Softbank Demoed Drone Wireless Relay System

Back in 2016, I was involved with doing testing using drones and Helikite with the UK operator EE. You can read more about that here. Since then, many different operators have tested the use of drones mainly for disaster recovery kinds of scenarios. The Japanese operator Softbank recently tried the same.

The press release from them provided the following details:

When typhoons, earthquakes, landslides and other types of natural disasters strike, mobile phones serve as an important lifeline for people to get information and to stay in touch with their family, friends and colleagues. SoftBank Corp. recognizes the importance of restoring communications lifelines quickly, and is engaged in developing and building systems for disaster preparedness.

One such service restoration initiative SoftBank has been working on is the “Drone Wireless Relay System.” On August 31, 2020, SoftBank demonstrated the solution for the press at Katsuma Radio Control Airstrip in Ichihara City, Chiba Prefecture, just east of Tokyo.

Thanks to their portability and ease-of-use, drone-based wireless relay base stations are showing promise as a means of providing connectivity when outages occur in the wake of natural disasters. SoftBank has been working with theTokyo Institute of Technology (Tokyo Tech)’s Department of Electrical and Electronic Engineering since 2019 to conduct research on drone-based wireless relay systems that use a wired power feed.

SoftBank’s drone-based relay base station rises to an altitude of 100 meters, covering a 10km radius. The drone can be transported in a small vehicle and is easy to set up. Compared to another SoftBank network recovery solution, the moored-balloon relay system, the time to deployment is much shorter. In addition, the wired power supply allows the drone to fly continuously for three days or longer, making it suitable for operations over the short- to medium-term.

The moored-balloon wireless relay system is capable of lifting wireless relay equipment to an altitude of 100 meters, covering a five-kilometer radius in open terrain. SoftBank 3G (mobile phone) (2.1 GHz band) voice communications and packet transmissions (email, Internet, etc.) can be used within the coverage area. We are also conducting trial tests of a new moored-balloon wireless relay system for SoftBank 4G LTE that can be deployable from ships, as part of our efforts to continuously improve this system.

A video from the recent drone event is as follows:

Related Posts:

• Telecoms Infrastructure Blog: Drones for Tower Inspections and Optimization
• Telecoms Infrastructure Blog: Dronecell - Turkcell's Flying Base Station
• Telecoms Infrastructure Blog: Turin will be the first European city with a 'drone ready' 5G network
• Telecoms Infrastructure Blog: Autonomous Relaying Drones
• Telecoms Infrastructure Blog: Flying Small Cells are here...
• Telecoms Infrastructure Blog: Drones, More Drones & Droneway

Small Cells Deployment Stories

I recently got an opportunity to hear about the small cell deployment studies, organised as SCWS pre-conference workshop. The combined slides from the presentation are embedded below and available to download from Small Cell Forum page here.

Open, Closed and Hybrid Access Small Cells

A question that often keeps cropping up regularly is regarding the open access and closed access small cells. Before we look at the explanation of these cells, lets see the different types of cells (from 3GPP TS 36.304) in brief:

Acceptable cell: An "acceptable cell" is a cell on which the UE may camp to obtain limited service (originate emergency calls and receive ETWS and CMAS notifications).

Suitable cell: A "suitable cell" is a cell on which the UE may camp on to obtain normal service. It is mandatory for the UE to have a USIM card belonging to the operator to which this cell belongs.

Barred cell: A cell is "barred" if it is so indicated in the system information. Its not available for use by anyone.

Reserved cell: A cell is reserved if it is so indicated in system information. It is reserved for operator use only.

Restricted Cell: A cell on which camping is allowed, but access attempts are disallowed for UEs whose access classes are indicated as barred.

Camping on the cell: With the cell selection, the UE searches for a suitable cell of the selected PLMN and chooses that cell to provide available services, further the UE shall tune to its control channel. This choosing is known as "camping on the cell".

To keep the discussion simple, I have ignored that some UE's may belong to MVNO and the PLMN Id of the operator would be stored as Equivalent PLMN Id.

Now lets look at a simple explanation of the different types of small cells.

Open Access: All (suitable) cells are open access by default. This means that they can be accessed by any device belonging to the operator whom the cell belongs to. Some people also refer to these cells as Open Subscriber Group (OSG) cells.

Closed Access: A (suitable) cell is closed when only certain devices can camp on them. These devices form a part of whitelist stored in a database to allow camping on the cell. Devices that are not part of the whitelist are not allowed to camp on this cell, even though they belong to the same operator and this cell is a suitable cell. The devices are said to belong to ‘Closed Subscriber Group’ (CSG). The cell is said to be a CSG cell as its transmitting CSG Indication set to 'true' and the CSG Identity.

Residential Femtocells are generally Closed Access but there are exceptions. Softbank, Japan for example gives open access Femtocells that can also provide coverage to users nearby. Another example is the operator Free in France that also offers similar open access Femtocells.

Hybrid Access: A (suitable) cell can also be hybrid access, thereby allowing all devices that either belong to a CSG or non-CSG to camp onto it. A hybrid cell may offer prioritised and/or additional services to the users that belongs to the CSG it is a part of.

I am not aware of any Hybrid Access Small Cells deployment to date. Please feel free to correct me.