Browse Prior Art Database

SUBSCRIBER-INITIATED INTRA-CELL HANDOVER

IP.com Disclosure Number: IPCOM000008257D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-May-30
Document File: 2 page(s) / 116K

Publishing Venue

Motorola

Related People

Mark J. Marsan: AUTHOR

Abstract

In current digital multi-site systems, an intra-cell handover is performed only when inbound link quality (as measured by a base site) degrades below a desired level and outbound link quality (as measured by a subscriber) remains at or above a desired level. Such intra-cell handovers may involve a change in the time slot on the same frequency, a change in frequency, or a change in time slot and frequency. However, there is currently no approach for performing an intra-cell handover when outbound link quality degrades below a desired level even though inbound link quality is at or above a desired level, particularly when neigh- boring site outbound link quality is also below a desired level (i.e., when an inter-cell handover does not provide any outbound quality improvement).

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m -LA Technical Developments

SUBSCRIBER-INITIATED INTRA-CELL HANDOVER

by Mark J. Marsan

INTRODUCTION

  In current digital multi-site systems, an intra-cell handover is performed only when inbound link quality (as measured by a base site) degrades below a desired level and outbound link quality (as measured by a subscriber) remains at or above a desired level. Such intra-cell handovers may involve a change in the time slot on the same frequency, a change in frequency, or a change in time slot and frequency. However, there is currently no approach for performing an intra-cell handover when outbound link quality degrades below a desired level even though inbound link quality is at or above a desired level, particularly when neigh- boring site outbound link quality is also below a desired level (i.e., when an inter-cell handover does not provide any outbound quality improvement).

  Outbound link quality may vary substantially among the base stations at any given base site due to varying levels of adjacent channel interference or intermodulation distortion from neighboring systems, or inconsistent reuse of frequencies in the same system which causes varying levels of

co-channel interference at the subscriber unit.

INCONSISTENT FREQUENCY REUSE

  Consider the case shown in Figure 1, where two Base Radios (BR) are operating from a single site. Typically, the desired signal level received at the subscriber is identical for both BRs, as both BRs have identical transmit power, antennas, cable loss, etc. However, co-channel interference powers may vary considerably, particularly if the frequency of the first BR is reused at a different site than the frequency of the second BR. As shown in Figure 1, if the site reusing the same frequency as the first BR is much farther away from the subscriber as the site reusing the same frequency as the second BR, the co-channel interference for the first BR may he much smaller than the second BR. If the subscriber is assigned to the second BR at the site and the carrier to interference ratio drops below the handover threshold, an intra-cell handover to the first BR will be beneficial as the carrier to interference ratio for the first BR may be considerable larger than the second BR.

0 Momola, 1°C. ,997 2.5 September 1997

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0 M -LA

Technical Developments

Cochannel Interferers for BRI, BR2

2 BR' s in serving celI

(CL), >> m,

Fig. 1 Example of Inconsistent Frequency Reuse

IN...