VoWLAN

VoWLAN (Voice over WLAN) is a method of sending voice information in digital form over a wireless broadband network. Essentially, VoWLAN is VoIP delivered through wireless technology. The technology is sometimes called“VoWi-Fi”or “Wi-Fi VoIP”because it uses the IEEE 802.11 set of specifications (informally known collectively as Wi-Fi) for transporting data over wireless local area networks and the Internet.

VoWLAN requires a voice-enabled wireless device, most commonly a PDA or a“Wi-Fi handset,”which looks and operates like a cell phone, but sends voice as discrete data packets rather than an analog voice stream. Callers can also use a software-based phone, known as a softphone, that resides on devices including laptop and desktop computers. The VoWLAN system routes calls from the phone to a WLAN access point and then to a VoIP gateway or IP PBX. The call is sent to its appropriate destination within the private network or out onto the Internet or PSTN.

The VoWLAN system allows all regular functions and messaging applications available on wired phones to be available on the VoWLAN devices. Like VoIP, VoWLAN also contributes to cost efficiency. Because calls can be routed over the data network internally or over the Internet externally, mobile telephony costs can be eliminated or decreased significantly.

Major barriers to VoWLAN include inconsistent voice performance and the need for quality of service (QoS); slow and unreliable encryption and authentication; and the proprietary nature of current products. The IEEE and the Wi-Fi Alliance have been developing standards improvements to mitigate VoWLAN limitations. The recent 802.11i standard implemented intelligent security to speed up authentication while Roaming. Other upcoming standards enhancements include:

● The 802.11e standard will define QoS measures that will prioritize voice traffic using two methods, Wireless MultiMedia (WMM) and WMM Scheduled Access

● 802.11r will specify a fast-roaming protocol to minimize packet loss when users move from one access point to another within a WLAN

● 802.11k will include the Radio Resource Management protocol to enable a handset to pre-discover the conditions of the WLAN network and choose the best available paths.

VoWLAN is most frequently found in the retail, manufacturing and health care industries, where WLAN was adopted early and use has progressed quickly. In the long term, VoWLAN deployment is a significant step toward interoperability and seamless mobile connectivity between private WLANs and public wireless and cellular networks.

VoWLAN

VoWLAN(無(wú)線局域網(wǎng)電話)是一種在無(wú)線寬帶網(wǎng)絡(luò)上以數(shù)字形式發(fā)送聲音信息的方法。本質(zhì)上，VoWLAN是通過無(wú)線技術(shù)提供的IP電話。有時(shí)，此項(xiàng)技術(shù)被稱為VoWi-Fi或者Wi-Fi VoIP, 因?yàn)樗捎靡唤MIEEE 802.11規(guī)范(非正式地統(tǒng)稱為Wi-Fi)在無(wú)線局域網(wǎng)和因特網(wǎng)上傳送數(shù)據(jù)。

VoWLAN需要實(shí)現(xiàn)聲音的無(wú)線設(shè)備，最常用的是PDA(個(gè)人數(shù)字助理)或Wi-Fi手持設(shè)備，它們看上去很像手機(jī)電話，但它們是以離散的數(shù)字包而不是模擬的聲音流發(fā)送聲音的。呼叫者也能使用基于軟件的、留駐在便攜式和臺(tái)式計(jì)算機(jī)等設(shè)備中的電話，稱之為軟電話。VoWLAN系統(tǒng)將呼叫從電話機(jī)路由到無(wú)線局域網(wǎng)的接入點(diǎn)，然后路由到VoIP網(wǎng)關(guān)或IP電話小交換機(jī)。最終呼叫被送到專網(wǎng)中的目的地或者外送到因特網(wǎng)或傳統(tǒng)電話網(wǎng)。

VoWLAN系統(tǒng)使得在有線電話上能實(shí)現(xiàn)的所有常規(guī)功能和傳信應(yīng)用在VoWLAN設(shè)備上也能實(shí)現(xiàn)。VoWLAN與VoIP一樣，節(jié)約了成本。因?yàn)楹艚心茉趦?nèi)部的數(shù)據(jù)網(wǎng)或者外部的因特網(wǎng)上路由，所以能消除或者大大減少移動(dòng)電話的成本。

VoWLAN的主要障礙有聲音性能的不一致和需要服務(wù)質(zhì)量(QoS)保證，緩慢和不太可靠的加密和認(rèn)證，以及目前產(chǎn)品的專有性。IEEE和Wi-Fi聯(lián)盟一直在對(duì)標(biāo)準(zhǔn)進(jìn)行改進(jìn)，以減少VoWLAN的局限性。最新的802.11i標(biāo)準(zhǔn)實(shí)現(xiàn)了智能安全，提高了漫游時(shí)的認(rèn)證速度。其他將要問世的標(biāo)準(zhǔn)改進(jìn)還有：

● 802.11e標(biāo)準(zhǔn)定義利用了兩種方法，即利用無(wú)線多媒體(WMM)和WMM預(yù)定訪問使聲音流量?jī)?yōu)先化的QoS措施。

● 802.11r將制訂快速漫游協(xié)議，使用戶在無(wú)線局域網(wǎng)中從一個(gè)接入點(diǎn)移到另一個(gè)接入點(diǎn)時(shí)包丟失減至最小。

● 802.11k將包括無(wú)線電資源管理協(xié)議，以便使手機(jī)預(yù)先發(fā)現(xiàn)無(wú)線局域網(wǎng)的狀態(tài)和選擇最好的可用方式。

VoWLAN在零售、制造和衛(wèi)生行業(yè)最常見，這些行業(yè)較早采用無(wú)線局域網(wǎng)，發(fā)展很快。從長(zhǎng)遠(yuǎn)看，部署VoWLAN是朝著專用無(wú)線局域網(wǎng)和公共的無(wú)線網(wǎng)絡(luò)以及蜂窩網(wǎng)絡(luò)之間互操作和無(wú)縫移動(dòng)連接的關(guān)鍵一步。