An Introduction of DIGITAL RELAY RADIO (DRR): This is a comprehensive and distinct wireless communication system, functioning in a non-conventional manner that surpasses existing VHF/UHF radio communication systems. It represents a step beyond conventional radios due to its capability to establish a robust radio link even without Line of Sight (LoS), setting it apart in point-to-point communication scenarios. 

In the illustrative scenario, conventional walkies CW-1 and CW-2 attempting to communicate between A-Zone and B-Zone are hindered by obstructions in the Line of Sight (indicated by the Red Line). On the other hand, DRR walkies DW-1 in A-Zone can effortlessly communicate with DW-2 in B-Zone using a third walkie, DW-R. This intermediate walkie relays the signal from DW-1 and transmits it to DW-2 with a clear LoS (depicted by the Green Line).

Main System Components of DRR Solution: The key components of the DRR Solution encompass two types of system elements. The first is the Handheld Walkie-talkie, Model: G5Ui, and the second is the tower-mountable DRR Extender, Model: G10Ui. The RF power output of this extender is 10 watts, surpassing the 5-watt output of the G5Ui Handheld Walkie. Due to its higher throughput, the G10Ui functions akin to a base station in conventional radio systems. It is recommended to install the G10Ui directly on towers or high-altitude locations to extend its communication range.

Application and demonstration of DRR system at CCL, Ranchi : This demonstration was conducted from 28/01/2021 to 30/01/2021 for the Karma Project and Topa Project in the Kuju area, in response to specific requirements from CCL management.

Requirement: At the open-cast coal mines of Karma and Topa Projects, a fundamental necessity is communication between the Project Officer, Pit Office, and Pump House located at the mine’s lower levels. The Project Officer needs real-time information about the mine’s activities. Additionally, workers at the lower levels occasionally require technical assistance or need to convey issues to surface-level personnel, a process that used to involve traveling to the surface for every minor requirement, which is neither efficient nor safe in terms of production. The senior officials also require the capability to urgently communicate with all workers from their offices. Thus, the dual objectives are ensuring effective communication and remote addressing.

Demonstration performed for two projects, 1. Karma Project, 2 Topa Projects:

About Karma Project: This is an open-cast mine located in the Kuju area, where the Project Officer (PO) aims to establish communication with various key areas, including the Pit Office, Viewpoint, inclined sections throughout the mine, the pump house area at the mine’s bottom level, and the check post area. The primary challenge arises due to the presence of a substantial-high dumping area between the mine site and the PO’s office. Extensive testing has been conducted from each of the designated node points mentioned above. The testing yielded successful results without the implementation of the DRR extender. However, it should be noted that optimal performance could be achieved by utilizing the DRR Handheld model G5Ui at all the locations specified in the table below. Additionally, for further enhancement of performance, we have recommended the utilization of DRR with high-gain antennas at all nodal points.

S. No. From Location To Location Dist. (km) Remarks
1 Projects office Check Post 1.2 Testing successful
2 Projects office Pit Office 1.0 Testing successful
3 Projects office Crusher via Viewpoint 1.0 Testing successful
4 Projects office Pump House 1.4 Testing successful
5 Pump House Crusher point 0.5 Testing successful
6 Crusher Point Pit Office 0.4 Testing successful
7 Pit Office Check post 0.35 Testing successful

About Topa Project: They require communication between the PO office, Pit office, railway siding, weighbridge, throughout the mine’s inclined sections, and the pump house area at the mine’s bottom level. The primary challenge stems from the presence of high dumping areas, and the effectiveness of line-of-sight communication is limited. Thorough testing has been conducted from each designated node point as mentioned above.

The testing yielded successful results when utilizing the DRR extender with a high-gain antenna placed between handheld mesh radios. In cases where the DRR box was not used, the mesh radios managed to communicate with each other up to the Pit office from the Weigh Bridge, albeit with slight noise and voice disruptions. To achieve enhanced performance, we incorporated the DRR extender with a high-gain antenna. For most of the node points, there is the provision to provide 220V AC power to the DRR. In cases where 220V AC power is unavailable, we recommended the use of solar panels. Notably, a significant challenge arises in establishing communication from the PO office, which is located in a crowded area. Thus, it is advisable to install a DRR between the Pit office and PO office.

A summary of the distances between each node point, up to which successful communication has been achieved, is as follows:

S. No. From Location To Location Dist. (km) Remarks
1 Railway Siding Weigh Bridge          1.0

This site requires min. 4 nos. DRR Extender as per testing & survey (may vary as site requirement).

1. Railway siding,

2. Siding area;

3. Towards PO office from Pit office,

4. Towards mines incline.

2 Siding Area Pit Office          1.0
3 Railway Siding Pit office          2.0
4 Pit Office Testing Point towards Excavation Area          0.5
5 Pit Office Towards P.O office          0.3
6 Railway Siding Towards P.O office          1.3



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