DEVELOPMET OF LOW COST WIDE AREA NETWORK IN INDONESIA

Onno W. Purbo, YC1DAV/VE3

Inter University Center on Microelectronics
Institute Technology Bandung
INDONESIA

Electronics and Components Lab.
Department of Electrical Engineering
Institute Technology Bandung
INDONESIA

Department of Electrical and Computer Engineering
University of Waterloo
Waterloo, Ontario
CANADA N2L 3G1

ABSTRACT

		Dalam tulisan ini, alternatif pendekatan untuk mengembangkan jaringan komputer wilayah luas menggunakan teknologi paket radio akan diketengahkan. Pendekatan ini dapat digunakan untuk membentuk jaringan komputer wilayah luas dengan biaya murah di Indonesia. Lapisan protokol yang digunakan akan dijelaskan secara garis besar. Usaha untuk membuat prototipe perangkat keras maupun lunak untuk keperluan ini akan dilaporkan. Prototipe ini meliputi perangkat berkecepatan rendah untuk para pemakai dan perangkat berkecepatan tinggi ini hubungan antar kota. Akhirnya, kemungkinan untuk bergabung dengan jaringan yang telah ada akan diperlihatkan.

		In this paper, an alternative approach to develop a wide area network based on low cost packet radio technology will be presented. This approach can be used to form a low cost wide are network in Indonesia. Different protocol layers to be used in the low cost wide are network will be briefly reviewed. Attempts to built prototype of low cost hardware and software to support the establishment of low cost wide area network will be reported. These include prototype of low speed hardware for the end users and prototype of high speed hardware for inter-city high speed trunks. Finally, possibilities to merge with the existing data communication services in Indonesia will be explored.

INTRODUCTION.

	In the last decade, computers start to emerge in Indonesia especially in the offices, industries, educational and research institutions. Needs of faster information facilities to cope with the pressures especially in the business world is growing. Different approaches have been or are being used to perform fast information exchanges. FAX machines are common in offices, Warung Telekomunikasi (WARTEL) etc. to be used for these purposes. However, more sophisticated integrated computer information systems are needed to accommodate the need of information.
	 Several attempts to form national data communication networks are being investigated. These attempts [1] include the development of Sistem Komunikasi Data Paket (SKDP) operated by PERUMTEL; Paket Satelit Network (PAKSATNET) by PT. INTI; University Network (UNINET) maintained by PUSILKOM-UI and Amateur Packet Radio Network (AMPRNet) operated by the Indonesian amateur radio operators as an international collaboration efforts [2]. Most of these services except AMPRNet use the long-distance phone facilities provided by PERUMTEL. These, unfortunately, require a relatively high operating cost as compare to AMPRNet. Thus, the adoption of packet radio technology in AMPRNet to be used in commercial world may yield a low cost Wide Area computer Network (WAN).
	In general, the network topology can be shown in Fig. 1. It basically integrates several Metropolitan Area Networks (MANs) in the cities via inter-city high-speed trunks to form a national Wide Area Network (WAN). Several Local Area Networks as well as end users can be directly connected to the Metropolitan Area Network. Except for the Local Area Network (LAN), packet radio may be used in WAN, MAN as well as end users. Integration with the existing commercial packet switched services, e.g., SKDP, PAKSATNET and AMPRNet, may also be performed in WAN or MAN levels.
	In this paper, I will describe the proposed low cost Wide Area Network based on packet radio technology. First, computer network architecture run on packet radio will be briefly reviewed. At this point, the use of TCP/IP protocol stack will be justified. Subsequently, attempts to built hardware and software prototypes to support the establishment of low cost WAN will be reported. Research works to built the prototypes will be partly funded by the Indonesian industries [3]. Finally, possibilities to integrate the with other services will be briefly explored [4].

BRIEF REVIEW ON PACKET RADIO NETWORK ARCHITECTURE.

	Network architecture used in packet radio technology can be described as seven protocol layers as shown in Fig. 2. As far as the protocol is concerned, this architecture is modular and one layer of protocol supposes to be independent with another. In general, most of the protocol layers used in packet radio network is the same as other network. The only difference is in physical and link layer protocol. In amateur packet radio network, AX.25 link layer protocol (derived from CCITT X.25 protocol) is used with radio (instead of cable) as the communication medium.
	In this research, DARPA TCP/IP protocol suite instead of X.75/X.224 ISO/OSI will be adopted. In a long run, we feel that it would benefit to adopt a defacto industrial standard protocol such as DARPA TCP/IP. We just recently sent copies of Request For Comments (RFC) describing the TCP/IP standard to several research institutions in Indonesia, e.g., Inter University Center on Microelectronics and Pusat Ilmu Komputer dan Sistem Informasi (PIKSI) both at Institute of Technology Bandung. The RFCs will be distributed to the interested parties on non-commercial basis. We hope this will broaden the understanding on TCP/IP based computer network in Indonesia.

ATTEMPTS TO BUILT LOW COST WAN PROTOTYPES.

	In this section, attempts to built the prototypes needed for the low cost WAN will be briefly reviewed. The main objectives in this project are:

      1.	To built simple hardware prototypes. To allow the microelectronics industries in Indonesia to adopt easily the technology.
      2.	To reduce the overhead cost to make it more attractive for end users.

Three different configurations will be attempted:

      1.	Low speed end-user's hardware and software.
      2.	High-speed prototypes for inter-city trunk.
      3.	Prototypes of LAN interconnection via packet radio.

	Figure 3. shows the typical station configuration for low speed (1200 baud) applications. It consists of a Terminal Node Controller (TNC) by which a microcomputer/computer will be connected to a radio transceiver. The TNC serves the role of link layer protocol (AX.25) and modem as part of the physical layer. The AX.25 link layer protocol is imbedded in an EPROM (Erasable Programmable Read Only Memory) to be run by a dedicated microprocessor in the TNC. The use of this configuration allows us to connect the TNC to various computers via its serial communication ports (similar to telephone modem). Unfortunately, the cost has to be sacrificed to gain this flexibility.
	It is reasonable to assume that most microcomputers used in Indonesia are PC compatible. Taking the advantage in the uniformity of hardware configuration, it would be reasonable to move the AX.25 link layer protocol in the TNC to the microcomputer. In other words, the only hardware added to the system is just a simple modem. This configuration is shown in Fig. 4. The modem itself is fairly simple in terms of design and components. It is a Bell 202 modem which can be constructed from a one chip modem such as Advance Micro Devices Am7910. We estimate a minimum cost in the range of $200 (excluding the microcomputer) may be achieved by using this configuration.
	For inter-city high speed trunk, we will be working on a microcomputer based inter-city back-bone. The main difficulties in realizing this kind of configuration is in the limited capabilities of the standard serial I/O port in the PC to achieve high speed operations. The maximum speed of the standard serial I/O port in PC is 19.5K baud. To overcome this problem, a special I/O card with buffering capabilities must be used. This I/O card will transfer the data directly to memory using Direct Memory Access (DMA) facilities in PC. This will allow us to operate a microcomputer at high speed (up to about 100K baud) without any significant problems. Typical configuration of inter-city high-speed trunk is shown in Fig. 5. A speed of 56K baud using Minimum Shift Keying (MSK) modulation will be used in our preliminary prototype adopting the technology used in amateur radio.
	Interconnection between different LANs via packet radio will be attempted. Typical configuration of LAN interconnection can be seen in Fig. 6. All protocol layers have to be used by the end users. At the microcomputers served as gateway between two different physical layer, up transport layer protocol is used. The main difficulty in interconnecting different LANs is no universal single link layer protocol. The link layer protocol will be depended on the used physical layer. In other words, we have to develop every device driver needed for each physical layer.

POSSIBILITIES TO INTEGRATE WITH OTHER SERVICES.

	As previously described, LAN interconnection via packet radio is possible. The use of layer protocols in the computer network will allow us to interconnect different computers via various physical layer. In terms of technological aspects, this only requires translation of data from one format to another and developing appropriate device driver to drive the hardware. This can be easily done taking the advantage in the modularity of the network protocol architecture.
	Our long term objectives are to integrate the low cost WAN with the existing packet switched network in Indonesia, e.g., SKDP and PAKSATNET. Typical interconnection among different data packet services can be seen in Fig. 7. Our current proposed projects [3] will be part of the development of small satellite systems at the Department of Electrical Engineering, Institute of Technology Bandung which will be partly funded by PERUMTEL.

SUMMARY.

	In this short paper, attempts to develop a low cost Wide Area Network in Indonesia have been presented. The low cost packet radio technology will be adopted to be used as the main vehicle to establish a low cost Wide Area Network in Indonesia. DARPA TCP/IP protocol suite will be adopted to integrate various Local Area Network into Wide Area Network. Attempts to built simple and low cost hardware prototypes have been described. These attempts will be partly funded by the Indonesian industries. Any questions regarding various aspects of the development of low cost Wide Area Network in Indonesia can be directed to:

	Onno W. Purbo
	Department of Electrical Engineering
	University of Waterloo
	Waterloo, Ontario
	CANADA N2L 3G1

	Dr. Adang Suwandi
	Department of Electrical Engineering
	Institute of Technology Bandung
	INDONESIA

	Dr. Kusmayanto Kadiman (director)
	Pusat Ilmu Komputer dan Sistem Informasi (PIKSI)
	Institute of Technology Bandung
	INDONESIA

	Ir. Achmad Fuad Mas'ud or
	Yudoyono Kartidjo MSc.
	Inter University Center on Microelectronics
	Institute of Technology Bandung
	INDONESIA

ACKNOWLEDGEMENTS.

	The author would like to thank Dr. Adang Suwandi, Dr. Kusmayanto Kadiman, Prof. Dr. Iskandar Alisyahbana, Yudoyono Kartidjo MSc, YB1AR, Ir. Ahmad Fuad Mas'ud and Ir. Suryono Adisoemarta, N5SNN at Institute of Technology Bandung, Indonesia. Ir. Robby Soebiakto, YB1BG at PT. Usaha Sistem Informasi (USI) IBM, Jakarta, Indonesia and the member of mikro-net for encouragement and fruitful discussions / suggestions during the course of the work.

REFERENCES.

[1]	Onno W. Purbo, "Jaringan komputer biaya murah menggunakan radio," KOMPAS 30 December 1990.

[2]	Onno W. Purbo, YC1DAV/VE3, "Sistem komunikasi data paket radio amatir," Majalah ELEKTRON, No. 38, pp. 3815-3820, 1990.

[3]	Onno W. Purbo and Adang Suwandi, "Perangkat jaringan komputer biaya murah menggunakan radio: sebuah proposal," Electronics and Components Lab., Department of Electrical Engineering, Institute of Technology Bandung, 1991.

[4]	Onno W. Purbo and Suryono Adisoemarta, "Teknologi satelit komunikasi komputer di amatir radio," submitted for publication in KOMPAS.

FIGURE CAPTIONS.

Figure 1.	The general topology of a Wide Area Network (WAN). Several Metropolitan Area Network (MAN) in the cities will be connected via inter-city high-speed trunks to form the WAN. Local Area Networks (LANs) in the office building can be connected to the MAN.

Figure 2.	The seven protocol layers as proposed in ISO/OSI. All of these protocol layers except the physical layer are written in software.

Figure 3.	Typical configuration of a packet radio station. The Terminal Node Controller (TNC) will control the link layer functions and connect the microcomputer to the radio.

Figure 4.	The proposed low cost end-user station assuming a PC compatible hardware is used in the microcomputer side. The link layer function will be moved to a program on PC.

Figure 5.	Typical station for inter-city high-speed trunk. The initial prototype will be geared on developing 56K baud modem and the high-speed I/O card.

Figure 6.	Typical configuration for interconnecting Local Area Network.

Figure 7.	Interconnection among various packet switched network to integrate Local Area Networks into Wide Area Network.

Figure 1.	The general topology of a Wide Area Network (WAN). Several Metropolitan Area Network (MAN) in the cities will be connected via inter-city high-speed trunks to form the WAN. Local Area Networks (LANs) in the office building can be connected to the MAN.

Figure 2.	The seven protocol layers as proposed in ISO/OSI. All of these protocol layers except the physical layer are written in software.

Figure 3.	Typical configuration of a packet radio station. The Terminal Node Controller (TNC) will control the link layer functions and connect the microcomputer to the radio.

Figure 4.	The proposed low cost end-user station assuming a PC compatible hardware is used in the microcomputer side. The link layer function will be moved to a program on PC.

Figure 5.	Typical station for inter-city high-speed trunk. The initial prototype will be geared on developing 56K baud modem and the high-speed I/O card.

Figure 6.	Typical configuration for interconnecting Local Area Network.

Figure 7.	Interconnection among various packet switched network to integrate Local Area Networks into Wide Area Network.