Micro Radio Wave in SDH

Although in principle the optical fiber has become the medium of choice for long-haul transmission as well as from the standpoint of its capacity, SDH microwave radio is still required by many network planners. Main reason is related to economic issues, speeds deployment and security.
Economically, the SDH radio provides the most economical solution for network planners if the existing infrastructure (eg towers, shelters, power-plant and antenna feeder systems) that already exist can be used again when the permission through an area is already owned first. Also areas that do not match the terrain (like mountains or buildings across the water / dam) to make deployment of fiber is very expensive. The consideration is that for the implementation of a fiber network, the largest initial capital expenditure for intalasi fiber cables, which nature does not depend on its capacity.
The results of a joint economic study conducted by Northern Telecom (Nortel) and Stentor (an alliance of companies in the Canadian telephone operator), which aims to determine the design of the most cost-effective transmission network for installation along the 2000 km route, which is based on the required capacity and conditions -field conditions, showed that for the difficult environmental conditions, the radio is more cost effective for capacity up to 2.5 Gbps (equivalent to 16 x STM-1). For environmental conditions that are not heavy terrain, fiber networks become more cost effective for larger capacity than the 310 Mbps (equivalent to 2 x STM-1). Based on these studies, Stentor can optimize its design along the 6500 km network of large capacity synchronous Trans Canadian economically with the spread either through fiber or radio.
It should be noted here is that the comparative study of costs is based on fiber routes and the radio is single. However to meet the objectives of the availability of long-haul nature of the ITU-T, a dual route (dual) fiber (which means difersitas route) is required, which are generally to compensate for shrinkage / reduction of the cable, which occurs on average two to three times per year per route along the 1000 km. Please note that in designing telecommunication networks there is always a term of degradation / decrease in work quality cable and a variety of equipment due to aging, not least in the optical fiber. Each cutting wires can require up to 12 hours to repair. Compared with the routes of long-haul radios that can be designed for 99.98 percent availability for distances up to 6500 km, which if converted into less than two hours of down time per year by using a single route. Therefore, if the study is intended for comparison of single radio route versus multiple fiber routes, which provide the same availability of the network, the radio will have an advantage in terms of costs even in a larger capacity and the environmental conditions mentioned above.
In terms of speed of deployment, SDH radio offers a more rapid deployment and generate more income faster than the fiber, especially when the existing infrastructure can be reused.
Consequently, the practical deployment strategy for network planners is to spread the SDH radio network at first. Then, when the revenue / income for the company have been obtained, and capacity needed to rise, a fiber route and then propagated to obtain the various routes and network media and to put fiber to the higher capacity that are potential (approximately 10 Gbps) if desirable and possible.
In terms of security, the radio network, which consists of radio Sheltered site within every 40 to 60 km, is easier to secure than the fiber network. Fiber networks is more difficult to secure because the entire fiber route must be protected from various kinds of natural disturbances and nosy hands.

Reality in SDH Access

To provide lebarpita lower-level sub-2Mbps within the scope of SDH, some manufacturers provide access to the sound frequency at ADM 4 / 1 them to memultipleks and mendemultipleks E1 stream. It is not part of the SDH hierarchy and its nature is not different from pemultiplekan and pendemultiplekan an E1 stream provided by the PDH equipment.If desired the pemultiplekan first order to make a 64 kbps channel is always available for its users, some ADM 4 / 1 actually has a limited ability to cross-connect 1 / 0 (hierarchical relationship to 0 or 64 kbps to the first hierarchy or E1) to distribute and integrate the channel- canal into the streams E1 before pack it into the structure of the VC-12.Many engineers (engineer) networks assume that the DXC-DXC 1 / 0 is no longer needed, when the cross connection 1 / 0 can be made in its ADM. ADM-ADM if it is possible to meet the provision of small-scale series of 64 kbps, while they do not have the ability to cross connection or arrangement of the DXC 1 / 0, then the reliance solely on the ADM-ADM for cross connection can cause many problems for operators menyediaan SDH network services sub E-1.In planning the migration to SDH in full, the network operators should consider the two roles are taken by the DXC 1 / 0 in delivering services efficiently n x64 kbps over mixed network SDH / PDH: namely channeling and integrating the nx 64 kbps services into the access network and focus (hubbing) into the core transport network.DXC-owned high capacity 1 / 0 makes it very efficient to distribute and integrate the communication traffic of 64 kbps or nx 64 kbps before heading to the SDH network. Hubbing with DXC DXC-1 / 0 the transport network negating the need for a complete meshing in lane highway E1 over SDH transport networks to provide services sub-E1. DXC 1 / 0 can be used to break the facility into a level of E1 64 kbps DXC and repackage them for the next transmission. Deployment strategy DXC 1 / 0 in this way would also allow a network management system "sub-E1" are spread out in parallel with the overall management of the SDH system.ADM relationships in ring (a ring) in the SDH access layer can be viewed as an entity with the interface between E1 with 64 kbps channels with the ability to cross connect, but so can the ADM ring is viewed as a DXC 1 / 0?However the key difference between ADM rings that have the ability 1 / 0 and a DXC 1 / 0 is true is in terms of maximum capacity. Interface STM-1 (or STM-4, if available) will form a barrier that is bottle neck for the transport channels of 64 kbps through a hoop or ring. The limit is 1890 or 63 E1 channels. While the ring is unidirectional, this condition can not be made for the second time.What if a flexmux with integrated capabilities 1 / 0 is used in combination with an ADM 4 / 1? A flexmux memultipleks generally low bit rate and channels sound frequencies into multiple streams of E1, and may also be associated with E1 ports of an ADM 4 / 1. During a number of exit channels (outgoing) E1 in a flexmux limited to two or three, they should be filled as completely as possible. This incorporation may be formed using cross-connection capabilities of its flexmux, namely an entrance channel (frequency noise) is placed into the stream of E1 is given to the ADM 4 / 1.Ability 1 / 0 in the ADM 4 / 1 and flexmuxnya used to integrate the communication traffic towards the high end of its network. However, ring ADM 4 / 1 will act as a DXC 1 / 0 only in the following cases:

    * ADM 4 / 1 has the ability DXC 1 / 0 non-blocking between tributary E1 and 63 E1 streams are packaged in STM-1 stream is done via the ADM 4/1-nya.
    * A number of E1 in a virtual tributary cross-connect does not exceed 63.
    * Ability 1 / 0 is used to integrate the traffic at the level of access in terms of the network.

Service Implication of SDH

To maximize the advantages of SDH technology that can be achieved, it is necessary to consider the different layers that exist in a telecommunications network. There are two layers of network transport services on a multipurpose network, which provides a service SDH transport stream of bits that are transparent. This means that the transport network itself is not aware of the contents of the payload is carried from A to B (for example, whether a telecommunications line is carrying voice or data).
Applications of new customers and services with added value appears on the network layer services at a higher level and can take forms that are difficult to predict (such as multimedia applications). The bottom of the second layer of these services generally include networks of basic services and network-specific overlay network service. -service networks is an area of ​​evolution is more predictable. Networks of basic services include applications, voice, ISDN and mobile radio (mobile), such as GSM, given overlay networks for specific services (for example 64 kbps leased lines provided to customers the company / industry) . Patterns of growth in voice traffic (phone) are generally stable, but the services is growing rapidly as GSM in some cases require the development of the transport network overlay on top throughout and multipurpose tissue. Under normal conditions, the characteristics that it has become the nature of an existing network should have to make this overlay, which is more an exception than a necessity.
When a new service is introduced through a vast geographical area, it is certainly not necessary to double overlay networks to be designed and implemented. Proper network planning at the early stages of a project can guarantee that a network of multipurpose transport will initially be able to connect the majority of potential customers.
New services can also be associated with applications of the intelligent network (IN: Intelligent Network), data network or mobile network (mobile). Not like the layers of services, the evolution of transport network layer is rather difficult to predict, but generally can be characterized by overall growth conditions are slowly, with a phase which is periodic of rapid growth.

PDH to SDH Evolution Strategy

Because the SDH transmission format is designed to overcome the limitations of PDH, then all the telecom companies are challenged to introduce into the SDH transmission network, PDH networks they already get up first. Important issue is the question of balance between the advantages offered by SDH and cost barriers in network investment. This requires a strategy on network evolution from PDH to SDH.
There are three main alternatives, each of which has its advantages and disadvantages. Telecommunications company may need to adopt a mixed strategy as the best answer for each of the environmental conditions.
Three alternatives are:

    * Top-down (the method level or layer)
    Bottom-up (method of islands or branch)
    * Parallel (overlay method)
Coating methods particularly relevant to the company's telecommunications services are still introduced at the level of digitalization of its network trunk or for those who need to support new services in layers over top of the inter-urban networks (as an example for the connection MAN-MAN )
The main aim is cost savings for large transport capacity in dealing with the growth of communications traffic. In the introduction to this strategy begins at the level of SDH backbone / supernode level with a few nodes are connected with systems of STM-16 or SDH STM-4. Interconnection to a PDH network is a gateway (gate contact), generally at the cross connect ports and the supply port cross-connect ports adequate to support all the functionality required PDH and SDH. This is an important aspect of network planning.
The following step is to change the layers of the lower subsequent to the SDH, and move its gateway to the point where the advantages of SDH most can be guaranteed. Thus, SDH provides full advantage of the layers of higher and selectively in layers lower.
Strategy with the island method is to install the SDH network nodes at the middle level and lower level, namely providing SDH islands for a particular community (for example, centers of trade and financial). With a layer approach, it takes a gateway-gateway for PDH networks.
At this level, some of the main cross-connect products will be broadband (wideband), menginterkoneksi systems STM-1 transport through interfaces of 155 Mbps (or 140 Mbps via a gateway interface), with channeling and combining facilities in VC level 1, 2 and 3 are carried in a speed of 2 Mbps or 1.5 Mbps.
Through the parallel method, SDH installed in an overlay network (which is overlaid) in addition to its PDH network in a few knots. The goal is to implement certain new services (such as videoconferencing and LAN interconnection / LAN) as well as benefit from all functions of SDH as soon as possible, and provide improvements in terms of quality.
Gateway for PDH networks are still needed, although there is segregation (separation) between the services between the old and new facilities SDH and PDH. It is also important that all the equipment necessary to provide full functionality in SDH SDH is overlaid is already installed.
This strategy is attractive to telecom companies with a traffic growth of rapid communication, and for those who wish to add functionality SDH (for example, to offer premium services; the caller / caller being charged pulses with special rates, which are usually applied to services information) as they increase their network capacity

SDH Network Architecture

SDH network architecture in general is as shown in Figure 5. The highest level, SDH transport network is nx STM-1 (nx 155 Mbps), which is crossed by the equipment connected DXC 4 / 4 (Digital Cross Connect). Brief description of the DXC is as follows: in digital telecommunications, digital signals are directed or routed to a central location-the telephone exchange called this DXC. DXC this serves to provide a place for interconnection relations wire line (hardwire) as well as routine maintenance and troubleshooting it. Each type of digital signal has its own digital penyakelar, for example at the DS-1 digital signal at 1.544 Mbps are called DXC-1, DS-4 at 274.176 Mbps called DXC-4. DXC 4 / 4 means a liaison between

Indonesian - detected to English translation

fellow at the network hierarchy to pemultiplekan 4.

The main task of the network is to provide a large trunk capacity between the central telephone exchange with the DXC-4 / 4 to allow for rapid restoration of connections if a node crashed or failed to function (impaired).

By using DXC 4 / 4 and the line terminal equipment to nx STM-1 (nx 155 Mbps), the smallest lebarpita handled by the transport network, granularitasnya (one of the canals before pemultiplekan) is an STM-1 (equivalent to 63 channels x 2 Mbps, or 1890 x 64 kbps). Fell further down the network hierarchy, DXC 4 / 1 (liaison with the hierarchy of the hierarchy to 4 to 1) break lebarpita STM-1 to the level of VC-12 (carrying E1). Each VC-12 can be individually routed to the node DXC 4 / 1 other or into the access network.

Through a combination of DXC 4 / 4 and 4 / 1, the granularity of the transport network to be E1 or 2 Mbps (for American T1 = 1.544 Mbps). A DXC 4 / 1 is used to provide granularity of VC-12 (E1) between layers of transport and access layers.

SDH access network are generally arranged in a ring-ring (ring forms) STM-1. ADM 4 / 1 (Add and Drop Multiplexer) for STM-1 mendemultiplek flow into streams E1, or E1 memultiplek flow into the stream STM-1 (hierarchy into the hierarchy to 4 with 1). E1 streams are being provided to end users through a standard interface G.703.

Referring to Figure 5, as mentioned above, the SDH network is divided into two layers (layer); transport layer and access layer. Transport layer consists of equipment located in the central DXC-telephone and high-capacity connections between the central-telephone exchange. Medium access layer consists of ADM equipment located in the central telephone exchange, or cabinets in the street, which is a provider of channel lebarpita for end users.

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SDH Hierarchy

Before the advent of SDH, the hierarchy of digital signal multiplexer to America / Canada, Japan and Europe differ as stated in Table 1. With the SDH hierarchy becomes uniform as shown in Figure 1.
 

Tabel 1. Hirarki sinyal digital di Amerika, Jepang dan Eropa

Level hirarki ke:	Amerika/kanada (Mbps)	Jepang (Mbps)	Eropa (Mbps)
1 2 3 4 5	1,544 6,312 44,736 274,176 -	1,544 6,312 32,064 97,728 397,200	2,048 2,442 34,368 139,264 560,840

Dari Gambar 1 tersebut terlihat bahwa pada level atau tingkat yang paling tinggi, SDH transport network is a network nx STM-1 (nx 155 Mbps).

STM-1 (Synchronous Transport Module) is a synchronous transport module level-1. A single frame of STM-1 is expressed by a matrix consisting of nine rows and 270 columns. These frames are formed of 2430 bytes, each byte consists of 8 bits. STM-1 frame contains two parts, the SOH (Section Overhead) and the VC (Virtual Container) which is its payload. Figure 2 states STM-1 frame structure, Figure 3 states the structure of his VC,sedang Gambar 4 menyatakan alokasi byte pada SOH.
SOH provides information between the two LTE (Line Terminating Equipment) of frame alignment, monitoring the BER (Bit Error Rate) and the transfer of information between the two LTE and so on. While the VC is used for transporting signals its tributary (individual input signals are fed to the multiplexer) through a pathway. Each VC consists of a POH (Path Overhead) and a
Container. POH seperti tercantum dalam Gambar 2 carry information between the points and disasembly asembly as parity checks, labeling channels, alarm monitoring, and performance monitoring. A container carrying tributary signals, is a pointer showing the location of the first bit her on the VC.

Introduction of SDH Technology

Synchronous Digital Hierarchy (SDH) is a hierarchy pemultiplekan based on synchronous transmission that has been defined by CCITT (ITU-T). In the world of telecommunications, pemultiplekan series of signals in the transmission poses problems in terms of branching and insertion (drop and insert) that is not easy, and limitations to monitor and control the transmission network.
Before the emergence of SDH, the existing transmission standard known as PDH (Plesiochronous Digital Hierarchy), which has long been defined by CCITT. A network does not synchronize plesiochronous network but using only pulses beat (clock) that is very accurate in all the nodes penyakelarnya (switching nodes) so that the rate of slip between the various nodes are quite small and still be acceptable (eg plus / minus 50 bits or 5x10 -5 to network / channel 2.048 or 1.544 Mbps). This mode of operation such as this may indeed be a most simple implementations because they are avoiding the distribution of timing throughout the network.
It turns out that PDH is not so well suited to support the development of control techniques and signal processing for today are increasingly needed by companies of telecommunications service providers. In PDH, a certain transmission equipment generally only deal with either one specific function within the network, while in a SDH, there is the integration of various types of different equipment that can provide new freedom in designing the network. It's not a new news that the SDH can be used for large capacity optical transmission, traffic regulation and restoration of communications networks.
SDH has two main advantages: flexibility so high in terms of channel configurations on both nodes network and improve network management capabilities for both its payload traffic and network elements. Taken together, these conditions will allow the network to be developed from the passive transport structures in the PDH into other tissues that actively transports and organize information.
Specific offers are created by the SDH of which include:

    * Self-healing; the redirection (rerouting) communication traffic automatically without interruption of service.
    * Service on demand; provision of rapid end-to-end customer services on demand.
    * Access is flexible; flexible management of various lebarpita remains to places customers.
SDH standards also help the creation of an open network structure, much needed in today's competitive scope for companies of telecommunications service providers.

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