Jussi Haapola

UWB wireless sensor networks: UWEN - a practical example

The research topic of sensor networks has been around for some time. With improvements in device size, power consumption, communications, and computing technology, sensor networks are becoming more popular for an ever increasing range of applications. Since 2002, there has been an increased in the popularity of commercial applications based on ultra wideband. This, in turn, has ignited interest in the use of this technology for sensor networks and fuelled research in the area. Impulse-radio-based UWB technology has a number of inherent properties that are well suited to sensor network applications. In particular, UWB systems have potentially low complexity and low cost, have noise-like signal, are resistant to severe multipath and jamming, and have very good time domain resolution allowing for location and tracking applications. This article examines one example of a UWB sensor network for outdoor sport and lifestyle applications.

Energy optimization in multihop wireless embedded and sensor networks

This paper provides an analytical model for the study of energy consumption in multihop wireless embedded and sensor networks where nodes are extremely power constrained. Low-power optimization techniques developed for conventional ad hoc networks are not sufficient as they do not properly address particular features of embedded and sensor networks. It is not enough to reduce overall energy consumption, it is also important to maximize the lifetime of the entire network, that is, maintain full network connectivity for as long as possible. This paper considers different multihop scenarios to compute the energy per bit, efficiency and energy consumed by individual nodes and the network as a whole. The analysis uses a detailed model for the energy consumed by the radio at each node. Multihop topologies with equidistant and optimal node spacing are studied. Numerical computations illustrate the effects of packet routing, and explore the effects of coding and medium access control. These results show that always using a simple multihop message relay strategy is not always the best procedure.

Cross-layer Energy Analysis of Multi-hop Wireless Sensor Networks

In this paper, we propose a detailed energy survey of the physical, data link, and network layer by analytical techniques. We also show the impact of regular sleep periods on node energy consumption and present a comparison analysis of single-hop vs. multi-hop communications in the energy realm. A detailed energy expenditure analysis of not only the physical layer but also the link and network layer provides a basis for developing new energy efficient wireless sensor networks. Regular, coordinated sleeping extends the lifetime of sensor nodes, but systems can only benefit from sleeping in terms of transmitted packets if the data arrival rate to the system is low. Energy efficiency is the driving motivation for it can be considered the most important factor for wireless sensor networks because of the power constraints set by battery operation. Radio solutions in the lower ISM bands are attractive because of their relatively easy implementation and low power consumption. However, the data rates of these commercial radios are also relatively low, limiting transmittable frame sizes to a few tens of octets along with strict duty cycle requirements. From the analysis we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have some inherent problems. We also argue that single-hop communications has up to 40% lower energy consumption than multihop forwarding within the feasible transmission distances of an ISM radio.

Multihop medium access control for WSNs: an energy analysis model

We present an energy analysis technique applicable to medium access control (MAC) and multihop communications. Furthermore, the techniques application gives insight on using multihop forwarding instead of single-hop communications. Using the technique, we perform an energy analysis of carrier-sense-multiple-access (CSMA-) based MAC protocols with sleeping schemes. Power constraints set by battery operation raise energy efficiency as the prime factor for wireless sensor networks. A detailed energy expenditure analysis of the physical, the link, and the network layers together can provide a basis for developing new energy-efficient wireless sensor networks. The presented technique provides a set of analytical tools for accomplishing this. With those tools, the energy impact of radio, MAC, and topology parameters on the network can be investigated. From the analysis, we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have inherent problems.

Implementation and performance evaluation of nanoMAC: a low-power MAC solution for high density wireless sensor networks

This paper describes the implementation architecture and performance analysis of nanoMAC, a CSMA/CA based Medium Access Control (MAC) protocol, which is specifically designed for high density Wireless Sensor Networks (WSNs). We empirically show that nanoMAC performs with high reliability in a variety of network traffic conditions in single and multihop scenarios. For energy efficient operation and minimising idle-overhearing, nanoMAC uses a specialised sleep algorithm. We also show results from a comparative study of nanoMAC with Berkeleys MAC (B-MAC) in terms of performance measures, as well as their coexistence in networks deployed in overlapping or nearby areas.

Impact of smart grid traffic peak loads on shared LTE network performance

The purpose of the paper is to examine if public long term evolution (LTE) network is suitable for smart grid (SG) automatic metering usage, in a suburban scenario, without causing significant hindrance to typical LTE traffic. In addition, the same generalized suburban scenario is evaluated with a hybrid sensor - LTE network where wireless sensor network (WSN) cluster heads are also equipped with LTE remote terminal units (RTUs). The simulation topology is formed as a suburban area that consists of single RTU per apartment/house for SG traffic and an average 3.7 people per habitat, each with their user equipment, using one of the available carriers. Normal SG traffic is generated in both directions, uplink and downlink. The worst-case usage factor is considered as a power outage, where all SG meters in the area of influence simultaneously detect and attempt to report such a failure. Thus, emergency SG traffic is generated simultaneous by all RTUs. To alleviate the problem of the high momentary SG emergency traffic load, two distinct solutions are proposed and simulated. As the first solution, an artificial, up to one-second random delay is introduced in the transmission scheduling of emergency messages. The second solution applies low-power WSNs at the cluster level and cluster heads that contain both 802.15.4 and LTE communication interfaces, i.e., a hybrid sensor-LTE network. The simulation results show that both of the solutions that try to alleviate the high instantaneous traffic loads can reach the quality of service criteria for SG traffic without compromising other public LTE traffic. The deciding factor to use either pure LTE approach or a hybrid sensor-LTE network comes from non-functional requirements of the system.

Effect of Impulse Radio–Ultrawideband Based on Energy Collection on MAC Protocol Performance

In this paper, we analyze the effects of the probabilities of detection, false alarm, and frame collision survival (in the presence of simultaneous transmissions) on medium access control (MAC) protocols using impulse-radio-ultrawideband (IR-UWB) energy-collection noncoherent receivers. The MAC protocols that were considered are all IEEE 802.15.4 compatible, i.e., the IEEE 802.15.4a optional UWB clear-channel-assessment mode, the IEEE 802.15.4a ALOHA mode, and a protocol termed preamble sense multiple access (PSMA). The impact on the network throughput, energy consumption, and delay are analytically derived and verified by simulation. The results show that these effects have a considerable impact on the performance of IR-UWB MAC protocols, and a classical analysis does not properly evaluate the protocolspsila performances. The results compare the performances of the MAC protocols and highlight a number of issues with regard to adapting narrowband protocols to UWB systems. The probability of frame collision survival on simultaneous transmissions is shown to have a significant impact on the performance of a MAC protocol. The comparison shows superior performance of the PSMA protocol under typical wireless-sensor-network operation ranges.

LTE and hybrid sensor-LTE network performances in smart grid demand response scenarios

The paper conducts an evaluation of traffic volumes, delivery ratios, and delays under various demand response (DR) setups using two distinct wireless solutions for smart grid (SG) communications. The first solution considers public long term evolution (LTE) network and the second one considers cluster-based hybrid sensor-LTE network where wireless sensor network (WSN) clusterheads are also equipped with LTE remote terminal units. The DR scenarios reflect cases where certain percentages of end users take part in automated DR-based load balancing while the rest of the users resort to advanced metering infrastructure based energy monitoring. In the DR cases various setups of energy consumption monitoring and load-balancing feedback are simulated. The purpose is to identify the limits of reporting and feedback intervals of the two communications technology setups for DR operations. DR and its management are becoming more important as distributed energy generation becomes more popular in households due to reducing prices of small-scale renewable energy generation equipment. The use of public telecommunications infrastructure is a good candidate for enabling DR communications over SGs, but it is becoming more congested by the increasing mobile data usage of consumers. The results show that both of the solutions have their advantages, LTE communications generally providing a higher delivery ratio whereas, surprisingly, hybrid sensor-LTE communications generally provides lower uplink delay.

Implementation and Performance Evaluation of nanoMAC: A Low-Power MAC Solution for High Density Wireless Sensor Networks

This paper describes the implementation architecture and performance analysis of nanoMAC, a CSMA/CA based medium access control protocol, which is specifically designed for high density wireless sensor networks. We empirically show that nanoMAC performs with high reliability in a variety of network traffic conditions in single and multihop scenarios. For energy efficient operation and minimizing idle-overhearing, nanoMAC uses a specialized sleep algorithmWe also show results from a comparative study of nanoMAC with B-MAC in terms of performance measures.

Feasibility study of IEEE 802.15.4e DSME utilizing IR-UWB and S-Aloha

In this paper, we analyze the effects of guaranteed time slots (GTSs) to the performance of IEEE 802.15.4 slotted Aloha (S-Aloha) medium access control (MAC) protocol utilizing impulse radio ultrawideband (IR-UWB) technology. IEEE 802.15.4e, amendment to IEEE 802.15.4 standard, defines an optional MAC scheme termed as deterministic and synchronous multi-channel extension (DSME). One of the key features of DSME is that it enables the MAC to operate in fully scheduled mode utilizing DSME-GTS slots for communications. The feasibility of DSME-GTSs is analytically derived in terms of throughput and it is verified by simulations performed in Opnet. Furthermore, the impact of DSME-GTSs for packet delivery ratio and delay is simulated in wireless hospital room scenario and the results are compared to contention-based operation of IEEE 802.15.4 MAC. The results show that significantly higher throughput and packet delivery ratio is achieved when IEEE 802.15.4 MAC operates in fully scheduled mode. In addition, fully scheduled mode guarantees upper bound for end-to-end data packet delay, and therefore it is the preferable mode for transmitting vital biomedical information.