A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> Surface-penetrating radar is a nondestructive testing technique which uses electromagnetic waves to investigate the composition of nonconducting materials either when searching for buried objects or when measuring their internal structure. A typical surface-penetrating radar transmits a short pulse of electromagnetic energy of 1 ns (10/sup -9/ s) time duration from a transmit antenna into the material. Energy reflected from discontinuities in impedance is received by means of a receive antenna and is then suitably processed and displayed by a radar receiver and display unit. If the transmit and receive antennas are moved at a constant velocity along a linear path, a cross-sectional image of the material can be generated. Alternatively, if the antennas are scanned in a regular grid pattern, a three-dimensional image of the target can be derived. This paper provides a review of the principles of the technique, discusses the technical requirements for the individual subsystems comprising a surface-penetrating radar and provides examples of typical applications for the method. Continued technical improvements in system performance enable clearer radar images of the internal structure of materials to be obtained, thus advancing the application of the technique. <s> BIB001 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> In this paper, we investigate the issue of error control in wireless communication networks. We review the alternative error control schemes available for providing reliable end-to-end communication in wireless environments. Through case studies, the performance and tradeoffs of these schemes are shown. Based on the application environments and QoS requirements, the design issues of error control are discussed to achieve the best solution. <s> BIB002 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> The potential for collaborative, robust networks of microsensors has attracted a great deal of research attention. For the most part, this is due to the compelling applications that will be enabled once wireless microsensor networks are in place; location-sensing, environmental sensing, medical monitoring and similar applications are all gaining interest. However, wireless microsensor networks pose numerous design challenges. For applications requiring long-term, robust sensing, such as military reconnaissance, one important challenge is to design sensor networks that have long system lifetimes. This challenge is especially difficult due to the energy-constrained nature of the devices. In order to design networks that have extremely long lifetimes, we propose a physical layer driven approach to designing protocols and algorithms. We first present a hardware model for our wireless sensor node and then introduce the design of physical layer aware protocols, algorithms, and applications that minimize energy consumption of the system. Our approach prescribes methods that can be used at all levels of the hierarchy to take advantage of the underlying hardware. We also show how to reduce energy consumption of non-ideal hardware through physical layer aware algorithms and protocols. <s> BIB003 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> Wireless microsensor systems are used in a variety of civil and military applications. Such microsensors are required to operate for years from a small energy source. To minimize the energy dissipation of the sensor node, RF front-end circuitry must be designed based on system level optimization of the entire network. This paper presents several energy minimization techniques derived from the unique properties of a practical short range asymmetric microsensor system. These include energy efficient modulation schemes, appropriate multiple access protocols, and a fast turn-on transmitter architecture. <s> BIB004 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> Targeted at multi-hop wireless sensor networks, a set of low power MAC design principles have been proposed, and a novel ultra-low power MAC is designed to be distributed in nature to support scalability, survivability and adaptability requirements. Simple CSMA and spread spectrum techniques are combined to trade off bandwidth and power efficiency. A distributed algorithm is used to do dynamic channel assignment. A novel wake-up radio scheme is incorporated to take advantage of new radio technologies. The notion of mobility awareness is introduced into an adaptive protocol to reduce network maintenance overhead. The resulting protocol shows much higher power efficiency for typical sensor network applications. <s> BIB005 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed. <s> BIB006 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> The traffic-adaptive medium access protocol (TRAMA) is introduced for energy-efficient collision-free channel access in wireless sensor networks. TRAMA reduces energy consumption by ensuring that unicast, multicast, and broadcast transmissions have no collisions, and by allowing nodes to switch to a low-power, idle state whenever they are not transmitting or receiving. TRAMA assumes that time is slotted and uses a distributed election scheme based on information about the traffic at each node to determine which node can transmit at a particular time slot. TRAMA avoids the assignment of time slots to nodes with no traffic to send, and also allows nodes to determine when they can become idle and not listen to the channel using traffic information. TRAMA is shown to be fair and correct, in that no idle node is an intended receiver and no receiver suffers collisions. The performance of TRAMA is evaluated through extensive simulations using both synthetic- as well as sensor-network scenarios. The results indicate that TRAMA outperforms contention-based protocols (e.g., CSMA, 802.11 and S-MAC) as well as scheduling-based protocols (e.g., NAMA) with significant energy savings. <s> BIB007 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> A sensor network is a collection of wireless sensor nodes, each equipped with embedded processor, memory, and a wireless transceiver, that may be designed to perform distributed sensing and tracking operations. The sensor nodes use ad hoc networking principles to communicate amongst themselves. However, limitations of battery power in the sensor nodes and the bursty and correlated nature of traffic in the network introduce additional constraints for designing the communication protocols for sensor networks over that of traditional ad hoc networks. This paper proposes a reservation based medium access control (MAC) protocol for sensor networks that provides a high probability of success in packet transmissions, low average energy consumption, and adaptability to the traffic requirements to maximize the data throughput. <s> BIB008 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> This paper presents the Simple Packet Combining (SPaC) error-correction scheme for wireless sensor networks. Nodes buffer corrupt packets, and when two or more corrupt versions of a packet have been received, a packet combining procedure attempts to recover the original packet from the corrupt copies. Packet combining exploits the broadcast medium and spatial diversity of a multi-hop wireless network by using packets overheard at any node, in addition to the next-hop destination of the packet itself. Unlike point-to-point forward error correction (FEC), packet combining therefore helps multi-node interactions such as multi-hop routing or broadcasting as well as to hop-by-hop communication. Also, SPaC does not transmit redundant overhead on good links and does not require costly probes to estimate channel conditions.We have implemented SPaC as a link-layer extension on sensor nodes; it is transparent to upper layer protocols and has low memory and CPU footprints. We evaluate performance through a combination of analysis, trace-driven simulation, indoor and outdoor testbed micro-benchmarks, and deployment on a live network. The results show significant performance gains, even when accounting for the energy cost of CPU processing. We also present detailed bit-level link measurements and the design and evaluation of a new preamble detection scheme motivated by these measurements. <s> BIB009 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> This paper describes the Multi-Radio Diversity (MRD) wireless system, which uses path diversity to improve loss resilience in wireless local area networks WLANs). MRD coordinates wireless receptions among multiple radios to improve loss resilience in the face of path-dependent frame corruption over the radio. MRD incorporates two techniques to recover from bit errors and lower the loss rates observed by higher layers, without consuming much extra bandwidth. The first technique is frame combining in which multiple, possibly erroneous, copies of a given frame are combined together in an attempt to recover the frame without retransmission. The second technique is a low-overhead retransmission scheme called request-for-acknowledgment (RFA), which operates above the link layer and below the network layer to attempt to recover from frame combining failures. We present an analysis that determines how the parameters for these algorithms should be chosen.We have designed and implemented MRD as a fully functional WLAN infrastructure based on 802.11a. In our testbed, we measured throughput gains up to 2.3 - over single radio communication schemes employing 802.11's autorate adaptation scheme. <s> BIB010 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> Datalink layer framing in wireless sensor networks usually faces a trade-off between large frame sizes for high channel bandwidth utilization and small frame sizes for effective error recovery. Given the high error rates of intermote communications, TinyOS opts in favor of small frame sizes at the cost of extremely low channel bandwidth utilization. In this paper, we describe Seda: a streaming datalink layer that resolves the above dilemma by decoupling framing from error recovery. Seda treats the packets from the upper layer as a continuous stream of bytes. It breaks the data stream into blocks, and retransmits erroneous blocks only (as opposed to the entire erroneous frame). Consequently, the frame-error-rate (FER), the main factor that bounds the frame size in the current design, becomes irrelevant to error recovery. A frame can therefore be sufficiently large in great favor of high utilization of the wireless channel bandwidth, without compromising the effectiveness of error recovery. Meanwhile, the size of each block is configured according to the error characteristics of the wireless channel to optimize the performance of error recovery. Seda has been implemented as a new datalink layer in the TinyOS, and evaluated through both simulations and experiments in a testbed of 48 MicaZ motes. Our results show that, by increasing the TinyOS frame size from the default 29 bytes to 100 bytes (limited by the buffer space at MicaZ firmware), Seda improves the throughput around 25% under typical wireless channel conditions. Seda also reduces the retransmission traffic volume by more than 50%, compared to a framebased retransmission scheme. Our analysis also exposes that future sensor motes should be equipped with radios with more packet buffer space on the radio firmware to achieve optimal utilization of the channel capacity. <s> BIB011 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> This work introduces the concept of a Wireless Underground Sensor Network (WUSN). WUSNs can be used to monitor a variety of conditions, such as soil properties for agricultural applications and toxic substances for environmental monitoring. Unlike existing methods of monitoring underground conditions, which rely on buried sensors connected via wire to the surface, WUSN devices are deployed completely belowground and do not require any wired connections. Each device contains all necessary sensors, memory, a processor, a radio, an antenna, and a power source. This makes their deployment much simpler than existing underground sensing solutions. Wireless communication within a dense substance such as soil or rock is, however, significantly more challenging than through air. This factor, combined with the necessity to conserve energy due to the difficulty of unearthing and recharging WUSN devices, requires that communication protocols be redesigned to be as efficient as possible. This work provides an extensive overview of applications and design challenges for WUSNs, challenges for the underground communication channel including methods for predicting path losses in an underground link, and challenges at each layer of the communication protocol stack. � 2006 Elsevier B.V. All rights reserved. <s> BIB012 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> A wireless sensor network (WSN) has important applications such as remote environmental monitoring and target tracking. This has been enabled by the availability, particularly in recent years, of sensors that are smaller, cheaper, and intelligent. These sensors are equipped with wireless interfaces with which they can communicate with one another to form a network. The design of a WSN depends significantly on the application, and it must consider factors such as the environment, the application's design objectives, cost, hardware, and system constraints. The goal of our survey is to present a comprehensive review of the recent literature since the publication of [I.F. Akyildiz, W. Su, Y. Sankarasubramaniam, E. Cayirci, A survey on sensor networks, IEEE Communications Magazine, 2002]. Following a top-down approach, we give an overview of several new applications and then review the literature on various aspects of WSNs. We classify the problems into three different categories: (1) internal platform and underlying operating system, (2) communication protocol stack, and (3) network services, provisioning, and deployment. We review the major development in these three categories and outline new challenges. <s> BIB013 </s> A Survey Report on Operating Systems for Tiny Networked Sensors <s> A. Communication Protocols and issues <s> Wireless Sensor networks (WSNs) are composed of small hardware devices that possess the ability to measure and exchange a variety of environmental data. In this paper, we measured the radio characteristics of IEEE 802.15.4 for wireless sensor networks. The system is mainly composed of mobile and static ZigBee nodes, which are deployed on the underground mine galleries. Based on measured data, we describe the link characteristics such as received signal strength, latency and throughput for different scenarios. We consider the impact of these findings on the design of WSN for monitoring applications in underground mines. <s> BIB014
A sensor network consists of different layers in a protocol stack. Physical layer deals with transmission media, modulation technique, receiving of bits and connectivity among nodes. Due to the dynamic topology of a sensor node Medium access control (MAC) applied to a sensor network must be aware of power consumption and should be able to minimize the collision of data packets BIB013 . Routing of data is taken care by the network layer and it further gives services to the transport layer. End to end data flow into a sensor network is with transport layer functionalities. Various power efficient algorithms have been proposed which is smart enough so that after receiving a message the node may turn off its receiver, which prevents the further receipt of duplicate messages. Additionally, a node can go into sleep mode for a specified amount of time and can pass a broadcast message in the network about shorting in power so cant participate in routing BIB013 , BIB006 . This gives an obvious power saving and this can further utilize in sensing. Although there are a number of literatures available describing the different layer functionalities of WSN. The main objective of this section is to address some open research issues. This section highlights only some critical research issues at every layer so that the reliability and efficiency of communication devices can be addressed in the future research. 1) Physical layer: Physical layer deals with the transmission of data, connectivity, modulation techniques and synchronizations. This faces different challenges for wireless communication to be possible. This layer interacts with the MAC layer of data link layer performing reception and bit synchronization. In BIB012 , the authors found that the error rate at the physical layer is high when the distance be-tween transmitter and receiver is increased. Energy consumption is one of the critical point for WSN. As the WSN has limited power source, hence to minimize the energy consumption and maximizing the life of a sensor node is vital. Physical layer uses power for bit stream transmission and radio operation. The amount of energy consumes to transmit a data stream can be adversely affected and varies due to the interference, multipath effects, fading and distance between the transmitter and receiver BIB012 . Whereas the energy consumption is fixed to operate circuitry. The energy consumption of the different radio chip used in WSN nodes is listed in subsection "Sensor Nodes". An efficient modulation technique for channel is another issue which is important for minimizing energy consumption by the network. BIB003 , BIB004 have carried out comparative analysis between binary modulation and multi-level (M-ary) modulation scheme and noticed that the energy consumed by the M-ary modulation is less and energy efficient than binary modulation. This occurs when the output power of RF is small and the time interval for start-up is less. On further comparison they found that when M is greater than eight, the M-ary phase shift keying and M-ary quadrature amplitude modulation scheme consumes more energy than the M-ary frequency shift keying. In addition to energy consumption, a comparative analysis of Binary and M-ary has been done and it was found that M-ary is capable to reduce the transmit time by transmitting multiple bits per symbol but it leads to a complex circuitry which in results consumes more power BIB001 . Further in their Fig. 2 : WSN Communication Protocol Architecture studies they suggested that binary modulation is good because it takes less power hence, is energy efficient. Choices for bandwidth also needs research efforts, as in WSN there are three major choices available at physical layer: spread spectrum, narrow band and ultra wideband (UWB). It may be noted that research efforts are there by the researchers on communication possibilities based on spread spectrum and narrow band, however, there are only limited literatures available which have the information on UWB based sensor communications. Therefore, the scope of UWB based sensor communications required more research efforts and implementations in real world scenarios. 2) Data Link Layer: The Data link layer is responsible for data transfer between the two; not sharing the same link. For better functionalities the MAC layer protocol design should have the following features  , BIB013 : support scalability, maximize bandwidth utilization, data frame synchronization and energy efficient. Transport layer and data link layer both deals with the error detection and correction mechanisms. There are issues for designing MAC protocols which include mainly network topology, energy consumption and throughput of the overall network. A number of researchers have proposed solutions to address energy consumptions in sensor nodes. The various power saving modes and mechanism for listening network to minimize energy consumption by the nodes have been reported by different researchers which helps to enhance the lifetime of the network BIB005 , BIB008 , BIB007 . Cross layer optimization and overall system performance are one of the future issues which can significantly improve the performance of the WSN. Dynamic change in topology and mobile network has forced researchers to explore the optimal design considerations for future needs of industries. The number of transmission must be minimized for maximizing the life of sensor nodes. In WSN there are various techniques used for recovery of data includes simple packet combining (SPAC) BIB009 , automatic repeat request (ARQ) BIB011 , forward error correction (FEC)  , hybrid ARQ (HARQ) BIB002 and multi radio diversity (MRD) BIB010 . Among these all FEC, significantly decreases the number of data transmission. This gives the advantage of reduced acknowledgement wait time and also the retransmission of data is avoided. Efficient research on trade-offs between the contention based MAC protocol and time divison multiple access (TDMA) /carrier sense multiple access (CSMA) is required BIB013 . To target WSN communication applications in industries, Forward Error Check (FEC) technique is required to be researched extensively so that the retransmission of data can be minimized. 3) Network Layer: A network layer protocol design for WSN should address the critical issues of fault tolerance, scalability, and efficiency  . Network protocol is needed for sensor nodes to build a communication network. The network protocol plays an important role to define the sequential instructions for the sensor nodes to take in order to communicate with other nodes and also for data formats. A sensor network is further challenged by the physical communication environment followed by the parameters like bit error rate, dynamic topology and also the resources available to individual nodes. Routing protocols used in an ad-hoc network is categorized into three: reactive, proactive and geographical. Reactive protocols establish a route discovery whenever required in the network. While the proactive routing protocols are responsible for monitoring paths between the devices in the network. Routes are setup based on the physical location of the devices by the geographical routing protocols BIB012 . Research on low duty cycles of the network should be examined. Routing protocols satisfying Quality of Service (QOS) can surely minimize end to end delay and energy efficiency. Research efforts are needed for QOS routing protocols in wireless sensor network. Design of routing protocol should withstand with the continuous changing topology of the network and must support scalability for future needs BIB013 . It should be such that the network performance may not get affected. 4) Transport Layer: Reliability and data accuracy at the receiver and sender ends are taken care by the transport layer protocols. The design of transport layer protocol should be such that it supports the concept generic i.e. for all applications BIB013 . As the different communication devices are developed by different manufacturers, the transport layer protocols should support heterogeneous network. Therefore, the developed protocols should have the vision of universal acceptance and can be applied to any kind of communication devices. Any loss in data packets directly affects the quality of service and wasted energy. Therefore, the protocol should be smart enough which can minimize this issue and able to detect and recover the lost data. It surely helps for better throughput and low energy consumptions. Reliability of network is directly connected to the throughput. Optimization of sensed data at nodes is another issue to reduce the congestion in the network. Trade-off between the loss of information and delay is further research issue for WSN. 5) Cross Layer Interaction: MAC layer capabilities of cross layer communications can save energy with the routing knowledge of neighbors. The variations in power level for transmission can be utilized further by the routing protocols. It is done with the knowledge that which link is taking the least amount of power to transmit. This effort reduces the energy consumption and hence, increases the lifetime of the network. Cross layer designs for WSN enhance the performance of the network. Changing topology due to the mobility can be useful for other nodes to transmit and update the route information. A cross layer MAC design shares this topology information in the network to support reliable routing and maximizing coverage for communication BIB012 , BIB014 .