Integrate SDH and ATM to optimize 3G Transmission Network

3G era brings more challenges
The arrival of the 3G era poses a huge challenge to operators, such as immature technology, limited funds, and uncertainty in market demand. In addition, operators must also provide high-quality and inexpensive 3G services, while ensuring network scalability and reducing network investment and operation costs. Due to the uncertainty of 3G development, therefore, the network to be built must be a cost-effective and flexible network. Currently, 3G is not used, which will not waste a lot of investment resources. However, if 3G business grows on a large scale, the existing network can quickly and effectively provide the required services.
The access part of the 3G transmission network has two completely different technologies: Transmission and ATM. The traditional network structure divides them into two different network layers. Although the network design is simple, however, the network is complicated, expensive, and inflexible. To meet the real needs of users, ECI proposes an innovative concept: Integrating SDH and ATM on the same platform optimizes the network, making the network more flexible and economical, and more scalable.
Role of ATM in 3G
Node B and RNC in 3G are connected through the Iub interface. The Iub interface is a complex protocol family and is based on the media, signaling, OAM, and so on the ATM. The ATM can transmit data through the TDM link, most Node B nodes contain 2 M or several 2 M based on ATM IMA, while RNC nodes often have multiple 2 M or STM-1.
The early 3G standard defines that Node B and RNC are connected through the TDM circuit. On the ATM layer, Node B and RNC are directly connected through the ATM link without ATM switching. The following functions are provided:
A. independent from the transport layer
B. Define multiple TDM links into one logical circuit through the ATM IMA mechanism. c. ATM statistics Reuse
3G standard version 4 defines the ATM switching and QoS Assurance, ATM switching has two benefits: RNC can be a STM-1 interface, greatly reducing the cost of RNC; improve bandwidth utilization.
The ATM switch can ensure bandwidth allocation, reuse statistics based on the peak value and constant rate, and reuse statistics based on users, thus improving the network bandwidth utilization.
Bandwidth savings greatly reduce costs. Whether you use leased lines or frequency resources to build a 3G transmission network, the bandwidth savings are reduced for the operation costs, bandwidth is small, this means that the network scale can be reduced, and the corresponding operation and maintenance costs can be greatly reduced.
3G transmission network deployment
You can build a 3G transmission network in two ways:
1. The E1 interface of the RNC Node is connected to Node B through the SDH network of TDM only.
2. RNC Node is STM-1 interface, Node B is E1 interface, ATM switch is used for E1 to STM-1 convergence, ATM switch can be placed at the RNC Node, can also be placed in other locations in the transmission network.
ATM switches are required in 3G transmission networks, but they are also expensive, Because ATM itself is an expensive technology. In addition, installing an ATM switch not only adds ATM devices, in addition, a large number of PDH and SDH interfaces are required, and the typical configuration of Node B nodes converge to the channel of STM-1 (52 E1) and the local Node B Node 20 E1.
The total number of ATM E1 is 72, so a channel of STM-1 is not enough, the convergence of the ATM layer, if only the convergence of TDM, need another STM-1, there are only nine E1 in the other STM-1, and the waste is obvious. But the ATM switch can compress 72 ATM E1 to a VC4, the ATM switch needs a STM-1 interface and 72 E1 interfaces, at the same time SDH network also needs to add a STM-1 interface and 72 E1 interface, obviously is an expensive solution, not suitable for 3G transmission network applications.
IMA is the formation protocol for transmitting ATMs over multiple E1 links. Multiple physical links are configured as one ATM link, which does not affect the upstream and downstream business circuits. This is a powerful function, however, IMA is implemented on the hardware layer. Therefore, all links to the same IMA group must be on the same interface card. However, in many cases, it is difficult to allocate the IMA group to the same interface card, all E1 instances in the same IMA group must be processed by the same ASIC chip.
This restriction makes network planning almost impossible. If the mobile operator assigns the E1 link to the IMA group, it cannot plan future expansion. If there is no margin for expansion in advance, in the future, the expansion of IMA and its complexity will affect the business. If there is a large margin, leading to a large amount of upfront investment, there is a risk of investment waste. ECI 3G Transmission Network Solution
Mobile communication has always been an important strategic market for ECI. To address the needs of the Mobile 3G transmission market for ATM services, ECI has proposed a solution on a single XDM platform of ECI, integrated with SDH and ATM functions, it features high cost performance, flexibility, and 3G scalability.
XDM is an MSTP platform designed by ECI for mobile and metro networks. It supports various TDM applications and pure optical applications. It also features a fully VC12-Based Cross matrix of XDM, it can ensure unlimited cross-linking between any E1, which is very beneficial to ATM applications.
Eci atm card: ATS card, which is connected to the cross matrix of XDM and has no physical interface. It is actually an ATM switch and supports three types of ATM ports:
1. VC4 in the STM-1 or VC4 in any high-order virtual container
2. Physical E1 port or E1 channel in any interface
3. Multi-E1 IMA Group
On the ATM layer, the ATM service between any ports can be exchanged without restrictions.
Remote through the STM-1 to 52 E1, local there are 20 E1, using external ATM switch mode, ATM and SDH Equipment must provide a STM-1 interface and 72 E1 interface, if the ATS scheme is adopted, the crossover matrix will cross 52 E1 in the remote STM-1 and 20 E1 in the local to the ATS card, and the ATS card will converge 72 E1 to a VC4, the crossover matrix then cross this VC4 to the STM-1 port. It is obviously more economical and flexible for a single device to complete SDH and ATM functions at the same time.
The integrated SDH/ATM solution of XDM is more compact, flexible, economic, and easy to manage.
The integration of ATM and SDH greatly simplifies hardware devices. When SDH and ATM are used, cables need to be connected between devices. The integration technology can save the connection cable, the ATS card does not have physical interfaces, so a single card can support 126 high-density interfaces (up to 84 IMA groups ). The ATM switch does not have such a high port density.
The integration solution has only one management system, which reduces operating costs and only one hardware, reduces equipment footprint, reduces power consumption, and reduces connection and cable costs.
The planning of the IMA group is a complex project. If you only consider the current requirements of the ATM E1 at the beginning, the future expansion may change the cable connection, which is not allowed, therefore, the E1 port must be set aside for future expansion, but the uncertainty of future expansion is a risk. The ATS card in XDM is an ideal solution. Unlike traditional ATM switches, ATS cards can converge different E1 cards on different PDH cards into an IMA group. In the traditional ATM switch solution, some ATM E1 interfaces must be reserved for future resizing. For the ATS scheme, new ATM E1 interfaces only need to be connected to the PDH E1 interface of XDM in the future, XDM can cross the ATM E1 on different PDH cards to their destination.
When planning a network, cost is the primary factor. Network Planning should not be regarded as expenditure, but also mean to generate benefits, the ideal network planning should meet users' needs while generating the largest return on investment, that is, to achieve optimal design with the minimum cost. There are more uncertainties in 3G network planning and it is difficult to predict future development. Therefore, 3G network planning should consider the possibility of optimism or pessimism in the future, therefore, we should consider the following from the perspective of cost flexibility:
First, design a network that is easy to demonstrate and use in a small scale. When the demand increases, the network upgrade can meet the new requirements of users. However, in practice, it is difficult to find the best solution; when measuring the cost of a network, cost flexibility is a very important factor. Therefore, the focus is not on the relationship between network capacity and demand, but on the relationship between network cost and investment return, the cost of the network should be compensated by the benefits of the network. Even if the original prediction is correct, the actual demand will often lag behind the original prediction. In any case, should not affect the benefits.
We often encounter the following dilemma: either the initial construction of a network with the lowest configuration will be expensive for future upgrades, or the construction of a network with a large reserved capacity, it will be a high cost in the initial stage.
XDM is a platform built upon your growth and paid for as you grow, while ATS is just a board of XDM. Adding ATM applications on the network only adds ATS cards, the increase is very low, so the investment cost in the initial stage is very low, and the cost of future expansion is also very low. When the ATM service changes, you do not need to consider configuring large-capacity ATM switches, simply consider adding several ATS boards.
Comprehensive application of 2G and 3G services
A philosopher once said, "No one is isolated." This sentence also means that no network is isolated.
When discussing 3G transmission networks, there is another important question: how do 2G networks and 3G networks share resources? This is not only a technical issue, but also an economic issue. To reduce costs, 3G networks must share network resources with existing 2G networks.
2g tdm services are transmitted in standard TDM links. The full low-level cross matrix of XDM is suitable for mobile networks and provides a flexible and convenient 2g solution. At the same time, the ATS card aggregates the ATM services of multiple Node B nodes into the IMA group. The 3G IMA group and the 2G TDM Service share in the same channel STM-1 link, network management can be used to allocate bandwidth between two networks.
Currently, the construction of a 3G transmission network is an arduous challenge. The technical problems are basically solved, but the implementation is still a problem mainly based on the following reasons: network structure and operation costs, business types, network layer division, changes in the number of users and bandwidth requirements for each user.
XDM's ATS is an innovative design that integrates SDH and ATM technologies to provide a powerful and economical solution for 3G transmission networks. The integration of the two technologies greatly reduces the cost of the network and provides great flexibility for the network. It is suitable for various trends in network development and meets the needs of increasing user and capacity.
XDM's ATS solution is not only an economic network solution, but also a completely scalable solution. Mobile operators do not have to invest in unclear future demands today, at the same time, when demand increases, the existing network can be upgraded without restrictions.