现代通信技术概论大作业-北京印刷学院.

现代通信技术概论大作业 班级:姓名:学号: 浅谈通信系统光纤技术应用及其发展 在这几十年的发展历程中,光纤通信已经成为现代通信技术的重点。应用光纤通信最大的技术优点是信息容量大;且光纤的损耗低、传输距离长;光纤通信不易被电磁干扰,对信息的保密性能好:可以有效节约有色金属;光缆尺寸小,便于安装和运输。下面我将从四个方面论述光纤技术的发展: 一、光纤通信的特点 1、频带极宽,通信容量大 在光纤技术中,光纤可以容纳50000GHz传输带宽,光纤通信系统的容许频带(带宽是由光源的调制特性、调制方式和光纤的色散特性决定的。例如,单波长光纤通信系统一般是使用密集波分复用等一些复杂的技术,以便解决通信设备的电子瓶颈效应的问题,保证光纤宽带可以发挥更积极的作用,从而增加光纤的信息传输量。目前,单波长光纤通信系统的传输率已经得到了2.5Gbps到 lOGbps。 2、抗电磁干扰能力强 光纤的制作材料主要是石英,其绝缘性好,抗腐蚀能力强。因此,光纤有较强的抗电磁干扰能力,且不受雷电、电离层的变化和太阳黑子活动等电磁影响,也不会被人为释放的电磁所干扰,这就是石英这种通信材料的最大优势。除以上有点之外,光纤体积小、质量轻,不仅可以节省空间,还便于安装;光纤的制作材料资源丰富,成本低;光纤的温度稳定性好,使用寿命长。由于光纤通信的优点很多,使其使用范围也不断扩宽 二、光纤通信技术的应用 自上世纪9O年代以来,我国光纤通信技术已经得到了很大的发展,特别是广播电视网、电力通信网、电信干线传输网等方面更是发展迅速,促使光纤生产量不断增加。现代信息网络通信系统不断扩展和增加,导致网络的管理和维护,以及设备的故障判定和排除就显得更加困难和繁杂。此时,我们采用 SDH+光纤或ATM十光纤组成宽带数字传输系统,这种传输系统可以保证环网传输的稳定性,链路传输系统或者组成各种形式的复合网络,也能满足各种信息传输的需要。针对电视节目的传输,我们同时是采用的宽带传输系统进行传输,将主站到地方站的所有数字信息设置成广播的方式,让同样的电视节目可以在不同的地方下载,也能利用网络管理平台的控制,以便不同的站点可以下载不同的节目。目前,有线电视已经在全国普及,在有线电视的网络支持下,宽带多媒体传输网络就更容易实现了,因此,在这种情况下,我们不应完全废除现有的有线电视网,而是科学的利用它,满足人们的需要,将光纤通信技术融入到千万家,方便人们的生活。不息的活力、不利于古村的保护和文化的传承,修缮古建筑后,完善其内部基础设施,疏通治理莲塘水系,使古村宜居宜用,并逐步迁移或导入居住、办公、商业或展示等功能,采取合理 措施 《全国民用建筑工程设计技术措施》规划•建筑•景观全国民用建筑工程设计技术措施》规划•建筑•景观软件质量保证措施下载工地伤害及预防措施下载关于贯彻落实的具体措施 活化古村落,使之恢复往日的生机与活力。 三、现代通信系统的光纤技术 l、单纤双向传输技术 单纤双向传输技术是针对双纤双向传输而言的,双纤传输时,其信号可以在两根不同的光纤中传输,而单纤传输时,信号在调频过后可在不同的波段后,在同一根光纤里传输。现代光纤的传输容量不断增大,从理论上说,光纤传输的容量是无限的,只是受到设备等各种因素的影响,传输容量大大降低,远不及预期的效果。目前,光纤通信传送网都是通过双纤双向传输的,如果利用单纤双向传输技术就能有效的节省一半的光纤资源,而对于现代庞大的光纤网络传输系统中,可节省的光纤资源数量也是十分庞大的。研发出成熟的单纤双向传输技术对网络通信的发展有十分积极的意义。单纤双向传输技术已经得到了广泛的使用,但主要用在光纤末端接入设备:PON无源光网络、单纤光收发器等设备,骨干传送网上还没有使用到这种技术。可见,这也是光纤通信技术的未来发展方向。 2、光纤到户 (FTTH接入技术 高速数据通信和高质量视频通信等媒体业务的发展和拓展,对现代宽带综合业务网的研究起到了积极的推动作用。而今,核心网便成为了以光纤线路为基础的高速信道,国际权威专家认为,宽带综合信息接入网是现代信息高速公路发展的“最后一公里”,同时也指出,这是信息通信发展的又一个瓶颈。虽然ADSL技术为现代通信业务提供了良好的基础,但对于未来将要发展的通信业务,如:网上教育,网上办公,会议电视,网上游戏等双向业务和HDTV高清数字电视,尤其是HDTV,现阶段的传输率仅为19.2Mbps,用 l-I.264压缩技术可以压缩到 5—6帕ps。在实践中,OOS有所保证的ADSL的最高传输速率是2Mbps,但仍然难以传输HDTV高清数字电视。而使用铜线接入的ADSL的方式已经无法再满足数据高速传输的需求,采用光纤接入技术已成为必然趋势,是未来通信技术的发展趋势 四、光纤通信技术的发展趋势 1、向超高速系统发展 超高速的系统使得传输容量增加,这样以来我们便可以增加各种所需的新业务,为实现多媒体和宽带提供了坚实的保障。从电信发展史来看,对于传输速率的提高和对于网络容量的需求一直存在着矛盾,所以为了能够更好的解决这对矛盾,我们要提高光纤通信系统的速度。 2、向超大容量进军 因为电的时分复用系统的扩展容量的潜力已经被开发殆尽,但是光线的200nm 可用的宽带资源才仅仅利用了很少的比例,还有极大的资源有待于发掘。如果我们能够充分的发掘这些资源,利用相关的技术。这样不仅仅可以充分的利用巨大的宽带资源,使得容量有一个极大的扩展,而且也可以节省许多的光纤和再生器,降低了成本。 3、实现光联网战略方向 因为光纤通信技术的飞速发展,那么未来的高速通信网节点之间便可能实现全光化,传输的信息会以光的形式进行传输。这是未来的光通信的发展的方向。 4、光接入网 光接入网包括光数字环路载波系统和无源光网络两个类型,其能够减少维护管理的费用,使得故障发生的频率降低,有利于对新设备的开发,两种类型网络可以使得收入有所增加;随着本地网络结构的调整,可以扩大覆盖的范围,那么对于实现智能化的全光网络则指日可待。 5、开发新一代的光纤 为了能够适应干线网和城域网的不同发展的需求,出现了非零色散光和无水吸收峰光纤两个不同的新型光纤 翻译 英文原文: Frequency Hopping First, the frequency hopping Radio communication is an essential means of communication during the war, but traditional radio communications are working under a fixed frequency, the enemy can easily be intercepted or impose electronic interference, so that the communication failure. Frequency Hopping is the drawbacks of traditional radio communications, so that the original letter fixed radio frequency and speed at a certain law of jump back and forth. Communication from the interference point of view, the carrier frequency hopping communication is by a random jump to avoid interference, the interference rejection at the receiver interference channel to achieve the purpose other than to avoid enemy radio direction finding and jamming. Frequency-hopping communication technology in anti- jamming communications of the outstanding advantages, so that it can be widely used in communication equipment, and VHF communications equipment as the main interference technology. Frequency hopping is not only a skilled defense against external interference, and for the suppression of long-distance radio communications caused by itself is also very effective multi-path interference. Because the use of frequency hopping, due in the main wave beam has been received, while the other radial beams have not yet reached the receiver, the transmit and receive carrier frequency on the long jump to another frequency, thus avoiding the multipath effects on the quality of communication effects. Second, the key technology of frequency hopping communication 1 hopping pattern Used to control the address of the carrier frequency hopping code sequence is often referred to as frequency hopping sequence. Under the control of the frequency hopping sequence, the law of frequency hopping carrier called the frequency hopping patterns. 2 Synthesis din Frequency hopping communication system is a system variable frequency synthesizer core part of the sum of the frequency hopping rate determines the frequency hopping system with anti-jamming capability. From the principle that the frequency hopping communication system with common variable frequency synthesizer frequency synthesizer is no different, but there are two characteristics. First, controlled by the frequency hopping sequence, frequency hopping to increase the number of wider expansion of the frequency, the greater the system's processing gain; the second is to jump fast enough frequency, the system can quickly jump from one frequency to another frequency , to avoid the forwarding of external interference. 3 Synchronization For frequency hopping systems, synchronization is the sending and receiving ends must have the same frequency of variation, that is, every time there is a definite frequency hopping strict correspondence. In particular, the requirement to do two things: First, the hopping pattern so that the receiver and transmitter frequency hopping pattern is consistent, so to come through a mixer (multiplication to complete the solution jump. Second, extract the received signal carrier frequency, using the received signal as it related to detection, demodulation information Third, interference of frequency hopping communication Frequency Hopping four necessary conditions for interference (1 time-domain conditions: the frequency tracking target is the real-time measurement of the jamming frequency hopping and interference in the transmitting frequency signals, because interference device response time and the impact of wave propagation time, launch time is always interfering signals lag behind the communication signals. Dwell time at the signal frequency, as long as 50% of the time be disturbed, you can achieve effective interference. This requires guidance from the jamming equipment was intercepted in the receiver signal to the interference signal reaches the receiver, the total delay time, the signal must not be less than the dwell time in 5O%. (2 airspace conditions: is the frequency hopping communication transmitter, receiver and jammer geographical location should satisfy the mathematical relationships. In order to effectively interfere with frequency hopping system, the communication frequency to jump before the new frequency, the jammer must complete release from listening to the whole process of interference. (3 Frequency Domain: The spectrum and frequency hopping communication signal to carry information in the spectrum coincide, so that in the frequency domain is difficult to separate the two linear wideband jammer hopping frequencies measured in real time, during treatment Verify before comparing to see if it meet the same conditions to meet the implementation of the interference signal transmission, does not meet the continued search frequency. Ji Road disturbed accounted hopping ratio of total number of channels and the format of the hop rate and signal, but, whatever the form of hop rate and signal, as long as more than 5O% interfered channel, can achieve the purpose of effective interference. (4 to field conditions:normal circumstances, the interference signal should be required to communicate with the suppression of enemy interference frequency. The most effective of frequency hopping communications interference is the following three: (1 narrow-band frequency of target-type interference: interference with a single channel for narrowband interference. Aimed at jamming the frequency band, first intercepted and analyzed to guide the search signal receiver, and then choose the best transmitter interference pattern starts to interfere with the beginning in accordance with the needs of power, at a certain frequency, the interference of high-power cast a long time, that single- Frequency Interference. (2 block-type interference:interference with a band for multiple channels of wideband interference. Block-type interference, the first linear sweep, and then sweep the frequency range, the implementation of a continuous block or comb block jamming jamming. It is divided by full-band frequency range and partial band interference. (3 frequency tracking target type interference: the interference method is measured in real time the frequency hopping, and it combines the targeting frequency band jamming jamming and blocking the merits, to take a compromise approach that also uses narrow-band interference, to avoid jamming due to interference blocking scattered over a wide power band and need a very high interference power, by using a full band scan, the use of interfering with the frequency, narrow-band frequency increased the flexibility of targeting jamming. Fourth, frequency hopping in the role of commercial mobile communication Intensive areas in the business, GSM system capacity by frequency reuse interference from restrictions, and the relative carrier to interference ratio may vary widely between calls. Carrier level generally increased with distance from the mobile station and base station and the barriers between each other and change the situation. The interference level is largely dependent on the neighboring district of the same frequency interference. Because the system aims to meet the additional requirements of users as possible, when not selected frequency hopping, if a certain frequency interference occurs when a user takes when the frequency will cause a decline in voice quality, leaving the user to accept, If the interference is continuous, it is likely to cause poor quality of dropped calls. When using frequency hopping, the interference of the carrier will be shared with other calls, interference was average, the interference is no longer in a continuous state, and in a sudden state of the overall network performance will be greatly improved. After analysis, the use of frequency hopping network than the network does not use high-3dB frequency hopping gain. GSM system uses slow frequency hopping, frequency hopping rate of 217 hop / s, FH carried out in two when the band to band, a time slot with a fixed frequency transceivers, the next time slot with another frequency transceiver, to reduce interference effects. 中文翻译: 跳频通信 一、跳频技术 无线电通信是战时通信的必备手段,但是,传统的无线电通信都是在某一固定频率下工作,很容易被敌方截获或施加电子干扰,从而使通信失灵。 跳频通信就是针对传统无线电通信的弊端,使原先固定不变的无线电发信频率按一定的规律和速度来回跳变。从抗干扰通信角度来看,跳频通信是靠载频的随机跳变来躲避干扰,将干扰排斥在接收信道以外来达到抗干扰的目的,避免敌方电台的 测向和干扰。跳频通信技术在抗干扰通信方面的突出优势,使其在通信装备中得以广泛应用,并且成为超短波通信装备的主要抗干扰技术。 跳频技术不仅是抵御外来干扰的能手,而且对于抑制远距离无线电通信本身所造成的多径干扰也十分有效。因为采用跳频技术后,由于在主波波束己被接收,而其他径向波束尚未到达接收机时,发送和接收载频早已跳到别的频点上,因而避免了多径效应对通信质量的影响。 二、跳频通信的关键技术 1跳频图案 用来控制载波频率跳变的地址码序列通常称为跳频序列。在跳频序列控制下,载波频率跳变的规律称为跳频图案。 2频率合成嚣 跳频通信系统的可变频率合成器是系统的核心部分,跳变频率的总和与跳频速率决定了系统的抗干扰能力。从原理上说,跳频通信系统的可变频率合成器与普通的频率合成器没什么不同,但有两个特点。一是受跳频序列控制,跳频数增加则扩展的频率越宽,系统的处理增益就越大;二是能足够快的跳变频率,使系统能够很快的从一个频率跳到另一个频率,躲避来自外部的转发性干扰。 3同步技术 对跳频系统来说,同步就是收、发两端的频率必须具有相同的变化规律,即每次跳变频率上有确切严格的对应关系。具体而言,要求做到以下两点:一是使 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 示接收机的跳频图案与发射机跳频图案相一致,这样才能通过混频器(相乘来完成解跳。二是提取接收信号的载波频率,用它对接收信号作相关检测,解调信息三、对跳频通信的干扰 跳频通信干扰的四个必要条件 (1时域条件:由于频率跟踪瞄准式干扰是实时测量出跳变的频率,并在该频率上发射干扰信号,因为干扰设备反应时间和电波传播时间的影响,干扰信号的发射时间总是滞后于通信信号。在信号频率的驻留时间内,只要有50%的时间被干扰,就可以达到有效干扰。这就要求从干扰设备的引导接收机截获到信号,到干扰信号到达接收机的总延迟时间,必须不小于信号驻留时间的5O%。(2空域条件:是指跳频通信发信机、接收机以及干扰机所处的地理位置应该满足的数学关系。 为了有效地干扰跳频系统,在通信频率跳到新的频率之前,干扰机必须完成从侦听到施放干扰的全过程。 (3频域条件:干扰频谱与跳频通信信号中携带信息的频谱相重合,这样,在频域就难以将二者分开干扰机采用线性宽频带实时测出跳变频率,在进行处理前进行验证比对,看是否满足相等条件,满足则实施干扰信号发射,不满足则继续搜频。被干扰的佶道数占跳频总信道数的比例与跳速和信号形式有关,但是,无论哪种跳速和信号形式,只要干扰了5O%以上的信道,都可以达到有效干扰的目的。 (4能域条件:一般情况下,干扰信号应具有压制敌方通信所需的干扰频率。 对跳频通信最有效的干扰是以下三种: (1窄带频率瞄准式干扰:用于干扰单个信道的窄带干扰。窄带频率瞄准式干扰,先由引导接收机搜索截获并分析信号,然后选择最好的干涉样式启动发射机开始按照需要功率进行干扰,在某一个频率上施放长时间的大功率的干扰,即单频 干扰。 (2拦阻式干扰:用于干扰一个频段内多个信道的宽带干扰。拦阻式干扰,先 进行线性扫频,然后根据扫到的频率范围,实施连续拦阻式干扰或者梳状拦阻式干扰。它按频率范围分为全频段和部分频段干扰。 (3频率跟踪瞄准式干扰:这种干扰方式是实时测量出跳变的频率,并且它结合了窄带频率瞄准式干扰和拦阻式干扰的优点,采取一种折中的方法,即也采用窄带干扰, 避免了拦阻式干扰由于干扰功率分散在很宽的频段上而需要很高的干扰功率,由使用了全频段扫描,采用跟频干扰,提高了窄带频率瞄准式干扰的灵活性。 四、跳频技术在商业移动通信中的作用 在业务密集区,GSM系统的容量受频率复用产生的干扰限制,相对载干比可能在呼叫之间有很大的变化。载波电平一般随移动台与基站的距离及相互间的障碍情况变化而变化。而干扰电平则在很大程度上依赖于邻近小区的同频干扰。由于系统的目标是尽可能满足更多用户的要求,当不选用跳频时,若某一频点出现干扰,当某用户占用该频点时就会造成通话质量下降,而使用户难以接受,若干扰是连续的,很容易造成质量差掉话。当使用跳频时,该干扰情况就会被该载波的其他呼叫所共享,干扰被平均了,干扰不再处于连续状态,而处于突发状态,整个网络的性能将得到很大提高。经分析,使用跳频的网络可比不采用跳频的网络高3dB 的增益。GSM系统中采用慢跳频技术,跳频速率为217跳/秒,跳频在两个时隙间进行,一个时隙内用固定频率收发,下一时隙用另一频率收发,以减小干扰的影响。