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Introduction to GSM, 2nd ed.

Introduction to GSM Book

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Frequency Reuse

Frequency reuse is the process of using the same radio frequencies on radio transmitter sites within a geographic area, which are separated by sufficient distance to cause minimal interference with each other. Frequency reuse allows for a dramatic increase in the number of customers that can be served (capacity) within a geographic area on a limited amount of radio spectrum (limited number of radio channels).

Frequency planning is the assignment (coordination) of radio channel frequencies in wireless systems that have multiple transmitters to minimize the amount of interference caused by transmitters that operate on the same frequency. Frequency planning is used to help ensure that combined interference levels from nearby transmitters that are operating on or near the same frequency do not exceed a certain interference (desired signal to interference) level compared to the desired signal.

The ability to reuse frequencies depends on various factors, including the ability of channels to operate in with interference signal energy attenuation between the transmitters. A frequency plan is the assignment of radio frequencies to radio transmission sites (cell sites) that are located within a defined geographic area. The frequency plan may use ratios that are different dependent on the number of transmitting sites to the number of antennas (sectors) on each site. A common frequency reuse plan for GSM is the ability to reuse a radio frequency on every 4th site that has three 120 degree sectors each 12 total sectors. This plan is commonly called 4/12.

sThis figure shows how GSM can use frequency reuse to increase the system capacity. This diagram shows that a frequency in a GSM system can be reused at nearby cell sites provided the radio signal level from the interfering (unwanted) cell is 9 dB to 14 dB below the desired signal level.

 

Introduction to GSM Book

more details

Introduction to GSM, 2nd ed.

This book explains the basic components, technologies used, and operation of GSM systems. You will discover why mobile telephone service providers have upgraded from 1st generation analog systems to more efficient and feature rich 2nd generation GSM systems. You will also discover how 2nd generation systems are gradually evolving into 3rd generation broadband multimedia systems.

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