Cooperative Channel Research Articles

A Novel based Cooperation and Joint Source Channel Transmission in Wireless Networks using LDPC

this paper, A Novel based Cooperation and joint source channel Transmission in wireless networks in this paper Low density parity check (LDPC) codes is linear different number of the forward error correcting codes, method of transmitting the number of messages over noisy transmission of a channel . Low density parity check (LDPC) codes are mainly used to minimize the outage probability. We summarize the methods based on the Read Solomon (RS) codes and the Progressive Edge Growth (PEG) algorithm in selection. The firest,we select a profile that describes that desire the desired number of columns of each weight and the desired number of rows of each weight. The symbols produced by the information source are given to the source encoder. These symbols cannot be transmitted directly. They are first concerted into digital form .The source encoder assign codeword's to the symbols for each discrete symbol there is an unique codeword. The transmission errors basically are of two types namely the random errors and burst errors. The errors that occurs in a purely random manner are known as random errprs.Where as the errors which occur in the form of bunches and hence which the not independent are known as the burst errors. Codes like binary BCH codes are useful in dealing with the random eror.Because of impulse noise, more than one corresponding data bits change their state simultaneously. The error introduced in the received word is called as burst error. The channel encoder and decoder is after converting the message (or) information signal in the form of binary sequence by source encoder. The signal is to transmit through channel. The communication channel adds some noise and interference to the signal being transmitted. Hence errors are introduced in the binary sequence received at the receiver end.

Cognitive Cooperative MAC With One Primary and Two Secondary Users: Achievable Rates and Optimal Power Control

We consider a three-user fading cognitive cooperative multiple access channel (MAC) with one primary and two secondary transmitters. We propose two encoding/decoding strategies with varying levels of cooperation, based on block Markov superposition encoding and backward decoding. The first is an overlay model, where the secondary users (SUs) aid the transmission of the primary user (PU) by causally decoding the PU message and forwarding it while also cooperating among each other. The second is an underlay model, where the SUs cooperate by decoding and forwarding each other's messages while treating the signal received from the PU as noise. In either case, the PU is guaranteed to operate at its maximum achievable single user rate. We characterize the achievable SU rate region for both models and maximize this region as a function of the transmit powers. The simulation results show that the SU rate region can be significantly enlarged, particularly using the overlay model.

Alternative relaying for cooperative multiple-access channels in wireless vehicular networks

In this paper, a novel spectrally efficient half-duplex cooperative transmission protocol is proposed for cooperative multiple-access channels in wireless vehicular networks, where multiple sources (vehicles) deliver messages to a common destination (roadside base station or roadside infrastructure) with the help of multiple decode-and-forward relays (roadside stations). The basic idea is to apply superposition coding at each transmitter in order to achieve the full diversity gain, where the linear zero-forcing detection is used at each relay to combat inter-relay interference. Compared to existing uplink cooperative protocols, the proposed scheme can exploit the cooperation involving both the relays and the sources. An achievable diversity-multiplexing trade-off is developed for the proposed transmission protocol. Even with strong inter-relay interference which has been ignored by many existing works, the proposed scheme can still approach the optimal multiple-input single-output upper bound. Numerical results have also been provided to demonstrate the performance of the proposed protocol.

On Cooperative Multiple Access Channels With Delayed CSI at Transmitters

We consider a cooperative two-user multiaccess channel in which the transmission is controlled by a random state. Both encoders transmit a common message and, one of the encoders also transmits an individual message. We study the capacity region of this communication model for different degrees of availability of the states at the encoders, causally or strictly causally. In the case in which the states are revealed causally to both encoders but not to the decoder we find an explicit characterization of the capacity region in the discrete memoryless case. In the case in which the states are revealed only strictly causally to both encoders, we establish inner and outer bounds on the capacity region. The outer bound is nontrivial, and has a relatively simple form. It has the advantage of incorporating only one auxiliary random variable. In particular, it suggests that there is none, or at best only little, to gain from having the encoder that transmits both messages also sending an individual description of the state to the receiver, in addition to the compressed version that is sent cooperatively with the other encoder. We then introduce a class of cooperative multiaccess channels with states known strictly causally at both encoders for which the inner and outer bounds agree, and so we characterize the capacity region for this class. In this class of channels, the state can be obtained as a deterministic function of the channel inputs and output. We also study the model in which the states are revealed, strictly causally, in an asymmetric manner, to only one encoder. Throughout this paper, we discuss a number of examples, and compute the capacity region of some of these examples. The results shed more light on the utility of delayed channel state information for increasing the capacity region of state-dependent cooperative multiaccess channels, and tie with recent progress in this framework.

Markovian‐based framework for cooperative channel selection in cognitive radio networks

The authors propose Markovian-based spectrum sensing policies in a cognitive radio system that leverages past sensing outcomes of several cooperating secondary users (SUs) to decide which channel (of primary users – PUs) should be sensed by each SU at a given time. These policies are based on a new finite-state channel model that captures the fading condition as well as the occupancy state for each primary channel. The multiuser extension of this model is useful when multiple spatially distributed SUs share their sensing outcomes. The proposed schemes allow the asynchronous sensing outcomes obtained by the SUs over different slots to be fused together and converted into a posteriori probabilities for the current states of the primary channels. As the detection threshold in a spectrum detector balances the trade-off between the false-alarm and miss probabilities for detecting primary signals in a single primary channel, a design parameter is introduced to allow the system designer to devise policies with different levels of aggressiveness. The authors evaluate the optimality and complexity of the proposed sensing policies and show that our schemes significantly increase secondary use of the spectrum and/or reduce interference with PUs compared to a random selection policy or a cooperative sensing policy based on a two-state channel model.

AKAP150-dependent cooperative TRPV4 channel gating is central to endothelium-dependent vasodilation and is disrupted in hypertension.

Endothelial cell dysfunction, characterized by a diminished response to endothelial cell-dependent vasodilators, is a hallmark of hypertension. TRPV4 channels play a major role in endothelial-dependent vasodilation, a function mediated by local Ca(2+) influx through clusters of functionally coupled TRPV4 channels rather than by a global increase in endothelial cell Ca(2+). We showed that stimulation of muscarinic acetylcholine receptors on endothelial cells of mouse arteries exclusively activated TRPV4 channels that were localized at myoendothelial projections (MEPs), specialized regions of endothelial cells that contact smooth muscle cells. Muscarinic receptor-mediated activation of TRPV4 depended on protein kinase C (PKC) and the PKC-anchoring protein AKAP150, which was concentrated at MEPs. Cooperative opening of clustered TRPV4 channels specifically amplified Ca(2+) influx at MEPs. Cooperativity of TRPV4 channels at non-MEP sites was much lower, and cooperativity at MEPs was greatly reduced by chelation of intracellular Ca(2+) or AKAP150 knockout, suggesting that Ca(2+) entering through adjacent channels underlies the AKAP150-dependent potentiation of TRPV4 activity. In a mouse model of angiotensin II-induced hypertension, MEP localization of AKAP150 was disrupted, muscarinic receptor stimulation did not activate TRPV4 channels, cooperativity among TRPV4 channels at MEPs was weaker, and vasodilation in response to muscarinic receptor stimulation was reduced. Thus, endothelial-dependent dilation of resistance arteries is enabled by MEP-localized AKAP150, which ensures the proximity of PKC to TRPV4 channels and the coupled channel gating necessary for efficient communication from endothelial to smooth muscle cells in arteries. Disruption of this molecular assembly may contribute to altered blood flow in hypertension.

Energy-Efficiency Analysis and Optimization for Virtual-MIMO Systems

Virtual multiple-input-multiple-output (MIMO) systems using multiple antennas at the transmitter and a single antenna at each of the receivers have recently emerged as an alternative to point-to-point MIMO systems. This paper investigates the relationship between energy efficiency (EE) and spectral efficiency (SE) for a virtual-MIMO system that has one destination and one relay using compress-and-forward (CF) cooperation. To capture the cost of cooperation, the power allocation (between the transmitter and the relay) and the bandwidth allocation (between the data and cooperation channels) are studied. This paper derives a tight upper bound for the overall system EE as a function of SE, which exhibits good accuracy for a wide range of SE values. The EE upper bound is used to formulate an EE optimization problem. Given a target SE, the optimal power and bandwidth allocation can be derived such that the overall EE is maximized. Results indicate that the EE performance of virtual-MIMO is sensitive to many factors, including resource-allocation schemes and channel characteristics. When an out-of-band cooperation channel is considered, the performance of virtual-MIMO is close to that of the MIMO case in terms of EE. Considering a shared-band cooperation channel, virtual-MIMO with optimal power and bandwidth allocation is more energy efficient than the noncooperation case under most SE values.

(China's Green Growth Strategy and Implications for Trade between Korea and China)

(China's Green Growth Strategy and Implications for Trade between Korea and China)

Rate Adaptation for Cooperative HARQ

We analyze the average throughput and the outage probability for relay-based incremental redundancy HARQ transmission over block fading channel. We focus on the effects of having an error-free multi-bit feedback channel instead of the single-bit ACK/NACK feedback used in conventional HARQ. This multi-bit feedback message provides the cooperating nodes with outdated channel state information (CSI) so that they can adapt their transmission rate. We discuss a network with M relay nodes and assume adaptive transmission rate for all the cooperating nodes. We describe the adaptation problem as a Markov Decision Process (MDP) and employ the Dynamic Programming (DP) for optimization. The numerical results obtained in the case of one relay transmission, indicate that significant throughput gains can be obtained when compared to non-adaptive, i.e, fixed-rate HARQ. Moreover, we study the performance limits of the system model by finding an upper bound of the throughput for the cooperative HARQ channel which is applicable to both adaptive and non-adaptive models. Finally, we analyze the discretization issues and conclude that only a small number of feedback bits is required by the adaptive system to outperform the conventional single-bit HARQ.

A temporal accessibility model for assessing the ability of search and rescue in Nansha Islands, South China Sea

Time is an indispensable means in accessibility expression and also an important index of the search and rescue (SAR) ability to a country. In this paper, a method for forecasting the location and probability of patrol vessel which is responsible for SAR on the sea is presented; and a temporal accessibility model for assessing the SAR ability of countries around South China Sea in Nansha is structured. In this study, 19 islands and cays in Nansha Islands are selected as rescue targets; eight ports in four countries around South China Sea are selected as SAR bases; patrol vessels belong to coast guard or maritime agency of countries around South China Sea whose displacement is over 1000 tons are selected as principal searchers and rescuers. Based on the density of ships passing the area and the distance from ports of each homeland, the distributions of patrol vessel which belongs to four countries around South China Sea are obtained. The SAR time of China, Vietnam, Malaysia and Philippines in Nansha were calculated based on the proposed method. The results indicated that due to the number of big patrol vessels, China Coast Guard is able to get to Nansha in minimum time, only half an hour for SAR; Vietnam gets second, one and a half hours; Malaysia gets third, 4.6 h; Philippines costs almost 7 h at the bottom of the list, because of the distance and the number of vessels. Taking consideration of the scattered distribution of islands, rocky coral reefs, bad weather and complex marine conditions, it is a very difficult job for SAR vessels. So it is necessary to set up several sub centers and shelters on appropriate islands or atolls in Nansha. And more importantly, how to enhance connection and coordination among countries around South China Sea, build harmonious and smooth SAR mechanisms or channels for cooperation, and improve the ability for solving emergency accidents in Nansha and even the whole South China Sea.

Superconductivity from weak repulsion in hexagonal lattice systems

We analyze the pairing instabilities for fermions on hexagonal lattices (both honeycomb and triangular ones) in a wide range of fermionic densities. We argue that for a generic doping in this range, superconductivity at weak coupling is of Kohn-Luttinger type, and, due to the presence of electronic interactions beyond on-site repulsion, is a threshold phenomenon, with superconductivity emerging only if the attraction generated by the Kohn-Luttinger mechanism exceeds the bare repulsion in some channel. For disconnected Fermi pockets, we predict that Kohn-Luttinger superconductivity, if it occurs, is likely to be $f$-wave. While the Kohn-Luttinger analysis is adequate over most of the doping range, a more sophisticated analysis is needed near Van Hove doping. We treat Van Hove doping using a parquet renormalization group, the equations for which we derive and analyze. Near this doping level, superconductivity is a universal phenomenon, arising from any choice of bare repulsive interactions. The strongest pairing instability is into a chiral $d-$wave state ($d+id$). At a truly weak coupling, the strongest competitor is a spin-density-wave instability, however, $d-$wave superconductivity still wins. Moreover, the feedback of the spin density fluctuations into the Cooper channel significantly enhances the critical temperature over the estimates of the Kohn Luttinger theory. We analyze renormalization group equations at stronger couplings and find that the main competitor to $d-$wave supoerconductivity away from weak coupling is actually ferromagnetism. We also discuss the effect of the edge fermions and show that they are unimportant in the asymptotic weak coupling limit, but may give rise to, e.g., a charge-density-wave order at moderate coupling strengths.

AKAP150‐dependent cooperative TRPV4 channel gating is central to endothelium‐dependent vasodilation and is disrupted in hypertension (678.10)

Endothelial cell (EC) dysfunction is a hallmark of hypertension. We recently discovered that local Ca2+ influx through clusters of functionally coupled TRPV4 channels (detected optically as “TRPV4 sparklets”) drives physiological vasodilation. Here, we show that stimulation of EC muscarinic receptors activated TRPV4 sparklets exclusively at discrete sites at myoendothelial projections (MEPs)—specialized regions of ECs that contact adjacent smooth muscle cells. This activation was dependent on protein kinase C (PKC) and was absent in mice lacking the PKC‐anchoring protein AKAP150 (A‐kinase anchoring protein 150), which was localized predominantly to MEPs. Cooperative gating of TRPV4 channels within a cluster amplified Ca2+ influx at MEPs by more than 2‐fold. This cooperativity was largely absent at non‐MEP sites and was virtually eliminated by chelation of intracellular Ca2+ or AKAP150 knockout, suggesting AKAP150‐dependent potentiation of TRPV4 activity by Ca2+ influx via adjacent channels. Notably, MEP‐localization of AKAP150 was disrupted in angiotensin II‐induced hypertension, leading to a complete loss of muscarinic activation of TRPV4 channels, much weaker coupling among TRPV4 channels at MEPs, and approximately an 80% reduction in carbachol‐induced vasodilation. Our results support the concept that endothelial‐dependent vasodilation of resistance arteries is enabled by MEP‐localized AKAP150, which ensures the proximity of PKC to TRPV4 channels and coupled channel gating necessary for efficient communication of the endothelium to the smooth muscle cells in arteries—a molecular configuration that is disrupted in hypertension.Grant Funding Source: Supported by HL044455, 1P01HL095488, R37DK053832, R01HL098243 to MTN

Cooperative gating and sensitivity of TRPV4 channels are regulated by distinct factors (1057.8)

TRPV4 (transient receptor vanilloid 4) sparklets represent Ca2+ influx through single TRPV4 channels (Sonkusare et.al., Science, 2012). In this study, we determined the differences in endothelial cell (EC) TRPV4 channel activity in mouse mesenteric (MA) and basilar (BA) arteries by recording TRPV4 sparklet activity in slit open, en face preparation, under physiological conditions of temperature and ionic solutions. TRPV4 channels in MAs and BAs exhibited a number of similarities, including a 4‐channel meta‐structure, the same quantal levels (0.19 ΔF/F0), and cooperative channel gating at myoendothelial projections (MEPs). However, an analysis of TRPV4 sparklets indicated that the channel open probability (Po) in response to TRPV4 agonist GSK1016790A (GSK101, 100 nM) is ~ 15‐fold lower in BAs than MAs. In agreement with the Ca2+ imaging results, the sensitivity of TRPV4 channels to the agonist GSK101, measured as currents in freshly isolated cells is shifted by ~10‐fold in cerebral arteries. The TRPV4 channel gating at MEPs was cooperative in both MAs and BAs, as indicated by similar coupling coefficients (~0.2). In MAs, the cooperative channel gating at the MEPs was dependent on a kinase anchoring protein 150 (AKAP150). Notably, AKAP150 exhibited similar clustering at MEPs in MAs and BAs. These results suggest that cooperativity and agonist sensitivity of TRPV4 channels are functionally separable.Grant Funding Source: HL044455, 1P01HL095488, R37DK053832, R01HL098243 to MTN

Superconductivity in the two-dimensionalt-t′-Hubbard model

Using a recently developed renormalization group method for fermionic superfluids, we determine conditions for d-wave superconductivity in the two-dimensional Hubbard model at moderate interaction strength, and we compute the pairing gap in the superconducting regime. A pairing instability signaled by a divergent flow in the Cooper channel leads to a superconducting state in all studied cases. The next-to-nearest neighbor hopping $t'$ plays a crucial role in the competition between antiferromagnetism and superconductivity. A sizable $t'$ is necessary to obtain a sizable pairing gap.

Establishing the Dominant Milk Marketing Channel in Nyandarua District, Kenya: A Cumulative Density Function Approach

This paper uses data from a survey of 186 dairy households in two divisional administrative zones in the Kenya highlands to establish the dominant milk marketing channel based on net returns. Cumulative density function results show that, the private channel dominates over all the other channels except at the 0.8 probability level of choice where the cooperative channel dominates overall. Although most smallholder farmers in Kenya market milk through the traditional channel, the net returns that would accrue from their enterprise if they used the traditional and cooperative channels is still considerably higher. It is however apparent that the traditional channel is being replaced, albeit slowly, giving rise to the need of a policy to breach the quality gap between the traditional and the modern channels by making popular training and certification programs for small scale milk traders and processors.

China's Green Growth Strategy and Implications for Trade between Korea and China

China's Green Growth Strategy and Implications for Trade between Korea and China

CRP-CMAC: A Priority-Differentiated Cooperative MAC Protocol with Contention Resolution for Multihop Wireless Networks

To improve the cooperative efficiency of node cooperation and multiple access performance for multihop wireless networks, a priority-differentiated cooperative medium access control protocol with contention resolution (CRP-CMAC) is proposed. In the protocol, the helper selection process is divided into the priority differentiation phase and the contention resolution phase for the helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase of the same priority helpers consists of k round contention resolution procedures. The helpers that had sent the first busy tone and are now sending the longest busy tone can continue to the next round, and then the other helpers that sense the busy tone withdraw from the contention. Therefore, it can select the unique best helper from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted to make the high data rate helper with packet to send transmit its data packets to its recipient without reservation. It can significantly decrease the reservation overhead and effectively improve the cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of CRP-CMAC is 74%, 36.1% and 15% higher than those of the 802.11 DCF, CoopMACA and 2rcMAC protocols in a wireless local area network (WLAN) environment, and 82.6%, 37.6% and 46.3% higher in an ad hoc network environment, respectively.

Enhancement of critical temperatures in disordered bipartite lattices

We study the strong enhancement, induced by random hopping, of the critical temperatures characterizing the transitions to superconductivity, charge-density wave, and antiferromagnetism, which can occur in bipartite lattice models at half filling, like graphene, by means of an extended Finkel'stein nonlinear $\ensuremath{\sigma}$-model renormalization group approach. We show that if Cooper channel interaction dominates, superconducting critical temperature can be enhanced at will, since superconductivity cannot be broken by entering any Anderson insulating phase. If instead, staggered interactions are relevant, antiferromagnetic order is generated by disorder at a temperature well above that expected for a clean system.

A rapid cooperation-differentiated medium access control protocol with packet piggyback for multihop wireless networks

Abstract To improve the efficiency of node cooperation and multiple access performance in multihop wireless networks, a rapid cooperation-differentiated medium access control (MAC) protocol is proposed. In the protocol, the helper selection process is divided into a priority differentiation phase and contention resolution phase for helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase for the same priority helpers can use any existing collision resolution scheme, such as the k-round elimination contention scheme. Helpers sending a busy tone first can proceed to the next round, while others, sensing the busy tone, subsequently withdraw from contention. Therefore, a unique optimal helper is selected from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted, which allows a high data rate helper with its own data packets, to transmit these to their recipient without reservation. This significantly decreases the reservation overhead and effectively improves cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of the proposed protocol is 39.6% and 9.6% higher than those of the cooperative MAC-aggregation (CoopMACA) and instantaneous relay-based cooperative MAC protocols, respectively, in a wireless local area network environment, and 40.8% and 31.9% higher, respectively, in an ad hoc network environment.

Ülevaade Soome palkehituse ajaloost

This article takes a look at the history of Finnish log construction and log architecture. Logs have been used as a building material in Finland for as long as the country has been inhabited. The modern corner-notching technique arrived in Finland in the late Iron Age (600−800 AD) from the east, leading to a building type that survived until the 20th century.During the era of church builders (1620−1810), log construction achieved its highest form: the churches built during this period represent Finnish log architecture of the highest quality. Church builders had an excellent command of log construction techniques and knew logs as a building material extremely well, which allowed them to use the forms of the buildings and the decorative elements for the architectonic expression characteristic of logs.Church architecture adapted to other Western style trends in the 19th century. Although outstanding churches were still being built at the time, their technical developments did not lead to further developments in log construction techniques.The architecture of the Finnish artists’ (Akseli Gallen-Kallela et al) villas built in the late 19th century relied on the expressive power of logs, corner joints and handicraft. The walls were stylistically rough-hewn and there was no weatherboarding. The corner notches played a central architectural role and decorative elements were borrowed from Finnish log construction heritage. Artists’ villas have a unique position in Finnish architecture: for the first time, logs consciously emerged as a main architectural element. Contemporary industrial log construction began to develop in the 1950s. Product quality has improved considerably since then as a result of development work, and the prefabricated log has become a generally accepted building material. However, these logs no longer have the essence of a natural material and they have therefore lost their power of expression. The emphasis of industrial log construction and architecture is predominantly on manufacturing as economically as possible using existing production technology. In the 2000s industrial log construction finally started losing its romantic and historical burden and finding its own architectural expression.Contemporary hand-crafted log construction can be regarded as a continuation of the vernacular log construction tradition. Training in hand-crafted log construction has been organised since the late 1970s. The level of training has been highly uneven and the lack of a connection between such training and construction education has been one of its problems. The future of log construction is associated with product quality and energy efficiency. Development work and opening up new cooperation channels is important for the future of log construction as a craft.