Network dimensioning
Network Dimensioning (ND) is usually the first task to start the planning of a given cellular network. The main result is an estimation of the equipment necessary to meet the following requirements.
• Capacity
• Coverage
• Quality
ND gives an overall picture of the network and is used as a base for all further planning activities.
Network dimensioning input
The inputs are
• Capacity related
Spectrum available.
Subscriber growth forecast
Traffic density map (Traffic per subs)
• Coverage related
Coverage regions
Area types information
• Quality related
MS classes
Blocking probability
Location probability
Redundancy
Indoor coverage.
The operator normally supplies the input data, but use of defaults is also possible. The technical parameter and characteristics of the equipment to be used are another very important part of the input. This includes the basic network modules (MSC, BSC, BTS) as well as some additional elements (antennas, cables…)
Capacity calculation
The capacity of a given network is measured in terms of the subscribers or the traffic load that it can handle. The former requires knowledge of subscriber calling habits (average traffic per subscriber) while the latter is more general. The steps for calculating the network capacity are
• Find the maximum no of carriers per cell that can be reached for the different regions based on the frequency reuse patterns and the available spectrum.
• Calculate the capacity of the given cell using blocking probability and the number of carriers.
• Finally the sum of all cell capacities gives the network capacity.
Spectrum efficiency
= S / (n X A X B)
S - total spectrum available
n - reuse factor
A - cell area
B - channel bandwidth
Erlang B table
To calculate the capacity of the given cell using blocking probability and the number of carriers we need the well-known Erlang B table or formulas and the no of traffic channels for different number of carriers. The result we get is the traffic capacity in Erlangs, which can easily be transferred into the number of subscribers.
Erlangs = n X t / 3600
• n = no of calls attempted
• t = total duration in seconds
Frequency reuse schemes
A cellular network can easily be drawn as a combination of hexagons or circles by the help of regular grids. One of the advantages is the possibility to try different frequency reuse patterns (clusters) and calculate the expected co-channel interference. This is required to assign a frequency reuse no (cluster size) to any of the network regions area types. It is clear that the high-density regions (big cities) are the most problematic parts of the network.
Power budget calculations
To guarantee a good quality in both directions (uplink and downlink) the power of BTS and MS should be in balance at the edge of the cell. The main idea behind the power budget calculations is to receive the maximum output power level of BTS transmitter as a function of BTS and MS sensitivity levels, MS output power, antenna gain (Rx & TX), diversity reception, cable loss, combiner loss, etc….
The power budget calculations provides following useful results:
BTS transmitted power: BTS transmitted power is adjusted to provide a balanced radio link (i.e. Uplink Downlink radio link performance is the same) for given BTS and MS receiver performance, MS transmitter performance, antenna and feeder cable characteristics.
Isotropic path loss: this is the maximum path loss between BTS and MS according to given radio system performance requirements.
Coverage threshold: downlink signal strength at coverage area border for given location probability.
Cell range for indoor and outdoor coverage: this is a rough indication about cell range in different area types and can be used for network dimensioning. It can also be used for comparing the effect of different equipment specification and antenna heights for the cell range.
Network Dimensioning (ND) is usually the first task to start the planning of a given cellular network. The main result is an estimation of the equipment necessary to meet the following requirements.
• Capacity
• Coverage
• Quality
ND gives an overall picture of the network and is used as a base for all further planning activities.
Network dimensioning input
The inputs are
• Capacity related
Spectrum available.
Subscriber growth forecast
Traffic density map (Traffic per subs)
• Coverage related
Coverage regions
Area types information
• Quality related
MS classes
Blocking probability
Location probability
Redundancy
Indoor coverage.
The operator normally supplies the input data, but use of defaults is also possible. The technical parameter and characteristics of the equipment to be used are another very important part of the input. This includes the basic network modules (MSC, BSC, BTS) as well as some additional elements (antennas, cables…)
Capacity calculation
The capacity of a given network is measured in terms of the subscribers or the traffic load that it can handle. The former requires knowledge of subscriber calling habits (average traffic per subscriber) while the latter is more general. The steps for calculating the network capacity are
• Find the maximum no of carriers per cell that can be reached for the different regions based on the frequency reuse patterns and the available spectrum.
• Calculate the capacity of the given cell using blocking probability and the number of carriers.
• Finally the sum of all cell capacities gives the network capacity.
Spectrum efficiency
= S / (n X A X B)
S - total spectrum available
n - reuse factor
A - cell area
B - channel bandwidth
Erlang B table
To calculate the capacity of the given cell using blocking probability and the number of carriers we need the well-known Erlang B table or formulas and the no of traffic channels for different number of carriers. The result we get is the traffic capacity in Erlangs, which can easily be transferred into the number of subscribers.
Erlangs = n X t / 3600
• n = no of calls attempted
• t = total duration in seconds
Frequency reuse schemes
A cellular network can easily be drawn as a combination of hexagons or circles by the help of regular grids. One of the advantages is the possibility to try different frequency reuse patterns (clusters) and calculate the expected co-channel interference. This is required to assign a frequency reuse no (cluster size) to any of the network regions area types. It is clear that the high-density regions (big cities) are the most problematic parts of the network.
Power budget calculations
To guarantee a good quality in both directions (uplink and downlink) the power of BTS and MS should be in balance at the edge of the cell. The main idea behind the power budget calculations is to receive the maximum output power level of BTS transmitter as a function of BTS and MS sensitivity levels, MS output power, antenna gain (Rx & TX), diversity reception, cable loss, combiner loss, etc….
The power budget calculations provides following useful results:
BTS transmitted power: BTS transmitted power is adjusted to provide a balanced radio link (i.e. Uplink Downlink radio link performance is the same) for given BTS and MS receiver performance, MS transmitter performance, antenna and feeder cable characteristics.
Isotropic path loss: this is the maximum path loss between BTS and MS according to given radio system performance requirements.
Coverage threshold: downlink signal strength at coverage area border for given location probability.
Cell range for indoor and outdoor coverage: this is a rough indication about cell range in different area types and can be used for network dimensioning. It can also be used for comparing the effect of different equipment specification and antenna heights for the cell range.
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