Method and apparatus for performing idle handoff in a multiple access communication system

• US 6,178,164 B1
• Filed: 10/07/1998
• Issued: 01/23/2001
• Est. Priority Date: 06/07/1996
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tiedemann, Edward G. Jr., Wang, Jun
• Primary Examiner(s): Jung, Min
• Application Number:
  US09/168,191
• Time in Patent Office: 839 Days
• Field of Search: 370/328, 370/329, 370/331, 370/332, 370/333, 370/335, 455/436, 455/437, 455/438, 455/439, 455/442
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration

Abstract

In a mobile communication system having a first communication device for communicating with a plurality of second communication devices, a method for performing handoff within the mobile communication system includes transmitting from at least one of the second communication devices to the first communication device a handoff list of second communication devices to which the first communication device is permitted to handoff. A channel assignment message is transmitted from each of the second communications devices in the handoff list. The handoff list includes base stations controlled by a single controller that determines which of the second communication devices transmits the channel assignment message. The base stations on the handoff list have pilot signals and the energy levels of the pilot signals are measured by the first communication device. The measured energy levels are transmitted to the controller and compared by the controller to provide an energy level list of base stations according to the comparing. The energy level list is transmitted to the first communication device and the handoff is performed according to the energy level list.

Claims

1. A method for performing handoff within a mobile communication system, the mobile communication system having at least one first communication device for communicating with a plurality of second communication devices (SCD), comprising the steps of:

(a) transmitting from at least one of the SCDs to the first communication device a handoff list to which the first communication device is permitted to handoff when in a system access state, wherein the handoff list comprises SCDs controlled by a single controller not located in the at least one first communication device; and

(b) transmitting a channel assignment message to the at least one first communication device from each of the SCDs in the handoff list.

2. The method in accordance with claim 1, wherein the single controller determines the SCDs used to transmit a channel assignment message.

3. The method in accordance with claim 1, wherein the SCDs on the handoff list transmit pilot signals, the method further comprising the steps of:

(c) measuring the energy levels of the pilot signals at the first communication device;

(d) transmitting the measured energy levels to the single controller;

(e) comparing the transmitted energy levels; and

(f) providing an energy level list of SCDs according to the comparison.

4. The method in accordance with claim 3, further comprising the step of transmitting the energy level list to the first communication device.

5. The method in accordance with claim 4, further comprising the step of performing a handoff according to the energy level list.

6. The method in accordance with claim 5, comprising the step of performing handoff only with SCDs contained in both the handoff list and the energy level list.

7. The method in accordance with claim 3, further comprising the step of transmitting to the first communication device a neighbor list of SCDs that are located in the geographic vicinity of the first communication device, wherein the handoff is preceded by the step of transmitting from the first communication device an origination message to at least one SCD.

8. The method in accordance with claim 7, wherein the handoff list and the neighbor list are transmitted together.

9. The method in accordance with claim 7, wherein the neighbor list comprises SCDs controlled by a plurality of controllers.

10. The method in accordance with claim 7, wherein the SCDs on the handoff list comprise a subset of the SCDs on the neighbor list.

11. The method in accordance with claim 1, wherein step (b) is followed by the step of performing a handoff of the first communication device from one of the SCDs to another one of the SCDs when the first communication device is in an idle mode (access state).

12. The method in accordance with claim 1, wherein step (a) is preceded by the step of synchronizing by the first communication device with at least one of the SCDs.

13. An apparatus for performing handoff within a mobile communication system, comprising:

a first communication device (FCD);

a plurality of second communication devices (SCDs) for communicating with the FCD, wherein at least one of the SCDs transmits to the FCD a handoff list of other SCDs to which the FCD is permitted to handoff when in a system access state, and wherein at least one SCD in the handoff list transmits to the FCD a channel assignment message for communicating with each SCD included in the handoff list; and

at least one controller used to control all SCDs included in the handoff list.

14. The apparatus in accordance with claim 13, further comprising at least one controller used to control all SCDs included in the handoff list, wherein each SCD in the handoff list separately transmits to the FCD a channel assignment message for communicating with that respective SCD.

15. The apparatus in accordance with claim 14, wherein a controller determines the SCD or SCDs used to transmit the channel assignment message.

16. The apparatus in accordance with claim 13, further comprising:

at least one controller used to control at least one of the SCDs included in the handoff list;

a device communicatively coupled to the FCD, the device used for measuring the energy level of pilot signals received by the FCD from any SCDs, and wherein the measured energy levels are communicated to the at least one controller;

and wherein the at least one controller compares the energy levels and cooperates in communicating a ranked energy level list for the SCDs to the FCD.

17. The apparatus in accordance with claim 16, wherein a handoff is performed according to the energy level list.

18. The apparatus in accordance with claim 17, wherein a handoff is performed only with base SCDs included in the handoff list.

19. An apparatus, comprising:

at least one first communication device (FCD), the FCD comprising;

a processing device;

a message generator device coupled to the processing device;

a modulator device coupled to the message generator;

a transmitter coupled to the modulator device;

a receiver device;

a plurality of demodulator devices communicatively coupled to the processing device and the receiver device, the demodulator device demodulating signals received from the receiver device;

a searcher device coupled to the processing device and the receiver device;

a combiner coupled to the demodulator device, the combiner used to produce a signal from the signals received from the demodulator device;

a duplexing device coupled to the transmitter device and the receiving device; and

at least one antenna coupled to the duplexing device; and

a plurality of second communication devices (SCDs) for communicating with the FCD, wherein at least one of the SCDs transmits to the FCD a handoff list of other SCDs to which the FCD is permitted to handoff when in a system access state, and wherein at least one SCD in the handoff list transmits to the FCD a channel assignment message for communicating with each SCD included in the handoff list.

20. An apparatus, comprising:

at least one first communication device (FCD), the FCD comprising;

a processing means for processing data;

a message generator means for generating messages, the message generator means coupled to the processing means;

a modulator means for modulating a signal, the modulator means coupled to the message means;

a transmitter means for transmitting a signal, the transmitter means coupled to the modulator means;

a receiver means for receiving a signal;

a demodulator means for demodulating a signal, the demodulator means communicatively coupled to the processing means and the receiver means, the demodulator means demodulating signals received from the receiver means;

a searcher means for searching for a desired signals, the searcher means coupled to the processing means, the demodulator means, and the receiver means;

a combiner means for combining desired signals, the combiner means coupled to the demodulator means, the combiner means used to produce a signal from the signals received from the demodulator means;

a duplexing means for allowing signals to be received and transmitted at the same time, the duplexing means coupled to the transmitter means and the receiving means; and

at least one antenna means for receiving a signal and coupled to the duplexing means; and

a plurality of second communication devices (SCDs) for communicating with the FCD, wherein at least one of the SCDs transmits to the FCD a handoff list of other SCDs to which the FCD is permitted to handoff when in a system access state, and wherein at least one SCD in the handoff list transmits to the FCD a channel assignment message for communicating with each SCD included in the handoff list.