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The Next Big Thing: 5G network architecture and technology

September 01, 2015

The fifth generation of telecommunications systems, or 5G, is expected to be commercially launched worldwide by 2020. These networks are claimed to be 60-70 times faster than 4G networks with download speeds increasing from a 4G peak of 150 Mbps to a minimum of 10 Gbps. Most importantly, 5G will deliver extremely low latency of around 1 millisecond – unperceivable to a human and about 50 times faster than 4G. Latency refers to the time lag between an action and a response. The low latency offered by 5G is expected to push augmented reality and virtual real-ity into the mainstream. Therefore, going forward, 5G will pave the way for a converged networking environment where wired and wireless communications will use the same infrastructure. However, to deliver 5G, operators need to boost their network capacity significantly.

At present, operators and vendors worldwide are making huge investments in identifying the spectrum bands that could potentially be used to roll out 5G. Also, vendors are working to identify technical solutions that can help support 5G services which would require high bandwidth. According to a research paper titled “Understanding 5G: Perspectives on Future Technological Advancements in Mobile” by GSMA Intelligence, operators and vendors worldwide are exploring technical solutions for 5G that could use frequencies above 6 GHz and reportedly as high as 300 GHz. However, higher frequency bands offer smaller cell radiuses and therefore, achieving widespread coverage using a traditional network topology model would be challenging. To overcome this limitation, the industry is looking at “beam-forming” – the focusing of the radio interface into a beam that would be usable over greater distances. Beam-forming is expected to be a critical part of the radio interface in future networks. To deliver high speed 5G services, the beam will have to track each mobile device, which essentially means that each cell in a network may have to support several hundred individual beams at any given time and track the end-users that are connected through these beams in a three-dimensional space.

In addition to the beam-forming solution, vendors are looking at high-order multi-input, multi-output (MIMO) technology as an alternative method for increasing the bandwidth on networks and making them 5G-ready. MIMO allows for the installation of an array of antennas in a device, and multiple radio connections are established between a device and a cell. However, GSMA in its research paper underlines that high-order MIMO can lead to issues pertaining to radio interference; therefore, supportive technology is required to help mitigate this problem. In fact, research is in progress to arrive at an architecture where the radio network is capable of adjusting its beam to take into account the specific orientation of the antenna at any given time. Further, to enhance the capacity for 5G networks, operators will look at installing more base stations to ensure that connected devices have access to telecom towers in close proximity. At the same time, operators are expected to supplement long-range macrocells, which can reach up to about 20 miles, with a number of short-range small cells that can cover up to a few hundred feet. However, the installation of macrocells and microcells on each tower calls for huge investments. In such a scenario, massive MIMO is being considered as a key technology required for the evolution from 4G to 5G. A number of vendors are working towards developing MIMO solutions to support high bandwidth services on 5G networks. For instance, Huawei claims to have introduced the first 128TRX massive MIMO prototype for the telecom industry at the 2014 Global Mobile Broadband Forum held in Shanghai. By providing higher resolution in the angular domain, the 128TRX massive MIMO prototype supports 3D user location distribution, improving spectrum efficiency and enhancing network capacity. The vendor also demonstrated sparse code multiple access (SCMA) technology at the forum. Huawei claims that the live tests showed that SCMA can improve the number of connections by 300 per cent and decrease air interface latency by seven times.

5G network architecture and technologies

At the 2015 Mobile World Congress, the European Commission (EC) along with its industry partners announced the EU’s vision of 5G technologies and infrastructure. As per the EC, the key technological components of 5G networks will encompass optical, cellular and satellite solutions. 5G networks will rely heavily on emerging technologies such as software defined networking (SDN), network functions virtualisation (NFV), mobile edge computing and fog computing. A recent white paper by Ericsson, “5G systems – Enabling Industry and Society Transformation”, too identifies NFV and SDN technologies as playing a key role in making 5G networks a reality. The white paper by the vendor indicates that even as the telecom industry moves towards a new 5G radio access standard, 5G networks will be much more than just radio access. In fact, the 5G network of the future will be an integration of cross-domain networks. 5G systems will be built to enable logical network slices, which will allow operators to provide networks on an as-a-service basis. And, according to Ericsson, NFV and SDN are the two slices in the network.

Like Ericsson, telecom equipment vendor Qualcomm has also identified SDN and NFV technologies to be an integral part of 5G networks. In a white paper titled, “5G – Vision for the Next Generation of Connectivity”, the vendor has identified the key characteristics defining a 5G network. Some of these characteristics are mentioned below.

User-centric design

The design approach in 5G is user centric, as it looks to bring content, connectivity and computing closer to the user. For connectivity, users will be more than mere end-points; they will be an integral part of the network (offering edgeless connectiv-ity). This distributed approach combined with NFV will not only reduce latency, but also significantly improve cost and energy efficiency, which are the key objectives of any new-generation technology.

Scalability and adaptability

5G networks will have the ability to scale and adapt across an extreme variation of use cases, including ultra-reliable, mission-critical services such as controlling the power grid or remote medical procedures; and connecting everything from simple sensors to complex robots, which also means supporting billions of ultra-low energy devices at very low data rates and at ultra-low cost.

User-centric network: Distributed and virtualised

Network virtualisation goes hand in hand with the distributed architecture approach, where network functions are virtualised and closer to the network edge. The 5G network will leverage NFV and SDN technologies, which are expected to be introduced in a large number of 4G networks ahead of 5G. The processing ability could be dynamically balanced between centralised and distributed based on the context – placing the control closer to the user for low latency applications and relying on centralised processing for other applications.

A key example of the value of this flexibility is when a mobile-capable device is engaged in a stationary position. In such a situation, by leveraging the improved network awareness, the network understands the context and avoids the setting up of network resources for full mobility. At the same time, the network is ready to rapidly bring mobility functions whenever the need arises, setting up control and user plane resources closer to the user to reduce latency. Virtualisation enables more efficient scaling of the core network so that the nodes can scale based on data and signalling loads, and cater to various deployment models, from hotspots and residential type of deployments to local area and wide area networks.

Qualcomm states that, unlike 3G which was defined by code division multiple access and 4G which was defined by orthogonal frequency division multiple access (OFDMA), 5G will not be defined as one multiple access variant since it is envisioned to meet an extreme variation in services – to support all spectrum types and bands. However, the foundation of the unified air interface is envisaged to be based on OFDMA, providing support for feature-driven development and test-driven development to address issues related to paired and unpaired spectrum, and also for shared and multi-tiered spectrum approaches across licensed and unlicensed spectrum. For instance, unified air interface will be required to use the time and frequency domains, orthogonal and non-orthogonal domains, as well as synchronous and asynchronous domains to adapt and scale to different spectrum and services types.


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