In this paper we simulate and analyze the system performance of implementing two Hybrid Automatic Retransmission Request (HARQ) architectures for IEEE 802.16m system, one is a modified Type I HARQ architecture with adaptive modulation and coding (AMC) scheme and the other is the Chase Combining. In the simulation, the buffer size of HARQ has been set to certain limit and under the condition of having the packet error ratio (PER) limited by 10% then the selection of proper HARQ structure with suitable AMC scheme for IEEE 802.16m system has been proposed for mobile speeds at 3 km/hr, 80 km/hr or 350 km/hr and with a distance of 300m between the mobile station and its serving base station.

In this paper we propose a method of using a heuristic Genetic Algorithm (GA) to solve the Fast Fourier Transform subchannelization scheduling (FFTSS) problem in IEEE 802.16 broadband wireless access systems. In such a multi-user transmission system with quality of service (QoS) requirements, data from different users should be quickly scheduled and transmitted within the shortest transmission time period. In this paper, we propose a GA-based scheduler that will search the best configurations of the uplink and/or downlink sub-frames in order to obtain the optimal system throughput as well as quality of services. Due to the slow convergence of conventional GAs, we design a novel hardware architecture to accelerate the processing speed of GA which is used for scheduling the Down Link (DL) sub-frames. We then describe the procedure of using Field-Programmable Gate-Array (FPGA) to implement the designed hardware to verify the convergence of the algorithm. With this hardware implementation, the proposed method indeed helps us to construct a fast optimization tool to be applied in broadband wireless communication systems.

In Dense Wavelength Division Multiplexing (DWDM) technologies, the optimal packet scheduling is a common encounter issue in multiple channels network. NP-hard problem deals with finding a way to rearrange packets in multiple channels into a finite and rare channel. Genetic algorithm (GA) is one of the most efficient ways to solve this issue. We hope to find a better solution to our task through the GA characteristics of multiprocessor searching and survivor of the fittest. Therefore, a modified and achievable hardware architecture of GA is presented in this paper. This architecture can increase the schedule speed of packet scheduling also can promote the efficiency of DWDM in Optical Communication Networks.

In this paper we exploit a basic type of three-stage Distributed Bragg Reflector (DBR) laser that by adjusting its input driving currents in the tri-electrode to generate signals with wavelengths that are in the International Telecommunication Union (ITU)-Band. Many driving current combinations can generate the same ITU wavelength; we will consider in this paper the situation when the input currents are restricted within certain range and to find for all those input current combinations that generate output signals with wavelengths locating in the ITU defined wavelength range. And we will through simulations to determine which set of current combinations will generate the shortest switching time. We will also propose a new current control method, when we know in advance the signal will be switched to certain band, to determine the best current switching combinations that resulting in faster and shorter switching time than that of the conventional system structure which has the drawback that it has only one fixed current combinations for each channel.

Abstract:In this paper the implementation of hierarchicalmodulated pilot signals for carrier frequency drift estimation in high mobility multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system is introduced. Specifically for a hierarchical-modulated 64QAM-OFDM system in which three Layers with two bits in each Layer are defined from the constellation point and the carrier frequency drift estimation is facilitated from every Layer instead of using all six constellation bits to possibly simplify the design and reduce the time in the estimation process. The carrier frequency drift estimation by using only one Layer and the system performance at the receiver terminal by utilizing this Layer's estimated carrier frequency drift are simulated and compared for various high mobile speeds in Rayleigh fading channels.