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What Is iCSSR?
Intelligent Coordinated Scheduling and Spatial Reuse (iCSSR) is an enhanced technology based on Coordinated Spatial Reuse (CoSR). It combines dynamic-zoom smart antennas and eliminates co-channel interference by enabling APs to exchange coordination packets, achieving more efficient concurrent transmission.
Why Is iCSSR Needed?
In high-density scenarios, co-channel interference usually occurs because APs are densely deployed. As Wi-Fi generations evolve, the conventional 20 MHz deployment model can no longer accommodate the growing need for concurrent access. Ultra-large-bandwidth networking has become an inevitable trend. However, if the channel width is set 40 MHz or 80 MHz, the number of available channels decreases. For example, only three 80 MHz channels are available in some countries or regions. In this case, co-channel APs are close to each other, leading to severe co-channel interference, deteriorating user experience.
Coordinated Spatial Reuse (CoSR) technology resolves co-channel interference issues in high-density scenarios, but still has some disadvantages. For example, CoSR imposes high requirements for inter-AP coordinated scheduling measurement because the sharing AP needs to accurately control the transmit power of shared APs to eliminate interference. This requires APs to periodically measure the signal strengths of STAs on the same channel and exchange information, which consumes system resources and affects the coordination effect.
To address such issues, Huawei proposes iCSSR technology. It enhances spatial reuse and combines dynamic-zoom smart antennas. By adding adjacent co-channel APs to a coordinated scheduling group and using dynamic-zoom smart antenna technology, iCSSR enables APs to work collaboratively, reducing signal conflicts and improving the overall network performance.
iCSSR vs. CoSR
- Combination with dynamic-zooming smart antennas
CoSR uses traditional omnidirectional antennas and addresses interference issues by enabling the sharing AP to control the transmit power of shared APs. However, this causes performance loss of the shared APs. In contrast, iCSSR uses dynamic-zoom smart antennas to suppress co-channel interference, without the need for power adjustment. With iCSSR, each AP performs planned and directional transmission. Compared with CoSR, iCSSR improves the network performance in concurrent scenarios.
- Optimized user group–based scheduling
CoSR supports only one coordination mode, that is, concurrent scheduling for inner-circle STAs. Edge users are not processed. On the basis of CoSR, iCSSR also supports time-division scheduling for outer-circle STAs, which resolves interference issues in concurrent scenarios. In this way, iCSSR better meets the requirements of STAs in different locations and improves network efficiency.
How Does iCSSR Work?
iCSSR enables APs to exchange coordination packets over the air interface to eliminate co-channel interference, achieving efficient concurrent data transmission. APs supporting dynamic-zoom smart antennas can determine the relative distance between STAs based on signal strength and decide whether to switch to the directional mode in real time.
- Coordinated measurement
An AP periodically measures the signal strengths of associated and non-associated STAs on the same channel. Additionally, the AP exchanges measurement information with co-channel neighboring APs, and sends measurement information about STAs associated with neighboring APs to the neighboring APs. As shown in the following figure, AP1 measures the signal strengths of STA1 (associated STA) and STA2 (non-associated STA) on the same channel simultaneously, and synchronizes the signal strength of STA2 to AP2 (co-channel neighboring AP of AP1).
STAs are classified into inner-circle STAs (SINR > 23 dB) and outer-circle STAs based on the signal strength in the uplink Block ACK (BA) frames they send. The inner-circle and outer-circle STA groups are used for different coordinated transmission modes.
Coordinated measurement - Coordinated scheduling
In coordinated scheduling, the sharing AP to select the most suitable STAs from co-channel APs for coordinated data transmission.
The AP that preempts the air interface is considered as the sharing AP. The sharing AP selects one or two co-channel neighboring APs based on the measurement result as coordinated APs for concurrent transmission. The sharing AP first determines the target STA for transmission, and then selects the co-channel neighboring AP with the largest path loss relative to this STA.
- Coordinated transmission
Two coordinated transmission modes are available: concurrent coordination for inner-circle STAs and time-division coordination for outer-circle STAs.
The coordinated transmission process for inner-circle STAs is as follows:- The AP that preempts the air interface through carrier sense multiple access with collision avoidance (CSMA/CA) becomes the sharing AP.
- The sharing AP sends coordination frames to instruct neighboring APs to concurrently send data with the allowed maximum transmit power at the specified time.
- Each AP switches its antennas to the directional mode using dynamic-zoom smart antenna technology to make the signals more concentrated.
- The sharing AP sends data to inner-circle STAs connected to it.
- Based on notification of the sharing AP, each shared AP selects the inner-circle STA with the strongest signal strength and the most packets to be sent among associated STAs, and sends data to the selected STA.
- All APs continue to preempt the air interface for the subsequent coordination process.
The coordinated transmission process for outer-circle STAs is as follows:- The AP that preempts the air interface through CSMA/CA is the sharing AP.
- Each AP switches its antennas to the omnidirectional mode using dynamic-zoom smart antenna technology. The sharing AP sends coordination frames to instruct the shared APs to perform time-division scheduling.
- The sharing AP first schedules all outer-circle STAs connected to it.
- Each shared AP constructs frames based on the instruction in the coordination frame sent from the sharing AP, and sends the frames in sequence to schedule outer-circle STAs connected to it.
- All APs continue to preempt the air interface for the subsequent coordination process.
Dynamic-zoom smart antennas
Dynamic-zoom smart antenna technology enables multi-beam switching on a single hardware antenna, achieving antenna beam zooming. This multi-beam zoom antenna flexibly switches between the directional and omnidirectional modes based on the signal strength of STAs.
- Directional mode: Directional beams are selected for inner-circle STAs to improve the signal strength in the coverage direction and reduce energy leakage in the interference direction, thereby improving the network-wide signal-to-noise ratio (SNR).
- Omnidirectional mode: Omnidirectional beams are selected for outer-circle STAs to reduce air interface conflicts and increase the downlink MCS index of outer-circle STAs.
What Are the Application Scenarios of iCSSR?
iCSSR technology is applicable to high-density scenarios such as education (excluding high-density stadiums and auditoriums) and open office (excluding desktop cloud) scenarios.
- Author： Liang Jiao
- Updated on： 2025-11-21
- Views： 563
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