Debabrata Sarddar et. al. / (IJCSE) International Journal on Computer Science and Engineering Vol. 02, No. 06, 2010, 2047-2052 Abstract— Recent research in wireless communications technologies has focused to the development of Next-generation wireless systems (NGWS) which integrate various existing wireless networks technologies, each of which is optimized for some specific services such as WLANs, WiMAX, General Packet Radio Service (GPRS) and Universal Mobile Telecommunications System (UMTS). The most important and challenging issue is to realize seamless handoffs with small handoff latency and packet loss to ensure the Quality of Service (QoS) in NGWS. In this paper, we propose a handoff management architecture using relative signal strength of the present and neighboring base stations to calculate the handoff initiation time. To take the right decision of handoff initiation time we use mobile’s speed, handoff signaling delay information and also the size of the present and neighboring cell and reduce the errors associated with them. The performance analysis shows that the approach ensures successful handoff and reduces call blocking probability. Index Terms— Next Generation Wireless Systems (NGWS), Handoff, Handoff latency, BS (Base Station), MT (Mobile Terminal), Relative signal strength. HMIP (Hierarchical Mobile IP). I. INTRODUCTION In order to achieve continuous communication during the mobile terminal’s mobility the active call should be transferred from one cell to another potential cell. Transition of an active call from one cell to another can be assumed to be the proper definition of hand-off/hand-over process. The transfer of a current communication channel could be in terms of a time slot, frequency band, or a code word to a new base station (BS) [1-4]. A new BS assigns one of unoccupied channels for the hand-off process. However, if all of the channels are in use at the handoff time there are two possibilities: To drop the call or to delay it for a while. Different handoff techniques are proposed in literature and two of the most important metrics for evaluating a handoff technique are forced termination probability and call blocking probability. In recent literatures, though many works are available in reducing hand-off failure probability by decreasing latency and execution times, there is no approach for incorporating error factors in the expression thereby ensuring hand-off success. We propose such a scheme here. I.1Handoff Initiation It is essential to be very precise on the time of requisition for hand-off process. Otherwise unnecessary calculations need to be performed and this will result wastage of resources. Handoff initiation is the process of deciding when to send a request for handoff. Handoff decision is based on the received signal strengths (RSS) from the current BS and neighboring BSs. In Fig. 1, we examine the RSSs of the current BS (BS1) and one neighboring BS (BS2). The RSS gets weaker as the MS moves away from BS1 and gets stronger as it gets closer to BS2 as a result of signal propagation characteristics. The received signal is averaged over time using an averaging window to remove momentary fading due to geographical and environmental factors [1-2]. Below, we will examine the four main handoff initiation techniques mentioned in [2-3]: relative signal strength, relative signal strength with threshold, relative signal strength with hysteresis, and relative signal strength with hysteresis and threshold. Reduction of Error in Handoff Initiation Time Calculation for Next-Generation Wireless Systems Debabrata Sarddar 1 , Arnab Raha 1 , Tapas Jana 2 , Shovan Maity 1 , Utpal Biswas 3 , M.K. Naskar 1 1. Department of Electronics and Telecommunication Engg, Jadavpur University, Kolkata – 700032. E-mail: 2. Department of Electronics and Communication Engg, Netaji Subhash Engg College, Techno City, Garia, Kolkata – 700152. 3. Department of Computer Science and Engg, University of Kalyani, Nadia, West Bengal, Pin –741235. ISSN : 0975-3397 2047