GSM LTE phones vs CDMA LTE phone radios


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Feb 13, 2010
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I found an interesting article about radios and LTE connections. The Radio Performance Disparity of the Galaxy Nexus on GSM and CDMA - Mobile Central - Binary Outcast

I have the oppurtunity to either go with ATT or Verizon. The article makes it seems that GSM is a better bet for LTE phones especially in areas with poor reception. I am hoping people can provide insight/comments on LTE phones for GSM and CDMA carriers and the article.

The Radio Performance Disparity of the Galaxy Nexus on GSM and CDMA

The Samsung Galaxy Nexus. It's Google's flagship phone that is designed to complement the Android 4.0 ?Ice Cream Sandwich? operating system software. With high end specifications (for 2011) and highly optimized software, the Galaxy Nexus is supposed to show off what Android can really do without any interference from carriers and OEMs. However, that wound up not truly being the case in the United States with the CDMA/LTE variant for Verizon Wireless and Sprint.

By and large, the CDMA/LTE variant sold by Verizon Wireless and Sprint is the same as the original HSPA+ model that is now sold by Google on the Play Store (at least in terms of hardware). It has the same CPU, RAM, NFC chip, screen, cameras, etc. The only hardware difference is the cellular radio structure.

The original UMTS HSPA+ model uses an Intel XG626 baseband modem that is connected to an antenna structure that supports quad-band GSM and penta-band WCDMA for global usage. For Americans, it means that it works on the HSPA+ networks for both AT&T and T-Mobile USA.

The CDMA/LTE variant uses a VIA Telecom CBP7.1 CDMA2000 baseband modem, connected to an antenna structure that supports dual-band CDMA2000. The Sprint model adds another CDMA2000 band that is exclusive to Sprint. Both CDMA/LTE variants use a Samsung CMC221 LTE baseband modem, but the Verizon Wireless variant is set up for LTE band class 13 (Upper 700MHz C block), while the Sprint variant is set up for LTE band class 25 (U.S. Extended PCS, also known as PCS+G). The Verizon Galaxy Nexus has a user-accessible SIM card slot while the Sprint one does not.

While the Intel (formerly Infineon) baseband used to be troublesome on AT&T's network (as many iPhone users that didn't own an iPhone 4S can attest to), the latest generation of basebands work fine on both AT&T and T-Mobile. With 3GPP Release 7 support, it has a maximum downlink throughput of 21Mbps while it has a maximum uplink throughput of 5.76Mbps. In general, the Galaxy Nexus works very well on AT&T and T-Mobile.

However, it isn't the same for the CDMA variants of the Galaxy Nexus. The VIA Telecom CDMA chip is notorious for weak performance. Other notable devices that use the chip are the Samsung DROID Charge and the Samsung Stratosphere. Searching on the web about these devices turns up a lot of complaints about CDMA service quality with these devices.

Jason Perlow of ZDNet experienced more than his fair share of issues while trying to live off of the 4G LTE connection his Galaxy Nexus provided. But he was trying to live off of 4G LTE, not CDMA2000. So why was he affected? Well, the truth is, CDMA/LTE devices require both radios to be active and connected. Not to mention, network authentication and feature provisioning actually goes through the CDMA system, not the LTE one.

The bridge between CDMA2000 and LTE is rather brittle and is prone to failure, because LTE wasn't designed to be bridged with CDMA2000 like that. It was intended to be installed alongside GSM and WCDMA networks, and it handles it a lot better with those networks. So when something goes wrong in the rather terribly buggy CDMA system, the whole phone can and usually does fail. If Verizon Wireless had upgraded the CDMA2000 system to UMTS HSPA+ like most other CDMA2000 carriers across the globe, it would have avoided dealing with this problem.

Also, the CDMA/LTE Galaxy Nexus lies to you (at least, it does now). Originally, the ?bars? that indicate signal strength would actually indicate the signal strength of LTE if it was connected to an LTE network. When everyone started complaining about how weak the signal was compared to the Motorola DROID RAZR and Motorola DROID Bionic, Anandtech investigated. It turned out that the signal strength was actually accurate, and that LTE signals are incredibly weak. Previous devices used the CDMA signal strength to determine how many ?bars? of signal you have. The Galaxy Nexus did not. It used the LTE signal strength when it was connected to LTE, and the CDMA signal strength when it wasn't. Verizon Wireless issued an update shortly afterward that changed the behavior to match older LTE devices. Newer LTE devices do the same as well.

Combining the fact that the Galaxy Nexus has to work incredibly hard to maintain an LTE signal with the fact that the CDMA2000 radio is horrible and has a difficult time holding onto the connection will lead anyone to the conclusion that it is a recipe for disaster. Is it any wonder why Jason Perlow and many others have so many problems with the CDMA/LTE version of the Galaxy Nexus? Not really.

Of course, this is excluding all the issues with timely updates that Verizon Wireless has caused for Galaxy Nexus owners. Including this issue just makes the problem worse. There are ways to work around some of the issues, though some workarounds will result in permanent degradation of performance. However, it doesn't mean anything if it takes forever for anyone to get any updates that implement them.

In the end, I really can't solidly recommend the CDMA/LTE version of the Galaxy Nexus to anyone. Nor can I recommend any CDMA2000 device that uses a VIA Telecom CDMA baseband modem. The pitfalls just make it a bad experience for everyone.[


Jun 28, 2010
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Nice write up, I had the cdma nexus and sadly had to return it since I kept dropping calls for me the revolution was terrible. I almost got the s3 but bailed at the last second after reading similar reports about reception problems. My contract is up in 15 days and I am happily going back to gsm.


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Jan 19, 2011
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Before you go around posting this anymore, suggest you read up on the Qualcom S4 setup which doesn't have the problems in which you are posting everywhere.


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Jul 15, 2010
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Far from being an expert; but from what I have read, it was not a problem with CDMA or LTE, per se, it was due to the chips used. The LTE baseband chip did not play well with the OMAP processor and vice versa.
Also believe this problem was corrected in an new flashed version. And from reading reviews of many other phones running LTE/CDMA, the problem has been resolved in all other phones.

Again, I AM NOT AN EXPERT in phone electronics, but I do read a lot, I used to stay at Holiday Inn Express motels, so I'm not a total idiot either.:D