Time-delayed saleh valenzuala cluster model for UWB & mm-Wave
Multipath components (MPCs) travelling near in time and arriving from potentially varied angle orientations in a brief propagation time window make up time clusters.
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We employ a Low Pass Filter (LPF) or circuit switching to detect the signal at the receiver side, which can detect a signal of a particular time duration (say, Ts). Keep in mind that the above signal, also known as the CIR, is a combination of delayed versions of a single impulse.
Saleh Valenzuela Channel Model (for UWB & Millimeter Wave Band)
Extremely high frequencies, like, millimeter wave (mm Wave) band or Ultra Wideband (UWB) which contributes high pathloss and its show multiple reflection and refraction property due to very short wavelength. If we deploy Massive MIMO system in such extremely high frequencies then channel matrix becomes sparse because multiple reflection and refraction weaken the signal strength and only few multi-paths (MPCs) riches to receiver with acceptable power. On the other hand we receive multiple copies of same signal at receiver side due to multiple reflection of same signal before reaching at receiver. So, we observe time dispersion property of signal. This time dispersion property is modelled as the extended Saleh Valenzuela model (clustered channel model) which is a frequently utilized model that enables us collect characteristics properly over Mm Wave channels or UWB communication channel.
Figure: Saleh Valenzuala Channel Model for UWB and mmWave Communication
Here in the above figure we have shown Saleh Valenzuala Channel Model which is basically based on exponentially decreasing amplitude of rays and clusters and also based on time delays or dispersion of same signal as well. For exam if we're sending high frequency narrow pulse from transmitter side, then we receive multiple copies of same signal with delays at receiver side due to multipath (MPCs). Here, each sample in a cluster is called ray or MPC. You will see here multiple clusters are formed. Let me tell what exactly cluster is
Cluster & Ray in Saleh Valenzuala Model
For extremely high frequency communication, time dispersion of signal is common. Here we observe some rays or MPCs arrive at receiver close in time or you can say they are close in spatial domain in CIR (channel impulse response graph). In the above figure you see multiple clusters and rays for same signal transmitted from Tx side. Here, t11, t12, and t13 are very close in time but there is significant different between t13 and t21. For simplicity, t11, t12, and t13 are rays in cluster 1 and t21, t22, and t23 are rays in cluster 2. Two clusters are not close in time at all.
During transmission signal at receiver, reaches with different angle of arrivals (AoA). That's why there are different clusters are formed. But only close in time rays or MPCs form a cluster. Other rays close in time form another cluster as well.
You also see rays in same cluster are continually decreasing in amplitude with time delay. And same thing happens for clusters. They are also decreasing in amplitude with time delay of received signal.
For Practice systems
- Saleh Valenzuala Model is widely acceptable model for clustered delay model where operating frequency is very high and signal has multiple reflection and refraction property.
- In Saleh valenzuala model cluster arrival rate and ray arrival rate are very important. sometimes we take in consideration of mixed probability of cluster arrival rate for simplicity in calculation
- In this model amplitude of received signal is also important. In this case also, we sometimes take average amplitude or power of signal as well.
- If we increase the operating frequency continuously then in general, number of clusters decrease.
- Similarly, for a particular environment, if signal becomes more reflected than other environment then number of clusters also decreases.
