New Transmitter/Receiver Diversity Scheme in DVB-H systems over Outdoor and Indoor Environments Yue Zhang School of Engineering & Design, Brunel University, UK Yue.Zhang@brunel.ac.uk John Cosmas School of Engineering & Design, Brunel University,UK John.cosmas@brunel.ac.uk Maurice Bard Broadreach Systems Communications Ltd, UK mail@broadreachSystems.com YongHua Song School of Engineering & Design, Brunel University,UK Yh.song@brunel.ac.uk Abstract The objective of this paper is to research and develop novel diversity techniques for broadcast transmitter networks that will minimise the complexity and power consumption of end user equipment. Transmitter Diversity will improve reception in areas of poor coverage such as for mobile reception, indoors and sparsely populated or obscured locations. Rapid development in the area of broadband wireless communications demands wireless multimedia services. One of the challenges of transmitting multimedia over wireless channels is that fading and interference can severely deteriorate the received signals. Orthogonal Frequency Division Multiplexing (OFDM) is a suitable technique for broadband transmission in such environments and is implemented in broadcast standards such as DVB- T/H and DAB. DVB-T/H and DAB are key radio broadcast network technologies, which are expected to complement emerging technologies such as WiMAX and its derivatives in future 4G networks. However, because of the poor error performance of OFDM in flat fading environments, it is necessary for wireless communication systems to use spatial diversity to improve the error performance and channel capacity. And complexity and power consumption of personal receiving devices can be optimized by improving the transmission of signals in non line of sight cluttered environments using transmit diversity. Transmit diversity exploits the statistical nature of fading due to multipaths and reduces the likelihood of deep fading by providing a diversity of transmit signals. Maximum diversity gain is achieved when fading is un-correlated across antenna pairs Resultant digital broadcast networks would have fewer transmitter sites and thus be more cost-effective and have less environmental impact. Unfortunately more recent space-time-code is not compliant with current standards for broadcast systems and therefore only spatial diversity techniques can be applied. If multiple signals are received with short delay spread the OFDM signal is faded equally across the channel in a flat fade, this induces long error bursts that are hard to correct since there is insufficient frequency selectivity to be exploited by the coding and interleaving schemes. Cyclic Delay Diversity (CDD) is a very simple and elegant method which, when combined with MIMO, improves frequency selectivity thereby randomizing the channel response. The computational cost of CDD is very low, as the entire signal processing needed is performed on the OFDM signals in the time domain. CDD scheme is much simpler to implement and can be used for any number of transmit antennas. It conforms to current broadcast standards. This article focuses on the CDD diversity structure on DVB-H systems over different environments. Firstly, we introduce the system model and then discuss CDD for both transmitter and Maximum Ratio Combining (MRC) for receiver. The application of CDD to DVB-H systems over outdoor and indoor environments is discussed and results of simulations presented. Finally we present the conclusions of this study. The work in this paper was supported by the EU project PLUTO (Physical Layer DVB Transmission Optimization). Keywords DVB-T/H, OFDM, MIMO, Diversity, MRC, CDD INTRODUCTION Future mobile radio systems are expected to deliver services, which inherently require high data rates. Orthogonal Frequency Division Multiplexing (OFDM) [1] is an ideal technique for broadband transmission in multipath fading environments and is implemented in broadcast standards like DAB or DVB as well as WLAN standards [2] such as HIPERLAN/2 or IEEE 802.11a/g and WiMAX. Spatial diversity can be used to improve the error performance and channel capacity in these systems by overcoming degradations caused by scattering environments. The use of multiple transmit and receive antennas (multiple-input-multiple-out; MIMO) is a well- documented technique where each pair of transmit and receive antennas provides a different signal path from the transmitter to the receiver. By sending signals that carry the same information through these different paths, multiple independently faded replicas of the data symbol can be obtained at the receive end. Maximum diversity gain is achieved when fading is un-correlated across antenna pairs. More recent