【正文】 漫游。根據(jù)青藏鐵路列車的無線網(wǎng)絡(luò)需求，我們決定采用無線網(wǎng)狀網(wǎng)來實現(xiàn)語音通信，同時還可實現(xiàn)：According to the customer request, we established the munication system on the train. This language automatic exchange system has the general switchboard system function, the user through the wireless telephone (this plan uses the WIFI handset) is possible to munity on the train the intermunicating telephone, also the out wire phone call, and handset in all partments may automated roaming. According to the Qinghai and Tibet railroad train wireless network demand, we decided uses the wireless netted network to realize the munication, meanwhile may realize:實現(xiàn)列車內(nèi)部無線信號良好覆蓋 Realization train interior wireless signal good cover滿足乘客、列車工作人員在旅途中的無線上網(wǎng)需求Satisfies the passenger, the train staff wireless accesses the net in the journey needs提供WiFi語音業(yè)務(wù)，實現(xiàn)列車工作人員的內(nèi)部免費通話 Provides the WiFi pronunciation service to realize train staff39。s internal nonregistered call實現(xiàn)無線WIFI手機拔打任意外線電話realize to dial any external registered call實現(xiàn)VoIP無線終端接通外線Realization the VoIP wireless terminal to put through the out wire實現(xiàn)無線電話在車廂內(nèi)的自動漫游Realization radio telephone automated roaming in the partment傳輸鏈路完全采用無線鏈路互聯(lián)，并通過網(wǎng)狀鏈路實現(xiàn)備份功能 Transmission link pletely use the wireless link interconnection, and through netted link realizes backup function實現(xiàn)無線終端安全接入 Realization safely turns on the wireless實現(xiàn)無線網(wǎng)狀網(wǎng)網(wǎng)絡(luò)管理Realization wireless terminal manage本方案力求在滿足以上要求的同時，盡可能的符合當今無線網(wǎng)絡(luò)發(fā)展的方向，具備相當?shù)南冗M性和可擴充、可升級的能力。充分考慮網(wǎng)絡(luò)的可靠性、冗余能力、自愈能力，力求具有前瞻性，并充分考慮將來網(wǎng)絡(luò)能夠滿足向更高性能擴展的能力，如3G。 This plan makes every effort above satisfying to request, as far as possible conforms to now the wireless network development direction, has ability which suitable advantage、may expand and may promote. This design full considers network reliability, the redundant ability, the ability of recover, makes every effort to have foresightedness, and with the full consideration the network will be able to satisfy the ability which will expand to the high performance in future, such as 3G.技術(shù)選型Product Election 由于本電話通信系統(tǒng)是建立在列車上，如果采用傳統(tǒng)的有線電話系統(tǒng)則要敷設(shè)很多線纜，這在列車上不太現(xiàn)實，而且傳統(tǒng)的有線電話不能在列車內(nèi)自動漫游；如果采用目前技術(shù)成熟的PHS方式（類似于小靈通）有兩個方面的問題不能解決，一是自動漫游問題，由于車廂外殼是金屬制品，屏蔽性很強，漫游問題解決不了，另一個是速度問題，PHS系統(tǒng)在本列車要求的時速達160公里時通話性能很難保障。因此我們考慮采用無線網(wǎng)格技術(shù)（MESH）的無線解決方案。Because this telephone munication system is the establishment on the train, if used the traditional wire telephone system, it have to lay very many cables, this isn’t realistic on the train, moreover the traditional wire telephone cannot automated roaming in the train。 If selects the present mature technology PHS method ,has two questions not to be able to solve, one question is the automated roaming, because the partment outer covering is the metal product, shield very strong, the question of roaming is insolubility, another was the speed, the PHS system is difficult to safeguard which requested when this train reaches 160 kilometer/hour . Therefore we considered uses the MESH technology solution.目前對于無線網(wǎng)絡(luò)的建設(shè)可選擇的技術(shù)較多，但就青藏鐵路列車的實際情況，考慮到安全和性能的穩(wěn)定性以及平滑升級的需求，采用先進的無線網(wǎng)狀網(wǎng)技術(shù)是最符合當前建設(shè)實際需要的。以下對無線網(wǎng)狀網(wǎng)技術(shù)的先進性作簡單介紹。At present the technology which may choose regarding the wireless network construction are more, but on the Qinghai and Tibet railroad train actual situation, we considers the security and the performance stability as well as the smooth promotion demand, uses the advanced wireless netted network technology most conforms to the current construction actual need. Below makes the simple introduction to wireless netted network technology’s advantage. 無線Mesh網(wǎng)絡(luò)（無線網(wǎng)狀網(wǎng)絡(luò)）也稱為“多跳（multihop）”網(wǎng)絡(luò)，它是一種與傳統(tǒng)無線網(wǎng)絡(luò)完全不同的新型無線網(wǎng)絡(luò)技術(shù)。在傳統(tǒng)的無線局域網(wǎng)(WLAN)中，每個客戶端均通過一條與AP相連的無線鏈路來訪問網(wǎng)絡(luò)，用戶如果要進行相互通信的話，必須首先訪問一個固定的接入點(AP)，這種網(wǎng)絡(luò)結(jié)構(gòu)被稱為單跳網(wǎng)絡(luò)。而在無線Mesh網(wǎng)絡(luò)中，任何無線設(shè)備節(jié)點都可以同時作為AP和路由器，網(wǎng)絡(luò)中的每個節(jié)點都可以發(fā)送和接收信號，每個節(jié)點都可以與一個或者多個對等節(jié)點進行直接通信。The wireless Mesh network (wireless netted network) also is called multihop network, it is one kind of new wireless network technology which pletely differences with the traditional wireless network. In the traditional wireless local area network (WLAN) center, each customer end visits the network through with the AP connected wireless link, if user carries on mutually corresponds, he must first visit the fixed plugin point AP, this kind of network architecture is called singlehop network. But in the wireless Mesh network, any wireless equipment node may simultaneously used as AP and Router, each node in network may transmit and receive the signal, each node may carry on the direct munication with one or many coordinated node.這種結(jié)構(gòu)的最大好處在于：如果最近的AP由于流量過大而導(dǎo)致?lián)砣脑?，那么?shù)據(jù)可以自動重新路由到一個通信流量較小的鄰近節(jié)點進行傳輸。依此類推，數(shù)據(jù)包還可以根據(jù)網(wǎng)絡(luò)的情況，繼續(xù)路由到與之最近的下一個節(jié)點進行傳輸，直到到達最終目的地為止。這樣的訪問方式就是多跳訪問，正好適合列車一節(jié)一節(jié)的接力方式。The most advantage of this kind of structure lies in: If recent AP is congestion as a result of the oversized current capacity, then the data may automatic carry on the transmission again to a traffic flow smaller neighbor node. Infer from this, according to the network the situation. The data packet also may continue the route to carry on the transmission with recent next node, until arrives the final destination. Such visit way is multihop visit, suits a train relay way.與傳統(tǒng)的WLAN相比，無線Mesh網(wǎng)絡(luò)具有幾個無可比擬的優(yōu)勢：Compares with traditional WLAN, the wireless Mesh network has several inparable superiorities:（1）快速部署和易于安裝。安裝Mesh節(jié)點非常簡單，將設(shè)備從包裝盒里取出來，接上電源就行了。由于極大地簡化了安裝，用戶可以很容易增加新的節(jié)點來擴大無線網(wǎng)絡(luò)的覆蓋范圍和網(wǎng)絡(luò)容量。在無線Mesh網(wǎng)絡(luò)中，不是每個Mesh節(jié)點都需要有線電纜連接，這是它與有線AP最大的不同。Mesh的設(shè)計目標就是將有線設(shè)備和有線AP的數(shù)量降至最低，因此大大降低了總擁有成本和安裝時間，僅這一點帶來的成本節(jié)省就是非?？捎^的。無線Mesh網(wǎng)絡(luò)的配置和其他網(wǎng)管功能與傳統(tǒng)的WLAN相同，用戶使用WLAN的經(jīng)驗可以很容易應(yīng)用到Mesh網(wǎng)絡(luò)上。（1）Fast deployment and easy to install. Installs the Mesh node extremely simply, takes out the equipment from the packing box, and meets the power source to be good. Because the installment is enormously simplified, the user may be very easy to increase the new node to expand the cover scope and the network capacity of the wireless network. In the wireless Mesh network, not each Mesh node needs the wired electric cable connection. This is the most difference with the wired AP. The Mesh design goal is falls