L. Alonso

A survey on M2M systems for mHealth: a wireless communications perspective.

In the new era of connectivity, marked by the explosive number of wireless electronic devices and the need for smart and pervasive applications, Machine-to-Machine (M2M) communications are an emerging technology that enables the seamless device interconnection without the need of human interaction. The use of M2M technology can bring to life a wide range of mHealth applications, with considerable benefits for both patients and healthcare providers. Many technological challenges have to be met, however, to ensure the widespread adoption of mHealth solutions in the future. In this context, we aim to provide a comprehensive survey on M2M systems for mHealth applications from a wireless communication perspective. An end-to-end holistic approach is adopted, focusing on different communication aspects of the M2M architecture. Hence, we first provide a systematic review of Wireless Body Area Networks (WBANs), which constitute the enabling technology at the patients side, and then discuss end-to-end solutions that involve the design and implementation of practical mHealth applications. We close the survey by identifying challenges and open research issues, thus paving the way for future research opportunities.

WSN4QoL: A WSN-Oriented Healthcare System Architecture:

People worldwide are getting older and this fact has pushed the need for designing new, more pervasive, and possibly cost effective healthcare systems. In this field, distributed and networked embedded systems, such as wireless sensor networks (WSNs), are the most appealing technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. This paper proposes recent advancements in this field by introducing WSN4QoL, a Marie Curie project which involves academic and industrial partners from three EU countries. The project aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. In particular, in this paper, the system architecture is presented to cope with the challenges imposed by the specific application scenario. This includes a network coding (NC) mechanism and a distributed localization solution that have been implemented on WSN testbeds to achieve efficiency in the communications and to enable indoor people tracking. Preliminary results in a real environment show good system performance that meet our expectations.

Towards Energy Saving Wireless Body Sensor Networks in Health Care Systems

The fact that the IEEE 802.15.4 MAC does not fully satisfy the strict wireless body sensor network (BSN) requirements in healthcare systems highlights the need for the design of new scalable MAC solutions, which guarantee low-power consumption to all specific sorts of body sensors and traffic loads. While taking the challenging healthcare requirements into account, this article aims at the study of energy consumption in BSN scenarios. For that purpose, the IEEE 802.15.4 MAC limitations are first examined and other potential MAC layer alternatives further explored. Our intent is to introduce energy-aware radio activation polices into a high-performance distributed queuing medium access control (DQ MAC) protocol and evaluate its energy-saving achievements, as a function of the network load. To do so, a fundamental energy-efficiency theoretical analysis for DQ MAC protocols is hereby for the first time provided. By means of computer simulations, its performance is validated using IEEE 802.15.4 MAC system parameters. The achieved outcome shows that the proposed DQ MAC scheme outperforms IEEE 802.15.4 MAC energy efficiency in all possible BSN scenarios.

A New MAC Approach in Wireless Body Sensor Networks for Health Care

Although the challenges faced by wireless body sensor networks (BSNs) in healthcare environments are in a certain way similar to those already existing in current wireless sensor networks (WSNs), there are intrinsic differences, which require special attention (Yang, 2006). For instance, human body monitoring may be achieved by attaching sensors to the body’s surface as well as implanting them into tissues for a more accurate clinical practice. One of the major concerns is thereby that of extremely energy efficiency, which is the key to extend the lifetime of battery-powered body sensors, reduce maintenance costs and avoid invasive procedures to replace battery in the case of implantable devices. That is, BSNs in healthcare systems operate under conflicting requirements. These are the maintenance of the desired reliability and message latency of data transmissions, while simultaneously maximizing battery lifetime of individual body sensors. In doing so, the characteristics of the entire system, including physical (PHY), MAC and application (APP) layers have to be considered. In fact, the MAC layer is the one responsible for coordinating channel accesses, by avoiding collisions and scheduling data transmissions, to maximize throughput efficiency (and reliability) at an acceptable packet delay and minimal energy consumption. Now, the design of future MAC protocols for BSNs must tackle stringent quality of service (QoS) requirements, apart from the desired low power consumption. Hence, the right MAC approach is able to handle cross-layer PHY-MAC-APP features. In order to consider all the aforementioned healthcare requirements, this chapter first concentrates on the analysis and evaluation of the energy consumption in a MAC level. Thereafter, novel cross-layer fuzzy-logic techniques are proposed to enhance QoS resource management in the here portrayed MAC approach for BSNs. Simulation results are achieved to validate the overall system performance, and its scalability, by increasing the number of wireless on-body sensors in the BSN (see Fig. 1). In this context, among all IEEE 802 standards available today, the IEEE 802.15.4 (802.15.4, 2003) is regarded as the technology of choice for most BSN research studies (Yang, 2006); (Zhen et al., 2007); (Kumar et al., 2008). However, the 802.15.4 MAC is not actually intended to support any set of applications with stringent QoS, and, even though it consumes very low power, the figures do not reach the levels required in BSNs (Zhen et al., 2007); (Kumar 6

Cross-Layer Enhancement for WLAN Systems based on a Distributed Queuing MAC protocol

Cross-Layer optimization is an emerging research topic. This paper proposes two novel cross-layer mechanisms to be included in a WLAN system where a near-optimum distributed MAC protocol is used. Their performance in terms of throughput and packet delay is analysed, and a significant system efficiency improvement is shown. This benefit is achieved by means of a PHY-MAC dialogue and a smart scheduling of the radio resources. Transmissions are scheduled taking into account the measurements of the channel state and the waiting time of packets in the accessing system. The two proposed mechanisms have different performance behaviour and thus present a trade-off between system enhancement and fairness. The obtained results emphasize the advantages of the proposed schemes and the importance of cross-layer design in wireless communication systems

Opportunistic scheduling for WLAN systems using cross-layer techniques and a distributed MAC

This paper proposes a novel Cross-Layer optimization nmechanism for WLAN systems and analyses its performance in nterms of throughput and mean packet delay. The proposed nscheme makes use of a MAC-PHY interaction and a nearoptimum ndistributed MAC to improve radio channel utilisation. nThe proposed technique allows the MAC layer to improve the nsystem efficiency by means of certain PHY information nknowledge. Simulation results show that the obtained benefits are nquite remarkable so the proposed scheme is feasible to be nintroduced in future wireless communication systems.

Dealing with VoIP Calls During “Busy Hour” in LTE

Long Term Evolution (LTE) is an evolving wireless standard developed by the 3rd Generation Partnership Project (3GPP) which, along with 3GPP HSPA+, 3GPP EDGE Evolution and Mobile WiMAX (IEEE 802.16e), opens the road to 4G technologies. The standard is focused on delivering high data rates for bandwidth-demanding applications and on improving flexibility and spectral efficiency, thus constituting an attractive solution for both end users and mobile operators. An important feature of LTE that differentiates it from conventional mobile standards is the all-IP packet based network architecture, which further ensures the seamless integration of internet applications and facilitates the convergence between fixed and mobile systems. The radio interface of LTE is based on Orthogonal Frequency Division Multiplexing (OFDM) and supports Multiple-Input-Multiple-Output (MIMO) technology. The standard defines asymmetrical data rates and modulations for uplink and downlink, using different access schemes for each link. In particular, Orthogonal Frequency Division Multiple Access (OFDMA) is employed in the downlink, while the technically similar but less powerdemanding Single Carrier – Frequency Division Multiple Access (SC-FDMA) is used in the uplink. In terms of the wireless spectrum allocation, LTE supports variable channel bandwidths that vary from 1.4 to 20 MHz and can be deployed in different frequency bands. The LTE architecture, referred to as Evolved Packet System (EPS) comprises the Evolved Radio Access Network (E-UTRAN) and the Evolved Packet Core (EPC), illustrated in Fig. 1 (3GPP, 2010). The E-UTRAN consists of a network of enhanced base stations called evolved Nodes B (eNBs) whose main role is to manage the radio resource and mobility in the cell in order to optimize the communication among all User Equipments (UEs). The eNBs can communicate with each other through the X2 interface and can access the EPC by means of the S1 interface. On the other hand, the EPC consists of a control plane node called the Mobility Management Entity (MME) and two user plane nodes, the Serving Gateway and the Packet Data Network Gateway (PDN Gateway or P-GW). These control planes handle the data packet routing within the LTE and towards non-3GPP data networks, respectively.

Hybrid Access Techniques for Densely Populated Wireless Local Area Networks

The IEEE 802.11p Task Group has recently released a new standard for wireless access in vehicular environments (WAVE). It constitutes an amendment to the 802.11 for Wireless Local Area Networks (WLANs) to meet the requirements of applications related to roadsafety involving interand intra-vehicle communications as well as communications from vehicle to the roadside infrastructure. Indeed, the importance of the targeted applications has forced authorities to allocate some dedicated bandwidth (nearby the 5.9GHz) to ensure the security of the communications. However, despite the suitability of this standard for use in high-speed vehicular communications, it is not possible to pass over the unprecedented market penetration of the popular 802.11 networks, the so-called WiFi networks. Before we can see a world where all the cars are equipped with 802.11p devices, current and nearfuture applications might probably run on the original 802.11. Moreover, interaction between humans and vehicles will probably be carried out by means of the 802.11, which is the standard that is flooding most of personal tech devices, such as laptops, mobile phones, gaming consoles, etc. Therefore, it is important to keep on working in the improvement of the 802.11 Standard for its use in, at least, some vehicular applications. This is the main motivation for this chapter, where we focus on the Medium Access Control (MAC) protocol of the 802.11 Standard, and we propose a simple mechanism to improve its performance in densely populated applications where it falls short to provide users with good service. Envisioned applications include those were a high number of vehicles and pedestrians coexist in a given area, such as for example, a crossing in a city where all the cars share information to coordinate the drive along the crossing and prevent accidents. Into more detail, the Distributed Coordination Function (DCF) is the mandatory access method defined in the widely spread IEEE 802.11 Standard for WLANs [1]. This access method is based on Carrier Sensing Multiple Access (CSMA), i.e., listen before transmit, in combination with a Binary Exponential Backoff (BEB) mechanism. An optional Collision Avoidance (CA) mechanism is also defined by which a handshake Request to Send (RTS) – Clear to Send (CTS) can be established between source and destination before the actual transmission of data. This CA mechanism aims at reducing the impact of the collisions of data packets and to combat the hidden terminal problem. The DCF can be executed in either ad hoc or infrastructure-based networks and is the only access method implemented in most commercial hardware. Despite the doubtless commercial success of the DCF, the simplicity