【正文】 第三種方法是從實(shí)驗(yàn)和簡(jiǎn)單信道仿真模型去提取所需知識(shí) 。 有三種基本技術(shù)類實(shí)現(xiàn)這個(gè)目標(biāo)：測(cè)量，仿真和建模 。 錯(cuò)誤編碼控制是提高任何數(shù)字通信系統(tǒng)質(zhì)量的重要技術(shù)。 我們比較了功率效率和帶寬效率的調(diào)制方案如表 1。平均傳輸光功率 PT 是平均時(shí)間內(nèi)的 X（ t）。 皮膚安全也 需要引起關(guān)注。 周期性的噪音是變化的熒光燈中驅(qū)動(dòng)燈管的鎮(zhèn)流器使用的結(jié)果。另一個(gè)重要的考慮因素是主要的噪音源 — 背景照明 的光譜分布 。 對(duì)人眼來說 發(fā)光二極管比激光二極管更安全 ， 激光二極管 通常 具 有很窄的光束。這些包括環(huán)境照明如自然光，日光燈光，白熾燈 光等 。一個(gè)有效的解決方法是使用強(qiáng)度調(diào)制，在調(diào)制信號(hào) 中 傳輸信號(hào)的強(qiáng)度 和功率 成正比 。 C． 基礎(chǔ)和大綱 大多數(shù)無線紅外通信系統(tǒng)，可以模擬 其輸出信號(hào) Y（ t）和輸入信號(hào) X（ t），并得出其表達(dá)式 其中 表示卷積， c（ t）是在通道 N（ t）為加性噪聲 時(shí)的脈沖響應(yīng)。該系列產(chǎn)品的視距（ LOS）路徑從發(fā)射器到接收器必須 沒有 障礙物，最 好 是光直接射向接收機(jī) 。這可以 是對(duì) 現(xiàn)有的局域網(wǎng) 的延伸 ，或 在沒有網(wǎng)絡(luò)的地方建立網(wǎng)絡(luò) 。 source coding and ARQ coding are not considered here. Trelliscoded PPM has been found to be an effective scheme for multipath infrared channels(10,11).The key technique is to recognize that although on a distortionfree channel, all symbols are orthogonal and equidistant in signal space, this is not true on a distorting channel. Hence, trelliscoding using set partitioning designed to separate the pulse positions of neighboring symbols is an effective coding method. Coding gains of dB electrical have been reported for rate 2/3coded 8PPM over uncoded 16PPM, which has the same bandwidth(11). C. Channel impulse response characterization Impulse response characterization refers to the problem of understanding how the impulse response C(t) in Equation (1) depends on the location, size, and orientation of the receiver and transmitter. There are basically three classes of techniques for acplishing this: measurement, simulation, and modeling. Channel measurements have been described in several studies(9,12,2), and these form the fundamental basis for understanding the channel properties. A particular study might generate a collection of hundreds or thousands of example impulse responses Ci(t) for configuration i. The collection of measured impulse responses Ci(t) can then be studied by looking at scatter plots of path loss versus distance, scatter plots of delay spread versus distance, the effect of transmitter and receiver orientations, robustness to shadowing, and so on. Simulation methods have been used to allow direct calculation of a particular impulse response based on a sitespecific characterization of the propagation environment(13,14). The transmitter, receiver, and the reflecting surfaces are described and used to generate an impulse response. The basic assumption is that most interior surfaces reflect light diffusely in a Lambertian pattern, . all incident light, regardless of incident angle, is reflected in all directions with an intensity proportional to the cosine of the angle of the reflection with the surface normal. The difficulty with existing methods is that accurate modeling requires extensive putation. A third technique attempts to extract knowledge gained from experimental and simulationbased channel estimations into a simpletouse model. In (15), for example, a model using two parameters (one for path loss, one for delay spread) is used to provide a general characterization of all diffuse IR channels. Methods for relating the parameters of the model to particular room characteristics are given, so that system designers can quickly estimate the channel characteristics in a wide range of situations. 翻譯 : 無線紅外通信 無線紅外通信指的是使用近紅外波段的光作為通信傳輸介質(zhì)的一種通訊方式（ 13），如圖 1 所示。原文 ： Wireless Infrared Communications I. Introduction Wireless infrared munications refers to the use of freespace propagation of light waves in the near infrared band as a transmission medium for munication(13), as shown in Figure 1. The munication can be between one portable munication device and another or between a portable device and a tethered device, called an access point or base station. Typical portable devices include laptop puters, personal digital assistants, and portable telephones, while the base stations are usually connected to a puter with other worked connections. Although infrared light is usually used other regions of the optical spectrum can be used (so the term wireless optical munications instead of wireless infrared munications is sometimes used). Wireless infrared munication systems can be characterized by the application for which they are designed or by the link type, as described