外文翻譯---通用分組無線服務(wù)技術(shù)

1、<p>　　General Packet Radio Service</p><p>　　General packet radio service (GPRS) is a packet oriented mobile data service available to users of the 2G cellular communication systems global system for mob

2、ile communications (GSM), as well as in the 3G systems. In 2G systems, GPRS provides data rates of 56-114 kbit/s.</p><p>　　GPRS data transfer is typically charged per megabyte of traffic transferred, while d

3、ata communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched se

4、rvice, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection for non-mobile users.</p><p>　　2G cellular systems combined with GPRS are often described

5、as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused time division multiple access (TDMA) channels in, for examp

6、le, the GSM system. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that GSM is the only kind of network where GPRS is

7、 </p><p>　　GPRS was developed as a GSM response to the earlier CDPD and i-mode packet switched cellular technologies.</p><p>　　Technical overview</p><p>　　Services offered</p>

8、<p>　　GPRS extends the GSM circuit switched data capabilities and makes the following services possible:</p><p>　　"Always on" internet access </p><p>　　Multimedia messaging serv

9、ice (MMS) </p><p>　　Push to talk over cellular (PoC/PTT) </p><p>　　Instant messaging and presence—wireless village </p><p>　　Internet applications for smart devices through wireless

10、 application protocol (WAP) </p><p>　　Point-to-point (P2P) service: inter-networking with the Internet (IP) </p><p>　　If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages

11、 per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute.</p><p>　　Protocols supported</p><p>

12、　　GPRS supports the following protocols:</p><p>　　internet protocol (IP). In practice, mobile built-in browsers use IPv4 since IPv6 is not yet popular. </p><p>　　point-to-point protocol (PPP). I

13、n this mode PPP is often not supported by the mobile phone operator but if the mobile is used as a modem to the connected computer, PPP is used to tunnel IP to the phone. This allows an IP address to be assigned dynamica

14、lly to the mobile equipment. </p><p>　　X.25 connections. This is typically used for applications like wireless payment terminals, although it has been removed from the standard. X.25 can still be supported o

15、ver PPP, or even over IP, but doing this requires either a network based router to perform encapsulation or intelligence built in to the end-device/terminal; e.g., user equipment (UE). </p><p>　　When TCP/IP

16、is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone during cell handover (when you move from one cell to another). TCP handles any packet loss (e.g. du

17、e to a radio noise induced pause) resulting in a temporary throttling in transmission speed.</p><p><b>　　Hardware</b></p><p>　　Devices supporting GPRS are divided into three classes:

18、</p><p><b>　　Class A :</b></p><p>　　Can be connected to GPRS service and GSM service (voice, SMS), using both at the same time. Such devices are known to be available today. </p&g

19、t;<p><b>　　Class B :</b></p><p>　　Can be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GP

20、RS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B. </p><p><b>　　Class C :</b></p><p&

21、gt;　　Are connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service. </p><p>　　A true Class A device may be required to transmit on two different

22、 frequencies at the same time, and thus will need two radios. To get around this expensive requirement, a GPRS mobile may implement the dual transfer mode (DTM) feature. A DTM-capable mobile may use simultaneous voice an

23、d packet data, with the network coordinating to ensure that it is not required to transmit on two different frequencies at the same time. Such mobiles are considered pseudo-Class A, sometimes referred to as "simple&

24、lt;/p><p>　　USB GPRS modems use a terminal-like interface USB 2.0 and later, data formats V.42bis, and RFC 1144 and external antennas. Modems can be added as cards (for laptops) or external USB devices which ar

25、e similar in shape and size to a computer mouse.</p><p>　　Coding schemes and speeds</p><p>　　The upload and download speeds that can be achieved in GPRS depend on a number of factors such as:<

26、;/p><p>　　the number of BTS TDMA time slots assigned by the operator </p><p>　　the maximum capability of the mobile device expressed as a GPRS multislot class </p><p>　　the channel enc

27、oding used summarised in the following table. </p><p>　　The least robust, but fastest, coding scheme (CS-4) is available near a base transceiver station (BTS), while the most robust coding scheme (CS-1) is u

28、sed when the mobile station (MS) is further away from a BTS.</p><p>　　Using the CS-4 it is possible to achieve a user speed of 20.0 kbit/s per time slot. However, using this scheme the cell coverage is 25% o

29、f normal. CS-1 can achieve a user speed of only 8.0 kbit/s per time slot, but has 98% of normal coverage. Newer network equipment can adapt the transfer speed automatically depending on the mobile location.</p>&l

30、t;p>　　In addition to GPRS, there are two other GSM technologies which deliver data services: circuit-switched data (CSD) and high-speed circuit-switched data (HSCSD). In contrast to the shared nature of GPRS, these in

31、stead establish a dedicated circuit (usually billed per minute). Some applications such as video calling may prefer HSCSD, especially when there is a continuous flow of data between the endpoints.</p><p>　　T

32、he following table summarises some possible configurations of GPRS and circuit switched data services.</p><p>　　Multiple access schemes</p><p>　　The multiple access methods used in GSM with GPRS

33、 are based on frequency division duplex (FDD) and TDMA. During a session, a user is assigned to one pair of up-link and down-link frequency channels. This is combined with time domain statistical multiplexing; i.e., pack

34、et mode communication, which makes it possible for several users to share the same frequency channel. The packets have constant length, corresponding to a GSM time slot. The down-link uses first-come first-served packet

35、scheduling,</p><p>　　Addressing</p><p>　　A GPRS connection is established by reference to its access point name (APN). The APN defines the services such as wireless application protocol (WAP) ac

36、cess, short message service (SMS), multimedia messaging service (MMS), and for Internet communication services such as email and World Wide Web access.</p><p>　　In order to set up a GPRS connection for a wir

37、eless modem, a user must specify an APN, optionally a user name and password, and very rarely an IP address, all provided by the network operator.</p><p><b>　　Usability</b></p><p>　　

38、The maximum speed of a GPRS connection offered in 2003 was similar to a modem connection in an analog wire telephone network, about 32-40 kbit/s, depending on the phone used. Latency is very high; round-trip time (RTT) i

39、s typically about 600-700 ms and often reaches 1 s. GPRS is typically prioritized lower than speech, and thus the quality of connection varies greatly.</p><p>　　Devices with latency/RTT improvements (via, fo

40、r example, the extended UL TBF mode feature) are generally available. Also, network upgrades of features are available with certain operators. With these enhancements the active round-trip time can be reduced, resulting

41、in significant increase in application-level throughput speeds.</p><p>　　通用分組無線服務(wù)技術(shù)</p><p>　　通用分組無線服務(wù)（GPRS）是一種面向服務(wù)的移動(dòng)分組數(shù)據(jù)，它提供給2G的蜂窩通信系統(tǒng)的使用者全球移動(dòng)通信系統(tǒng)（GSM），以及在3G系統(tǒng)。在2G系統(tǒng)中GPRS能提供56-114千比特/秒的數(shù)據(jù)傳輸速率。&

42、lt;/p><p>　　GPRS數(shù)據(jù)傳輸通常是收取每兆字節(jié)的傳輸流量，而數(shù)據(jù)通信是通過傳統(tǒng)的電路交換每分鐘的連接時(shí)間計(jì)費(fèi)的，不管用戶實(shí)際是處于使用狀態(tài)還是處于空閑狀態(tài)都是獨(dú)立的。 GPRS是一種非常有效的分組交換服務(wù)，而不是電路交換，能夠?yàn)榉且苿?dòng)用戶的連接保證一定的服務(wù)質(zhì)量。</p><p>　　與GPRS結(jié)合的2G蜂窩系統(tǒng)通常被描述為2.5G，就是一種在2G和3G之間的移動(dòng)電話技術(shù)。它提供了

43、中等速度的數(shù)據(jù)傳輸，利用閑置時(shí)分多址（TDMA）的渠道，例如，GSM系統(tǒng)。本來有一些想法擴(kuò)展到包括其他的GPRS標(biāo)準(zhǔn)，而是那些網(wǎng)絡(luò)正在轉(zhuǎn)換為使用的GSM標(biāo)準(zhǔn)，這樣的GSM網(wǎng)絡(luò)是唯一一種在正在使用的GPRS。 GPRS是在97年發(fā)布的基于GSM的整合和新版本。它最初是由歐洲電信標(biāo)準(zhǔn)協(xié)會(huì)（ETSI）的標(biāo)準(zhǔn)，但現(xiàn)在由第三代合作伙伴項(xiàng)目（3GPP）替代。</p><p>　　作為一個(gè)GSM ，GPRS較早的回答了CDPD

44、和i - mode分組交換蜂窩技術(shù)的發(fā)展。</p><p><b>　　技術(shù)概覽</b></p><p><b>　　提供的服務(wù)</b></p><p>　　GPRS的擴(kuò)展了GSM電路交換數(shù)據(jù)的能力，并有可能提出以下服務(wù)：</p><p>　　“永遠(yuǎn)在線”的互聯(lián)網(wǎng)接入</p><

45、p>　　多媒體短信服務(wù)（MMS）</p><p>　　手機(jī)一鍵通(PoC/PTT)</p><p>　　即時(shí)消息和出現(xiàn)無線村</p><p>　　通過無線應(yīng)用協(xié)議的互聯(lián)網(wǎng)應(yīng)用智能設(shè)備(WAP)</p><p>　　點(diǎn)對(duì)點(diǎn)（P2P）的服務(wù)：內(nèi)部局域網(wǎng)（IP）</p><p>　　如果通過GPRS使用短信，可能會(huì)實(shí)現(xiàn)

46、傳輸每分鐘約30封短信郵件。GSM傳輸速度大約是每封郵件6至10分鐘，GPRS短信的傳輸速度更快。</p><p><b>　　支持的協(xié)議</b></p><p>　　GPRS支持以下協(xié)議：</p><p>　　互聯(lián)網(wǎng)協(xié)議（IP）。在實(shí)踐中，手機(jī)內(nèi)置的瀏覽器使用的IPv4，因?yàn)镮Pv6尚未普及。</p><p>　　點(diǎn)對(duì)

47、點(diǎn)協(xié)議（PPP）。移動(dòng)電話運(yùn)營商往往不支持PPP這種模式，但如果是作為移動(dòng)連接的電腦調(diào)制解調(diào)器使用，PPP是用來連接IP和手機(jī)的。它允許動(dòng)態(tài)分配一個(gè)IP地址到移動(dòng)設(shè)備。</p><p>　　X.25連接。這通常是用于諸如無線支付終端的應(yīng)用，雖然它已經(jīng)從標(biāo)準(zhǔn)中刪除。 X.25仍然是可以的PPP，甚至超過IP，但這樣做要求是要么基于路由器來執(zhí)行封裝或在建的end-device/terminal情報(bào)網(wǎng)，例如，用戶設(shè)備（

48、UE）。</p><p>　　當(dāng)TCP / IP使用，每個(gè)電話可以有一個(gè)或多個(gè)IP地址分配。 GPRS將存儲(chǔ)和轉(zhuǎn)發(fā)的IP數(shù)據(jù)包到手機(jī)，在小區(qū)切換（當(dāng)你從一個(gè)細(xì)胞轉(zhuǎn)移到另一個(gè)），能夠處理在一個(gè)臨時(shí)節(jié)流造成的傳輸任何的TCP數(shù)據(jù)包丟失的問題（例如，由于無線電噪聲引起的停頓）。</p><p><b>　　硬件</b></p><p>　　設(shè)備支持的

49、GPRS可分為三類：</p><p><b>　　A類：</b></p><p>　　可以連接到GPRS服務(wù)和GSM服務(wù)（語音，短信），在同一時(shí)間使用兩種。這種設(shè)備到現(xiàn)在還是有效的。</p><p><b>　　B類：</b></p><p>　　可以連接到GPRS服務(wù)和GSM服務(wù)（語音，短信），在

50、一特定時(shí)間只使用一個(gè)或其他。當(dāng)GSM業(yè)務(wù)（語音通話或短信），GPRS服務(wù)暫停時(shí)，然后恢復(fù)的GSM服務(wù)（語音通話或短信）將自動(dòng)結(jié)束。大多數(shù)GPRS移動(dòng)設(shè)備屬于B類。</p><p><b>　　C類：</b></p><p>　　無論是連接到GPRS服務(wù)或GSM服務(wù)（語音，短信）。必須手動(dòng)切換之間的一種或其他服務(wù)。</p><p>　　一個(gè)真正的

51、A類設(shè)備可能需要在同一時(shí)間兩個(gè)不同的頻率間傳輸，因此將需要兩個(gè)收音機(jī)。為了解決這個(gè)昂貴的規(guī)定，一個(gè)GPRS手機(jī)可以實(shí)現(xiàn)雙傳輸模式（DTM）的特征。一個(gè)有DTM功能的手機(jī)可能會(huì)建立語音和分組數(shù)據(jù)，使之協(xié)調(diào)以確保它不需要在同一時(shí)間兩個(gè)不同的頻率時(shí)傳送。這種手機(jī)被認(rèn)為是偽類，有時(shí)也被稱為“簡(jiǎn)單的A類”的。有些網(wǎng)絡(luò)預(yù)計(jì)DTM將在2007年獲得支持。</p><p>　　GPRS的調(diào)制解調(diào)器使用的USB終端型接口的USB

52、2.0和更高版本，數(shù)據(jù)格式V.42bis和RFC 1144和外部天線。調(diào)制解調(diào)器可以增加一條，作為卡（筆記本電腦）或外部USB設(shè)備是在形狀和大小，類似電腦鼠標(biāo)。</p><p><b>　　編碼方案和速度</b></p><p>　　可以在GPRS實(shí)現(xiàn)的上傳和下載速度取決于很多因素，如以下：</p><p>　　輸血服務(wù)中心的TDMA的運(yùn)營商分

53、配的時(shí)間槽數(shù)</p><p>　　作為一個(gè)GPRS多時(shí)隙級(jí)表示最高性能的移動(dòng)設(shè)備</p><p>　　通道編碼使用總結(jié)如下表：</p><p>　　(CS-4)是最不強(qiáng)勁，但速度最快，編碼方案，由一個(gè)基站收發(fā)信臺(tái)（BTS）提供，而最強(qiáng)大的編碼方案是（CS - 1型），它使用移動(dòng)臺(tái)（MS）來進(jìn)一步脫離輸血服務(wù)中心。</p><p>　　使用CS

54、 – 4編碼方案有可能達(dá)到20.0千比特用戶速度/時(shí)間s每插槽。但是，使用此計(jì)劃的細(xì)胞正常范圍為25％。 CS - 1型可實(shí)現(xiàn)用戶只有8.0千比特的速度/時(shí)間s每插槽，但有98％的正常范圍。較新的網(wǎng)絡(luò)設(shè)備能夠自動(dòng)適應(yīng)不同的傳輸速度的移動(dòng)位置。</p><p>　　除了GPRS的，還有兩個(gè)其他的GSM技術(shù)，提供數(shù)據(jù)服務(wù)：電路交換數(shù)據(jù)（CSD）和高速電路交換數(shù)據(jù)（HSCSD）。相較于GPRS的共享性質(zhì)，這些不是建立一

55、個(gè)專用電路（通常是每分鐘計(jì)費(fèi)）。如視頻電話的某些應(yīng)用程序可能更喜歡HSCSD，尤其是當(dāng)有一個(gè)端點(diǎn)之間的數(shù)據(jù)源源不斷。</p><p>　　下表總結(jié)了一些可能的配置的GPRS和電路交換數(shù)據(jù)服務(wù)：</p><p><b>　　多址接入方案</b></p><p>　　多址的GSM與GPRS中使用的方法是基于頻分雙工（FDD）和時(shí)分多址。在會(huì)議期間，

56、用戶被分配到一個(gè)上行和下行線路頻率通道對(duì)。這是結(jié)合時(shí)域統(tǒng)計(jì)多路技術(shù)，也就是說，數(shù)據(jù)包通信方式，從而有可能為多個(gè)用戶共享同一頻道。有固定長度的數(shù)據(jù)包，對(duì)應(yīng)到GSM時(shí)隙。向下鏈接使用先到先得先到先得分組調(diào)度，而上行采用計(jì)劃非常相似，保留時(shí)隙ALOHA（的R -時(shí)隙ALOHA）。這意味著，時(shí)隙ALOHA（第S -時(shí)隙ALOHA）可以預(yù)訂查詢期間使用一階段的爭(zhēng)奪，然后實(shí)際的數(shù)據(jù)傳輸與使用動(dòng)態(tài)TDMA的先來先服務(wù)調(diào)度。</p>&l

57、t;p><b>　　尋址</b></p><p>　　一個(gè)GPRS連接，建立了參照其接入點(diǎn)名稱（APN）。該APN的定義，如無線應(yīng)用協(xié)議（WAP）的接入，短消息業(yè)務(wù)（SMS），多媒體信息服務(wù)的服務(wù)（MMS）的，和互聯(lián)網(wǎng)通信服務(wù)，如電子郵件和萬維網(wǎng)訪問。</p><p>　　為了建立一個(gè)無線調(diào)制解調(diào)器GPRS連接，用戶必須指定一個(gè)APN，可以選擇一個(gè)用戶名和密碼，

58、很少是一個(gè)IP地址，全部由網(wǎng)絡(luò)運(yùn)營商提供的。</p><p><b>　　可用性</b></p><p>　　在2003年提供的GPRS連接的最大速度是類似于在模擬電話線連接網(wǎng)絡(luò)的調(diào)制解調(diào)器，大約32-40千比特/秒，與在手機(jī)上使用的不同。等待時(shí)間非常高，往返時(shí)間（RTT）通常約600-700毫秒，而且往往達(dá)到1秒GPRS是典型的優(yōu)先低于講話，因此，連接的質(zhì)量差別很大