A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> Diversity techniques based on NC: <s> Modern medical wireless systems present a challenge where communication reliability is crucial, but the resources are limited, since medical devices carried on a patient need to be small. We propose, simulate and analyze one relay network, and show that network coding along with redundancy can be used as a very efficient error recovery mechanism that greatly improves network reliability at very low computational and hardware cost. Thus, network coding can be an interesting method for reliability improvement in medical systems such as Wireless Body Area Networks (WBAN). A network coding scheme is proposed and simulated, and the optimal method according to that scheme is analyzed. Practical and fast decoding algorithm is presented. We then simulate the proposed network and the optimal method and compare it with the regular redundant network. Simulations show great improvement compared to regular redundant transfer, for very small computational cost. Finally, we simulate and show that the proposed network is still functional and operational even in case where one relay point is off. <s> BIB001 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> Diversity techniques based on NC: <s> During recent years Wireless Body Area Networks (WBANs) have been experienced continuous developments by researchers both in academia as well as industry due to its capabilities and various promising applications, for instance, in the areas of healthcare, sports, military, etc. One of the crucial requirements in designing a WBAN, especially, for the healthcare applications is network reliability since it is related to life in patients. However, due to the close proximity of the network to the human body, electromagnetic waves affect the human body should be extremely low. Thus, a WBAN requires a low transmission power meaning that a sensor node does not transmit its data directly to a monitoring device or a gateway but the data are forwarded by a relay node. In this study, we apply the assistance of a relay combining with network coding design to improve network reliability of a WBAN at very low computational and hardware cost. An Unequally Error Protection (UEP) concept is cooperated with network coding at the relay for different classes of data packets corresponding to WBAN applications. <s> BIB002 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> Diversity techniques based on NC: <s> In this paper we propose a highly reliable wireless body area network (WBAN) that provides increased throughput and avoids single points of failure. Such networks improve upon current WBANs by taking advantage of a new technology, Cooperative Network Coding (CNC). Using CNC in wireless body area network to support real-time applications is an attractive solution to combat packet loss, reduce latency due to retransmissions, avoid single points of failure, and improve the probability of successful recovery of the information at the destination. In this paper, we have extended Cooperative Network Coding, from its original configuration (one-to-one) to many-to-many as in multiple-input-multiple-output (MIMO) systems. Cooperative Network Coding results in increased throughput and network reliability because of the cooperation of the nodes in transmitting coded combination packets across spatially distinct paths to the information sinks. <s> BIB003 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> Diversity techniques based on NC: <s> In this paper we present and contrast two approaches, Cooperative Network Coding (CNC) and Cooperative Diversity Coding (CDC) to achieving reliable wireless body area networks. CNC combines cooperative communications and network coding, while CDC combines cooperative communication and diversity coding. These approaches also provide enhanced throughput and transparent self-healing which are desirable features that Wireless Body Area Networks should offer. Additionally, these feed-forward techniques are especially suitable for real-time applications, where retransmissions are not an appropriate alternative. Although, these techniques provide similar benefits, simulation results show that CDC provides higher throughput than CNC because of the fact that the network topology is known and few hops between the source and destination. Moreover, CDC has lower complexity, since the source and destination nodes know the coding coefficients. <s> BIB004 </s> A Survey on M2M Systems for mHealth: A Wireless Communications Perspective <s> Diversity techniques based on NC: <s> Relay sensor networks are often employed in end-to-end healthcare applications to facilitate the information flow between patient worn sensors and the medical data center. Medium access control (MAC) protocols, based on random linear network coding (RLNC), are a novel and suitable approach to efficiently handle data dissemination. However, several challenges arise, such as additional delays introduced by the intermediate relay nodes and decoding failures, due to channel errors. In this paper, we tackle these issues by adopting a cloud architecture where the set of relays is connected to a coordinating entity, called cloud manager. We propose a cloud-assisted RLNC-based MAC protocol (CLNC-MAC) and develop a mathematical model for the calculation of the key performance metrics, namely the system throughput, the mean completion time for data delivery and the energy efficiency. We show the importance of central coordination in fully exploiting the gain of RLNC under error-prone channels. <s> BIB005
Cooperation between nodes is a key mechanism that can be used to enhance diversity. Exploiting the broadcast wireless nature, nodes in the vicinity of the transmitter (relays) can actively contribute to the communication by forwarding any overheard packets to the destination. Recently, cooperative NC techniques have been studied as a potential way to enhance reliability in WBANs. The work presented in BIB003 shows the potential throughput improvement under error-prone channels through the application of network coding, as a function of the number of redundancy packets, the employed relays and the number of sink nodes. More advanced schemes, such as cooperative diversity coding where both coded and uncoded data packets are transmitted, can yield ever better results BIB004 . A tree topology has been assumed in BIB001 , where multiple nodes communicate with the coordinator through a small number of relays. The nodes send their uncoded data to the relays, which in turn forward a set of both coded and uncoded packets to the destination. The obtained results show that network coding can offer higher reliability with respect to traditional redundancy schemes where multiple retransmissions of uncoded packets take place. Similar conclusions are drawn in BIB002 , where the coding decisions take into account the reliability requirements of different traffic flows. Finally, a novel cloud-assisted MAC protocol, CLNC-MAC, that employs NC and guarantees the successful delivery of all generated data to the destination through a relay network, regardless of the channel conditions, has been proposed in BIB005 . The key concept behind CRNC-MAC is to employ cloud resources for the relay coordination, to ensure that all crucial information from the source is propagated without losses through the network (that may include multiple hops), thus enabling the successful decoding at the destination. This is achieved by employing a central coordinating entity, namely the cloud controller, which has the task of verifying the reception of all required information by the relays at a hop by hop basis, requesting retransmissions whenever necessary.