Identification code search in a communication device

• US 5,408,682 A
• Filed: 08/10/1992
• Issued: 04/18/1995
• Est. Priority Date: 06/08/1989
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Hoflinger, Jurgen, Ranner, Georg
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US07/927,779
• Time in Patent Office: 981 Days
• Field of Search: 455/62, 455/67.1, 455/226.1, 455/77, 455/161.1, 455/161.2, 455/166.1, 455/166.2, 455/343, 455/32.1, 455/34.1, 455/34.2, 379/58, 379/59, 379/62
• US Class Current: 455/166.2
• CPC Class Codes: H04M 1/72511 Searching for available channels

Abstract

With cordless telephones it is a known fact that each pair of radio stations has m radio channels out of n possible radio channels in common. During a test cycle the mobile unit examines only the common radio channels. Consequently, the test period required for testing only the common channels is shorter than the time necessary for testing all channels. If, by chance, all common channels are busy or if such a situation is the result of a malfunctioning, establishing a link between the base unit and the mobile unit is no longer possible. In the proposed embodiment of a cordless telephone, reliably establishing a link is guaranteed in that in a first test phase the common channels and in a second test phase all n radio channels are tested. A field of application of the invention is the cordless telephone.

Claims

1. Method for establishing a communication link comprising,

(a) in a first communication device, the step of sending out an identification code over one of n radio channels, where n is an integer, for an initial period (t_E);

(b) in a second communication device the steps of searching for the identification code, said searching including repeatedly applying a test cycle, and exiting the test cycle if the identification code is found, the test cycle including the steps of;

i) first searching a group of m priority channels where m is an integer and m<

n;

ii) first standing by for a first stand-by time;

iii) second searching all n channels; and

iv) second standing by for a second stand-by time,

whereby the test cycle is shorter than the initial period; and

(c) upon finding the identification code, setting up the second communication device to operate using a channel on which the identification code was found.

2. The method of claim 1 wherein the second communication device is a mobile unit of a cordless telephone, and wherein the first standby time is longer than the second stand-by time in the test cycle to increase a time during which the mobile unit can be operated separately from a base station without recharging.

3. A method for establishing a communication link between a pair of communication devices comprising the steps of:

(a) from a first unit, sending out an identification code over one of n radio channels, wherein n is an integer; and

(b) in a second unit searching for the identification code according to a test cycle, the test cycle including executing a first test phase and second test phase, the first test phase including searching m radio channels, where m is an integer less than n, and the second test phase including

i) putting the second unit in a standby mode for a first time interval;

ii) searching all n radio channels if the identification code is not found in the first test phase; and

iii) if the identification code is not found in the second test phase, the second test phase also including putting the second unit in the standby mode for a second time interval, the first and second time intervals being chosen so that the total test cycle is shorter than a transmission time for the identification code.

4. The method of claim 3 wherein the m channels form a contiguous block with the n channels.

5. The method of claim 3 wherein the n are channels divided into a plurality of blocks of m channels, where m is an integer less than n and each block is assigned a group number and, during manufacturing, a group number is assigned to the first unit and a second unit;

and the first test phase includes searching m radio channels chosen according to the group number of the first and second unit.

6. The method of claim 3 in which the test cycle includes alternately executing the first phase and the second phase.