25-08-2017, 09:32 PM
TRAINING REPORT ON RADIO NETWORK PLANNING AND OPTIMIZATION
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Introduction[b]
Since the early days of GSM development, GSM system network planning has undergone extensive modification so as to fulfill the ever-increasing demand from operators and mobile users with issues related to capacity and coverage. Radio network planning is perhaps the most important part of the whole design process owing to its proximity to mobile users.Before going into details of the process, we first look at some fundamental issues.
[b]1. BASICS OF RADIO NETWORK PLANNING
The Scope of Radio Network Planning
The Radio network is the part of the network that includes the base station (BTS) and the mobile station (MS) and the interface between them, as shown in Figure 2.1. As this is the part of the network that is directly connected to the mobile user, it assumes considerable importance. The base station has a radio connection with the mobile, and this base station should be capable of communicating with the mobile station within a certain coverage area, and of maintaining call quality standards. The radio network should be able to offer sufficient capacity and coverage.
Cell Shape
In mobile networks we talk in terms of ‘cells’. One base station can have many cells. In general, a cell can be defined as the area covered by one sector, i.e. one antenna system. The hexagonal nature of the cell is an artificial shape This is the shape that is closest to being circular, which represents the ideal coverage of the power transmitted by the base station antenna. The circular shapes are themselves inconvenient as they have overlapping areas of coverage; but, in reality, their shapes look like the one A practical network will have cells of nongeometric shapes, with some areas not having the required signal strength for various reasons.
Elements in a Radio Network Mobile Station (MS)
The mobile station is made up of two parts, as shown in Figure 1.3: the handset and thesubscriber identity module (SIM). The SIM is personalised and is unique to the subscriber.The handset or the terminal equipment should have qualities similar to those of fixed phones in terms of quality, apart from being user friendly. The equipment also has functionalities like GMSK modulation and demodulation up to channel coding/decoding. It needs to be dual-tone multi-frequency generation and should have a long-lasting battery.The SIM or SIM card is basically a microchip operating in conjunction with a memory card. The SIM card’s major function is to store data for both the operator and subscriber.The SIM card fulfills the needs of the operator and the subscriber as the operator is able to maintain control over the subscription and the subscriber can protect his or her personal information. Thus, the most important SIM functions include authentication, radio transmission security, and storing of the subscriber data.
Base Transceiver Station (BTS)
From the perspective of the radio network-planning engineer the base station is perhaps the most important element in the network as it provides the physical connection to the mobile station through the air interface. And on the other side, it is connected to the BSC via an Abis interface. A simplified block diagram of a base station is shown in Figure 1.4.The transceiver (TRX) consists basically of a low-frequency unit and a high-frequency unit. The low-frequency unit is responsible for digital signal processing and the high frequency unit is responsible for GMSK modulation and demodulation.
Channel Configuration in GSM
There are two types of channels in the air interface: physical channels and logical channels.The physical channel is all the time slots (TS) of the BTS. There are again two types in this:half-rate (HR) and full-rate (FR). The FR channel is a 13 kbps coded speech or data channel with a rawdata rate of 9.6, 4.8 or 2.6 kbps, while the HR supports 7, 4.8 or 2.4 kbps. ‘Logical channel’ refers to the specific type of information that is carried by the physical channel.Logical channels can also be divided into two types: traffic channels (TCH) and control channels (CCH). Traffic channels are used to carry user data (speech/data) while the control channels carry the signalling and control information.
. RADIO NETWORK PLANNING PROCESS
The main aim of radio network planning is to provide a cost-effective solution for the radio network in terms of coverage, capacity and quality. The network planning process and design criteria vary from region to region depending upon the dominating factor, which could be capacity or coverage. The design process itself is not the only process in the whole network design, and has to work in close coordination with the planning processes of the core and especially the transmission network. But for ease of explanation, a simplified process just for radio network planning is shown in Figure 2.5.The process of radio network planning starts with collection of the input parameters such as the network requirements of capacity, coverage and quality. These inputs are then used to make the theoretical coverage and capacity plans. Definition of coverage would include defining the coverage areas, service probability and related signal strength. Definition of capacity would include the subscriber and traffic profile in the region and whole area, availability of the frequency bands, frequency planning methods, and other information such as guard band and frequency band division. The radio planner also needs information on the radio access system and the antenna system performance associated with it.
The pre-planning process results in theoretical coverage and capacity plans. There are coverage-driven areas and capacity-driven areas in a given network region. The average cell capacity requirement per service area is estimated for each phase of network design, to identify the cut-over phase where network design will change from a coverage-driven to a capacity-driven process. While the objective of coverage planning in the coverage-driven areas is to find the minimum number of sites for producing the required coverage, radio planners often have to experiment with both coverage and capacity, as the capacity requirements may have to increase the number of sites, resulting in a more effective frequency usage and minimal interference.
Radio Cell and Wave Propagation
Coverage in a cell is dependent upon the area covered by the signal. The distance travelled by the signal is dependent upon radio propagation characteristics in the given area. Radio propagation varies from region to region and should be studied carefully, before predictions for both coverage and capacity are made. The requirement from the radio planners is generally a network design that covers 100% of the area. Fulfilling this requirement is usually impossible, so efforts are made design a network that covers all the regions that may generate traffic and to have ‘holes’ only in no-traffic zones.The whole land area is divided into three major classes – urban, suburban and rural –based on human-made structures and natural terrains. The cells (sites) that are constructed in these areas can be classified as outdoor and indoor cells. Outdoor cells can be further classified as macro-cellular, micro-cellular or pico-cellular (see Figure 2.6).
[attachment=42676]
Introduction[b]
Since the early days of GSM development, GSM system network planning has undergone extensive modification so as to fulfill the ever-increasing demand from operators and mobile users with issues related to capacity and coverage. Radio network planning is perhaps the most important part of the whole design process owing to its proximity to mobile users.Before going into details of the process, we first look at some fundamental issues.
[b]1. BASICS OF RADIO NETWORK PLANNING
The Scope of Radio Network Planning
The Radio network is the part of the network that includes the base station (BTS) and the mobile station (MS) and the interface between them, as shown in Figure 2.1. As this is the part of the network that is directly connected to the mobile user, it assumes considerable importance. The base station has a radio connection with the mobile, and this base station should be capable of communicating with the mobile station within a certain coverage area, and of maintaining call quality standards. The radio network should be able to offer sufficient capacity and coverage.
Cell Shape
In mobile networks we talk in terms of ‘cells’. One base station can have many cells. In general, a cell can be defined as the area covered by one sector, i.e. one antenna system. The hexagonal nature of the cell is an artificial shape This is the shape that is closest to being circular, which represents the ideal coverage of the power transmitted by the base station antenna. The circular shapes are themselves inconvenient as they have overlapping areas of coverage; but, in reality, their shapes look like the one A practical network will have cells of nongeometric shapes, with some areas not having the required signal strength for various reasons.
Elements in a Radio Network Mobile Station (MS)
The mobile station is made up of two parts, as shown in Figure 1.3: the handset and thesubscriber identity module (SIM). The SIM is personalised and is unique to the subscriber.The handset or the terminal equipment should have qualities similar to those of fixed phones in terms of quality, apart from being user friendly. The equipment also has functionalities like GMSK modulation and demodulation up to channel coding/decoding. It needs to be dual-tone multi-frequency generation and should have a long-lasting battery.The SIM or SIM card is basically a microchip operating in conjunction with a memory card. The SIM card’s major function is to store data for both the operator and subscriber.The SIM card fulfills the needs of the operator and the subscriber as the operator is able to maintain control over the subscription and the subscriber can protect his or her personal information. Thus, the most important SIM functions include authentication, radio transmission security, and storing of the subscriber data.
Base Transceiver Station (BTS)
From the perspective of the radio network-planning engineer the base station is perhaps the most important element in the network as it provides the physical connection to the mobile station through the air interface. And on the other side, it is connected to the BSC via an Abis interface. A simplified block diagram of a base station is shown in Figure 1.4.The transceiver (TRX) consists basically of a low-frequency unit and a high-frequency unit. The low-frequency unit is responsible for digital signal processing and the high frequency unit is responsible for GMSK modulation and demodulation.
Channel Configuration in GSM
There are two types of channels in the air interface: physical channels and logical channels.The physical channel is all the time slots (TS) of the BTS. There are again two types in this:half-rate (HR) and full-rate (FR). The FR channel is a 13 kbps coded speech or data channel with a rawdata rate of 9.6, 4.8 or 2.6 kbps, while the HR supports 7, 4.8 or 2.4 kbps. ‘Logical channel’ refers to the specific type of information that is carried by the physical channel.Logical channels can also be divided into two types: traffic channels (TCH) and control channels (CCH). Traffic channels are used to carry user data (speech/data) while the control channels carry the signalling and control information.
. RADIO NETWORK PLANNING PROCESS
The main aim of radio network planning is to provide a cost-effective solution for the radio network in terms of coverage, capacity and quality. The network planning process and design criteria vary from region to region depending upon the dominating factor, which could be capacity or coverage. The design process itself is not the only process in the whole network design, and has to work in close coordination with the planning processes of the core and especially the transmission network. But for ease of explanation, a simplified process just for radio network planning is shown in Figure 2.5.The process of radio network planning starts with collection of the input parameters such as the network requirements of capacity, coverage and quality. These inputs are then used to make the theoretical coverage and capacity plans. Definition of coverage would include defining the coverage areas, service probability and related signal strength. Definition of capacity would include the subscriber and traffic profile in the region and whole area, availability of the frequency bands, frequency planning methods, and other information such as guard band and frequency band division. The radio planner also needs information on the radio access system and the antenna system performance associated with it.
The pre-planning process results in theoretical coverage and capacity plans. There are coverage-driven areas and capacity-driven areas in a given network region. The average cell capacity requirement per service area is estimated for each phase of network design, to identify the cut-over phase where network design will change from a coverage-driven to a capacity-driven process. While the objective of coverage planning in the coverage-driven areas is to find the minimum number of sites for producing the required coverage, radio planners often have to experiment with both coverage and capacity, as the capacity requirements may have to increase the number of sites, resulting in a more effective frequency usage and minimal interference.
Radio Cell and Wave Propagation
Coverage in a cell is dependent upon the area covered by the signal. The distance travelled by the signal is dependent upon radio propagation characteristics in the given area. Radio propagation varies from region to region and should be studied carefully, before predictions for both coverage and capacity are made. The requirement from the radio planners is generally a network design that covers 100% of the area. Fulfilling this requirement is usually impossible, so efforts are made design a network that covers all the regions that may generate traffic and to have ‘holes’ only in no-traffic zones.The whole land area is divided into three major classes – urban, suburban and rural –based on human-made structures and natural terrains. The cells (sites) that are constructed in these areas can be classified as outdoor and indoor cells. Outdoor cells can be further classified as macro-cellular, micro-cellular or pico-cellular (see Figure 2.6).