To minimize false handoff probability as described in  we have here in Figure 6. AB is the side of regular hexagonal cell served by the Old BS (OBS). But A’B’ is the common cord of the two adjoining cells, one served by the OBS and the other by the NBS. When a MS crosses A’B’, then it will be under the New BS (NBS). This is because RSS of NBS is greater than RSS of OBS to the right side of A’B’. Once the MT reaches the boundary of the circular cell (real) then the MT discovers that it may enter into the coverage area. Here, we have considered some hexagonal portion to be overlapping. MT is moving from its current serving BS (old BS), to the future serving BS (new BS).
Different radio access technologies present distinct characteristics in terms of mobility management, security support, and QoS . To achieve seamless mobility and end-to- end QoS guarantee for the users, these issues should be carefully addressed while developing the in networking and handoff schemes of Wireless mesh networks with various wireless networks. Mesh routers in the WMNs play an important role. 802.16 base station (BS) functions can be integrated into one mesh router. When an Mobile node switches the network interface, only the link type is changed between the MN and mesh routers, and the MN still connects to the same mesh router. In this case, the traditional mobility management such as Mobile IP leads to a large handoff delay with too much signaling cost. Thus to achieve fast and seamlesshandoff, a new handoff scheme should be considered.
In the interworking of heterogeneous network, lone of the main challenge is seamless vertical handoff. A number of issues should be considered such as handoff metrics, handoff decision algorithms and administration in classify to attain seamlesshandoff. Vertical handoff, the major handoff metric is the received signal strength. Handover, in vertical handoff, simply the received signal strength is not adequate to make a handoff decision. The handoff metrics may well include cost of service, available bandwidth, power requirements, quality of service, and user preference. The vertical handoff could not take leave only at the cell boundary. It can take place at any time, depending on the network condition and user predilection. Such collective metrics guide to a challenge for scheming a handoff decision algorithm since some factor are more difficult to gain than the material level parameters such as received signal strength (RSS) and signal-to-interference ratio.
Abstract— The integration of WiMAX and WLAN has been seen as a promising approach towards fourth generation (4G). Vertical handoff plays important role while integration of WiMAX and WLAN heterogeneous overlay systems. Vertical handoff is preformed on the basis of Quality of Service (QoS) metrics of the two heterogeneous networks. A Seamlesshandoff scheme is based on the tightly coupled architecture so that undesirable signaling cost induced by the mobile Internet protocol can be avoided with aim to provide always best QoS for the users (mobile and fixed). By using the ad-hoc on demand multipath distance vector protocol a simple evaluation algorithm is used to measure the QoS metrics such as available bandwidth and packet delay of both mobile and fixed users. The proposed scheme can keep the users always being best connected.
In the present time, key to provide mobile users with required QoS will be seamlesshandoff between homogenous or heterogeneous wireless access networks. Also the continuation of user application should not be compromised. Generally handover bring up the process of transferring an active call or data session from one cell in a cellular network to another. There are many reasons to perform handover between three cellular networks, and the most important reason is to deliver uninterrupted service to a user [12, 13]. There are some rules to initialize the handoff and it can be divided into two types:
In this research work we have formed a heterogeneous network by integrating two different networks (WLAN and WiMAX) and presented a vertical handoff scheme using ASN –GW. For performance evaluation VoIP application is chosen and we have also taken node mobility into account. An attempt was made to provide seamlesshandoff in the network. We have done addition of the QOS Profiles (RSVP, PQ, RED, CQ) at the interface of ASN gateway which resulted in the improvement over the existing handoff techniques .Close observation reveal that application of RED resulted in low jitter, applications that require best quality of voice at the destination should use PQ as it gives consistent improved voice quality. RED is also the optimum choice for those real time applications that are delay sensitive. No matter speed of mobile nodes increase RED will provide the minimum end to end delay. If the application is required to have high throughput then RSVP is the best choice as it reserves resources such as bandwidth etc in advance, thus gives us good performance in terms of throughput.
Historically, when a seamless shaped textile product was needed, cutting and sewing was required. There are a number of adverse consequences caused from utilizing seams in a textile product. First, the process of cutting and sewing is the most labor intensive step in the formation of a product. Second, the sewing process can also create needle holes in the fabric as well as damage the fiber within the yarn. The presence of needle holes and damaged fibers could adversely affect the strength and performance of the fabric. Third, there is a concentration of stress where the seams are located which jeopardizes performance properties and ultimately results in premature product failure. Fourth, cutting and sewing is done manually which introduces the potentail for human error. In addition, fabric waste is generated by the cut and sew process and seams in a garment create a bulkiness especially at the shoulders and underarms which can affect the comfort of a garment.
and other handoff calls. Even if there is no special voice but the channels in q1 and q2 are filled with handoff calls and any other handoff calls tries to make a call, it will be blocked. Retrial voice call will be blocked if the channel of q1 is filled with special, handoff and retrial calls. The retrial call can only preempt new calls. Meanwhile, for the retrial and new calls to have access to the channel, the handoff and special will need to access q2 before q1, they will only access q1 if only there is no free channel in q2. In this work, a retrial call is defined as any call that call back within the 30s from its previous attempt when it was blocked. We are trying to prevent a situation where a call trying to access a channel will be blocked for a longtime. Also, we are preventing a situation where a caller that has gone to sleep for more than 30s will suddenly call back to get access thereby preventing a new call that might be urgent. It is of the believed in this work that if a call is important, you will call back within some seconds. A new call will be blocked in q1 channel if there is no free channel. As soon as the call is blocked, its number will be registered in the cache in the network, then, if the call is repeated within 30s it will assume a new status of retrial call. All these assumptions and processes have been incoporated in the flowchart shown in Fig. 2.
An extensive work has been done in literature for providing appropriate handoff scheme in UMTS while catering QoS needs of the network at the same time. In 1987 Europe produced GSM 2G standard issued by ETSI and in 1993 first GSM mobile phone became available and fax, data and sms services were launched. Schiller (2008) explained the requirements of hand off process that are resource management and different traffic conditions during movement of the UE/cell phone from one cell to another during an ongoing session as interference experienced by the user's equipment from the near cell. Jayasuriya (2001) had described different types of handoffs and handoff algorithms. Hard handoff is also known as break before make because this type of handoff firstly breaks connection and after breaking makes a new connection with BS. GSM uses hard handoffs which break connections during handoff and not able to support high demanding multimedia services as Voice Over Internet Protocol (VOIP), heavy web browsing etc. These two issues led to number of researchers to explore their work area. J. N. et al (1994) explained evaluation of GSM that offers up to 472 kbps data rates, but unable to support for voice applications and lead to creation of UMTS. Main ai m of UMTS is to provide mobility without connection break and it also supports various multimedia services. Soft handoff is special feature of UMTS which is also known as make before break because this type of handoff firstly build connection and after building a new connection with base station (BS), break connection with old BS, supported by Wide Code Division Multiple Access (WCDMA) access method (Homla 2001). Kim and Sung (1999) explained another type of handoff called softer handoff, implemented in the UMTS system. Further research also been done by researchers on UMTS architecture to support soft and softer handoffs, network architecture consists of UE, BS’s, Radio Network Controller (RNC), Gateway GPRS Support Node (GGSN), Serving GPRS Support Node (SGSN) and Server. Wong (1997) explained problem of the situation where one base station receives two signals from one user from two adjacent sectors which BS serves during softer handoff in UMTS. To resolve this problem rake receivers were used in transrecievers of BS. Stojmenovic (2002) had given detail description of UMTS handoffs requirements, QoS requirements of different bearer services and their management in UMTS (Garg 2000). To provide required QoS to multimedia services, UMTS support five service classes traffic class, conversational class, streaming class, interactive and background class, which are divided based on QoS metrics which evaluate performance of the system during different handoffs (Sharma 2004).
3) Since the performance of the call dropped rate is calculated as possible call dropping in every stage from the radio link to the PSTN connection, the response time of the handoff in the network will be a factor when the cell becomes small, the response time for a handoff request has to be shorter in order to reduce the call dropped rate.
High speed Internet with mobility is required for doubling the demand of Integrated wireless networks. When the mobile node is changing its position from one location to other an uninterrupted connection is maintained by means of handoff  . Handoff is the process of assignment of a current call from one channel to the other channel of core network or it is the assignment of call between two base stations . Handoff between the similar networks with same technology, then it is called as horizontal handoff or homogeneous handoff. In order to make the continues connection with handoff requires the fulfilment of mobility and session management among the networks . An efficient distributive and mobility management  system can be helpful in different applications those are secured data base entry monitoring, focusing on QoS, parallel arrangement of data in mobile wireless applications, digital media files.
2302 Wireless networks accessing technologies are in vast growth. Owing to this organization of different networks technologies such as 3G (UMTS, IEEE 802.11), 4G (LTE, IEEE 802.16) and 5G, the users gets a great opportunity to be connected to those technologies at anytime and anywhere. The vital accessing of technologies tends to be so quick and easier because of introducing the smart mobile terminal multi accessing modes such as mobile phones, smart-phones, IPAD, etc. The above mentioned modes have enabled users also to handle simultaneously various applications by using different access networks. Although most technologies can be accessed by heterogeneous wireless networks, there exists most vigorous issue. The issue is owing to enabling the users to continuously choose the most appropriate access network during their communication. Similarly, there exist a handoff while a mobile node from one network accessing other mobile node in another network. Also there may arise the mismatch in accessing network which is denoted as Ping-Pong effect. In addition to that during resource allocation there exists shrinkage of network coverage more frequently which readily leads to inaccuracy.
time units handoff time), according to the input parameters, the overall effect of the non-handoff mode coding dwarfs the effect of the handoff mode coding. The data in all three graphs (mean time until successful transmission, probability of retransmission, and mean number of retransmissions per frame) is as we expect. A very “strong” puncturing matrix introduces many errors into the bit stream, reducing the effectiveness of the error correction coding. As the puncturing matrix “strength” is reduced (as the distance between punctured bits increases), the code tends to approach the performance of the use of no puncturing matrix.
With the development of integrated wireless mobile system, non-real-time service has to be incorporated and its effect needs to be taken into consideration . In order to support wider range of traffic, the handoff strategy need to take different features of different types of service into account. On the other hand, transmission delay of non-real- time service does not have much impact on the performance of non-real-time service (delay insensitive). Therefore, a successful handoff without interruption is very important to real time services, but not so critical for non-real-time service.  proposed a special two-dimensional model for cellular mobile systems with pre-emptive priority to real time service calls. However, no distinction was made between originating and handoff requests. Since forced termination of ongoing real time services calls is more annoying than blocking of originating calls from the users’ point of view, higher priority should be given to real time service handoff calls. In , a priority handoff scheme for the integrated voice/data wireless network has been studied but only data service handoff requests are allowed to be queued.  employed the concept of prioritization of handoff calls over new calls since it is desirable to complete an ongoing call rather than accepting a new one. They developed a channel assignment policy as well as using the idea of buffering handoff calls in case there are no available channels.  presented a comprehensive survey of different call admission control techniques.  proposed a support for multimedia users with dynamic bandwidth requirements. These policies take only local information in the admission decision process, and therefore will have a high call dropping probability. To reduce the call dropping probability, few other CAC algorithms that take into consideration neighbouring cells information have been proposed   . However, those algorithms only support users with fixed bandwidth requirements.
As a matter of fact, network conditions have an important influence on vertical handoff decisions. In Ref., the authors propose a number of VHO algorithms for two new network models considering integration of WLAN and 3G networks. In , a vertical handoff algorithm based on Q-learning is proposed. Q-learning can provide the decider with self-adaptive ability for handling the terminal handoff requests with different motion types and channel conditions. In Ref., a new adaptive vertical handoff algorithm based on compensating time is devised to analyze the necessity of access to WLAN. They could reduce the ping-pong effect. The previous researches, however, could be considered insufficiently the influences of fading effects on RSS. In this paper, a vertical handoff algorithm using Savitzky-Golay filtering will be proposed for different fading effects. The handoff between WLAN and LTE in wireless access technology is a typical representation. Meanwhile, the paper introduces the basic principles and the decision processes. The algorithm is able to reduce effectively the fading effect and the unnecessary handoff. It is also applicable to vertical handoff among other wireless access technologies.
Heterogeneous wireless networks need to cooperate to provide users to provide ubiquitous environment with seamless mobility. Mobile nodes (MNs) can automatically switch the connectivity between different types of networks. Next-generation wireless networks have been imagined as an Internet Protocol (IP) based infrastructure with the integration of various wireless access networks such as IEEE 802.11 wireless local area networks (WLANs), IEEE 802.16 wireless metropolitan area networks (WMANs), Wimax ,Wi-Fi networks. The interworking between different wireless access networks has been a hot research and development topic
Residency training programs have understood the importance of handoff communication for decades. However, the Accreditation Council on Graduate Medical Education heightened its attention to handoffs as duty hours were implemented and later revised. Currently, the Accreditation Council on Graduate Medical Education states: “Sponsoring institutions and programs must ensure and monitor effective, structured handover processes to facilitate both continuity of care and patient safety. Programs must ensure that residents are competent in communicating with team members in the handover process.” Some training programs have met this requirement by mandating lectures and learning modules for house staff. Other programs monitor the sign-out process and deem residents
The conventional handoff decisions are normally a single metric based i.e. RSSI, which alone is not suitable for current mobile system. In order to maintain a continuous and reliable link between the Mobile Station and the base station in a cellular network, new and better handoff algorithms are needed to keep QoS as high as possible. Handoff algorithms, based on soft computing techniques such as Fuzzy Logic, Neural Networks, genetic algorithms, probability theory etc can be used for the same purpose . These kinds of algorithms are based on uncertainty, partial truth, and approximation and depend on the expertise advice for information gathering to reduce computational cost. The purpose of this work is to utilize fuzzy logic to model and solve a real world problem of handoffs. It also emphasizes on design and implement a generalized framework for the design of Fuzzy Logic based handoff controller.
In wireless multimedia networks, the process of offering Quality of Service (QoS) guaranteed multimedia services becomes more challenging owing to the limited bandwidth, dynamic environment and mobility. This problem can be overcome by a call admission control mechanism that restricts the network access based on resource availability. In this paper QoS based Adaptive admission control algorithm for wireless multimedia networks is proposed. Initially the calls entering the network cell are categorized as real time handoff calls, non-real time handoff calls and new calls which are handled in the similar progression. In common, any call category entering the cell undergoes bandwidth test and when the bandwidth value is satisfied, the call is admitted. Otherwise cell performs different cell resizing technique for respective call categories. The proposed work is implemented in Network simulator (NS-2). It is shown that the proposed admission control algorithm achieves better bandwidth utilization, fairness with reduced call dropping rate, when compared with the existing technique. A mobile cellular architecture based on WCDMA is considered for implementation of this technique.
Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008, Article ID 136939, 14 pages doi 10 1155/2008/136939 Research Article Handoff Triggering and Networ[.]