Handoff in a wireless communication system

Details Handoff in a wireless communication system Handoff in a wireless communication system

1999-08-11

2003-07-01

Olms, Douglas (Department: 2732)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S332000

Reexamination Certificate

active

06587446

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to wireless communication system, and, more particularly, to methods and apparatus for providing hard handoffs between cells in such systems.
BACKGROUND OF THE INVENTION
In a code division multiple access (CDMA) system, the vast majority of handoffs happen between cells on the same CDMA channel and use soft handoff procedures. On some occasions, the mobile stations need to perform a handoff between cells on different CDMA channels where such channels are at different radio frequencies (FR), often denoted as inter-frequency hard handoff. Such situations are typically, but not limited to, either a handoff between different operators, a handoff between different RF channels allocated for capacity reasons, or a handoff between different signal modulation technologies.
Before effecting an inter-frequency hard handoff, the mobile station is directed by the base station to tune to the new target frequency, measure the radio environment (e.g., pilot signal strength of the received signals, etc.), and report the measurement back to the base station. Such a procedure is specified in TIA/EIA-95-B and greatly enhances the probability of success of an interfrequency handoff.
An essential requirement of the measurement on the target frequency, often referred to as “search excursion,” is to minimize the disruption of the current service on the originating frequency. Handoffs to a second frequency without adequate prior sampling could result in poor signal performance. On the other hand, sampling for long periods of time may cause the signal at the first frequency to be lost completely. The method described below permits the mobile station to minimize the search time and to limit the disruption of service.
SUMMARY OF THE INVENTION
A mobile station transmits a plurality of channels including a pilot channel and at least one information channel. In the exemplary embodiment, the base station determines the adequacy of the transmission energy of the reverse link signal in accordance with the received energy of the reverse link pilot signal. In the present invention, the pilot channel transmission power is retained at the level it was prior to the frequency search excursion, while increasing the transmission energy of at least one other channel transmitted by the mobile station. In addition, when the mobile station is not capable of increasing the transmission energy of all of the information channels, the mobile station generates a ranking of the importance of the different information channels and selectively increases the transmission power of those channels.


REFERENCES:
patent: 5751725 (1998-05-01), Chen
patent: 5963870 (1999-10-01), Chheda et al.
patent: 6073025 (2000-06-01), Chheda et al.
patent: 6078570 (2000-06-01), Czaja et al.
patent: 6134440 (2000-10-01), Black
patent: 6154659 (2000-11-01), Jalali et al.
patent: 6181943 (2001-01-01), Kuo et al.
patent: 6185431 (2001-02-01), Li et al.
patent: 6188900 (2001-02-01), Ruiz et al.
patent: 6252861 (2001-06-01), Bernstein et al.
patent: 6304755 (2001-10-01), Tiedemann, Jr. et al.
patent: 0667726 (1995-08-01), None
patent: 0809365 (1997-11-01), None
patent: 2314734 (1998-01-01), None
patent: 9729611 (1997-08-01), None
patent: 9740592 (1997-10-01), None
Maria Gustafsson, et al., Compressed Mode Techniques for Inter-Frequency Measurements in a Wide-Band DS-CSMA System, Ericcson Radio Systems, Stockholm, Sweden, IEEE 1997, p. 231-235.
Satarasinghe, et al., “A Novel Method for CDMA Hard Handoff” IEEE pp. 1766-1768 (1996).

Affiliated with

Also associated with

Rating

Handoff in a wireless communication system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Handoff in a wireless communication system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Handoff in a wireless communication system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3004766