SMS and USSD Signaling for WiFi Cellular Hand-off
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Solution Overview
Problem
Current methods for hand-off between WiFi and cellular networks in Dual Transfer Mode (DTM) handsets lack standardized solutions, relying heavily on cellular network infrastructure and signaling, which is complex and not widely adopted due to compatibility issues and reliance on specific cellular network upgrades.
Innovation Solution
The use of Short Message Service (SMS) and Unstructured Supplementary Services Data (USSD) channels for call control signaling, allowing hand-off between WiFi and cellular domains, with SMS providing confirmation of message receipt and USSD supporting bidirectional messaging for seamless hand-off, decoupling reliance on cellular network infrastructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cellular network infrastructure is used for hand-off control, then call control capability is provided, but device complexity and network dependency increase
Solution Approach 1:
The patent introduces SMS and USSD as intermediary signaling mechanisms between the handset and the cellular network. These messaging channels act as mediators that carry hand-off control information without requiring complex direct signaling protocols, thereby simplifying the interaction while maintaining reliable hand-off control capability.
Solution Approach 2:
The patent replaces complex direct cellular signaling mechanisms with simpler SMS/USSD messaging protocols. Instead of using complex call control signaling directly over the cellular network, the system substitutes these with standardized text-based messaging channels that are easier to implement and more universally supported.
2Adaptability or versatility
If standardized hand-off methods are implemented, then network independence is improved, but existing cellular infrastructure compatibility deteriorates
Solution Approach 1:
The patent leverages the universal availability of SMS and USSD services in cellular networks to provide hand-off control functionality. These messaging channels are already universally supported across different cellular networks and devices, allowing the system to achieve network independence without requiring specialized infrastructure or complex compatibility measures.
Solution Approach 2:
The patent changes the signaling parameter from complex direct call control messages to standardized SMS/USSD text messages. This parameter transformation allows the system to use existing cellular infrastructure for hand-off control while maintaining simplicity and universality, as SMS and USSD are standard features of cellular networks that require no additional infrastructure.
Data Source
AI summary
The invention makes use of the Short Message Service (SMS) or Unstructured Supplementary Services Data (USSD) capabilities present in today's cellular networks as a means of providing call control and presence signalling and, in particular, for providing the means of effecting hand-off at least from/to the cellular domain to/from the WiFi domain. SMS and USSD were originally designed as engineering channels, but SMS has become highly popular as a service in its own right. SMS and USSD are built into all existing cellular (GSM, CDMA etc.) network and predate the current GPRS overlay. In particular, SMS and USSD can be used while a call may be active in the cellular domain, and a handset may send and receive such messages, with an additional facility which may be used by the invention of receiving acknowledgements of successful receipt of an outgoing SMS by the messaged party—effectively a confirmation from the network. The present invention proposes to use SMS or USSD as a means of an adjunct call control and presence signalling in the cellular domain between a handset and the SIP domain.