Progress in Wireless Communication Systems

Introduction

The wireless communication systems have been tremendously evolved during the last few decades. Each time the systems nature was developed to improve its reliability, data rate, latency, speed etc. These evolutions were termed as mobile generations. An analog system called 1G was the first generation developed in 1981. This system based on a technology called
advanced mobile phone service, and was purely focussed on telephone calls. 1G is the first most cellular mobile technology. Due to some drawbacks in 1G such as non-reliable handoff, non-roaming capability and poor vice links, new mobile generations appeared approximately every ten years. The mobile users also increased at a rapid speed as the wireless systems
became more robust and reliable. With the passing of time a number of modifications keep on taking place and the wireless communication system has been evolved from the analog system (1G), duplex communication voice telephony (2G), multimedia communication systems (3G), Broadband IP network systems (4G), to a high data rate end to end connectivity (5G). Sufficient changes at the architecture level has been performed according to the needs, from the first generation until the fifth generation (5G) wireless networks. The 5G technology is on its way to create a universally connected world, with a broadband wireless communication and entertainment at a highly reliable wireless link.

Second Generation (2G)

The 2nd generation (2G) was also aimed primarily towards voice market, but it used digital modulation for the first time unlike the first generation. This generation provides significant improvements in voice quality, due to the use of efficient frequency allocation schemes such as Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). 2G offers performance improvements compared to 1G such as better data services, advanced roaming and higher spectrum efficiency. The virtual eminent technologies used in 2G were Global system for mobile communication (GSM) and Code Division Multiple Access (CDMA). 2G system architecture was further improved for circuit switched and packet switched domains called 2.5G, to provide a data rate of upto 144kbps. The General Packet Radio Service (GPRS) was used by 2.5G for data communication in addition to the GSM.


Figure 1. 2G system architecture (source: https://www.geeksforgeeks.org)

Third Generation (3G)

Third generation (3G) is based on International Telecommunication Union (ITU) family of standards. The first commercial 3G system was launched by NTT Docomo in japan in 2001. 3G system has the ability to transfer both the voice and non-voice data such as mobile TV, video calls, browsing internet data and location-based services. The main focus of 3G architecture was to offer increased data rate for both short and long coverage areas. The 3G  technology has been split into three main areas, the universal mobile telecommunication (UMTS), CDMA2000 (code division multiple access) and less well-known standard TD-SDMA. 3G offers more security by using the advanced user authentication capabilities. 3G technologies also provide much better global roaming calls clarity and multiplayer gaming capability which is not possible in 2G network systems. 3G was upgraded to another
telecommunication standard called 3.5G based on High Speed Downlink Packet Access (HSDPA), for high speed data packet internet communications. The modified 3G architecture supports a data rate of up to 2.4 Mbps on the forward link and up to 153 Kbps in the in the reverse link.


Figure 2. 3G system architecture
(source: https://www.slideshare.net/mashiur028/3g-system)

Fourth Generation (4G)

Fourth generation system (4G) was developed to remove the problems and limitations of the 3G systems. 4G provides high speed data transfer along with the concept of interoperability between different types of networks. This technology allows users to simultaneously connect to various wireless access technologies such as UMTS, WiMAX, WIFI or any other technology. 4G is an IP based system architecture with different communication standards like Long Term Evolution (LTE) and IEEE802.16 standards. 4G systems offer more reliable connection, faster hand off between different technologies and much higher data rates than the previous generations. The main features of the 4G technologies is the adaptability and being highly dynamic. Services can be delivered and will be available according to personal preferences of the users. In 4G the core network was completely replaced by the single IP network for both voice and video data. The more redundant signaling system 7 was replaced by the IP network that is connection less and use the slots only when they have data to send. 4G technology supports a mobile speed of up to 100 Mbps and a fixed speed of up to 1 Gbps. 4G was launched successfully for the first time in Japan in 2005. The LTE standard of 4G was published by 3GPP that offers a broadband and high-speed access of upto 100 Mbps. WiMAX as another standard of 4G provides faster data services of upto 40 Mbps, but it has some limitations such as poor voice services and limited roaming  capability.


Figure 3. 4G system architecture
(source: https://www.omnitron-systems.com/mobile-backhaul)

Fifth Generation (5G)

The usage of wireless communication technologies nowadays is not restricted only to voice and texting, it serves a number of diverse applications such as a demand for high speed networks due to the increased number of users. The 5G is another step towards the evolution of modern communication technologies, it is sometimes called the real wireless world network. 5G uses a frequency band of 30 GHz to 300 GHz, also called millimeter waves. The third generation partnership project (3GPP) standardized the first specification for 5G in the late 2017 and the
rules for standard body has been completed in June 2018. The fifth generation (5G) will be deployed with the existing 4G network and will fully compatible. 5G is a technology that allows the internet of things (IOT) to exist and will provide connectivity to every single device. The biggest focus of this technology is to provide access to the broadband technologies such as streaming services or cloud-based applications. The fifth generation system will provide a consistent reduction of latency to offer a much higher data rates. The 60 GHz band used by the 5G is an unlicensed band that ensures a high data rate. This generation offers a broad bandwidth access in terms of connectivity and coverage also provides features like virtual
reality.
The 5G network architecture aims to be more flexible and efficient to meet the diversified requirements of the modern mobile services. By the use of software defined networking (SDN) 5G completely cloudifies access, transport and the core networks. The transport network consists of SDN controllers that generates a specific data path based on network topology. The core network used in 5G only support non-3GPP networks deployed outside the NG-RAN. 5G network uses a more powerful concept of the network slicing unlike the other previous generations. These slices refer to the 3GPP functionalities that provides services to the user equipment (UEs). 5G system uses an efficient user plan path management to serve a big amount of data traffic.


Figure 4. Cloud based 5G system architecture (source: www.semanticscholar.org/paper)

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