Inching Ever Closer to the Any 3G/LTE Network Mobile Device

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the missing link image

iPad LTE pic I have written about my ire with Apple regarding their design decisionsThe basic complaint I have with the OEMs (Apple, Samsung, etc…) is that their LTE product design forces the end user to purchase a network specific mobile device. For example, I purchase a Band 13 device (VZW), I cannot then change my mind and go to ATT (Band 17) etc… Of course network operators don’t prefer this capability but let’s ignore that for the moment. Technologically, the ability to do this was limited by (A) the requirements of the devices and (B) the capability of the components in the devices.

Requirements as drivers to network locked devices.

Today’s mobile networks topologically, in the US from a data perspective,  are LTE overlays on existing 2G and 3G network coverage. This is a deployment scenario caused by the reality of the economy, risk aversion of operators etc and whatever. The requirement/expectation is end user  device is usable throughout the entire network coverage area of the network’s operator. Thus, if the LTE coverage ends, the device must gracefully hand down/over to 3G and resume data communications. This means a 3G radio and 4G radio is required to interact with the 2 networks (3G/4G.) 

Currently voice is carried over 3G and not VoLTE yet so this sets up more of the same 3G/4G multi-radio requirements.

Summary: Pure LTE device like a smartphone that uses something like VoLTE  for voice requires one radio and path at a time, today’s voice enabled devices require 2 radio paths. Data only devices can utilize a single radio path but are still hamstrung by the spectrum used for EVDO/HSPA as a fallback to LTE coverage holes ultimately requiring dual radio performance for smooth transitions. Oh yeah, CDMA EVDO handovers are better with eHRPD blah blah but I’m assuming a perfectly state of the art, fully capable device and network.

Capability of components

ipad3 teardown picI have written about the iPad radio design, and the key take aways were the RF chain required Apple to include band specific components to facilitate the multiple radio and/or paths required. There have been some improvements since I’ve moaned and I will go through some of those.


Firstly, let’s look at the antenna. If your load (includes antenna) is RF mismatched in the circuit with the amplifiers, duplexers, filters etc…the efficiency of the radio transmission/reception could suffer a great deal. This means more energy required to transmit/receive, possible harmful interference control measures required and end users end up paying more for poor performance in the end. I mention this because the previous crop of device antennae were not well suited for wide band use, like 700MHz through AWS 2100MHz in the same elements. 

Skycross,Skycross Logo a Fremont, CA company has recently announced some technology that can be helpful here. Here is information from their site:

SkyCross’ three core technologies contribute to addressing the growing number of frequency bands required for LTE and carrier aggregation.

  • iMAT allows a single antenna to act like multiple antennas through the use of multiple feedpoints. Each feedpoint accesses the single antenna as if it were two or more independent antennas, highly isolated from each other. This enables very efficient and compact antenna designs. Developers can combine the iMAT design with other antenna requirements to form a multi-band, multi-protocol antenna module.
  • VersiTune provides an advanced tunable antenna solution for multi-band 4G LTE devices in a single antenna structure. SkyCross can therefore actively tune an antenna from frequency band to frequency band accurately so that the antenna meets the many needs of a single operator or the frequency band requirements of multiple operators simultaneously.
  • MatchTune enables a single antenna structure to uniquely fine tune within a given LTE frequency band, which both enhances performance for a given frequency or for multiple simultaneous frequencies when employing carrier aggregation.

These technologies also enable ODMs and OEMs to improve the performance of their mobile devices, while concurrently reducing costs and shrinking the form factor of their products.

Here’s a good paper about their Isolated Mode Antennas (iMat).

So, yesterday’s devices required either poor efficiency or multiple antennas to support multiple air technologies and bands and now there is Skycross technologies that address these issues. OEMs can design true MIMO devices with good efficiency, in a reasonably small package. I think Apple at some point mentioned this problem with respect to their support for SVLTE in the Verizon version of their devices. Check this off the list of problems.

The next item on the list is the transceiver. I have mentioned Qualcomm’s WTR1605 previously, and this part essentially offers an expansion of bands and radio technologies over previous generations such that a typical 3G/4G band scenario that requires support for Bands 1,4, 12,13, 17 and 25 for LTE and PCS/AWS/800MHz cellular for CDMA. Furthermore, simultaneous support for 11 RX ports and 9 TX ports allow simultaneous multiple radio paths with dedicated PA/LNAs.

AnandTech went into some detail on the WTR1605L for your purchasing or RF hardware engineering pleasure in their blog: The State of Qualcomm’s Modems – WTR1605 and MDM9x25 (Actually, I liked the detail since Qualcomm didn’t publish any.)

WTR1605L RFIC by QualcommQualcomm says:

The WTR1605 will be Qualcomm’s first Radio Transceiver in Wafer Level Package and will be a highly integrated radio transceiver with multi-mode (LTE FDD, LTE TDD, CDMA, WCDMA, TD-SCDMA, GSM) and multi-band support. The WTR1605 will be optimized for low power consumption and small footprint and will integrate a high performance GPS core with GLONASS support. Samples of the MDM9615, MDM8215, WTR1605 and PM8018 are anticipated to be available in late 2011.

Lastly, the 3G/4G MODEM (baseband) is solved with Qualcomm’s 9200/9215 and 9600/9615/9625 parts support GSM/EDGE/WCDMA/CDMA/EVDO/and LTE the technologies of interest here. So we are nearly there with 3 parts. There is something missing though.

The Missing Link

the missing link image

So what’s stopping us from a single multimode multi-band design to serve all networks and end users? The Power Amplifier (PA) and Low Noise Amplifier (LNA) situation. I’m not going to go too deep here because for multiple reasons but on the face of it there are many extra components that would be needed to support all of the Bands 1,4, 12,13, 17 and 25 with MIMO for LTE and PCS/AWS/800MHz cellular for CDMA. It’s not impossible and there are some design decisions that can be made if the OEM is willing to live with extra band specific LNA/PA’s on board. The downside is without any magic, they will take up extra space, create more heat and consume power with or without use. I think there is a better way (Custom silicon) that Apple and Samsung could probably bring to bear more quickly than any other OEMs.  

There You Go

So as you can see, there are 2 paths and on 1, we are tantalizingly close to having universal mobile devices. Oh yeah, as I have mentioned before you will probably need a removable UICC too and Apple has this design presently.  The Path 1 fix with a universal mobile device, when to expect the LNA/PA/duplexor/filter solution? Like I said, an innovator like Apple or Samsung could knock it out rapidly (assuming quickly with core purchased IP from SkyWorks, TriQuint etc…) like mid this year. Else, the groundhog will see it’s shadow and we’ll be having to check at the end of next winter. On the Path 2 fix, implement VoLTE, make LTE ubiquitous and stop using 3G networks, that will take a wee bit longer.