Internet Speed is very low with ppp in modem shell for nrf9160.

Question

I am connecting to Nordic nrf9160 from linux through PPP of modem shell application for internet connection. I am observing very slow internet speed where it is taking approximately 1.30 minutes to download 1MB of data. Below are some test results. 
 
 time wget http: //speedtest.ftp.otenet.gr/files/test1Mb.db 
 Connecting to speedtest.ftp.otenet.gr ( 212.205 . 74.89 : 80 ) 
 saving to 'test1Mb.db' 
 test1Mb.db 42 % |*********************** | 430k 0 : 00 : 49 ETA 
 test1Mb.db 100 % |********************************************************| 1024k 0 : 00 : 00 ETA 
 'test1Mb.db' saved 
 
 real 1m32.443s 
 user 0m0.022s 
 sys 0m0.093s

time wget speedtest.ftp.otenet.gr/files/test1Mb.db 
 Connecting to speedtest.ftp.otenet.gr ( 212.205 . 74.89 : 80 ) 
 saving to 'test1Mb.db' 
 test1Mb.db 45 % |************************* | 463k 0 : 00 : 35 
 test1Mb.db 100 % |********************************************************| 1024k 0 : 00 : 00 ETA 
 'test1Mb.db' saved 
 
 real 1m29.821s 
 user 0m0.018s 
 sys 0m0.092s 
 
 I want to know is there any possibility of increasing the speed? or what speed I am getting here is the expected one from this hardware.

Susheel Nuguru · Accepted Answer

Showed the info you provided to my colleague who has deep understanding on this. Typically getting speeds around 180kb/s (not using PPP) is normal, so these does not look too bad but could have been little better. 
 Try Increasing the shared memory buffers between the modem and application cores might help a bit (look at the Kconfig file for the modem lib). You could also try to increase the baudrate to 1000000, though I don't think the UART interface is what is limiting in your case. 
 For comparison, you can find the peak rates of the physical layer (so the application will see lower numbers) here: https://www.nordicsemi.com/-/media/Software-and-other-downloads/Product-Briefs/nRF9160-SiP-product-brief.pdf?sc_trk={Download%20product%20brief}

Internet Speed is very low with ppp in modem shell for nrf9160.

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