外文翻譯蜂窩無線通信系統(tǒng)的研究

1、附錄 外文翻譯(原文)RESEARCH OF CELLULAR WIRELESS COMMUNATION SYSTEMAbstract1897, Marconi demonstrates the first practical application of the mobile radio communication, opening up a precedent of mobile communication, wireless communication in the modern sense was born. From that day onwards, the wireless co

2、mmunication technology is committed to achieving better communication quality, lower power consumption, smaller size and cheaper price. In the next 60 years, a number of landmark technological breakthroughs to promote the further development of mobile communications. Know the early 1980s, with the e

3、stablishment of a cellular mobile communication systems, mobile communication system has now entered a period of prosperity and development. The cellular system has experienced rapid exponential growth, clearly showing that wireless communication has a bright future.Cellular communication systems al

4、low a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed base stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband, or to a wideband microwav

5、e link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public Switched Telephone Network (PSTN). Similarly, communications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency di

6、vision multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or spatial division multiple access (SDMA).1 IntroductionA wide variety of wireless communication systems have been developed to provide access to the communications infrastructure for mobile o

7、r fixed users in a myriad of operating environments. Cellular mobile communication system by the exchange of Network Subsystem (NSS), the wireless base station subsystem (BSS) and mobile station (MS) has three major components. Switched network subsystem (NSS) completion of the exchange functional a

8、nd customer data, and mobility management, security management database functionalityMost of todays wireless systems are based on the cellular radio concept. Cellular communication systems allow a large number of mobile users to seamlessly and simultaneously communicate to wireless modems at fixed b

9、ase stations using a limited amount of radio frequency (RF) spectrum. The RF transmissions received at the base stations from each mobile are translated to baseband, or to a wideband microwave link, and relayed to mobile switching centers (MSC), which connect the mobile transmissions with the Public

10、 Switched Telephone Network (PSTN). Similarly, communications from the PSTN are sent to the base station, where they are transmitted to the mobile. Cellular systems employ either frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), or

11、 spatial division multiple access (SDMA) .Cellular wireless network due to its sophisticated networking technology, good coverage and reasonable cost of network construction has been the largest range of applications. GSM / GPRS, CDMA1X, and WCDMA, CDMA2000, and TDS-CDMA cellular radio network of th

12、e areas. The first generation of mobile communication system is characterized by: frequency division multiple access, analog modulation and demodulation, the frequency of low resource utilization, system capacity is low, serious interference, poor communication quality, and large terminal equipment.

13、 MS: Mobile Station, the users mobile terminal. BSS: Base Station Subsystem, including a base station controller BSC and base stations starting the BTS. BTS is responsible for the mobile station via the air interface communication; BSC is responsible for controlling one or more of the BTS. MSC: Mobi

14、le Switching Center, responsible for one or more of the BSS. Completion of the MS mobility management and business as well as the PSTN exchange. HLR, VLR is: are responsible for the records to the local user information registered in the local and roaming user information in the field. MSC through t

15、hese two databases to user mobility management and the correct exchange of the user service. The EIR, AUC: mobile devices, and user authentication center, responsible for the management of user rights. Obviously, the core of the GSM wireless network for the MSC by the MSC, VLR and HLR, to complete a

16、 voice call business circuit-switched mobile station access and mobility management. GPRS / GSM dual-mode mobile station, mobile station (MS), GSM base stations (BSS) subsystem made the appropriate hardware and software extensions. Introduced in the core network, the SGSN (and the GGSN two new netwo

17、rk device node SGSN,) GGSN logo both on the 7th signaling address and data GGSN IP address of GSN (SGSN or GGSN), the communication between using the IP GSN and MSC, HLR, and other entities of communication No. 7 signaling address.CDMA its market fundamentals in the United States. Europes second-gen

18、eration mobile communication system uses a TDMA standard, later developed into todays GSM network.Relative to the second-generation GSM network, GPRS network multiple components of the adjustment of the function module of the new features include: (1) mobile station (MS) must be GPRS or GPRS / GSM d

19、ual-mode mobile station. The original GSM network is only used as a voice call: GSM upgrade to the GPRS network, the MS with GPRS network to transmit voice packet switching circuit switching and transmission of data in two ways, and therefore more diverse functions and purposes. (2) the original GSM

20、 base stations (BSS) subsystem made the appropriate hardware and software extensions, base transceiver stations BTS units still only connected with the base station controller BSC, no new hardware interfaces, only an increase in the BTS software unit (CCU), the original BTS of the GSM network for th

21、e GPRS network. BSC is still connected at the same time many of the BTS, BSC is not only the need for software upgrades for the additional packet processing capabilities, but also increase the hardware interface of the connected with the SGSN Packet Control Unit (PCU). In the GPRS network, the wirel

22、ess signal issued by the MS for data or voice in two ways, responsible for the identification signal from the BTS data form: If the only voice information from the BSC to transfer the data to the MSC (which plays the voice switch role); containing data from the PCU in the BSC new interface, separate

23、d from the voice services to data services and data transmission to the SGSN, to control the allocation of the radio channel. (3) software that supports GPRS network switching subsystem (SS) (such as HLR, VLR, MSC, etc.), original equipment. (4) the introduction of the SGSN and GGSN of two new netwo

24、rk equipment in the core network nodes, thereby increasing the data-based voice services on the basis of business.Wireless communication links experience hostile physical channel characteristics,such as time-varying multipath and shadowing due to large objects in the propagation path. In addition, t

25、he performance of wireless cellular systems tends to be limited by interference from other users, and for that reason, it is important to have accurate techniques for modeling interference. These complex channel conditions are difficult to describe with a simple analytical model, although several mo

26、dels do provide analytical tractability with reasonable agreement to measured channel data . However, even when the channel is modeled in an analytically elegant manner, in the vast majority of situations it is still difficult or impossible to construct analytical solutions for link performance when

27、 error control coding, equalization, diversity, and network models are factored into the link model. Simulation approaches, therefore, are usually required when analyzing the performance of cellular communication links.In a wireless communication system, there are three basic mechanisms of signal pr

28、opagation: reflection, diffraction and scattering. Reflection occur when electromagnetic waves encounter objects much larger than the wavelength, occur in the Earths surface, building and wall surface. Electromagnetic waves in the media of the different nature of the junction, there will be some ref

29、lection, in part through. The electric field intensity of the reflected wave and transmitted wave depends on the Fresnel reflection coefficient (the Fresnel). The reflection coefficient as a function of the material, and the polarity of the incidence angle and frequency of the incident. Diffraction

30、occurred in the wireless path between the receiver and the transmitter is blocked sharp edges. Mountain blocking secondary wave surface to walk on the space, including the blocking of the body on the back. In the high frequency band, diffraction and reflection depends on the shape of the object, and

31、 the diffraction point of the incident wave amplitude, phase and polarization of the situation. Diffraction makes radio signals around the Earths surface spread, can spread to the back of the obstacles.Signals are transmitted in the wireless channel is generally attributed to reflection, diffraction

32、 and scattering three basic means of communication, wireless signal, whether the former forward link or reverse link transmission, will in many ways by the physical channel. Due to the complexity and time variability of the radio channel, the signal through the wireless channel will be subject to al

33、l aspects of the attenuation loss. Overall, the impact of the channel on the wireless signal can be summed up for the free space path loss, shadow fading and multipath fading three. (1) shadow fading: shadowing mainly refers to the radio waves generated by the buildings block the shadow effect on th

34、e propagation path loss, reflecting the trend of the average received signal level in the medium range of ups and downs. Such loss is generally unique for wireless communication, the general statistical laws to comply with the lognormal distribution, the rate of change is slower than the rate of tra

35、nsmission of information. (2) multipath fading: multipath fading, also known as fast fading, reflecting the trend of the average level of the ups and downs in a small area to receive. The level normally comply with the Rayleigh, Rice, over Nakagami probability distribution, and its rate of change is

36、 faster than the slow fading. Fast fading can be divided into space selective fading, frequency selective fading and events selective fading. Three most important multi-path fading effect in wireless channels: rapid changes generated within a small spread of distance or time interval, the signal str

37、ength multipath fading; different path signal, the Doppler frequency shift caused by the random frequency changes and multipath propagation delay spread caused by multipath fading effect. Multipath fading of wireless channels can cause the signal to the expansion of different dimensions (time, frequ

38、ency, space) has a significant impact on the wireless communication signals.Liking wireless links, the system performance of a cellular radio system is most effectively modeled using simulation, due to the difficulty in modeling a large number of random events over time and space. These random event

39、s, such as the location of users, the number of simultaneous users in the system, the propagation conditions, interference and power level settings of each user, and the traffic demands of each user,combine together to impact the overall performance seen by a typical user in the cellular system. The

40、 aforementioned variables are just a small sampling of the many key physical mechanisms that dictate the instantaneous performance of a particular user at any time within the system. The term cellular radio system,therefore, refers to the entire population of mobile users and base stations throughou

41、t the geographic service area, as opposed to a single link that connects a single mobile user to a single base station. To design for a particular system-level performance, such as the likelihood of a particular user having acceptable service throughout the system, it is necessary to consider the co

42、mplexity of multiple users that are simultaneously using the system throughout the coverage area. Thus, simulation is needed to consider the multi-user effects upon any of the individual links between the mobile and the base station.The link performance is a small-scale phenomenon, which deals with

43、the instantaneous changes in the channel over a small local area, or small time duration, over which the average received power is assumed constant . Such assumptions are sensible in the design of error control codes, equalizers, and other components that serve to mitigate the transient effects crea

44、ted by the channel. However, in order to determine the overall system performance of a large number of users spread over a wide geographic area, it is necessary to incorporate large-scale effects such as the statistical behavior of interference and signal levels experienced by individual users over

45、large distances, while ignoring the transient channel characteristics. One may think of link-level simulation as being a vernier adjustment on the performance of a communication system, and the system-level simulation as being a coarse, yet important, approximation of the overall level of quality th

46、at any user could expect at any time.Cellular systems achieve high capacity (e.g., serve a large number of users) by allowing the mobile stations to share, or reuse a communication channel in different regions of the geographic service area. Channel reuse leads to co-channel interference among users

47、 sharing the same channel, which is recognized as one of the major limiting factors of performance and capacity of a cellular system. An appropriate understanding of the effects of co-channel interference on the capacity and performance is therefore required when deploying cellular systems, or when

48、analyzing and designing system methodologies that mitigate the undesired effects of co-channel interference. These effects are strongly dependent on system aspects of the communication system, such as the number of users sharing the channel and their locations. Other aspects, more related to the pro

49、pagation channel, such as path loss, shadow fading (or shadowing), and antenna radiation patterns are also important in the context of system performance, since these effects also vary with the locations of particular users. In this chapter, we will discuss the application of system-level simulation

50、 in the analysis of the performance of a cellular communication system under the effects of co-channel interference. We will analyze a simple multiple-user cellular system, including the antenna and propagation effects of a typical system. Despite the simplicity of the example system considered in t

51、his chapter, the analysis presented can easily be extended to include other features of a cellular system.2 Cellular Radio SystemSystem-Level Description：Cellular systems provide wireless coverage over a geographic service area by dividing the geographic area into segments called cells as shown in F

52、igure 2-1. Depending on the size of the service area, the cell in the cellular mobile communication system usually can be divided into four categories: the picocell (picocell), microcell(microcell), macrocells (macrocell), satellite beam (satellitebeam). This is called a hierarchicalcompared to cell

53、ular mobile communication systems, and conventional single-layer cellular mobile communication service area at the same time, the hierarchical cellular mobile communication systems can provide higher system capacity. Its basic coverage criteria for the lower layer of smaller service area of the cell

54、 layer covering the user density is relatively high in order to obtain a larger system capacity; a higher level of larger cell layer for large area (the user density is relatively low), continuous coverage and provide overflow redundant channel for the former.In addition, in order to avoid frequent

55、cell switch, to ensure the quality requirements of the different characteristics of mobile communication of the mobile station, layered cellular mobile communication systems, usually moving faster mobile coverage by the higher level cell layer provides services to mobilethe slower the mobile station

56、 is assigned to a low cell coverage layer.The available frequency spectrum is also divided into a number of channels with a group of channels assigned to each cell. Base stations located in each cell are equipped with wireless modems that can communicate with mobile users. Radio frequency channels u

57、sed in the transmission direction from the base station to the mobile are referred to as forward channels, while channels used in the direction from the mobile to the base station are referred to as reverse channels. The forward and reverse channels together identify a duplex cellular channel. When

58、frequency division duplex (FDD) is used, the forward and reverse channels are split in frequency. Alternatively, when time division duplex (TDD) is used, the forward and reverse channels are on the same frequency, but use different time slots for transmission.Figure 2-1 Basic architecture of a cellu

59、lar communications system High-capacity cellular systems employ frequency reuse among cells. This requires that co-channel cells (cells sharing the same frequency) are sufficiently far apart from each other to mitigate co-channel interference. Channel reuse is implemented by covering the geographic

60、service area with clusters of N cells, as shown in Figure 2-2, where N is known as the cluster size. The RF spectrum available for the geographic service area is assigned to each cluster, such that cells within a cluster do not share any channel . If M channels make up the entire spectrum available