cell-sectoring

A single omnidirectional antenna at a cell site broadcasts in all 360° directions, but users are not evenly distributed around the cell. More importantly, signals transmitted toward the back of the cell (toward co-channel cells) cause co-channel interference. Cell sectoring uses directional antennas to divide a cell into sectors, focusing energy where users are and reducing interference toward co-channel cells.

Cell sectoring divides a single cell into 3 or 6 sectors (120° or 60° each) using directional antennas instead of one omnidirectional antenna. Each sector operates as an independent cell with its own channel set, reducing co-channel interference and increasing capacity per unit area.

1. Instead of one omnidirectional antenna, install 3 (120°) or 6 (60°) directional antennas per cell site
2. Each sector covers a wedge-shaped area; total coverage remains 360°
3. Each sector is assigned its own subset of the cell’s frequencies
4. Since each antenna covers only a 60–120° sector, signals are not broadcast toward co-channel cells
5. Effective co-channel interference decreases by the number of sectors
6. C/I ratio improves, or cluster size (N) can be reduced, increasing capacity

The effective reuse factor improves by a factor equal to the number of sectors: 3 sectors reduces interference by 3× or allows 3× reduction in cluster size (from N=7 to N=4).

• Reduces effective co-channel interference by a factor of 3 (or the number of sectors)
• Allows smaller cluster sizes (higher capacity) while maintaining C/I
• Improves downlink coverage for directional antennas
• Requires careful sector boundary planning to avoid coverage gaps
• Common configuration: 3 sectors per cell (120° each)
• Sectors can overlap at boundaries, enabling soft handoff zones

• Built from: Cellular Mobile System — sectoring is a capacity enhancement technique for cellular systems
• Built from: Antenna Types — sectoring uses directional antennas
• Built from: Frequency Reuse — sectoring improves effective frequency reuse
• Related: Cell Splitting — another capacity enhancement technique
• Related: Co-Channel Interference — sectoring directly reduces this
• Related: GSM Architecture — GSM BTS supports sectorized deployments

• Sectors can cause coverage gaps at their boundaries
• Requires careful RF planning to ensure uniform coverage
• Sector boundaries are not static — they shift with traffic load and seasonal foliage
• Ping-pong handovers can occur at sector boundaries