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Date: 20-01-12

MIPI announces DigRF v4 v1.10 and RFFE v1.10 specs for mobile phone designers

MIPI Alliance has announced two new specifications targeting the digital modem and the front-end radio portions of a mobile device. The DigRF v4 v1.10 specification defines the interface between one or more baseband ICs and radio frequency (RF) ICs, and delivers increased bandwidth for data-intensive HSPA+/LTE architectures. The RFFE v1.10 specification defines a standardized control architecture for RF front-end devices, and offers a low-complexity solution for multi-mode, multi-band and multiple antenna configurations. Both specifications expand on previous versions by addressing today's complex multi-radio wireless systems.

Here is the Q&A posted in its release by MIPI Alliance:

Q. Why did MIPI Alliance develop these specifications?
A. As the global leader in mobile interface technology, MIPI Alliance includes members who are intimately involved in radio technology. Both of these specifications expand on previous versions, addressing the increasingly complex market demands of multi-radio, multi-band wireless architectures.

Q. What applications are targeted with these specifications?
A. Both the DigRF and RFFE specifications address the radio portion of wireless devices, spanning next generation technologies including HSPA+, LTE, Mobile WiMAX, as well as established 3GPP and non-3GPP air interfaces.

Q. Are these specifications backwards-compatible with their previous versions?
A. RFFE: The RFFE v1.10 specification is backwards-compatible with the previous (v1.00.00) version.
DigRF: DigRF v4 v1.10 is backwards-compatible with the previous (v1.00.00) version. DigRF v4 v1.10 now references the MIPI Alliance Specification for M-PHY v1.00.00 which is also backwards-compatible with M-PHY v0.80.00.

Q. If a company has begun implementing previous versions of the specifications, should they transition to the more current version? Or can they continue their development work?
A. RFFE: Development can continue with v1.00.00; however it is recommended that transition be made to v1.10 as the latest version clarifies certain topics or areas in the specification. Provided that the requirements as stated in v1.00.00 of the RFFE Specification are interpreted correctly, it is not expected that the release of v1.10 will require redesign of existing devices.
DigRF: Development of DigRF v4 v1.00.00 can be continued with a smooth transition to DigRF v4 v1.10 since only incremental enhancements were added.

Q. When were the first versions of these specifications released?
A. RFFE v1.00.00 was released to members in 3Q 2010. DigRF v4 1.00.00 was released in 2Q 2010. Visit www.mipi.org for details on both.

Q. Who can use these MIPI specifications?
A. MIPI specifications are available to MIPI Alliance members.

Q. Are there other organizations that develop interface specifications for the radio portion of wireless devices?
A. We are not aware of any other standards organization that has developed a control interface specifically for the RF front-end or an interface between BBICs and RFICs. Many proprietary interfaces exist, which was one of the motivations for creating the RFFE and DigRF Specifications.

Q. Will MIPI Alliance continue to develop new versions of DigRF v4 and RFFE?
A. Yes, MIPI Alliance believes that radio systems and air interface technology will continue to grow in complexity. In fact, the DigRF Working Group and the RFFE Working Group are both already investigating their next-generation specifications.

Q. If both of these specifications target the radio, why are there two separate working groups?
A. While both address the radio portion of a wireless device, each group focuses on a unique portion of the radio. DigRF was developed as a high-
speed interface for carrying digital RF IQ data and RF control information between the Baseband IC and the RFIC, while RFFE addresses the control interface between the RFIC/Baseband IC and the RF Front-End devices.
Technical Q&As - DigRF v4 v1.10

Q. What does DigRF v4 v1.10 specify?
A. This document specifies the interface between one or more baseband ICs (BBICs) and the radio frequency ICs (RFICs) in a mobile terminal.

Q. What is different between v1.00.00 and v1.10 of the specification?
A. DigRF v4 v1.10 is primarily a maintenance update to the DigRF v4 specfication. It was created as a means to update information about, and references to, the v1.00.00 release of the M-PHY specification, which is used in DigRF v4 as the physical layer. At the same time, extensive updates to the DigRF v4 specification were undertaken to clarify details of the DigRF v4 interface. No significant technical changes to DigRF v4 exist between v1.00.00 and v1.10.

Q. What are the key attributes of the specification?
A. Some of the important points addressed by DigRF v4 are:
* Increased bandwidth capability to support data rates for HSPA+, LTE, WiMAX, etc.
* Minimized interface pin count
* Reduce overall interface power consumption
* Manage EMI issues to avoid RF spurious problems
* Add flexibility and scalability to allow usage of multiple receivers and transmitters simultaneously

Q. What are the key benefits for this specification?
A. DigRF v4 provides a standardized interface. This high-speed serial interface technology provides optimized power efficiency via multiple speed modes and fast cycling between active and power-saving operations. It does
so while also providing for low EMI operational impact, as well as protection from interference induced into the interface

Q. Does this specification include a physical layer?
A. DigRF v4 leverages MIPI's M-PHYSM physical layer, which is also used in other parts of a wireless device.

Q. What is not included in the specification?
A. DigRF v4 is not a system design specification, and does not standardize a detailed programming model for RFICs. However, some system aspects - such as EMI - are included to enable optimal performance and operations. DigRF v4 focuses solely on the interface between the baseband and RF ICs.

Q. Which companies developed this v1.10 specification?
A. Arasan Chip Systems Inc., Cadence Design Systems, Inc, Fujitsu Limited, Intel Corporation, Motorola Mobility, Inc., Nokia Corporation, Panasonic Corporation, Research In Motion, ST-Ericsson, Synopsys, Inc and Texas Instruments, Inc. were the primary contributors. Other companies have provided support and suggestions.

Q. Is there a roadmap for this specification?
A. Yes, upcoming versions of DigRF v4 will address the needs of higher bandwidth requirements for LTE-A.

Q. What is unique to DigRF v4 compared to other high speed interfaces?
A. This specification offers the ability to manage and minimize EMI issues in a radio frequency environment. DigRF v4 provides a protocol and a set of operating modes tailored to the needs of a BB to RFIC interface and allows control messages with very low latency. This offers flexibility and scalability for air interface standards.

Q. Is DigRF v4 already used in products that are on the market?
A. Yes, multiple vendors offer solutions incorporating DigRF v4.
Technical Q&As - RFFE v1.10

Q. What does RFFE v1.10 specify?
A. The specification defines a control interface for RF Front-End devices including, but not limited to, power amplifiers, low-noise amplifiers, filters, switches, power management modules, antenna tuners and sensors. The interface is a compact two signal serial interface (clock and data) designed for low gate count, low current consumption and low EMI. In addition to the specification, the RFFE Working Group has developed an RFFE Application Note and a PICS document. The Application Note discusses and explains informative or more implementation-related issues. The PICS document is the Protocol Implementation Conformance Statement which may be used by a device implementer to identify the capabilities and options of the protocol that have been implemented, or by a systems designer to verify device capabilities.

Q. What is different between v1.00.00 and v1.10 of the specification?
A. As per MIPI specification numbering policy, a change to the minor number revision field indicates that only relatively minor changes have been made to the document. Accordingly, in the latest version of the MIPI RFFE Specification the intent is that technical differences are kept to a minimum between v1.00.00 and v1.10. The RFFE WG went to some effort to ensure that this is the case. The primary intent of the RFFE WG in releasing a v1.10 was to clarify certain topics or areas in the specification, and not to incorporate any major technical changes at this time. While a better understanding of certain requirements or parameters could result in alternate implementation decisions by a user, it was not the intention of this release to require any changes to existing device designs.

Q. What are the key attributes of the specification?
A. Some of the primary points of focus for RFFE are:
* Minimize the wiring effort on the front end of a mobile terminal
* Minimize pin count
* Ease and optimize flow control
* Ensure minimal EMI contributions from the RFFE bus
* Minimize complexity for the Slave
* Add flexibility and scalability, allowing use of multiple receivers and transmitters simultaneously

Q. What are the key benefits for this specification?
A. The RFFE control interface supports multiple RF Front-End devices with a minimum number of wires and pins, while using a single RFFE bus. RFFE is a common interface which allows interoperability for many different devices in a RF front-end.

Q. What is not included in the specification?
A. Analog signal paths required between the front-end devices and other elements that control and utilize devices are outside the scope of the RFFE specification.

Q. Which companies developed this v1.10 specification?
A. Analog Devices Inc., Fujitsu Limited, National Semiconductor, Nokia Corporation, NXP Semiconductors, Panasonic Corporation, Peregrine Semiconductor, Qualcomm Incorporated, RF Micro Devices, Skyworks Solutions, Inc., ST-Ericsson and WiSpry Inc. were the primary contributors. Other companies have provided support and suggestions.

Q. Is there a roadmap for this specification?
A. The WG is actively developing requirements and technical details for a next generation update to the RFFE specification. The time frame for this is not yet determined.


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