Temperature dependence of turn-on time delay of semiconductor laser diode: Theoretical analysis

2010 ◽  
Vol 18 (4) ◽  
Author(s):  
M.S. Ab Rahman ◽  
M.R. Hassan
Keyword(s):  
Time Delay ◽  
Temperature Dependence ◽  
Semiconductor Laser ◽  
Laser Diode ◽  
Communication Systems ◽  
Recombination Coefficient ◽  
Turn On ◽  
Proposed Model ◽  
Wide Range ◽  
Dc Bias

AbstractTemperature dependence of the turn-on time delay (ton) of uncooled semiconductor laser diodes biased below and above threshold is analyzed in presence of data pattern effect. We show that even when the laser is biased at or slightly above threshold, the increase in temperature of operation will lead to increase in the threshold carrier (Nth) and consequently the laser diode will be biased below the threshold again and a significant value of ton will be produced. Thus, knowledge about a value of dc-bias current required to achieve zero ton within wide range of temperature degrees is important when considering uncooled laser diode in high-speed optical communication systems. The temperature dependence of ton is calculated according to the temperature dependence of Nth and Auger recombination coefficient (C) and not by the well-know exponentional relationship of threshold current with temperature. The temperature dependence of Nth is calculated according to the temperature dependence of laser cavity parameters. Advanced analytical model is derived in term of carrier density, recombination coefficients and the injection current (Iinj). The validity of proposed model is confirmed by a numerical method. In addition, approximated models are included where under specified assumptions the proposed model reduces to the well-known approximate models of ton. According to our typical values and at a specified value of modulation current, the dc-bias one (Iib) should be increased from Iib = Ith to Iib ≈ 1.25 and 1.5Ith in order to achieve approximately zero ton when the temperature increases from 25°C to 55°C and 85°C, respectively.

scholarly journals Analytical Modelling of a New Handover Algorithm to Improve Allocation of Resources in Highly Mobile Environments

2016 ◽  
Vol 11 (6) ◽  
pp. 789 ◽  
Author(s):  
Yonal Kirsal
Keyword(s):  
Communication Systems ◽  
High Speed ◽  
Model Simulation ◽  
Blocking Probability ◽  
Mobile User ◽  
Mobile Systems ◽  
Mobile Users ◽  
Mobile Environments ◽  
Proposed Model ◽  
Wide Range

Wireless and mobile communication systems have evolved considerably in recent years. Seamless mobility is one of the main challenges facing mobile users in wireless and mobile systems. However, highly mobile users lead to a high number of handover failures and unnecessary handovers due to the limited resources and coverage limitations with a high mobile speed. The traditional handover models are unable to cope with high mobile users in such environments. This paper proposes, an intelligent handover decision approach to minimize the probability of handover failures and unnecessary handovers whilst maximizing the usage of resources in highly mobile environments. The proposed approach is based on modelling the system using a Markov chain to enhance the system’s performance in terms of blocking probability, mean queue length and transmission delay. The results are compared with the traditional handover model. Simulation is also employed to validate the accuracy of the proposed model. Numerical results have shown that the proposed method outperforms the traditional algorithm over a wide range of handover failures and significantly reduced the number of such failures and unnecessary handovers. The results of this study show that quality if service (QoS) measures of such systems can be evaluated efficiently and accurately using the proposed analytical model. However, the performance results have also shown that it is still necessary to explore an effective model for operational spaces. In addition, the proposed model can also be adapted to various types of networks considering the high speed of the mobile user and the radius of the network.

scholarly journals A proposed model for frequency tuned antennas used in mobile communication systems

2021 ◽  
Vol 11 (2) ◽  
pp. 1367
Author(s):  
Amin H. Al Ka'bi ◽  
Magid M. Rady
Keyword(s):  
Resonant Frequency ◽  
Mobile Devices ◽  
Communication Systems ◽  
Research Work ◽  
Electromagnetic Properties ◽  
Wireless Communication Systems ◽  
Significant Shift ◽  
Ferrite Material ◽  
Proposed Model ◽  
Wide Range

The antenna is considered as one of the most fundamental elements in wireless communication systems, especially in mobile devices. Desirable specifications of antennas include covering wide range of operating frequencies, while maintaining high quality of system performance over the whole range of operating frequencies. Therefore, the ability of tuning the resonant frequency of the antenna without altering its physical dimensions would be highly recommended in up-and-coming designs of antennas in mobile devices. This research work proposes a model for tuning the operating frequency of the inverted F-antenna over a reasonably wide range of frequencies, via altering the electromagnetic properties of its ferrite material. In this proposed model, it will be shown that the electronic control of the permeability of the ferrite material of the antenna leads effectively to a significant shift in its resonant frequency, and hence to an overall improvement in the performance of the communication system.

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