The Quality of Internet Backhaul Link with WLAN 802.11b between The Access Point of Pathuk Area Towards The 12 Stations in Yogyakarta Seen from Its Latency Sutiyo 1 , Wahyu Dewanto 2 , Sujoko Sumaryono 3 1 Departement of Electrical Engineering, Faculty Of Enginnering, Widya Dharma University, Klaten, Central Java 2,3 Departement of Electrical Engineering, Faculty Of Enginnering, Gajah Mada University, Yogyakarta, Indonesia E-mail : tio@unwidha.ac.id Abstract— Destructive interference between WLAN (Wireless Local Area Network) 2.4 GHz devices that result in decreased quality of data transfer is a major problem in using wireless technology for (media) data communication. This problem arises because the minimum management or coordination of the use of frequency 2.4 GHz for data communication, particularly in outdoor use, although there has been government regulation through the Ministerial Decree No. 2 in 2005. This research activity is to measure the value of the latency of a system of Internet Backhaul Link, the system consists of the Access Point located in Bukit Pathuk, Yogyakarta and 12 stations scattered in the region of Yogyakarta, Yogyakarta region of southern, eastern, central, north and west. Latency data obtained and were logging in graphical form. WLAN 802.11b interference levels in Yogyakarta, especially the middle or the city is already high. Fifty percent (50%) from the 12 stations has a High interference levels or a set of six stations, and 33.33% have a Medium level of interference, and 16.67% have a Low interference level. Connectivity level also varies; about 33.33% has level above Medium, and 66.67% has level below Low and 8.33% has level Lost. Keywords-- wireless, 802.11b, interference, latency, backhaul, link I. INTRODUCTION WLAN 2.4 GHz technology has advantages in terms of economical reason, but in terms of technology, the frequency 2.4 GHz has limitations. This field of frequency is also used for ISM (Industrial, Scientific and Medical). Consequently, any service that uses this frequency field are vulnerable to have an interference from other devices of ISM[10]. The use of this frequency field will be optimal if all the devices used have limited resources and similarity. When the transmit power is lifted, it will interfere other transmitters in different locations. Frequency interference causes the decline in the performance of each device. Performance reduction of the devices influence the quality of data transfer or tighten the bandwidth. The quality of service is embodied in the data transfer rate or the amount of latency or ping time delay between the access point to the station. The narrow bandwidth can affect the latency of the wireless connection device, it was a subject matter being studied. Research on the frequency 3.5 GHz interference has been done by Mustofa [5], the radio frequency spectrum is a natural resources which are limited. Spectrum allocation planning is needed well in optimizing the use, one of which is the frequency of sharing. It was also mentioned by the researchers that the lack of consideration of technical and regulatory bodies unpreparedness may cause interference problems. Structuring the use of radio frequency spectrum should be related made more efficient and optimum[8]. This provides the opportunity for academics to provide input concerning with the regulation of the adoption of the frequency spectrum. POSTEL Policy (Post and Telecommunications) as well as the additional information in this research. II. LITERATURE REVIEW A. Backaul Link Backhaul link is a communication facility with high capacity that connects the main node or main network with different sub-nodes or sub-sub-network and even with global telecommunication network[2]. In a world of information technology backhaul links also called backbone or core network. One application backhaul link is to connect the nodes of BTS (Base Transceiver Station) mobile cellular base stations to each other, connecting the BTS to the mobile telephone exchange, connecting the cellular provider with another cellular provider. Backhaul link has a very important role in terms of maintaining the quality of service of telecommunication systems. Backhaul links are generally created in the system point to point to get a high bandwidth throughput of the devices backaul link which is used. In choosing a backhaul technology, we must consider parameters such as capacity, cost, and the need for resources such as the frequency spectrum, license, availability of devices [3]. Media backbone such as FO (Fiber Optic), VSAT (Very Small Aperture Terminal), Microwave, Radio Link. Fiber optics is the backbone of the most powerful medium because it has the quality of data transfer or high of bandwidth throughput, but the application require an expensive cost. Backbone with wireless media such as Microwave, Radio Link, WLAN, WiMAX (Worldwide Interoperability for Microwave Access) is a media that in general is the easiest to apply in the construction of a backbone of a telecommunications system, in addition to more affordable price and it is also easier to install, but many problems arise when the use of wireless technologies which is not governed or coordinated, the problem is about frequency interference. The model of backhaul links is shown in Figure 1. ICITEE 2011 Technical ISSN: 2088-6578 Gadjah Mada University Yogyakarta, 28 July 2011 69