Definition
Interference Coordination (Interference Coordination) reduces inter-cell interference (ICI) in co-channel networks through coordination in the frequency, time, or power domain, improving SINR and rates, especially for cell edge users. ICIC (Inter-Cell Interference Coordination) and eICIC (enhanced ICIC, almost blank subframe) are key technologies in LTE/dense networking, working collaboratively with SON and power control.
Technical Methods
- Frequency Domain: Fractional Frequency Reuse (FFR), Soft Frequency Reuse (SFR), edge users use different frequency bands to avoid co-channel interference
- Time Domain: eICIC Almost Blank Subframe (ABS), macro cells reduce power in some subframes to give resources to small cell users
- Power Domain: Power control, Cell Range Expansion (CRE) bias, balancing macro and small cell load
CoMP and 5G
CoMP (Coordinated Multi-Point) further suppresses interference through multi-cell joint scheduling/precoding. 5G NR reduces interference through more flexible time-frequency resources, beamforming , dynamic TDD, etc. Interference coordination directly affects the connection quality of edge IoT devices.
Typical Use Cases
Heterogeneous networks (macro cells + small cells ), dense networking, indoor-outdoor coordination, etc. IoT devices of SimtoLink can benefit from SINR improvements brought by interference coordination at coverage edges.
Interference coordination improves the connection quality of users at cell edges, and IoT devices can benefit in coverage edge or dense deployment scenarios. SimtoLink IoT SIM cards automatically enjoy performance improvements brought by interference coordination in the operator network. The SimtoLink cloud platform can analyze the signal quality in the device's area and provide network optimization suggestions for IoT projects deployed in complex coverage environments.
Which slice of frequency an edge user gets depends on the reuse pattern
In a same-frequency network, a user at the cell center is close to the base station and interference is relatively small. An edge user also hears the neighbor cell, and the signal-to-interference ratio fails first. Partial frequency reuse leaves a slice of frequency for the edge. Neighboring cells use different slices at the edge, and the center reuses all of the spectrum or another slice. Soft reuse is not a hard ban. It lets the edge band be transmitted at lower power in the neighbor cell. To see whether a device actually received that protection, see whether the resource blocks it was scheduled on fall in the position planned for the edge, not only how far it is from the base station. Far away, and still scheduled on the center band, interference coordination never reached this device.
Once reuse cuts the spectrum into pieces, peak bandwidth for a single user falls. An IoT small packet usually does not feel the peak loss. Broadband video does. Do not turn the whole site into very low reuse for a few sensors at the edge, unless edge traffic itself is the main load of the site. The plan should name which bearers count as edge-first.
Almost-blank subframes help only when a macro site is bearing down on a small cell
Enhanced interference coordination has the macro site send less, or send nothing, on certain subframes. Small-cell users transmit in those subframes and so avoid the strong macro interference. This arrangement depends on two cell layers overlapping, and on small-cell users being extended closer to the macro site. If the network is all macro sites, or the interference is between small cells on the same layer, blank subframes do not line up with the interference source, and the resources left empty are only waste. Confirm first that the main interferer is that macro site. If edge rate rises after the matching macro subframes are turned down, the configuration is right. If nothing changes, do not keep raising the blank ratio.
The blank-subframe ratio is a trade between capacity and edge rate. If the ratio is too high, throughput of ordinary users on the macro site falls, including IoT devices under the macro site. After an adjustment, look at both the small-cell edge and the macro-cell center. Do not look only at the one device being protected.
Coordinated multipoint needs backhaul that can keep up with joint scheduling
Coordinated multipoint lets neighboring cells schedule or precode together for the same device, and turns what used to be interference into a useful signal. That requires cells to exchange channel information and user data, and backhaul delay has to keep up with how fast the channel changes. If the delay cannot do that, joint transmission aims the energy off target, and the result is worse than simply doing power control. The condition is that edge block errors rise after coordination is turned on, and backhaul delay is also high. Fall back to frequency or power coordination, rather than widening the coordination area further.
A SimtoLink device cannot turn on base-station interference coordination by itself. It can only live with the air-interface result after coordination. If a card at the cell edge retransmits again and again, and the neighbor level is close to the serving cell, the value of the platform record is to mark the point as an edge, so the network side can check whether reuse and blank subframes cover that point. Changing the card or raising the plan does not change neighbor power. Moving the antenna out of the overlap is often more effective than changing application retransmission.
Pull edge users into the small cell and the interference source switches sides
When a bias widens the small-cell range, users who used to be served by the macro site hang off the small cell instead. They are still close to the macro site, so the macro site becomes a strong interferer. What is needed then is for the macro site to give way on the matching resources, not for the small cell to raise power again. The higher the power, the worse other users at the macro edge become. Interference has only changed direction. The bias is too large when the small-cell user count rises, the macro-edge rate falls, and the signal-to-interference ratio of those small-cell users has not improved. Stop the bias where the small cell can still hold its signal-to-interference ratio.
A bias change also changes idle-mode camping. If connected-mode coordination parameters are not changed with it, the device camps on a cell whose scheduler does not protect it. A SimtoLink device meets a different interference environment as its camping cell changes. A large rate difference at the same place between day and night may be surrounding load changing the effect of the coordination parameters, not a change in card status. Record rate and neighbor level together before deciding whether the bias should be adjusted, rather than only increasing the retransmission count.