2. Introduction to Wireless Systems

 

2. Introduction to Wireless Systems



17.12.2018

Introduction to Wireless Systems – Video: Register for Course


Introduction to Wireless Systems – Transcript:

What Will You Learn

Fixed Wireless Network

The high level structure of the fixed wireless network consists of:

  • end devices, aka STAs (stations) in the WiFi nomenclature;
  • Wireless access points – the WiFi Aps
  • The radio path – also called radio interface, through which, the radio transmission is conveyed
  • If this is an enterprise network, also we have a Wireless controller, that manages the configuration of the individual Aps
  • An internet Edge router to provide transport to public IP cloud called the internet
  • This enables to reach to the application servers and finally applications.

Fixed Wireless Network Evolution

An evolution of the fixed wireless systems, based on WiFi consisted on the following major steps:

  • The first commercial standard was 802.11b supporting up to 11Mbps of throughput. It was based on DSSS scheme (described in more details later on this course) working at 2.4GHz and the assumed range for communication of 35m indor and up to 140m outdoors
  • The next step was 2003, with 802.11g, where OFDM was used (also described in details later on in this course) supporting throughput of up to 54Mbps. As it is deployed at 2.4GHz, the range stayed similiar.
  • 6 years later the next generation came with 802.11n which, by using larger BWs at 5GHz and MIMO schemes, improved the throughput by over 10x ending up in maximum data transmission speed of 600Mbps. Due to using multiple antennas, also the range could be improved.
  • The next big step was with the introduction of 802.11 ac that further increased thrpt another 10x ending up at almost 7Gbps and new services/use cases. This standard is being deployed in 5GHz spectrum band and more antennas can be supported
  • The most recent standard is 802.11ad to be soon finalized. This one uses very high frequencies – namely, 60GHz band, and due to that, the range is highly limited – to 3.5m due to high pathloss and low penetration.

We will elaborate on the detailed aspect of those standards in the other section of this track.

Mobile Wireless Networks

Mobile wireless networks also known as 2G, 3G, 4G and recently also 5G, consist of the following main elements:

  • End user devices, that are called MTs (mobile terminals) in 2G, UEs (user equipments) in 3G, 4G and 5G
  • Radio access network – consisting of base stations and controllers (called BTS, BSCs, NBs, RNCs, eNBs and gNBs – depending on the technology)
  • Radio interface through which the radio signals are reaching the terminals and base stations
  • The private operators IP cloud being transporting the data to the operator’s brain – core network, where all the functionalities, including routing, charging, accounting, control, mgmt and user DBs are
  • To reach finally the public internet and application servers

Mobile Wireless Network Evolution

In case of mobile cellular wireless networks, we had so far 5 generations, that evolved as follows:

  • The first generation was supporting basic analogue voice with no data transmission support and was showing up the world in the 80’s. In this case there was one network designed for one service – voice. And different regions of the world had different standards including NMT in europe, AMPS in US and TACS in the far east
  • The next generation 10years later, namely 2G, brought digital voice…..

Licensed and Unlincensed Systems

One of the major differences between the mobile wireless systems vs fixed is the way they access spectrum – i.e. either through licensing or as free use. This table shows the differences and main characteristics of both.

Fixed and Mobile Network Convergence

Both words merge more and more in case of carrier wifi as the MNOs want to reach to unlicensed „free” spectrum where most of the traffic recently goes.

  • This started with wifi offload schemes, where the MNO could (through core network functionality) suggest the UE about neighbouring wifi (typically carrier wifi), so that the user decides to switch to the wifi link. This is done via CN, so the operator „looses” the control in some sense, the link is either via mobile network or via wifi
  • Then a bit more tight interworking came into play. In this case, the RAN (base stations) informs the terminal (based on radio measurements) about the wifi, and allows for faster switch to the wifi. The switch of the user data and control plane is switched fully to wifi – i.e. ue is either connected to mobile network or to carrier wifi
  • Most recently more advanced schemes came into play, namely the aggregation of resources / radio links between those networks. The first scheme is when the user is informed about the wifi network nearby, and is configured by LTE / mobile network to perform standardized measurements and to provide the results to the mobile network controlling the connection. And based of the decision, the traffic may be switched to WiFi, or added as a secondary link where the control is still kept at the mobile network, and the data can come trhough either mobile network or through wifi or through both. Addtionaly very recently the mobile industry has standardized its own radio enabled to be used in unlicensed spectrum – called LAA (licensed assisted access). This is an LTE radio tailored to be used in WiFi bands, which should fulfill requirements of being a good neighbor – i.e. should not impact wifi networks more than yet another wifi network.

 

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