Dear Sierra Wireless,
EM7565 Technical Specifiaction describes that it does not support LTE Band38. (TDD/ 2570MHz – 2620 MHz )
We have noticed that EM7565 is supporting LTE Band41 (TDD/ 2496MHz – 2690 MHz).
So based on the frequency ranges it seems like Band38 would be a Subset of Band41.
Would it be correct to assume the EM7565 could also support LTE Band 38?
If not, is there a SW Firmware or Set-Up Change that could enable the modem to Support LTE Band38?
We should probably update our PTS.
Let me clarify this with the FW guys and get back to you.
any luck clariying this question with your FW guys?
Cheers and Happy New Year,
I didn’t forget about your question.
I’ll give you an answer by early next week.
I have the answer.
“Would it be correct to assume the EM7565 could also support LTE Band 38?”
No it’s not.
We do not support B38.
Overlapping bands are not the same as dedicated band support.
The impact is mostly on NTWK acquisition.
thank you for looking into this topic. There is stong interest for aeronautical use cases to support LTE Band38.
Could you please explain what you are trying to state as the reason why band 38 is not supported?
According to documentation the large majority of devices supporting band 41 also support band 38 and the small difference may only be based on unavailable full spec for 5+ years old devices.
Simply stating “network acquisition” as the main reason is not fully valid without providing any hint to the required documentation/agreements/3GPP-documentation.
Network acquisition comprises of several steps and is mainly driven by firmware:
Step-1: After being powered on, UE tunes the RF and attempts to measure the wideband received power (RSSI) for specific frequencies (channels as commanded by higher layer) over a set of supported frequency bands one after another and ranks those cells based on signal strength.
Is the stated “missing support of band 38” a deficiency in the sierra wireless firmware for this modem?
Band 41 is stated as supported but it is a strange band. With 194 MHz it does not fit a full number of 5, 10, 15 or 20 MHz channels (and according to “the Internet” only 5 to 20 MHz channels are allowed here) thus there needs to be either some special agreement or detailed cell-search method.
Band 38 is other than band 41 a well-defined band with 50 MHz fitting a full multiple of 5 MHz channels and allowing different combinations of 10, 15 and 20 MHz channels with easily identifiable channels where core blocks containing PSS and SSS would be located. Cell search is thus quite easily done as the number of possibilities is quite low.
With band 41 covering 194 MHz the locations of 5 MHz channels are not logically predefined as 194 MHz need to waste 4 MHz to get to a band width fitting a full multiple of 5 MHz channels. I could not find a general agreement how to place the channels into a basic layout in band 41. This would lead me to the basic requirement of LTE where a carrier may be placed in any slot of the 200 kHz pattern (given that the channel width allows it).
For band 41 the cell search algorithm would not be able to start with an easy basic pattern of logical 5 MHz channel layouts but cover most of the possible 5 MHz channels searching for spectral power, PSS and SSS.
When the band 41 layout started using 2496 MHz as the lower there would not be any overlap in PSS and SSS RBs with band 38.
Also, considering that the lower 4 MHz of band 41 are also used by RADIODETERMINATION SATELLITE (space-to-earth) I doubt that this could be used for MOBILE without any impact on SATTELITE service as defined. Therefore it would make sense that band 41 active transmissions would start at 2500 MHz where then 190 MHz bandwidth would allow for clean multiple of 5 MHz channels and allowing a PSS/SSS matching overlap with band 38.
- Could you please clearly state what is missing and why the sierra wireless firmware does not support band 38?
- Is it planned to close this gap?
- Could you please provide the strategy followed by the modem for cell search considering that it has no idea in which region it is currently located and also that it can’t disregard any band supported unless the user removed it from the set of allowed bands in the configuration?
- Are there channels pre-defined in the firmware (for each band)?
- How long does a full all-bands search take?
The questions you have asked re search algorithms are highly complex and dependent upon multiple factors (both internal and external) making it impossible to answer them with any certainty. I will give you some broad guidance though assuming the unit is powering up with a new SIM that it has not seen before is inserted (meaning a lot of settings are cleared out).
- Power on and sequentially search each enabled band (all by default) on the highest enabled bearer (LTE by default) for the LTE pilot signals, then switch to 3G (assuming it has just done LTE) and do the same.
- If it sees its home network immediately attempt to attach (within the above search pattern).
- If it does not see its home network attempt to attach any of the networks on the preferred operator list contained on the SIM.
- If it does not see any of these then go for each NW it sees in turn.
How long this takes depends upon network response times and how many networks it can see. The more networks the longer it has to listen to get the required information before it can move to the next.
With regards our position on band 38.
- As James has stated we do not support it even though from an RF stand point the unit might do so.
- This position is borne from the lack of commercial deployments using B38 hence no commercial value in terms of units we would be able to sell.
- No testing performed and no exploratory work done with Qualcomm over whether or not the chipset or firmware is in place or available to operate on it successfully (its not just a case of hooking it up to a B38 network simulator and saying yes it attaches, there is significant levels of validation and certification required before we can declare it works).
- No there are no current plans to close this gap.
We have engaged with your company directly with regards LTE and I have passed your details onto the guys who are discussing with them.