WLL and VSAT Integration

Characteristic study and potential customer requirement at remote area can be identified as follows:

• Potential customers who live in isolated village and often clustered in 50 to 500 customers for each cluster, or potential customer who live in identified area.
• Quite low line usage intensity for rural customers (0.025 to 0.2 Erlang per line)
• Voice traffic percentage that leaves local cluster can’t be predicted (varied between 20% to 80%).
• Terminal equipment has to be in line with rural environment: mountain range/not flat, has fast development capability, and low consumption power.
• Low consumption rate is important.
• Low infrastructure cost is also important: target cost per line is estimated around US$1.000 - 1.500, not including installation cost and satellite use cost.

Various technologies are available to provide basic telephone service to remote areas. The latest

LEO and MEO systems, microwave technology and VSAT networks can be designed for specific existing infrastructure. The key is to integrate WLL technology and VSAT to offer rural and thin population areas viable communications networks.

The right WLL cell coverage area is very depended on open field and population distribution. Based on field experience, there are 9 WLL models. These models (table 1) illustrated rural environment at various types of continents,  including forest, mountain, island, and flat land).

Table 1. Overview of rural customer density and topgraphy

Conclusion:

• Distribution and topography of rural customers are not affected by one real model in total population regulation, population density, and the requested line number.
• Customer distribution is not the same because mountain or river separates village cluster.
• Villages are served more efficiently and economically with microcell architecture (cell with base station range not more than 5 – 10 km). This contrasts with  macrocell, where range distance less than 30 km. *The examples of standard microcell are DECT and PHS. **The standard examples that provide macrocellular range are GSM, TDMA (IS-136) and CDMA (IS-95).

Table 2 illustrates the comparison of standard WLL. Several characteristics of rural environments showed that standard DECT was the best choice if it used microcell technology. First, DECT microcell base station showed that it was suited with general medium population range (20 – 200 customers) for remote area. 

Table 2. Comparison of standard WLL

Second, ‘non-compressed’ DECT (32 kbit/s ADPCM) voice information speed showed several flexibilities for VSAT and for delivering good voice quality via satellite link. In addition to that, DECT terminals have a low data complexity and consumption. Therefore DECT terminal are designed to conduct fast distribution and to make low cost  infrequent maintenance.

The last one, low electrical power demand on DECT is suitable for the rural environment that has minimal infrastructure.

VSAT technology selection is determined because of many demand similarities with standard WLL, as end user require lower rates and low intensity of telephone line use.

The customer’s cost per line (under US$1,500) for low-density customer is viewed from WLL and VSAT devices integration to have mininal cost.

 The largest cost reduction were provided by:

• Decreasing of output Base Station Controller function.
• Simplifying and decreasing the cost of local switching.
• Simplifying and decreasing cost from local switching into WLL/VSAT terminal in order to avoid satellite power and bandwidth use for local call.
• Terminal control function integration into the existing WLL and or BSC processors.
• Channel banks output and digital to analogue signal conversion.

Figure 1. Non-integrated DECT/VSAT component

DECT Interface Unit (DIU – base of integration attempts):

• Assignment of WLL channels, WLL/VSAT call control and processing.
• Voice compression for the satellite link.
• Management of DAMA control link with centralized network management system.
• Power distribution to the DECT base station and VSAT outdoor unit.

Figure 2. Integrated WLL/VSAT architecture

This integration will save 50%. Figure 2 illustrated the network architecture. It’s estimated that DIU-based terminal cost is under $1,000 per line for 180 customers’ population with low calling activity and generally under $1,500 for less than 50 customers with high calling activity.

Computers and communications—worlds previously isolated from one another—are converging and opening up integrated mobility solutions (terminal devices, networks, applications). In these terms, mobility pertains to terminal devices and users, free choice of networks, transparency of services, and universally available applications.

Integration and interaction of networks (internetworking) play an important role. The customer requirements must always be foremost in system design. Network integration demands high-quality communications, comprehensible billing methodologies and attention to installation and commissioning, user interfaces and security.
The global market volume for products and solutions in the telecommunications sector amounts to billions of dollars per year.  More than ²/₃ of all mobile radio traffic will take the form of data communications by 2005. Mobile computing and mobile multimedia will be commonplace by then. The spectrum of networks for mobile data communication extends from wireless LANs and DECT, via wireless WANs (e.g. GSM and AMPS, CDMA, MODACOM and MOBITEX), through to satellite networks using  satellite systems such as VSAT and LEOS.

The focal points of DECT and GSM applications differ according to subscriber density and range

Abbreviations and Definitions

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