INTRODUCTION
The cellular is system level idea which calls for replacing a single transmitter used to cover a large area with many cells, each providing coverage only to a small portion of the service area. This chapter is designed to provide with an overview of basic concepts of wireless communications. This chapter addresses some major problems in the cellular radio environment plus some solution used to resolve these problems.
Upon completion of this chapter we will be able to :
· Briefly describe the frequency reuse, capacity and coverage.
· Briefly describe the time Division Multiple Access Technique (TDMA)
· Transmission problems and the methods used to solve those.
7.1 FREQUENCY CONCEPT
An MS communicate with a BTS by transmitting or receiving radio waves, which consist of electromagnetic energy. The frequency of a radio wave is the number of times that the wave oscillates per second. The frequencies used by the mobile networks vary according to the standard being used.
The following table summarizes the frequency-related specifications of each of the GSM systems
Table 7.1 Frequency related specifications
System
GSM-900
GSM-1800
GSM-1900
Frequencies : Uplink
880-915 MHz
1710-1785 MHz
1850-1910 MHz
Downlink
925-960 MHz
1805-1880 MHz
1930-1990 MHz
Wave length
33 cm
17 cm
16 cm
Band width
35 MHz
75 MHz
60 MHz
Duplex distance
45 MHz
95 MHz
80 MHz
Carrier separation
200 KHz
200 KHz
200 KHz
Radio channels
175
375
300
Transmission
270 kbps
270 kbps
270 kbps
7.1.1 BANDWIDTH
Carrier spacing 200 kHzBandwidth is the term used to describe the amount of frequency range allocated to one application. The bandwidth given to an application depends on the amount of available frequency spectrum. The amount of bandwidth available is an important factor in determining the capacity of mobile system, i.e. the number of calls, which can be handled.
The cellular is system level idea which calls for replacing a single transmitter used to cover a large area with many cells, each providing coverage only to a small portion of the service area. This chapter is designed to provide with an overview of basic concepts of wireless communications. This chapter addresses some major problems in the cellular radio environment plus some solution used to resolve these problems.
Upon completion of this chapter we will be able to :
· Briefly describe the frequency reuse, capacity and coverage.
· Briefly describe the time Division Multiple Access Technique (TDMA)
· Transmission problems and the methods used to solve those.
7.1 FREQUENCY CONCEPT
An MS communicate with a BTS by transmitting or receiving radio waves, which consist of electromagnetic energy. The frequency of a radio wave is the number of times that the wave oscillates per second. The frequencies used by the mobile networks vary according to the standard being used.
The following table summarizes the frequency-related specifications of each of the GSM systems
Table 7.1 Frequency related specifications
System
GSM-900
GSM-1800
GSM-1900
Frequencies : Uplink
880-915 MHz
1710-1785 MHz
1850-1910 MHz
Downlink
925-960 MHz
1805-1880 MHz
1930-1990 MHz
Wave length
33 cm
17 cm
16 cm
Band width
35 MHz
75 MHz
60 MHz
Duplex distance
45 MHz
95 MHz
80 MHz
Carrier separation
200 KHz
200 KHz
200 KHz
Radio channels
175
375
300
Transmission
270 kbps
270 kbps
270 kbps
7.1.1 BANDWIDTH
Carrier spacing 200 kHzBandwidth is the term used to describe the amount of frequency range allocated to one application. The bandwidth given to an application depends on the amount of available frequency spectrum. The amount of bandwidth available is an important factor in determining the capacity of mobile system, i.e. the number of calls, which can be handled.
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