Historical Trend of Wireless Communications

A new generation of cellular system appears every 10 years or so, with the latest generation (4G) being introduced in 2011. Following this trend, the 5G cellular system is expected to be standardised and deployed by the early 2020s. The standardisation of the new air interfaces for 5G is expected to gain momentum after the International Telecommunication Union‐ Radiocommunication Sector’s (ITU‐R) meeting at the next World Radiocommunication Conference (WRC), to be held in 2015. Table 1.2 summarises the rollout year as well as the International Mobile Telecommunications (IMT) requirements for the peak and the average data rates for different generations of the cellular system. Although IMT requirements for 5G are yet to be defined, the common consensus from academic researchers and industry is that in principle it should deliver a fibre‐like mobile Internet experience with peak rates of up to 10 Gbps in static/low mobility conditions, and 1 Gbps blanket coverage for highly mobile/cell edge users (with speeds of > 300 km/h). The round‐trip time latency of the state‐of‐the‐art 4G system (Long‐Term Evolution – Advanced; LTE‐A) is around 20 ms, which is expected to diminish to less than 1 ms for 5G.

Global standards are a fundamental cornerstone in reaching ubiquitous connectivity, ensur- ing worldwide interoperability, enabling multi‐vendor harmonisation and economies of scale. ITU‐R is responsible for defining IMT specifications for next‐generation cellular systems. Having defined two previous specifications (IMT‐2000 for 3G and IMT‐Advanced for 4G), it has already commenced activities towards defining specifications for 5G, which is aimed for completion around 2015. ITU‐R arranges WRCs every three to four years to review and revise radio regulations. Allocation of new spectrum for mobile communications is already on the agenda of the next WRC, to be held in November 2015.

To understand where we want to be in terms of 5G, it is worthwhile to appreciate where it all started and to mark where we are now. The following provides a roadmap of the evolution towards 5G communications:

  • Before 1G (<1983): All the wireless communications were voice‐centric and used analogue systems with single‐side‐band (SSB) modulation.
  • 1G (1983–): All the wireless communications were voice‐centric. In 1966, Bell Labs had made a decision to adopt analogue systems for a high‐capacity mobile system, because at that time the digital radio systems were very expensive to manufacture. An analogue system with FM radios was chosen. In 1983, the US cellular system was named AMPS (Advanced Mobile Phone Service). AMPS was called 1G at the time.
  • 2G (1990–): During this period, all the wireless communications were voice‐centric. European GSM and North America IS‐54 were digital systems using TDMA multiplexing. Since AT&T was divested in 1980, no research institute like Bell Labs could develop an outstanding 2G system as it did for the 1G system in North America. IS‐54 was not a desir- able system and was abandoned. Then, GSM was named 2G at the time when 3G was defined by ITU in 1997. Thus, we could say that moving from 1G to 2G means migrating from the analogue system to the digital system.
  • 2.5G (1995–): All the wireless communications are mainly for high‐capacity voice with limited data service. The CDMA (code division multiple access) system using 1.25 MHz bandwidth was adopted in the United States. At the same time, European countries enhanced GSM to GPRS and EDGE systems.
  • 3G (1999–): In this generation, the wireless communications platform has voice and data capability. 3G is the first international standard system released from ITU, in contrast to previous generation systems. 3G exploits WCDMA (Wideband Code Division Multiple Access) technology using 5 MHz bandwidth. It operates in both frequency division duplex (FDD) and time division duplex (TDD) modes. Thus, we could say that by migrating from 2G to 3G systems we have evolved from voice‐centric systems to data‐centric systems.
  • 4G (2013–): 4G is a high‐speed data rate plus voice system. There are two 4G systems. The United States has developed the WiMAX (Worldwide Interoperability for Microwave Access) system using orthogonal frequency‐division multiplexing (OFDM), evolving from WiFi. The other is the LTE system that was developed after WiMAX. The technology of LTE and that of WiMAX are very similar. The bandwidth of both systems is 20 MHz. The major cellular operators are favourable to LTE, and most countries around the world have already started issuing licences for 4G using current developed LTE systems. The cost of licensing through auction is very high. Thus, we could say that migrating from 3G to 4G means a shift from low data rates for Internet to high‐speed data rates for mobile video.

5G (2021–): 5G is still to be defined officially by standardisation bodies. It will be a system of super high‐capacity and ultra‐high‐speed data with new design requirements tailored towards energy elicited systems and reduced operational expenditure for operators. In this context, 5G envisages not only one invented technology, but a technology ecosystem of wireless networks working in synergy to provide a seamless communication medium to the end user. Thus, we can say that moving from 4G to 5G means a shift in design paradigm from a single‐discipline system to a multi‐discipline system.

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