A wireless communication system is provided for reducing the probability that latency before data transmission increases when a mobile station that is actually in sync is judged to be out of sync. A base station causes the timing calculation part to calculate the timing advance (TA) of a transmit timing from the mmobile station; causes the timer adaptive control part to obtain the traveling speed or the time variation in TA of the mmobile station and, adaptively determines and outputs as the timer update information the length of the mfirst timer within an M number in total of synchronization timers and the length of the second timer of the mmobile station and update the length of the mfirst timer; and transmits from the downlink transmission part a downlink signal which contains timer update information.
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Claim 1: . A base station of a wireless communication system which performs communication between a mobile station and the base station, the base station comprising:
Claim 2: . The base station of, wherein the base station notifies said set period via a message which is related to a RRC connection.
Claim 3: . A mobile station of a wireless communication system which performs communication between the mobile station and a base station, the mobile station comprising:
Claim 4: . The mobile station of, wherein the mobile station received the set period via a message which is related to a RRC connection.
Claim 5: . A method executed by at least one processor of controlling a base station of a wireless communication system which performs communication between a plurality of mobile stations and the base station, the method comprising:
Claim 6: . A method executed by at least one processor of controlling a mobile station of a wireless communication system which performs communication between the mobile station and a base station, the method comprising:
Claim 7: . A wireless communication system which performs communication between a mobile station and a base station, wherein the base station comprises:
Claim 8: 8. A method of a User Equipment (UE), the method comprising:
Claim 9: 9. The method according to, wherein the first timer value is included in system information.
Claim 10: 10. The method according to, wherein the first timer value is included in system information broadcast to the UEs.
Claim 11: 11. The method according to, wherein the second timer value is included in a message related to an RRC connection.
Claim 12: 12. The method according to, wherein the timer with the second timer value is used to determine whether an uplink can be synchronized or not.
Claim 13: 13. The method according to, wherein the timer with the second timer value is used to determine whether an uplink can be synchronized or not, and
Claim 14: 14. A User Equipment (UE) comprising:
Claim 15: 15. The UE according to, wherein the first timer value is included in system information.
Claim 16: 16. The UE according to, wherein the first timer value is included in system information broadcast to the UEs.
Claim 17: 17. The UE according to, wherein the second timer value is included in a message related to an RRC connection.
Claim 18: 18. The UE according to, wherein the timer with the second timer value is used to determine whether an uplink can be synchronized or not.
Claim 19: 19. The UE according to, wherein the timer with the second timer value is used to determine whether an uplink can be synchronized or not, and
Complete technical specification and implementation details from the patent document.
More than one reissue application has been filed for the reissue of U.S. Pat. No. 8,259,701, The reissue applications are (1) the present application, (2) Ser. No. 16/725,617, filed Dec. 23, 2019 (3) Ser. No. 15/974,310, issued as RE47,846, and (4) Ser. No. 14/444,321, issued as RE47,721, The present application is a continuation reissue of Ser. No. 16/725,617, filed Dec. 23, 2019.
This is a continuation reissue of U.S. application Ser. No. 16/725,617, which was filed Dec. 23, 2019, which is a continuation reissue of U.S. patent application Ser. No. 15/974,310, which was filed on May 8, 2018, issued as U.S. RE47846, which is a continuation reissue application of U.S. application Ser. No. 14/444,321, which was filed on Jul. 28, 2014, issued as U.S. RE47,721, which is a reissue application of U.S. Pat. No. 8,259,701 issued Sep. 4, 2012, which was filed as U.S. patent application Ser. No. 12/525,722 on Aug. 4, 2009, which is a National Stage of International Application No. PCT/JP2008/051685 filed Feb. 1, 2008, and which claims priority from Japanese Patent Application No. 2007-026203, filed Feb. 5, 2007 in the Japan Patent Office, the disclosures of which are incorporated herein by reference in their entirety.
The present invention relates to a wireless communication system which manages synchronization by use. of a timer, and more particularly, to a wireless communication system, its base station and mobile station, a communication synchronization management method and a timer control program therefore which enable the base station to adaptively control a transmit timing of an uplink signal from the mobile station.
In 3GPP Long Term Evolution (LTE), consideration is given to maintaining orthogonality between mobile stations (UE: user equipment) by allocating an orthogonal radio resource to each mobile station (UE) when transmitting and receiving data (a radio resource is an area uniquely defined by time and frequency; radio resources are set by dividing time and frequency into discrete areas for allocation to different mobile stations, so that one resource will not overlap between two mobile stations).
During transmission/reception of an uplink signal, in order to eliminate interference between mobile stations (UE) within the cell of a base station (Node B) so that the uplink signals can be demodulated correctly by the base station (Node B), it is essential that the base station's receive timing of an uplink signals from each of a plurality of mobile stations (UE) fall within a guard interval called a “cyclic prefix (CP).” At the same time, regardless of whether synchronization in data transmission/reception is actually being maintained, synchronization is assumed to be guaranteed if a receive timing falls within a predetermined timer period (i.e. during a timer is running). Based on this assumption, a state in which a receive timing falls within the timer period is judged to be a deemed in-sync state (i.e. a mobile station is assumed to be uplink synchronized), and a state in which a receive timing does not fall within the timer period (i.e. a timer expires) is judged to be a deemed out-of-sync state (i.e. a mobile station is assumed to be NOT uplink synchronized).
A mobile station (UE) which has been determined to be in a deemed out-of-sync state sends a Non-sync RACH (Non-synchronized Random Access Channel), in which a plurality of mobile stations (UE) compete for and use common radio resources, before transmitting an uplink signal. The mobile station then receives from the base station a timing advance (TA) for adjusting its transmit timing. According to the TA, the mobile station adjusts its transmit timing and finally synchronizes the uplink signal (i.e. the uplink signal is received within a CP at the base station).
Since each mobile station (UE) must secure synchronization while it is transmitting an uplink signal, a timing advance (TA) is notified from the base station to each mobile station, either at constant intervals or triggered by the occurrence of a specific event (e.g., a rapid change in the traveling speed of the mobile station). The reference time period from when the timing advance (TA) is last updated until the mobile station is judged to have returned to an out-of-sync state is either notified from the base station in the system information as the cell specific value or is pre-defined as a fixed value. The reference time is monitored at the base station and each of the mobile stations (UE) through use of a timer. Upon a timeout of the timer (i.e., when the reference time period described above expires), the mobile station (UE) is judged to have transited from a deemed in-sync state to a deemed out-of-sync state.
For the purpose of judging whether a mobile station (UE) is in a deemed in-sync state or a deemed out-of-sync state, the base station controls as many timers as the number of mobile stations (UE) under its management. The mth timer held by the base station (where m is an integer between 1 and M, and M is a natural number indicating the number of mobile stations (UE) managed by the base station) corresponds to the timer held by the mth mobile station (UE).
The plurality of timers controlled by the base station are set to the same length of time, so are the timers held by the plurality of mobile stations. The base station timers and the mobile station timers are set to a timer length such that synchronization can be guaranteed by the mobile station (UE) that is traveling at the highest speed (e.g., 350 km/h) of all the mobile stations (UE) supported by the base station. The timer length is therefore shorter than the minimum length of time over which this mobile station (UE) will become out-of-sync. A determination between a deemed in-sync state and a deemed out-of-sync state is made solely relying on the state of the timer, regardless of the actual traveling speed of the mobile station (UE). Non-patent Literature 1 discloses an example of a process for adjusting a transmit timing during transfer of an uplink signal in the 3GPP Long Term Evolution (LTE) described above.
When data is generated for transmission to the base station, a mobile station (UE) in a deemed in-sync state first transmits a Scheduling Request (SR) to the base station to request a radio resource over which to transmit the data, using a radio resource specific to the mobile station (UE). One method that can be used to assign a radio resource specific to a mobile station (UE) is to periodically assign a radio resource over which to transmit an SR to each of the mobile stations (UE) that are in a deemed in-sync state. On the other hand, when a mobile station (UE) in a deemed out-of-sync state transmits an SR, it first transmits a Non-sync RACH and receives a timing advance (TA) for controlling the transmit timing and, at the same time, assigns a radio resource specific to the mobile station (UE) over which to transmit the SR.
It is clear from the foregoing that a mobile station (UE) in a deemed out-of-sync state suffers a longer latency (or a delay due to waiting time) before it can initiate data transmission than a mobile station in a deemed in-sync state. This is because the former mobile station additionally requires a step of transmitting a Non-sync RACH before being able to perform a step of transmitting an SR. In addition, since orthogonality between mobile stations (UE) is not guaranteed for a Non-sync RACH, a collision may occur between mobile stations (UE). If a collision occurs, the transmitted Non-sync RACH may not be detected by the base station, in which case the mobile station (UE) must retransmit a Non-sync RACH. This further increases the latency.
Non-patent Literature 1 3GPP RAN WG2 Contribution [R2-063401.doc NTT DoCoMo]
http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_56/Document s/
Non-patent Literature 2 3GPP RAN WG1 Contribution [R1-063377.doc Nokia]
http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_47/Docs/
Non-patent Literature 3 3GPP RAN WG1 Contribution [R1-063405.doc Siemens]
http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1/Docs/
In the related art described above, the timer length is set based on the time in which synchronization is guaranteed by a rapidly traveling (for example, at a speed of 350 km/h) mobile station (UE). This leads to a problem in which a mobile station (UE) that is standing still or traveling at a low speed may be judged to be in a deemed out-of-sync state upon a timeout of the timer, even though the actual uplink synchronization is being maintained.
Furthermore, if another data occurs at the mobile station (UE) and an uplink signal must be transmitted during a period in which the timer has timed out but synchronization is actually being maintained, the latency before the data can be transmitted becomes even longer.
This is because a static or slow-moving mobile station (UE) is judged to be out-of-sync based on the timer, even though it is actually in sync and can transmit a Scheduling Request (SR) using a radio resource specifically assigned to it. In such situation, the mobile station needs first to transmit a Non-sync RACH to receive a timing advance (TA) from the base station (Node B), so that it can be assigned a radio resource over which to transmit the SR according to the timing advance (TA).
An object of the present invention is to provide a wireless communication system, its base station and mobile station, a communication synchronization management method and a timer control program therefor which can control the timer length used for judging whether a mobile station is in a deemed in-sync state or in a deemed out-of-sync state adaptively for each a mobile station, thereby minimizing possibilities for an actually in-sync mobile station to be judged to be in a deemed out-of-sync state.
Another object of the present invention is to provide a wireless communication system, its base station and mobile station, a communication synchronization management method and a timer control program therefor which can reduce a latency in transmission of an uplink signal during a period in which a mobile station in a deemed out-of-sync state is actually in sync.
According to a first exemplary aspect of the invention, a base station of a wireless communication system which performs wireless communication between a mobile station and a base station, comprises
a timer unit which sets a period, during which synchronization of a receive timing at the base station for an uplink signal from the mobile station is guaranteed, and, according to the occurrence or non-occurrence of a timeout of the period, judges whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
a timer control unit which is made capable of determining the period of the timer unit for each mobile station according to the state of the mobile station and updating the timer unit.
According to a second exemplary aspect of the invention, a mobile station of a wireless communication system which performs wireless communication between a mobile station and a base station, comprises
a timer unit which sets a period, during which synchronization of a receive timing at the base station for an uplink signal from the mobile station is guaranteed, and, according to the occurrence or non-occurrence of a timeout of the period, judges whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
a timer control unit which is made capable of determining the timer length according to the state of the mobile station and updating the timer unit.
According to a third exemplary aspect of the invention, a wireless communication system which performs wireless communication between a mobile station and a base station, comprises
the base station and the mobile station
comprising a timer unit which sets a period, during which synchronization of receive timings at the base station for uplink signals from the mobile station is guaranteed and, according to the occurrence or non-occurrence of a timeout of the period, judges whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
at least either of the base station and the mobile station
comprising a timer control unit which is made capable of determining the timer length of at least either of the base station and the mobile station adaptively for each mobile station according to the state of the mobile station and updating the timer unit.
According to a fourth exemplary aspect of the invention, a communication synchronization management method in wireless communication system to perform wireless communication between a mobile station and a base station, comprises
at the base station and the mobile station
having a timer step of setting a period, during which synchronization of a receive timing at the base station for an uplink signal from the mobile station is guaranteed, and, according to the occurrence or non-occurrence of a timeout of the period, judging by a timer whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
at least one of the base station and the mobile station
determining the period used in the timer step at least either of the base station and the mobile station adaptively for each mobile station according to the state of the mobile station and updating the timer.
According to a fifth exemplary aspect of the invention, a timer control program which is realized by a computer of a wireless communication system which performs wireless communication between a mobile station and a base station for operating on the base station,
causing the computer to execute
a function to set a period, during which synchronization of a receive timing at the base station for an uplink signal from the mobile station is guaranteed, and, according to the occurrence or non-occurrence of a timeout of the period, judge by a timer whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
a timer control function which is made capable of determining the timer length_for each mobile station according to the state of the mobile station and updating the timer.
According to a sixth exemplary aspect of the invention, a timer control program which is realized by a computer of a wireless communication system which performs wireless communication between a mobile station and a base station for operating on the mobile station,
causing the computer to execute
a function to set a period, during which synchronization of a receive timing at the base station for an uplink signal from the mobile station is guaranteed, and, according to the occurrence or non-occurrence of a timeout of the period, judge by a timer whether the mobile station is in a deemed in-sync state, in which uplink synchronization is guaranteed, or in a deemed out-of-sync state, in which uplink synchronization is not guaranteed, and
a timer control function which is made capable of determining the timer length according to the state of the mobile station and updating the timer.
Effect of the present invention is that the probability can be reduced that a latency before data transmission increases when a mobile station that is actually in sync is judged to be out of sync based on a timeout of the timer used for judging whether a mobile station is in a deemed in-sync state or in a deemed out-of-sync state. This is because the present invention can control the timer length of each mobile station adaptively to the traveling speed of the mobile station.
The present invention will now be described in detail with reference to the drawings.
First, in exemplary embodiments of the present invention, an initial value Tfor the timer, which is used for judging whether a mobile station is in a deemed in-sync state or in a deemed out-of-sync state, is set during a period in which synchronization of a rapidly moving station can be guaranteed. This can be done by using a method similar to commonly used methods. In 3GPP LTE, a traveling speed of 350 [km/h] is assumed as a reference speed for setting a timer length.
In Non-patent Literature 2, the tolerance for deviations in transmit timing required for an uplink signal to be detected correctly is estimated to be approximately 1 [usec]. In Non-patent Literature 3, the worst case for synchronization loss is assumed to be when synchronization is lost as a result of a deviation of 1 [usec] in transmit timing.
Unknown
March 31, 2026
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