手机在通话过程中改变小区称作：（）。

A:Handover B:Roaming C:Active

MAP信令中的“Provide Roaming Number”操作用于什么场合（）

A:HLR向MSC/VLR请求MSRN漫游号码 B:GMSC向HLR请求MSRN漫游号码 C:GMSC向MSC/VLR请求MSRN漫游号码 D:以上答案都不对

漫游（Roaming）是指MS从一个PLMN移动到另一个PLMN的过程。

When Melissa Mahan and her husband visited the Netherlands, they felt imprisoned by their tour bus. It forced them to see the city according to a particular route and specific schedule--but going off on their own meant missing out on the information provided by the guide. On their return home to San Diego, California, they started a new company called Tour Coupes. Now, when tourists in San Diego rent one of their small, brightly coloured three-wheeled vehicles, they are treated to a narration over the stereo system about the places they pass, triggered by Global Positioning System (GPS) satellite technology.
This is just one example of how GPS is being used to provide new services to tourists. "What we really have here is a technology that allows people to forget about the technology," says Jim Carrier of IntelliTours, a GPS tourism firm which began offering a similar service over a year ago in Montgomery, Alabama. The city is packed with sites associated with two important chapters in American history, the civil war of the 1860s and the civil-rights movement a century later. Montgomery has a 120-year-old trolley system, called the Lightning Route, which circulates around the downtown area and is mainly used by tourists. On the Lightning Route trolleys, GPS-triggered audio clips point out historical hotspots.
Other firms, such as CityShow in New York and GPS Tours Canada in Banff, Canada, offer hand-held GPS receivers that play audio clips for listening to while walking or driving. In South Africa, Europcar, a car-rental firm, offers a device called the Xplorer. As well as providing commentary on 2 000 points of interest, it can also warn drivers if they exceed the local speed limit.
If such services prove popular, the use of dedicated audio-guide devices could give way to a different approach. A growing number of mobile phones have built-in GPS or can determine their locations using other technologies. Information for tourists delivered via phones could be updated in real time and could contain advertisements. "Location-based services", such as the ability to call up a list of nearby banks or pizzerias, have been talked about for years but have never taken off. But aiming such services at tourists makes sense--since people are more likely to want information when in an unfamiliar place. It could give mobile roaming a whole new meaning.
When a traveler is in an unfamiliar place, ______.

A:mobile roaming will meet his needs. B:he wants to know something about it. C:Location-based services play a key role in his traveling. D:he must understand the roles of Location-based services.

When Melissa Mahan and her husband visited the Netherlands, they felt imprisoned by their tour bus. It forced them to see the city according to a particular route and specific schedule--but going off on their own meant missing out on the information provided by the guide. On their return home to San Diego, California, they started a new company called Tour Coupes. Now, when tourists in San Diego rent one of their small, brightly coloured three-wheeled vehicles, they are treated to a narration over the stereo system about the places they pass, triggered by Global Positioning System (GPS) satellite technology.
This is just one example of how GPS is being used to provide new services to tourists. "What we really have here is a technology that allows people to forget about the technology," says Jim Carrier of IntelliTours, a GPS tourism firm which began offering a similar service over a year ago in Montgomery, Alabama. The city is packed with sites associated with two important chapters in American history, the civil war of the 1860s and the civil-rights movement a century later. Montgomery has a 120-year-old trolley system, called the Lightning Route, which circulates around the downtown area and is mainly used by tourists. On the Lightning Route trolleys, GPS-triggered audio clips point out historical hotspots.
Other firms, such as CityShow in New York and GPS Tours Canada in Banff, Canada, offer hand-held GPS receivers that play audio clips for listening to while walking or driving. In South Africa, Europcar, a car-rental firm, offers a device called the Xplorer. As well as providing commentary on 2 000 points of interest, it can also warn drivers if they exceed the local speed limit.
If such services prove popular, the use of dedicated audio-guide devices could give way to a different approach. A growing number of mobile phones have built-in GPS or can determine their locations using other technologies. Information for tourists delivered via phones could be updated in real time and could contain advertisements. "Location-based services", such as the ability to call up a list of nearby banks or pizzerias, have been talked about for years but have never taken off. But aiming such services at tourists makes sense--since people are more likely to want information when in an unfamiliar place. It could give mobile roaming a whole new meaning.

A:mobile roaming will meet his needs. B:he wants to know something about it. C:Location-based services play a key role in his traveling. D:he must understand the roles of Location-based services.

What does the author wants to illustrate with Johnny roaming the streets

A:An instance of arbitrariness. B:A consequence of permissiveness. C:A prototype of classics. D:An example of irresponsibility.

When Melissa Mahan and her husband visited the Netherlands, they felt imprisoned by their tour bus. It forced them to see the city according to a particular route and specific schedule--but going off on their own meant missing out on the information provided by the guide. On their return home to San Diego, California, they started a new company called Tour Coupes. Now, when tourists in San Diego rent one of their small, brightly coloured three-wheeled vehicles, they are treated to a narration over the stereo system about the places they pass, triggered by Global Positioning System (GPS) satellite technology.
This is just one example of how GPS is being used to provide new services to tourists. "What we really have here is a technology that allows people to forget about the technology," says Jim Carrier of IntelliTours, a GPS tourism firm which began offering a similar service over a year ago in Montgomery, Alabama. The city is packed with sites associated with two important chapters in American history, the civil war of the 1860s and the civil-rights movement a century later. Montgomery has a 120-year-old trolley system, called the Lightning Route, which circulates around the downtown area and is mainly used by tourists. On the Lightning Route trolleys, GPS-triggered audio clips point out historical hotspots.
Other firms, such as CityShow in New York and GPS Tours Canada in Banff, Canada, offer hand-held GPS receivers that play audio clips for listening to while walking or driving. In South Africa, Europcar, a car-rental firm, offers a device called the Xplorer. As well as providing commentary on 2 000 points of interest, it can also warn drivers if they exceed the local speed limit.
If such services prove popular, the use of dedicated audio-guide devices could give way to a different approach. A growing number of mobile phones have built-in GPS or can determine their locations using other technologies. Information for tourists delivered via phones could be updated in real time and could contain advertisements. "Location-based services", such as the ability to call up a list of nearby banks or pizzerias, have been talked about for years but have never taken off. But aiming such services at tourists makes sense--since people are more likely to want information when in an unfamiliar place. It could give mobile roaming a whole new meaning.

A:mobile roaming will meet his needs B:he wants to know something about it C:Location-based services play a key role in his traveling D:he must understand the roles of Location-based services

IEEE 802.11定义了无线局域网的两种工作模式，其中的 (1) 模式是一种点对点连接的网络，不需要无线接入点和有线网络的支持，用无线网卡连接的设备之间可以直接通信。IEEE 802.11的物理层规定了3种传输技术，即红外技术、直接序列扩频(DSSS)和跳频扩频(FHSS)技术，后两种扩频技术都工作在 (2) 的ISM频段。IEEE 802.11MAC层具有多种功能，其中分布式协调功能采用的是 (3) 协议，用于支持突发式通信，而用于支持多媒体应用的是 (4) 功能，在这种工作方式下，接入点逐个询问客户端，被查询到的客户端通过接入点收发数据。最新提出的IEEE802.11a标准可提供的最高数据速率为 (5) 。

A:Roaming B:AdHoc C:Infrastructure D:DiffuselR