Handover Algorithm for a Dedicated DVB-H Network
The handover for the dedicated DVB-H network in this book is defined as the handover which is considered in the DVB-H network only. For the converged DVB-H and telecommunications networks, the handover inside the DVB-H network part can also be considered
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The handover for the dedicated DVB-H network in this book is defined as the handover which is considered in the DVB-H network only. For the converged DVB-H and telecommunications networks, the handover inside the DVB-H network part can also be considered the handover of the dedicated DVBH network. Handover in unidirectional broadcasting networks like DVB-H is a novel issue. The main difference between handover in DVB-H and that of 3G telecommunications networks is that passive handover in DVB-H is performed and can be performed by the terminals only while the handover in 3G telecommunications networks will require the operation by both the network and the terminals. Since making accurate handover decisions can reduce the battery power consumed, this chapter describes and investigates different strategies that can assist the handover decision-making process in DVB-H networks. The benefits and drawbacks of the different algorithms are presented. A hybrid handover decision-making algorithm is also described.
6.1 Introduction Handover is the switching of a mobile signal from one channel or cell to another. When a user moves from one DVB-H cell to another, the DVB-H terminal has to be synchronized to another signal without service interruption. This chapter defines handover in DVB-H as a change of transport stream and/or frequency. Handover in dedicated DVB-H network refers to the handover in a DVB-H only network (without uplink connection). DVB-H transmits data streams using a burst mode called time slicing instead of a continuous mode. Time slicing is the characteristic that makes seamless soft handover in DVB-H possible. The off burst time in time slicing transmission mode is illustrated in Fig. 6.1. Depending on the transmission bit rate, the duration of the off time in the transmission stream can vary. The DVB-H receiver can utilize the off time to detect the signals and to initialize soft handover when it moves from one
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6 Handover Algorithm for a Dedicated DVB-H Network
Fig. 6.1. Off Burst Time in Time Slicing Mode
DVB-H cell to another. This chapter focuses on the most important of the three handover stages - the handover decision-making process. An instantaneous RSSI (Received Signal Strength Indication) value based handover scheme was proposed in [104]. This is the earliest publicly available handover algorithm for DVB-H. Since the RSSI value can vary due to multipath, interference or other environmental effects it may not give a true indication of communication performance or range and mistakenly measuring the RSSI value would result in unnecessarily consuming battery power because of more off burst time used in handover measurement. Therefore, the RSSI value may have the chance of being measured during many off burst times and the possibility is that the RSSI value would be measured at least every off burst time. Approaches to improve the RSSI handover algorithm are proposed in this chapter. In the analysis to the potential battery power consumption savings of the algorithms proposed in this chapter a worst case s
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