MIPI® Alliance Advances Radio Frequency Interface Technology in Mobile Devices 

New DigRF^SM and RFFE Specifications Address Growing System Complexity 

The DigRF^SM Working Group was established as a MIPI Alliance Working Group in April 2007. The group’s scope is to develop specifications for wireless mobile Baseband IC (BBIC) to Radio Frequency IC (RFIC) interfaces in various mobile terminals. The ability to design one common high-speed interface that can be re-used for multiple applications is intended to help reduce design resource requirements and speed up the time-to-market for these terminals.

A BBIC to RFIC interface has unique requirements that are not typically met by other interface standards and the requirements of emerging air interface standards are not met by existing BBIC to RFIC interface standards. DigRF^SM addresses a need for high-speed serial interface technology with high bandwidth capabilities developed specifically for a wide range of emerging mobile applications.

Committed to designing a sustainable specification for the long term, the WG is focused on efficiency, flexibility, and extensibility, while accommodating many variations in an overlying system design and providing interoperability at the interface level between compliant ICs.

The DigRF^SM WG has also collaborated extensively with MIPI’s PHY WG to allow the use of a common M-PHY^SM physical layer. This is a significant benefit given the increased performance requirements and complexity of next generation mobile terminals.

The DigRF^SM working group released the MIPI Alliance Specification for DigRF^SM v4 v1.10 in December 2011 and an updated MIPI Alliance Specification for DigRF^SM 3G Dual Mode 2.5G/3G Baseband/RFIC Interface v3.09.06. DigRF^SM v4 v1.10 is backwards-compatible with the previous (v1.00.00) version. DigRF^SM v4 v1.10 now references the MIPI Alliance Specification for M-PHY^SM v1.00.00 which is also backwards-compatible with M-PHY^SM v0.80.00.

The DigRF^SM v4 interface was designed in response to the rising deployment of high-bandwidth air interface standards requiring higher channel bandwidth, IQ sampling rates, IQ sample bit width, RX Diversity and MIMO. Described as the ‘link for the long term’, DigRF^SM v4 was developed for mobile terminals that support next generation mobile broadband technologies such as Long Term Evolution (LTE) while supporting existing 3GPP standards such as 2.5G and 3.5G (EGPRS, UMTS, HSPA, etc.). Due to its large data rate and scalability, it is also suitable to cover other non-3GPP air interfaces over a common interface.

DigRF^SM v4 is intended to increase bandwidth capabilities, minimize pin count, provide an efficient protocol for data transfer, and allow the use of multiple receivers and transmitters simultaneously. DigRF^SM v4 provides a robust, high performance scalable digital link with low latency, high timing accuracy, power-saving operations and low EMI. In addition, it also natively handles MIMO configurations and receive diversity.

DigRF^SM 3G is targeted for 2.5G GPRS / EGPRS as well as 3.5G UMTS chipsets including HSPA and also supports receive diversity in all cases.

Although first silicon implementations of DigRF^SM v4 v1.00.00 and v1.10 demonstrate the maturity of a well-seasoned specification, the DigRF^SM WG is currently working on DigRF^SM v4 Specification v1.2 to include extensions for M-PHY HS Gear 3 and is expected to publish an approved version of this specification update in Q2-2013. 

History and Roadmap

Working Group Chair

Dr. Dietmar Wenzel - Intel Corporation