3GPP has been continuously working towards improving the 5G ecosystem. According to 3GPP Release 16, various features, such as the Integrated Access and Backhaul (IAB), enable the flexible deployment of 5G networks. IAB solution provides a flexible deployment by reusing spectrum resources and physical equipment for both access and backhaul. Furthermore, enhanced beam management can be used to improve latency, efficiency, and performance. This is achieved by full-beam refinement and multi-antenna-panel beam support. Moreover, various power-saving features help maximize each device’s sleep duration and improve the overall system power consumption.
Furthermore, dual connectivity operation is optimized by reducing the device initial access latency and further improve coverage when connected to multiple nodes. Positioning is another aspect for enhancement since the accuracy requirements are set to 3m for indoor connectivity and up to 10m for outdoor connectivity for 80% of the time.
3GPP Release 17
3GPP Release 17 introduces further improvements in IAB, this time for distributed deployment. This release introduces operating in full-duplex mode and introduces mobile relays to improve coverage, capability, and QoS. Coverage & beam management is further optimized by reducing the overhead and enhancing the overall performance with the introduction of beam selection.
Furthermore, the spectrum support is expanded in licensed and unlicensed millimeter-wave frequencies from 52.6 GHz up to 71 GHz. New use cases are introduced, which range beyond the initial eMBB services. These use cases expand the mmWave frequency support for sidelink, URLLC, and industrial IoT use cases such as NR-Light. Further enhancements in positioning are also introduced for a wide range of new use cases, including centimeter-level accuracy, lower latency, and higher capacities.
Distributing antennas are used to improve robustness and coverage in 5G NR mmWave gNodeB and remote radio heads (RRHs). The beam overlap offers an improved angular diversity. MmWave repeaters are used to extend coverage with simple repeaters and smart repeaters in Release 17. This provides flexible spatial reuse from a single mmWave cell.
5G NR mmWave IAB
5G NR mmWave IAB can be used for cost-efficient dense deployments. Whereas traditional fiber backhaul can be expensive for mmWave cell sites, IAB improves coverage and capacity while limiting the backhaul cost. MmWave access inherently requires small cell deployment. However, running fiber to connect each new cell site may not be feasible and can be cost-prohibitive. MmWave backhaul can have a more extended range than access, while mmWave access and backhaul can now flexibly share common resources.
IAB can support a fast and cost-efficient 5G NR mmWave network roll-out. Early 5G NR mmWave deployments were based on Rel-15. This meant that the Operators were deploying new 5G NR mmWave base stations using limited and existing fiber links. IAB can help widen the 5G NR mmWave coverage by incrementally deploying additional base stations, still using existing fiber links, and supporting fast traffic growth with extra fibers. The Operators can now choose to deploy new fiber links for selected IAB nodes according to the capacity demands.
IAB enhancements in R.17
As mentioned above, 3GPP Release 17 introduces new use cases with better capabilities and defines an evolved IAB solution for more flexible and efficient deployment. It has introduced the enhanced distributed IAB concept where a Distributed Unit (DU) can be shared between Centralized Units (CU) and cross-CU configurations. Smarter network planning can be achieved via machine learning network management, zero-network planning, and increased IAB deployment tolerances.
IAB can also offer an efficient power-saving network since it can be powered down during low traffic periods. Furthermore, it may also support a dynamic broadcast configuration and an expanded spectrum, either in unlicensed frequency ranges, such as 37 GHz and 60 GHz, or in higher mmWave bands such as the 71-114.25 GHz spectrum. Mobile relay and sidelink can extend coverage and support disaster areas by offloading and moving base stations for portable deployment.
IAB can use enhanced multiplexing techniques with simultaneous access and backhaul with spatial multiplexing or full-duplex configuration. IAB also supports topological redundancy, with extension to support more than two-parent IAB nodes to achieve better reliability and capacities. Moreover, IAB can also enhance QoS by optimizing the overall 5G system for latency-critical traffic on backhaul and scheduling, signaling improvements for multi-hop connectivity. Finally, AIB can also be used for expanding backhaul services by backhauling LTE and non-3GPP traffic wirelessly over 5G NR mmWave IAB supporting QoS.
Further 5G NR enhancements
3GPP Rel.16 offers improved reliability by supporting multi-beam repetitions. This means more robust beam failure recovery schemes for both UL and DL by using proactive beam set switching and SCell beam failure recovery, together with UL beam failure recovery.
Higher performance can be achieved with multiple antenna panels support improving the overall throughput and diversity. UL/DL beam selection is decoupled for optimal performance in both directions. This is achieved beam management for each device that helps the MPE – Maximum Permissible Exposure.
More efficient beam management techniques help to support higher intra- and L1/L2 inter-cell mobility. This means an expanded beam selection which improves mobility and coverage.
Power consumption enhancements
The evolution of 5G device hardware and functionalities in the millimeter-wave region can also help to reduce the system power consumption and enable significant power savings. New devices are expected to provide additional information for battery level and temperature and allow the network to select carrier or power mode. For example, using lower rank/CA during the power-saving mode. The device can also provide antenna information to enable more power-efficient beam sweeping/switching, a technique also known as multi-panel beam management.
Furthermore, enhanced low-power modes help improve the device power consumption in idle and inactive modes. Efficient carrier aggregation operation can also optimize power consumption by reducing the number of blind decoding. The new 3GPP releases introduce a more efficient channel control management, reducing the processing overhead with control channel (PDCCH) skipping. Moreover, the new systems are expected to use integrated WUR (Wakeup Receiver) with beam management in C-DRX (Connected discontinued receive). This beam-formed wakeup signal improves beam pairing success and extends sleep mode. Power saving ranges from 10% to 80% over baseline C-DRX depending on the Ton and Tcycle configurations.
Enhancements for Industrial IoT
According to Release 17, various enhancements will help to improve the network reliability and performance of Industrial IoT applications. Reliability is enhanced using Multi-beam operation in mmWave transmission. More candidate beams are introduced, such as beam sweeping for DL control, UL control and data, and device-based fast beam update. There are also enhancements regarding latency. These include quicker beam failure detection and recovery procedure activation based on device feedback.
Furthermore, latency is also reduced by enhanced beam management. Overhead reduction is achieved with pre-determined beam switching predictable device movements in the Industrial IoT environment. Enhanced device feedback is also used, with advanced hybrid automatic repeat request (HARQ) feedback and enhanced channel state feedback (CSF).
