Partial Information Relaying with Multi-Layered Superposition Coding

The ability to decode new words of varying degrees of orthographic-phonological mapping is an important word recognition skill across languages. Chinese characters represent three types of phonetic regularity: regular, semi-regular, and irregular depending on the degree of reliability of the pronunciation information provided by the phonetic component. This study investigated whether adult non-native Chinese learners can use partial phonological information encoded in semi-regular characters to learn the pronunciations of new characters. A total of 55 college students, enrolled in an intensive Chinese program with varying proficiency levels, were taught the pronunciations of 18 novel compound characters of three phonetic regularity types over three trials. Non-native Chinese learners of advanced and intermediate levels learned the pronunciations of regular characters (initial-same and final-same), which contain full information about pronunciation, and semi-regular characters (initial-different, final-same), which contain partial information about pronunciation, significantly better than irregular characters (initial-different and final-different), which contain misleading pronunciation information. The performance difference between semi-regular and irregular characters decreased over trials. Novice students demonstrated limited ability in using partial information to learn to pronounce characters compared to intermediate and advanced students. These results provide implications for effective character instruction for adult learners of Chinese with varying Chinese proficiency levels.

This paper presents an exhaustive study on the use of one-relay and two-relay cooperative communication schemes and 2-hop communication scheme for improving the energy efficiency and reliability of ultra-wideband based wireless body area networks (UWB WBANs). Various investigations have been performed to study the impact of the parameters like packet size, hop distance, transmit power and channel error rate on the energy efficiency and reliability. An optimal packet size is obtained for the maximization of energy efficiency for both on-body communication and in-body communication. The analytical and simulation results show enhanced reliability with cooperative communication than direct communication and 2-hop communication, for all values of source to destination distances. The results also depict a threshold behaviour for energy efficiency which separates the hoplength for direct transmission from the hoplength where cooperation and 2-hop communication will be useful. The simulation results reveal that if the channel conditions are poor, when the source to destination distance is larger than the threshold value, 2-hop communication gives higher energy efficiency compared with direct and cooperative communications.

In this work, we study a dynamic portfolio optimization problem related to pairs trading, which is an investment strategy that matches a long position in one security with a short position in another security with similar characteristics. The relationship between pairs, called a spread, is modeled by a Gaussian mean-reverting process whose drift rate is modulated by an unobservable continuous-time, finite-state Markov chain. Using the classical stochastic filtering theory, we reduce this problem with partial information to an equivalent one with full information and solve it for the logarithmic utility function, where the terminal wealth is penalized by the riskiness of the portfolio according to the realized volatility of the wealth process. We characterize optimal dollar-neutral strategies as well as optimal value functions under full and partial information and show that the certainty equivalence principle holds for the optimal portfolio strategy. Finally, we provide a numerical analysis for a toy example with a two-state Markov chain.

We consider the problem of assessing and mitigating fire sales risk for banks under partial information. Using data from the European Banking Authority's stress tests, we consider the matrix of asset holdings of different banks. We first analyse fire sales risk under both full and partial information using different matrix reconstruction methods. We then investigate how well some policy interventions aimed at mitigating fire sales risk perform if they are applied based on only partial information. We find that even under partial information, using suitable network reconstruction methods to decide on policy interventions can significantly mitigate risk from fire sales. Furthermore, we show that some interventions based on reconstructed networks significantly outperform ad hoc methods that decide on interventions only based on the size of an institution and do not account for overlapping portfolios.

Optimal experimental designs for partial likelihood information

Inflation Targeting and Nominal Income Growth Targeting: When and Why are They Suboptimal?

The equilibrium joining probabilities for a single primary user (PU) and secondary users (SUs) in the case of no queue length information, and the equilibrium Nash balance thresholds for PU and SUs to join the system in the cases of partial queue length information and full queue length information observed by PU and SUs are investigated in a cognitive radio system. PU stochastically sends PU requests and each SU is assumed to only carry one SU request. Whenever a PU (or an SU) request is completed, a reward is issued to the PU (or the SU). However, a holding cost is charged also for each SU and PU during their average sojourn time in the system respectively. Both of PU requests and SU requests are selfish in this research and their objectives are to maximize their own benefit. Our major conclusion includes a threshold probability value for PU (or SU) to join the system identified for the case of no queue length information, a Nash balance PU (SU) threshold value is determined for the case of partial queue length information; and the multi-dimensional Nash balance threshold is established for the case of full queue length information. These Nash balance threshold integer values depend on not only the Nash Balance PU-threshold value but also the specific number of SU requests in the system at that arriving time. In addition, we discuss the sensibility of input parameters to the obtained equilibrium joining probabilities and Nash balance thresholds. We mathematically verify that SUs' equilibrium joining probability does not necessarily increase with the transmission rate of PU in no queue length information case and observe numerically that the Nash balance thresholds adopted by an arriving SU are fickle with the change of PU's transmission rate in both of partial and full queue length information cases. Our results and observations provide a guideline and important managerial insights in making decisions with strategic users in the design of CRNs.

Cooperation provides an efficient form of diversity in wireless communications. In this paper we consider a coded cooperative system where the source and the relays may have multiple antennas. We describe two simple algorithms for choosing a good relay: blind-selection-algorithm and informed-selection-algorithm. These algorithms only require the knowledge of average received signal to noise ratios at the destination. Simulation results, carried out for a cellular system, show that both algorithms result in substantial improvement over direct transmission and random choice of relay in the cell and provide error rates close to best relay performance.

Coordination and Free-Riding Problems in Blood Donations

This work is concerned with the synthesis of nonlinear controllers for plants where full state information is not available. By means of the equivalent Takagi-Sugeno form of the nonlinear model, conditions were found that allow a parallel distributed compensation of the model to be constructed only with partial information of the state and no need of an observer. These conditions are expressed in terms of linear matrix inequalities which are efficiently solved by convex optimization techniques in commercially available software. The proposed approach is successfully applied to the stabilization of a twin rotor MIMO system and compared with another partial-information technique.

Recently, the cooperative communication has been explored more and more as an impressing technique to combat the effects of channel fading and to reduce the energy consumption in wireless networks. However, the impact of cooperative communications on transmission rate has not been well-addressed yet. In this paper, we provide an analytical framework for transmission rate enhancement issue in wireless communications. For a given transmit power and a desired probability of success, we investigate how much average transmission rate can be increased by cooperative communications. Three transmission models have been compared: the direct transmission, the cooperative transmission without maximal ratio combiner (MRC), and cooperative transmission with MRC. The analytical and numerical results show that around 1 - 3b/s/Hz transmission rate can be improved when the source-destination distance is 20m. We also reveal that the MRC scheme is not always beneficial, especially when the source-destination distance is short and the relay is close to the destination.

This article outlines one way to address these problems by using the notion of cooperation between wireless nodes. In cooperative communications, multiple nodes in a wireless network work together to form a virtual antenna array. Using cooperation, it is possible to exploit the spatial diversity of the traditional MIMO techniques without each node necessarily having multiple antennas. Multihop networks use some form of cooperation by enabling intermediate nodes to forward the message from source to destination. However, cooperative communication techniques described in this article are fundamentally different in that the relaying nodes can forward the information fully or in part. Also the destination receives multiple versions of the message from the source, and one or more relays and combines these to obtain a more reliable estimate of the transmitted signal as well as higher data rates. The main advantages of cooperative communications are presented.

The innovation of Wireless communication has been developed very fast in order to improve the performance of communication systems. Especially, a concept of Multiple Input Multiple Output (MIMO) is purposed to fulfill a high data rate service such as high quality video conference. However, a limitation in size and power of mobile device in the latest version of cellular system i.e. third Generation (3G) and fourth Generation (4G) causes difficulty to implement MIMO on mobile unit. Hence, Cooperative communication has been created to operate as a virtual MIMO in modern wireless communication. The objective of this paper, the performance analysis of Hybrid Decode-Amplify and Forward (HDAF) Cooperative communication using Orthogonal Space-Time Block Code (OSTBC) is derived in term of Symbol Error Rate (SER) against Signal-to-Noise Ratio (SNR) when the system applies different type of modulation techniques. Additionally, the error performance is derived base on Moment Generating Function (MGF) of the Rayleigh fading channel. We only focus on the downlink direction. Assuming that multiple antennas can be equipped into a transmitter which operates as base station in cellular system, mobile unit can be equipped with only single antenna due to the size limitation which operates as relays and destination. Moreover, the receiver uses Maximum Ratio Combining (MRC) to receive the transmitted signal.

The fundamental idea of cooperative communications in wireless networks originates from the design of multiple-antenna systems. In multiple-antenna systems, communicating terminals are equipped with multiple antennas to mitigate the effects of multipath fading and optimise the communication rate in the network. Wireless communication nodes like cellular phones and sensor nodes have size restrictions, power supply limitations and are only able to accommodate a limited level of complexity. It is thus unfeasible to equip them with multiple antennas. The effects of multipath fading are critical in cellular, ad hoc and sensor networks because the physical deployment of communicating nodes makes them susceptible to interference. It is imperative to adopt a mechanism to combat fading in such networks. The broadcast nature of the wireless medium makes it easy for the communicating nodes to hear each other. They can share their physical resources specifically their single antennas, thereby creating a virtual multiple-antenna array. Cooperative communications is a concept where several single-antenna nodes cooperate and form a distributed multiple-antenna system which combats multipath fading. In recent years, cooperative communications have received extensive world-wide attention and significant advances in both research and applications have been achieved.

Although multiple-input multiple-output antenna transmission is advantageous on orthogonal frequency division multiple access system, it may not be possible that practical systems have more than two antennas because of its size and cost. Therefore, cooperative communication has been recently studied as a way to solve this problem in a wireless environment. However, if cooperative communication system selects relay in a bad channel environment between source and relay, the relay has a bad effect on the bit error ratio performance. Thus, selective relay technique is proposed in this paper. The proposed system can select the best relay which has the best SNR between source and relay among the candidates. The proposed system also easily finds the best relay with low complexity.