Handover method for OFDM wireless communication system

• US 7,729,313 B2
• Filed: 06/20/2005
• Issued: 06/01/2010
• Est. Priority Date: 06/18/2004
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd., Yonsei University
• Original Assignee: Samsung Electronics Co. Ltd., Yonsei University
• Inventors: Cho, Sung-Hyun, Lee, Sang-Hoon, Yun, Sang-Boh
• Primary Examiner(s): Patel; Ajit
• Application Number:
  US11/156,507
• Publication Number:
  US 20060007888A1
• Time in Patent Office: 1,807 Days
• Field of Search: None
• US Class Current: 370/331
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 16/12 Fixed resource partitioning
• CPC Class Codes: H04W 36/00692 using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] allocation of physical resources in CoMP or in CA H04L5/0035
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 48/20 Selecting an access point

Abstract

An OFDM mobile communication system includes a system controller for dividing an OFDM symbol into a control channel and a data channel, multiplexing the control channel to control subchannels, and allocating the multiplexed control subchannels to base stations. The base stations simultaneously transmit control signals on the control allocated subchannels and data on the data channel. Mobile nodes receive an OFDM symbols with the multiplexed control channels for them and a data channel for selecting a base station according to information in the control subchannels. The mobile node simultaneously processes control subchannels received from two base stations using one physical layer module.

Claims

1. A handover method of a mobile node in a wireless communication system including a plurality of base stations, the method comprising:

receiving signals of an entire system frequency band including a dedicated control band and a dedicated data band, the dedicated control band being divided into a plurality of unique control channels, each of the plurality of unique control channels being allocated to each of the plurality of base stations and the dedicated data hand being occupied by all of the plurality of base stations; and

selecting a handover-target base station from among the plurality of base stations, based on at least two pilot signals transmitted on at least two of the plurality of unique control channels,

wherein a number of the unique control channels is determined based on a frequency reuse factor, and

wherein time periods of symbol durations and guard interval durations of the unique control channels are set to multiples of time periods of a symbol duration and a guard interval duration of a data channel included in the dedicated data band.

2. The method of claim 1, wherein selecting the handover-target base station comprises:

measuring an intensity of each of the at least two pilot signals; and

selecting a base station transmitting a pilot signal with a highest intensity among the at least two pilot signals as the handover-target base station.

3. The method of claim 2, wherein selecting the handover-target base station comprises:

comparing the intensity of each of the at least two pilot signals with a predetermined threshold;

registering base stations transmitting a pilot signal with an intensity greater than the predetermined threshold as handover candidate base stations;

determining if an intensity of a pilot signal from a currently connected base station is within a predetermined range of the predetermined threshold;

selecting one of the handover candidate base stations as the handover-target base station, when the intensity of the pilot signal from the currently connected base station is within the predetermined range of the predetermined threshold; and

transmitting a handover initialization request to the currently connected base station and the handover-target base station.

4. The method of claim 1, wherein the plurality of unique control channels are multiplexed using at least one of a Frequency Division Multiplexing (FDM) scheme and a Code Division Multiplexing (CDM) scheme.

20. The method of claim 1, wherein the dedicated control band is used for transmitting at least one of a Synch Channel (SCH), a Broadcast Channel (BCH), a Common Pilot Channel (CPICH) and a Semi-Soft-Handover Control Channel (SSHCCH), and the dedicated data band is used for transmitting data.

5. A handover method of a base station in a wireless communication system including a mobile node and a plurality of base stations, the method comprising:

transmitting, to the mobile node, a control signal using a unique control channel allocated to the base station; and

transmitting, to the mobile node, data of the base station using a data channel included in a dedicated data band occupied by all of the plurality of base stations,

wherein the unique control channel is one of a plurality of unique control channels included in a dedicated control band and is used for transmitting a pilot signal to select a handover-target base station to the mobile node,

wherein a number of the unique control channels is determined based on a frequency reuse factor, and

wherein time periods of symbol durations and guard interval durations of the unique control channels are set to multiples of time periods of a symbol duration and a guard interval duration of the data channel.

6. The method of claim 5, wherein the plurality of unique control channels are multiplexed using at least one of a Frequency Division Multiplexing (FDM) scheme and a Code Division Multiplexing (CDM) scheme.

7. The method of claim 5, further comprising:

receiving duplicate data transmitted from a currently connected base station of the mobile node; and

transmitting the duplicate data to the mobile node, after being selected as the handover-target base station and receiving a handover decision message from the mobile node.

21. The method of claim 5, wherein the control signal includes at least one of a Synch Channel (SCH), a Broadcast Channel (BCH), a Common Pilot Channel (CPICH) and a Semi-Soft-Handover Control Channel (SSHCCH).

24. The method of claim 5, wherein the unique control channel is used to transmit a pilot signal from the base station to the mobile node.

8. A handover system in a wireless communication system, comprising:

a plurality of base stations; and

a mobile node for receiving signals of an entire system frequency band including a dedicated control band and a dedicated data band, the dedicated control band being divided into a plurality of unique control channels, each of the plurality of unique control channels being allocated to each of the plurality of base stations and the dedicated data band being occupied by all of the plurality of base stations, and for selecting a handover-target base station from among the plurality of base stations, based on at least two pilot signals transmitted on at least two of the plurality of unique control channels,

wherein a number of the unique control channels is determined based on a frequency reuse factor, and

wherein time periods of symbol durations and guard interval durations of the unique control channels are set to multiples of time periods of a symbol duration and a guard interval duration of a data channel included in the dedicated data band.

9. The system of claim 8, wherein the mobile node measures an intensity of each of the at least two pilot signals and selects a base station transmitting a pilot signal with a highest intensity among the at least two pilot signals as the handover-target base station.

10. The system of claim 8, wherein the mobile node compares an intensity of each of the at least two pilot signals with a predetermined threshold, registers base stations transmitting a pilot signal with an intensity greater than the predetermined threshold as handover candidate base stations, determines if an intensity of a pilot signal from a currently connected base station is within a predetermined range of the predetermined threshold, selects one of the handover candidate base stations as the handover-target base station, when the intensity of the pilot signal from the currently connected base station is within the predetermined range of the predetermined threshold, and transmits a handover initialization request to the currently connected base station and the handover-target base station.

11. The system of claim 8, wherein the dedicated control band comprises a multiplexed band using at least one of a Frequency Division Multiplexing (FDM) scheme and a Code Division Multiplexing (CDM) scheme.

12. The system of claim 8, wherein the mobile node comprises:

a synchronization module for performing timing synchronization on the received signals of the entire system frequency band;

a demodulation module for demodulating the signals synchronized by the synchronization module;

a detection module for detecting respective unique control channels for respective base stations from the signals demodulated by the demodulation module;

a selection module for selecting the handover-target base station according to pilot signals of the unique control channels detected by the detection module; and

a decoding module for restoring data received from the handover-target base station selected by the selection module using a data channel.

13. The system of claim 12, wherein the demodulation module comprises a fast Fourier transformer.

14. The system of claim 12, wherein the demodulation module simultaneously demodulates the signals synchronized by the synchronization module.

22. The system of claim 8, wherein the dedicated control band is used for transmitting at least one of a Synch Channel (SCH), a Broadcast Channel (BCH), a Common Pilot Channel (CPICH) and a Semi-Soft-Handover Control Channel (SSHCCH), and the dedicated data band is used for transmitting data.

15. A handover system in a wireless communication system, comprising:

a mobile node; and

a base station transmitting, to the mobile node, a control signal using a unique control channel allocated to the base station, and transmitting, to the mobile node, data of the base station using a data channel included in a dedicated data band occupied by all base stations of the wireless communication system,

wherein the unique control channel is one of a plurality of unique control channels included in a dedicated control band and the mobile node uses a pilot signal transmitted from the unique control signal to select a handover-target base station,

wherein a number of the unique control channels is determined based on a frequency reuse factor, and

wherein time periods of symbol durations and guard interval durations of the unique control channels are set to multiples of time periods of a symbol duration and a guard interval duration of the data channel.

16. The system of claim 15, wherein the plurality of unique control channel are multiplexed using at least one of a Frequency Division Multiplexing (FDM) scheme and a Code Division Multiplexing (CDM) scheme.

17. The system of claim 15, wherein the unique control channel is used to transmit a pilot signal.

18. The system of claim 15, wherein the base station receives duplicate data transmitted from a currently connected base station of the mobile node and transmits the duplicate data to the mobile node, when selected as the handover-target base station, after receiving a handover decision message from the mobile node.

19. The system of claim 15, further comprising a system controller for allocating a dedicated control band to each of the base stations and allocating the dedicated data band including the data channel occupied by all of the base stations.

23. The system of claim 15, wherein the control signal comprises at least one of

a Synch Channel (SCH);

a Broadcast Channel (BCH);

a Common Pilot Channel (CPICH); and

a Semi-Soft-Handover Control Channel (SSHCCH).