Packet-Level Diversity Reception in Cell Border Regions with DVB-H

Abstract

Digital broadcast systems such as Digital Video Broadcasting - Handheld (DVB-H) support Single Frequency Networks (SFNs). Within these SFNs, all transmitters broadcast the same signal on the same frequency and therefore represent a single big network 'cell'. However, even SFNs have borders, and some DVB-H networks are built in a cellular scheme where one cell is covered by a single transmitter. In the border region between two of these cells, signal quality available from either of the cells is usually poor. This paper presents an approach to realize diversity reception of the signals of two or more different adjacent network cells in such a border region. By this means, the packet error rates of services available in several cells may be reduced significantly by replacing lost packets from an alternative signal. It is shown in this paper how such an approach may be implemented with the DVB-H standard by making use of a single receiver front-end only. With this technique, also soft handovers on packet level become possible. transmitters. However, even SFNs have borders. Firstly, the extent of SFNs is limited by the so-called guard interval which is used for the OFDM modulation and is a substantial part of the SFN support of such networks. Secondly, due to regulatory reasons the same frequency typically is not available in every region of a service target area. Because of that, 'network cells' are built making use of different transmission frequencies in different regions. Within these cells, either an SFN or a single transmitter may be used. At the border of neighboring cells reception of the signals of all adjacent cells tends to be poor and error-prone. Due to the usually existing overlap of the coverage area of various cells it is often possible to receive several error-prone signals from different cells. If a terminal is located in such an area, it could receive a service from more than one cell and merge the different signals to a combined signal of improved quality. For this approach to work a terminal would normally need at least two receiver modules. In this paper, however, an approach will be presented where only a single receiver front-end is sufficient for such a diversity reception. The idea is based on the Time Slicing technology which was originally introduced in DVB-H for reducing power consumption of the terminal. The paper starts with a short overview over DVB-H. Specifically Time Slicing and Phase Shifting are discussed. Afterwards, the new approach for diversity reception on packet level is presented in detail. Requirements for terminals to realize this kind of reception are shown. The approach is evaluated by the use of simulations. Finally, the paper closes with a short conclusion. II. DVB-H