๐ฉ๐ผ๐ช๐ถ๐๐ถ (๐ฉ๐ผ๐ถ๐ฐ๐ฒ ๐ผ๐๐ฒ๐ฟ ๐ช๐ถ-๐๐ถ) is a technology that allows users to make voice calls over a Wi-Fi instead of a cellular network.
Its Architecture is composed of:
๐ญ. ๐ช๐ถ-๐๐ถ ๐๐ฐ๐ฐ๐ฒ๐๐ ๐ก๐ฒ๐๐๐ผ๐ฟ๐ธ:
It can be any Wi-Fi access point, such as home routers, public Wi-Fi, or enterprise networks.
Does not process mobile signaling but provides the IP transport for voice data packets.
It could be:
๐ ๐จ๐ป๐๐ฟ๐๐๐๐ฒ๐ฑ ๐ก๐ฒ๐๐๐ผ๐ฟ๐ธ: When the Wi-Fi network is not managed by the mobile operator (e.g., public Wi-Fi hotspots or home networks).
๐ ๐ง๐ฟ๐๐๐๐ฒ๐ฑ ๐ก๐ฒ๐๐๐ผ๐ฟ๐ธ: one that is managed or approved by the operator (e.g., operator-controlled Wi-Fi hotspots or enterprise network.)
๐ ๐๐ถ๐ฟ๐ฒ๐ฐ๐ ๐ฉ๐ผ๐ช๐ถ๐๐ถ ๐๐ฐ๐ฐ๐ฒ๐๐: UE connects directly to the IMS core over Wi-Fi ๐๐ถ๐๐ต๐ผ๐๐ ๐ฒ๐ฃ๐๐.
๐ฎ. ๐๐๐ผ๐น๐๐ฒ๐ฑ ๐ฃ๐ฎ๐ฐ๐ธ๐ฒ๐ ๐๐ฎ๐๐ฎ ๐๐ฎ๐๐ฒ๐๐ฎ๐ (๐ฒ๐ฃ๐๐) or ๐ง๐ฟ๐๐๐๐ฒ๐ฑ ๐ช๐ถ๐ฟ๐ฒ๐น๐ฒ๐๐ ๐๐ฐ๐ฐ๐ฒ๐๐ ๐๐ฎ๐๐ฒ๐๐ฎ๐ (๐ง๐ช๐๐):
๐ฒ๐ฃ๐๐ acts as a secure interface b/n the untrusted Wi-Fi network & the operatorโs core network.
๐ Establishes an ๐๐ฃ๐๐ฒ๐ฐ ๐๐๐ป๐ป๐ฒ๐น with the userโs device for secure communication over Wi-Fi.
๐ Ensures authentication using credentials stored in the SIM (e.g., ๐๐ ๐ฆ๐) in collaboration with HSS and the AAA Server.
๐ง๐ช๐๐ is used when the Wi-Fi network is trusted by the mobile operator.
๐ It functions as a bridge b/n the Wi-Fi network and the operatorโs core network.
๐ It does not use IPsec tunnels like the ePDG. Instead, it relies on the inherent security of the managed Wi-Fi network.
๐ It supports direct access to the Packet Gateway (P-GW) without requiring an ๐ฒ๐ฃ๐๐.
๐ฏ. ๐๐ ๐ถ๐๐๐ถ๐ป๐ด ๐๐ผ๐ฟ๐ฒ ๐ก๐ฒ๐๐๐ผ๐ฟ๐ธ ๐ฒ๐น๐ฒ๐บ๐ฒ๐ป๐๐ with ๐ฉ๐ผ๐ช๐ถ๐๐ถ adaptation to operate with the new interfaces, protocols & authentication capability. This includes (๐๐ ๐ฆ, ๐๐ฆ๐ฆ, ๐๐๐, ๐ฃ-๐๐ช, ๐ ๐๐ช, ๐ฃ๐๐ฅ๐.)
๐ฐ. ๐ฉ๐ผ๐ช๐ถ๐ณ๐ถ ๐ฐ๐ฎ๐ฝ๐ฎ๐ฏ๐น๐ฒ ๐๐๐ฒ๐ฟ ๐ฑ๐ฒ๐๐ถ๐ฐ๐ฒ (๐จ๐):
The userโs smartphone or tablet, equipped with VoWiFi functionality ( ๐ฆ๐๐ฃ ๐ผ๐๐ฒ๐ฟ ๐ฎ๐ป ๐๐ฃ๐๐ฒ๐ฐ ๐๐๐ป๐ป๐ฒ๐น) to the ๐ฒ๐ฃ๐๐.
๐๐ฎ๐น๐น ๐๐น๐ผ๐ ๐ถ๐ป ๐ฉ๐ผ๐ช๐ถ๐๐ถ
๐ญ. ๐๐ฒ๐๐ถ๐ฐ๐ฒ ๐๐๐๐ต๐ฒ๐ป๐๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป:
The device connects to the ๐ฒ๐ฃ๐๐ over Wi-Fi(permitted by AAA), creating a secure IPsec tunnel or directly to the ๐ง๐ช๐๐ in the case of ๐๐ฟ๐๐๐๐ฒ๐ฑ WiFi.
Use ๐๐ฆ๐ฆ to authenticate the SIM credentials.
๐ฎ. ๐๐ ๐ฆ ๐ฅ๐ฒ๐ด๐ถ๐๐๐ฟ๐ฎ๐๐ถ๐ผ๐ป:
Once authenticated, the ๐จ๐ registers with the IMS core using ๐ฆ๐๐ฃ.
๐ฏ. ๐๐ฎ๐น๐น ๐๐๐๐ฎ๐ฏ๐น๐ถ๐๐ต๐บ๐ฒ๐ป๐:
When a call is made, ๐ฆ๐๐ฃ sets up the session b/n the calling & receiving parties.
Voice data flow via Wi-Fi network to the ๐๐ ๐ฆ ๐ฐ๐ผ๐ฟ๐ฒ & the recipient.
๐ฐ. ๐๐ฎ๐ป๐ฑ๐ผ๐๐ฒ๐ฟ:
If the user moves out of Wi-Fi coverage, the call seamlessly transitions to ๐ฉ๐ผ๐๐ง๐ via the ๐๐ ๐ฆ core, maintaining continuity or ๐ฆ๐ฅ๐ฉ๐๐ may be used to handover to legacy ๐๐ฆ.