Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
  • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
  • H04W16/10—Dynamic resource partitioning
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
  • H04B1/7097—Interference-related aspects
  • H04B1/7103—Interference-related aspects the interference being multiple access interference
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/50—Allocation or scheduling criteria for wireless resources
  • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
  • H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W24/00—Supervisory, monitoring or testing arrangements
  • H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation
  • H04W72/044—Wireless resource allocation based on the type of the allocated resource
  • H04W72/0446—Resources in time domain, e.g. slots or frames
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
  • H04W72/21—Control channels or signalling for resource management in the uplink direction of a wireless link, i.e. towards the network

Definitions

• the present invention relates generally to a communication method and apparatus in mobile communication systems, and more particularly, to a dynamic channel allocation (DCA) method and apparatus for use in TDD CDMA communication system.
• DCA dynamic channel allocation
• CDMA is a more advanced mobile communication system, with higher capacity and spectrum efficiency.
• FDD Frequency Division Duplex
• TDD Time Division Duplex Code Division Duplex
• TDD CDMA communication system TD-SCDMA
• ITU International Telecommunication Union
• TD-SCDMA TDD CDMA communication system
• ITU International TDD CDMA communication system
• the Chinese government provides great support for TD-SCDMA, and allocated 155MHz spectrum for TD-SDCMA.
• TDD CDMA communication system is recognized as very promising in the future.
• each RNS Radio Network System
• the base station is responsible for communicating with UEs via wireless medium
• a main function of RNC is to allocate communication radio resource for the base station and UEs and manage the resource.
• the base station and RNC in RNS are generally called as base station together.
• power control is generally applied in uplink, thus, signals sent from all UEs allocated in the same uplink timeslot will reach the receiver of the base station with approximately equal power. Accordingly, the situation that strong signal suppresses weak signal in the base station almost does not exist, that means the far-near effect won't happen in uplink.
• synchronization control is applied for uplink, so signals sent from all UEs allocated in the same uplink timeslot will reach the receiver of the base station almost simultaneously, which reduces the multi-access in uplink to the greatest extent.
• a mobile terminal in a downlink timeslot will receive signals sent by the base station to it, and signals sent by the base station to other
• each UE allocated in the downlink timeslot is different, so, the base station has to transmit signals to UEs with different distance at different transmission power, the farther the distance, the higher the transmission power, so as to ensure that signals received by each UE can satisfy a predefined QoS requirement.
• a close UE receives signals sent by the base station to a remote UE in the same downlink timeslot
• signals sent to the remote UE at higher transmission power will produce interference to signals sent to the close UE at lower transmission power and thus this affects signal reception of the close UE, which is the far-near effect often occurring in downlink. How to settle the far-near effect will have a significant influence upon the downlink communication performance of TDD CDMA communication system.
• a detailed description will be given below to clarify the far-near effect in downlink, in conjunction with Fig.1.
• this cell includes a base station, UEO and UE1 , wherein UEO is close to the base station while UE1 is far away from the base station. Assume UEO and UE1 are allocated in the same downlink timeslot, the base station transmits signal SO to UEO and signal S1 to UE1 in the downlink timeslot.
• the base station should transmit signal S1 at a higher transmission power P1 and transmit signal SO at a lower transmission power P0, so that signal SO received by UEO and signal S1 received by UE1 can both satisfy the QoS requirement.
• the attenuation of the signal in a fading channel is proportional to the nth order of the transmission distance, and n generally is a value more than 3.
• the transmission power P1 at which the base station transmits signal S1 should be 8 times more than the transmission power PO at which the base station transmits signal SO. That is, when the base station is transmitting SO and S1 in the same downlink timeslot respectively at PO and P1 , UEO can receive SO sent by the base station to it, and S1 sent by the base station to UE1 as well, and the power of SO reaching UEO is only 1/8 of that of S1 reaching UEO.
• An object of the present invention is to provide a dynamic channel allocation (DCA) method and apparatus for use in TDD CDMA communication system, capable of reducing or canceling communication interferences brought by the far-near effect in the downlink of TDD CDMA communication system, and thus improving the downlink communication performance of TDD CDMA communication system.
• DCA dynamic channel allocation
• a DCA method for use in TDD CDMA communication system is proposed in the present invention, to be performed by a UE, comprising: in a downlink timeslot, receiving the signals transmitted by a network system to each UE allocated in the downlink timeslot; estimating the strength of each interfering signal introduced by the signals transmitted to other UEs to the signal transmitted to the UE in the received signals; transmitting the information about each interfering UE whose interfering signal strength exceeds a predefined value, to the network system via an uplink.
• a DCA method for use in TDD CDMA communication system is proposed in the present invention, to be performed by a network system, comprising: receiving from a UE the information about each interfering UE producing interfering signal to the UE; allocating network resource to the interfered UE according to the information about the interfering UE; reporting the allocated network resource to the interfered UE so that the interfered UE can receive signals transmitted from the network system by utilizing the allocated network resource.
• Fig.1 is a schematic diagram illustrating the downlink far-near effect in conventional TDD CDMA communication system
• Fig.2 is a schematic diagram illustrating the method for canceling downlink far- near effect in TDD CDMA communication system in accordance with the present invention
• Fig.3 is a flow chart illustrating the DCA method for use in TDD CDMA communication system in accordance with the present invention
• Fig.4 displays the structure of the DCA apparatus in TDD CDMA communication system in the embodiment of the present invention
• the main idea of the present invention is to allocate each UE in different downlink timeslot, to avoid the interference caused by the far-near effect when
• UEs in the same downlink timeslot and with different distance to the base station are receiving signals transmitted by the base station with beams in the same direction.
• the interfered UE reports the information about each interfering UE to the base station through uplink signaling.
• the base station reallocates network resource for the interfered UE and each interfering UE, according to the report from the interfered UE, which comprises: reallocating downlink timeslots, especially for those UEs close to the base station, with the principle that we should try to allocate the UEs close to the base station and those far away from the base station in different downlink timeslots; reallocating transmitting beam to avoid the situation that each UE receives signals transmitted by the base station to different
• Fig.2 illustrates the method for canceling downlink far-near effect in accordance with the present invention.
• the base station allocates UEO, UE1 , UE2 and UE3 in the same downlink timeslot and the four UEs receive signals transmitted by the base station in the same beam direction.
• SO, S1, S2 and S3 will be transmitted by the base station respectively to
• the base station should allocate timeslots for UEO, UE1 , UE2 and UE3 according to the following principle, to cancel interference caused by the far-near effect:
• UEO accesses TDD CDMA communication system and camps on a cell after powering on (step S10).
• UEO attempts to communicate with another UE through the base station, it acquires the initially allocated radio resource by the base station as normal, including: information about uplink and downlink timeslots allocation, midamble, spreading code, beam direction in which the base station transmits signals to UEO, and etc (step S20).
• UEO When UEO is receiving signals from the base station in downlink timeslot, it will receive signal SO sent by the base station to it, and signals S2 sent by the base station to UE2, because UEO and UE2 are allocated in the same downlink timeslot. Due to the far-near effect, S2 becomes the interfering signal for UEO and UE2 becomes the interfering UE for UEO.
• UEO estimates the strength of interfering signal S2 (step S30), and determines whether S2's strength exceeds a predefined value according to the estimation result (step S40). If S2's strength exceeds a predefined value, e.g.
• the interfered UEO detects the midamble in interfering signal S2 (step S50), and reports the midamble in interfering signal S2 to the base station through uplink signaling (step S60).
• the base station After receiving the midamble in the interfering signal S2 reported by UEO, the base station finds the ID corresponding to the interfering UE2 according to the midamble, and reallocates radio resource for the interfered UEO and/or the interfering UE2 (step S70). For instance, the base station can choose to reallocate a downlink timeslot for UEO so that UE1 and UE2 can receive signals from the base station in different downlink timeslot. The base station can also choose to measure the relative position of UEO and UE2, and use beams in different directions to transmit SO and S2 to UEO and UE2, so that SO and S2 can be in different beams when being transmitted by the base station.
• UEO and UE2 can respectively receive signals in different transmission angles from the base station, which avoids the result that UEO will be interfered by S2.
• the base station notifies UEO about the reallocated network resource, such as the reallocated downlink timeslot information, so that UEO can receive signals from the base station in the newly allocated timeslot (step S80).
• UEO After acquiring the network resource reallocated by the base station, UEO receives signals from the base station, by taking advantage of the reallocated network resource (step S90). For instance, UEO can receive signals from the base station in the newly allocated downlink timeslot, or receive radio signals transmitted by the base station in a new beam direction, or receive radio signals transmitted by the base station in a new beam direction in the newly allocated downlink timeslot.
• Fig.4 displays the structure of the DCA apparatus in TDD CDMA communication system in accordance with the embodiment of the present invention, wherein the components same as conventional network system and UEs are not given herein.
• UE 200 comprises: a receiving unit 204, in a downlink timeslot, for receiving signals transmitted by a network system to each UE allocated in the downlink timeslot; an estimating unit 205, for estimating the strength of each interfering signal introduced by the signals transmitted to other
• a detecting unit 201 for detecting the midamble in the interfering signal if the interfering signal strength exceeds a predefined value
• a transmitting unit 202 for transmitting the midamble to the network system via the uplink.
• the 102 allocates network resource for the interfered UE according to the information about the interfered UE, and sends the allocated network resource to the interfered UE, so that the interfered UE can use the allocated network resource to receive signals sent by the network system.
• the network resource can be the downlink timeslot allocated for the interfered UE by the network system, so that the interfered UE and the interfering UE can receive signals from the network system in different downlink timeslots.
• the network system can adopt other means to decrease interferences to the interfered UE, for example, determine the position information of the interfered UE and each interfering UE according to the above received information about each interfering UE through determining unit
• the interfered UE reports information about the interfering UE (such as the midamble in the interfering signal) to the base station, so that the base station can reallocates radio resource for the interfered UE after obtaining the information about the interfering UE.
• the interfered UE can receive signals from the base station in the newly allocated downlink timeslot, which cancels the interference caused by the far-near effect.

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• 2003
  • 2003-11-28 CN CNA2003101157952A patent/CN1622500A/zh active Pending
• 2004
  • 2004-11-19 EP EP04799190A patent/EP1692898A1/en not_active Withdrawn
  • 2004-11-19 CN CNA2004800350033A patent/CN1887016A/zh active Pending
  • 2004-11-19 JP JP2006540742A patent/JP2007512754A/ja not_active Withdrawn
  • 2004-11-19 WO PCT/IB2004/052482 patent/WO2005053342A1/en not_active Application Discontinuation

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