Week I  第一周

Welcome to ECE5884/6884 Wireless Communications
欢迎来到 ECE5884/6884 无线通信课程

Cellular concept and Wireless channetbasics
蜂窝概念和无线网络基础知识

Wireless is everywhere 无线网络无处不在

The Cellular Concept 细胞概念

Early mobile radio systems
早期的移动无线电系统

• Base stations serve multiple subscribers in a cell.
  基站为一个小区的多个用户提供服务。
• Frequencies are geographically reused in cells
  在单元中按地理位置重复使用频率
• Handoff provides seamless connection
  切换提供无缝连接
• Practical considerations usually do not allow base stations to be placed elluster extly as they appear in the hexagonal layout.
  出于实际考虑，基站通常不可能像六边形布局中的那样向外放置。

The Cellular Concept 细胞概念

6G Use cases 6G 用例

ITU-Vision for 6G standard specifications (IMT-2030)
国际电信联盟 6G 标准规范愿景 (IMT-2030)

$◻$$◻$◻\square Immersive Communication: extends on the enhanced Mobile Broadband (eMBB) of ( XR and holographic communications).
$◻$$◻$◻\square 沉浸式通信：在增强型移动宽带（eMBB）的基础上扩展（XR 和全息通信）。
$◻$$◻$◻\square Hyper-Reliable and Low-Latency Communication:This scenario extends Ultra-Reliable and Low-Latency Communication (URLLC) capabilities.
$◻$$◻$◻\square 超可靠和低延迟通信：此方案扩展了超可靠和低延迟通信 (URLLC) 功能。
$◻$$◻$◻\square Massive Communication:This usage scenario extends massive Machine Type Communication (mMTC) capabilities of 5G.
$◻$$◻$◻\square 大规模通信：该使用场景扩展了 5G 的大规模机器类型通信 (mMTC) 功能。
$◻$$◻$◻\square Ubiquitous Connectivity: Intended to bridge the digital divide and provide access to the internet in places like rural and remote areas.
$◻$$◻$◻\square 泛在连接：旨在缩小数字鸿沟，为农村和偏远地区等地提供互联网接入。
$◻$$◻$◻\square Integrated Artificial Intelligence and Communication
$◻$$◻$◻\square 集成人工智能和通信
$◻$$◻$◻\square Integrated Sensing and Communication
$◻$$◻$◻\square 综合传感与通信
https://www.6gworld.com/exclusives/itu-6g-standardisationready-no-later-than-2030/

Design challenges 设计挑战

• Large bandwidth required but spectrum is fragmented
  需要大带宽，但频谱分散

• Low-latency for machine critical applications
  为机器关键应用提供低延迟

• Performance versus Complexity
  性能与复杂性

• Heterogeneous networks 异构网络

• Greater Coverage 更大的覆盖范围

• Multiradio Integration 多收音机集成

Radio Spectrum 无线电频谱

Radio Frequency Bands 无线电频段

• light frequencies for ‘optical wireless’ systems
  光无线 "系统的光频

The ITU, 3GPP and IEEE
国际电信联盟（ITU）、3GPP 和电气和电子工程师学会（IEEE

What influences the evolution and innovation of wireless systems?
是什么影响了无线系统的发展和创新？

• 3rd Generation advancement and evolution of cell diversification of wireless technologies and solutions
  第三代无线技术和解决方案的进步与发展
• Institute of Electrical and Electronics Engineers (IEEE), a professional association of engineers, scientists, and academics from various fields of technology. IEEE focuses more on the wireless technology standards, which define the physical layer, the medium access control layer, and the link layer of various wireless systems and devices.
  电气与电子工程师协会（IEEE）是一个由来自不同技术领域的工程师、科学家和学者组成的专业协会。IEEE 更关注无线技术标准，这些标准规定了各种无线系统和设备的物理层、介质访问控制层和链路层。

IEEE 802.II Wireless LAN IEEE 802.II 无线局域网

• IEEE 802 is a group that develops local area network and metropolitan area network standards, focusing on the PHY, MAC, and LINK layers
  IEEE 802 是一个制定局域网和城域网标准的组织，重点关注 PHY、MAC 和 LINK 层
• IEEE 802.II is WLAN working group (members develop standards + vote)
  IEEE 802.II 是无线局域网工作组（成员制定标准并投票）。

IEEE 802.II Subgroups IEEE 802.II 分组

• 802.1 I: I/2Mbps in 2.4 GHz band, FHSS or DSSS
  802.1 I:2.4GHz频段内的I/2Mbps，FHSS或DSSS

• 802.1 la: extend to 5 GHz band, 54Mbps, OFDM Late 90s, 3G,2Mbps
  802.1 la：扩展至 5 GHz 频段，54Mbps，OFDM 90 年代后期，3G，2Mbps
• 802.1 Ib: (WiFi) DSSS with IIMbps in 2.4 GHz band
  802.1 Ib：（WiFi）2.4 千兆赫频段 IIMbps DSSS
• $802.\mathrm{llg}$$802.\mathrm{llg}$802.llg802 . \mathrm{llg} : similar to $802.\mathrm{Il}$$802.\mathrm{Il}$802.Il802 . \mathrm{Il} but for $2.4\mathrm{GHz}2000,36$$2.4\mathrm{GHz}2000,36$2.4GHzquad2000,362.4 \mathrm{GHz} \quad 2000,36 mobile data rates were in the
  $802.\mathrm{llg}$$802.\mathrm{llg}$802.llg802 . \mathrm{llg} ：与 $802.\mathrm{Il}$$802.\mathrm{Il}$802.Il802 . \mathrm{Il} 类似，但 $2.4\mathrm{GHz}2000,36$$2.4\mathrm{GHz}2000,36$2.4GHzquad2000,362.4 \mathrm{GHz} \quad 2000,36 的移动数据传输速率在 $802.\mathrm{Il}$$802.\mathrm{Il}$802.Il802 . \mathrm{Il} 的范围内。
• 802.I In: MIMO enhancement, I00-200Mbps 2003 efforts on standardization for $4G$$4G$4G4 G
  802.I In：MIMO 增强，I00-200Mbps 2003 年在 $4G$$4G$4G4 G 标准化方面的努力
• 802. 1 l ac:Very high throughput < 6 GHz carrier celluar systems continued
       1 l ac：超高吞吐量 < 6 GHz 载波蜂窝系统续

• More bandwidth aggregation, more MIMO, multiuser MIMO
  更多带宽聚合、更多 MIMO、多用户 MIMO

• 802.I lad:Very high throughput > 6GHz carrier
  802.I梯形：吞吐量极高 > 6GHz载波

New generation of WLAN operates at $60\mathbf{G}\mathbf{H}\mathbf{z}$$60\mathbf{G}\mathbf{H}\mathbf{z}$60GHz60 \mathbf{G H z}
新一代无线局域网的运行速度为 $60\mathbf{G}\mathbf{H}\mathbf{z}$$60\mathbf{G}\mathbf{H}\mathbf{z}$60GHz60 \mathbf{G H z}

• Wireless local area networking (WLAN)
  无线局域网（WLAN）

• Gbps peak throughputs Gbps 峰值吞吐量
• In-room local area networking
  室内局域网
• Cable replacement 电缆更换

• Chipsets are available and some products are shipF
  可提供芯片组，某些产品还可出货F
• Next gen is currently in development (802.I lay)**
  下一代产品正在开发中（802.I 布局）**

• Will support MIMO spatial multiplexing
  将支持 MIMO 空间多路复用
• Channel bonding for even larger bandwidths
  通道绑定，实现更大带宽
• Targets 100 Gbps data rates
  目标是 100 Gbps 数据传输速率

The Network Stack 网络堆栈

DSP approach to wireless DSP 无线方法

Typical Digital Communication System
典型数字通信系统

How this fits with the SDR labs
如何与特别提款权实验室相结合

Components of a digital communication system
数字通信系统的组成部分

• More details will be added throughout the course
  更多详情将在整个课程中补充
• Just a reference design, some blocks may be merged or swapped
  仅为参考设计，部分模块可能会合并或交换

Propagation effects 传播效果

Reflection Scattering and Diffraction
反射散射和衍射

Modeling channel impairments
信道损伤建模

• Often called the channel 通常称为通道
  $◻$$◻$◻\square The term channel may also refer to a model for just part of the combined channel
  $◻$$◻$◻\square "通道 "一词也可指仅用于部分组合通道的模型

Channel impairments (I) 通道损伤 (I)

SNR is signal power/noise power
SNR 即信号功率/噪声功率

Channel impairments (2) 信道损伤 (2)

Channel impaiments (3) 航道障碍 (3)

• Multiple propagation paths between the transmitter and receiver
  发射器和接收器之间有多条传播路径

• Type equation here. 在此输入等式。

• h0, hl, h2: gains for the existing paths
  h0、hl、h2：现有路径的增益
• d0, dI, d2: distances travelled by the wave from $Tx$$Tx$TxT x to $Rx$$Rx$RxR x
  d0、dI、d2：波从 $Tx$$Tx$TxT x 到 $Rx$$Rx$RxR x 的距离
• c: speed of light c：光速
• $\mathrm{v}(\mathrm{t})$$\mathrm{v}(\mathrm{t})$v(t)\mathrm{v}(\mathrm{t}) : noise  $\mathrm{v}(\mathrm{t})$$\mathrm{v}(\mathrm{t})$v(t)\mathrm{v}(\mathrm{t}) ：噪音
  modeled in general as an LTI system
  一般建模为 LTI 系统
  ${\int }_0^{L}h(\tau )x(t-\tau )d\tau +v(t)$${\int }_0^L h(\tau )x(t-\tau )d\tau +v(t)$int_(0)^(L)h(tau)x(t-tau)d tau+v(t)\int_{0}^{L} h(\tau) x(t-\tau) d \tau+v(t)

Channel Impairments (4) 航道受损 (4)

• Cochannel interference, due to frequency reuse
  由于频率重用，Cochannel 干扰

• Adjacent channel interference from spectral leakage
  频谱泄漏造成的相邻信道干扰

Basics of Wireless channel characterization
无线信道特征描述基础

• Friis equation 弗里斯方程
• Ground reflection model 地面反射模型
• Fresnel zones 菲涅尔区
  $>$$>$>> Channels for mobile
  $>$$>$>> 移动渠道
• Large scale fading 大规模褪色
• Small scale fading 小规模褪色
• Doppler effects 多普勒效应

Channel Models forWireless System
无线系统通道模型

Propagation basics 传播基础知识

• How do we model the channel in a wireless system?
  如何为无线系统中的信道建模？
  $>$$>$>> What is the attenuation of the channel?
  $>$$>$>> 信道的衰减是多少？
  $>$$>$>> How does it depend on the physical environment (hills, buildings, water, etc)?
  $>$$>$>> 它如何取决于自然环境（山丘、建筑、水域等）？
  $>$$>$>> How does it depend on the design of the radio system?
  $>$$>$>> 无线电系统的设计如何决定？
  $>$$>$>> Size of antenna, positioning of antennas, choice of radio frequency
  $>$$>$>> 天线的尺寸、天线的位置、无线电频率的选择
  $>$$>$>> How does it vary with time?
  $>$$>$>> 它是如何随时间变化的？

General Characteristics of Wireless channels
无线信道的一般特性

• Point-to-point with line of sight propagation
  点对点视线传播
• E.g. microwave radio links
  例如微波无线电链路

• Simple free space propagation
  简单的自由空间传播
• Channel stable with time 通道随时间而稳定
• System designed on case by case basis - using well defined formula ((o)))
  根据具体情况设计系统--使用定义明确的公式 ((o))
• TV Broadcast-Point to area propagation
  电视广播--点对点传播
• Many different receivers 多种不同的接收器
• General optimization of transmitter (e.g. position on highest point
  发射机的总体优化（例如：位于最高点的位置
• Individual optimization of receiver (point antenna in right direction, put up a large antenna in case of poor reception)
  接收器的个性化优化（将天线指向正确方向，在接收不佳的情况下安装大天线）
• Channel relatively stable with time
  随着时间的推移，通道相对稳定
• Mobile telephone reception
  移动电话接收
• Many different receivers 多种不同的接收器
• Must work at many different locations with very different channels
  必须在许多不同的地点工作，渠道也大相径庭
• Channel may change rapidly with time (e.g. in car on freeway)
  信道可能会随着时间的推移而迅速改变（例如，在高速公路上的汽车中）

Different tools for calculating the effects of channels
计算渠道影响的不同工具

Free space and multi-path propagation
自由空间和多路径传播

$◻$$◻$◻\square For the single path case, the channel attenuation can be calculated from the directivity of the receive and transmit antenna, the area of the receive antenna and the distance between transmitter and receiver
$◻$$◻$◻\square 对于单路径情况，可以根据接收和发射天线的指向性、接收天线的面积以及发射器和接收器之间的距离计算出信道衰减。
$◻$$◻$◻\square For the multipath case, the received signal depends on how signals with the same frequency and different phases combine
$◻$$◻$◻\square 对于多径情况，接收到的信号取决于频率相同、相位不同的信号是如何组合的。

Free space propagation - Friis equation
自由空间传播--弗里斯方程

meters 仪表
$G_t$$G_t$G_(t)quadG_{t} \quad Transmiter antenna gain
$G_t$$G_t$G_(t)quadG_{t} \quad 发射机天线增益
$G_r$$G_r$G_(r)quadG_{r} \quad Receiver antenna gain
$G_r$$G_r$G_(r)quadG_{r} \quad 接收机天线增益
$\lambda$$\lambda$lambda\lambda Wavelength in meters
$\lambda$$\lambda$lambda\lambda 波长（米
$L$$L$LL is system loss factor not related to
$L$$L$LL 是系统损耗因数，与
propagation $(\mathrm{L}\ge 1$$(\mathrm{L}\ge 1$(L >= 1(\mathrm{L} \geq 1 ) 传播 $(\mathrm{L}\ge 1$$(\mathrm{L}\ge 1$(L >= 1(\mathrm{L} \geq 1 )

Friis Equation 弗里斯方程

• power falls off as square of distance in free space
  在自由空间中，功率随距离的平方而下降
• Received power depends on the gain of transmitter and receiver antennas
  接收功率取决于发射器和接收器天线的增益
• Apparent dependence on wavelength is because the gain of the antenna depends on wavelength (high gain antennas at low frequencies have larger areas)
  表面上看与波长有关，是因为天线的增益与波长有关（低频高增益天线的面积更大）。
• Friis formula a valid predictor of $P_r$$P_r$P_(r)P_{r} for $d>d_f,d_f=\frac{2D^2}{\lambda }$$d>d_f,d_f=\frac{2D^2}{\lambda }$d > d_(f),d_(f)=(2D^(2))/(lambda)d>d_{f}, d_{f}=\frac{2 D^{2}}{\lambda} is the Fraunhofer distance and $D$$D$DD is the largest physical dimension of the antenna
  当 $d>d_f,d_f=\frac{2D^2}{\lambda }$$d>d_f,d_f=\frac{2D^2}{\lambda }$d > d_(f),d_(f)=(2D^(2))/(lambda)d>d_{f}, d_{f}=\frac{2 D^{2}}{\lambda} 是弗劳恩霍夫距离， $D$$D$DD 是天线的最大物理尺寸时，弗里斯公式是 $P_r$$P_r$P_(r)P_{r} 的有效预测器

Effective antenna aperture
有效天线孔径

Free Space Pathloss 自由空间路径损耗

Propagation Characteristics
传播特性

• Path Loss (includes average shadowing)-distance dependence
  路径损耗（包括平均阴影）--与距离有关
• Shadowing (due to obstructions)-variations around the mean pathloss
  阴影（由于障碍物）--平均路径损耗周围的变化
• Multipath Fading-faster variations over shorter distances typically in the order of half a wavelength
  多径衰减--在较短距离内变化较快，通常为半个波长左右

Large and small scale fading
大规模和小规模褪色

• Large-scale fading models describe the average behavior of the channel in a small area and are used to infer channel behavior over longer distances.
  大尺度衰减模型描述的是小范围内信道的平均行为，用于推断较长距离内的信道行为。
• Small-scale fading models describe the localized fluctuations in a given area and may be location dependent.
  小尺度衰减模型描述特定区域的局部波动，可能与地点有关。
• Models for both large-scale and small-scale propagation phenomena are important.
  大尺度和小尺度传播现象的模型都很重要。
• Large-scale trends influence system planning, the link budget, and network capacity predictions, and they capture the “typical” loss in received signal strength as a function of distance.
  大规模趋势会影响系统规划、链路预算和网络容量预测，并捕捉到作为距离函数的接收信号强度的 "典型 "损失。
• Small-scale trends influence physical-layer link design, modulation schemes, and equalization strategies by capturing local constructive and destructive multipath effects.
  小尺度趋势通过捕捉本地的建设性和破坏性多径效应，对物理层链路设计、调制方案和均衡策略产生影响。
• The received signal processing algorithms depend more strongly on small-scale models, but the net performance of those algorithms in a system depends on the large-scale models as well.
  接收信号处理算法更依赖于小尺度模型，但这些算法在系统中的净性能也取决于大尺度模型。

Large scale and small scale fading
大规模和小规模褪色

Simple two path channel 简单的双通道

• Two path channel is important in a number of practical applications
  双路径通道在许多实际应用中都很重要
• Represents worst case in the design of some systems
  代表某些系统设计中的最坏情况
• Microwave links 微波链接
• Digital television transmissions with multiple transmitters on the same frequency (single frequency network SFN)
  同一频率上有多个发射机的数字电视广播（单频网络 SFN）
• Understanding the effect of ground reflection
  了解地面反射的影响
• The received power at a distance for a two-ray ground reflected model can be expressed as
  双射线地面反射模型的距离接收功率可表示为

Ground reflection model 地面反射模型

• In general reflection depends on the angle of incidence, the polarization of the signal, and the properties of the ground
  一般来说，反射取决于入射角度、信号的极化以及地面的特性。
• But for small angles (ie. Grazing incidence) the reflected wave is equal in magnitude and out of phase with the incident wave
  但对于小角度（即掠入射），反射波与入射波的大小相等，但相位不同

Ground reflection model (two ray model)
地面反射模型（双射线模型）

• Using simple geometry can calculate the total electrical field as a function of distance
  利用简单的几何原理可以计算出总电场与距离的函数关系

To summarize so far 现总结如下

Mechanisms in fixed wireless design and large scale fading
固定无线设计和大规模衰减的机制

• Practical measurements in German cities show that the dependence can be very different from this
  德国城市的实际测量结果表明，依赖关系可能与此大相径庭

Fresnel Zone 菲涅尔区

• Path differences of $\lambda /2$$\lambda /2$lambda//2\lambda / 2 cause signals to cancel
  $\lambda /2$$\lambda /2$lambda//2\lambda / 2 的路径差异会导致信号抵消
• How close does an object have to have the potential
  物体距离多近才有可能

• See Rappaport for derivation in terms of diffraction
  有关衍射的推导，请参阅 Rappaport。
• Shows that points which can result in $\lambda /2$$\lambda /2$lambda//2\lambda / 2 path difference are located on an ellipse
  显示可能导致 $\lambda /2$$\lambda /2$lambda//2\lambda / 2 路径差异的点位于椭圆上
• Similarly for other path lengths that result in cancellation
  同样，其他路径长度也会导致抵消
• But used as rule-of-thumb in microwave link design the first Fresnel zone is used to signal degradation with methods such as Bullington
  但在微波链路设计中，第一菲涅尔区被用作信号衰减的经验法则，例如布林顿法

Fresnel Zone 菲涅尔区

Log-distance Path Loss Model
对数距离路径损耗模型

Log-Normal Shadowing 对数正态阴影

• The model Log-distance PL model does not take into consideration the surrounding environmental clutter.
  对数距离 PL 模型没有考虑周围的环境杂波。
• Measurements have shown that at any value of $d$$d$dd, the path loss $\mathrm{PL}(\mathrm{d})$$\mathrm{PL}(\mathrm{d})$PL(d)\mathrm{PL}(\mathrm{d}) at a particular location is random and distributed lognormally about the mean distance-dependent value.
  测量结果表明，在 $d$$d$dd 的任何值上，特定位置的路径损耗 $\mathrm{PL}(\mathrm{d})$$\mathrm{PL}(\mathrm{d})$PL(d)\mathrm{PL}(\mathrm{d}) 都是随机的，并围绕与距离相关的平均值对数正态分布。
• ${\mathrm{PL}}_{\mathrm{dB}}(d)={\mathrm{PL}}_{\mathrm{dB}}(d)+X_{\sigma }={\mathrm{PL}}_{\mathrm{dB}}\left(d_0\right)+10n\log \left(\frac{d}{d_0}\right)+X_{\sigma }$${\mathrm{PL}}_{\mathrm{dB}}(d)={\mathrm{PL}}_{\mathrm{dB}}(d)+X_{\sigma }={\mathrm{PL}}_{\mathrm{dB}}\left(d_0\right)+10n\log \left(\frac{d}{d_0}\right)+X_{\sigma }$PL_(dB)(d)=PL_(dB)(d)+X_(sigma)=PL_(dB)(d_(0))+10 n log((d)/(d_(0)))+X_(sigma)\mathrm{PL}_{\mathrm{dB}}(d)=\mathrm{PL}_{\mathrm{dB}}(d)+X_{\sigma}=\mathrm{PL}_{\mathrm{dB}}\left(d_{0}\right)+10 n \log \left(\frac{d}{d_{0}}\right)+X_{\sigma}
  $X_{\sigma }$$X_{\sigma }$X_(sigma)X_{\sigma} is zero-mean Gaussian distributed random variable (in dB ) with standard deviation $\sigma$$\sigma$sigma\sigma (also in dB).
  $X_{\sigma }$$X_{\sigma }$X_(sigma)X_{\sigma} 为零均值高斯分布随机变量（单位为 dB），标准偏差为 $\sigma$$\sigma$sigma\sigma （单位也是 dB）。

Path Loss for different environments
不同环境下的路径损耗