Mobile zeroes in on 5G
IMT-2020 also takes into account technological developments already in the pipeline that will play a role in the evolution of 5G.
On the RAN side, the most well-publicized developments are centered around carrier aggregation, advanced antenna technologies like 3D-beamforming, active antenna systems, massive MIMO and network MIMO that promise better spectrum efficiency. Particularly in Asia, there’s also been a lot of work on dual-mode TDD-FDD and dynamic TDD to enhance spectrum flexibility.
There’s also a lot of activity to develop advanced waveforms, modulation and coding, and multiple access technologies aimed at improving spectral efficiency, such as filtered OFDM (FOFDM), filter bank multi-carrier modulation (FBMC), pattern division multiple access (PDMA), sparse code multiple access (SCMA), interleave division multiple access (IDMA) and low density spreading (LDS).
Other RAN technology developments includes simultaneous Tx/Rx on the same frequency with self-interference cancellation, flexible backhaul and dynamic radio access configurations, higher-order modulation for small cells, joint management of multiple radio access technologies (multi-RATs) and flexible uplink/downlink resource allocation.
On the network side, SDN and NFV are already in play, and are expected to play a key role in enabling operational network efficiency and give mobile networks the flexibility and visibility they need to support the deluge of apps, services and connections coming down the road.
Cloud RAN (C-RAN) will play a major role in ensuring that baseband and higher-layer processing resources can be managed and allocated dynamically on demand. Inter-cell coordination schemes like self-organizing network (SON) technology will enable operators to improve the opex efficiency of multi-RAT and multi-layer networks.
Then there are technologies designed to enhance mobile broadband service QoS, such as small cells, License Assisted Access (LAA), Evolved Multimedia Broadcast and Multicast Service (eMBMS), dynamic adaptive streaming over HTTP (DASH) to accommodate more video streaming content in existing infrastructure, context aware applications for more personalized services, and proximity-based techniques to enable direct device-to-device (D2D) communication.
This is 5G
With all that in mind - and with the key caveat that 5G has to be conceptualized and designed not only for the applications and services the industry knows are coming, but for the apps and services we haven’t even thought of - the ITU has developed a list of eight key parameters that should define 5G’s capabilities:
- Peak data rate: maximum achievable data rate (Gbps) under ideal conditions per user/device.
- User experienced data rate: achievable data rate (Mbps or Gbps) that is available ubiquitously across the coverage area to a mobile user/device. (Note that “ubiquitous” refers to the target coverage area, not literally everywhere in the country.)
- Latency: the contribution by the radio network to the time from when the source sends a packet to when the destination receives it (in ms).
- Mobility: maximum speed (km/h) at which a defined QoS and seamless transfer between radio nodes which may belong to different layers and/or radio access technologies can be achieved.
- Connection density: total number of connected and/or accessible devices per unit area (per km2).
- Energy efficiency: on the network side, energy efficiency refers to the quantity of information bits transmitted to/ received from users, per unit of energy consumption of the RAN (in bit/Joule). On the device side, energy efficiency refers to quantity of information bits per unit of energy consumption of the communication module (in bit/Joule).
- Spectrum efficiency: average data throughput per unit of spectrum resource and per cell (bits per second/Hz).
- Area traffic capacity: total traffic throughput served per geographic area (in Mbps/m2).
When IMT-2020 was first announced, many media reports focused primarily on the first parameter - peak data rate - if only because that’s the one consumers relate to the most. After all, faster data rates from the previous generation were the primary marketing focus of 3G and 4G services. Initial reports claimed that IMT-2020 would provide peak rates of 20 Gbps.
That’s true - in a sense. ITU-R M.2083-0 does assign actual values to each of the eight parameters, and it does say that 5G will support peak rates of up to 20 Gbps - under certain conditions and scenarios. Under other circumstances, peak data rates will be more along the lines of 10 Gbps, and that’s mainly for enhanced mobile broadband services (i.e. accessing the internet on your smart device like you do now, only with a faster and more efficient connection, and better latency, etc).
But data rates for 5G will vary depending on the scenario. The ITU document says: “IMT-2020 would support different user experienced data rates covering a variety of environments for enhanced Mobile Broadband. For wide area coverage cases, e.g. in urban and sub-urban areas, a user experienced data rate of 100 Mbit/s is expected to be enabled. In hotspot cases, the user experienced data rate is expected to reach higher values (e.g. 1 Gbit/s indoor).”
Which is another way of saying that with 5G, the exact peak rates won’t matter, so long as they deliver the best possible user experience for any given app or service.
The same goes for the other parameters. As Figure 1 (below) shows, the ITU has assigned benchmarks for each of them, but cautions: “The values are targets for research and investigation for IMT-2020 and may be further developed in other ITU-R Recommendations, and may be revised in the light of future studies.”
The ITU adds further that the benchmarks for peak data rates, mobility, spectrum efficiency and latency are basically extrapolations of its current benchmarks for IMT-Advanced (the ITU’s codename for LTE-Advanced and related technologies).
And as a further caveat, the ITU notes that the importance of each parameter is app-specific. For example, mobility isn’t that important in a hot-spot scenario, while a massive machine-type communication (MTC) scenario would place higher emphasis on connection density than fast data rates (depending on the app).
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