Method in a portable communications and data terminal operating to optimize receipt of both incoming CDPD and AMPS messages

• US 6,449,494 B1
• Filed: 06/29/1998
• Issued: 09/10/2002
• Est. Priority Date: 06/28/1995
• Status: Expired due to Term

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Cashman, Russell P.
• Primary Examiner(s): CUMMING, WILLIAM D
• Application Number:
  US09/107,025
• Time in Patent Office: 1,534 Days
• Field of Search: 455/553, 455/426
• US Class Current: 455/553.1
• CPC Class Codes: H04W 36/0094 Definition of hand-off measurement parameters
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: H04W 68/00 User notification, e.g. alerting and paging, for incoming communication, change of service or the like
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A portable radio telephone handset operates as a data transfer terminal as well as an analog cellular telephone subscriber station. Two modes of operation, an analog cellular communication mode and a Cellular Digital Packet Data (CDPD) mode, are available in the handset. The handset distinguishes between paging signals indicating CDPD mode communications and those indicating analog cellular communications. The handset also automatically preempts CDPD communications in favor of analog cellular communications such as those carried out in an AMPS configuration. The handset maintains an active status on a CDPD communication channel during a “sleep mode”, when the handset can carry out AMPS activity.

Claims

1. A method of carrying out handoff of a wireless subscriber station from a first cell to a second cell in a Cellular Digital Packet Data (CDPD) system controlled by a mobile data intermediate system (MD-IS), where said wireless subscriber station contains a first cell transfer database pertaining to radio frequency characteristics of said first cell, said method comprising steps of:

(a) sending a polling receiver ready (RR) signal from said wireless subscriber station to a CDPD Mobile Data Base Station (MDBS) in said second cell;

(b) determining a first time interval for a complete Received Signal Strength Indication (RSSI) scan of said second cell by said wireless subscriber station;

(c) dividing said first time interval into a plurality of overlapping time slots;

(d) alternately scanning said CDPD channel and an Advanced Mobile Phone Service (AMPS) control channel during successive time slots for a first duration of said first time interval, thereby creating a second cell transfer data base pertaining to said second cell; and

(e) deleting said first cell transfer database upon acquisition of said second cell transfer database.

2. The method of claim 1, wherein step (d) comprises of sub-steps of:

(i) repeating said alternating scan of said CDPD and AMPS control channels for a second duration of said first time interval where said scan on said CDPD channel is carried in time slots not scanned for CDPD activity in a previous duration of said first time interval; and

(ii) repeating sub-step (i) until all said time slots of said first time interval had been scanned for CDPD activity.

3. The method of claim 2, wherein each said time slot has the same time duration.

4. The method of claim 3, wherein each said time slot has a duration defined as 2n, where n is the minimum time between AMPS pages.

5. The method of claim 4, wherein a maximum time between AMPS pages is less than a quantity 2n-g where g is a time required for moving from one communication mode to another.

6. The method of claim 5, wherein all said time slots at said first time interval are scanned within three durations of said first time interval.

7. The method of claim 6, wherein said first time interval is divided into a plurality of time slots so that the RSSI scan interval is an even multiple of 2n.

8. The method of claim 7, wherein g is approximately 300 ms and the AMPS paging interval is from 4.5 seconds to 8.7 seconds.

9. The method of claim 2, further comprising the steps of:

(f) selecting a second time interval greater than said first time interval; and

(g) sending a polling RR from said subscriber station to said MD-IS once during each of said second time intervals.

10. The method of claim 2, wherein said second time interval has a duration in the range of 5 minutes to 1 hour.