Wireless Communication allows the transfer of information between a transmitter and a receiver, without a physical medium.
Components of Wireless Communication
Transmitter
Receiver
Wireless Signal
Wireless Channel
The communication link uses RF signals (radio frequency signals)to transfer information.
All radio signals travel at the speed of light.
RF signals used as a vehicle for information transfer are often referred to as carrier waves.
Modulation is the process by which we impress information onto the carrier wave for transmission.
At the receiver, we must demodulate the carrier to recover our data.
Wireless Transmission and Reception
This is a high-level representation of the process. In reality, there are much more processes involved.
Cell towers are deployed by the network operators to carry wireless transmissions in long distances.
During a phone call, our devices would send the signal to one of these towers, which then transmits our information to the receiver.
High frequency radio signals face higher pathloss during transmission.
When information is sent over any wireless communication link, Noise and possibly Interference is introduced.
Noise is unwanted energy or signals.
It is natural in nature i.e. it is always present in real-life scenarios and cannot be controlled.
Interference is created when two nearby transmitters use the same radio frequency at the same time.
It is deliberate in nature and it can be mitigated with careful planning of frequency allocation of various devices.
Radio Spectrum is the range of radio frequencies over which a wireless communication takes place for a specific purpose.
The frequencies or radio spectrum allocated to mobile phones ranges from approximately $450$ MHz to $39$ GHz.
A radio signal that carries information uses a range of frequencies over which the communication link is established. That range of frequencies is called a radio channel and its width is called bandwidth.
The radio channel is often compared to a data pipe: a wider channel implies bigger data pipe and higher data rate.
The radio channel can be loosely classified as:
Narrowband: Radio Signal occupies a smaller amount of radio spectrum (~ kHz).
Wideband: Radio signal occupies a larger amount of radio spectrum (~ MHz).
FDD and TDD are two ways to share the limited (and expensive) Radio Spectrum
Frequency Division Duplexing (FDD)
It requires a pair of radio channels for simultaneous two-way communication.
Both sides can transmit information at the same time on independent links.
Time Division Duplexing (TDD)
It uses a single radio channel but it is used in different directions at different times.
It is cheaper and more flexible than Frequency Division Duplexing, but at the expense of data speeds.
There are several factors that affect the data rate, i.e., the speed your phone gets:
Signal-to-Noise Ratio
How many bars does my phone have?
Channel Capacity
How wide is my channel?
Network Load
How crowded is my channel?
Spectral Efficiency
How frequently, and efficiently, can my phone use the available channel?
A mobile network’s coverage area is divided into “cells”.
Each cell is served by a Base Station a.k.a. a “tower”.
The cells are designed to have “tessellating” coverage.
As you drive around, you are handed off from one Base Station to the next by the network.
Let’s take a look at a high-level overview of a Cellular Network
A Cellular Network has two fundamental components:
Radio Access Network (RAN)
It provides wireless connections to users.
Base stations are interconnected.
Use communicates with one base station at any time.
Emphasis on higher speeds and spectral efficiency.
Massive Machine-Type Communications (m-MTC)
Connecting not just people, but their worlds.
Expectation of very long battery life (Up to 10 years).
Emphasis on power conservation and simplicity of protocols, instead of speed and efficiency.
Ultra Reliable Low Latency Communications (URLLC)
Ultra-responsive, instant connections necessary for mission-critical services.
Emphasis on end-to-end latency, instead of speed.
Ultra-high reliability and availability.
Support for high-speed mobility.
[i] Approximately every 10 years, a new generation of cellular technology has been developed, starting with 1G in the 1980s to the current fifth generation.
[i] 5G aims to meet new requirements by providing:
an increase in
Throughput
Spectral Efficiency
Capacity
Network Efficiency and Density
decrease in
End-to-End Latency
[i] eMBB, mMTC and URLLC are three prominent service classes 5G is expected to enable.
NSA acts as a stepping stone on road to end-to-end 5G network deployments.
Channel coding provides additional metadata to wireless signals to minimize the effects of pathloss, noise and interference.
Even if the wireless signal faces impediments, the receiver can make educated guesses to retrieve original data.
Without channel coding, the receiver cannot demodulate the information properly.
This causes the transmitter to resend the same message multiple times, therefore using more power and resources.
Advanced Channel coding in 5G NR allows for more efficient delivery of multi-Gbps throughput.
MIMO stands for Multiple Input Multiple Output.
If both the receiver and sender has multiple antennas, which they utilize for multiple inputs and outputs, it is called MIMO system. This massively improves the data throughput.
MIMO enables two signals to be sent on the exact same frequency channel.
It also helps improve Spectral Efficiency.
mmWave enables us to use the mostly unused mmWave spectrum which offers us with abundant bandwidth, solving the problem of frequency scarcity for wireless devices.
5G NR network architecture is guided by certain key principles: ^0342a0
Independence of software from hardware
Provides great flexibility and scalability.
Decoupling of compute and storage resources
Provides extra protection and protects data more efficiently.
Separation of user plane from control plane
Cloud-compatible design: flexible and easily scalable
The following features enable a 5G NR network to implement the principles mentioned above ^0342a0:
A Network Slice is a subset of the available network components that can provide an E2E service.
A Network Slice can be designed and commissioned depending upon the needs of a service.
Diverse requirements of different services can be met by serving them with different slices of the same network, i.e., different components of the same infrastructure.
Splitting resources to network slices enables the ability to serve different use cases on the same network. Network slicing allows allocation of resources to different service classes precisely according to requirements
Benefits
Dynamic and efficient resource allocation and utilization; resource isolation among services.
There are three principal ways of utilizing the available spectrum as far as 5G is concerned.
Licensed Spectrum
Whoever wants to use this 5G spectrum has to have a specific license of usage, obtained from a local regulatory authorities.
He has exclusive access to that band, resulting in better performance.
Downside is that the network operator has to pay a lot of money to secure the license.
This might result in higher fees for the users of the network.
Unlicensed Spectrum
It has been internationally agreed upon to be free for use for end consumers.
Examples include WIFI routers, Bluetooth, garage door openers etc.
User density might prove to be problematic for unlicensed spectrum.
Interference profile in unlicensed spectrum is usually very poor.
Shared Spectrum
A band is licensed from the regulatory authority but different companies make an agreement to share it among themselves.
For example, one company might agree to use the top half of the band while the other uses bottom, or one company might use the whole band in the morning, while the other uses the whole band in the evening.
It offers a good trade off between cost and performance.
What is mmWave?
Spectrum where radio wavelength is a few millimeters: above 24 GHz
5G mmWave spectrum is around 28 GHz and 39 GHz.
Spectrum above 52 GHz is also being considered.
Why mmWave?
Currently, mmWave is largely unused.
Ample spectrum available.
Enormous bandwidth
mmWave can fulfill the demand of data-hungry 5G use cases.
What are the challenges of mmWave?
Inferior propagation
Higher frequency results in significantly higher path loss.
Building penetration loss
Deep indoor coverage is challenging.
Sever attenuation due to rain and foliage
What are the advantages of mmWave?
Larger bandwidth → Less crowding
More antennas → Higher Gain
As the frequency of operation goes higher, the wireless antenna size gets smaller.
At mmWave, antennas size become very small.
Small mmWave antennas enable the possibility of designing antenna arrays.
As more antennas are capable of transmitting more energy, they provide ‘higher gain’.
High directivity → Better focus → Higher spectral efficiency
When you have more antennas in a gNodeB, typically arranged in a 2D array, you have two options:
Each antenna can send signals in separate directions.
All the antennas in the array can act cohesively as one entity.
When all the antennas focus their energy in the same direction, high directivity is provided.
Higher Pathloss and directivity → Better spatial reuse
5G NRmmWave is Bringing New Waves of Opportunities
For outdoor deployments
Significantly elevate today’s mobile experiences - initially focusing on smartphones.
Deployments predominantly driven by mobile operators - initially focusing on dense urban.
For indoor deployments
Complementing existing wireless services provided by Wi-Fi - also expanding to new device types.
Bringing superior speeds and virtually unlimited capacity for enhanced experiences.
mmWave could replace fiber backhaul at a cost-efficient manner
Particularly beneficial in rural deployments with low building and user densities.
mmWave base stations don’t have to be rooted on the ground. They can placed on trucks to provide mobility and flexibility.
