共查询到17条相似文献,搜索用时 203 毫秒
1.
提出一种改进的基于优先级的IEEE 802.16系统跨层调度算法,该算法综合考虑了媒体接入控制(MAC)层的业务服务质量(QoS)要求与无线信道的时变特性,通过动态调整实时轮询(rtPS)业务的优先级加权系数,在保证rtPS业务QoS要求的前提下,增加非实时轮询(nrtPS)业务和尽力而为(BE)业务的调度机会,提高nrtPS业务和BE业务的传输速率.每个连接分配的优先级根据信道和服务状态进行动态更新,每次调度优先级最高的连接.仿真结果表明,该算法能够为不同业务提供QoS保证,同时有效提高了频谱利用率和系统吞吐量. 相似文献
2.
3.
4.
5.
讨论了WDM光网中,在动态业务流量和有限范围波长变换情况下的动态路由和波长分配问题。基于Moone-Dijkstra算法,考虑到动态波长变换的可能和限制,提出了一种新型的、可实现动态最小代价路由和最佳虚波长通道的综合启发式算法(DMC-OVWP)。该算法对路由子问题和波长分配子问题既相互独立,又相互结合,优化了RWA。以中国教育和科研计算机网(CERNET)为拓扑背景,基于本算法进行了计算机仿真,并对实验结果进行了比较分析,证明本算法可充分利用网络信息获取较低的阻塞率。 相似文献
6.
波长转换是应用在全光WDM网络中打破波长一致性约束、降低网络阻塞概率的一种有效技术,但限于波长转换器的高昂成本以及其对信号失真度的影响,目前还不可能为网络中的每个节点均配置波长转换器,所以波长转换器需要以最优方案配置在网络中的个别关键节点上,本文提出了一种在任意拓扑结构的网络中,基于遗传算法的波长转换器配置算法,并对该算法在NSFNET网络上进行了计算机仿真,模拟结果显示该算法非常有效. 相似文献
7.
提出了一种基于代理(Agent)的QoS组播路由算法,它根据一个在网络中漫游的移动代理收集的网络状态来建立保证QoS的组播树,仿真实验表明,该算法是有效的和可行的。 相似文献
8.
针对未来无线通信系统必须能够同时支持多种业务类型的用户的问题,按照各用户服务质量(QoS)需求的不同将用户分为具有不同优先级的类,并基于子载波与功率分配联合优化的思想,提出了一种下行多用户OFDM系统动态资源分配方法.仿真结果表明,与现有方法相比,该方法在首先满足具有较高优先级用户的QoS需求的情况下,将更多的资源分配给优先级相对较低的用户,从而提高了资源利用率,进一步增加了系统的整体速率. 相似文献
9.
10.
11.
12.
Femtosecond wavelength conversion in the telecommunication bands via four-wave mixing in a 1.5 mm long silicon rib waveguide is theoretically investigated. Compared with picosecond pulses, the spectra are greatly broadened for the femtosecond pulses due to self-phase modulation and cross-phase modulation in the four-wave mixing process, and it is difficult to achieve a wavelength converter when the pump and signal pulse widths are close to or less than 100 fs in the telecommunication bands because of the spectral overlap. The influence of the spectral broadening on the conversion efficiency is also investigated. The conversion bandwidth of 220 nm and peak conversion efficiency of -8 dB are demonstrated by using 500 fs pulses with higher efficiency than the picosecond pulse-pumped efficiency when the repetition rate is 100 GHz. 相似文献
13.
Among the wavelength-division-multiplexing (WDM) optical packet switches (OPSs) using wavelength converters (WCs), a shared-per-node switch architecture has been considered as a way to utilize WCs efficiently. We propose a new switch control algorithm for the architecture. The proposed algorithm, different from previous algorithms, focuses on using the heterogeneous WC blocks (HeWCBs), where a HeWCB consists of WCs with different wavelength conversion degrees (WCDs). The results show that the WDM OPS architecture using HeWCBs reduces the number of WCs with a higher WCD, while minimizing the packet loss from wavelength contention at outbound links. 相似文献
14.
A. Esmaeilian-Marnani A.F. Abas M.K. Moravvej-Farshi M. Ebnali-Heidari 《Journal of Modern Optics》2013,60(8):601-606
Realization of wavelength conversion based on second-order femtosecond dark solitons with hyperbolic secant pulse is presented. This is achieved by introducing localized dispersion perturbation along the optical fiber. We demonstrate that an initial 30 fs second-order pulse decays to similar sub-pulses by applying perturbation using a step increment of β2 from 6.3 to 15.75 ps2 km?1. This shows that the realization of a 1 × 2 channel wavelength converter for femtosecond pulses is possible. Recent research shows the possibility of realizing wavelength conversion generated from picosecond solitons neglecting nonlinear effects. However, employing the same method for femtosecond pulses fails due to the manifestation of nonlinear effects. In this paper, pulse deformation under different levels of perturbation was tested, and appropriate perturbation leading to similar sub-pulses is achieved. 相似文献
15.
The authors proposed a selective assign shortest path first (SASPF) algorithm for routing and wavelength assignment in the presence of four wave mixing (FWM) in wavelength division multiplexing network with a design parameter Vm. In order to maintain a reasonably good performance in terms of blocking probability to fulfil the connection requests but also to allow acceptable FWM effects, Vm is an important design parameter (number of established optical channels to fulfil the connection requests but also to allow acceptable FWM effects). If its value is too low, many connection requests will not be able to establish, which may lead to higher blocking probability. On the other hand, if its value is too high, it may lead to obvious FWM effects that will affect the network performance. Thus, Vm must be optimum to balance the requirement of the connection requests and also the induced FWM crosstalks. Performance results show that SASPF algorithm outperforms the comparison scheme such as traditional assign shortest path first resulting in low blocking probability with a specific value of Vm. 相似文献
16.
All-optical NRZ-to-RZ format conversion with a function of wavelength multicasting is proposed in this paper, which is realized by exploiting cross-phase modulation (XPM) and four-wave-mixing (FWM) in a dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF). The designed format converter is experimentally demonstrated, for which the 1-to-4 wavelength multicasting is achieved simultaneously by filtering out two FWM idler waves and both blue-chirped and red-chirped components of the broadened NRZ spectrum induced by XPM. Moreover, the wavelength tunability and dynamic characteristics of the proposed NRZ-to-RZ format converter are also exploited using the different central wavelengths of an optical clock signal and varying the input optical power at a DF-HNL-PCF in our experiment. It is shown that the designed format converter can possess a wide range of operational wavelength over 17 nm, an optimal extinction ratio of 11.6 dB, and a Q-factor of 7.1, respectively. Since the proposed scheme uses an optical fiber-based configuration and is easy for implementation, it can be very useful for future applications in advanced fiber-optic communication networks. 相似文献
17.
First, the optical burst switching (OBS) network with limited wavelength conversion capability (LWCC) is decomposed into multiple wavelength continuous segments according to the position of wavelength converters. Based on the decomposed network model, two reservation signalling mechanisms for OBS-LWCC networks, namely wavelength-amend-on-demand (WAoD) and contention-based limited signalling protocol (CLSP), are proposed to reduce the blocking probability in the OBS-LWCC networks. In WAoD, the congested node sends a feedback message to the closest upstream switch with wavelength conversion capability. The notified switch will change the burst wavelength to the one assigned by the congested node to avoid collision in advance. Extensive simulation results indicate that by applying the wavelength reconfiguration method to the core nodes without wavelength conversion capability, the proposed WAoD scheme can improve the blocking performance in the OBS-LWCC networks significantly. Furthermore, CLSP, which combines the burst time-slot reconfiguration with the wavelength reconfiguration of WAoD, always has the lowest burst loss probability when compared with both the conventional and the proposed reservation mechanisms. 相似文献