce BSes. Using these IPI-based methods to generate a 128-bit BS in real time normally takes around half a minute. In order to improve the time efficiency of such methods, this paper presents an ECG multiple fiducial-points based binary sequence generation (MFBSG) algorithm. The technique of discrete wavelet transforms is employed to detect arrival time of these fiducial points, such as P, Q, R, S, and T peaks. Time intervals between them, including RR, RQ, RS, RP, and RT intervals, are then calculated based on this arrival time, and are used as ECG features to generate random BSes with low latency. According to our analysis on real ECG data, these ECG feature values exhibit the property of randomness and, thus, can be utilized to generate random BSes. Compared with the schemes that solely rely on IPIs to generate BSes, this MFBSG algorithm uses five feature values from one heart beat cycle, and can be up to five times faster than the solely IPI-based methods. So, it achieves a design goal of low latency. According to our analysis, the complexity of the algorithm is comparable to that of fast Fourier transforms. These randomly generated ECG BSes can be used as security keys for encryption or authentication in a WBAN system.

Medical Body Area Networks: Opportunities, challenges and practices

Spectrum cartography is the process of constructing a map showing Radio Frequency signal strength over a finite geographical area. Multiple research groups have recently proposed to use spectrum cartography in the context of discovering spectrum holes in space that can be exploited locally in cognitive radio networks. In our novel approach, we exploit the sparsity of primary users in space to formulate the cartography process as a compressive sensing problem. Further, we present a novel algorithm for solving the cartography problem that builds on the well-known Orthogonal Matching Pursuit algorithm. We evaluate the performance of our approach by simulating a cognitive radio network where primary users are low power wireless microphones. Our simulation results show a significant improvement in reconstruction error, in comparison to two existing compressive sensing based methods.

A modified shuffled frog leaping algorithm for PAPR reduction in OFDM systems

We present an electrocardiogram (ECG)-based data encryption (EDE) scheme for implantable medical devices (IMDs). IMDs, including pacemakers and cardiac defibrillators, perform therapeutic or even life-saving functions and store sensitive data; therefore, it is important to prevent adversaries from having access to them. The EDE is designed with the ability to provide information-theoretically unbreakable encryption where two well-known techniques of classic one-time pads (OTPs) and error correcting codes are combined to achieve a cryptographic primitive for IMDs. Unlike other ECG-based key agreement schemes where ECG features are used to facilitate a key distribution, in the EDE scheme, random binary strings generated from ECG signals are directly used as keys for encryption. OTP keys are generated by the IMD and the programmer, respectively, before each encryption attempt; thus, the EDE does not require a cryptographic infrastructure to support a key distribution, storage, revocation, and refreshment. Protected by the EDE, IMDs could not be accessed by adversaries; however, medical personnel can have access to them by measuring real-time ECG data in emergencies. Therefore, the EDE design achieves a balance of high security and high accessibility for the IMD. Our data and security analysis shows that the EDE is a viable scheme for protecting IMDs.

MEB MAC: Improved channel access scheme for medical emergency traffic in WBAN

Medical Body Area Network (MBAN) is a new wireless communications technology designed to sense humans vital signals through tiny nodes in, on and around the human body wirelessly. MBAN will play an important role in enabling ubiquitous and non-invasive telemetry and healthcare systems in the future. In this paper, we firstly explore the opportunities of MBAN from the point of new applications, and then we analyze the enabling technologies and challenges to achieve the goal of MBAN, which includes energy efficiency, robustness, high data rate for video support and network co-existence issues. Finally, we describe our MQWIN400 radio platform which was designed to work at 400MHz MICS band, as well as the related research activities and experimental results.

Extension of SCTP for Concurrent Multi-Path Transfer with Parallel Subflows

Significant reduction of the peak-to-average power ratio (PAPR) is an implementation challenge in orthogonal frequency division multiplexing (OFDM) systems. One way to reduce PAPR is to apply a set of selected partial transmission sequence (PTS) to the transmit signals. However, PTS selection is a highly complex NP-hard problem and the computational complexity is very high when a large number of subcarriers are used in the OFDM system. In this paper, we propose a new heuristic PTS selection method, the modified chaos clonal shuffled frog leaping algorithm (MCCSFLA). MCCSFLA is inspired by natural clonal selection of a frog colony, it is based on the chaos theory. We also analyze MCCSFLA using the Markov chain theory and prove that the algorithm can converge to the global optimum. Simulation results show that the proposed algorithm achieves better PAPR reduction than using others genetic, quantum evolutionary and selective mapping algorithms. Furthermore, the proposed algorithm converges faster than the genetic and quantum evolutionary algorithms.