Intelligent Cell Concept And Application
An increase in system capacity can be achieved in wireless PCS systems by applying the intelligent cell concept. There are two means by which intelligence in a cell can reduce interference. First it can use intelligence to deliver the signal to the mobile unit, in which cell isolates the signal with multiple zones. Second it can tolerate a great deal of interference while receiving the signal in which the signal resides with the interference but retains its processing gain
The intelligent PCS cell Types:
- Power-delivery Intelligent cell
- Processing-gain intelligent cell
The intelligent cell may be a large-sized cell such as a macrocell or a small-sized cell such as a microcell
Power-Delivery Intelligent Cells:
- In a conventional macrocell or microcell, when a mobile unit enters a cell or a sector the cell site blankets the entire cell or sector with power to ensure the communication.In a cellular system the frequency reuse scheme is implemented to increase spectrum efficiency.(see figure 9.1)
- If two cochannel cells (cells that use the same frequency) can be placed much closer to each other, the same frequency channel can be reused more frequently in a given geographical area, and so can a finite number of frequency channels provide many more traffic channels. Thereby both system capacity and spectrum efficiency arc increased.
- A frequency-reuse system, such as the cellular system, we always use the term radio capacity to measure the traffic capacity. The radio capacity m is defined as:[ 1]
- where m is the number of channels/cell in an omnidirectional radiation cell.
- M is the total number of frequency channels, K is the cell reuse factor, and S is the number of sectors.
D is the co-channel-cell separation and R is the cell radius.
- The relationship between the carrier-to-interference ratio (C/I) and D/R can be expressed
In general there are three kinds of zone-divided-cell systems:
- Sectorial Cells
- Intelligent Microcells
- Reuse of Sectorial Beams with Directional Antennas