5G Antenna Design Challenges And How To Overcome Them
As we move along 2021, cellular technology continues to make advances to cater to the ever-growing demand for higher data rates, lower latency, and improved reliability. At the heart of these developments lies radio-frequency (RF) system design. Overcoming design challenges is essential to enable the 5G network and cellular devices to deliver more data to an increasing number of users in growing use cases.
As the infrastructure develops, so does the need for 5G installation work and training, how It works. Information on specifications that meet the requirements for 5G is being released by the 3rd Generation Partnership Project (3GPP). However, there is some miscommunication among OEMs as they prepare to launch 5G enabled devices and products on the market.
Most of the confusion stems from antenna design, and this is because this aspect of the process relies almost exclusively on OEMs’ preferences as well as the end device form factor. In today’s blog, we talk about different approaches to 5G antenna design.
5G vs. 4G
Before we can delve into the specifics, let us first try to understand the unique requirements of the new networks that didn’t exist in previous generations. This will help us to explain the different challenges and approaches to 5G User Equipment (UE) antenna design. Some basic terms to remember include:
- Channel capacity per bit/second (C)
- Number of channels (M)
- The bandwidth of channels (B)
- Signal to noise ratio (S/N)
The Shannon-Hartley theorem (C = M * B log2(1 + S/N)) shows how 5G can deliver higher data rates than the existing technology. To provide greater channel capacity, the new networks require adjustments to the abovementioned specifics. 5G comes with effective measures in its architecture to achieve this. For instance, carrier aggregation (CA) and the allocation of new frequency bands will increase B, which M can be improved with the multiple-in-multiple-out (MIMO) architecture. Moreover, the adaption of higher-order modulation schemes will improve both B and S/N.
5G takes the existing techniques to a whole new level of complexity. And this complexity also includes antenna design to meet the growing need for more bandwidth and frequency bands with improved immunity from interference. Currently, bucket trucks are being rolled out to carry light antennas for coverage.
The Problem of Co-existence
Co-existence refers to multiple antennas installed on one device and operating on the same frequency bands. This is a basic requirement of MIMO and is being used with existing networks as well.
But while 4G LTE relies on single-user MIMO (SU-MIMO) and multiple-user MIMO (MU-MIMO), 5G calls for massive-MIMO (mMIMO). This is necessary to boost UE downloading data rate and cell capacity. Current designs focus on the base station that requires a minimum of 32 logical antenna ports, but these are likely to increase in future iterations.
The problem of co-existence is further exacerbated with Multiple Access offered by 5G, i.e. enabling cellular, Bluetooth, WLAN, etc to transmit on the UE at the same time. This can cause problems like blind spots and range reduction.
Major Design Considerations
There are two main roadblocks when it comes to creating antennas for the new network:
New Frequency Ranges
The 5G network will rely on two new frequency bands as per 3GPP Release 15. These are:
- FR1 (410 MHz to 7.125 GHz)
- FR2 (24.5 to 52.6 GHz)
5G adopts the frequency bands in FR1 from existing 4G LTE sub-3GHz bands. However, new specifications for antennas and bucket trucks are needed to provide coverage in the sub-6GHz range.
FR2, also known as the mmWave frequency range, provides bandwidth up to 2 GHz in some regions, which is a decent bandwidth. But path losses are common and severe in this range (the lower the signal wavelength, the higher the signal propagation loss). To overcome this problem, phased-array antennas with high gain can be used.
Antenna Tuners
The latest wireless devices have strict size limitations, and active antenna tuners are used to shrink the size. These tuners adjust the antenna smartly according to coverage, frequency, and the operating environment. As 5G comes with greater CA (as well as more cellular bands), the latest antenna tuners will have to support more tuner states and wider frequency within each state. Conversely, there are two main design approaches to overcome these challenges:
mmWave
Designing antennas for the FR range require a greater upfront knowledge of design concepts, practices, and signal behaviour, far beyond a basic knowledge of 5G installation work and training, how It works.
Even at the most basic level, phased-array antennas should be able to maximise the peak EIRP (dBm) towards user devices in a cell sector by steering and optimising the radiation beam. It will help to overcome the signal losses described above. Some of the key factors to consider include:
- Dual polarisation
- Array size
- Sidelobe level
- Beam steering angle range
- Beam steering angle resolution
- System noise
Overcoming these issues requires intensive and costly testing.
Sub-6 GHz
Finally, designing antennas for sub-6 GHz capacity is relatively easier, since the design concepts are common between 4G and 5G networks, except lateral complexity. Moreover, many of these same antenna types can be used to achieve these frequency bands, such as:
- Dipole antennas
- Monopole antennas
- PIFA
- IFA
- Loop antennas
An active antenna system needs to be designed to overcome the challenge of a smaller device and larger antenna bandwidth.
