INTRODUCTION

The early mobile systems (1G - 1st Generation) emerged in commercial scope in the 1980's, but it was in this last decade that the mobile communication became irreplaceable for the society. The 2G (2nd Generation) and 3G (3rd Generation) technologies are now world spread and with the prices of the phones getting cheaper it makes even easier to people to get access to these technologies.

The continuous demand for higher speed and connectivity makes necessary a continuous evolution of the communication systems. The LTE-A (Long Term Evolution Advanced) is the technology that will represent this next generation of mobile services. It is a standard developed by 3GPP (3rd Generation Partnership Project) that will improve communication performance, increasing data rate and link range without increasing transmit power or bandwidth. This coursework will describe the project of a 4G LTE radio network in a given city. It will cover all the details about the network design, such as:

- Number and position of the transmitters
- Number of cells and cell coverage
- Carrier frequency
- Bandwidth
- Path lost and interference issues

The project will be developed using the software Wireless InSite. It is a wireless communication planning software that can simulate the proposed network and return the feedback necessary to evaluate its performance.

BACKGROUND

On this section I will present all the necessary coursework background. I will begin with an overview on the history of mobile communications, starting with 1G and going until 3G. Them I will introduce the LTE technology that will be the next generation on mobile communication. Finally I will present the scenario that was given for the project of a 4G LTE network. History of Mobile Communication

1G - First Generation

The first generation of mobile telecommunication is also known by the acronym 1G. This technology came out in the 1980's and by dividing the area to be covered in cells made possible to accommodate a large number of people, since the same frequency could be reused many times. In the 1G system, the voice was modulated in a higher frequency, usually over 150MHz. The use of analog signals for voice transmission led to problems like [1]:

- It's very hard to use advanced encryption methods in analog signal. The lack of security makes possible listening to other people's call or stealing their ID and makes phone calls in their names.
- The quality of the signal is compromised since analog signals are way more susceptible to interference than the digital ones.
- The use of the spectrum is inefficient, since each carrier is dedicated to a single user (active or idle).

2G - Second Generation

To overcome all the deficiencies of 1G network the 2G systems were proposed. 2G systems are completely digital, what solves all the problems created by the use of analog signals. This way is possible to encrypt the signals, to use error detection and correction techniques and to share a carrier among more than one user (using different codes or time slots) [2]. It allows the use of Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). Among the different 2G standards the most important of them is the GSM (Global System for Mobile Communications).

GSM is a European 2G standard. Its commercial development started in 1991, becoming popular worldwide. The first system to be used had an operating frequency of 900MHz, with future variants in 1800MHz, 1900MHz and 450MHz. GSM also supports data connection, with rates up to 9.6kbps. The architecture of a GSM network can be illustrated by the following diagram (Figure 1).


Figure 1: 2G Network

SIM: Subscriber Identity Module
BTS: Base Transceiver Station
BSC: Base Station Controller
BSS: Base Station Subsystem
MSC: Mobile Switching Centre
HLR: Home Location Register
VLR: Visitors Location Register
AuC: Authentication Centre
GMSC: Gateway MSC
PSTN: Public Switched Telephone Network

3G - Third Generation

2G networks could obtain a huge success in the market. The technology was great at supplying the demand for voice communication services. With the increase in popularity of multimedia and internet services 2G systems couldn't provide a satisfactory bitrates. It is solve this issue that the 3G systems come into scene. They would provide 144kbps (full mobility applications in all cases) up to 2Mbps (low mobility applications in the micro and pico cellular environments). Its communication spectrum is between 400MHz and 3GHz [3].

3G systems support symmetric and asymmetric traffic, packet-switched and circuit-switched services, global roaming, among other features.

LTE - Next Generation Mobile

LTE is a standard of mobile communication developed by 3GPP that has the goal of being the next generation of mobile communication. It was submitted as 4G system candidate and approved by the ITU (International Telecommunication Union) as meeting 4G requirements on the release 10, also known as LTE-A [4].

Different from 2G, using TDMA and FDMA, and 3G, using CDMA, LTE uses OFDMA (Orthogonal Frequency-Division Multiplexing Access) as multiple access technology. On OFDM (Orthogonal Frequency-Division Multiplexing) the signal to be transmitted is decomposed on ‘n' signal (it can be done using a serial/parallel converter). These signals are them multiplied by an exponential, each one with a frequency orthogonal to the others. Then, all of them are summed and transmitted. It can be seen on Figure 2 [5].


Figure 2: OFDM transmission OFDMA is an extension of OFDM. On OFDMA the subcarriers are distributed among many different users at the same time, making possible multiuser communication.
Other advance that LTE systems have is the use of multiple antenna technique. LTE is the first global mobile cellular system to use MIMO (Multiple-Input Multiple-Output) technology. The use of multiple antennas can improve significantly the communication performance through a greater channel capacity. A model of a MIMO system is shown on Figure 3 [6].


Figure 3: MIMO System The LTE-A performance can be seen on Figure 4 [7].


Figure 4: LTE-A performance