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LTE / TD-LTE Compatibility


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Now that it looks like Clear is moving full steam ahead with its TD-LTE network, how is the interoperability between traditional LTE (being deployed by AT&T, Sprint & Verizon) and TD-LTE?

 

Furthermore, given the Chinese governments delay in issuing TD-LTE licenses for a few years, WHAT IF (big "what if"), China decides to go a different route than TD-LTE? What are the compatibility ramifications for Clearwire?

 

It appears TD-LTE is a superior technology to traditional LTE given that its LTE advanced-ready and it is much better at penetrating walls in higher spectrum frequencies such as Clear's 2.5 GHz. However, if its not compatible with the rest of the world, isolation could cause all sorts of issues including lack of roaming agreements and OEM / device support. Just ask Sprint, they are spending billions to dump WiMAX and go LTE since they would have been in a similar situation.

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As far as interoperability goes Sprint claims the transition will be seamless between the two technologies.

 

Wtih regards to traditional FDD-LTE vs TD-LTE, they are both still LTE rel. 9 (or 10 when advanced is rolled out) and are different only in the method they make use of spectrum. FDD-LTE is meant for traditional paired spectrum like the Sprint PCS band which has seperated uplink and downlink channels. One example of paired spectrum is the PCS G-Block which uses 1910-1915 mhz uplink and 1990-1995mhz downlink. These two links are seperated by 75mhz of bandwidth.

 

TD-LTE is designed to be used with unpaired spectrum like the Clear BRS band which may be (making this up) 2500-2520mhz which has no separation (or guard band) between the downlink and the uplink. TD or Time division compensates for this by making use of that same band for both uplink and downlink and switches between the two links as a function of time like alternating current.

 

So one isn't necessarily better than the other they are just designed for different spectrum allocations (paired vs. unpaired).

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The next big issue for wireless is: developing a chip set that is interoperable with the different bands of spectrum and roaming agreements. A chip hasn't been developed yet to allow cross usage among all the carriers spectrum, only a say about 3 or 4 different frrequencies. The FCC is going to have to step in to get roaming agreements. AT&T and Verizon are fighting it, but Sprint, T-Mobile and the regionals need it.

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Sort of like the Gobi 4000, but made small enough for mobile phones. But like you said, the big two (if not all) of the carriers might not want such a beast. Only then can the world be at our doorstep without having to worry about spectrums, roaming agreements and carriers stubborness.

 

TS

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I'm growing tired of reminding people of this: the chip's support of the bands is not an issue. The present Qualcomm MDM9600 modem (in the HTC Thunderbolt & Rezound along with numerous AT&T devices and the upcoming iPad3) used for LTE does Verizon 700, AT&T 700, and will work in PCS, AWS, and all defined LTE bands. The problem is the RF electronics (preamps, diplexers, filters) and antennas. There is not physical room to support more than 1 or 2 LTE bands on a phone that will fit into your pocket. The only phones approved with more than a single LTE band class are the upcoming AT&T phones approved for 700 and AWS, and the reason they're approved is because they only have to support 2 bands of GSM/GPRS/HSPA. So 4 bands total.

Edited by 4ringsnbr
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I'm growing tired of reminding people of this: the chip's support of the bands is not an issue. The present Qualcomm MDM9600 modem (in the HTC Thunderbolt & Rezound along with numerous AT&T devices and the upcoming iPad3) used for LTE does Verizon 700, AT&T 700, and will work in PCS, AWS, and all defined LTE bands. The problem is the RF electronics (preamps, diplexers, filters) and antennas. There is not physical room to support more than 1 or 2 LTE bands on a phone that will fit into your pocket. The only phones approved with more than a single LTE band class are the upcoming AT&T phones approved for 700 and AWS, and the reason they're approved is because they only have to support 2 bands of GSM/GPRS/HSPA. So 4 bands total.

 

4rings...yes you have definitely posted that before. I appreciate your info, even if you are an overly direct communicator. :P

 

Robert

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I'm growing tired of reminding people of this: the chip's support of the bands is not an issue. The present Qualcomm MDM9600 modem (in the HTC Thunderbolt & Rezound along with numerous AT&T devices and the upcoming iPad3) used for LTE does Verizon 700, AT&T 700, and will work in PCS, AWS, and all defined LTE bands. The problem is the RF electronics (preamps, diplexers, filters) and antennas. There is not physical room to support more than 1 or 2 LTE bands on a phone that will fit into your pocket. The only phones approved with more than a single LTE band class are the upcoming AT&T phones approved for 700 and AWS, and the reason they're approved is because they only have to support 2 bands of GSM/GPRS/HSPA. So 4 bands total.

 

Yup Yup nothing to do with the chips now long as were using qualcomms beauties....all about the other physical stuff needed to communicate...maybe antennae tech will take a leap soon and allow this to be possible?...

 

Sent from my PG86100 using Tapatalk

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So, to listen FM radio you have to use directly connected headphones as FM antenna...

Why not use micro USB cable as "additional" antenna?

At least, I will have a perfect signal in my car or using a doc station etc...

Patent for it is buried somewhere already?

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  • 4 weeks later...

So, to listen FM radio you have to use directly connected headphones as FM antenna...

Why not use micro USB cable as "additional" antenna?

At least, I will have a perfect signal in my car or using a doc station etc...

Patent for it is buried somewhere already?

 

I'm assuming because USB has sheilding and (not to sure on this) because antennas are supposed to be certain lengths for certain wave lengths/spectrum USB cables won't support LTE too well as it doesn't handle noise well either but FM on the other hand can be recieved with a rusty coat hanger...

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I'm growing tired of reminding people of this: the chip's support of the bands is not an issue. The present Qualcomm MDM9600 modem (in the HTC Thunderbolt & Rezound along with numerous AT&T devices and the upcoming iPad3) used for LTE does Verizon 700, AT&T 700, and will work in PCS, AWS, and all defined LTE bands. The problem is the RF electronics (preamps, diplexers, filters) and antennas. There is not physical room to support more than 1 or 2 LTE bands on a phone that will fit into your pocket. The only phones approved with more than a single LTE band class are the upcoming AT&T phones approved for 700 and AWS, and the reason they're approved is because they only have to support 2 bands of GSM/GPRS/HSPA. So 4 bands total.

 

I posted about the Nokia Lumina 900 and it seems to prove that you can stuff a TON of bands inside a phone.

 

It seems like the number of bands isn't that big of an issue. Not sure how they do it, or how many antennas it has (looks like two... but not sure).

 

Any insight?

 

GSM 850/900/1800/1900, WCDMA 850/900/1900 and LTE 700/1700/2100.

Edited by irev210
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I posted about the Nokia Lumina 900 and it seems to prove that you can stuff a TON of bands inside a phone.

 

It seems like the number of bands isn't that big of an issue. Not sure how they do it, or how many antennas it has (looks like two... but not sure).

 

Any insight?

 

GSM 850/900/1800/1900, WCDMA 850/900/1900 and LTE 700/1700/2100.

 

irev, in this and your aforementioned previous post, you seem to confuse bands with modes.

 

Cellular 850 MHz, GSM 900 MHz, DCS 1800 MHz, and PCS 1900 MHz are four bands. Band wise, the GSM and W-CDMA distinctions are irrelevant; those airlinks represent only separate modes. So, just four bands are needed to cover the GSM and W-CDMA modes.

 

As for LTE, Lower 700 MHz and AWS 2100+1700 MHz are separate bands. Also, "2100" may indicate IMT 2100+1900 MHz as an additional supported band. While all three are indeed separate bands, they may not, for example, require as many additional antennas (or antenna capabilities) as meets the eye.

 

Lower 700 MHz, yes, requires its own compatible antennas. However, AWS and IMT share essentially the same downlink frequencies, hence can share the same downlink MIMO antennas. Furthermore, since LTE uplink MIMO is not apt to be a reality on handsets anytime soon, a single antenna per uplink band should suffice. AWS uplink corresponds very closely to DCS uplink, while IMT uplink corresponds very closely to PCS downlink. So, those antennas may be reused.

 

Now, that said, all bands do require appropriate power amp modules and filters, so it is still no free lunch. But my primary point is that you inflate the number of bands. For further clarification, see the previous thread:

 

http://s4gru.com/ind...okia-lumia-900/

 

AJ

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I posted about the Nokia Lumina 900 and it seems to prove that you can stuff a TON of bands inside a phone.

 

It seems like the number of bands isn't that big of an issue. Not sure how they do it, or how many antennas it has (looks like two... but not sure).

 

Any insight?

 

GSM 850/900/1800/1900, WCDMA 850/900/1900 and LTE 700/1700/2100.

 

GSM and WCDMA can be done with a single Tx and single Rx antenna and the U.S. / European 850/900 and 1800/1900 GSM/WCDMA bands have long been incorporated together in a single device. The IMT 2100 WCDMA support is a little extra compared with the standard fare, but the antenna can be shared with the PCS array. The problem is LTE since it will require 1 Tx and 2 Rx antennas (with precise spacing) to function for EACH band it supports. All of AT&T's recent devices seem to support 2 LTE bands and 2 GSM/GPRS/WCDMA bands. This device (actually two models, QMNRM-808 and QMNRM-823 is no different. It essentially supports 4 bands.

The problem when it comes to other carriers is EVDO (and 1x Advanced). EVDO requires Rx diversity too, so an extra antenna is needed per band on top of the CDMA / 1x antennas. This makes it significantly harder to engineer a multi-band CDMA and LTE device. I would imagine the first multiple band CDMA/LTE devices we'll see will be the next wave of smartphones from Verizon. They will likely support CDMA/EVDO in 850 Cellular & PCS 1900 as well as LTE in Upper C 700 (BC 13) and AWS. These will be four band devices too, but the EVDO in 850 and 1900 will require extra antennas as compared with AT&T's quad-band devices.

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GSM and WCDMA can be done with a single Tx and single Rx antenna and the U.S. / European 850/900 and 1800/1900 GSM/WCDMA bands have long been incorporated together in a single device. The IMT 2100 WCDMA support is a little extra compared with the standard fare, but the antenna can be shared with the PCS array. The problem is LTE since it will require 1 Tx and 2 Rx antennas (with precise spacing) to function for EACH band it supports. All of AT&T's recent devices seem to support 2 LTE bands and 2 GSM/GPRS/WCDMA bands. This device (actually two models, QMNRM-808 and QMNRM-823 is no different. It essentially supports 4 bands.

The problem when it comes to other carriers is EVDO (and 1x Advanced). EVDO requires Rx diversity too, so an extra antenna is needed per band on top of the CDMA / 1x antennas. This makes it significantly harder to engineer a multi-band CDMA and LTE device. I would imagine the first multiple band CDMA/LTE devices we'll see will be the next wave of smartphones from Verizon. They will likely support CDMA/EVDO in 850 Cellular & PCS 1900 as well as LTE in Upper C 700 (BC 13) and AWS. These will be four band devices too, but the EVDO in 850 and 1900 will require extra antennas as compared with AT&T's quad-band devices.

 

So is it possible that Apple will have 3 different versions of the iPhone for the US alone, all with different radio setups? That would sure put a hamper on interoperability.

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So is it possible that Apple will have 3 different versions of the iPhone for the US alone, all with different radio setups? That would sure put a hamper on interoperability.

 

Anything is possible. That is how Steve Jobs became a successful pioneer in technology.

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So is it possible that Apple will have 3 different versions of the iPhone for the US alone, all with different radio setups? That would sure put a hamper on interoperability.

 

Well there will have to be a separate AT&T and Verizon LTE model as you cannot combine the lower and upper 700 LTE spectrum in the same device with the FCC filtering requirements. The third model would probably be a pentaband phone like the GNex but have LTE in AWS and maybe PCS for other carriers-- but I don't know if the demand will be sufficient for this. I would basically expect at least 3 versions just like the new iPad. Lower and Upper 700 LTE will NEVER be interoperable-- the way they're setup and the filtering requirements to protect public safety upper and lower and channel 51 will make that a non-starter. The FCC's current investigation of LTE interoperability focuses on the Lower 700 bands 12 & 17-- the AT&T and regionals should be able to be interoperable with no issues. Band 13 (upper band used by Verizon) is totally incompatible with the rest of 700 -- it is duplex inverted, has different filtering requirements and has net neutrality requirements too.

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Well there will have to be a separate AT&T and Verizon LTE model as you cannot combine the lower and upper 700 LTE spectrum in the same device with the FCC filtering requirements. The third model would probably be a pentaband phone like the GNex but have LTE in AWS and maybe PCS for other carriers-- but I don't know if the demand will be sufficient for this. I would basically expect at least 3 versions just like the new iPad. Lower and Upper 700 LTE will NEVER be interoperable-- the way they're setup and the filtering requirements to protect public safety upper and lower and channel 51 will make that a non-starter. The FCC's current investigation of LTE interoperability focuses on the Lower 700 bands 12 & 17-- the AT&T and regionals should be able to be interoperable with no issues. Band 13 (upper band used by Verizon) is totally incompatible with the rest of 700 -- it is duplex inverted, has different filtering requirements and has net neutrality requirements too.

 

So does that mean that device costs for some phones could go up?

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So does that mean that device costs for some phones could go up?

 

They may go up, but the carriers will eat it with subsidies. They will only charge what the market will bear-- in other words, whatever AT&T charges for a device of a certain class, Sprint, Verizon, and even T-Mobile will be largely tied to that cost range. A good case in point is the new Verizon LG Lucid. This is essentially the same phone Sprint will call the Viper. Verizon charges $79 for the Lucid on contract. Sprint can't afford to move much above $99 for the same basic device. They only have additional leverage because this is their only LTE device (right now). Verizon has dozens of LTE devices-- but the concept is the same. It wouldn't surprise me to see all iPhones go into the $249 - $349 on contract price range with the LTE generation since the carriers' profits are really hurt badly by the steep Apple subsidies, which are significantly higher than other phone manufacturers.

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They may go up, but the carriers will eat it with subsidies. They will only charge what the market will bear-- in other words, whatever AT&T charges for a device of a certain class, Sprint, Verizon, and even T-Mobile will be largely tied to that cost range. A good case in point is the new Verizon LG Lucid. This is essentially the same phone Sprint will call the Viper. Verizon charges $79 for the Lucid on contract. Sprint can't afford to move much above $99 for the same basic device. They only have additional leverage because this is their only LTE device (right now). Verizon has dozens of LTE devices-- but the concept is the same. It wouldn't surprise me to see all iPhones go into the $249 - $349 on contract price range with the LTE generation since the carriers' profits are really hurt badly by the steep Apple subsidies, which are significantly higher than other phone manufacturers.

 

Understandable. I saw the Lucid and I like the phone. Looks pretty nice for entry level LTE devices. When was it released?

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Understandable. I saw the Lucid and I like the phone. Looks pretty nice for entry level LTE devices. When was it released?

I think it was released about 2 weeks ago-- I didn't really pay attention-- I'm married to my MAXX for now...

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EVDO requires Rx diversity too, so an extra antenna is needed per band on top of the CDMA / 1x antennas.

 

I can find no real world basis for the frequent claim that EV-DO "requires" Rx diversity. If anything, I find more evidence for the contrary. Take the Samsung Illusion, for example, a plain Jane EV-DO 850/1900 handset on VZW. See the antenna block diagram (from the FCC OET filing):

 

6gltll.png

 

Now, unless the Samsung Illusion incorporates Rx diversity within that ~20mm x ~20mm single WWAN Tx/Rx antenna array, then EV-DO seemingly cannot "require" Rx diversity.

 

AJ

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I can find no real world basis for the frequent claim that EV-DO "requires" Rx diversity. If anything, I find more evidence for the contrary. Take the Samsung Illusion, for example, a plain Jane EV-DO 850/1900 handset on VZW. See the antenna block diagram (from the FCC OET filing):

 

 

 

Now, unless the Samsung Illusion incorporates Rx diversity within that ~20mm x ~20mm single WWAN Tx/Rx antenna array, then EV-DO seemingly cannot "require" Rx diversity.

 

AJ

 

The use of required was a poor choice of words. Technically, EVDO can be done without receive diversity; however, receive diversity improves real world downlink throughput by 35 - 45% and SINR by 4-4.5 dB. This is why it is used in almost all EVDO devices (phones and aircards) for the past several years. Keep in mind that the Rx diversity is NOT MIMO, so the antenna spacing isn't as critical and these antennas may be right next to each other. In the LG Viper, I think they shared the Rx/Tx with CDMA and used one of the LTE Rx antennas for the 2nd Rx EVDO-- but I haven't looked at it in a while so I don't remember exactly. I do know it used separate antennas for Rx diversity on EVDO, but didn't necessarily share the same spacing as the LTE MIMO Rx antenna spacing. The Rx diversity just helps with multipath issues and primarily improves signals in fringe areas, though all areas do benefit from it. Technically 1x Advanced doesn't REQUIRE Rx diversity either, if 3x RTT's capacity is all that is desired; however, to get the full benefit (4x capacity of RTT), you have to have Rx diversity on 1xA. Again, I would expect manufacturers to treat it as a must-do like they do currently with EVDO Rx diversity.

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The problem when it comes to other carriers is EVDO (and 1x Advanced). EVDO requires Rx diversity too, so an extra antenna is needed per band on top of the CDMA / 1x antennas. This makes it significantly harder to engineer a multi-band CDMA and LTE device. I would imagine the first multiple band CDMA/LTE devices we'll see will be the next wave of smartphones from Verizon. They will likely support CDMA/EVDO in 850 Cellular & PCS 1900 as well as LTE in Upper C 700 (BC 13) and AWS. These will be four band devices too, but the EVDO in 850 and 1900 will require extra antennas as compared with AT&T's quad-band devices.

 

What do you make of the Samsung Aviator for USCC which appears to support dual band CDMA/EVDO (cellular, PCS) as well as quad band LTE (BC 2, 4, 5, 12)?

 

http://www.phonescoop.com/phones/phone.php?p=3638

http://www.samsung.com/us/mobile/cell-phones/SCH-R930DSAUSC-specs

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What do you make of the Samsung Aviator for USCC which appears to support dual band CDMA/EVDO (cellular, PCS) as well as quad band LTE (BC 2, 4, 5, 12)?

 

http://www.phonescoo...hone.php?p=3638

http://www.samsung.c...930DSAUSC-specs

 

Hadn't noticed that one before-- looking at the FCC approvals for RF exposure, the thing has 6 antenna arrays! The whole thing looks like an antenna. CDMA/EVDO arrays are all tucked together in the bottom left corner. The top left corner has all LTE bands Rx and Tx. The 2nd Rx for LTE bands 5 & 12 is bottom right corner and the 2nd Rx for LTE bands 4 & 2 are midway on the right hand side. BT/Wifi and GPS arrays are separated from these others. Bands 4 & 2 (PCS & AWS) should be able to use similar array spacing so sharing the locations shouldn't be an issue. Similarly BC 12 (lower 700) and BC 5 (Cellular) are also close in frequency to each other, so the antenna spacing is similar (but twice as far as the other pair of arrays). There is no filtering incompatibility issue or duplex issue with Lower 700 / Cellular / PCS / AWS, so it's just a matter of squeezing all the antennas into one (fairly large for a phone) device.

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4ringsnbr and WiWavelength - thanks for the help understanding - this is not my area of expertise.

 

The reason why I am so curious is because apple tries very hard to limit the number of devices they have on the market.

 

I am curious how many different models of the next iPhone they are going to have to make to meet the needs of wireless carriers in the US and across the globe.

 

How many bands/antennas do you think they will be able to cram into the next iPhone?

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