Simple LTE Tutorial

Using the LTE testbed

In order to use the LTE testbed resources offered by the NITOS facility, first you will have to create an account here and follow this tutorial. Then you will be able to reserve the LTE eNBs and the nodes with LTE connectivity, offered by the Outdoor and Indoor RF isolated testbeds.

Reserving the eNBs will render rights to the experimenter to access the LTErf service of the NITOS facility, used to configure and setup the eNBs and the EPC at the experimenter's will.

After your reservation has started, log in to the NITOS3 server with the following command:

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Load image to nodes

Once you have logged in, you have to load the image baseline_icarus_lte.ndz to the nodes that you reserve with the following command:

omf load -i baseline_icarus_lte.ndz -t omf.nitos.node0xx,omf.nitos.node0yy

and to turn them on:

omf tell -a on -t omf.nitos.node0xx,omf.nitos.node0yy

Check which base station your are using

In order to start experimenting with the LTE components in NITOS, you have first to find out which eNodeB you will be using. In general, node 1 is the outdoor NITOS eNB (currently offline for maintenance) and node 2 is the indoor NITOS. Other entries might exist for test purposes with OAI.

In order to check the available eNodeBs and their IP addresses, you have to send the following command to the service:

wget -qO- http://lterf:5054/lterf/bs/list

which should reply something like the following:

AP Number : 1 | Type of BS : ipaccess | Ip : 10.64.44.52 | Management Iterface : eth1
AP Number : 2 | Type of BS : ipaccess | Ip : 192.168.200.1 | Management Iterface : eth0
AP Number : 3 | Type of BS : oai | Ip : 10.64.44.56 | Management Iterface : eth1

The indoor testbed is using the 192.168.200.0/24 network for the network between the eNodeB and the EPC network. For the indoor testbed, AP number = 2 should be used for altering the base station components, by appending node=2 to all the commands sent to the LTErf service.

Restart Basestation

It is important to setup the eNBs to the default settings, as their configuration might have been altered from their normal behavior by any previous experimenter. In order to setup the eNB to the default settings you issue the following commands:

 wget -qO- 'http://lterf:5054/lterf/bs/config/load?name=reset&&node=2'

Since not all of the changes take place immediately, you will need to restart the eNB for some of the changes to take effect. You can restart the eNB with the following command:

 wget -qO- 'http://lterf:5054/lterf/bs/restart?node=2'

Which will return you the message:

... has been restarted

Restart EPC

In order to setup the EPC to the default settings you issue the following command:

 wget -qO- 'http://lterf:5054/lterf/epc/config/load?name=setDefaultEpc'

NOTE: As NITOS is currently upgrading to control multiple remote femtocells, please issue the following command to switch using the indoor testbed before restarting it. You can do this with the following command:

 wget -qO- 'http://lterf:5054/lterf/epc/config/testbed?name=indoor'

You will need to restart the EPC twice in order for some of the changes to take effect. You can restart the EPC with the following command:

 wget -qO- 'http://lterf:5054/lterf/epc/restart'

Which will return you the message:

EPC network has been restarted

There are some cases where the EPC is restarted but not all of the EPC compoenents are interconnected. You should check if the EPC is working by sending the following command:

wget -qO- "http://lterf:5054/lterf/epc/get?function=getSystemStatus" | xml_pp

If everything is working correctly, you should see an output where all the components report connected. If at least one of the components SGW, HSS, PGW is not connected, try restarting the EPC again.

Check if all components are connected

In order to check if the eNB is connected to EPC after the restart you will have to type the following command:

wget -qO- 'http://lterf:5054/lterf/epc/get?function=getSystemStatus&args=MME,S1AP_INTERFACE,192.168.200.1' | xml_pp

Which will return you the message:

<STATUS>
  <EPC>
    <getSystemStatus>
      <instance id="1">
        <componentType>MME</componentType>
        <currentStatus>CONNECTED</currentStatus>
        <lastUpdated>2015-05-21T13:49:52Z</lastUpdated>
        <statusType>S1AP_INTERFACE</statusType>
        <statusIdentifier>192.168.200.1</statusIdentifier>
        <severityLevel>0</severityLevel>
      </instance>
    </getSystemStatus>
  </EPC>
</STATUS>

You can see the parameters that can be changed and the LTERF service commands and their syntax by invoking the following command:

 wget -qO- 'http://lterf:5054/lterf/' | xml_pp

It returns an XML tree with the complete list of LTERF commands. Since the eNB and EPC are back to their default settings, you can start experimenting with the LTE testbed.

Connect to the LTE network

Using AT commands

ssh root@node0xx

You will have to first turn the LTE dongle on. You can do this by running the following command on the node console:

root@node0XX:~# lte_dongle -o -v

The "-o" argument can be used to turn the USB on/off, while the -v is used for the verbose output at the console. You can use the "-h" argument for a complete list of the available commands.

Once the dongle is connected, you can see it listed with the lsusb command. The output should look like the following:

root@node0XX:~# lsusb | grep Huawei
Bus 001 Device 008: ID 12d1:1506 Huawei Technologies Co., Ltd. E398 LTE/UMTS/GSM Modem/Networkcard

And a wwan0 device should be attached on the node.

NOTE: Multiple restarts of the dongle might cause the huawei_cdc_ncm driver not to attach correctly and therefore no wwan0 interface will be available. In such a case, reboot the node.

Next step is to connect to the LTE dongle using the minicom application. The port that can be used to setup the LTE interface depends on the USB LTE stick model. In order to check the LTE stick model number, connect with minicom over the port /dev/ttyUSB0 (or USB1, depends on the LTE Dongle type (for more information see the list below)) and run the following commands:

root@node0XX:~# minicom -D /dev/ttyUSB0
ATE
ATI

The "ATE" command will enable the local-echo to the output console, so that you can see what you write, and the "ATI" command will return to you some information about the LTE dongle.

The following dongles are available in NITOS, with the respective ports that can be used for configuring them:

LTE Dongle type	Port used for configuration
Huawei E398	/dev/ttyUSB0
Huawei E3272	/dev/ttyUSB1
Huawei E3372	/dev/ttyUSB0

In order to configure it exit minicom and restart it using the port as an argument

root@node0XX:~# minicom -D PORT

In order to turn on the air interface:

at+cfun=1

Add a new APN and activate the PDP context:

at+cgdcont=1,"IP","default"

at^ndisdup=1,1,"default"

at+cgatt=1

at+cgact=1,1

at^dhcp?

If the last command outputs a string with numbers in HEX, the dongle should have received the IP address from the EPC DHCP network. You can now exit from minicom and configure the wwan0 interface with the ip 10.0.3.xx. Generally, the last digits for the IP address are the same as the node ID (e.g. node077 gets the 10.0.3.77/24 IP address).

If at^dhcp is giving you an error or just reports "OK", then the modem is not in a state to connect. To do so, bring down the air interface and re-activate it by using the next set of commands:

AT+CFUN=0
AT+CFUN=1

You can now wait for the modem to report

^SRVST=2

If it is in such serving state, the modem can connect to the network, so you can re-send the previous set of commands for adding the APN and connecting to the network.

Once AT^DHCP is reporting you the IP address received from the LTE network, you can setup the network interface. To do so, exit minicom (Ctrl+a followed by Ctrl+x will show you the exit window) and send the following command from the node console:

root@node0XX:~# dhclient wwan0

Once the dhclient command exits, the wwan0 interface should have an IP address. However, the system by default is assigning automatically a subnet mask equal to /30. You can overcome this by sending the following commands:

root@node0XX:~# ifconfig wwan0 netmask 255.255.255.0 -arp up

Now you should be able to ping the PDN-GW component of the EPC network (the default configuration uses the 10.0.3.1 IP address) or any other LTE client connected to the network.

The LTE interfaces can get in an IDLE state when you do not send any traffic over the network. If this is something that you do not want, you can have a ping running in the background, pinging the EPC network.

Performing Downlink experiments

If you decide to keep the LTE default configuration, performing DL/UL experiments can be a lttle tricky. The overall architecture of the NITOS LTE network is based on the 192.168.200.0/24 network for the communication between femtocells and the EPC network. This network, is also attached to each node's experimental network.

In order to do DL/UL experiments involving the wired experimental network, you will need a testbed node that has an IP address from the 192.168.200.0/24 network configured for the experimental interface. To do so, log in on a node and send the following commands:

root@node0XX:~# ifconfig eth1 192.168.200.XX/24 up
root@node0XX:~# route add -net 10.0.3.0/24 gw 192.168.200.200

Now you have configured the receiving node to send and receive traffic to/from the LTE network by using the EPC (192.168.200.200) as the default gateway.

You will have to configure routing on the LTE node as well, as follows:

root@node0XX:~# route add -net 192.168.200.0/24 gw 10.0.3.1

Now the LTE node will use the EPC PDN-GW as the default gateway for sending traffic to the 192.168.200.0/24 network. You should be able to ping each side and do DL/UL experiments with any available traffic generator.

Other LTErf configurations

The LTErf service is used for configuring the base stations, EPC networks and datapath configurations in the LTE network. The service is supporting several configurations. All the available services can be retrieved from the LTErf service using the following command:

wget -qO- "http://lterf:5054/lterf/" | xml_pp

In the following articles a complete list of the possible configurations per building block are illustrated:

You can also check out the rest of the available LTE tutorials.

Using OMF

Instead of using the AT-Commands to setup the LTE dongle, you can use the OMF to automatically setup the air interface for you. If you are not familiar with OMF, please refer to the OMF-related pages in this site.

An example of an OMF experiment used to generate traffic in the NITOS testbed, using the LTE enabled nodes is the following:

defGroup("Sender","omf.nitos.node066"){ |node|
	node.addApplication("iperf-5.4", :id => 'iperf') {|app|
		app.setProperty('port', 5200)
		app.setProperty('bandwidth',"100000000")
		app.setProperty('udp',true)
                app.setProperty('time', 100)
		app.setProperty('client', "10.0.3.77")
		app.setProperty('reportstyle', 'o')
		app.setProperty('interval', '1')
		app.measure('transfer', :samples=>1)
		app.measure('losses', :samples=>1)
   }
	#Configure LTE dongle
        node.net.l0.radio = "on"
	node.net.l0.apn = "default"
	node.net.l0.attach = 1
	node.net.l0.connect = "default" #Connect and set up wwan interface
}
defGroup("Receiver","omf.nitos.node077"){ |node|
	node.addApplication("iperf-5.4", :id => 'iperf') {|app|
		app.setProperty('port', 5200)
		app.setProperty('server', true)
		app.setProperty('udp',true)
		app.setProperty('reportstyle', 'o')
		app.setProperty('interval', '1')
		app.measure('transfer', :samples=>1)
		app.measure('losses', :samples=>1)
   }
	#Configure LTE dongle
        node.net.l0.radio = "on"
	node.net.l0.apn = "default"
	node.net.l0.attach = 1
	node.net.l0.connect = "default" #Connect and set up wwan interface
}
onEvent(:ALL_UP_AND_INSTALLED){ |event|
 	info "Configuring the LTE dongles"
        wait 80
	info "Starting iperf server-client"
	group("Receiver").startApplication('iperf')
	group("Sender").startApplication('iperf')
	wait 60
	info "Stoppping all applications"
	group("Receiver").stopApplications
	group("Sender").stopApplications
	Experiment.done
}

You can refer to a complete description of the experiment to the following video: