SIR performance evaluation of a multirate OFFH-CDMA system

This paper investigates the signal-to-interference ratio (SIR) performance of a single chip rate variable processing gain optical fast frequency hopping CDMA (OFFH-CDMA) system, using direct detection. A fiber-optic CDMA communication network is considered. A system model that allows multirate transmission is presented. In addition, the SIR is derived. A comparison between the exact value of the SIR and the approximation one assuming random sequences is also discussed     

An effective segmentation method for iris recognition based on fuzzy logic using visible feature points

Multimedia Tools and Applications - In this paper, the edge corners (ECs) are proposed as new visible feature points located at the edges of visible iris features such as crypts, pigment spots and...     

Optical S-ALOHA/CDMA systems for multirate applications: architecture, performance evaluation, and system stability

In this paper, a new multirate optical network based on a hybrid slotted-ALOHA (S-ALOHA)/overlapped code division multiple access (O-CDMA) system is proposed as an effective way of integrating multiclass traffic. The key issue in this proposal is to exploit the potential of the optical O-CDMA using fiber Bragg gratings when jointly used with the S-ALOHA protocol in a link layer. The newly proposed system is modeled using a general Markov chain from which both the system throughput and the average packet delay are derived. The system stability passing through a general finite user model is also envisaged. The system is then compared to the classical S-ALOHA/variable processing gain (VPG) CDMA system. Numerical results show that the proposed system outperforms the latter one, especially at high transmission rates. In addition, stability measures demonstrate that the overlapped system tends to be more stable than the VPG system.     

Multirate optical fast frequency hopping CDMA system using powercontrol

This paper addresses the problem of real-time multimedia transmission in fiber-optic networks using code division multiple access (CDMA). We present a multirate optical fast frequency hopping CDMA (OFFH-CDMA) system architecture using fiber Bragg gratings (FBGs). In addition, we argue that, in multimedia applications, different services have different quality of service (QoS) requirements; hence, the user only needs to use the minimum required power to transmit the signal, such that the required signal-to-interference ratio (SIR) is met. We show that a variable bit rate optical communication system with variable QoS can be implemented by way of power control with great efficiency. Present-day multirate optical CDMA systems concentrate on finding the code structure that supports a variable rate system, neglecting the importance of the transmission power of active users on the multiple access interference (MAI) and, therefore, on the system capacity. We assign different power levels to each rate through a power control algorithm using variable optical attenuators, which minimizes the interference and, at the same time, provides variable QoS constraints for different traffic types. Although we are using a code family that preserves good correlation properties between codes of different lengths, simulations show a great improvement in the system capacity when power control is used     

On the cutoff rates of a multiclass OFFH-CDMA system

We consider an optical code-division multiple-access (OCDMA) network that supports multiple traffic classes. Each class has different processing gain and performance requirements. In this paper, a new method is proposed to analyze the cutoff rates for a multiclass, multirate optical frequency-hopping code-division multiple-access system using fiber Bragg gratings and direct detection. This approach exploits the linear structure of passive OCDMA systems and the nominal time required to accomplish the encoding-decoding operations in such systems. A system model is presented and analyzed, based on a newly introduced bit-overlap procedure. An expression for the cutoff rate of a single-class system is derived. In addition, for a multiclass system, an expression that relates the cutoff rates of the offered classes is introduced, and it is called the service curve. It is shown that for a required quality of service guarantee, a number of active users, and a given probability of hit, the system's data rate can be increased beyond the nominal limit imposed by the physical constraint of the encoder-decoder set.     

Hybrid minutiae and edge corners feature points for increased fingerprint recognition performance

Pattern Analysis and Applications - In general, most fingerprint recognition systems are based on the minutiae feature points. When matching two fingerprint images, the goal in most recognition...     

Optimal Resource Allocation Scheme in a Multirate Overlapped Optical CDMA System

This paper addresses the problem of resource allocation in a multiservice optical network based on an overlapped code-division-multiple-access system. A joint transmission power and overlapping coefficient (transmission rate) allocation strategy is provided via the solution of a constrained convex quadratic optimization problem. The solution of this problem maximizes the aggregate throughput subject to peak laser transmission power constraints. The optimization problem is solved in a closed form, and the resource allocation strategy is simple to implement in an optical network. Simulation results are presented, showing a total agreement between the derived analytical solution and the one obtained using a numerical search method. In addition, analytical and numerical results show that the proposed resource allocation strategy can offer substantial improvement in the system throughput.