Wireless communication method, wireless communication system, base station and mobile station

• US 8,340,237 B2
• Filed: 03/26/2009
• Issued: 12/25/2012
• Est. Priority Date: 03/26/2008
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Sahara, Toru
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): Badipour, Bahman
• Application Number:
  US12/934,583
• Publication Number:
  US 20110026633A1
• Time in Patent Office: 1,370 Days
• Field of Search: 375/260, 375/295, 375/320, 375/324, 375/340, 375/355, 370/208, 370/280, 370/328, 370/505, 455/502
• US Class Current: 375/355
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04W 56/003 Arrangements to increase tolerance to errors in transmission or reception timing

Abstract

There is provided a wireless communication method, a wireless communication system, a base station and a mobile station which conduct wireless communication using an OFDM modulation scheme. The base station transmits a timing correction burst to the mobile station only when a correlation peak detected from a received OFDM symbol is within a predetermined timing detection range. If the timing correction burst is not introduced from the base station even after expiration of predetermined time duration, by copying a signal by a length different from a guard interval from the end of an effective symbol and adding the copied signal to the front of the effective symbol, the mobile station generates a new timing correction channel (second time), in which transmission timing of a previously generated timing correction channel is shifted.

Claims

1. A wireless communication method of conducting wireless communication between a mobile station and a base station by using an OFDM modulation scheme, the method comprising:

notifying a notification channel from the base station to the mobile station;

in the mobile station,

generating a channel to be frame synchronized with the notification channel and transmitting an OFDM symbol to the base station;

in the base station, as peak detection processes thereof,

removing a guard interval from the transmitted OFDM symbol to obtain an effective symbol;

detecting a correlation peak between the effective symbol and a known ideal symbol; and

only when the correlation peak is detected in a predetermined timing detection range shorter than a length of the effective symbol, transmitting a differential between reference timing of the base station and the time of the detection of the correlation peak to the mobile station by means of a timing correction burst;

in the mobile station,

if the timing correction burst is not introduced from the base station even after expiration of predetermined time duration from the transmission of the OFDM symbol to the base station,

copying a signal by a length different from a guard interval from the end of an effective symbol and adding the copied signal to the front of the effective symbol to shift transmission timing of a previously generated channel by a predetermined shift amount so as to generate a new channel having the shifted transmission timing; and

transmitting an OFDM symbol to the base station to implement the peak detection processes of the base station again, and

if the timing correction burst is introduced from the base station within the predetermined time,

correcting transmission timing by calculating a sum of shift amounts of transmission timing to the present time in order to solve a differential from reference timing of the base station; and

transmitting a communication channel assignment request to the base station at the corrected transmission timing.

2. The wireless communication method according to claim 1,

wherein in the process of generating a new channel in the mobile station, any one of two types of channels, which are alternatively generated due to differentials by the predetermined shift amount in transmission timing, is generated.

3. The wireless communication method according to claim 1,

wherein in the process of generating a new channel in the mobile station, a channel, in which transmission timing is advanced or delayed by the predetermined shift amount, is generated by making a length of signal to be copied shorter or longer than a guard interval.

4. The wireless communication method according to claim 1,

wherein the sum of the shift amounts is shorter than the length of the effective symbol.

5. The wireless communication method according to claim 1,

wherein if a communication channel is not assigned from the base station despite that the mobile station transmits a communication channel assignment request to the base station, the mobile station transmits the OFDM symbol to the base station as the same timing as the previously generated channel to implement peak detection processes of the base station again.

6. A wireless communication system comprising a mobile station and a base station, which conduct wireless communication by using an OFDM modulation scheme,

wherein the base station comprises:

a notification unit that notifies the mobile station of a notification channel;

a guard interval removing unit that removes a guard interval from an OFDM symbol transmitted from the mobile station through a channel generated by the personal channel to obtain an effective symbol;

a timing detection unit that detects a correlation peak between the effective symbol and a known ideal symbol; and

a correlation peak determination unit that transmits a differential between reference timing of the base station and the time of the detection of the correlation peak to the mobile station by means of a timing correction burst only when the correlation peak is detected within a predetermined timing detection range shorter than a length of the effective symbol, and

wherein the mobile station comprises;

a timing correction channel generating unit, which generates a channel to be frame synchronized with the notification channel and transmits an OFDM symbol to the base station, and which, if the timing correction burst is not introduced from the base station even after expiration of predetermined time duration from the transmission, copies a signal by a length different from a guard interval from the end of an effective symbol and adds the copied signal to the front of the effective symbol to shift transmission timing of a previously generated channel by a predetermined shift amount so as to generate a new channel having the shifted transmission timing and transmit an OFDM symbol to the base station;

a shift storing unit that stores a sum of shift amounts of transmission timing in the timing correction channel generating unit;

a transmission timing correcting unit which, if the timing correction burst is introduced from the base station within the predetermined time, corrects transmission timing by calculating a sum of shift amounts of transmission timing stored in the shift storing unit in order to solve a differential from reference timing of the base station; and

a communication channel assignment request unit that transmits a communication channel assignment request to the base station at the corrected transmission timing.

7. A base station that conducts wireless communication with a mobile station by using an OFDM modulation scheme,

wherein the mobile station comprises:

a timing correction channel generating unit, which generates a channel to be frame synchronized with a notification channel notified from the base station and transmits an OFDM symbol to the base station, and which, if a timing correction burst is not introduced from the base station even after expiration of predetermined time duration from the transmission, copies a signal by a length different from a guard interval from the end of an effective symbol and adds the copied signal to the front of the effective symbol to shift transmission timing of a previously generated channel by a predetermined shift amount so as to generate a new channel having the shifted transmission timing and transmit an OFDM symbol to the base station;

a shift storing unit that stores a sum of shift amounts of transmission timing in the timing correction channel generating unit;

a transmission timing correcting unit which, if the timing correction burst is introduced from the base station within the predetermined time, corrects transmission timing by calculating a sum of shift amounts of transmission timing stored in the shift storing unit to solve a differential from reference timing of the base station; and

a communication channel assignment request unit that transmits a communication channel assignment request to the base station at the corrected transmission timing, and

wherein the base station comprises;

a notification unit that notifies the mobile station of a notification channel;

a guard interval removing unit that removes a guard interval from an OFDM symbol transmitted from the mobile station through a channel generated by the personal channel to obtain an effective symbol;

a timing detection unit that detects a correlation peak between the effective symbol and a known ideal symbol; and

a correlation peak determination unit that transmits a differential between reference timing of the base station and the time of the detection of the correlation peak to the mobile station by means of a timing correction burst only when the correlation peak is detected within a predetermined timing detection range shorter than a length of the effective symbol.

8. A mobile station that conducts wireless communication with a base station by using an OFDM modulation scheme, the mobile station comprising:

a timing correction channel generating unit, which generates a channel to be frame synchronized with a notification channel notified from the base station and transmits an OFDM symbol to the base station, and which, if a timing correction burst is not introduced from the base station even after expiration of predetermined time duration from the transmission, copies a signal by a length different from a guard interval from the end of an effective symbol and adds the copied signal to the front of the effective symbol to shift transmission timing of a previously generated channel by a predetermined shift amount so as to generate a new channel having the shifted transmission timing and transmit an OFDM symbol to the base station;

a shift storing unit that stores a sum of shift amounts of transmission timing in the timing correction channel generating unit;

a transmission timing correcting unit which, if the timing correction burst is introduced from the base station within the predetermined time, corrects transmission timing by calculating a sum of shift amounts of transmission timing stored in the shift storing unit in order to solve a differential from reference timing of the base station; and

a communication channel assignment request unit that transmits a communication channel assignment request to the base station at the corrected transmission timing.