Method and apparatus for allocating channels in an orthogonal frequency division multiple access system

• US 7,636,571 B2
• Filed: 03/04/2005
• Issued: 12/22/2009
• Est. Priority Date: 03/05/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Yoon, Soon-Young, Maeng, Seung-Joo, Lee, Jae-Hyok, Jang, Ji-Ho, Jeon, Jae-Ho, Oh, Jeong-Tae
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Brandt; Christopher M
• Application Number:
  US11/072,181
• Publication Number:
  US 20050197132A1
• Time in Patent Office: 1,754 Days
• Field of Search: 455/450, 455/436, 455/446, 455/447, 455/442, 455/438
• US Class Current: 455/437
• CPC Class Codes: H04L 5/0062 Avoidance of ingress interference, e.g. ham radio channels
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/26 Resource reservation
• CPC Class Codes: H04W 36/0072 of resource information of target access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

A method for allocating a frequency to a subscriber station (SS) in handover operation in an Orthogonal Frequency Division Multiple Access (OFDMA) system. In the method, the SS checks safety channel frequencies for a target base station (BS), generates a safety channel frequency request message for requesting allocation of the checked safety channel frequencies, and transmits the safety channel frequency request message. Upon receiving the safety channel frequency request message from the SS, a serving BS allocates frequencies for a requested channel, and transmits an allocation message with the frequency allocation information to the SS. The serving BS transmits a channel allocation request message to the target BS according to the frequency allocation information. Upon receiving the channel allocation request message, the target BS allocates the safety channel frequencies to the SS.

Claims

1. A method of allocating frequency for handover of a Subscriber Station (SS) for use of a frequency reuse factor of 1 or a frequency reuse factor approximating 1 in a communication system, the method comprising:

receiving, by the SS, a frame in a first coverage of a serving Base Station (BS);

detecting, by the SS, frequencies in the frame, when the SS is located in the first coverage and a second coverage of a target BS, and reporting to the serving BS the detected frequencies; and

receiving a signal representing that the detected frequencies are determined safety channel frequencies used between the target BS and the SS;

wherein the SS uses the detected frequencies together with the target BS, the target BS receives the safety channel frequencies, the target BS determines that the SS communicates data with the target BS using the safety channel frequencies until the handover ends, and the target BS varies the safety channel frequencies every predetermined number of frames,

wherein the frame includes a preamble including a first preamble and a second preamble, the first preamble is used for transmitting, by the SS, information to measure a distance from the serving BS and a state of a channel between the SS and the serving BS, and the second preamble is used for transmitting, by the SS, data in frequencies except for the detected frequencies, in which data is not transmitted among frequencies included in the second preamble of the frame.

2. The method of claim 1, wherein the detected frequencies are frequencies in which data is not transmitted among frequencies included in the second preamble of the frame, the frequencies in which data is not transmitted are determined according to a pattern, and the pattern is set differently for every BS, and is changed every frame.

3. A method of allocating frequency for handover of a Subscriber Station (SS) for use of a frequency reuse factor of 1 or a frequency reuse factor approximating 1 in a communication system, the method comprising:

allocating, by a serving Base Station (BS), frequencies not used in neighbor BSs as safety channel frequencies in a next frame, the safety channel frequencies being used by the serving BS and the SS; and

communicating with the serving BS, by the SS, the safety channel frequencies until the handover ends,

wherein when the SS completely moves to a coverage of the target BS, the SS releases a call with the serving BS and communicates with only the target BS using other frequencies instead of the safety channel frequencies, and

wherein when the SS completely moves back to a coverage of the serving BS while performing the handover, the SS reports, to the serving BS, that a handover situation has ended, and the serving BS allocates to the SS other frequencies instead of the safety channel frequencies, and

wherein when the SS ends the call while performing the handover, the serving BS releases allocation of the safety channel frequencies, reports the end of the handover to the target BS and changes the safety channel frequencies every frame, and

wherein the frame includes a preamble including a first preamble and a second preamble, the first preamble is used for transmitting, by the SS, information to measure a distance from the serving BS and a state of a channel between the SS and the serving BS, and the second preamble is used for transmitting, by the SS, data in frequencies except for the detected frequencies, in which data is not transmitted among frequencies included in the second preamble of the frame.

4. The method of claim 3, wherein the detected frequencies are frequencies in which data is not transmitted among frequencies included in the second preamble of a frame, the frame is received by the SS in a coverage of the serving BS, and the frequencies in which data is not transmitted are determined according to a pattern that is set differently for every BS, and is changed every frame.