Special Articles on 3GPP Release 17 Standardization Activities
Advanced 5G Radio Technologies in 3GPP Release 17
5G NR RAN
Hiroki Harada and Shinya Kumagai
6G-IOWN Promotion Department
Communication Device Development Department
Masato Taniguchi and Hidekazu Shimodaira
Radio Access Network Development Department
Following the Rel-15 specifications at 3GPP for new radio access technology called NR toward 5G, Rel-16 specified enhanced technology from Rel-15 in June 2020. Then, as further enhancements to Rel-15/Rel-16 specifications, 3GPP began Rel-17 specifications in December 2019 and completed the specifications in June 2022. This article presents an overview of advanced 5G radio technologies in Rel-17.
The 3rd Generation Partnership Project (3GPP)*1 ...
The 3rd Generation Partnership Project (3GPP)*1 specified Release 15 (Rel-15) and Rel-16 specifications for New Radio (NR)*2, a new radio access technology toward 5G, including radio technology toward enhanced Mobile BroadBand (eMBB)*3 and further enhancements to eMBB, enhancements toward Ultra-Reliable and Low Latency Communication (URLLC)*4, and technical extensions for creating a new business area called Industrial Internet of Things (IIoT)*5 to promote IoT in industrial fields.
In addition to specifying extensions to Multiple Input Multiple Output (MIMO)*6 functions and URLLC functions specified in previous releases, Rel-17 supports frequency bands up to 52.6-71 GHz to increase transmission data rates, supports Non-Terrestrial Network (NTN)*7 systems that utilize satellites to extend coverage, and adds a NR device category called Reduced Capability (RedCap)*8 to extend 5G use cases. These enhancements aim to contribute to the provision of new value through 5G. Main functions specified in Rel-17 are summarized in Figure 1. In this article, we provide an overview of main technical enhancements specified in Rel-17 and provide some background to their specifications.
- 3GPP: An organization that creates standards for mobile communications systems.
- NR: Radio system standard formulated for 5G. Compared with 4G, NR enables high data rate communications using high frequency bands (e.g. sub-6 GHz bands and 28 GHz band) and low-latency and high-reliability communications for achieving advanced IoT.
- eMBB: Generic name for communications requiring high data rates and large capacity.
- URLLC: Generic name for communications requiring low latency and high reliability.
- IIoT: IoT for industrial fields such as network connections for equipment and devices in a factory and elsewhere.
- MIMO: A signal transmission technology that uses multiple antennas for transmission and reception to transmit signals and improve communications quality and spectral efficiency.
- NTN: A network that extends the communication area to diverse locations including the air, sea, and space using non-terrestrial equipment such as satellites and High Altitude Platform Station (HAPS) aircraft without limiting the coverage area to land.
- RedCap: The name of a simple UE category introduced in Rel-17 NR that reduces device complexity by decreasing the number of transmit/receive antennas and bandwidth mandatorily supported in NR UEs.
2.1 Advanced Technologies toward Mobile Broadband
1) Functional Extensions for Dual Connectivity (DC)*9 and Carrier Aggregation (CA)*10
(a) Reduction of User Equipment (UE)*11 power consumption in DC
3GPP specifications before Rel-17 enabled the use of a power consumption reduction function called Secondary Cell (SCell) deactivation*12. In situations such as when the traffic is temporarily small during CA, this function reduces power consumption by temporarily limiting (deactivating) usage of SCell. SCell deactivation can also be applied to the SCell in SCG, but an issue in Rel-16 was the inability to reduce power consumption in UE in certain cases. For example, the Primary SCell (PSCell)*13 could not be deactivated and power consumption could not be reduced when using high NR frequencies in the PSCell.
In Rel-17, this issue was addressed by adding a Secondary Cell Group (SCG)*14 deactivation*15 function that deactivates the SCG including the PSCell, thereby obtaining a high effect in power consumption reduction in DC.
(b) Reduction of processing delay in DC/CA
To reduce delay in switching between PSCells in DC and to improve communications reliability at the time of switching, Rel-16 specifies technology called Conditional PSCell Change (CPC)*16 to notify the UE of conditions for executing PSCell change and candidate PSCells for switching in advance. Here, Rel-16 CPC only supports the case that the cells before and after CPC belonged to the same base station, but Rel-17 CPC supports performing PSCell change between cells belonging to different base stations. In addition, Conditional PSCell Addition (CPA) was specified in Rel-17. CPA initiates DC with a candidate cell that meets pre-configured conditions as CPC, which enables the delay when initiating DC to be reduced.
From the viewpoint of CA, functional improvements were also made in reducing the delay in reactivating a deactivated SCell by accelerating processing such as time/frequency synchronization*17 by having the UE use the Tracking Reference Signal (TRS)*18 received from the network.
2) Improvements in Throughput*19 and Reliability through Distributed MIMO
In Rel-16 NR, a function is specified for distributed MIMO*20 transmission of DownLink (DL) user data using multiple antenna panels or transmission points of a base station in the same cell. This function enables the use of high-rank transmission and improves reliability.
In Rel-17 NR, distributed MIMO transmission of DL user data can be performed using base-station transmission/reception points in different cells (Figure 2). This expands the scenarios in which distributed MIMO can be applied and improves effective throughput and reliability.
Also specified was a function that enables the UE to repeatedly transmit UpLink (UL)*21 user data and UL physical layer control information to multiple transmission/reception points. When channel quality between the UE and a transmission/reception point deteriorates, this function enables signal transmission using a channel with another transmission/reception point, thereby improving the reliability of the UL.
3) UE Power Savings
Reducing UE power consumption is an important element in improving the user experience*22. In Rel-16, functions are specified for reducing UE power consumption mainly during connected-mode. Rel-17 made further technical extensions to solve some remaining issues in Rel-16 from the viewpoints of reducing UE power consumption during idle/inactive-mode in NR Stand Alone (SA)*23 operation, reducing UE power consumption during connected-mode in Frequency Range 2 (FR2)*24 operation, and making effective use of Rel-16 UE assistant information*25.
Functions for reducing UE power consumption in idle/inactive mode were introduced such as early notification of paging*26 and TRS notification to the UE. Additional functions for reducing UE power consumption during connected-mode were introduced such as skipping of control-channel monitoring, switching of control-channel monitoring settings, and relaxing of UE measurement for radio link monitoring and beam failure detection.
4) Expansion of Coverage*27 Enhancements
Coverage performances constitute an important element in the provision of network services*28 since they affect network quality as well as CAPital EXpenditures (CAPEX)*29 and OPerating EXpenses (OPEX)*30. In Rel-15, technologies that contribute to coverage performances were specified such as repeated transmission in the time domain*31 and aggregation in the frequency domain*32. On the other hand, NR makes use of high frequency bands compared with Long-Term Evolution (LTE), and since propagation loss*33 tends to increase at higher frequencies, it is important to evaluate coverage performances of NR, which was carried out in Rel-17. As a result, the Physical Uplink Shared CHannel (PUSCH)*34, Physical Uplink Control CHannel (PUCCH)*35, and Msg3 PUSCH*36 were identified as channels requiring improvements in coverage performances, and technologies for improving the coverage of these channels were introduced.
To improve PUSCH coverage performances, the maximum number of repeated transmissions that can be indicated to UE was increased, and the number of effective repeated transmissions that can be performed by UE was also increased by introducing repeated transmission based on available UL slots*37. In addition, Transport Block (TB)*38 transmission spanning multiple slots was introduced. For example, as a UE at the edge of the service area would need to transmit PUSCH with a low Modulation and Coding Scheme (MCS)*39 to compensate for the large propagation loss, this would not be very efficient from the viewpoint of coding gain since it would be necessary to transmit data in small-sized TBs in short segments. A single TB transmission over multiple PUSCH slots makes it possible to improve coding gain. Next, as technologies for improving PUCCH coverage performances, dynamic indication of the number of repeated transmissions for PUCCH was introduced so that dynamic change of the number of repeated transmissions according to UE channel quality or other characteristics was made possible. Finally, as technologies for improving Msg3 PUSCH coverage performances, a maximum of 8 repeated transmissions was introduced thereby improving the receive Signal to Noise Ratio (SNR)*40 of Msg3 PUSCH at the base station.
Additionally, with regard to the DeModulation Reference Signal (DM-RS)*41, the bundling*42 of such signals was introduced as a common technology for improving both PUSCH and PUCCH coverage performances. In Rel-15/Rel-16, channel estimation*43 was performed using DM-RS within corresponding PUSCH/PUCCH resources. On the other hand, as shown in Figure 3, the accuracy of channel estimation can be improved by transmitting DM-RS with power consistency and phase continuity across multiple PUSCH/PUCCH resources in multiple slots by the UE so that the base station can perform channel estimation using DM-RS across multiple slots.
5) 1024 Quadrature Amplitude Modulation (1024QAM)*44 for DL
The 256QAM*45 scheme could be used for data modulation in both the DL/UL up to Rel-16 NR. In Rel-17 NR, 1024QAM was introduced for DL to increase the data rate and improve spectral efficiency*46, and since it was a function that had already been specified in LTE, it was thought that this scheme should be supported in NR too. The 1024QAM scheme targets scenarios with a sufficiently large Signal to Interference plus Noise power Ratio (SINR)*47, so it would be applicable only to environments in which there is no UE movement at all or practically no movement. It is therefore a function that is envisioned mainly for static links such as in Fixed Wireless Access (FWA)*48. To support 1024QAM, Rel-17 added a Channel Quality Indicator (CQI)*49 table and MCS table, and Rel-17 specified a density determination method of the Phase-Tracking Reference Signal (PT-RS)*50 within frequency/time resources for the new MCS table.
6) Frequency Extension to 52.6-71 GHz Band
3GPP specifications in Rel-16 and before specified the 0.41-7.125 GHz band (FR1*51) and 24.25-52.6 GHz band (FR2) as available frequencies. In Rel-17, following the agreement at World Radiocommunication Conference (WRC)*52-19 on using the 66-71 GHz band as frequencies for International Mobile Telecommunications (IMT) and completion of the IEEE 802.11ad/ay*53 standard using the unlicensed 57-66 GHz band, the 52.6-71 GHz frequency range was newly supported. This frequency extension enabled further expansion of communications capacity.
Newly supported functions for operating NR in the new frequency range include high SubCarrier Spacing (SCS) and wide channel bandwidth, a channel access technique for using unlicensed bands*54, and mechanisms for reducing UE burden caused by processing for transmitting/receiving the UE control channel and data channel in the high frequency.
7) Optimization for Multi-Subscriber Identity Module (SIM) UE*55
In the case of a Multi-SIM UE in which all SIMs cannot perform communications simultaneously, communications with multiple networks must be performed using a limited transmitter/receiver in which SIMs other than the one currently communicating are occasionally put into standby for incoming calls from other networks. Before Rel-17, this problem had been solved by UE implementations, but with the harmonizing of UE behavior and network operation, functions for Multi-SIM UE were specified in Rel-17 to optimize its performance.
These include a function for avoiding paging collisions between networks that are each communicating with a SIM, a function for assisting in the switching to another network (terminating communications with the currently communicating network or intermittently suspending communications), and a function for notifying the UE whether paging that occurs while communication is in progress with a certain SIM is an incoming voice call to enable the UE to respond to that voice call incoming to another SIM.
8) Quality of Experience (QoE)*56 Measurement in NR
Rel-15 LTE specified a function in which the UE measures QoE in the service application layer as in video streaming and reports the result of that measurement to the network. In Rel-17, QoE measurements in NR are specified to support measuring QoE in NR in the application layer for streaming, voice calls, and Virtual Reality (VR)*57. As newly added functions unique to Rel-17, there is a function for measuring QoE in each slice in network slicing*58 architecture and a function for assisting in Radio Access Network (RAN)*59 optimization by reporting the results of QoE measurements in a form that can be referenced by RAN.
9) Functional Extensions to Self-Organizing Network (SON)*60 and Minimization of Drive Test (MDT)*61
SON/MDT basic functions were introduced in NR Rel-16. Rel-17 introduced functional extensions including cell coverage optimization, Physical Cell ID (PCI)*62 collision avoidance, collection of information on latent problems in a successful HandOver (HO)*63, automatic activating/deactivating of an NR cell in Evolved Universal Terrestrial Radio Access Network - NR Dual Connectivity (EN-DC)*64, load distribution between LTE/NR cells, and information collection on the failure of a Conditional HO (CHO)*65 or Dual Active Protocol Stack (DAPS)*66 HO specified in Rel-16.
10) High Power UE (HPUE)*67 Specification
The transmission power of a handheld UE*68 has been specified as a maximum 23 dBm as Power Class 3 (PC3)*69, but the PC2 specification that enables transmission at an output power 3 dB greater than PC3 has also come to be introduced as the HPUE specification. Although PC2 targeted only EN-DC up to Rel-16, target scenarios in Rel-17 have been extended to NR-CA*70 and Supplementary UpLink (SUL)*71, and while only Time Division Duplex (TDD)*72 bands were targeted in the past, supported bands have also been extended to include Frequency Division Duplex (FDD)*73 bands. In addition, the PC1.5 specification that enables transmission at an output power 3 dB greater than PC2 has been introduced targeting Band n77*74, n78, and n79. Since these are specifications that take existing regulatory requirements into account, there are limitations in setting an appropriate duty cycle*75. However, the UEs targeted include not only those for FWA, for which high transmission power is relatively easy, but handheld UEs as well. These functions are expected to have the effect of expanding UL coverage in a wide range of use cases.
11) Enhanced Radio Frequency (RF)*76 Performance Specifications
For FR1, Tx antenna switching*77 was enhanced from Rel-16 in conjunction with enhancements to UE RF architecture to enable the limited RF chain*78 to be used with a number of carriers and MIMO layers that could provide higher quality. Also targeting FR1 was an HPUE specification during UL intra-band CA and an extension to UL MIMO application cases. Extended functions are shown in Figure 4. Specifically, while Tx antenna switching in Rel-16 provided for the case of 1Tx by one carrier (enabling the use of only that port) and 2Tx by another carrier (enabling the use of both ports), Rel-17 extended this to the case of 2Tx use by both carriers. It also specified HPUE to increase transmission power and extended RF specifications*79 during dual use of UL CA and UL MIMO to increase the number of MIMO layers in transmission. In terms of RF performance, these enhancements are expected to improve UL throughput.
For FR2, while discussions could not be completed in Rel-16, performance-related specifications toward higher data rates were presented for study items related to improving RF performance. Specifically, these were the drafting of performance specifications in FR2 inter-band DL CA for bundling nearby but different frequency bands such as 28 GHz + 28 GHz or 40 GHz + 40 GHz, performance specifications in FR2 inter-band UL CA to enable the UE to form different beams for each band, and gap specifications used in calibration for maintaining stable communications. Inter-band CA extensions are shown in Figure 5.
12) Radio Resource Management (RRM)*80 Enhancements
Further enhancements to RRM include an RRM specification for antenna port switching of the Sounding Reference Signal (SRS)*81 for optimal UL transmission antenna selection, an RRM specification for HO with PSCell when performing HO from NR SA to EN-DC to enable an optimal EN-DC cell combination immediately after the HO, and an RRM specification for cell activation timing when using a PUCCH SCell, all of which aim to guarantee UE minimally required performance. The commercial introduction of these functions is expected to improve user experience.
Additionally, to make Measurement Gap (MG)*82 settings more flexible and reduce transmission gaps, three new functions have been specified: a preconfigured MG pattern that allows for different MG settings in each BandWidth Part (BWP)*83, multiple concurrent and independent MG patterns that enable simultaneous and efficient use of multiple gaps having different applications, and network controlled small gap that minimizes the transmission gap by using only the minimally required gap. These evolved functions are expected to reduce transmission gaps and improve throughput.
13) Performance Enhancements for High-speed Mobile Environments
In Rel-16, discussions were held on specifying minimally required performance for a High-Speed Train (HST)*84 scenario for environments up to a maximum traveling speed of 500 km/h and a maximum frequency of 3.6 GHz. In Rel-17, a new CA specification was drafted to accommodate even higher HST traveling speeds. Additionally, while Rel-16 HST targeted only FR1, Rel-17 extended this specification to FR2. This specification targeting FR2 is basically the same as Rel-16 FR1, but maximum traveling speed is 350 km/h and the maximum frequency that can be applied is 30 GHz. This will enable FR2 to be used with only a single carrier in a high-speed mobile environment, which is expected to expand coverage for high-speed communications.
14) Enhanced Signal-demodulation Specifications for UE and Base Station
UE demodulation*85 specifications that were not drafted in Rel-15 and Rel-16 were drafted in Rel-17 with the aim of improving throughput on both DL and UL. Specifically, these are specifications for an advanced receiver to reduce inter-cell interference on the DL and inter-UE interference and performance specifications for FR1 UL 256QAM.
15) NR Repeater*86
An RF repeater has been used in 2G, 3G, and LTE, and in Rel-17, a NR performance specification was discussed and drafted. In particular, given that maintaining coverage is an issue in high frequency bands above 3 GHz, which are mainly used for high-speed communications, due to high signal attenuation, the use of RF repeaters is expected to expand the 5G area in which high-speed communications can be used and reduce dead zones.
2.2 Advanced Technologies toward Industry Creation and Co-creation of Solutions
1) Enhancements for IIoT and URLLC
In Rel-16, a function was incorporated for synchronizing the base station and UE for such applications as device control in factories. However, at the time of Rel-16, a problem still remained in that errors could occur whenever the signal propagation delay between the base station and UE was too large due, for example, to a wide area covered by the base station. To address this problem, a function that could compensate for this propagation delay error was incorporated in Rel-17, enabling synchronization even across a wider area.
Additionally, while Rel-16 enabled NR to be operated in an unlicensed band*87 toward eMBB, Rel-17 made a functional enhancement enabling URLLC in unlicensed bands and in environments where unexpected interference from other systems and/or radio access technology only sporadically happens.
Furthermore, to reduce latency and improve reliability, functional enhancements were made to the scheduling of packets with different priorities and to retransmission control as well as to reports from the UE on channel conditions.
2) Simple NR UE for IoT Services
RedCap targeting middle-range IoT services lying between low-end IoT provided by LTE-IoT and high-end IoT such as URLLC and IIoT provided by NR have been specified in Rel-17. RedCap targets use cases such as video surveillance, wearables, and industrial wireless sensors, and to reduce UE complexity/cost while satisfying requirements of those use cases, the maximum bandwidth supported by the UE, the number of receive antenna branches and maximum number of DL MIMO layers*88, the highest modulation level*89, and the duplex operation*90 have been simplified compared with Rel-15/Rel-16 NR UEs. In making this simplification, it was assumed that non-RedCap UEs would be operating in the same cell, so specifications for operating in BWPs different than those of non-RedCap UEs and a function enabling a RedCap UE to notify the base station and identify itself as RedCap during initial access were specified.
3) Positioning in NR
A function for estimating UE position using Radio Access Technology (RAT)*91 signals has been supported since LTE, but it was first supported for NR in Rel-16. Specifically, Rel-16 NR supported Enhanced Cell-ID (E-CID)*92, DL Time Difference of Arrival (DL-TDOA)*93, UL-TDOA*94, Multiple-Round Trip Time (Multi-RTT)*95, UL Angle of Arrival (UL-AoA)*96 and DL Angle of Departure (DL-AoD)*97 positioning methods, thereby enabling RAT-based positioning in NR as well.
In Rel-17 NR, discussions were held on functional enhancements for industrial use in factories and elsewhere in addition to general use cases, and functional enhancements targeting positioning accuracy on the sub-meter level and positioning processing delay on the physical layer under 10 ms were made into specifications.
While LTE/NR specifications up to Rel-16 targeted terrestrial networks, Rel-17 specified wireless technologies toward NTN for communications via satellites and aircraft with the aim of expanding the 5G coverage area. Issues in NTN include extremely large propagation delay and a small difference in signal quality between the cell connected to the UE and adjacent cells. As to the former issue, technology involved in establishing and maintaining synchronization and technology for scheduling and enabling a Hybrid Automatic Repeat reQuest (HARQ)*98 and making those processes highly efficient were studied and introduced. As to the latter issue, specifications were made for technology that executes a HO based on information other than signal quality.
5) Functional Extensions toward Network Slicing
(a) Standby cell selection taking slice into account
There are cases in which a network slice that provides services performs different operations depending on the frequency or cell. In such cases, while the UE may connect to a cell with good signal quality, the slice that the user wishes to use in that cell may not be provided. Specifications up to Rel-16 supported an operation that moves to another cell based on instructions from the network after connection. However, Rel-17 performs broadcasting slice supported in the cell in advance, thereby enabling use of the desired slice without having to wait for instructions from the network.
(b) Priority control of Random Access CHannel (RACH)*99 taking slice into account
In specifications up to Rel-16, it was possible to take a network slice into account in allocating resources during communications through base-station operations, but slicing was not taken into account by the RACH used to initiate communications. Consequently, if RACH is congested, a bottleneck may occur in the RACH handling communications for the slice that wants to provide services on a priority basis, thereby preventing initiation of communications. Rel-17 specifications prescribe a function for detaching from or for performing priority control of RACH depending on the slice. The addition of this function enables resource control to be applied according to slice even when initiating communications.
6) Efficient Transmission of Small Data
To reduce UE power consumption and signal overhead in low-capacity, low-frequency communications typified by instant messages from smartphones or sensing data from IoT or wearable terminals, Rel-17 adds a function for transmitting data by a simple procedure even in an RRC_INACTIVE*100 state.
7) Communications via Relay*101 UE (Sidelink Relay*102)
Rel-17 specified a UE-to-network relay that enables a UE (remote UE) to communicate with the network via another UE (relay UE). This technology enables a remote UE that is currently positioned under a cell other than the communicating cell or out of range of the network to nevertheless communicate. This ability is expected to have the effect of extending the service provision area.
- DC: A technology whereby a single terminal connects to multiple base stations using different frequency bands.
- CA: A technology that achieves higher transmission speeds by transmitting and receiving data using multiple carriers supported by a single base station.
- UE: A mobile device having functions conforming to 3GPP.
- SCell deactivation: Technology that reduces UE and network power consumption by deactivating carriers other than those in CA that are maintaining the connection (PCell, PScell).
- PSCell: For DC or MR-DC, the component carrier that maintains the connection, among the component carriers supported by the secondary base station.
- SCG: Among base stations in DC, the cell group subordinate to the base station, or Secondary Node (SN), that does not establish a connection with the terminal.
- SCG deactivation: Technology that reduces UE and network power consumption by deactivating the SCG.
- CPC: One method for executing a PScell change. Instead of giving instructions at the time of executing a PScell change, the network notifies the UE of the candidate cells for switching and switching conditions beforehand.
- Time/frequency synchronization: The state in which the speed of keeping time is consistent from one piece of equipment to the next.
- TRS: A reference signal used for tracking fluctuations in time and frequency on the downlink.
- Throughput: The amount of data transferred through a system without error per unit time.
- Distributed MIMO: A MIMO transmission technology that transmits different MIMO streams from multiple base stations to a single mobile station.
- UL: The flow of information from terminals to the network.
- User experience: A general term for the experiences gained through the use or consumption of certain products or services.
- SA: An operation format in which the terminal connects to the mobile communications network using a single wireless technology.
- FR2: A frequency band specified in 3GPP ranging from 24,250 to 52,600 MHz.
- UE assistant information: Information on UE state and requests from the UE that are to be transmitted to the base station for use in performing appropriate scheduling.
- Paging: A procedure and signal for calling a terminal while camped in a standby zone at the time of an incoming call. Since a terminal does not know beforehand whether a paging message addressed to itself exists, early notification of paging and reduction of unnecessary synchronization processing can reduce UE power consumption.
- Coverage: In wireless communications such as mobile phones, the area in which radio signals can be transmitted and received.
- Network services: The provision of information communications and services to users of a telecommunications network.
- CAPEX: Amount of money expended for investing in facilities.
- OPEX: The amount of money expended for maintaining and operating facilities.
- Time domain: In signal analysis, this domain is used to show the temporal makeup of a signal's components. A time-domain signal can be converted to a frequency-domain signal by a Fourier transform.
- Frequency domain: In signal analysis, this domain is used to show the frequency makeup of a signal's components. A frequency-domain signal can be converted to a time-domain signal by an inverse Fourier transform.
- Propagation loss: The amount of power attenuated in a signal emitted from a transmitting station until it reaches the receiving point.
- PUSCH: Shared channel used for sending and receiving data in the uplink.
- PUCCH: Physical channel used for sending and receiving control signals in the uplink.
- Msg3 PUSCH: An uplink data channel scheduled with respect to UE Physical Random Access CHannel (PRACH) transmissions in a random access procedure.
- Available UL slots: UL slots in which PUSCH and PUCCH can transmit.
- TB: A basic unit used when processing data transmissions and the like.
- MCS: Combinations of modulation scheme and coding rate decided on beforehand when performing adaptive modulation and coding.
- Receive SNR: The ratio of received power of the desired signal to noise.
- DM-RS: A reference signal used for channel estimation, used for decoding data transmitted on the uplink and downlink.
- Bundling: The combining and running of multiple functions or elements.
- Channel estimation: The process of estimating the amount of attenuation and phase rotation acquired by the signal while propagating via the wireless channel. Estimated values so obtained (channel information) are used on the receive side for separating MIMO signals and performing demodulation as well as for optimizing the transmit signal.
- 1024QAM: A type of modulation scheme that modulates data bits at 1,024 signal points differing in amplitude and phase. A single modulation can transmit 10 bits of data.
- 256QAM: A type of modulation scheme. 256QAM modulates data bits through 256 different amplitude and phase signal points. A single modulation can transmit 8 bits of data.
- Spectral efficiency: The number of data bits that can be transmitted per unit time and unit frequency band.
- SINR: The ratio of desired-signal power to the sum of all other interference-signal power and noise power.
- FWA: Wireless communications performed between fixed base stations and terminals situated outdoors.
- CQI: An index of reception quality measured at the mobile station, expressing propagation conditions on the downlink.
- PT-RS: A reference signal that aims to estimate phase noise in high-frequency bands.
- FR1: Frequency bands specified in 3GPP ranging from 450 to 6,000 MHz.
- WRC: A conference that reviews, and if necessary, revises Radio Regulations, the international treaty governing the use of radio-frequency spectrum, and the orbits of geostationary and non-geostationary satellites. The conference normally meets once every three to four years, and is attended by administrations, ITU registered corporations and related organizations.
- IEEE 802.11ad/ay: A wireless LAN standard using the 60 GHz band.
- Unlicensed bands: Frequency bands that do not require government licensing, and whose use is not limited to a particular telecommunications operator.
- Multi-SIM UE: A UE that can use multiple SIMs on one unit.
- QoE: Service quality derived from the user experience.
- VR: Technology that gives the user the illusion of being in a virtual world.
- Network slicing: One format for achieving next-generation networks in the 5G era. Architecture that optimally divides the core network in units of services corresponding to use cases, business models, etc.
- RAN: A network consisting of radio base stations and radio-circuit control equipment situated between the core network and mobile terminals.
- SON: A network installed with functions to self-configure and self-optimize its parameters.
- MDT: A technology standardized by the 3GPP for gathering QoE information. Terminals send information to the network regarding incidents such as interruption of communication or failed handover as they occur, such as location and cause of the incident.
- PCI: A physical-cell identifier. NR supports a total of 1,008 PCIs that can be reused across the network.
- HO: A communications technology for switching between communication cells or base stations while maintaining communications between the terminal and network.
- EN-DC: An architecture for 5G non-standalone operations, using 5G as another radio resource in addition to the RRC connection over 4G radio.
- CHO: One method for executing an HO in which the network, instead of giving instructions at the time of an HO, notifies the UE beforehand of the switching destination and switching conditions.
- DAPS: A function for shortening UE interruption time during an HO by simultaneously using both pre-HO/post-HO communications paths in a transient manner.
- HPUE: Generic term for a UE that can transmit with greater power than an ordinary UE.
- Handheld UE: A device that the user holds in one's hands during use such as the so-called smartphone.
- PC3: 3GPP standards provide several types of power classes such as maximum over-the-air power.
- NR-CA: A technology that achieves higher transmission speeds through band expansion by simultaneously transmitting and receiving data using multiple NR carriers while maintaining backward compatibility.
- SUL: Separate from the normally used UL/DL pair, a UL in a different frequency band used in a supplementary manner for maintaining UL coverage. It cannot be used simultaneously with the normally used UL.
- TDD: A signal transmission system that allocates different time slots to UL/DL transmissions using the same carrier frequency and frequency band.
- FDD: A single transmission system using different carrier frequencies and frequency bands in the UL and DL.
- n77: A TDD frequency band defined for NR (3,300 to 4,200 MHz).
- Duty cycle: The UL transmission period within a given period.
- RF: Refers to the radio frequency analog circuit.
- Tx antenna switching: Technology for dynamically switching antennas used for signal transmission by a UE. Selecting antennas that enable higher quality signal transmission is expected to improve communications quality and throughput.
- RF chain: Refers to the entire analog signal processing section including antennas, up-converter/down-converter, oscillator, and amplifiers.
- RF specifications: Radio-related characteristics such as spurious emissions and receiver sensitivity.
- RRM: A generic term applied to control functions for appropriately managing limited radio resources, making smooth connections between terminals and base stations, etc.
- SRS: A reference signal for measuring UL channel quality and reception timing on the base-station side.
- MG: Refers to the interval established for measuring frequencies other than the frequency used in communications.
- BWP: A partial band used when it is necessary to use only a bandwidth narrower than the carrier's maximum bandwidth. The BWP information required for communications (bandwidth, frequency position, subcarrier interval) can be set in each UE.
- HST: Special specifications have been prepared for high-speed mobile environments that are generally called HST scenarios.
- UE demodulation: Generic term for receive-signal processing at the UE.
- Repeater: Relay equipment on the physical layer to amplify a DL receive signal from a base station and transmit it to a mobile station.
- Unlicensed band: A frequency band that does not require government licensing, and whose use is not limited to a particular telecommunications operator.
- MIMO layers: The number of signals (data streams) simultaneously transmitted on the same radio resources with different antennas using spatial multiplexing.
- Modulation level: The number of signal phase points in data modulation. This number is 4 in Quadrature Phase Shift Keying (QPSK) and 16 in 16 Quadrature Amplitude Modulation (16QAM).
- Duplex mode: A communications scheme where transmission can be performed in the UL and DL simultaneously. Generally implemented as Frequency Division Duplex (FDD) or Time Division Duplex (TDD).
- RAT: A radio access technology such as NR, LTE, W-CDMA, and GSM.
- E-CID: A positioning technology for estimating a UE's position using the cell ID received from the base station, the received strength and received quality of the reference signal transmitted from that base station, the Round-Trip-Time (RTT) between the base station and UE, etc.
- DL-TDOA: A positioning technology that estimates a UE's position by simultaneously transmitting DL reference signals to that UE from multiple base stations and using differences in the arrival times of those signals and each base station's coordinates.
- UL-TDOA: A positioning technology that estimates a UE's position by transmitting a UL reference signal from that UE to multiple surrounding base stations and using differences in the arrival times of those signals and each base station's coordinates.
- Multi-RTT: A positioning technology that estimates a UE's position based on the RTTs between that UE and multiple base stations and on each base station's coordinates.
- UL-AoA: A positioning technology that estimates a UE's position by transmitting a UL reference signal from that UE to the base station and using the horizontal and vertical angles of arrival.
- DL-AoD: A positioning technology that estimates a UE's position by transmitting a DL reference signal from the base station to that UE and using the index and received strength of the received beam and the beam's horizontal and vertical angles of departure on the base-station side.
- HARQ: A technology that combines Automatic Repeat reQuest (ARQ) and error correcting codes to improve error-correcting performance on transmission and reduce the number of retransmissions.
- RACH: A common UL channel that is used for transmitting control data and user data. Each user independently and randomly transmits signals enabling multiple users to share a single channel.
- RRC_INACTIVE: A terminal state in RRC where the terminal does not have cell level identification within the base station, and where the context of the terminal is held in the base station and the core network.
- Relay: Technology for relaying and transmitting communications.
- Sidelink relay: Technology for extending coverage through relaying in sidelink communications.
This article provided an overview of advanced 5G ...
This article provided an overview of advanced 5G radio technologies specified in 3GPP Rel-17 specifications. Details of advanced technologies for mobile broadband, industry creation, and co-creation of solutions are provided in other articles of this issue .
At 3GPP, work on Rel-18 specifications as the initial release of 5G-Advanced began in December 2021 . NTT DOCOMO is a firm promoter of 5G standardization at 3GPP and intends to contribute to its further development going forward.
-  Y. Matsumura et al.: “Enhanced Mobile Broadband Technologies in 3GPP Release 17,” NTT DOCOMO Technical Journal, Vol. 24, No. 3, 2023.
-  S. Kumagai et al.: “Advanced Technologies for Industry Creation and Solution Co-creation in 3GPP Release 17,” NTT DOCOMO Technical Journal, Vol. 24, No. 3, 2023.
-  H. Harada et al.: “5G and 5G-Advanced Standardization Trends,” NTT DOCOMO Technical Journal, Vol. 24, No. 3, 2023.
-  Y. Matsumura et al.: “Enhanced Mobile Broadband Technologies in 3GPP Release 17,” NTT DOCOMO Technical Journal, Vol. 24, No. 3, 2023.