Browse Prior Art Database

Minimizing macro-mobility handover frequency with a location based handoff trigger

IP.com Disclosure Number: IPCOM000016593D
Original Publication Date: 2003-Jul-01
Included in the Prior Art Database: 2003-Jul-01
Document File: 4 page(s) / 141K

Publishing Venue

Motorola

Related People

Uday Sagi: AUTHOR [+2]

Abstract

WLAN networks in enterprises provide employees an inexpensive alternative for telephony services and other real-time applications. Employees equipped with a dual mode mobile device can experience voice communications over the WLAN network in the enterprise, and over a cellular WAN network outside the enterprise. When the mobile moves between these heterogeneous networks (WLAN and 3G), a seamless handoff of an ongoing call is desired where the user does not perceive any delay or loss of voice data during the handoff.

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Minimizing macro-mobility handover frequency with a location based handoff trigger [MP1] 

By Uday Sagi, Murli Gummakonda

Motorola, Inc.

ABSTRACT

WLAN networks in enterprises provide employees an inexpensive alternative for telephony services and other real-time applications. Employees equipped with a dual mode mobile device can experience voice communications over the WLAN network in the enterprise, and over a cellular WAN network outside the enterprise. When the mobile moves between these heterogeneous networks (WLAN and 3G), a seamless handoff of an ongoing call is desired where the user does not perceive any delay or loss of voice data during the handoff.

Typically handoff triggers are based on the quality and strength of the radio signal between the mobile and the base site. Though this mechanism is sufficient enough to achieve seamless macro-mobility between WLAN and WAN networks, it often results in frequent and unnecessary handoffs. In this paper, an efficient and reliable macro-mobility handoff mechanism is presented where position and location information is used to accurately determine when a handoff is required.

PROBLEM

Seamless mobility between WLAN and WAN networks is usually achieved by triggering handoff procedures when the signal quality (or signal strength) at either the mobile or the base site reaches a “Handoff Threshold”. The handoff procedures involve communications between the mobile, the WLAN base site, and the WAN cellular site to seamlessly handoff an ongoing voice or multimedia communication.

In an enterprise environment, it is expected that a dual mode mobile station moves back and forth between WLAN and WAN coverage areas resulting in frequent, and in some cases, unnecessary handoffs. These “ping-pong” handoffs between the WAN and WLAN networks increase the cellular costs and strain the network resources as they result in unnecessary switches to and from cellular network for a brief period of time (typically a few seconds). This situation could particularly occur in enterprises or buildings with large exit points like those found in warehouses, distribution centers, airport luggage and freight handling. These kinds of businesses have a highly mobile workforce that usually works in and around the periphery of a building.

It is therefore desirable to continue existing coverage (either WLAN or cellular, but preferably WLAN due to low usage cost) as long as possible and initiate a handoff between WLAN and WAN only when absolutely required. This can be done by decreasing the “Handoff Threshold”, but runs the risk of completely losing the WLAN signal before handing off to the WAN. This reduced “Handoff Threshold” can cause a break in voice (or video), or could even result in a dropped call.

SOLUTION

In this paper, we propose a position and location based handoff trigger that greatly reduces the frequency of handoffs between WLAN and WAN networks. The proposed mechanism avoids “ping-pong” effects near t...