Experimental and theoretical analysis of the optimum decision threshold for varying numbers of active users in a 2-D time-wavelength asynchronous O-CDMA system

Experimental demonstration of interference avoidance protocol (transmission scheduling) in O-CDMA networks

“…It should be noted that as each packet consists of several bits, the state of the link remains constant for a long duration. In [3], an IA based optical CDMA network was modeled using discrete event based packet simulator The simulator modeled multiple nodes on a broadcast shared medium optical O-CDMA LAN. The normalized offered load is the arrival rate (in packets/s) expressed as a fraction of the maximum possible arrival rate (in packets/s) of the network when it is used as a single channel network.…”

“…Optical code division multiple access (O-CDMA) is one of the feasible A critical limitation of O-CDMA networks is the reduction of throughput when many users are simultaneously trying to transmit over a common medium, thus producing extreme congestion at high network loads. In fact, networks can suffer from "congestion collapse" in which the network's throughput is degraded when traffic exceeds a threshold and it eventually approaches to zero under extremely high loads, i.e., when several users transmit simultaneously, their packets and hence their code-words overlap [3,4]. When the optical pulses in the codeword overlap, their power will be added, thus optical pulses from one codeword may be detected by other receivers tuned to other code-words.…”

Time-spreading wavelength-hopping OCDMA systems using parallel detection scheme

“…With the rapid progress of multimedia service, optical code division multiple access (OCDMA) techniques have been widely discussed for implementing digital subscriber loop [1]- [7]. As the twodimensional (2-D) optical CDMA systems can offer more advantages than one-dimensional systems in terms of carnality, multiple access interference (MAI), and number of simultaneous access users, thus the 2-D OCDMA systems have been extensively discussed for applications in local access links [2]- [7].…”

“…To implement 2-D OCDMA configurations, there are some practical optical devices to achieve the functionalities such as array waveguide grating (AWG), tunable delay line, fiber Bragg grating (FBG),…etc, [2] [3]. Several experiments have also demonstrated the performance of these systems [6] [7].…”

Trellis ternary line coding scheme for asynchronous optical CDMA systems

“…First of all, an OOK signaling scheme requires a dynamically adjustable receiving threshold. The optimal threshold for optical CDMA systems varies with the number of active users, and the use of a nonoptimal threshold may degrade the bit error rate (BER) by several orders of magnitude [10,11,23]. Receivers with dynamic thresholding schemes will increase the system complexity, and will even be intractable especially in high-speed transmission and bursty traffic situations.…”