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A new multi objective handover algorithm for mobile infrastructure communication system

IP.com Disclosure Number: IPCOM000124210D
Published in the IP.com Journal: Volume 5 Issue 5 (2005-05-20)
Included in the Prior Art Database: 2005-May-20
Document File: 5 page(s) / 216K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

In mobile communication the area of service is divided in a multiple cell structure. Whenever a mobile terminal moves to a different cell a handover of the connection to the new access point is initiated. Handover increase overall interference. On the other hand, enlarging the network cells reduces the quality of service (noise etc.). In result, the handover conditions must be defined carefully to get the best out of the network infrastructure. Novel handover decision algorithms should consider more than one handover decision objective and a methodology to combine and process these criteria. In VCL technology the mobile terminals move in clusters. This fact is used to address to the above mentioned problem. So, the likelihood of a cluster having an access point moving together with the cluster is very high. Hence, in the new algorithm, the relative speeds and directions of components as handover decision metrics is considered. With the lowest membership value threshold, the algorithm is likely to achieve the minimum number of handovers; with the highest membership value threshold the algorithm is likely to achieve the minimum call blocking rate. The algorithm introduced provides an optimization mechanism with the trade off between handover attempts and call dropping rates as a consequence it also improves the soft capacity of the system and the grade of service.

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A new multi objective handover algorithm for mobile infrastructure communication system

Idea: Doc. Massimo Feroldi, IT-Cinisello

In mobile communication the area of service is divided in a multiple cell structure. Whenever a mobile terminal moves to a different cell a handover of the connection to the new access point is initiated. Handover increase overall interference. On the other hand, enlarging the network cells reduces the quality of service (noise etc.). In result, the handover conditions must be defined carefully to get the best out of the network infrastructure.

Novel handover decision algorithms should consider more than one handover decision objective and a methodology to combine and process these criteria. In VCL technology the mobile terminals move in clusters. This fact is used to address to the above mentioned problem. So, the likelihood of a cluster having an access point moving together with the cluster is very high. Hence, in the new algorithm, the relative speeds and directions of components as handover decision metrics is considered. With the lowest membership value threshold, the algorithm is likely to achieve the minimum number of handovers; with the highest membership value threshold the algorithm is likely to achieve the minimum call blocking rate. The algorithm introduced provides an optimization mechanism with the trade off between handover attempts and call dropping rates as a consequence it also improves the soft capacity of the system and the grade of service. 3G communication systems use Code Division Multiple Access (CDMA) as their air interface. CDMA systems are mainly interference limited. Increasing the interference reduces directly the system capacity. So in the new handover decision algorithm, one also considers the soft capacities of the access points that are affected by the interference in the environment.

One uses a fuzzy logic system with center average defuzzifier, product-inference rule, and singleton fuzzifier to combine and process the handover decision metrics. Details of the fuzzy logic systems can be found in.

Figure 1 shows the block diagram of the new system.

One defines a four-dimensional pattern vector for the current access point:

PVC =[Sc; Xc; ∆θc; ∆Vc] (1)

where, Sc is the received signal strength from the currently serving access point, Xc is the ratio of the used soft capacity to the total soft capacity for the currently serving access point, ∆θC is the direction difference between the mobile terminals and the currently serving access point, and ∆VC is the velocity difference between the mobile terminals and the currently serving access point.

One defines a four-dimensional pattern vector for the candidate access point n:

PVN=[Sn; Xn; ∆θn; ∆Vn] (2)

Here Sn is the received signal strength from the candidate access point, Xn is the ratio of the used soft capacity to the total soft capacity for the candidate access point, ∆θn is the direction difference betw...