Analyst house ABI Research looks at how full duplex microwave innovations are boosting 5G spectrum efficiency, helping operators meet growing backhaul demands, overcome spectrum limitations, and enable high-capacity, cost-effective wireless connectivity.
Wireless backhaul is a critical component of any mobile network, as it is the link supporting voice and data transport between the core network and radio access network (RAN) sites. Wireless backhaul, such as microwave and millimeter wave (mmWave), continues to be a key backbone technology, with ABI Research forecasting that over 50% of backhaul traffic is carried over microwave and mmWave links.
Backhaul capacity requirements are anticipated to continue growing, so the microwave equipment sector has been spearheading several key developments and innovations.
Key industry trends
1. Demand for backhaul capacity
Exceeding earlier forecasts, annual 5G subscriptions from the top 30 countries monitored by ABI Research reached 2.1 billion at the end of 2024 and they are expected to grow to over 4.3 billion by the end of 2030. Accordingly, 5G data traffic is forecast to increase from over 480 exabytes in 2024 to 2,800 exabytes in 2030 – a compound annual growth rate (CAGR) of 32%. This growth is driven by increasing consumption of high-resolution video streaming services, both downloads and uploads, as well as higher adoption of generative AI (gen AI) mobile applications.
The above developments are expected to drive demand for higher backhaul capacities, especially in urban areas. ABI Research expects backhaul capacity throughput requirements to grow quickly, reaching 25 Gbps in urban scenarios. This is driven by traffic carried over 5G mid-band, a selective deployment of 5G high-band, and the decreasing installed base of 4G end users by 2030.
2. Increased competition for spectrum
Recent developments at the World Radiocommunication Conference 2023 (WRC-23) also introduced new challenges to the microwave industry in terms of spectrum availability. Region 1 and Region 3 have identified the 6,425-7,125 MHz and 7,025-7,125 MHz spectrum ranges for International Mobile Telecommunications (IMT) services, respectively. Additionally, to facilitate 6G deployment, the WRC-23 agreed to study the 7,125-8,400 MHz frequency band of (or parts thereof) and 14.8-15.35 GHz for IMT, thus creating even more competition for spectrum use in traditional microwave frequency bands.
At the same time, other countries, such as the US, Canada, Saudi Arabia, and South Korea, have identified the entire 6 GHz band (5,925-7,125 MHz) for license-exempt access, which will support other wireless access technologies such as Wi-Fi. This also creates a challenge for microwave deployment due to interference concerns.
3. Insufficient spectrum channel sizes
Limitations to microwave channel sizes is another challenge for wireless backhaul deployments. According to the European Telecommunications Standards Institute (ETSI), the majority of countries surveyed (74%) had maximum E-band channel sizes of 1,000 MHz and below. This restriction, which limited E-band deployments to 5,600 Mbps at 256 quadrature amplitude modulation (QAM), prevented operators from realizing the full potential of the technology.
Microwave spectrum trends
To adequately address communications service providers’ (CSPs’) concerns on backhaul capacity, microwave solutions providers have been able to rise to the challenge and deliver enhanced spectrum efficiencies. These developments are largely centered around the following key technologies.
1. Higher / adaptive modulation schemes
QAM is a frequently used technique for microwave backhaul applications that combines amplitude and phase modulation to transmit more data in one signal. Rather than only sending 0s and 1s, this technology uses points on a constellation diagram, with different values assigned to each point. For example, 4 QAM has 4 points, which enables the transmission of 2 bits per symbol, while 16 QAM has 16 points in the constellation, which supports 4 bits per symbol.
However, this technique has a limitation in that it sees diminishing returns as QAM levels increase. It was reported that beyond 1024 QAM, spectral efficiency gain is less than 10% for each incremental step (i.e., to 2048 QAM and beyond). Operators will need to balance between enhancing capacity via increasing QAM levels against decreasing radio frequency performance due to increased interference risks.
Adaptive modulation is a tool used to adjust the modulation of a signal depending on the existing condition of the channel between the transmitter and receiver. For example, when the channel is experiencing sub-optimal conditions, such as rain, adaptive modulation allows for the adjustment of modulation schemes to increase signal throughput, a feature that is not available with fixed modulation schemes.
2. Spectral efficiency – via interference cancelling
Cross-polarization interference cancelling (XPIC) can potentially double the capacity of a microwave link by doubling its spectral efficiency. This is done by propagating two signals horizontally and vertically over the same channel, increasing channel reusability. This allows for an increase in both coverage and the number of links using the same spectrum band.
XPIC also cancels interference brought about by atmospheric attenuation (e.g., raindrops, which cause polarization rotation as they fall, skewing a signal’s polarization out of alignment and causing interference with other polarized signals). XPIC samples signals in both polarizations to cancel the effects of any interference. Essentially, link capacity can be doubled through XPIC by employing both polarizations to transmit twice the data in the same channel.
3. Spectral efficiency – via antenna separation
Line-of-sight (LOS) multiple-input multiple-output (MIMO) enhances link capacity through increasing spectral efficiency. This is achieved by allowing more data to be transmitted though the same frequency by optimizing the separation between the antennas in the transmit and receive arrays. LOS MIMO links can either be 2X2, with two transmitters and receivers that are connected to two antennas on each side, or 4X4 by using four transmitters and receivers in both horizontal and vertical polarization.
A 4X4 LOS MIMO scheme can enable transmission of four different data streams in the same frequency channel with an effective gain of 4X more capacity than a standard 1+0 single-input, single-output (SISO) link. However, a challenge with this deployment mode is that double the number of antennas need to be installed on a single tower, with a minimum separation distance between them to optimize signal quality. As a result, scaling out such LOS MIMO deployments is challenging due to concerns on accumulating tower-related telco equipment rental costs.
4. Integrated access and backhaul
Integrated Access and Backhaul (IAB) uses access spectrum to backhaul mobile data traffic to the core network. IAB has higher equipment cost efficiencies, as both access and backhaul share the same radio hardware unit and have similar operation/maintenance systems. IAB can also help lower equipment costs, as cell sites do not require separate transmitter-antennas for backhaul links.
However, a limitation to this technology is that it utilizes the same access spectrum for backhaul, potentially affecting customer network experiences. Additionally, there are also risks of IAB interference between access and backhaul links, which may cause half-duplexing.
5. Two-way transmissions
Traditional methods of communication typically use: 1) time division duplex (TDD) technology, where signals are transmitted and received using the same frequency but at different time intervals; and 2) frequency division duplex (FDD) technology, where signals are transmitted and received simultaneously, but using different frequencies. However, a common issue faced by both TDD and FDD technologies is that spectrum usage is not fully maximized.
“Full duplex” is a revolutionary technology that improves spectrum usage by enabling simultaneous sending of data in both directions (i.e., transmitting and receiving) using the same frequency band, effectively doubling spectrum efficiency. This technology also avoids the challenges faced by LOS MIMO deployments by simplifying deployments into a single antenna.
While full duplex transmission introduces increased risks of co-channel interference, various solutions, such as high isolation and interference cancellation, have been developed to maximize the performance of full duplex solutions.
Here are some of the latest developments for full duplex technology:
Huawei: In 2025, Huawei launched the world’s first commercial full duplex microwave solution, MAGICSwave, that can double spectral efficiency with the use of: 1) highly isolated antennas (within a single box); and 2) advanced interference cancellation algorithms to remove interference caused by the environment. In a live test conducted with Turkcell, the full duplex solution was able to support a data throughput of 50 Gbps utilizing the E-band (80 GHz) spectrum.
Nokia: In 2024, Nokia announced the successful demonstration of full duplex fixed point-to-point wireless links in the D-Band (130 – 175 GHz) frequency range. The company reports that its solution achieved 10 Gbps for the uplink and 10 Gbps for the downlink over a single 2 GHz channel. Studies to develop standards governing the use of the D-Band by ETSI and the International Telecommunication Union Radiocommunication Sector (ITU-R) are ongoing.
Summary conclusions
Microwave backhaul technology continues to evolve with the changing requirements of mobile access technology. With increasing competition for spectrum resources, spectral efficiency stands out as a critical component to maximizing backhaul capacities with the limited available spectrum.
At the same time, reducing tower load, operational expenditure, and energy consumption will continue to be key considerations for CSPs. The evolution of microwave technology toward full duplex solutions is timely for helping backhaul networks meet future mobile requirements.
