Implementation of Dynamic Resource Allocation for LTE System Using GNU Radio

Abstract

Nowadays, the fourth generation mobile communication is being popularized all over the world. As the core technologies, OFDM and MIMO are being widely researched and attracting more and more people to make them perfect. Dynamic resource allocation for OFDM is one of the research topics in the field of OFDM technology for Long Term Evolution (LTE) standard. In order to dynamically allocate resource to multiple users with different purposes, there is large number of algorithms used in specific situations. On the other hand, a universal technology named Software Defined Radio (SDR) is rapidly developing for signal processing and wireless communication. With more flexibility and lower cost, SDR, especially GNU Radio, are widely used for researching and building portable communication devices. This thesis combines LTE and GNU Radio technology. This thesis consists of two parts: one is a study of the important issues in wireless communication and dynamic resource allocation for OFDM based systems; the other is the implementation of a simplified signal processing structure for an LTE communication system using GNU Radio. Within this signal processing structure, the dynamic resource allocation algorithms are embedded in the OFDM modulator. In this thesis, we choose three typical dynamic resource allocation algorithms: Max-Sum, Max-Min and Nash Bargaining Game. We assume a general LTE network with one eNodeB base station and multiple user devices. Max-Sum algorithm maximizes the total throughput of the network since it only allocates channels to those users who have the best channel gain. Max-Min algorithm maximizes the worst user device rate to guarantee that the user device which is in the worst channel environment can obtain an opportunity to access to the network and maintain an acceptable quality of service. Nash bargaining game algorithm maximizes the product of the rates of each user device. This algorithm provides an approach to enlarge the total throughput and guarantees the fairness of the occupancy for each user devices. Using GNU Radio to implement dynamic resource allocation requires a large amount of prerequisites. GNU Radio, a kind of Software Defined Radio framework, provides a C++ library for signal processing. It provides GNU Radio Companion (GRC) for researchers to build a signal processing flow graph for a specific task. GRC translates the flow graph to Python codes and the Python script calls the compiled C++ programs which process the signals in encapsulated blocks. Based on the rules of GNU Radio development and some built-in signal processing modules, we build the OFDM modulator and demodulator for downlink communication and the SC-FDMA modulator and demodulator for uplink communication, which are the technologies adopted by the LTE standard. More important, we design and build the base station and user device to simulate real situations in which people use mobile phones to send requests and get information. Then, the three dynamic resource allocation algorithms are embedded in the resource allocation module of the base station to study the differences among them.