Mobility Development Group NewsletterJune 2015
Spring 2015 Mobility Global Summit Recap
The Spring 2015 Mobility Global Summit was a complete success! More than 60 attendees from 32 companies came together and discussed LTE deployments, Voice over WiFi and M2M services. A special thanks to our host Cisco, our sponsor Qualcomm, the speakers and panelists for their excellent topical presentations and to the members and other attendees for their participation in our interactive forum to address the challenges and opportunities that we are all facing at this exciting and transformational time in the wireless industry.
Presentations are now available for download on our website.
Bridging the Gap Circuit Switched Voice on the path to VoLTE…and beyond
By Tony Lee, VIA Telecom and Asif Hamidullah, Mobility Development Group
As wireless operators worldwide continue to deploy 4G LTE networks, and the adoption of smart phones continues to proliferate globally, a very large focus has been put on the amount of new data being generated and consumed via innovative applications, and the types of data speeds that are achievable in 4G networks. One of the key areas not so publicly discussed is how voice in a packet switched environment is being supported.
Consumers have come to expect voice to be a core service on a mobile device, and unlike other data applications that are bringing new means of communication to smart phone users, voice services from an end user perspective have not changed very much over the years. Continued support of voice services in an LTE environment has, however, proven to be far more challenging than any other type of data application. While the telecommunications industry in general is in agreement that all paths lead to Voice over LTE (VoLTE) where voice is treated as another, albeit crucial data application, the initial results for VoLTE have indicated that further work is required to ensure the performance is at least at par, if not better, than Circuit Switched voice. Quality of Service (QoS) is critical, as packet loss and latency for a voice application is not as forgiving as other data applications. Operators have to ensure for various types of voice services whether for general consumer use or for specialty use, such as emergency services, that QoS is available and an appropriate level of service is maintained.
Operators that have traditionally deployed 3GPP based networks have relied on their 3G WCDMA/HSPA and/or 2G GSM networks to continue to provide CS voice services on LTE devices using Circuit Switched Fallback (CSFB) as defined by the 3GPP. cdma2000 operators, on the other hand, have been required to support both cdma2000 and LTE technologies in their multi-mode devices, and a major aspect of ongoing development in the cdma2000 community is on the interworking between cdma2000 and LTE, and especially in the areas of voice communications.
Simultaneous Voice and LTE Data (SVLTE) – Dual Radio Solutions
Early solutions to support voice on cdma2000-LTE devices involved deployment of Simultaneous Voice and LTE (SVLTE), a dual-radio solution where devices support separate radios for cdma2000 and LTE, each monitoring and communicating with their respective networks over different radio links. While this allows some new capabilities such as serving a voice call on 1X while at the same time using LTE data, there are significant performance impacts in the area of battery life and overall cost of the device for supporting and running two radios. SVLTE devices also have to support very complicated algorithms to ensure the device doesn’t exceed SAR requirements, a critical component to meeting regulatory requirements on health and safety. Device form factor also becomes an issue as additional components required for the two radios directly impact the ever shrinking real estate in most smart phones commercialized today.
e1X-CSFB – Intelligent Communication between 3G & 4G
While 3GPP operators seamlessly use CSFB from LTE to support 3G CS Voice services, operators with cdma2000 networks have the option of deploying enhanced 1X-CSFB (e1X-CSFB), which leverages the LTE network to help facilitate a faster transition from LTE to cdma2000 when processing a voice call or SMS. By using Generic Circuit Services Notification Application (GCSNA), S102 tunneling and new SIB8 messaging parameters to channel cdma2000 related information between the device and cdma2000 network via the LTE eNB, faster call setup and call process times can be achieved, while minimizing any network performance impacts on LTE. Coupled with advanced vocoders like EVRC-NW codec that provides HD Voice capability, consumers will notice a significant improvement in voice call quality. e1X-CSFB does, however, come with an added cost requiring network upgrades to support S102, as well as a greater signaling load on the network and additional complexity on the device.
Hybrid 1X & LTE – The best of both worlds?
More recently, an alternate mechanism to support 1X CS Voice and SMS while on LTE is emerging in the form of Hybrid 1X & LTE or Single Radio – LTE (SR-LTE) as it is more commonly known. Unlike SVLTE, a single radio solution allows for lower cost of materials, and better power management, and unlike e1X-CSFB, it is a device based solution where no costly network upgrades are required. Hybrid 1X & LTE uses a single radio, and in some implementations leverages the existing Rx Diversity Antenna chain to monitor the 1X network while the primary Rx path is used to monitor the LTE network. In other cases, a single Rx path is used to monitor both networks with the device tuning away from one network to another periodically based on a predetermined algorithm. As cdma2000 1X pages are sent to the device or when the user chooses to make a voice call, intelligent algorithms establish the priority for processing these 1X requests and revert back to LTE data once the call is completed. The improvements in voice call quality can be maintained using the EVRC-NW codec. Hybrid 1X & LTE implementations also, however, have associated costs mainly relating to performance impacts on transitioning from LTE to cdma2000 and vice versa, compared to eCSFB since the 3G and 4G networks are operating independently and are not aware of the device transitions between the two. This, however, can be minimized by setting the right transition timers on the device, and leveraging existing messaging capabilities to ensure any impacts are minimal.
Hybrid 1X & LTE is fast becoming the de-facto solution for supporting CS voice over multi-mode networks and is becoming critical for cdma2000 roaming. While operators supporting e1X-CSFB can offer an enhanced voice experience in their networks, they can rest assured that while roaming, cdma2000 voice services can still be leveraged using Hybrid 1X & LTE across any of their cdma2000 roaming partners.
MDG 209 – Voice Options for Multimode Devices
The Mobility Development Group has been developing and maintaining a technical requirements document on Voice Options for Multimode Devices. This document captures the requirements a device manufacturer needs to consider when implementing SVLTE, e1X-CSFB and/or more recently Hybrid 1X & LTE. Operators and Manufacturers alike have been contributing to these requirements given no other industry documents capturing Hybrid 1X & LTE requirements exist. The MDG is also working in close collaboration with partner organizations like the Global Certification Forum (GCF) to develop test specifications and certification solutions for Hybrid 1X & LTE.
As technology evolves, it is becoming more apparent that Hybrid 1X & LTE solutions will need to exist even when VoLTE solutions become available, with some operators leveraging both VoLTE and CS 1X Voice to offer the best possible service for their users. Hybrid VoLTE, as it is fast becoming known, is the next logical evolution path and will be a key item on the Mobility Development Group’s technology roadmap.
Members are encouraged to participate, collaborate and contribute to the development of these technologies and ensure broad-range support in industry to enable interoperability of devices across networks, and reduce fragmentation. To participate in this initiative or to get a copy of the latest revision of Doc 209, please contact the MDG office at