Figure 3-7 summarizes the vision of 5G networks, showing its key differences from 4G and where the two cellular standards will intersect. In summary, 5G networks will do the following:
• Deploy a multitude of heterogeneous RATs where mobile devices may operate multiple links to distinct RATs simultaneously
• Deploy a multitude of different cell types, including dynamic cell structuring mechanisms
• Combine classical wireless broadband bands, typically below 6 GHz, with mmWave bands
• support the application of wireless backhauling, in particular for small cells
• Deploy several base stations to serve a target mobile device simultaneously
• Enable device-to-device and multi-hop communication
• Enable usage of an efficient User/Control plane split across multiple BS and/or multiple RATs
51 The 4G air interface is based on OFDM waveforms, which provide system bandwidth scalability, multi-user resource allocation in time and frequency, with a granularity of physical resource blocks (PRB = 1 ms × 180 kHz), and spatial MIMO processing at moderate signal processing complexity. The OFDM waveform is well suited for the 4G broadband access scenario, in which base stations are synchronized in time and frequency, and users are predominately served by one base station at a time. Uplink synchronization is realized by timing advance mechanisms controlled by the serving base station. Furthermore, macro and small cells are usually allocated a dedicated and contiguous part of the spectrum. However, with heterogeneous network deployments, where different cell sizes are combined, more spectrum allocation flexibility will be required. Therefore, new PHY and MAC functionalities to support asynchronous multi-connectivity, autonomous in-cluster self-organization of radio resources, spectrum coordination with other wireless communication clusters, and support for high mobility—possibly without wireless infrastructure support—will be required for 5G.
5G will support multiple point access to various base stations. This will make timing advances infeasible unless the involved base stations are operated at separate frequencies/PRBs. Multi-access-interference (MAI) will become a significant challenge in network design with OFDM applied. MAI and asynchronous signals will become particularly severe in network-assisted or ad-hoc vehicle or vehicle-to-infrastructure wireless communication with several simultaneous links in a meshed topology.
Solutions being investigated and designed include new scalable waveforms to be configured in spectral localization, which need to be robust against timing jitter, and MAI, scalable in allocated system bandwidth per wireless link, access point, or wireless system and must support easy frequency domain equalization for frequency selective channels. Filter Bank Multicarrier (FBMC) is one promising candidate for a 5G physical layer (PHY). Nonorthogonal schemes for multi-user access (NOMA) are also under investigation; these consider channel overloading techniques for multi-user/multi-point communications, for example by a superposition of orthogonal waveforms
Figure 3-7. A 5G network and its key features [14]
(CDMA, OFDMA) or specific nonorthogonal CDMA designs. The resulting interference between users can be handled by more complex signal processing on the receiver side.
One of the key differences between 4G and 5G networks is the spectrum extension beyond 6 GHz, which will allow significantly more bandwidth per wireless link and per base station. Furthermore, the interference range will be smaller than experienced below 6 GHz because of the need for more directional transmission of energy. This is caused by the link budget and the limited available transmit power. This makes mmWave wireless access the ideal candidate for small-cell deployments. In mmWave small cells deployments, the number of active users should shrink proportionally to the coverage area. TDMA can therefore be a sufficient solution for multiuser access. Beamforming antennas are seen as mandatory to reach the high gain (directionality) for dynamic outdoor environments. Furthermore, transmit power at mmWave is usually limited.
Therefore, advanced multicarrier waveforms with low Peak-to-Average Power Ratio (PAPR) are crucial.
These technological directions are expected to be a key differentiator between the 4G and 5G cellular standards. 5G will introduce new transmitter and receiver designs, new modulation schemes and waveforms, new adaptive antenna array technologies for mmWave bands and new regulatory regulations on spectrum sharing, interference mitigation, and licensed and unlicensed operation.
References
1. Ericsson, “5G—What it is?” White Paper, October 2015;
2. http://www.streamingmediaglobal.com/Articles/News/Featured-News/
Ericsson-Plans-5G-Showcase-at-2018-Winter-Olympics-105898.aspx 3.
http://www.telegraph.co.uk/technology/news/10598874/South-Korea-to-invest-900m-in-5G-development.html
4. http://www.phonearena.com/news/Japans-NTT-DoCoMo-shares-its-plans-to-deliver-5G-in-time-for-the-Olympics-in-2020_id72473
5. 3GPP, SP-150149, “5G” timeline in 3GPP, http://www.3gpp.org/
news-events/3gpp-news/1674-timeline_5g
6. NGMN Alliance, “NGMN 5G White Paper", February 2015;
7. GSMA Intelligence, “Understanding 5G: Perspectives on future technological advancements in mobile", December 2014;
8. Huawei, “5G: A Technology Vision”, White Paper, November, 2013;
9. Ericsson, “5G - Requirements and capabilities”, White Paper 2015;
10. Samsung Electronics, “5G Vision”, White Paper, February 2015;
11. Nokia, “5G Use Cases and Requirements”, White Paper, 2014;
12. 4G Americas, “Recommendation on 5G Requirements and Solutions”, White Paper, October 2014;
13. 4G Americas, “Mobile Broadband Evolution towards 5G: Rel-12 & Rel-13 and beyond”, White Paper, June 2015;
14. Markus D. Mueck, Ingolf Karls et.all, “Global Standards enabling a 5th Generation Communications System Architecture Vision”, IEEE Globecom 2014, Workshop on Telecommunications Standards on Emerging Technologies for 5G Wireless Cellular Networks, Austin, Texas, USA;
15. 3GPP TR 38.900 “Study on channel model for frequency spectrum above 6 GHz” 2016
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© Intel Corp. 2016
5G Technologies
As discussed in the previous chapter, the wireless communication ecosystem stakeholders are currently in the process of trying to figure out what will be the key 5G use cases, enabling everything from autonomously driving cars to 8K video streaming to the billions of connections characteristic of the Internet of Things (IoT). Recently published white papers by key stakeholders have revealed some mutual shared views on 5G requirements and key features.
First there is wireless access speed, important for extreme mobile broadband access (xMBB) , where 5G will achieve peak data rates up to several times faster than LTE Advanced's peak speeds of 1 Gbps. In 5G laboratory trials peak speeds of 7.5 Gbps [ 1 ] or even 1 Tbps [ 2 ] have been achieved (a peak rate that shouldn't be expected in commercial networks). Second is capacity, which is important in particular for extreme machine-type communication (xMTC), where, for example, NGMN expects 5G to provide between 100 and 1,000 times more capacity than 4G [ 3 ] . These factors may seem excessive at a first glance, but current studies show that by 2019 alone the mobile capacity requirements will increase by a factor of 6-10 times compared to 2014 as shown in a recent overview published by GSMA [ 4 ] , illustrated in Figure 4-1 . Third, there is latency, important for extremely responsive and reliable machine-type communication. 5G must have a latency of a single millisecond, 50 times faster than 4G, or even less [ 1 ] . And finally, the network will run on either centimeter wave bands at spectrum frequencies below 6GHz or centimeter and millimeter wave bands above it. 5G networks shall consist of densely deployed indoor and outdoor small cells, new antenna designs including massive MIMO, combinations of multiple radio access technologies, including WiFi, and evolution of software defined networking (SDN) and network function virtualization (NFV) for better resource and energy efficiency.