1、宁波大学宁波大学 2016 年攻读博士学位研究生年攻读博士学位研究生入入 学学 考考 试试 试试 题题(A 卷卷)(答案必须写在答题纸上)考试科目考试科目:数字通信数字通信科目代码科目代码：3807适用专业适用专业:通信与信息系统通信与信息系统/信号与信息处理信号与信息处理/移动计算与人机交互移动计算与人机交互第 1 页 共 5 页一、填空（每空一、填空（每空 2 分，共分，共 20 分）分）1、数字通信的任务是（）、（）地传递信息。2、设在s125内传输 256 个二进制码元，则码元传输速率是（）。3、时变随参信道的特点是（）、（）、（）。4、设到达接收端的已调信号功率和信道噪声的功率谱密度
2、已经给定。降低调制指数后，FM 解调器的输入信噪比（）；对于 AM，包络检波器输入的信噪比（）。5、出现概率越（）的消息，其所含的信息量越大；出现概率越（）的消息，其所含的信息量越小。二、选择题（每空二、选择题（每空 2 分，共分，共 10 分）分）(a) 2DPSK(b) 2ASK(c) 2(d) 4(e) 快(f) 慢(g) 倒现象(h) 相位错移(i)kb/slog2M(j)kb/slog102M(k) 1(l) 3(m) 时域均衡(n) 循环稳定(o) 高(p)61、某二进制信源中连续出现的 0 的个数最多是 6 个，此信源经过 HDB3、数字分相码编码后，编码结果中连续出现的 0 的
3、个数最多分别是（）和（）个。2、对于传输信道所引入的码间干扰，一种基本的解决方法是采用（）。3、如果升余弦滚降系统的滚降系数越小，则相应的系统总的冲激响应 x (t)的拖尾衰减越（）。4、 BPSK 信号在接收端因为载波同步系统中的分频，可能产生载波相位状态转移，发生对信号的错误解调，这种现象称为（）。三、计算题（三、计算题（10 分）分）设某个数字通信传输系统传送二进制码元的速率为 3600B，试求该数字通信传输系统的信息速率；如果将该数字通信传输系统改为传送 32 进制信号码元，假设其码元速率不变，则此时该数字通信传输系统的信息速率是多少？宁波大学宁波大学 2016 年攻读博士学位研究生年
4、攻读博士学位研究生入入 学学 考考 试试 试试 题题(A 卷卷)(答案必须写在答题纸上)考试科目考试科目:数字通信数字通信科目代码科目代码：3807适用专业适用专业:通信与信息系统通信与信息系统/信号与信息处理信号与信息处理/移动计算与人机交互移动计算与人机交互第 2 页 共 5 页四、四、Translate the following from English into Chinese. And，say something aboutyourunderstandingofdigitalcommunications,communicationsystem,orinformation syste
5、m.(60 分分)It has been more than a few decades since mobile wireless communications were initiated with the firstgeneration, voiceonly systems. Over the last couple of decades the world has witnessed gradual, yetsteady evolution of mobile wireless communications towards second, third and fourth genera
6、tionwireless networks. Introduction of digital modulations, effective frequency reuse, penetration ofpacket-based Internet and rapid advancement in physical layer technologies, like WCDMA, OFDMA,MIMO, HARQ etc. have significantly contributed towards this gradual evolution. Besides this, with theever
7、 increasing popularity of smart devices, currently all-IP based fourth generation LTE networkshave become a part of everyday life. As a result, a set of new, user-oriented mobile multimediaapplications, like mobile video conferencing, streaming video, e-healthcare and online gaming arecoming up. The
8、se new applications are not only satisfying users requirements, but also opening upnew business horizons for wireless operators to increase their revenue. The combined effect ofemergingmm-wavespectrumaccess,hyper-connectedvisionandnewapplication-specificrequirements is going to trigger the next majo
9、r evolution in wireless communications - the 5G (fifthgeneration). 5G wireless communications envision magnitudes of increase in wireless data rates,bandwidth, coverage and connectivity, with a massive reduction in round trip latency and energyconsumption. It points out that the first standard is ex
10、pected to mature by 2020. Group Special MobileAssociation (GSMA) is working with its partners towards the ultimate shaping of 5G communication.Withtheseeightabove-mentionedrequirements,wirelessindustries,academiaandresearchorganizations have started collaborating in different aspects of 5G wireless
11、systems. It shows the visionof 5G from different globally famous wireless vendors and operators. Ericsson expects 5Gdevelopment should start in a backward compatible way with existing 4G LTE networks. This will helpin continuing services using the same carrier frequency to traditional devices. Erics
12、son is alsocollaborating with South Korean market leader SK Telecom, for demonstrating 5G networks at 2018winter Olympics. Qualcomm is developing and driving 4G and 5G in parallel to achieve the maximum宁波大学宁波大学 2016 年攻读博士学位研究生年攻读博士学位研究生入入 学学 考考 试试 试试 题题(A 卷卷)(答案必须写在答题纸上)考试科目考试科目:数字通信数字通信科目代码科目代码：380
13、7适用专业适用专业:通信与信息系统通信与信息系统/信号与信息处理信号与信息处理/移动计算与人机交互移动计算与人机交互第 3 页 共 5 页potential. The unified platform should help in improving cost and energy efficiency, while enabling avast range of new services. Huawei is collaborating with international trade associations, manyuniversities, governments and ecosy
14、stem partners to establish crucial 5G innovations. Docomo networkhas identified two important trends, pervasive wireless connectivity, extensive rich content delivery inreal time. It believes integration of both the higher and lower frequency bands holds the key to 5Gdeployment. The lower frequencie
15、s will be responsible for basic coverage and the higher frequencieswill provide high data rates. Optimizing spectrum usage, revolutionary advances in 5G, dense smallcells and improved performance are key concepts of Nokias realization for 5G wireless. Billions ofautonomously connected diverse device
16、s, leading to the beginning of IoT is Samsungs vision for 5G.METIS (Mobile and wireless communications Enablers for the Twenty-twenty (2020) InformationSociety) and HORIZON 2020 are the major 5G research project initiated and funded by the EuropeanUnion (EU). To deploy 5G in alignment with the marke
17、t demands, 5GPPP is working for earlyagreements with major stakeholders for multitenancy and single digital market. IEEE CommunicationSocietys5G Training and Certification initiative is coordinating 5G training at IEEE-sponsoredworkshops and conferences, with the process of developing a 5G certifica
18、tion program. Collaborativeresearch and development efforts between South Korea, Japan and China have resulted in the formationof 5G forum. Overall layout of 5G wireless networks breaks the rules of BS centric cellular conceptand moves towards a device centric topology. 5G network proposes the use o
19、f higher frequencies forcommunication. The propagation and penetration of mm-wave signal in outdoor environment is quitelimited. Thus, node layout can not follow traditional cellular design or even any definite pattern.Rappaport and his group propose site specific node layout for 5G radio network de
20、sign. For instance,ultra dense deployment is necessary in areas requiring high data rates, like subway stations, malls andoffices. Line of Sight (LOS) communication is undisputed preference over Non Line of Sight (NLOS)communication. Alternately, reflected, scattered and diffracted signals still mig
21、ht have sufficientenergy, which needs to be explored when LOS is completely blocked. 5G cellular technology needs towork with an enormous number of users, variety of devices and diverse services. The primary concerntherefore, is the integration of 5G BSs with the legacy cellular networks (e.g. 4G, 3
22、G and 2G).Different configurations like, mm-wave BS grid systems, mmwave integrated with 4G systems andmm-wave standalone systems are proposed by Farooq and his team at Samsung Electronics. Large宁波大学宁波大学 2016 年攻读博士学位研究生年攻读博士学位研究生入入 学学 考考 试试 试试 题题(A 卷卷)(答案必须写在答题纸上)考试科目考试科目:数字通信数字通信科目代码科目代码：3807适用专业适用
23、专业:通信与信息系统通信与信息系统/信号与信息处理信号与信息处理/移动计算与人机交互移动计算与人机交互第 4 页 共 5 页beamforming gains extend the coverage, while reducing interference and improving link quality at thecell edges. This feature enables mm-wave BS grids to provide low latency and cost effective solutions.It proposes a dual-mode modem, enabl
24、ing the user to switch between the two networks for betterexperience. Alternately, mm-wave spectrum can also be used only for data communications, whilecontrol and system information can be transmitted by using traditional 4G networks. Standalone 5Gsystems operate exclusively on mm-waves. Such syste
25、ms envision the use of same mm-wave spectrumfor both backhaul and wireless access links. The concept of narrow beams allows acceptable spectrumoverlap and also improves link quality between BS grids and large number of users. Thus, the radionetworking in 5G communications is expected to be much diff
26、erent from legacy networks. Evolution inradio would also change the schematics of the air interface.Successful deployment of 5G networks depends on the effective antenna array design. This exploits theadvantages of change in air interface. The multi-beam smart antenna array system should be used tor
27、ealize SDMA capabilities. Smart antennas help in interference mitigation, while maintaining theoptimal coverage area and transmit power reduction of both mobile handset and BS. Moreover, for thesame physical aperture size, more energy can be transmitted at higher frequency by the use of narrowbeams.
28、 Smart antenna implementation enables the same channel to be used by different beams. Thisreduces one of the major problems of wireless communications: co-channel interference. Use ofbeamforming antennas, with fractional loading factor, further dilutes the co-channel interferenceproblem. Application
29、 of highly directional beams do not necessarily require any fractional loading.Infrastructure expenses and complex operations impede indiscriminate use of directional antennas.However, even less complex antennas are capable of providing considerable capacity gains. Therefore,a smart antenna design,
30、optimized over directional gains, cost and complexity is very important fordevelopment of 5G wireless communications. Vertical planar subarrays steer the beams in horizontalplane by varying the weights associated with the subarray elements. The subarray configurations arecrucial for beam steering. T
31、hree different possibilities to arrange an antenna subarray circular, planarand segmented.Bettercoverageofcircularsubarray makesitmoresuitableforwirelesscommunications. While curvature allows wider beam steering, linear configurations have betterdirectivity, but limited scan-angle range. Instead of
32、circular or linear, simple segmented configurationscan also be carefully designed to achieve the required level of directivity and scan range. Generally,宁波大学宁波大学 2016 年攻读博士学位研究生年攻读博士学位研究生入入 学学 考考 试试 试试 题题(A 卷卷)(答案必须写在答题纸上)考试科目考试科目:数字通信数字通信科目代码科目代码：3807适用专业适用专业:通信与信息系统通信与信息系统/信号与信息处理信号与信息处理/移动计算与人机交互
33、移动计算与人机交互第 5 页 共 5 页horn antennas have higher gains over all other antennas. An array of horn antennas provide high poweroutput required at BS. The space, size and power are constraints at the mobile device. Hence, moresimple patch antennas are suitable candidate for devices. Generally space, not th
34、e size, limits thedeployment of sophisticated smart antennas at both BS and MS. However, Samsungs experiments at28 GHz bands with patch antennas in popular handset have shown promising results. Cloud RadioAccess Network (C-RAN) resolves some of the major problems associated with increasing demands f
35、orhigh data rates. Wireless industry is working on measures to enhance network capacity by adding morecells, implementing MIMO techniques, establishing complex structure of HetNets and small celldeployment.However,inter-cellinterference,CAPitalEXpenditure(CAPEX)andOPeratingEXpenditure (OPEX) impedes
36、 these efforts. C-RAN offers to improve system architecture, mobility,coverage performance and energy efficiency while at the same time reducing the cost of networkdeployment and operation. C-RAN is based on fundamentals of centralization and virtualization. Thebaseband resources are pooled at BaseB
37、and Unit (BBU), situated at remote central office (not at thecell sites). In traditional cellular networks, the Internet Protocol, Multiprotocol functionality andEthernet are extended all the way to remote cell sites. A typical C-RAN architecture is with BBUs frommany remote sites centralized at a v
38、irtual BBU pool. This results in statistical multiplexing gains,energy efficient operations and resource savings. Virtual BBU pools further facilitate scalability, costreduction, integration of different services and reduction in time consumption for field trials. RemoteRadio Heads (RRH), comprising
39、 of transreciever components, amplifiers and duplexers enable digitalprocessing, analog-digital conversions, power amplification and filtering. RRHs are connected to BBUpool by single mode fibre of data rate higher than 1 Gbps. This simplified BS architecture is paving theway for dense 5G deployment by making it affordable, flexible and efficient. Powerful cloudcomputing ability can easily handle all complex control processes.
