Sharing the LTE data through Wi-Fi

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Before sharing the network, some additional routing has to be performed on the UE. Thanks to the SPGW’s built-in SNAT functionality, the outgoing packets from the private LTE network are allowed to go to the Internet. When a commercial UE attaches to the network, it is given an IP from the IP address pool, configured with the network’s DNS, and is then able to access the Internet by going through a default gateway which performs SNAT. The UE, however, is not properly configured when it attaches to the network. After the attach procedure is complete, a virtual network interface named oip1 is created and assigned an IP from the IP address pool. In this state, one can ping external IPs (e.g. Google DNS servers: 8.8.8.8) to test if the network is working, but it is not possible to browse the Internet. Some modifications are required.

First of all, a default IP route gateway should be assigned to the new network interface, oip1. Currently and unlike the commercial UEs, OAI UE is also not properly assigned with the network’s DNS primary and secondary address. This can be solved by using a proxy, or by just adding the DNS configurations manually to the OAI UE’s computer. As all configurations are known, the second option is chosen. After a network restart, the user should now be able to browse the Internet.

Now that the Internet is properly configured, the UE can run as is, but the ultimate goal of this dissertation is to have a device that provides Internet to multiple users. There are three options, discussed in the following subsection.

5.5.1 Sharing the network

The network can be shared with other users by using an Ethernet cable connected to a single computer or an AP/router, or by using the computer’s Wi-Fi module to create an hotspot. The last two options were tested.

When running the UE on a computer, the network was shared through the built-in Wi-Fi module. Using Ubuntu’s Network Manager GUI, it’s possible to create a Wi-Fi hotspot that shares the computer’s existing connection with others. If no password is configured, a free hotspot is now available.

When running the UE on a SBC, the network was shared by an Ethernet cable connected to the LAN port of an AP. The Ethernet port can be configured by manually routing and using SNAT, or with the Network Manager, by configuring the Ethernet port to share the computer’s network. When configuring the AP, the Local Area Network (LAN) is config- ured as 10.42.0.2 and it is critical that the Dynamic Host Configuration Protocol (DHCP) functionality is disabled, otherwise it won’t work. Again, if no password is configured, a free Wi-Fi hotspot is now available.

This chapter described the implementation of a reconfigurable LTE network that can be interfaced with a commercial UE or a software-defined radio UE for different radio configura- tions modes. After being successfully attached to the network, the UE will be able to share its LTE mobile connection with the surrounding devices, by creating a Wi-Fi hotspot.

The non-conventional scenarios described in Chapter 4 could all be deployed with the implementations described in this Chapter. For the catastrophe and remote location scenarios, the eNB could also be condensed into a smaller but powerful computer, like the Intel NUC, and the EPC ran in a virtualized environment. This way, this LTE implementation could be dropped anywhere it was required and provide access to the Internet.

For the other scenarios (opportunistic use of TDD bands, unlicensed spectrum and in- vestigation infrastructures), the current implementations would suffice, at least for testing purposes.

Chapter 6

Results

This chapter begins with an introduction to the implemented setups and the measurements that will be performed, in section 6.1. Afterwards, the setup is described in section 6.2, along with the tools used for testing. Then, the test results are presented for the different implementations: section 6.3 for the commercial UEs, section 6.4 for the UE running on an Intel NUC mini-computer and section 6.5 for the UE running on the single-board computer UP Squared.

6.1

Introduction

Regarding the main purpose of this dissertation, which is the ability of having a compact, flexible and fully reconfigurable UE that works in a number of previously described scenarios, it is of great importance that the implemented setups can provide a reliable service to the user. If possible, the user should be able to browse the Internet, watch videos on Youtube, make Skype calls and so on.

Three major implementations were deployed. The only network element that varies with each implementation is the UE. First, a commercial UE is used, moving on to an UE running on Intel’s NUC mini-computer and finalizing with it running in a single-board computer. The implementation with a commercial UE is the one that supposedly works best in OpenAirIn- terface (OAI), so it will be used as a reference on what results the others should achieve.

To evaluate the performance of each implementation, throughput and latency measure- ments were performed, along with the visualization of software oscilloscopes (softscopes) containing, for example, a representation of the received signal in dB or the constellations of different physical channel modulations. Additional entities are also taken into account and are reported by the UE to the eNB. These are the Power Headroom Report (PHR) and the Channel Quality Indicator (CQI), and will be described in the following section.

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