Directional handover control in digital mobile radio systems employing MAHO

• US 5,327,575 A
• Filed: 03/23/1992
• Issued: 07/05/1994
• Est. Priority Date: 03/23/1992
• Status: Expired due to Term

• Current Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Bonta, Jeffrey D., Menich, Barry J.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Le, Thanh C.
• Application Number:
  US07/856,278
• Time in Patent Office: 834 Days
• Field of Search: 455/33.1, 455/34.1, 455/33.2, 455/56.1, 455/54.1, 455/62, 379/59, 379/60
• US Class Current: 455/437
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/32 by location or mobility data, e.g. speed data

Abstract

A method of selecting handover targets for a communication unit exchanging a communicated signal through a serving base site in a digital cellular system. The method uses timing advance to determine a relative distance of a communication unit to the serving base site. The method comprising the steps of comparing a timing advance value with a first threshold. The first threshold may be equal to a distance one and one-half times the radius of the serving cell. When the timing advance value exceeds the first threshold, a base site frequency list is modified to include base sites non-adjacent the serving base site. The identity of the non-adjacent base sites may be determined from the directionality of the communication unit. The method further includes the step of selecting a handover target providing a highest relative RSSI value to the communication unit from the modified base site frequency list.

Claims

1. A method of selecting handover targets for a communication unit exchanging a communicated signal through a serving base site in a digital cellular system, such method comprising the steps of:

A) determining a directionality of the communication unit based upon a first set of measured RSSI values of base sites within a base site frequency list;

B) comparing a timing advance value of the communication unit with a first threshold;

C) when the timing advance value exceeds the first threshold, modifying the base site frequency list to include base sites non-adjacent the serving base site based upon the directionality of the communication unit; and

D) selecting a handover target providing a highest relative RSSI value to the communication unit based upon a second set of measured RSSI values of base sites within the modified base site frequency list.

2. An apparatus for selecting handover targets for a communication unit exchanging a communicated signal through a serving base site in a digital cellular system, such apparatus comprising:

A) means for determining a directionality of the communication unit based upon a first set of measured RSSI values of base sites within a base site frequency list;

B) means for comparing a timing advance value of the communication unit with a first threshold;

C) means for modifying the base site frequency list to include base sites non-adjacent the serving base site when the timing advance value exceeds the first threshold based upon the directionality of the communication unit; and

D) means for selecting a handover target providing a highest relative RSSI value to the communication unit based upon a second set of measured RSSI values of base sites within the modified base site frequency list.

3. A method of selecting handover targets from a communication unit exchanging a communicated signal through a serving base site in a digital cellular system, such method comprising the steps of:

A) measuring RSSI values of base sites within a base site frequency list for sites adjacent the serving base site;

B) determining a directionality of the communication unit based upon the measured RSSI values;

C) comparing a timing advance value of the communication unit with a first threshold;

D) when the timing advance value exceeds the first threshold, modifying the base site frequency list to include base sites non-adjacent the serving base site based upon the directionality of the communication unit; and

E) measuring RSSI values of base sites of base site frequency list including base sites non-adjacent the serving base site; and

F) selecting a handover target providing a highest relative RSSI value to the communication unit from the modified base site frequency list.