Introduction to cellular technology and related implementation with Embedded Linux

1. 打造自己的IoT
Cellular Technology with Embedded Linux
SZ LIN
szlin@cs.nctu.edu.tw
1
Date: 2016/8/21

2. 2
SZLIN
➔ Taiwan Industrial Grade Linux Distribution
➔ Debian Maintainer
➔ Blog: https://szlin.me
About Me

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8. 8
Prepare Cellular
Interface
Enable device driver
and cellular utility
Get proper
Cellular Module
and SIM card
4321
Steps to Build Your Own IoT
Hands-on Experience

9. 9
Analog Cellular
- AMPS
-TACS
- NMT
* 14.4 kbps
Digital
NarrowBand
Circuit Data
- GSM
- D-AMPS
- PHS
* 9.6/ 14.4 kbps
Packet Data
- GPRS
- CDMA2000
1xRTT
- EDGE
* 171.2 kbps
Digital
Broadband
Packet Data
- UMTS
- CDMA2000
1xEV-DO
* 3.1 Mbps
Digital
Broadband
Packet Data
- HSPA+
- LTE
- WiMAX
(IEEE 802.16e)
* 14.4 Mbps
Digital
Broadband
Packet Data
* All IP network
- LTE Advanced
- WiMAX
(IEEE 802.16m)
* Cat. 6: 300/50
Mbps
1G
2G
3G
4 G
Cellular Network Generation
2.5/
2.75G
3.5/ 3.75/
3.9 G

10. 10
Analog Cellular
- AMPS
-TACS
- NMT
* 14.4 kbps
Digital
NarrowBand
Circuit Data
- GSM
- D-AMPS
- PHS
* 9.6/ 14.4 kbps
Packet Data
- GPRS
- CDMA2000
1xRTT
- EDGE
* 171.2 kbps
Digital
Broadband
Packet Data
- UMTS
- CDMA2000
1xEV-DO
* 3.1 Mbps
Digital
Broadband
Packet Data
- HSPA+
- LTE
- WiMAX
(IEEE 802.16e)
* 14.4 Mbps
Digital
Broadband
Packet Data
All IP network
- LTE Advanced
- WiMAX
(IEEE 802.16m)
* Cat. 6: 300/50
Mbps
1G
2G
3G
4 G
Cellular Network Generation
2.5/
2.75G
3.5/ 3.75/
3.9 G
Taiwan is phasing out 2G cellular on 2017-6-30
to make way for more 4G bandwidth
ref:
http://www.ncc.gov.tw/chinese/print.aspx?table_name=news&site_content_sn=8&sn_f=33421

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Prepare Cellular
Interface
Get proper
Cellular Module
and SIM card
4321
Steps to Build Your Own IoT
Enable device driver
and cellular utility
FAQ

12. 12
BANANA

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BANANA
SoC Built-in
cellular function
Board buit-in
Mini-PCIe slot
Mini-PCIe to USB
Connector

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SoC Built-in Cellular Function

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Board Built-in Mini-PCIe Slot
USB signal

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Mini PCI-E to USB Adapter
With SIM Card and Case Slot
USB signal

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Prepare Cellular
Interface
Get proper
Cellular Module
and SIM card
4321
Enable device driver
and cellular utility
Hands-on Experience

18. 18
LTE frequency bands
➢ 3GPP Release 8 defines 5 LTE user
equipment categories depending on
maximum peak data rate and MIMO
capabilities support [1]
➢ CAT 3, CAT 4 modules took up a dominant
share of cellular market so far
➢ Some new modules start to support CAT6
LTE Category
➢ The definition is in 3GPP TS 36.101
➢ The available band might be different
in different country
Get Proper Cellular Module
Module PIN definition
➢ Make sure the PIN definition between
slot and module are the same

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LTE frequency bands [11][15]

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LTE category [9]
Aggregating up to 40 MHz of bandwidth

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Prepare Cellular
Interface
Get proper
Cellular Module
and SIM card
4321
Enable device driver
and cellular utility
Hands-on Experience

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Data Path Interface
Control Path ProtocolBANANA

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)
* This table only lists information which I have handled

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)

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AT commands - Hayes command set [2][3]
❏ Developed by Dennis Hayes
❏ A series of short text strings which can be combined to produce commands for operations
• dialing
• hanging up
• changing the parameters
❏ “AT” meaning 'attention’

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AT commands - Hayes command set [2][3]
Standard format of AT commands
AT+
Proprietary format of AT commands
AT!, AT^ or AT$ etc..

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AT commands - Utility

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)

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Dial-up by using PPP [5]
Not a Recommended way
6+ steps to dial up with ppp
1. Install the packages in Debian/ Ubuntu
➢ apt-get install netbase ifupdown ppp
2. Create a file /etc/ppp/peers/gprs with this
content
3. Edit /etc/ppp/chap-secrets
4. Edit /etc/ppp/pap-secrets
5. Edit /etc/network/interfaces
6. ifup gprs
7. !@#$%^&*()_
ref: https://c1.staticflickr.com/5/4150/5067471752_1fa8a4ab15.jpg

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Dial-up by using wvdial [6]

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1. apt-get install wvdial
2. edit /etc/wvdial.conf
3. wvdial
Dial-up by using wvdial [6]

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Get IP by using DHCP

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)
serial interface
Non serial interface

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Ethernet Networking Control Model
CDC_ECM + RNDIS - Ethernet over USB [16]
Virtual
Interface
RNDIS
Virtual
Interface
…
Cellular Module – Router mode
IPTABLES - NAT
IP Stack
DHCPDNS➢ RNDIS - Proprietary protocol developed
by Microsoft
➢ “virtual Ethernet” functionality
➢ Support USB high speed
○ Not suitable for the module which
are for more than CAT 6

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Ethernet Networking Control Model
CDC_ECM + RNDIS - Ethernet over USB
Virtual
Interface
RNDIS
Virtual
Interface
…
Cellular Module – Router mode
IPTABLES - NAT
IP Stack
DHCPDNS
Virtual
Interface
RNDIS
Virtual
Interface
…
Cellular Module – Bridge mode
IPTABLES - NATIP Stack
DHCPDNS

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Ethernet Networking Control Model
Driver option in Linux kernel

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Ethernet Networking Control Model
CDC_ECM + RNDIS

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)

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➔ LTE baseband market with 65% [17]
➔ Obsolete AT command and serial
interface
• Compatibility
• Logical Bandwidth
➔ Propose unique value proposition

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QMI (Qualcomm MSM Interface)
◆ Linux Kernel 3.4
• qmi_wwan
◆ Define network services
• NAS (network access)
• PDS (gps location)
• UIM (user identity module)
• WDS (wireless data)
• DMS (device management)
• …
◆ Binary protocol

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QMI (Qualcomm MSM Interface)
Device Driver Owner User-space
GobiSerial
GobiNet
qcserial
option
qmi_wwan
Qualcomm
Open Source Community
GobiAPI
•Sierra Wireless SDK
•…
libqmi (freedesktop.org)
uqmi (openWRT)
ofono (INTEL)

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QMI (Qualcomm MSM Interface)
drivers/net/usb/qmi_wwan.c
➢ Net Driver dependence
➢ Related information

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QMI (Qualcomm MSM Interface)
drivers/usb/serial/qcserial.c & drivers/usb/serial/option.c
➢ Serial Driver dependence
qcserial option

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QMI (Qualcomm MSM Interface)
When to use option instead of qcserial

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QMI (Qualcomm MSM Interface)
Move qcserial to option

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QMI (Qualcomm MSM Interface)
LIBQMI
Mailing lists
libqmi-devel@lists.freedesktop.org

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Control Path Protocol Data Path Interface
1. AT commands
2. QMI (after kernel v3.4 )
3. MBIM (after kernel v3.8)
1. ppp (ttyUSB or cdc-acm)
2. RNDIS (cdc-ecm)
3. QMI (cdc-wdm)
4. MBIM (cdc-mbim)
➔ extends cdc-ncm (Network Control Model)

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Mobile Broadband Interface Model (MBIM)
◆USB-IF Standard (Extends NCM)
• Microsoft
• Intel
• HP
• …
◆Linux Kernel 3.8
• cdc_mbim
◆Binary protocol
◆Raw IP
◆MBIM could embedded different protocols
• QMI
• …

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Mobile Broadband Interface Model (MBIM)
➢ MBIM extends the NCM as a protocol with
the difference that devices transfer raw IP packets
instead of packets with 802.3 headers
➢ NCM
○ 802.3 headers
➢ NCM/ MBIM
○ Raw IP
○ Control path

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Mobile Broadband Interface Model (MBIM)
Device Driver Owner User-space
cdc_mbim Open Source Community libmbim (freedesktop.org)
umbim (openWRT)

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Mobile Broadband Interface Model (MBIM)
LIBMBIM
Mailing lists
libmbim-devel@lists.freedesktop.org

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Prepare Cellular
Interface
Get proper
Cellular Module
and SIM card
4321
Enable device driver
and cellular utility
Hands-on Experience

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ref: http://www.safetysign.com/products/p3249/warning-read-manual-label

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ref: http://www.safetysign.com/products/p3249/warning-read-manual-label

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Use command “dmesg” to find out the
idVendor and idProduct of cellular module.
Use command “grep -r "1199" drivers/net/usb/” to
find out which driver does it use.
Lazy is the greatest motivation behind progress

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Hands-on Experience – FAQ
Dial-up failed !
Check steps one by one
• Check the band of SIM card is matched with cellular module
• Check SIM card is ready or not (Make sure PIN code is correct)
• Check cellular signal is good enough
• Make sure SIM card's supporting band is the same with the cellular module
• Make sure the firmware of cellular module is the same with the ISP
• Make sure cellular module is connected properly to your antenna (MAIN/ AUX)
• Make sure the mode of module firmware is configured properly
• Make sure wireless disable function is OFF

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Hands-on Experience – FAQ
My connection is disconnected !
Check steps one by one
• Check cellular signal from base station
• Make sure cellular module is not in idle mode
• Make sure MTU is configured properly

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Internet
Ping
eth0

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Internet
Open browser
eth0

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Hands-on Experience – FAQ
Make sure MTU is configured properly
This forces the packet to be fragmented, and the fragmented packets are not be re-assembled.
M2M IoT Network Usage Guidelines [25]

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Conclusion
Enable LTE-A module require more fundamental
knowledge
➢ Band, carrier, firmware, antenna, etc…
1
2
3
Future Prospects
➢ MBIM
➢ 3GPP Rel. 12
○ LTE-U
➢ 3GPP Rel. 13
○ LTE-LAA
Fault tolerance mechanism
➢ We cannot control status of base station and carrier

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Thank you

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References
1. E-UTRA
https://en.wikipedia.org/wiki/E-UTRA
2.海斯命令集
https://zh.wikipedia.org/wiki/%E6%B5%B7%E6%96%AF%E5%91%BD%E4%BB%A4%E9%9B
%86
3. Hayes_command_set
https://en.wikipedia.org/wiki/Hayes_command_set
4. Wvdial
https://en.wikipedia.org/wiki/WvDial
5. Modem3G
https://wiki.debian.org/Modem/3G
6. Wvdial - github
https://github.com/wlach/wvdial
7. modem-cmd
https://github.com/imZack/modem-cmd
8. E-UTRA
https://en.wikipedia.org/wiki/E-UTRA
9. LTE UE Category & Class Definitions
http://www.radio-electronics.com/info/cellulartelecomms/lte-long-term-evolution/ue-cat
egory-categories-classes.php
10. Qualcomm Gobi devices in Linux based systems
http://www.lanedo.com/documents/Qualcomm%20Gobi%20devices%20on%20Linux.pdf
11. LTE band
http://niviuk.free.fr/lte_band.php
12. Cellular network
https://en.wikipedia.org/wiki/Cellular_network
13. 1g 2g 2.5g 3g 3.5g 4g comparisons, peak speed, real speed, carriers
https://www.youtube.com/watch?v=_3k5Iic4pWI
14. Project mangOH
http://source.sierrawireless.com/blog/2016/3/next-on-mangoh/
15.長期演進技術
https://zh.wikipedia.org/wiki/%E9%95%B7%E6%9C%9F%E6%BC%94%E9%80%B2%E6%
8A%80%E8%A1%93
16. RNDIS
https://en.wikipedia.org/wiki/RNDIS
17. Qualcomm news
http://www.prnewswire.com/news-releases/abi-research-reports-qualcomm-maintain
s-clear-leadership-in-the-lte-baseband-market-with-65-share-but-faces-mou
nting-captive-market-competition-300222968.html
18. Mobile broadband modem control protocols
http://www.lanedo.com/users/amorgado/talks/FOSDEM2013%20-%20Mobile%20broa
dband%20modem%20control%20protocols.pdf
19. Qualcomm Gobi devices in Linux based systems
http://www.lanedo.com/documents/Qualcomm%20Gobi%20devices%20on%20Linux.p
df

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References
20. libqmi
https://www.freedesktop.org/wiki/Software/libqmi/
21. uqmi
http://git.openwrt.org/?p=project/uqmi.git;a=summary
22. ofono
https://01.org/zh/ofono?langredirect=1
23. Linux Kernel
https://www.kernel.org
24. USB: qcserial/option: make AT URCs work for Sierra Wireless MC73xx
https://patchwork.ozlabs.org/patch/433374/
25. M2M_IoTNetworkUsageGuidelines
https://m2mdeveloper.verizon.com/portals/M2M_Management_Center_
Help/images/a/a2/M2M_IoTNetworkUsageGuidelines.pdf
26. libmbim
https://www.freedesktop.org/wiki/Software/libmbim/
27. umbim
http://lxr.mein.io/source/umbim/
28. LTE-U與LAA發展趨勢介紹
http://www.ttc.org.tw/userfiles/file/20151104/20151104090423_
39805.pdf
29. Special thanks to Glen Chiang