5G-Advanced Store and Forward (S&F): Enabling Resilient IoT Communications via Satellite

Introduction

As the deployment of 5G networks continues to expand globally, the industry is already looking ahead to enhance capabilities through 5G-Advanced features. Among these innovations is the "Store and Forward" (S&F) functionality for Non-Terrestrial Networks (NTN), which represents a significant advancement for IoT applications utilizing satellite connectivity. This feature, specified in 3GPP Release 19, addresses one of the key challenges in satellite communications: maintaining service continuity during intermittent feeder link connectivity.

What is Store and Forward?

Store and Forward (S&F) satellite operation is designed to provide communication services for User Equipment (UE) under satellite coverage without requiring a simultaneous active feeder link connection to the ground segment. This capability is particularly relevant for delay-tolerant IoT services utilizing Non-Geostationary Orbit (NGSO) satellites.

In simple terms, S&F enables satellites to:

• Collect data from IoT devices when they're in range
• Store this data onboard the satellite
• Forward the data to ground stations only when a connection becomes available

This approach fundamentally differs from traditional satellite operations, which require end-to-end connectivity at the moment of transmission.

Source: 3GPP TR 22.865: Technical Specification Group Services and System Aspects; Study on satellite access Phase 3;

Normal Operation vs. Store and Forward

To understand the significance of S&F, it's important to contrast it with the "normal/default satellite operation" mode:

Normal/Default Satellite Operation

In the traditional model, signalling and data traffic exchange between a UE with satellite access and the ground network requires both service and feeder links to be active simultaneously. This creates a continuous end-to-end connectivity path between the UE, satellite, and ground network.

Store and Forward Operation

Under S&F operation, the end-to-end exchange of signalling/data traffic is handled as a two-step process that doesn't need to occur concurrently:

• Step A: Signalling/data exchange between the UE and satellite takes place even without the satellite being connected to the ground network. The satellite operates the service link without an active feeder link connection, collecting and storing data from IoT devices.
• Step B: Later, when connectivity between the satellite and ground network is established, the stored communications are transmitted to the ground network.

This approach bears similarities to existing store-and-forward services like SMS, where end-to-end connectivity between endpoints isn't required simultaneously.

Source: Ericsson Blog

Technical Requirements for Store and Forward

The implementation of S&F relies heavily on regenerative satellite payloads, as opposed to transparent payloads. Here's why this distinction matters:

Regenerative Payload Advantages

A regenerative payload with an onboard gNB (next-generation NodeB) offers several critical capabilities:

• Onboard Processing: The ability to process and store data directly on the satellite
• Reduced Dependency: Less reliance on continuous ground segment connectivity
• Enhanced Resilience: The NTN can function even if the feeder link is temporarily severed
• Performance Improvements: Significant reductions in roundtrip time for all procedures between the gNB and UE

For S&F functionality, all or part of the core network functions must be placed on the satellite together with the gNB. This architectural change enables a new level of autonomous operation for satellite networks.

Applications for IoT

The Store and Forward capability is especially suited for delay-tolerant or non-real-time IoT applications. Examples include:

• Environmental Monitoring: Collecting sensor data from remote locations
• Asset Tracking: Monitoring the status of assets in transit through areas with limited ground infrastructure
• Agricultural Sensing: Gathering data from widely distributed sensors in rural areas
• Maritime and Offshore IoT: Supporting connected devices at sea where direct connectivity to ground networks is inconsistent

These use cases benefit from S&F's ability to ensure data is eventually delivered without requiring constant connectivity, which is particularly valuable for battery-powered IoT devices that need to conserve energy.

Relationship to Delay-Tolerant Networking

The concept of Store and Forward is well-established in delay-tolerant networking (DTN) and disruption-tolerant networking domains. These networking paradigms are designed to work in challenged environments where conventional protocols may fail due to long delays or frequent disruptions.

In the 3GPP context, S&F can be compared to SMS service, which doesn't require end-to-end connectivity between endpoints but only between the endpoints and the Short Message Service Centre (SMSC), which acts as an intermediate node handling storage and forwarding.

Future Implications

The introduction of S&F functionality represents an important step toward what Ericsson has called "data centers in the sky." By placing not just radio access network functions but also core network capabilities in space, we're moving toward satellite networks that can operate with greater autonomy and resilience.

This development also aligns with broader industry efforts to create truly global coverage through integrated ground and space networks. Combined with inter-satellite links (ISL), S&F enables more flexible and resilient network architectures that can maintain service even when individual links are unavailable.

Conclusion

Store and Forward represents a significant advancement in 5G-Advanced satellite communications, particularly for IoT applications. By decoupling the timing requirements between service link and feeder link communications, S&F enables more resilient, energy-efficient, and cost-effective deployment of IoT devices in remote or challenging environments.

As 3GPP Release 19 specifications continue to develop, we can expect to see this capability integrated into commercial satellite IoT offerings, expanding the reach of 5G networks to truly global coverage. While initially targeted at IoT applications, the architectural principles of S&F could eventually extend to other services, bringing us closer to ubiquitous connectivity across terrestrial and non-terrestrial networks.

Related Posts

• The 3G4G Blog: Tutorial Session on Non-Terrestrial Networks (NTNs) and 3GPP Standards from 5G to 6G
• Connectivity Technology Blog: Tutorial Session on Current Trends and Key Challenges of Satellite communications
• Free 6G Training: ATIS Webinar on 'Introduction to 3GPP Release 19 and 6G Planning'
• The 3G4G Blog: Low Latency Power Saving with Low Power-Wake Up Signal/Receiver (LP-WUS/LP-WUR)
• The 3G4G Blog: Small Data Transmission (SDT) in LTE and 5G NR
• The 3G4G Blog: 3GPP TSG RAN and TSG SA Release-19 Workshop Summary
• The 3G4G Blog: Are there 50 Billion IoT Devices yet?
• 3G4G: An Quick Introduction to 3GPP 

Low Latency Power Saving with Low Power-Wake Up Signal/Receiver (LP-WUS/LP-WUR)

Power-saving methodologies have been integral to all generations of 3GPP technologies, aimed at reducing the power consumption of user equipment (UEs) and other battery-dependent devices. Some of the stringent requirements of 5G, such as achieving a 10-year battery life for certain IoT devices, have necessitated further optimisation of power consumption. To address this, 3GPP Release 16 introduced the Wake-Up Signal (WUS) power-saving mechanism, designed to significantly reduce energy usage in UEs. For a detailed technical explanation, ShareTechnote provides an excellent overview.

The concept of wake-up radios has been explored for over a decade. In a 2017 blog post, Ericsson highlighted how researchers had been working on designing wake-up radios and receivers, initially aimed at IEEE 802.11 (Wi-Fi) technologies. This idea later gained traction in 3GPP discussions, culminating in a study conducted during Release 18. The findings are comprehensively documented in 3GPP TR 38.869: Study on low-power wake-up signal and receiver for NR (Release 18).

Quoting from the introduction of 3GPP 38.869:

5G systems are designed and developed targeting for both mobile telephony and vertical use cases. Besides latency, reliability, and availability, UE energy efficiency is also critical to 5G. Currently, 5G devices may have to be recharged per week or day, depending on individual's usage time. In general, 5G devices consume tens of milliwatts in RRC idle/inactive state and hundreds of milliwatts in RRC connected state. Designs to prolong battery life is a necessity for improving energy efficiency as well as for better user experience. 

Energy efficiency is even more critical for UEs without a continuous energy source, e.g., UEs using small rechargeable and single coin cell batteries. Among vertical use cases, sensors and actuators are deployed extensively for monitoring, measuring, charging, etc. Generally, their batteries are not rechargeable and expected to last at least few years as described in TR 38.875. Wearables include smart watches, rings, eHealth related devices, and medical monitoring devices. With typical battery capacity, it is challenging to sustain up to 1-2 weeks as required. 

The power consumption depends on the configured length of wake-up periods, e.g., paging cycle. To meet the battery life requirements above, eDRX cycle with large value is expected to be used, resulting in high latency, which is not suitable for such services with requirements of both long battery life and low latency. For example, in fire detection and extinguishment use case, fire shutters shall be closed and fire sprinklers shall be turned on by the actuators within 1 to 2 seconds from the time the fire is detected by sensors, long eDRX cycle cannot meet the delay requirements. eDRX is apparently not suitable for latency-critical use cases. Thus, the intention is to study ultra-low power mechanism that can support low latency in Rel-18, e.g. lower than eDRX latency.

Currently, UEs need to periodically wake up once per DRX cycle, which dominates the power consumption in periods with no signalling or data traffic. If UEs are able to wake up only when they are triggered, e.g., paging, power consumption could be dramatically reduced. This can be achieved by using a wake-up signal to trigger the main radio and a separate receiver which has the ability to monitor wake-up signal with ultra-low power consumption. Main radio works for data transmission and reception, which can be turned off or set to deep sleep unless it is turned on.

The power consumption for monitoring wake-up signal depends on the wake-up signal design and the hardware module of the wake-up receiver used for signal detecting and processing. 

The study should primarily target low-power WUS/WUR for power-sensitive, small form-factor devices including IoT use cases (such as industrial sensors, controllers) and wearables. Other use cases are not precluded, e.g.XR/smart glasses, smart phones. 

As opposed to the work on UE power savings in previous releases, this study will not require existing signals to be used as WUS. All WUS solutions identified shall be able to operate in a cell supporting legacy UEs. Solutions should target substantial gains compared to the existing Rel-15/16/17 UE power saving mechanisms. Other aspects such as detection performance, coverage, UE complexity, should be covered by the evaluation.

The Bridge Toward 6G: 5G-Advanced Evolution in 3GPP Release 19 by Xingqin Lin, @NVIDIA - https://t.co/O1d8jnB9MY#Free5Gtraining #3G4G5G #3GPP #5G #5GAdvanced #6G #AIML #NGRAN #XR #UAV #LPWUS #LPWUR #HighPerforming #LTM #SBFD #Femtocell #NTN #WAB #Relay pic.twitter.com/aSC9FuruC7

— Free 5G Training (@5Gtraining) January 2, 2024

Qualcomm's blog post looking at 'How will wireless innovations foster a greener, more sustainable future?' is also worth reading on this topic.

Related Posts: 

• The 3G4G Blog: 3GPP TSG RAN and TSG SA Release-19 Workshop Summary
• The 3G4G Blog: ETSI's Summit on Sustainability: ICT Standards for a Greener World
• The 3G4G Blog: Four Ways 5G Can Improve the Battery Life of User Equipment (UE)
• The 3G4G Blog: Energy Consumption in Mobile Networks and RAN Power Saving Schemes
• The 3G4G Blog: Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)
• The 3G4G Blog: Mobile Initiated Connection Only (MICO) mode in 5G System 

3GPP TSG RAN and TSG SA Release-19 Workshop Summary

3GPP recently announced the milestone of reaching 100th plenaries of the three Technical Specification Groups (TSGs) in 3GPP which took place in Taipei last week. If you are unsure what TSGs are, we recently made a tutorial of 3GPP, available here.

During the plenary TSG SA and TSG RAN held workshops on Release 19. The top level link for RAN workshop is here while that for SA is here. SA also has HTML link of the documents here.

The slide above is from the RAN chair's summary provides list of topics that were discussed. The following is the executive summary from the draft workshop report:

The 3GPP TSG RAN Rel-19 face-to-face workshop was held June 15 - June 16, 2023 in Taipei hosted by TAICS (Taiwan Association of Information and Communication Standards) and MediaTek with 174 participants (see Annex A) and 491 Tdocs (see Annex B). A GotoWebinar conference call was carried out during the whole workshop to display discussed documents and to allow listen & talk access for people joining remotely.

The workshop agenda was provided in RWS-230001 and split into 3 main parts:

• High-level overview proposals for Rel-19: 18 Tdocs handled, 46 not treated, 1 in the end endorsed (RP-230488)
• Specific RAN1/2/3-led Rel-19 topics: 29 Tdocs handled, 369 not treated
• RAN4-led Rel-19 topics (for information only): 20 not treated

Note: High-level overview proposals for Rel-19 and RAN4-led Rel-19 topics had the restriction of maximum one contribution led per company.

Some guidance about the workshop was provided on the RAN email reflector on 28.04.23 and 02.05.23.

Time plan versions of the workshop were provided on 02.05.23, 11.06.23 and on 15.06.23.

Workshop inputs were possible from 28.04.23 until the submission deadline 31.05.23 9pm UTC.

(Late Tdoc requests as well as revisions of Tdocs after the Tdoc request deadline 30.05.23 9pm UTC were avoided in order to not complicate the Tdoc handling, like quotas for AI 4 and 6, preparations of the workshop in parallel to RAN #100 and preparations of the summary etc.)

Originally, Thursday 15.06.23 and Friday 16.06.23 morning were planned for presentations of a limited set of 47 workshop contributions (selected by the RAN chair trying to achieve a fair coverage of the topics and interests and taking into account that there were many more inputs that can be handled in a 2 days workshop) and Friday afternoon was reserved for the discussion of a summary of the RAN chair (in RWS-230488). Note: Since the presentation part went faster and the Friday lunch break was skipped, the workshop ended on Friday afternoon earlier than originally planned.

Finally, the RAN chair's summary in RWS-230488 was endorsed indicating the motivations and handling of the workshop, the Rel-19 timeline and load plans and the management and categorization of topics.

TSG SA didn't have a summary slide but SWS-230002, output of drafting session on Consolidated SA WG2 Rel-19 Work, listed the following topics:

• Satellite Architecure Enhancements
• XRM Enhancements and Metaverse
• AI/ML enhancements
• Multi-access (Dual 3GPP + ATSSS Enh)
• Integrated Sensing and Communication
• Ambient IoT
• Energy Efficiency / Energy Saving as a Service
• IMS and NG_RTC enhancements
• Edge Computing Enhancements
• Proximity Services enhancements 
• TSC/URLLC/TRS enhancements 
• Network Sharing 
• User identities + identification of device behind RG/AP
• 5G Femto 
• UAS enhancements 
• VMR Enhancements 
• UPEAS Enhancements 

3GPP Rel-19 candidates by Nokia#Free5Gtraining #3G4G5G #Nokia #5G #5GAdvanced #5GNetworks #3GPP #Release19 #NTN #Sidelink #Femto #WUS #IoT #Sidelink #Positioning #XR #AIML #MIMO #Beamforming #Enhancements #AIML #Duplex #Slicing #EnergyEfficiency pic.twitter.com/t1ehBYgCVM

— Free 5G Training (@5Gtraining) June 12, 2023

Fattesinh Deshmukh has a summary of 3GPP RAN Rel-19 Workshop on LinkedIn here. Nokia has their summary of the workshop here.

Related Posts: 

• 3G4G: A Quick Introduction to 3GPP
• The 3G4G Blog: 3GPP's 5G-Advanced Workshop Summary
• The 3G4G Blog: ATIS Webinar on "3GPP Release 18 Overview: A World of 5G-Advanced"
• The 3G4G Blog: '5G RAN Release 18 for Industry Verticals' Webinar Highlights 

ATIS Webinar on "3GPP Release 18 Overview: A World of 5G-Advanced"

Yesterday, ATIS, one of the seven 3GPP Organizational Partner (OP), delivered on online webinar on 3GPP Release 18 Overview: The World of 5G-Advanced. A summary of the webinar according to ATIS as follows:

As the first release of 5G-Advanced, Release 18 has been progressing well despite the challenges in fully resuming 3GPP face-to-face meetings in 2022.

In this webinar, ATIS provides a high-level summary of 3GPP Release 18: the confirmed Rel-18 timeline, status for the ongoing study and work items, and the newly converted work items from the completed study items. We also give a brief introduction of the preparation for Release 19 aiming for approval of the package of projects in December 2023.

Distinguished speakers included:

• Wanshi Chen (Qualcomm, Chair of 3GPP RAN Plenary) will provide a view on radio interface and RAN system aspects.
• Puneet Jain (Intel, Chair of 3GPP System Architecture Group – SA2) will look at whole system capabilities and network aspects.
• Moderator: Iain Sharp, Principal Technologist, ATIS

The recording of the webinar is embedded below and slides available here.

Just a reminder, 5G covers Release 15, 16 and 17. 5G-Advanced is Release-18 onwards. Ideally, 18, 18 and 20. 6G should start with Release 21. Based on the current industry adoption of 5G, there is no reason to push the next generation on the operators before it's mature and everyone is ready to take it onboard.

I have seen a few vendors & operators now referring to 3GPP Release-17 as 5G-Advanced but the 3GPP definition is 5G-Advanced is Release-18. More details on this old blog post here - https://t.co/zY3thY3sAe pic.twitter.com/qO6d1YpO1e

— Zahid Ghadialy (@zahidtg) January 12, 2023

Related Posts:

• The 3G4G Blog: ATIS Webinar on '5G Standards Development Update in 3GPP Release 17 and 18'
• The 3G4G Blog: ATIS Webinar on '5G Standards Developments in 3GPP Release 16 and Beyond'
• The 3G4G Blog: 3GPP Release-18 Work Moves Into Focus as Release-17 Reaches Maturity
• The 3G4G Blog: 3GPP Presentations from CEATEC Japan 2021
• The 3G4G Blog: '5G RAN Release 18 for Industry Verticals' Webinar Highlights
• Free 6G Training: ATIS’ Next G Alliance (NGA) Releases Two New Reports
• Free 6G Training: Next G Alliance's Report on 6G Applications and Use Cases
• The 3G4G Blog: DCCA Features and Enhancements in 5G New Radio
• The 3G4G Blog: AI/ML Enhancements in 5G-Advanced for Intelligent Network Automation 

ATIS Webinar on '5G Standards Development Update in 3GPP Release 17 and 18'

Our blog post on ATIS Release-16 webinar has been one of the popular posts so it's no brainer that people will surely find this Release 17/18 update useful as well. 

The moderator for this webinar was Iain Sharp, Principal Technologist at ATIS. The following were the speakers and the topics they spoke on:

• Services: Greg Schumacher, Global Standards, T-Mobile USA
• Systems Architecture and Core Networks: Puneet Jain, Principal Engineer and Director of Technical Standards at Intel Corporation, and 3GPP SA2 Chairman
• Radio Access Network: Wanshi Chen, Senior Director,Technology at Qualcomm, and 3GPP RAN Chairman

Here is a summary of the webinar:

In Release 17, 3GPP delivered important updates to 5G specifications to broaden their range of commercial applications and improve the efficiency of networks. 3GPP is now starting standardization of Release 18. This webinar provides an up-to-date view of the completed 3GPP Release 17 work with a particular focus on how the work is expanding capabilities of 5G and enhancing the technical performance of the mobile system.

The webinar will cover:

• The status of 3GPP's work and the organization's roadmap for the future
• The main themes the delivered Release 17 features in 3GPP specifications
• How enhancements to 5G are helping the 5G market proposition (e.g., through new service opportunities, or enhanced efficiency of 5G networks)

The webinar will give a technical overview of 3GPP's Release 17 content and its benefits to 5G networks. It is suitable for people in technical roles and technical executives who want to understand the current state of 5G standardization.

The video is embedded below and the slides are available here:

Glad to see that 3GPP Rel-19 work has already started as can be seen in the roadmap below.

(click to enlarge)

Related Posts: 

• The 3G4G Blog: 3GPP Release-17 5G NR Reaches Completion
• The 3G4G Blog: 3GPP Release-18 Work Moves Into Focus as Release-17 Reaches Maturity
• The 3G4G Blog: ATIS Webinar on '5G Standards Developments in 3GPP Release 16 and Beyond'
• Free 6G Training: Transatlantic perspectives on 6G Vision, Roadmap and Development Model