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CONCENTRIC CELL HANDOVER AND ASSIGNMENT ALGORITHMS

IP.com Disclosure Number: IPCOM000007872D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-May-01
Document File: 2 page(s) / 122K

Publishing Venue

Motorola

Related People

G. Eastwick: AUTHOR [+2]

Abstract

With the rapid growth of cellular systems, such as time division multiplexed communication systems, it is becoming increasingly difficult to provide suffi- cient capacity in busy city centers using conventional frequency reuse techniques. Bearing in mind the lim- ited (and fixed) spectrum available to each commu- nication system operator, novel frequency planning techniques must be employed by system operators if these operators are to provide sufficient capacity to support high volumes of traffic (per square kilometer) in densely populated (city) environments. One such technique is the use of a concentric cell system in which different frequency re-use patterns may be employed between a macro (upper) level and a concentric (lower) level. However, in order to use the concept of concentric cells effectively, new handover and assignment algorithms need to be developed.

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M-LA Technical Developments

CONCENTRIC CELL HANDOVER AND ASSIGNMENT ALGORITHMS

by G. Eastwick and J. Hopkinson

INTRODUCTION

  With the rapid growth of cellular systems, such as time division multiplexed communication systems, it is becoming increasingly difficult to provide suffi- cient capacity in busy city centers using conventional frequency reuse techniques. Bearing in mind the lim- ited (and fixed) spectrum available to each commu- nication system operator, novel frequency planning techniques must be employed by system operators if these operators are to provide sufficient capacity to support high volumes of traffic (per square kilometer) in densely populated (city) environments. One such technique is the use of a concentric cell system in which different frequency re-use patterns may be employed between a macro (upper) level and a concentric (lower) level. However, in order to use the concept of concentric cells effectively, new handover and assignment algorithms need to be developed.

This paper describes an improved handover and assignment algorithm.

mobile units closely located to a base station, while outer cell carriers are used for the more distantly located mobile units. It is therefore necessary to ensure that a mobile unit is not handed to an inner cell carrier when that mobile unit is in a pool of coverage away from the base station, otherwise the mobile unit could sulIer co-channel interference. This problem is illustrated in Figure 1 below. PROPOSED ALGORlTHM

  The concept behind the proposed algorithm is to estimate co-channel interference likely to be expe- rienced by a mobile unit (at its current position) on an inner cell carrier in response to signal level meas- urements for outer cell channels that are known to possess co-channel inner cell carriers (frequencies). This technique is possible since the inner and outer cell carriers share the same antenna, and thus the signal level on the inner cell carriers can be directly determined from measurements of the outer cell car- riers. One possible algorithm is given below:-

* Check if the radio signal level horn the serving cell exceeds the GSM parameter (RXLEV- ACCESS-MIN + X), where: RXLEV- ACCESS- MIN is the minimum allowable received signal level at a mobile unit required for access to the communication system through a base station (as specified in GSM rec. 5.08) and X is an additional signal level margin defined by a system operator and is specified such as to require a mobile unit to have a stronger radio signal level that the minimum level specified in GSM rec. 5.08); and

CONCENTRIC CELLS

  A concentric cell will have frequenci...