Review of wireless communication system

1. Representation of the cell coverage

• Cell, is the signal coverage
• Hexagonal cell is only used to simplify the depiction on the layout

in the picture above, you can see that in the real life, cell is very messy. Therefore, we use hexagonal model. In the wireless communication system, there are mobile station (ms) as a user, and base station (bts) as a transceiver. BTS has several type of antenna, such as Omnidertional, sectoring 120 degree, and sectoring 60 degree. The usefullnes of the sectoring pattern is like adding capacity and reduce interference. The Cell model, it has 4. Those are macrocell, microcell, picocell and femtocell.

2. Characteristic of cellular system.

• Frequency reuse
• Channel sharing
• Handover
• High spectral efficiency

Frequency Reuse

     The concept of frequency reuse allows the use of the same frequency in different cells, beyond the reach of interference. The parameter is a measure of power ratio signal/carrier to total interference power. Why we use frequency reuse? Because; limitation of frequency allocation, limited cell coverage area, raising the number of channels, from a cluster that contains several cell and co-channel intererence. 

Handover

     handover allows a user to move from one cell to another without any termination. Displacement occurs frequency/channel is automatically done by the system. Handover is a facility to guarantee communication continously if the costumer move from one cel to another.There are several type of handover; Intra-BTS handover, inter-BTS handover, inter-BSC handover, and inter-MSC handover.

1. intra-BTS: transfer relationship to a different channel on the same single base station
2. inter-BTS: transfer relationship between different base station in a single BSC
3. inter-BSC: transfer relationship between the BSC in a single MSC
4. inter-MSC: displacement relationship that occur in 2 different MSC

here is the mechanism of handover:

1. mobile station measure other cells
2. if better cell detected, handover initiated
3. mobile station handled by new cells, then handover completed

3. Cluster concept.

     Cluster contains several cells. K is representation of the number of cells inside cluster. 

the equation: K = i^2 + j^2 + i.j 

and to manage the frequency reuse, we need to know about the number of cells that separate the same frequency (we call as Co-channel Reuse distance ratio) and representated by Q. here is the equation: Q = (3.K)^0.5

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