Definition
Dense Network (Dense Network/UDN Ultra Dense Network) increases network capacity and coverage by increasing the number of cells per unit area. It is a key technology for 5G to meet the high capacity requirements of eMBB. Macro base stations, small base stations, DAS, etc., form a heterogeneous network (HetNet), with cell radius reduced to several tens of meters. Dense network deployment requires interference coordination (ICIC, eICIC), SON self-organizing network, handover optimization and other technologies to achieve efficient deployment and operation.
Technical Challenges and Solutions
- Interference Management: Dense cells result in increased co-channel interference, which requires eICIC (almost blank subframe), CoMP, beamforming and other interference suppression methods
- Backhaul Cost: A large number of small base stations results in high cost for front-haul/backhaul fiber or wireless links; C-RAN centralization and eCPRI compression can alleviate this
- Mobility Management: Smaller cells lead to frequent handovers; it is necessary to optimize handover parameters and introduce light connection states like RRC_INACTIVE to reduce signaling
Capacity and Coverage Gain
Dense networking shortens the spectrum reuse distance, increasing unit area capacity by several to tens of times; edge users are closer to base stations, reducing path loss, improving coverage and rates. For IoT devices in high-density scenarios such as stadiums and commercial areas, dense networking can significantly improve access success rates and uplink speed.
Typical Use Cases
High-traffic areas, stadiums, commercial areas, subway stations, airports, industrial IoT dense deployments, and other high-capacity scenarios. SimtoLink's IoT SIM cards can enjoy more stable connectivity in dense networking environments.
Dense networking increases network capacity in high-traffic areas, allowing IoT devices to obtain more stable connections in high-density scenarios such as stadiums and commercial areas. SimtoLink's IoT SIM cards support dense networking environments, and the SimtoLink cloud platform can analyze device connectivity quality in high-traffic areas, providing network planning and optimization recommendations for large-scale IoT deployments.
Shorten the site spacing and the handover zones stack on each other
Dense networking pulls the cell radius down to a few dozen meters, and the usable areas of two cells overlap across a large area. In the overlap the device hears two cells at similar levels, and measurement events trigger more easily. If the handover threshold and hysteresis are still the macro-site set, the device hands back and forth between neighboring small cells, and signaling overhead exceeds the service itself. To tell whether density brought capacity or oscillation, see whether handover count rises with walking speed while throughput does not. Adding sites without tightening the handover zone makes IoT devices in the hotspot less stable than they were under the macro site.
A stationary device can sit on a handover zone too. A card reader by a shelf or a gate, mounted exactly on the equal-level line of two small cells, will reselect often in idle mode and hand over often while connected. Moving it a few meters is often more effective than replacing the module. Acceptance should record the level difference to neighbors, not only the absolute value of the strongest cell.
Backhaul delay eats the gain of centralized scheduling
After the small-cell count goes up, if scheduling is still centralized in a distant baseband pool, fronthaul or backhaul delay must stay under the time that coordination and retransmission require. If the delay exceeds that, a centralized scheduling decision arrives on the air after the channel has already changed, and spectral efficiency falls instead of rising. Density then keeps only the gain of “closer to the user.” The gain of joint processing is gone. The condition is that air-interface block errors move with backhaul delay while the received level stays stable.
A small cell with wireless backhaul also competes with the access link for the same spectrum. When backhaul is congested, the access side shows the whole site’s rate falling together, and the signal of a single device is not poor. Treating that site as a device fault and changing the card produces the same pattern on the neighboring devices. Look at that small cell’s backhaul bandwidth and delay before looking at the device.
After a small cell is switched off, the macro site must still be able to catch the camper
The dense layer usually sits on top of macro coverage. When a small cell loses power or its backhaul breaks, the device should be able to return to the macro site. If the macro site on this layer is set to the lowest priority with a harsh threshold, the device searches again and again for a small cell that has already disappeared, and the service stays down longer than the small cell takes to recover. The plan should name the camping target after a small cell is unavailable, and acceptance should turn one small cell off on purpose and see whether the device returns to the macro site and whether uplink is still usable after it returns.
A SimtoLink card follows the device through reselection and handover. The card itself does not choose site spacing. After a hotspot event ends and the small cells are turned off, the platform may show a batch of devices changing from a small-cell identity to a macro identity, with a lower rate and still online. That is a coverage-layer change, not an unpaid account. If devices go straight offline after the small cell is turned off, uplink budget of the macro site at that point is not enough. What needs to be added is fallback coverage, not more data volume on every card.
When there are too many neighbors, measurement itself becomes the burden
Dense networking raises the number of cells a device can hear. If the measurement list is too long, the device spends a large share of time scanning neighbors, the gaps left for actual data shrink, and the battery falls. If the list still contains a cell that has been removed, the device keeps listening on the period, fails to hear it, and records a measurement failure. Trim the list to the current topology, and give different neighbor types different measurement periods, rather than putting every heard cell on the same list. A stationary IoT device does not need to scan the full list as often as a high-speed device.
After the list is trimmed, handover and reselection have fewer candidates. Trim it wrong and the device cannot leave the only poor cell that remains. At acceptance, turn the primary small cell off on purpose and confirm that the list still has a macro site or a neighboring small cell to go to. A SimtoLink card only camps on the measurement result. It does not build the neighbor list. If devices in an area show many measurement failures and very few service bytes, hand the neighbor-list length and the failures to network optimization together, rather than raising device transmit power. More power only makes interference in the dense area heavier.