5G wireless communications should bring increased network capacity, higher peak data rates, and more reliable service in mobile communications systems. Many of the goals are 10x, 100x or 1000x today's performance but aren't achievable in the currently available spectrum below 6 GHz. Therefore, new air interfaces are being investigated in Centimeter (cm) and Millimeter-wave (mmWave) frequencies up to 100 GHz. Characterization of the radio channel at mmWave frequencies presents many new challenges for engineers. Here are some of these challenges and some considerations.
To define new air interface standards, researchers will need to characterize the radio channel so they can understand how the signal will propagate. Researchers are using channel sounding techniques to collect the CIR (channel impulse response) data so they can extract channel parameters by using channel parameter estimation algorithms. The extracted data are then used for developing new channel models as shown in Figure 1. Sounds straightforward and easy, right?
Well, not quite.
Figure 1. The model of a wireless transmission channel consists of channel sounding, estimating of channel parameters, and statistics.
Channel sounding measurement systems can range from simple to complex depending on parameters being estimated. When measuring time-varying channels with multipath propagation, you need to understand the complex impulse response with time and phase information. In addition, one of the key challenges is being able to duplicate or validate the measurements with different measurement systems in similar conditions.
Key technical challenges include:
- Signal generation and analysis at mmWave frequencies with greater than 500 MHz bandwidth and with multi-channel support
- Data capture and storage
- Channel parameter estimations
- Calibration and synchronization
Now let's discuss considerations to help you address these challenges.
Next: Starting with signal