Smart introduction of 5G Broadcast in co-existence with legacy broadcast systems

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ABSTRACT

5G Broadcast offers broadcast network operators the possibility of reaching mobile devices directly, without requiring additional hardware in smartphones [1]. 5G Broadcast enables delivery of services such as linear TV, live content offload, or emergency messages to the general population while minimizing the hardware impact and the cost to the end customers.

When introducing a new broadcast standard, factors such as spectrum scarcity, the need to support legacy receivers, and regulatory constraints are of significant interest in non-greenfield markets. Due to these issues, in some cases it may not be desirable or feasible to vacate one entire broadcast UHF channel to deploy 5G Broadcast. Instead, a transition approach to refarming may be preferred, where the available bandwidth is flexibly allocated to 5G Broadcast or a legacy standard with a granularity finer than a broadcast UHF channel.

In this paper, we analyze how 5G Broadcast can be introduced and deployed while coexisting in the same UHF channel with several other legacy broadcast radio technologies, including ATSC 3.0, DVB-T2 and ISDB-T. Transmissions belonging to both technologies, i.e. the legacy system and 5G Broadcast, are multiplexed (in time and/or frequency, depending on the legacy system) in a manner that is backwards-compatible with legacy demodulators. By proper joint signal generation, decoding the legacy signal can be achieved by legacy receivers, unaware of the presence of the 5G Broadcast waveform, while the 5G Broadcast waveform can be decoded by the corresponding receivers, unaware of the legacy system as well. We present the techniques used by both 5G Broadcast and legacy standards to create “gaps” in their transmissions and investigate how these techniques can be paired across standards to successfully achieve coexistence.

INTRODUCTION

In recent years, 5G Broadcast [1] has attracted the attention of broadcasters worldwide due to the possibility of reaching mobile receivers directly, while reusing the baseband processing present in current handsets. Although the baseline deployment model for 5G broadcast would be to dedicate one or several UHF channels in their entirety to this technology, in some cases it may be beneficial or desirable to partially allocate one channel to 5G Broadcast while using the remaining capacity for a legacy broadcast system.

In the US, the regulation requires a NextGen TV broadcaster to transmit a free-to-air ATSC 3.0 TV program, while the remaining capacity in the channel can be used for ancillary services (which may include a 5G Broadcast transmission). In this case, the ATSC 3.0 signal would need to share the 6MHz channel with the 5G Broadcast transmission, and the joint signal should be constructed in such manner that existing ATSC 3.0 receivers can demodulate their corresponding program.

In other geographies, although not necessarily bound by regulation, there may be deployment constraints under which it is beneficial to share a broadcast channel between 5G Broadcast and legacy technologies. For instance, a broadcaster may choose to move one TV program from DVB-T2 to 5G Broadcast while keeping the rest of the programs in the same channel under DVB-T2. This would allow legacy receivers to keep demodulating the DVB-T2 programs while enabling new device types through 5G Broadcast. Other use cases for 5G Broadcast, such as emergency notifications, software updates, datacasting, etc. may not need to use a whole channel.

An additional issue arising from different broadcasting technologies co-existing in the same channel is how to tackle the different link budgets (i.e. the transmit power) required to obtain the desired coverage. In practice, it may be desirable that co-existing standards use the same transmit power (e.g., if the same tower(s) is/are used for transmission), with the understanding that a certain amount of gap fillers may be needed to obtain full coverage. In co-existence based on frequency division multiplexing (FDM), such as 5G Broadcast with ISDB-T (as described in this paper), interference mitigation across technologies may necessitate careful choices of transmit power(s). However, for time division multiplexing (TDM) based co-existence, such as for 5G Broadcast with ATSC 3.0 or DVB-T2 (as described in this paper), interference due to different transmit power(s) is less of an issue.

For 5G Broadcast, the challenges related to uplink/downlink interference are addressed by 3GPP specifications, such that cellular transmissions from smartphones do not significantly impair broadcast reception.

In the standardization groups, there is currently a work item in progress in ATSC to address the corresponding co-existence aspects we describe in the next sections, while there is currently a proposed work item for Release 19 in 3GPP to tackle CAS enhancements in 5G Broadcast. In the case of DVB-T2, it was not deemed necessary to address any issues.

In this paper, we present techniques that can be used to multiplex 5G Broadcast with other broadcast technologies (ATSC 3.0, DVB-T2 and ISDB-T) in the same broadcast channel.For each of the technologies, we present the basic frame structure and features that can be used for coexistence.