Auto-correlation receivers, such as frequency shift reference systems, offer a low-complexity alternative to Rake receivers, for low data-rate ultra-wideband applications. In such systems, a data signal and a reference signal are simultaneously transmitted. At the receiver, the received signal corresponding to the data is correlated with the received signal corresponding to the reference signal, thereby accumulating the multi-path channel energies in-phase. For improving bandwidth and energy efficiency, multi- differential schemes have also been proposed where multiple data signals share the same reference signal. With the aim of further boosting the achievable data rates, in this work we propose a multi-differential frequency shift reference receiver that supports higher order modulation formats. We design the corresponding receiver architecture that can exploit both the in-phase and quadrature-phase signal components and analytically characterize the signal and noise components. We also study the problem of optimal bit and power allocation to the multiple data signals, both for uncoded and coded systems, as a function of channel metrics that can be easily tracked at the receiver.

The heart rate variability (HRV) is the variation in the pulsing frequency of the human heart. Measuring this parameter can reveal important information on the real-time interaction between the autonomic nervous system and the cardiocirculatory system. It can provide useful insight on an individual's state of stress or well being even outside a clinical setting, thanks to inexpensive and unobtrusive wireless sensors and the computing capability of our smartphones. These sensors are battery operated, so their current sampling frequency may be inadequate to measure HRV parameters. In this article, we focus on the accuracy of the detection of the RR interval time series (the instantaneous heart rate), and we investigate the sampling frequency needed to obtain a given level of accuracy for different signals and HRV parameters. We provide the guidelines for an opportunistic choice of the sampling rate to achieve a desired accuracy, and we propose a series of techniques to improve this accuracy with a fixed sampling frequency. We show the effectiveness of the proposed techniques in terms of relative error reduction and energy savings for the wireless sensors.

Media streaming applications have recently attracted a large number of users in the Internet. With the advent of these bandwidth-intensive applications, it is economically inefficient to provide streaming distribution with guaranteed QoS relying only on central resources at a media content provider. Cloud computing offers an elastic infrastructure that media content providers (e.g., Video on Demand (VoD) providers) can use to obtain streaming resources that match the demand. Media content providers are charged for the amount of resources allocated (reserved) in the cloud. Most of the existing cloud providers employ a pricing model for the reserved resources that is based on non-linear time-discount tariffs (e.g., Amazon CloudFront and Amazon EC2). Such a pricing scheme offers discount rates depending non-linearly on the period of time during which the resources are reserved in the cloud. In this case, an open problem is to decide on both the right amount of resources reserved in the cloud, and their reservation time such that the financial cost on the media content provider is minimized. We propose a simple-easy to implement-algorithm for resource reservation that maximally exploits discounted rates offered in the tariffs, while ensuring that sufficient resources are reserved in the cloud. Based on the prediction of demand for streaming capacity, our algorithm is carefully designed to reduce the risk of making wrong resource allocation decisions. The results of our numerical evaluations and simulations show that the proposed algorithm significantly reduces the monetary cost of resource allocations in the cloud as compared to other conventional schemes.

Many mobile devices e.g., smart phones, PDAs, portable computers and wireless routers e.g., WiFi access points nowadays are equipped with ad hoc transmission mode. In a dense environment such as a college/office campus, this creates the possibility of forming a wireless mesh network WMN in which mobile users communicate with each other through multiple wireless hops. This allows mobile users to exchange share files over the free access WMN rather than a carrier frequency such as 3G and WiMax. We consider a peer-to-peer P2P content sharing setting in a WMN, wherein the mesh network operator over-provision a number of mesh routers in the network with additional storage capacity and P2P-aware devices that are programmed to cache and store P2P content. Those mesh routers act as caches and participants in P2P content sharing. The aim of this setting is to both reduce the cost of communications between peers within the WMN i.e., reduce bandwidth and energy that P2P traffic consumes in the network, and enhance the performance of P2P content sharing i.e., reduce the average P2P content download delay. Our main contribution in this paper is an optimum P2P content replication strategy at the participating mesh routers. In particular, we determine the optimum number of replicas for every P2P file such that the average access cost of all files in the network is minimized. We propose a centralized algorithm that enables the participating mesh routers to implement the optimal strategy. We further propose a distributed low cost algorithm for P2P content replication at the participating mesh routers, and show that the distributed algorithm mimics the optimal strategy very well. The analytical and simulation results show that our replication strategy significantly reduces the average overall cost of accessing P2P files in the WMN as compared with other commonly used replication strategies. Copyright © 2013 John Wiley & Sons, Ltd.

Smart Grid (SG) uses communication technology to gather information about the actual and planned power usage in order to enable efficient power provisioning and consumption. Wireless multi-hop communications are used for exchanging data and control messages between smart meters and the utility. With the advent of cybercrimes, there is a growing concern on privacy of the clients. We argue that any communication paradigm used in the SG should support privacy, anonymity, unlinkability, unobservablity, and undetectablity. Due to the broadcast nature of wireless transmissions, many cyber-attacks such as traffic analysis and flow tracing compromise privacy of the clients. We propose an innovative scheme for traffic routing that benefits from the enhanced network coding technology. Our analysis shows that our scheme maintains privacy of the users despite the possibility of detecting transmitted traffic by an adversary. Moreover, our scheme has extra favourable features such as less computation complexity and robustness of communication.

In a smart grid system, the metering data collected by smart meters (SMs) and transferred via an Advanced Metering Infrastructure to the utility for billing purposes, and to the demand-response system to achieve cost effective resource allocation. The collected data at the SMs are sent to aggregators (AGRs), which in turn forward these data to a higher layer data collection system using secured communications. However, metering data are typically transferred between SMs and AGRs over wireless multi-hop communication networks. Due to the broadcast nature of wireless transmissions, the communications between a SM and AGR are susceptible to many security attacks. We argue that advanced network coding (NC) technology can be utilized to address this problem. We propose a novel system that supports data collection security at AGR by encrypting metering data transmitted between SMs and AGR using NC technology. Our innovative scheme eliminates the use of previously specified public key encryption system between SMs and AGR, which consequently makes our system very efficient. Analyses show that our proposed scheme enhances robustness and throughput of data routing in the wireless multi-hop network between SMs and AGR while maintaining a strong security.

ABSTRACT Wireless mesh networks (WMNs) have emerged as a promising technology that provides low‐cost broadband access to the Internet for fixed and mobile wireless end users. An orthogonal evolution in computer networking has been the rise of peer‐to‐peer (P2P) applications such as P2P data sharing. It is of interest to enable effective P2P data sharing in this type of networks. Conventional P2P data sharing systems are not cognizant of the underlying network topology and therefore suffer from inefficiency. We argue for dual‐layer mesh network architecture with support from wireless mesh routers for P2P applications. The main contribution of this paper is P2PMesh: a topology‐aware system that provides combined architecture and efficient schemes for enabling efficient P2P data sharing in WMNs. The P2PMesh architecture utilizes three schemes: (i) an efficient content lookup that mitigates traffic load imbalance at mesh routers; (ii) an efficient establishment of download paths; and (iii) a data transfer protocol for multi‐hop wireless networks with limited capacity. We note here that the path establishment and data transfer schemes are specific to P2P traffic and that other traffic would use routes determined by the default routing protocol in the WMN. Simulation results suggest that P2PMesh has the potential to improve the performance of P2P applications in a wireless multi‐hop setting; specifically, we focused on data sharing, but other P2P applications can also be supported by this approach. Copyright © 2011 John Wiley & Sons, Ltd.

We consider the problem of energy consumption in sharing a viral file between peers over a wireless community network (e.g., students in campus). Wireless community networks such as Wireless Mesh Networks (WMNs) have been accepted as a new communication approach that enables users to share the network resources and reduce the cost of the Internet access. The common paradigm for sharing content between users in a community network is through the use of a centralized server. Another scheme is to exploit the upload capacity of peers who are interested in the same content (e.g., Peer-to-Peer (P2P) file sharing). In this paper, we consider a content distribution setting in a wireless mesh network wherein a number of infrastructure nodes (mesh routers) support the P2P content sharing and act as caches and participants. We model the performance of this content distribution scheme, and analytically compute the energy that is consumed in the network when a viral P2P object is shared between the peers in a WMN. We compare the energy consumption with the centralized server scheme using both numerical results and detailed simulations. The results shows significant reduction in energy consumption (more than an order of magnitude) when only few replicas of the object is cached at the infrastructure nodes.

We consider a Peer-to-Peer (P2P) data sharing setting in wireless mesh networks (WMNs), wherein few mesh routers are provisioned with storage capacity and act as caches and participants in the P2P content sharing. Our contributions in this paper are optimum replication strategies for the P2P objects at the participating mesh routers to reduce the communication cost between peers within the WMN. We determine the optimum number of replicas for each object such that the average access cost of all objects in the network is minimized. We then propose a distributed algorithm for object replication and show that the distributed algorithm mimics the optimal strategy very well. The simulation results show that our strategy reduces the communication cost as compared to other commonly used strategies by a ratio of ≈20%.

Wireless Mesh Networks (WMNs) have been widely deployed as a new communication paradigm that can provide innovative services for a community (neighborhood, campus, etc.). WMNs are capable to provide both delay-sensitive services such as Voice over Internet Protocol (VoIP) and delay-insensitive services such as peer-to-peer file sharing. Network routing protocols in WMNs often employ the minimum-hops routing metric to provide Quality of Service (QoS) for the delay-sensitive traffic. However, this approach results in unbalanced traffic load at network mesh routers. In this paper, we propose the WMN-Balance: a content lookup algorithm for peer-to-peer file sharing over wireless mesh networks. The WMN-Balance enhances the content lookup routing on the overlay network, that involves mesh routers which support peer-to-peer file sharing, to mitigate the network unbalanced load.

Wireless mesh networks are being widely deployed around the world as a mean to provide low-cost access to the Internet. The high capacity at mesh routers nodes allows applications such as real time multicast over WMNs. In light of the slow development of IP multicast and the rise of peer-to-peer communication, implementing multicast capability at the application layer is imminent. QoS support for application layer multicast over WMNs is challenging due to the architecture of the overlay networks, characteristics of the wireless medium, and end users limited bandwidth efficiency. We argue for ring-based overlay multicast scheme with support from wireless mesh routers for the multicast applications. We demonstrate, using extensive simulations, that this approach has excellent potential to improve the performance of the peer-to-peer multicast applications in a wireless setting; specifically we focus on many-to-many real time multimedia applications but other applications can also be supported by this approach.