- The cell size and traffic load when using ATM are relatively small, so it has the advantage of reducing the information storage buffer. In the opposite case, when having to cache a lot of information, the delay will of course increase, and at the same time the static traffic load on the buffer devices will also increase. These two factors have a negative impact on the service quality requirements for real-time traffic.
- Another option is to use IP, but currently IPv4 has some serious disadvantages in terms of address space limitation and QoS failure. In contrast, ATM and its corresponding bit rate classes meet QoS requirements very well. One solution is that ATM and IP are combined for packet traffic, in which the IP protocol will be used on top of ATM. This combined solution will combine the advantages of both protocols: IP will ensure connectivity and ATM will ensure connection quality and routing. Due to the disadvantages of IPv4, the compromise solution is that in the 3G network, certain network elements use fixed IPv4 addresses, while the remaining subscriber traffic uses dynamically allocated IPv6 addresses. In this case, to adapt the 3G network to other networks, the 3G IP core network must have equipment to translate between IPv4 and IPv6 addresses because other networks may not support IPv6.
The core network nodes also need to be technically transformed. The circuit switching elements need to be able to handle both 2.5G and 3G subscribers. This requires changes in the MSC/VLR and HLR/AC/EIR. For example, the security mechanism during call setup is completely different in 2.5G and 3G networks and thus the circuit switching elements need to be upgraded to handle both cases. The packet switching elements will actually be upgraded.
from GPRS. In this case, the name remains the same as in 2.5G networks, but the functionality will be different. The biggest change for SGSNs is that their functionality is almost completely different from that in 2.5G networks. In 2.5G networks, the main function of SGSNs is mobility management for packet connections. In 3G networks, the mobility management function is divided between the RNC and the SGSN. This means that when a subscriber in a 3G network switches cells, the packet switching elements do not necessarily intervene, but the RNC has to manage this process.
3G networks deployed according to 3GPP R99 provide the same types of services as 2.5G networks. In this phase, most of the services are converted to packets when the application requires them. WAP is one of the candidates in this category, because in terms of the nature of the information transmitted, WAP is packet-switched. Packet-switched services are divided into service branches, in which each branch will include many different types of services and are services based on the subscriber location mechanism available in 3G networks.
The next steps after 3GPP R99 are not yet specific, but only general trends are identified. The main trends are the separation of the call connection, control and service parts, and the need to move the network towards a fully IP-based approach. From a service development perspective, these developments should enable 3G networks to provide good multimedia services, for example, services that combine voice and video simultaneously.
4.3.1.2. 3G solution according to 3GPP R4 standard
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Choosing Technology Suitable for the Conditions and Management Level of Our Country
CAME L | WAP | MEXE | USAT |
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Figure 4.3 3G network according to 3GPP R4 standard
In the 3GPP R4 phase, only the separation of the call connection part, the control part and the service part for the circuit-switched core network has been implemented. In this core network, subscriber data traffic will go through MGW (Media Gateways) which is the part that ensures connection and switching functions when required. This whole process is managed by an MSC Server upgraded from MSC/VLR. An MSC server can control many MGWs and thus the circuit-switched core network can be easily expanded. When the operator wants to increase the control capacity, they can set up another MSC server, and vice versa, when they want to increase the switching capacity, they can set up more MGWs.
Once a network has been established as above, the technological developments and requirements
The technical requirements will define the next frontier of this network. As IPv6 is increasingly deployed in 3G networks, the number of 3G connections that can be converted to IPv6 will increase, thus reducing the need for IPv4 to IPv6 migration. During this period, the traffic mix between circuit-switched and packet-switched data will change significantly. Most traffic will be packet-switched, and some traditional circuit-switched services, such as voice, will at least partially become packet-switched (VoIP, Voice over IP). For example, a traditional GSM call is replaced by a VoIP call over the MGW to which the BSS is connected. There are many ways to implement VoIP calls, but a new core network subsystem called IMS (IP Multimedia Subsystem) will be added because it will provide unified methods for handling VoIP calls. In addition, IMS will also be used for IP-based multimedia services. Of course, the BSS subsystem must also be upgraded to use IP, but the timing is still uncertain. In this case, the role of CAMEL will also change. Because many services using CAMEL are being moved from the circuit-switched network to the packet-switched network, at this stage, CAMEL must be established with the packet-switched network, and at the same time act as the connecting element between the service and the network.
4.3.1.3. 3G solution according to standard : 3GPP R5
Network Management System (NMS)
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Figure 4.4 3G network according to 3GPP R5 standard (all IP )
In 3GPP R5, the technology will continue to transition and all traffic in the 3G network will be IP traffic. For example, a call from a network terminal to the PSTN will have to be routed through the 3G network in packet form and from the GGSN the VoIP call will be routed through the IMS with switching functions to the PSTN.
From the mobile terminal point of view, the network has always been the same throughout its development. However, within the network itself, almost everything changes. The main change is first of all the transport technology, which in the 3GPP R99 implementation was ATM and later in 3GPP R4 and R5 moved to IP. Because the system needs to be backward compatible, the operator always has a choice to use either ATM or IP transport technology, or to have a solution for both. As explained earlier, ATM has the advantage of supporting QoS from the beginning, and later IP technology will have QoS guarantee mechanisms deployed not only for ATM but also for many different types of network subsystems.
At this stage, the service and the network become more important than the technology itself, and therefore the type of radio access technology used will become less important. The criterion for choosing the type of radio access technology to use is the ability to provide enough bandwidth for the required services. In the future, 3G core networks will have interfaces for several radio access technologies, such as GSM, EDGE, cdma-2000, W-CDMA and WLAN. This will naturally place many demands on terminal manufacturers and require the market to have terminals that can handle multiple types of radio access technologies. The 3G terminal will gradually become an inseparable object with many functions such as a phone, a wallet, an ID card and a passport, etc.
4.3.2 Selection of technology options and network solutions
Viettel will choose WCDMA technology (or UMTS) because of some of the following criteria:
UMTS is the 3G evolution of the GSM technology family (GSM, GPRS & EDGE), which is the only technology recognized by European countries for 3G networks. GSM and UMTS are also the technology lines that account for the largest market share in the mobile information market today (accounting for 85.4% according to GSA 8-2007).
UMTS is fully backward compatible with GSM. UMTS handsets typically support both GSM and UMTS modes so they can be used with existing GSM networks. If a UMTS subscriber leaves the UMTS coverage area and enters GSM coverage, the call is automatically transferred to the GSM network.
Thus: WCDMA is the only technology that currently has ready equipment, is produced by many equipment suppliers and can be provided immediately upon order. On the other hand, due to the large market size and being a "mature" technology,
Therefore, WCDMA is also one of the technologies with the lowest investment cost and the highest efficiency.
Viettel's current mobile network is GSM and has deployed GPRS. To take advantage of the 2.5G core network as well as the existing infrastructure, the technology chosen is WCDMA. In addition, WCDMA has a signaling network developed from the GSM-MAP protocol, so it will be convenient for backward compatibility with the GSM network.
For some countries in the world, they can choose to deploy first or deploy additional coverage with EDGE. In essence, EDGE with 8-PSK modulation technique allows transmission speed up to 384 kbps to satisfy ITU's 3G standard in some areas with high data rate demand. EDGE replaces GSM transmitters with simple EDGE radio transceivers, without affecting the overall network planning. But for Vietnam, deploying EDGE will complicate the planning and optimization of coverage. In addition, if EDGE is chosen to deploy, there will be terminals with too many modes, which is inconvenient for users. Thus, the terminal trend in Vietnam will be GSM/GPRS/WCDMA.
Initial network selection 3GPP R99 and future will be R4 and R5
The proposed 3G WCDMA network for Viettel is based on the 3GPP R99 version. Thus, this 3G network has both packet switching and circuit switching, so management is still complicated. However, many advanced countries in the world have deployed 3G, but voice traffic still accounts for the majority, so this plan will make the most of the old infrastructure for the dynamic digital market, which is still voice and medium data services.
But in the future, the goal is that 3G WCDMA will be an all-IP network implemented according to R4 and R5 standards.
When deploying 3G network according to R5 standard, there will be no more channel switching center but all will use IP packet switching. Only then can we take full advantage of the advantages and efficiency of packet switching technology in using transmission lines effectively and managing, charging...
But in addition to technical factors, there is also the factor of economic efficiency. We need to consider the deployment conditions when data traffic has surpassed voice traffic. And the conversion from IPv4 to IPv6 version still has many problems.
4.4 . Calculating parameters and constructing network structure
The construction of a WCDMA radio network is a very complex issue. When designing a network for a residential area, the designer must pay attention to many factors early on, such as: carefully estimating the ability to expand radio coverage to inner-city areas, service quality in different environments, spectrum efficiency and network growth potential. In the process of planning network operations, attention must be paid to issues of traffic distribution, deployment of large and small cells, provisioning for inner-city coverage and high bit rates, determining cell locations, site costs and other related environmental factors such as the presence of obstacles, buildings in the cell, etc.
4.4.1 . Some input assumptions for calculating the wireless network design :
4.4.1.1 Forecasting the demand for 3G network traffic development
Viettel network currently has over 25 million subscribers. It is forecasted that from now until 2010 the network will increase to about 35 million subscribers and by 2012 there will be about 50 million subscribers, of which the number of 3G subscribers will be about 10 million.