Packet Squeezing of Random Access with 5G Real-Time Services for Internet of Things

Wireless Personal Communications - Random Access techniques are many, most of which are designed for a limited number of mobile nodes. However, in a 5G Internet of Things environment, the design of...     

Adaptive multilevel method for the air bearing problem in hard disk drives

An adaptive grid-generating algorithm is constructed and integrated with the multigrid method to form a numerical scheme that suits slider air-bearing simulation of hard disk drives. The relative truncation error, a by-product of the multigrid method, is used in grid adaptation criteria. Finer meshes are constructed over nodes of the current finest grid where the relative truncation error exceeds a predetermined tolerance. The union of these finer meshes forms a new level of grid, which may not cover the entire domain of the coarse grid underneath. The final grid system thus constructed is composed of levels of uniform grids with decreasing mesh sizes. This composite grid structure incorporates with numerical resolution as needed and efficiency of computation. A shaped rail, negative pressure slider is used to demonstrate the effectiveness of this numerical scheme. Compared with the traditional multigrid method, the proposed adaptive multilevel method can significantly reduce the computation work for achieving the same level of accuracy.     

A Novel Complex Orthogonal Design for Space–Time Coding in Sensor Networks

In this paper, we propose a complex orthogonal design based on the theory of Finite projective plane. As most of the orthogonal designs incur low ratio of time diversity, the proposed complex orthogonal design has a relatively high ratio of time diversity. In addition, the proposed scheme has the following characteristics: (1) full spatial diversity (2) low rate (3) linear processing. We compare the proposed scheme with another complex design to show the tradeoffs. The proposed scheme can be of use for certain applications such as sensor networks and deep space exploration where there might be an imposed limit on the peak transmit power.     

Patching Based Extra Short Packet Forward Error Control Coding for Ultra-Reliable Low Latency Communications (URLLC) in 5G

Wireless Personal Communications - With advancement in the communication technology, need of faster data transfer and cheaper alternates of existing fiber structure is highly required. Free Space...     

Orthogonal code design for quasi-synchronous CDMA

A new code design method for quasi-synchronous CDMA is proposed. The proposed scheme, based on the theory of finite projective planes, has the following advantages: orthogonality; low cross-correlation for both the quasi-synchronous mode and asynchronous mode; and low auto-correlation. Numerical autocorrelation and cross-correlation results are provided for both the proposed code design and the Walsh functions     

Optimal time-hopping scheme for CDMA air interface in broad-bandwireless systems

Time-hopping techniques have been applied in direct sequence code division multiple access (DS-CDMA) to reduce the harmful effects of a sudden power surge in the received signals. The conventional approaches may result in either nonuniform distribution of transmitting users among time slots or uneven interference from the dominant interferers. For both cases, the bit-error rate (BER) increases significantly for the users suffering the worst case condition. We propose an optimal time-hopping scheme based on the theory of finite projective planes for DS-CDMA to distribute interference evenly among participating users. The performance evaluation is divided into four parts. We demonstrate that both the average BER, probability of outage, and bandwidth efficiency can be improved by using the proposed time hopping scheme in comparison to other time-hopping schemes, such as the fixed allocation scheme and random selection scheme for various modulation methods including frequency shift keying-coherent demodulation (FSK-CD), differential phase shift keying (DPSK), binary phase shift keying (BPSK), and FSK with noncoherent demodulation (FSK-NCD). We compare the proposed time hopping scheme with nontime-hopping DS-CDMA with identical signal bandwidth. We then prove that the proposed scheme is optimal in minimizing interference     

A Novel Analytical Modeling of Composite Cognitive Capability with an Overlay Sensing Approach

Cognitive radios are promising solutions to the problem of overcrowded spectrum. The cognitive capability is the key technology that enables the secondary users to use licensed spectrum in a dynamic manner that the spectrum of the primary users are as unaffected as possible. But the metrics for composite cognitive capability are required in time in order to capture the temporal, spectral, and spatial variations (“spectrum holes”) simultaneously with cognitive signal strength under sophisticated cognitive radio environments. In this paper, in order to evaluate the spectrum awareness effectively, a novel analytical modeling of composite cognitive capability with an overlay sensing approach is proposed. A cognitive scenario with elliptically spatial variations is assumed, which consists of primary units and cognitive radio units (CRUs) with concurrent temporal and spectral scanning schemes. Moreover, a metric of spectrum holes ratio (SHR) is defined to evaluate the composite cognitive capability. Furthermore, CRUs can also detect transmission signals strength and “assist” receiving signal through a tone-assisted relaying signal to enhance system performance and reach lower symbol error probability with a specific tone-to-signal ratio above signal-to-noise ratio decision thresholds under a constant elliptic SHR locus.     

A feasible method to implement optimum CIR-balanced power control in CDMA cellular mobile systems

Power control is essential in the design of direct-sequence code-division multiple-access (DS-CDMA) techniques. Optimum power-control (OPC) methods with carrier-to-interference ratio (CIR) balancing have been formulated as eigenvalue problems for frequency-division/time-division multiple-access (FDMA/TDMA) cellular systems. For the CDMA cellular system, its OPC was also formulated as an eigenvalue problem based on a large link-gain matrix. The OPCs with CIR-balancing were realized by solving eigenvalue problems of link-gain matrices. We reformulate the CIR-balanced OPC in CDMA cellular systems by benefiting from the power constraints as an eigenvalue problem based on a novel link-gain matrix. For a feasible implementation, a two-level hierarchical power-control structure is proposed to carry out the eigendecomposition which is required for the CIR-balanced OPC. Shortages of unbalanced CIR and global outage are two common issues in CIR-balanced power control. To tackle these two problems, a simple linear prediction method and an adaptive on-off strategy are proposed. Furthermore, because of the capacity limitation of wireless communications, a differential pulse code modulation scheme is presented to reduce the number of bits required for the transmission of command words in the two-level hierarchical power-control structure.     

Evaluations of Novel Waveform Coding Signals Based on Finite Projective Plane

The most popular and representative classic waveform codes are referred to as orthogonal, bi-orthogonal, simplex, and etc, but the choice of waveform codes is essentially identical in error performance and cross correlation characteristic. Though bi-orthogonal coding requires half the bandwidth of the others, such coding scheme is attractive only when large bandwidth is available. In this paper, a novel finite projective plane (FPP) based waveform coding scheme is proposed, which is with similar error performance and cross correlation. Nevertheless, the bandwidth requirement will grow in a quadratic way, but not in an exponential way with the values of message bit numbers (k). The proposed scheme takes obvious advantages over the bi-orthogonal scheme when k 6.