Enhancing Mimo Technology Performance

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Enhancing MIMO Technology Performance

Mr. Mushtaq Ahmad & Muhammad Shoib Gul

Department of Graduate Studies and Applied Sciences , Bahria University, Islamabad, Pakistan.

mushtaq_bit9@yahoo.com

mushtaq.ahmad91@gmail.com

Abstract--WiMAX (IEEE 802.16m) and Long Term Evolution (LTE) are the two main candidates for 4G. Majority of the worlds operators and venders are already committed to the LTE and WiMAX (IEEE 802.16m) deployment developments. Multiple input output (MIMO) Technologies introduced in WiMAX(IEEE 802.16m) and LTE Advanced such as precoding, transmit diversity , beamforming, and spatial multiplexing are key technologies for provide high throughput and link range at a better system efficiency. This paper also described a simulation study of the transmit diversity technology, which improve data transmission in multipath environments, this simulation result is base on spatial diversity and pattern diversity techniques and also point out three effects through which MIMO capacity increase.

Index Terms- Global Software Engineering, Data Mining, Risks Management

I. INTRODUCTION

A promising way of achieving high data rate in wireless communications is to use multiple antennas at both the transmitter and the receiver, forming a multiple input multiple output system. Worldwide Interoperability for Microwave Access (WiMAX) is the common name associated to the IEEE 802.16a/REVd/e standards [1] but with exponential evolution in the field of Network and Telecommunication a new standard WiMAX (IEEE 802.16m) has recently been introduced and become a research focal point for most of the researcher now. WiMAX provide OFDM based physical layer, Very high data rates and reliability through MIMO , Scalable bandwidth and data rate support, Adaptive modulation and coding (AMC), Support for TDD and FDD, Orthogonal frequency division multiple access (OFDMA), Flexible and dynamic per user resource allocation, Support for advanced antenna techniques, Quality-of-service support, Robust security, Support for mobility, IP-based architecture,capacity and flexibility over existing legacy networks .

On the other hand a new technology Long Term Evolution (LTE) Advanced belong to 3rd Generation partnership project (3GPP) provide MIMO based antennas system which increase distinctly the system performance and LTE Advanced also become the competitor of WiMAX (IEEE 802.16m) technology. its main features are High Data Rate and spectral efficiency (OFDM,MIMO),low latency, flexible bandwidth [2].one of the main problems faced by the world developing standard is providing high throughput at the cell edge without increasing average transmit power and frequency bandwidth and the 2nd problem is define as multiple received replicas of the transmitted signal sometimes combine destructively and signal over lay resulting in local deep dips called Rayleigh fading[4] . In this research we work on the 2nd problem so we evaluate the benefits of transmit diversity in MIMO system because one solution to overcome this problem is the use of antennas diversity.

MIMO technologies are used by both WiMAX and LTE combine for improving data rate and system performance. MIMO technologies offers allot of features, which includes, Fast delivering , Mobile broadband services reliably over extended coverage area, Increase data throughput, Increase link rang, Interference suppression, Diversity gain, Cell coverage.

To get all this divergent set of objectives, LTE and WiMAX adopted various MIMO technologies such as transmit diversity, dedicated beamforming, Coordinated multi-point (CoMP), single user (SU)-MIMO, multiuser (MU)-MIMO and closed-loop rank-1 precoding [3]. All these Technologies are differing from each other by using different techniques including beamforming, precoding, diversity coding and spatial multiplexing.

In this paper we present a simulation study to investigate performance of Transmit diversity technology scheme in MIMO technologies to improve data transmission in multi-path environments. The data transmission increase can be achieved by three effects including increase of the Signal-to-Interference-and-Noise Ratio, Spatial multiplexing, a diversity gain.

The reminder of this paper organized as fellows. First we briefly describe the transmit diversity technology scheme in MIMO technologies. Then the main characteristic of this technology in MIMO. Finally we offer simulation of the antenna placement to get better diversity in multipath propagation and provide our mean conclusions and results.

II. BACKGROUND KNOWLEDGE

The transmit diversity technology can be applied to all the physical channel in downlink of LTE [3] and WiMAX, in uplink now four antenna used for the selection of good diversity.

Diversity is achieved by creating several independent paths between the transmitter and receiver. In above 2nd problem in which multipath signal fading is one of the most fundamental features of wireless channels. Because multiple received replicas of the transmitted signal sometimes combine destructively and signal overlay resulting in local deep dips called Rayleigh-Fading [4]. Multiple antennas diversity overcome this problem. The receiver of independent copy of same signal by each element in the receive array is the basis of receive diversity . The probability decrease that all signals are in deep fade simultaneously.

Figure 1: antenna diversity

Transmit diversity is base on multiple transmitter and receiver antennas. MIMO technologies is based on both transmit and receive diversity. MIMO and transmit diversity increase the performance of present and future wireless communication systems, in MIMO transmit diversity is based on space-Frequency Block coding (SFBC), combine with Frequency Shift Transmit Diversity (FSTD) in case of four transmit antenna [5]. Transmit diversity is intended for common downlink