Millimeter Wave Bands Comes under Extremely High frequency Band (EHF) range as EHF ranges from 30 to 300 GHz.
Frequency range:
The millimeter wave band spans 30 to 300 GHz.
What is the significance of its name?
Here in millimeter wave (mm wave) wavelength is very short. We know,
wavelength = (1 / frequency)
As this frequency band spans from 30 GHz to 300 GHz
So, (1 / 30 GHz) = 10 millimeter &
(1 / 300 GHz) = 1 millimeter
As wavelength ranges between 1 millimeter to 10 millimeter. So, it is called millimeter wave.
Unfavorable bands in Millimeter wave band:
The 57-64 GHz millimeter wave range is easily absorbed by oxygen, while the 164-200 GHz spectrum is absorbed by vapor.
Huge Spectrum Resource:
As we've already mentioned above that some frequencies in millimeter wave are not suitable for distant communication as they are absorbed by atmospheric gases, but there available bandwidth is still greater than 150 GHz. We can use these frequencies for feasible communication.
High Path loss:
The millimeter wave band allows us to attain high data rates and meet high bandwidth demands, but it also has several drawbacks. Because the frequency is so high, there is a lot of path loss. We know that path loss grows at a square proportional rate in relation to operation frequency. As a result, we can simply deduce that the path loss will be significant.
Severe Penetration Loss:
The wavelength of the millimeter wave band, on the other hand, is relatively tiny in the millimeter range (i.e., 1 millimeter to 10 millimeter). As a result, it has a hard time propagating through building walls or obstacles. The Line of Sight Communication (LOS) path might easily be blocked as a result of this. As a result, we rely on stronger Non Line of Sight (NLOS) pathways for such a high frequency band.
High Reflective and Refractive Properties:
Because of its higher frequency, this band has excellent reflecting and refractive properties. It is easily reflected / refracted by building walls and glasses, resulting in a greater number of multipath communication or MPCs between transmitter and receiver, but only a few MPCs are available for communication. The incidence and reflection angles are not the same in refraction. When an EM wave collides with an uneven plane, it typically reflects from that uneven plane in a variety of angles and directions.
When the wavelength is extremely short, it tends to be more refractive. Massive MIMO integration in the millimeter wave frequency, on the other hand, enables more efficient use of the huge spectrum available.
Why millimeter wave band is important for 5G communication
We are all aware that the number of internet-connected gadgets has surpassed 50 billion and is continually growing. And the number is rapidly increasing as the number of internet-connected IoT devices and sensors grows. Most countries are now using the sub-6 GHz band for 5G, although bandwidth congestion is expected in the near future. As we all know, bandwidth allocated for a specific service is limited, and the number of connected devices is continuously growing, we require more bandwidth to communicate with all connected devices in a seamless manner. In the near future, the millimeter wave band will meet the demand.
Why mmwave communication more susceptible to noise?
Mm-Wave Pathloss & Propagation
Large-Scale Parameters (LSP)
LSPs represent power variations over long distances. The primary factors are Path Loss (distance-based decay) and Shadowing (blocking by buildings or trees).
Small-Scale Parameters (SSP)
SSPs represent rapid fluctuations (fading) caused by Multipath Components (MPCs) and Doppler spreads. In mmWave, these are often grouped into Clusters arriving from similar angles.
Spatial Consistency
Small-scale parameters must remain consistent as a user moves. Segments of 10–15 meters are typically used where channel conditions are strongly correlated.
The Close-In (CI) Pathloss Model
The CI model is widely used for mmWave because it provides high precision across various environments using a log-normal distribution.
*A higher pathloss exponent (\(n\)) indicates a more obstructed environment where signal strength drops more rapidly.
Massive MIMO Channel Model (mmWave)
The Saleh-Valenzuela (SV) Model
Because mmWave signals have high path loss and sparse scattering, they are modeled using Clusters. In the SV model, the channel is not just a single path, but a collection of clusters, where each cluster contains multiple sub-paths or "rays."
Arrival Statistics: Both cluster and ray arrivals follow a Poisson Distribution.
• \(\Lambda\): Cluster arrival rate.
• \(\Gamma\): Ray arrival rate.
The Channel Matrix \(H\):
Antenna Array Geometry
Elements arranged in a 1D line. Best for calculating simple Angle of Arrival (AoA).
Elements arranged in a 2D grid. Required for 3D beamforming (Azimuth + Elevation).
Why Geometry Matters:
As a signal hits an array, it reaches different elements at different times, creating a Phase Difference (\(d \cos \theta\)). Massive MIMO exploits this phase difference to perform spatial multiplexing and beamforming.
Millimeter-wave (30 GHz to 300 GHz) is a cornerstone of 5G, offering massive bandwidth (over 150 GHz) to meet the demand for 1000x more data traffic. While it provides ultra-high speeds, it faces significant challenges: severe path loss, high penetration loss through walls, and atmospheric absorption.
Massive MIMO
Short wavelengths allow hundreds of antenna elements to be packed into small spaces, creating narrow, high-gain beams to overcome path loss.
Click Here to Read More about Massive MIMO
Beamforming Gain
By spacing antennas at half-wavelength intervals, systems focus energy in specific directions, reducing interference and boosting efficiency.
Click Here to Read More about Beamforming
Future Applications
- Vehicular: Supports self-driving cars needing 1TB of data per hour with low-latency links.
- Indoor/IoT: Enables factory automation and massive IoT via high-precision positioning and high-rate indoor links.