在我们的 J2ME 应用程序中使用 USSD 命令的目的是什么？这可能吗？
我听说Mobile中有USSD命令，但我不知道它是什么？我在谷歌上搜索了另外两个网站。我不明白。请任何了解 USSD 命令的人与我分享。
当我们在 j2me midp 2.0 应用程序开发中使用 USSD 命令时，它有何用处？
请建议我一些有用的 URL，以正确获取此信息。
另外，我也想在这里了解 AT 命令？
谢谢&问候， 萨拉瓦南
I heard there is USSD Commands in Mobile.But i dont know what it is? i was googling two more sites.i did not understand it.Please anybody having knowledge about USSD Commands, share with me.
How it is useful when we using USSD Commands with our j2me midp 2.0 application development?
Please suggest me some useful URL's to get this properly.
Also, i would like to here about AT Commands too?
Thanks & Regards,
P.SARAVANAN
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USSD 是非结构化补充服务数据。
GSM 对USSD 的语法（即消息传输）进行了标准化，但并未对语义进行标准化（即USSD 的用途取决于网络运营商）。
USSD 应用请求/响应模式。用户发送 USSD 请求，该请求由网络处理并最终得到 USSD 响应。简而言之，USSD 允许最终用户发送数字命令。这些命令通过 SS7 信令堆栈内的协议功能从移动设备传输到移动网络 MSC（移动交换中心，控制移动网络的网络节点）。网络运营商配置 MSC 来处理特定的 USSD 请求，通常将它们转发到各种其他网络元件。其中有：
HLR（归属位置寄存器，用户数据库）用于打开/关闭电话服务。
IN（智能网、实时计费平台等）预付费充值凭证管理系统
USSD 网关，用于将 USSD 消息分支到外部系统。
然后，这些网络元件生成 USSD 响应，并将其传输回用户。
通过以下方式使用 J2ME 中的 USSD：
支持 JSR 120（无线消息 API）的设备。请查阅制造商开发文档或设备数据库以检查涵盖哪些设备。
通过串行接口仿真的 AT 命令 (AT+CUSD)。
USSD is Unstructured Supplementary Service Data.
GSM standardizes on the syntax (i.e. message transport) of USSD but not on the semantics (i.e. what one can do with USSD is network-operator-specific).
USSD applies a request/response pattern. A user sends a USSD request which is processed by the network and eventually answered with an USSD reponse. In a nutshell, USSD allows an end user sending numerical commands. These commands are transported by protcol functionality within the SS7 signalling stack from the mobile device to the mobile network MSC (mobile switching center, the nework node controlling the mobile network). The network operator configures the MSC to handle specific USSD requests, typically to forward them to various other network elements. Among them are:
HLR (home location register, the user database) to switch on/off telephony services.
IN (intelligent network, the realtime billing platform, among others) voucher management system for prepaid top-up.
USSD gateway to branch out USSD messages to external systems.
These network elements then generate USSD responses which are transported back to the user.
Using USSD from J2ME is offered via:
Devices supporting JSR 120 (Wireless Messaging API). Consult manufacturers development documentation or device databases to check which devices are covered.
AT command (AT+CUSD) via serial interface emulation.
用户在手机键盘上撰写一些消息（通常相当神秘）。
电话将其发送到电话公司网络，由专用于 USSD 的计算机接收。
这台计算机的答案将发送回手机。
答案可以在电话屏幕上看到，但通常是非常基本的演示。
通过 USSD 发送的消息并未由任何标准化机构定义，因此每个网络运营商都可以实施其认为适合其客户的任何内容。
The user composes some message—usually rather cryptic—on the phone keyboard.
The phone sends it to the phone company network, where it is received by a computer dedicated to USSD.
The answer from this computer is sent back to the phone.
The answer could be seen on the phone screen, but it is usually with a very basic presentation.
The messages sent over USSD are not defined by any standardization body, so each network operator can implement whatever it finds suitable for its customers.