The
Kansas City has the following population and the spectrum band.
- Population - 50,000 – 500,000
- Bandwidth - 900 MHz – 905 MHz à 5 MHz
- GSM Carrier separation - 200 KHz
This system is developed using 7 cell cluster system.
Following assumptions are made in order to decide the number of base stations needed.
- Aimed Grade of Service - 2%
- Call duration - 5 min
- Distance from Base Station - 1m
- Transmitter Power - 1mw
- Receiver Power - -100 dBm
- Path loss exponent - 3
The “ N “ cells which collectively use the complete set of available frequencies is called a cluster.
If i = 2 and j = 1 then,
N = i2 + ij + j2
N = 22 + (2*1) + (1)2
N= 4 + 2 + 1
N = 7
Co-Channel Reuse Distance
- D1 - 1m
- P1 - 1 mw
- P2 - -100 dBm
- N - 3
- D2 - ?
log 10 P = -10
P = 10 -10 mw
Number of Carriers Available = Bandwidth / Carrier separation
= 5 MHz / 200 KHz
Assuming a cell gets equal number of carriers,
Number of Carriers per Cell = Number of Carriers Available / 7
= 25 / 7
= 3.571
= 3 (approximately)
Therefore,
Number of Channels per Cell = Number of Carriers per Cell * 8
= 3 * 8
= 24
Two channels are taken for the transmission of control signals. Therefore,
Number of Usable Channels per Cell = Number of channels per cell – 2
= 24 – 2
= 22
Busy Hour Traffic
· Aimed Grade of Service - 2%
· Usable Channels per Cell - 22
Therefore,
Busy Hour Traffic = 14.90 Erlang
Number of Users per Cell
Assuming the call arrival rate in busy hour à 5 min
Traffic = Number of users per cell * call arrival rate
14.9 E = N * (5 / 60)
(14.9 * 60) / 5 = N
178.8 = N
Number of Users per Cell = 178 (approximately)
Therefore, a cell can accommodate 178 users.
Number of base stations required = Number of Users / Call Arrival Rate
= 500,000 / 178
= 2808.98
= 2809 (approximately)
The competitive outlook of the industry has to go beyond cost cutting and find the underlying ways to improve efficiency, while delivering value-added services for mobile end users.
In GSM 900 system, there are 125 channels in both uplink and downlink, and these channels span the available bandwidth of GSM 900. The frequency is a scare resource in GSM system, and the frequency must be carefully planned to be reused. The frequency reuse factor is defined as the number of base stations that can be implemented between the current base station and the ones before the same frequency is reused. The antenna height can also influence the reuse factor, since the higher the antenna is, the greater the possibility that the signal causes more interference. Frequency planning is done using one of the previously mentioned optimization algorithms, by setting an adequate cost function to maximize the capacity of the network while minimizing the number of frequency sub-bands used.
When you consider the spectrum management, no single reform in isolation would provide a solution for the increasing pressures placed on spectrum management. However, in combination with regulatory, process-oriented and technical reforms, economic methods of spectrum management can help to create an improved spectrum management system. There are several methods for spectrum pricing.
The simplest method that of the administrative cost recovery price already adopted in many countries of the world is based on estimation of the funding required recovering the yearly costs incurred by the government agency for managing the spectrum resource. A number of options for spectrum price determination based on system performance have been developed. The price could be built up from a number of separate elements based on any or all of various criteria such as the amount of spectrum used, number of channels or links used, degree of congestion, efficiency of radio equipment, transmitter power/coverage area, geographical location and so forth. The basic principle of this approach is to identify various technical parameters in order to measure the spectrum volume used or define the “pollution area” of a radio system as a common basis for establishing spectrum fees. Another method is the spectrum fee is based on the costs of spectrum reframing. The so-called “differential rent spectrum price” basically exploits the difference between equipment costs for systems providing the same service but using different spectrum ranges.
The aims of differential rent spectrum prices are to establish equal opportunities in the market among all operators using different bands and access media and to stimulate operators to use higher frequency ranges or alternative wire technology, resulting in increased efficiency in spectrum use. Such method can only be successful to the extent that suitable alternative frequencies or technologies exist.
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