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10 - Relaying and wireless network coding
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- By Elisabeth De Carvalho, Aalborg University, Mats Bengtsson, KTH - Royal Institute of Technology, Florian Lenkeit, University of Bremen, Carsten Bockelmann, University of Bremen, Petar Popovski, Aalborg University
- Edited by Afif Osseiran, Jose F. Monserrat, Patrick Marsch
- Foreword by Mischa Dohler, King's College London, Takehiro Nakamura
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- Book:
- 5G Mobile and Wireless Communications Technology
- Published online:
- 05 June 2016
- Print publication:
- 02 June 2016, pp 277-302
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- Chapter
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Summary
Relaying and network coding are powerful techniques that improve the performance of a cellular network, for example by extending the network coverage, by increasing the system capacity or by enhancing the wireless link reliability. This chapter focuses on relaying and wireless network coding in 5G. After reviewing the history of relaying, the key envisioned scenarios for relaying in 5G are highlighted, namely the provisioning of wireless backhaul in Ultra-Dense Networks (UDNs), for nomadic cells or for data aggregation in the context of massive machine-type communications. While full-duplex technology is slowly gaining maturity, it is expected that due to complexity reasons most relaying scenarios in 5G will be based on half-duplex devices. Therefore, finding solutions to overcome the half-duplex limitation remains critical. The chapter describes the following three key innovations for efficient half-duplex relaying:
• By applying the principles of wireless network coding to distributed multi-way traffic, in-band relaying becomes a spectrally efficient solution for wireless backhaul in ultra-dense networks of small cells, despite conventional views.
• Non-orthogonal multiple access techniques, as required by physical-layer network coding, are essential for increased spectral efficiency when simultaneous multi-flows are exchanged through a same relay. Here, Interleave-Division Multiple-Access (IDMA) is put forward for its ability to support flexible rate requirements.
• Buffer-aided relaying is featured where different ways to exploit buffering are described for improved diversity and increased rates. This technique targets delay tolerant applications having high data rate requirements.
The role of relaying and network coding in 5G wireless networks
Relaying was a common technique used to convey messages over large distances in ancient empires such as Egypt, Babylon, China, Greece, Persia and Rome [1]. The messages were transmitted in various forms, such as beacon fires relayed by towers or mountain peaks. A more common method was sending messengers on horseback between Relay Stations (RSs) until the final destination was reached. With the advent of science, communication techniques improved. In 1793, the Chappe brothers of France proposed a telegraph system relying on RSs equipped with telescopes and lighted by lamps.
In modern times, RSs were initially simple devices that amplify a signal and forward it immediately, and were mainly intended to extend the coverage of the wireless system. These were low-cost devices, compared to Base Stations (BSs), that did not include any baseband processing, and hence no network protocol operation was possible.
7 - The 5G radio-access technologies
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- By Malte Schellmann, Huawei, Petra Weitkemper, NTT DOCOMO, Eeva Lähetkangas, Nokia, Erik Ström, Chalmers University of Technology, Carsten Bockelmann, University of Bremen, Slimane Ben Slimane, KTH - Royal Institute of Technology
- Edited by Afif Osseiran, Jose F. Monserrat, Patrick Marsch
- Foreword by Mischa Dohler, King's College London, Takehiro Nakamura
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- Book:
- 5G Mobile and Wireless Communications Technology
- Published online:
- 05 June 2016
- Print publication:
- 02 June 2016, pp 158-207
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- Chapter
- Export citation
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Summary
The radio access for 5G will have to respond to a number of diverse requirements raised by a large variety of different new services, such as those from the context of massive Machine-Type Communication (mMTC) and ultra-reliable MTC (uMTC), as discussed in Chapter 2. Consequently, a “one-size-fits-all” solution for the air interface as prevalent in today's radio systems may no longer be the adequate choice in the future, as it can merely provide an inadequate compromise. Instead, the system should provide more flexibility and scalability to enable tailoring the system configurations to the service types and their demands. Moreover, as the data rates to be provided by mobile radio systems are ever increasing, technologies need to be devised to squeeze out the last bit from the scarce spectrum resources. This chapter elaborates on novel radio-access technologies addressing the aforementioned issues, which can be considered promising candidates for the 5G system. It is noteworthy that there has been flourishing work on potential radio-access technologies for 5G in recent time; refer to [1][2] for prominent research activities in the field.
The chapter starts with a general introduction to the access design principles for multi-user communications in Section 7.1, which build the fundamentals for the novel access technologies presented in this chapter. Section 7.2 then presents novel multi-carrier waveforms based on filtering, which offer additional degrees of freedom in the system design to enable flexible system configurations. Novel non-orthogonal multiple-access schemes yielding an increased spectral efficiency are presented in Section 7.3. The following three sections then elaborate on radio access technologies and scalable solutions tailored for specific use cases, which are considered key drivers for 5G radio systems. Section 7.4 focuses on Ultra-Dense Networks (UDN), where also higher frequencies beyond 6 GHz are expected to be used. Section 7.5 presents an ad-hoc radio-access solution for the Vehicle-to-Anything (V2X) context, and finally Section 7.6 proposes schemes for the massive access of Machine-Type Communication (MTC) devices, characterized by a low amount of overhead and thus enabling an energy efficient transmission.
Table 7.1 gives a brief overview on the radio-access technologies presented in this chapter, highlighting some of their characteristics and properties. It should be noted that the gathered information is not exhaustive and only the most important aspects are listed.