Circuit-switched分析.PDFVIP

Circuit-switched fallback. White Paper In collaboration with: Qualcomm Circuit-switched fallback. The first phase of voice evolution for mobile LTE devices. 1 LTE Growth and Challenges to switch from the PS network to the CS network. This solution is universally accepted for LTE-3GPP network The 3GPP Long Term Evolution (LTE) high-speed, high- interworking solutions and is the focus of this paper. capacity data standard for mobile devices is on its way to becoming a globally deployed standard. Launched com- With circuit-switched fallback, when the user’s device is mercially in late 2009, first quarter 2012 deployment and operating in LTE (data connection) mode and a call comes planning worldwide has expanded as reflected in Figure 1. in, the LTE network pages the device. The device responds with a special service request message to the network, As an all-IP, data-only transport technology using packet and the network signals the device to move (fall back) to switching, LTE introduces challenges to satisfying estab- 2G/3G to accept the incoming call. Similarly for outgoing lished quality of service expectations for circuit-switched calls, the same special service request is used to move mobile telephony and SMS for LTE-capable smartphones, the device to 2G/3G to place the outgoing call. while being served on the LTE network.