1. Field of the Invention
This invention relates in general to mobile phone networks, and more specifically, to a Hybrid Push-to-Talk (PTT) function in a mobile phone network.
2. Description of Related Art
Advanced voice services (AVS), also known as Advanced Group Services (AGS), such as two-way half-duplex voice calls within a group, also known as Push-to-Talk (PTT) or Press-to-Talk (P2T), as well as other AVS functions, such as Push-to-Conference (P2C) or Instant Conferencing, Push-to-Message (P2M), etc., are described in the commonly-assigned patent applications cross-referenced above and incorporated by reference herein. These AVS functions have enormous revenue earnings potential for wireless communications systems, such as cellular networks and personal communications systems (PCS) networks.
Currently, there are three major approaches employed in providing advanced voice services in wireless communications systems. One approach requires the installation of a dedicated private network, parallel to the wireless communications system, to support the group-based voice services. NEXTEL uses such a system, based on a solution developed by MOTOROLA known as IDEN. However, a dedicated private network is costly to install and maintain and is employed by a few public wireless carriers. Also, the IDEN system is non-standard, and hence cannot be used in standard wireless communications networks, such as those based on GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access).
Another approach is based on Voice over IP (VoIP) technologies. While this approach promises compliance with newer and emerging standards, such as GPRS (General Packet Radio Service), UMTS (Universal Mobile Telecommunications System), etc., it does not provide a solution for carriers employing wireless communications systems based on existing standards, such as GSM, CDMA, etc. However, even for the newer standards, solutions based on VoIP have serious drawbacks, including slower call setup, significant overhead, increased susceptibility to packet losses, low bit rate voice coders, and poor voice quality due to lack of Quality of Service (QoS) guarantees. Further, carrier deployment of networks capable of supporting the stringent demands of VoIP is spotty and far from ubiquitous. There is a need, instead, for solutions that require only minimal upgrades to the handset.
Still another approach is that defined in the commonly-assigned patent applications cross-referenced above and incorporated by reference herein. In this approach, advanced voice services are provided by a dispatch gateway (DG) or real-time exchange (RTX) that interfaces to the wireless communications system to provide the advanced voice services therein, wherein both the dispatch gateway and mobiles that use the advanced voice services communicate with each other using call setup and in-band signaling within the wireless communications system. This approach based on circuit switching solution provides the same voice quality as the underlying cellular network and hence has superior voice quality performance compared to solutions based on VoIP. However, in this approach the initial call setup time is dependent on the underlying cellular voice network.
Notwithstanding these innovations, there is a need in the art for improvements to the methods and systems for delivering the advanced voice services that comply with existing and emerging wireless standards and yet provide superior user experiences by utilizing the circuit switched solution for superior voice quality and an optimized call setup method for an overall superior user experience. The present invention satisfies this need.