Overview
1.1 System Overview
LokaLTE simplifies implementation and configuration of the Evolved Packet Core (Core Network) elements of an LTE network. The EPC provides core software functions such as subscriber management and routing user traffic to the network monitoring, web-based administration, and local web and DNS serving/caching and Internet. It connects to the radio “base station”, called the eNodeB (Radio Access Network), which then talks to the User Equipment (UE)- i.e., your cell phone or access device.
Since the LokaLTE targets small communities in rural areas, the design of the system uses open-source solution to develop a low-cost small community LTE base station. The LokaLTE base station works by using a Software Defined Radio to serve as the eNodeB of the system to provide connection from the User Equipment to the Core Network. SDRs have very good advantages in developing a base station transceiver due to its reconfigurability in contrast with the radio units used by the commercial telecommunication systems.
The first factor in the creation of an LTE cellular network is the Radio Access Network (RAN) or the eNodeB. The function of the eNodeB in the system to establish Radio Frequency (RF) connection from the User Equipment (UE) to the LTE cellular network. The LokaLTE used an open-source eNodeB software from srsLTE. The srseNB will function as the RAN of the LokaLTE for it to establish a connection to Ues capable of transmitting and receiving data from LTE Band 71, which is 617 MHz – 698 MHz. SrseNB is used to configure the transmitter/receiver gain, E-UTRA Absolute Radio Frequency Channel Number (EARFCN), the Bandwidth (BW), Mobile Country Code (MCC), Mobile Network Code (MNC), Mobility Management Entity (MME) IP address, S1 Interface address and GTP address.
The LokaLTE project requires a framework to provide voice and data for LTE network, hence the use of Open5GS’s open-source Evolved Packet Core is used. Under the EPC framework are the different instances for the network. It functions as a user database, authentication of the Ues if the requirements are met, regulates and charges the data usage of the user, and to ensure the connection of the User Equipments (UE) to the backhaul. The LokaLTE uses the following instances from Open5Gs:
MME – Mobility Management Entity
HSS – Home Subscriber Server
PCRF – Policy and Charging Rules Function (backed by Haulage and LokaLTE Portal)
SGWC – Serving Gateway Control Plane
P-GW – Packet Data Network Gateway
The EPC hosts several servers that can be accessed without using data from the Backhaul, and not charged by the PCRF. Accessing the servers such as LokaLTE portal, LokaFlix, and OpenSource Speed Test will not consume data charges by the EPC.
Another factor the LokaLTE considers is the limited data bandwidth from the backhaul. The LokaLTE will use a caching proxy server in order to reduce data usage. The squid proxy will determine the rules, caching content rules and the network monitoring data and graphs. The primary function of the squid proxy is to prevent the repetitive gathering of data from the World Wide Web through the backhaul which could lead to inefficient use of limited bandwidth of the backhaul network. Another function of squid proxy is to prevent unnecessary data usage of the advertisements as well as contents that are not safe for kids.
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