Vehicular safety applications have much significance in preventing road accidents and fatalities. Among others, cellular networks have been under investigation for the procurement of these applications subject to stringent requirements for latency, transmission parameters, and successful delivery of messages. Earlier contributions have studied utilization of Long‐Term Evolution (LTE) under single cell, Friis radio, or simplified higher layer. In this paper, we study the utilization of LTE under multicell and multipath fading environment and introduce the use of adaptive awareness range. Then, we propose an algorithm that uses the concept of quality of service (QoS) class identifiers (QCIs) along with dynamic adaptive awareness range. Furthermore, we investigate the impact of background traffic on the proposed algorithm. Finally, we utilize medium access control (MAC) layer elements in order to fulfill vehicular application requirements through extensive system‐level simulations. The results show that, by using an awareness range of up to 250 m, the LTE system is capable of fulfilling the safety application requirements for up to 10 beacons/s with 150 vehicles in an area of 2 × 2 km2. The urban vehicular radio environment has a significant impact and decreases the probability for end‐to‐end delay to be ≤100 ms from 93%–97% to 76%–78% compared to the Friis radio environment. The proposed algorithm reduces the amount of vehicular application traffic from 21 Mbps to 13 Mbps, while improving the probability of end‐to‐end delay being ≤100 ms by 20%. Lastly, use of MAC layer control elements brings the processing of messages towards the edge of network increasing capacity of the system by about 50%.

This research focuses on developing a positioning algorithm for Optical Wireless Communication (OWC) based indoor positioning systems. The proposed Two Receiver Indoor Positioning (TRIP) algorithm has the potential to overcome the light beam overlapping problem and locate the position of an object in an indoor environment precisely. The current research builds upon a previously proposed positioning algorithm named Optimal Beam Radius Indoor Positioning (OBRIP) algorithm and proposes the use of two receivers to detect the optical signal to further reduce the error in position estimation while also investigating the best values for important parameters like beam radius of transmitting Light-Emitting Diodes (LED), grid size of LED array and number of LEDs in an array for multiple room shapes. The performance analysis of TRIP algorithm and subsequent comparison with the performance of OBRIP algorithm is also carried out in this research using MATLAB simulations. From the simulation results, this algorithm proves to be effective for a room with floor dimensions of 10 m × 10 m yielding an average error in position estimation whose value is 0.69 m and surpasses the performance of the OBRIP with 30% lesser average error values. Using this technology for indoor positioning and tracking in the medical sector, and extending help to elderly dementia affected patients is a noble and intriguing idea.

In this work, we design an infrared protocol (IRP) for light emitting diode (LED) based indoor positioning. The designed IRP compensates for the shortcomings of other existing protocols when applied to the multiple LED estimation indoor positioning model (MLEM). MLEM uses overlap of LED beams to increase accuracy of positioning. The overlap sets up a multipoint-to-point optical communication channel. The existing protocols which are designed for point-to-point links, when modified to suit the MLEM overlapping region, show a high positioning time between 3 s and 4.5 s. These values are not desirable for real time tracking. A new protocol is therefore designed to reduce the positioning time. The protocol is implemented in an experimental MLEM design using ATmega 328 microcontroller hardware. The experimental results show the new protocol reduces the positioning time to 0.5 s.

The advent of data intensive applications on the mobile devices is putting a strain on the available RF spectrum. Recently, visible light wireless communications has become a desirable alternative due to the low cost of light emitting diode (LED) devices which can offer data rates in the Gigabit per second range while providing lighting. In addition, visible light belongs to the unlicensed part of spectrum which is easily reusable due to the fact that light does not penetrate walls. Various modulation techniques have been adopted for optical wireless because negative signals (or complex signals) cannot be used due to the fact that light intensity is a positive quantity. Orthogonal frequency division multiplexing (OFDM) has been successfully modified for optical wireless but it suffers from high peak-to-average-power ratio (PAPR). High PAPR causes LED to operate in nonlinear region which leads to performance degradation. We discuss a technique to reduce PAPR while keeping averaging power constraint which is important for the purpose of lighting.

In this paper, we propose a novel Virtual Multiple-Input-Multiple-Output (VMIMO) architecture based on the concept of Spatial Modulation (SM). Using a dual-hop and Decode-and-Forward protocol, we form a distributed system, called Dual-Hop Hybrid SM (DH-HSM). DH-HSM conveys information from a Source Node (SN) to a Destination Node (DN) via multiple Relay Nodes (RNs). The spatial position of the RNs is exploited for transferring information in addition to, or even without, a conventional symbol. In order to increase the performance of our architecture, while keeping the complexity of the RNs and DN low, we employ linear precoding using Channel State Information (CSI) at the SN. In this way, we form a Receive-Spatial Modulation (R-SM) pattern from the SN to the RNs, which is able to employ a centralized coordinated or a distributed uncoordinated detection algorithm at the RNs. In addition, we focus on the SN and propose two regularized linear precoding methods that employ realistic Imperfect Channel State Information at the Transmitter. The power of each precoder is analyzed theoretically. Using the Bit Error Rate (BER) metric, we evaluate our architecture against the following benchmark systems: 1) single relay; 2) best relay selection; 3) distributed Space Time Block Coding (STBC) VMIMO scheme; and 4) the direct communication link. We show that DH-HSM is able to achieve significant Signal-to-Noise Ratio (SNR) gains, which can be as high as 10.5 dB for a very large scale system setup. In order to verify our simulation results, we provide an analytical framework for the evaluation of the Average Bit Error Probability (ABEP).

In this paper, we aim to study the Energy Efficiency (EE) of Spatial Modulation (SM) at different Base Stations (BSs) taking into account the total power consumption. Compared to conventional Multiple-Input Multiple-Output (MIMO) schemes, SM benefits from a single Radio Frequency (RF) chain which results in decreased power supply (W), higher EE (Mbits/J), and reduced complexity. Using the fundamental limits of Shannon capacity, we show that SM achieves a range of average data rates with only a fraction, which can be as low as 24% for four transmit antennas, of the total power supply of conventional MIMO. In addition, we demonstrate that the EE of the studied schemes is maximized for a certain average data rate and that SM achieves the highest EE among them. Finally, we note that a BS employing SM can be up to 67% more energy efficient compared to a BS under a conventional MIMO transmission scheme, for four transmit antennas.

Multiple-input-multiple-output systems provide a potential approach for achieving high communication capacities in optical wireless. A small amount of publications based on different scenarios are available. The current work will illustrate that a very good distribution of communication capacity can be achieved for certain configurations. In particular, we look at angle diversity receivers which are able to successfully identify transmitter directions. The investigated scenarios include 4x4 and 16x16 multiple-input-multiple-output configurations.

In this paper, a distributed and autonomous technique for resource and power allocation in orthogonal frequency division multiple access (OFDMA) femto-cellular networks is presented. Here, resource blocks (RBs) and their corresponding transmit powers are assigned to the user(s) in each cell individually without explicit coordination between femto-base stations (FBSs). The “allocatability” of each resource is determined utilising only locally available information of the following quantities: the required rate of the user; the quality (i.e., strength) of the desired signal; the frequency-selective fading on each RB; and the level of interference incident on each RB. Using a fuzzy logic system, the time-averaged values of each of these inputs are combined to determine which RBs are most suitable to be allocated in a particular cell, i.e., which resources can be allocated such that the user requested rate(s) in that cell are satisfied. Fuzzy logic presents a completely novel, low-complexity methodology for inter-cell interference coordination (ICIC). A comprehensive study of this system in a femtocell environment is performed, yielding system performance improvements in terms of throughput, energy efficiency and coverage over state-of-the-art ICIC techniques.

In this paper, Sphere Decoding (SD) algorithms for Spatial Modulation (SM) are developed to reduce the computational complexity of Maximum—Likelihood (ML) detectors. Two SDs specifically designed for SM are proposed and analysed in terms of Bit Error Ratio (BER) and computational complexity. Using Monte Carlo simulations and mathematical analysis, it is shown that by carefully choosing the initial radius the proposed sphere decoder algorithms offer the same BER as ML detection, with a significant reduction in the computational complexity. A tight closed form expression for the BER performance of SM—SD is derived in the paper, along with an algorithm for choosing the initial radius which provides near to optimum performance. Also, it is shown that none of the proposed SDs are always superior to the others, but the best SD to use depends on the target spectral efficiency. The computational complexity trade—off offered by the proposed solutions is studied via analysis and simulation, and is shown to validate our findings. Finally, the performance of SM—SDs are compared to Spatial Multiplexing (SMX) applying ML decoder and applying SD. It is shown that for the same spectral efficiency, SM—SD offers up to 84% reduction in complexity compared to SMX—SD, with up to 1 dB better BER performance than SMX—ML decoder.

A unique characteristic of spatial modulation (SM) is the three dimensional constellation diagram. This enables to trade-off traditional signal constellation diagrams with spatial constellation diagrams where the latter is defined by the physical antenna array. In this paper we investigate the optimum pairs of signal and spatial constellation sizes with respect to average bit error probability (ABEP) and energy efficiency. The analysis is performed for varying antenna correlations and channel conditions. Both numerical and closed-form results are presented which show that a significant performance gain can be obtained when the optimal constellation pairs are used.

In this paper, a novel scheduling mechanism that enhances both network spectral and energy efficiency is presented. In Pareto Optimal Scheduling (POS), mobile stations (MSs) are scheduled based on path gains such that the sufficient conditions for Pareto optimal power control (POPC) are fulfilled. This is performed in such a manner to maximise the number of concurrently transmitting MSs. Furthermore, a Stepwise Removal (SR) algorithm is introduced for the situation where links do not meet the sufficient conditions for power control. In this case, links are removed in order for other MSs to achieve their signal-to-interference-plus-noise ratio (SINR) targets. The targets of these remaining MSs are updated to prevent losses in system spectral efficiency caused by the link removals. Large network simulation results show that significant gains in spectral efficiency can be achieved over standard power control techniques, while additionally providing substantially improved energy efficiency.

In this paper, Pareto Femto-Cell Scheduling (PFCS), a novel scheduling mechanism for randomly deployed femto-cells, is presented. Here, the signal-to-interference-plus-noise ratio (SINR) targets of femto-users are adapted such that the sufficient conditions for Pareto optimal power control (POPC) are fulfilled. Furthermore, interference from full bandwidth users is managed such that as many mobile stations (MSs) as possible can transmit. Due to the random nature of femto-base station (FBS) deployment, interference graphs are used to group femto-cells (and hence, users) such that target spectral efficiencies can be achieved at Pareto optimum power. Simulation results show that PFCS achieves significant system capacity gains over other SINR-target-based power allocation techniques, while maximising coverage in dense mobile environments. Furthermore, substantial power savings can be achieved.

Spatial modulation (SM) and space shift keying (SSK) use only one out of several transmit antennas at a time to transmit data via an antenna index. In such a system, the information is encoded by exploiting channel randomness i.e. the fact that channels between different transmit and receive antennas are random. This difference is used to distinguish among the transmit antennas. While SSK uses only antenna index to transmit data, SM also uses ordinary signal modulation. In wireless secrecy systems, one of the key performance measures is secrecy capacity. It specifies the rate at which the transmitter can communicates on the main link to the desired receiver while this information cannot be decoded by the eavesdropper. We investigate SM and SSK in the context of wireless secrecy capacity when the underlying modulation and the difference between the legitimate and eavesdropper signal to noise ratios (SNRs) are varied.

In this paper, motivated by the relatively new concept of Spatial Modulation (SM), we are addressing the problem of Receive-Spatial Modulation (R-SM) under two cases of imperfect channel knowledge at the transmitter side. In the first case, we adopt a statistical model for the channel uncertainties, whereas in the second one a worst-case approach is followed and the channel uncertainties are expressed as a bounded set. Based on Zero-Forcing (ZF) precoding and using standard tools from optimization theory, we derive closed form solutions that turn out to be robust. Simulation results show that the proposed schemes have a performance close to the perfect channel knowledge scenario in low and mid-low SNRs. Furthermore, these designs can be applied to wide range of channels with different correlation states combined with a transmit power gain.

A novel modulation technique coined U-OFDM is proposed. U-OFDM uses different time sample states and an innovative rearrangement of the Orthogonal Frequency Division Multiplexing (OFDM) frame which allow for the creation of unipolar OFDM signals required for Optical Wireless Communication (OWC) with Light Emitting Diodes (LEDs). In comparison to similar techniques like DC-biased Optical OFDM (DCO-OFDM) and Asymmetrically Clipped Optical OFDM (ACO-OFDM), U-OFDM is both optically and electrically more power efficient in an Additive White Gaussian Noise (AWGN) channel, which is prevalent in an optical wireless system.

This paper constructs a model for Optical Spatial Modulation Orthogonal Frequency Division Multiplexing (O-SM-OFDM). It investigates the effects of different power allocation schemes on bit error ratio (BER) performance. Optical features such as the DCO technique, the LED non-linearity and the indoor optical channel are considered. Under power constraint, when making power difference between transmitters, we discussed trade-off between the accuracy of the spatial domain bits detection and that of signal domain bits detection. We investigated the relationship between transmitter power surplus, spatial BER, signal BER, system total BER and signal to noise ratio (SNR). The optimal point of transmission power difference is found to be around 11.5 dB.

In this paper, the impact of clipping noise on optical wireless communication (OWC) systems employing orthogonal frequency division multiplexing (OFDM) is investigated. The two existing optical OFDM (O-OFDM) transmission schemes, asymmetrically clipped optical OFDM (ACO-OFDM) and direct-current-biased optical OFDM (DCO-OFDM), are studied. Time domain signal clipping generally results from direct current (DC) biasing and/or from physical limitations of the transmitter front-end. These include insufficient forward biasing and the maximum power driving limit of the emitter. The clipping noise can be modeled according to the Bussgang theorem and the central limit theorem (CLT) as attenuation of the data-carrying subcarriers at the receiver and addition of zero-mean complex-valued Gaussian noise. Analytical expressions for the attenuation factor and the clipping noise variance are determined in closed-form and employed in the derivation of the electrical signal-to-noise ratio (SNR). The validity of the model is verified through a Monte Carlo bit-error ratio (BER) simulation. Finally, the BER performance of ACO-OFDM with DCO-OFDM is compared for different clipping levels and multi-level quadrature amplitude modulation (M-QAM) schemes.

The sum rate of spectrum-sharing in decentralized and self-organizing wireless networks is investigated in this paper. Such networks pose the following two fundamental challenges: 1) cochannel interference and 2) the hidden node problem. For a slotted shared wireless medium, where resources are partitioned into time-frequency slots, time-multiplexed receiver initiated busy burst (BB) transmissions solve these problems by establishing an exclusion region around an active receiver by means of receiver feedback. The size of this exclusion region is controlled by an interference threshold that determines whether a user is allowed to transmit on a specific time-frequency resource unit. We propose a novel approach for setting the interference thresholds based on a heuristic derived for a two-link network. First, for two-links, the optimum threshold value is derived that maximizes the sum rate. Second, for multiple links, the new heuristic threshold that only relies on locally available information is derived. It is demonstrated via simulations that heuristic thresholding achieves superior sum rate compared to a fixed system-wide threshold. To complement simulation results, an analytical approach is developed to approximate the probability density function (pdf) of the sum of the interferers in BB setting with fixed threshold with a cumulant-based shifted log normal fitting method.

In this paper, the impact of double-sided signal clipping on optical wireless communication (OWC) systems employing asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) is investigated. Time domain signal clipping is introduced due to biasing issues or physical limitations of the front-ends. These include insufficient forward biasing of the emitter and the maximum driving power limit of the emitter and/or the detector. The clipping noise can be modeled according to the Bussgang theorem and the central limit theorem as attenuation of the subcarriers at the receiver and addition of zero-mean complex Gaussian noise. The attenuation factor and the clipping noise variance are determined semi-analytically and employed in the derivation of the signal-to-noise ratio (SNR) at the receiver. Finally, the theoretical SNR is verified through a bit-error ratio (BER) simulation.

In this paper, we introduce Dual-hop Spatial Modulation (Dh-SM). We look at the effect that Dh-SM has on the required signal to noise ratio (SNR) at the destination and how it can help alleviate the multi-hop burden. Initial bit-error-ratio (BER) results comparing the performance of Dh-SM with orthogonal decode-and-forward (DF) are presented where Dh-SM is shown to have up to a 10 dB SNR advantage.

Time switched transmit diversity (TSTD) system uses only one out of several transmit antennas at a time in order to exploit the benefit of transmit diversity while keeping the system simple by having only one RF chain. We show that while average rate of such a system remains similar to the capacity of the single transmit antenna, outage secrecy capacity is greatly improved. In particular, as the number of transmit antenna is increased or outage probability decreased, the gains over single antenna system improve significantly - gains of over 20 dB with respect to the single antenna system are achieved for 1% outage rate. Furthermore, the probability of existence of secrecy capacity is improved as well for cases when the main channel has higher SNR than the eavesdropper channel.

In shared wireless medium access, receiver initiated busy burst (BB) transmission mitigates the problem of co-channel interference. Receiver feedback allows potential transmitters to ascertain the amount of interference their transmission would cause to victim receivers in adjacent communication links. The BB concept mitigates excessive co-channel interference, by maintaining an exclusion region around any victim receiver: interferers within the region must refrain from accessing the shared wireless medium. In this paper, an analytical framework for interference modelling of the BB protocol is developed, via cumulant-based shifted log normal approximation of its probability density function (pdf). The interference pdf is then applied to derive the pdf of the signal-to-interference ratio (SIR).

This paper presents a novel approach for setting the thresholds for busy burst (BB) enabled interference avoidance in TDD (time division duplex) systems. One of the key issues in the BB concept is the appropriate choice of the threshold, which determines whether a user is allowed to transmit on a specific time-frequency resource unit. For a two-link network we derive the optimum threshold value that maximises the sum rate. Furthermore, for multiple links, a new heuristic threshold that only relies on locally available information is derived. It is demonstrated via simulations that the heuristic threshold provides superior sum rate than a fixed system-wide threshold.

Self-configuring, hierarchical, ad hoc, wireless networks are fast becoming the focus of research for spectral efficiency and energy efficiency reasons. Such networks can be considered as graphs where a node represents a transceiving unit and an edge represents a communication link between two nodes. In order to probabilistically analyse connectedness issues in such graphs, the concept of the star-node is introduced here, where a star-node is a node whose path loss to multiple nodes in its vicinity falls below a given threshold, i.e., it is capable of sustaining "healthy" communication links to multiple neighbours. Star-nodes are important in the context of ad hoc and sensor networks since nodes in a self-configuring network must be able to identify their neighbours, i.e., those nodes with which viable communication links can be established. The probability of finding such star-nodes is analytically derived for a uniform user distribution in a circular scenario. The theory is tested against Monte Carlo simulations and a very good match has been found.

In this paper the capacity of decentralized wireless networks is addressed. An exclusion region is introduced that protects active receivers from destructive interference of nearby transmitters. An exclusion range imposes an upper bound on the interference that a transmitter may cause to receivers of competing links. While an exclusion region avoids excessive interference and thus improves capacity per link, the spatial reuse in terms of concurrently served links is compromised. The resulting trade-off is elaborated by computer simulations, so to optimize the exclusion range as a function of the user density and maximum transmit power. We demonstrate that by an appropriately specified exclusion range, the network capacity is substantially enhanced. In this context, it has been found that the exclusion range that maximizes the system capacity does not vary greatly when changing the a priori user density. In addition, the trade-off between maximizing the system capacity and maintaining fairness is investigated.

Cognitive radio (CR) systems need to be able to adjust the transceiver characteristics in response to stimuli received from the radio environment. Therefore, monitoring the wireless signal in real-time for stimuli such as unexpected changes due to sporadic interference in radio frequency band of operation is at the core of such systems. In this paper, a method of detecting anomalies in a periodic signal by means of statistical analysis of its envelope is described. The proposed scheme makes use of the Kullback-Leibler divergence between probability distributions drawn from analogous segments of the periodic signal to detect anomalous events. Experiments conducted on real wireless signals suggest that the method described is simple, robust and effective for the analysis of periodic signals.

The purpose of this paper is to compare two interference avoidance techniques for time division duplex (TDD) wireless networks, viz.: a novel technique termed asymmetry balancing and the known zone division (ZD) principle. Both asymmetry balancing and ZD strive to reduce the same-entity interference (mobile station (MS)-to-MS and base station (BS)-to-BS) that occurs during crossed slots, i.e. slots which are simultaneously used for uplink (UL) in one cell and for downlink (DL) in a neighbouring cell. Asymmetry balancing eliminates crossed slots by synchronising the TDD switching point (SP) among cells. Cell-specific asymmetry demands are still maintained through cooperation among the entities in the network. ZD, on the other hand, reduces same-entity interference by decreasing transmission range. This study demonstrates that asymmetry balancing achieves more than 100% higher spectral efficiencies than ZD for the considered scenarios.

This paper proposes a novel approach to interference avoidance via inter-cell relaying in cellular OFDMA-TDD (orthogonal frequency division multiple access - time division duplex) systems. The proposed scheme, termed asymmetry balancing, is targeted towards next-generation cellular wireless systems which are envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing resolves the detrimental base station (BS)-to-BS interference problem inherent to TDD networks by synchronizing the TDD switching points (SPs) across cells. In order to maintain the flexibility of TDD in serving the asymmetry demands of individual cells, inter-cell relaying is employed. It is demonstrated that asymmetry balancing offers great flexibility in uplink (UL)- downlink (DL) resource allocation. In addition, results show that a spectral efficiency improvement of more than 100% can be obtained with respect to a case where the TDD SPs are adapted to the cell-specific demands.

Under the horizontal spectrum sharing scenario where two cognitive radios are able to find an unutilised resource and access to the resource is coordinated between them, it is shown in our earlier work that either single or simultaneous transmission at maximum power maximises system spectral efficiency. While in general suboptimal, sequential transmission, an average of two single transmissions, is also investigated as a more fair alternative to single transmission. In this paper, the system spectral efficiencies of simultaneous, single and sequential transmission schemes are compared for the 2-link scenario where the two communication pairs are chosen from uniformly distributed nodes on a disk. The simultaneous transmission scheme is shown to provide smaller expected system spectral efficiency for higher transmit power than sequential or single transmission schemes. Introducing additional interferers, however, significantly reduces the advantage of single and sequential schemes over simultaneous transmission. However, under the scenario of transmission to the closest neighbour, simultaneous transmission is shown to result in higher average system spectral efficiency than the other two schemes over the wide range of transmit powers.

This paper analyzes the system spectral efficiency of a 2-link ad hoc network. The analysis shows that there are exactly three operating points that maximize system capacity: either both links transmit with maximum power simultaneously; or one single link transmits with maximum power while the other is silent. The impact of the scheduling policy on the system spectral efficiency is also studied: simultaneous transmission or sequential access where the two links share the medium by dedicated time/frequency slots without causing interference. An exhaustive numerical search over a wide range of pathloss parameters shows that sequential transmission is superior to simultaneous transmission in about two third of the cases. Even when simultaneous transmission outperforms sequential transmission, the gains are typically not substantial. Furthermore, we show that in case of simultaneous transmission power control causes only marginal degradation in terms of system spectral efficiency, while transmitting with maximum power pays off for sequential transmission. This highlights the importance of the joint optimization of power and rate adaptation together with scheduling for power constraint ad hoc networks.

In this paper, the effect of variation in the spatial protection margin, is investigated for multihop wireless networks under the interference avoidance protocol model and compared to single-hop communication network. Under the protocol model, the interference is avoided by the application of the exclusion range concept. This means that a spatial protection region (or a circular exclusion region) is specified around all receiving nodes so that any node other than the intended transmitter is not allowed to reuse the same frequency resource within this region. It is demonstrated that for an asymptotically infinite coverage area, the spatial reuse efficiency for a multihop design increases proportionally with the number of multiple hops per link, and with the spatial protection margin. However, under a finite coverage area, the monotonic increase of spatial reuse efficiency does not remain completely valid. In order to analyze the performance of such a system, a relation for the system throughput is derived from the Shannon capacity equation. It is found that the system throughput attains a peak when the value of spatial protection margin is nearly unity. The exact value of spatial protection margin when the throughput reaches its maximum is found to be a monotonically increasing function of the number of multiple hops and the pathloss exponent.

A multihop ad hoc wireless network with an interference avoidance model is analyzed for a time division duplex (TDD) air-interface. In accordance with the non-interference protocol, an exclusion region is defined around every communicating receiver wherein no other node except the desired transmitter can transmit. In a network comprising finite coverage area, the position of the communicating nodes determine the number of simultaneous communicating pairs and hence the overall system throughput. A random data hopping technique for a time slot (TS) partitioned system is proposed in this paper. In this technique, the number of TS(s) in the TDMA frame is increased by reducing the duration of each TS. Then, the time slots over which the transmission pairs of the end-to-end link communicate are randomly assigned over the time frame. This randomness combined with a high TS granularity results in an increased system throughput of up to 31% as compared to a system with low TS granularity

A new telemetry method in oil well services uses compressional acoustic waves to transmit data along the drill string to the surface. Normal drilling operations produce in-band acoustic noise at intensities comparable to the transducer output while lossy propagation through the drill string and surface noise further degrade the signal. A single receiver system has a capacity of several hundreds bits per second. A two-receiver scheme exploits the fact that the surface noise source and the signal propagate in opposite directions to remove the downward propagating surface noise, which produces substantial increases in channel capacity. We use training with easily obtained data to determine how the signals need to be processed in a way that does not rely on knowing sensor placement or the acoustic model.

This paper is an initial investigation into the following question: can cooperation among sensors in a sensor network improve detection performance in a simple hypothesis test? We analyze a simple cooperative system using the Kullback-Leibler (KL) discrimination distance and a quantity known as the information transfer ratio which is a ratio of KL distances. We discover that, asymptotically, gain over a non-cooperative system depends on the conditional KL distance. We conclude with an illustrative example which demonstrates that cooperation not only significantly improves performance but can also degrade it.

A new method of wireless data telemetry in oil well services uses compressional acoustic waves to transmit data along the drill string. Coded wave trains are produced by an acoustic transducer, travel through the drill string and are subsequently decoded to recover the data. Normal drilling operations produce in-band acoustic noise at multiple sources at intensities comparable to the transducer output, while propagation through the long drill string further degrades the signal. We describe a theoretical channel model, and, based on this model, demonstrate that a single receiver system has a capacity of several hundred bits per second in such noisy drilling conditions. We analyze a two-receiver scheme that exploits the fact that the dominant noise source and the signal propagate in opposite directions. We show that with two receivers this dominant noise can be cancelled, which results in a significant improvement in capacity over the single receiver.

Information processing is performed when a system preserves aspects of the input related to what the input represents while it removes other aspects. To describe a system's information processing capability, input and output need to be compared in a way invariant to the way signals represent information, Kullback-Leibler distance, information-theoretic measure that reflects the data processing theorem, is calculated on the input and output separately and compared to obtain information transfer ratio. We consider the special case where input serves several parallel systems and show that this configuration has the capability to represent the input information without loss. We also derive bounds for asymptotic rates at which the loss decreases as more parallel systems are added and show that the rate depends on the input distribution.