Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0667—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
  • H04B7/0671—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different delays between antennas
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
  • H04B7/0842—Weighted combining
  • H04B7/0862—Weighted combining receiver computing weights based on information from the transmitter

Definitions

• the present invention pertains to wireless telecommunications, and particularly to determining whether to enhance diversity in an Orthogonal Frequency- Division Multiplexing (OFDM) system.
• OFDM Orthogonal Frequency- Division Multiplexing
• Frequency division multiplexing is a technology that transmits multiple signals simultaneously over a single transmission path. Each signal travels within its own unique frequency range (carrier), which is modulated by the data (text, voice, video, etc.).
• Orthogonal FDM's (OFDM) spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the "orthogonality" in this technique which prevents the demodulators from seeing frequencies other than their own.
• OFDM Orthogonal FDM's
• the benefits of OFDM are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. This is useful because in a typical terrestrial broadcasting scenario there are multipath- channels (i.e., the transmitted signal arrives at the receiver using various paths of different length). Since multiple versions of the signal interfere with each other (inter symbol interference (ISI)) it becomes very hard to extract the original information.
• ISI inter symbol interference
• Diversity techniques are used for reducing the errors in the transfer of a single data stream. Diversity gives an increase in the robustness of the signal path. This means there will be an increase in the maximum data rate at any given distance.
• Multi-carrier based radio access schemes such as Orthogonal Frequency-
• OFDM Orthogonal Frequency Division Multiplexing
• DFT Discrete Fourier Transform
• Cyclic Delay Diversity is a technique which introduces spatial diversity to an Orthogonal Frequency Division Multiplexing (OFDM) based transmission scheme that itself may have no built-in diversity.
• OFDM Orthogonal Frequency Division Multiplexing
• CDD-based precoding can be defined by combining linearly increasing phase-shift diagonal matrix and unitary precoding matrix as shown by Expression ( 1 ).
• the CDD-based precoding matrix for the number of transmit antennas N, with spatial multiplexing rate can be defined by combining a phase-shift diagonal matrix and a precoding matrix.
• the signals transmitted from different antennas are copies of one time- domain OFDM symbol, each copy with different amount of cyclical shifts.
• OFDM system by doing so, an artificial multipath environment is generated to provide or enlarge the frequency selectivity.
• the system performance depends on the cyclic delay value.
• G. Bauch, J. S. Malik "Parameter optimization, interleaving and multiple access in OFDM with cyclic delay diversity.”
• proc. VTC 2004. pp. 505-509. 200 a methodology to determinate cyclic delay value is presented without the consideration of sub-carrier allocation.
• the (fractional) frequency reuse is a well known technology. See. for instance. US Patent 6,088,416, incorporated herein by reference. Frequency reuse has the ability to use the same frequencies repeatedly across a cellular system, since each cell is designed to use radio frequencies only within its boundaries, the same frequencies can be reused in other cells not far away with little potential for interference. The reuse of frequencies is what enables a cellular system to handle a huge number of calls with a limited number of channels. On the other hand.
• the Inter- cell Interference Coordination (ICIC) technology has the task to manage radio resources (notably the radio resource blocks) such that inter-cell interference is kept under control.
• a resource block is a number (M) of consecutive sub-carriers for a number (N) of consecutive OFDM symbols.
• introducing CDD in precoding can introduce a linear phase shift to the frequency channels, which can help to obtain frequency scheduling gain in the flat channel scenario.
• Fig. 1 shows Mean user throughput PFTF for per stream rate control (PARC) and selective per stream rate control (S- PARC) with and without CDD precoding in single cell with flat channel.
• PARC per stream rate control
• S- PARC selective per stream rate control
• Fig. 1 shows that, in the single-cell with flat channel scenario, the CDD can improve system performances for the frequency-domain scheduler, e.g., PFTF (proportional fair in both time and frequency domain), since the CDD can get more frequency channel variation, and due to the fact that there is only white noise, the fading variation of the frequency channel has an effect of the SINR variation in the frequency domain.
• Fig. 1 shows mean user throughput PFTF for per stream rate control (PARC) and selective per stream rate control (S-PARC) with and without CDD precoding in single cell with flat channel.
• PARC per stream rate control
• S-PARC selective per stream rate control
• Fig. 2 illustrates mean user throughput PFTF for PARC and S-PARC w ith and without CDD precoding in a multi cell with suburban SCM channel. Fig. 2 thus shows that CDD does not provide any interesting gains in a multi-cell scenario with frequency reuse equal to one. See, e.g.. 3GPP TR 25.814.
• the determination whether to implement cyclical delay diversity is made in accordance with interference distribution at the wireless terminal, as such interference distribution is measured or otherwise perceived.
• plural transmit antennas of a radio base station are employed to implement the cyclical delay diversity for the connection.
• An example embodiment includes receiving one or more indications of the interference distribution and using the indication(s) of the interference distribution to make the determination.
• the indication of interference distribution can take the form of information received from the wireless terminal, such as a measured signal to interference noise ratio (SINR) from the wireless terminal.
• SINR measured signal to interference noise ratio
• the determination to implement the cyclical delay diversity can be made affirmatively if the indication of the interference distribution indicates that noise is a greater factor than interference for a signal to interference noise ratio (SINR) for the wireless terminal.
• the indication of interference distribution can take the form of frequency reuse plan information for interfering cells.
• the determination to implement the cyclical delay diversity can be made affirmatively if the frequency reuse for interfering cells is above a predetermined frequency reuse number.
• the determination whether to implement the cyclical delay diversity is made in accordance with two criteria.
• a first criteria comprises frequency reuse plan information for interfering cells;
• a second criteria comprises interference power as measured at the wireless terminal.
• a determination not to implement the cyclical delay diversity is made if either a first criteria or the second criteria indicates that cyclical delay diversity is not necessary to obtain signal gain for the wireless terminal.
• a determination to implement the cyclical delay diversity is made if both the first criteria and the second criteria indicate that cyclical delay diversity is desirable to obtain the signal gain for the wireless terminal.
• the technology has the effect of implementing the cyclical delay diversity for the wireless terminal in a noise-dominated area of a cell served by the radio base station, but not implementing the cyclical delay diversity for the wireless terminal in an interference-dominated area of the cell served by the radio base station.
• the radio base station makes the determination whether to implement the cyclical delay diversity.
• a controller of the radio base station can make the determination.
• the wireless terminal can make the determination whether to implement the cyclical delay diversity.
• the wireless terminal communicates the determination to the radio base station, so that the radio base station can implement or not implement the cyclical delay diversity as the case may be.
• Fig. 1 is a graph illustrating how, in the single-cell with flat channel scenario, the CDD can improve system performances for the frequency-domain scheduler.
• Fig. 2 is a graph illustrating how CDD does not provide any interesting gains in multi-cell scenario with frequency reuse equal to one.
• Fig. 3 is a diagrammatic view of an example embodiment wherein an indication of interference distribution is received from a wireless terminal and a cyclic delay diversity (CDD) implementation determination is made by a radio base station.
• CDD cyclic delay diversity
• Fig. 4 is a flowchart illustrating example acts or steps performed by CDD decision logic for the embodiment of Fig. 3.
• Fig. 5 is a diagrammatic view showing a network having cells, with each cell having a noise dominating area and an interference dominating area.
• Fig. 6 is a diagrammatic view of an example embodiment wherein a cyclic delay diversity (CDD) implementation determination is made by a wireless terminal.
• CDD cyclic delay diversity
• Fig. 7 is a flowchart illustrating example acts or steps performed by CDD decision logic for the embodiment of Fig. 6.
• Fig. 8 is a diagrammatic view of an example embodiment wherein a cyclic delay diversity (CDD) implementation determination is made on the basis of frequency reuse plan information for interfering cells.
• Fig. 9 is a diagrammatic view of an example embodiment wherein a cyclic delay diversity (CDD) implementation determination is made both on the basis of reported interference distribution and on the basis of frequency reuse plan information for interfering cells.
• CDD cyclic delay diversity
• Fig. 10 is a flowchart illustrating example acts or steps performed by CDD decision logic for the embodiment of Fig. 9.
• Fig. 11 is a diagrammatic view of yet another example embodiment wherein a cyclic delay diversity (CDD) implementation determination is made both on the basis of reported interference distribution and on the basis of frequency reuse plan information for interfering cells, and wherein the decision is distributed between a radio base station and a wireless terminal
• CDD cyclic delay diversity
• Fig. 12 is a flowchart illustrating example acts or steps performed by distributed CDD decision logic for the embodiment of Fig. 11.
• Fig. 13 is a flowchart illustrating example acts or steps performed by another embodiment.
• processors may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software.
• the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared or distributed.
• explicit use of the term "processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may include, without limitation, digital signal processor (DSP) hardware, read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage.
• DSP digital signal processor
• ROM read only memory
• RAM random access memory
• MIMO-OFDM Orthogonal Frequency Division Multiplexing is a technology that uses multiple antennas to transmit and receive radio signals.
• MIMO-OFDM allows service providers to deploy a Broadband Wireless Access (BWA) system that has Non-Line-of-Sight (NLOS) functionality.
• BWA Broadband Wireless Access
• NLOS Non-Line-of-Sight
• MIMO-OFDM takes advantage of the multipath properties of environments using base station antennas that do not have LOS.
• the determination whether to implement cyclical delay diversity is made in accordance with interference distribution at the wireless terminal, as such interference distribution is measured or otherwise perceived.
• plural transmit antennas of a radio base station are employed to implement the cyclical delay diversity for the connection.
• one or more indications of the interference distribution are received and used for making the determination whether or not to implement the cyclical delay diversity for the connection.
• Fig. 3 shows an example embodiment wherein the indication of interference distribution can take the form of information received from a wireless terminal.
• Fig. 3 shows a radio network 20 comprising radio base station 26 and wireless terminal 30 which communicate across a radio (air) interface 32.
• radio base station 26 comprises plural transmitters 34 0 through 34 n , as well as at least one receiver 36.
• the plural transmitters 34 0 through 34 n each have an associated transmit antenna 38 0 through 38 n .
• Receiver 36 has receive antenna 39.
• receiver 36 can be included in a transceiver (e.g., combined with one of the transmitters 34).
• Radio base station 26 can take the name and function of other comparably denominated nodes such as base station, base transceiver station (BTS), node_B, or
• radio base stations comprise the radio network 20. and that the plural radio base stations are connected to associated control nodes of the network, e.g., radio network controller (RNC) nodes in the case of UTRAN, for example.
• RNC radio network controller
• the radio network is illustrated as only comprising the radio base station 26. although it will be understood that the radio base station 26 is connected to one or more of these other nodes.
• transmissions from each radio base station covers a field (e.g., a cell).
• the radio base stations are inter-connected physically or logically. By logical connection it is meant that the radio base stations can exchange signals (including, for example, frequency reuse information) via other nodes such as radio network controller nodes, for example).
• the wireless terminal can be called by other names and comprise different types of equipment.
• the wireless terminal can also be called a mobile station, wireless station, or user equipment units (UEs). and can be equipment such as mobile telephones ("cellular" telephones) and laptops with mobile termination, and thus can be. for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network .
• UEs user equipment units
• a data stream destined for transmission from radio base station 26 to wireless terminal 30 (depicted by arrow 40) is applied to resource allocator/scheduler 42.
• the resource allocator/scheduler 42 serves to allocate resource blocks (e.g., a number of consecutive sub-carriers for a number of consecutive OFDM symbols) for the connection to which the data stream belongs.
• the radio base station 26 further comprises a cyclic delay diversity (CDD) controller, e.g., CDD controller 44.
• CDD cyclic delay diversity
• CDD controller 44 determines whether the data stream for the connection (as carried by the allocated resource blocks) is to be transmitted with or without cyclic delay diversity (CDD), e.g., is to be transmitted over one or more of the plural transmit antennas 38 0 through 38 n .
• CDD controller 44 is connected to CDD implementation unit 46.
• the CDD implementation unit 46 is shown in simplified form as comprising switches 48 1 through 48 n and delay elements 49 1 through 49 n .
• switch 48] When switch 48] is closed by CDD controller 44, the data stream for the connection is applied (after a time delay imposed by delay element 49i) to transmitter 34) and its antenna 38i.
• the data stream for the connection is applied to one or more successive transmitters and potentially to transmitter 34 n and its associated antenna 38 n .
• each of the transmit antenna 38 1 through 38 n can have a different delay or phase shift.
• FIG. 3 shows by arrow 5Oo the transmission of the data stream from radio base station 26 to wireless terminal 30 over radio interface 32.
• CDD cyclic delay diversity
• transmission of the data stream also occurs from one or more of the diversity antennas 38 1 through 38 n . as indicated by arrows 50, through 5O n .
• Arrows 5O 1 through 5O n are shown by broken lines in view of their optional nature (e.g., since transmission from diversity antennas 38
• the radio base station 26, and particularly CDD controller 44 makes the determination whether cyclic delay diversity (CDD) is to be implemented or not.
• CDD controller 44 as including CDD decision logic 52.
• the CDD decision logic 52 can comprise software (e.g., a coded set of instructions) executed by a processor or controller which makes the determination.
• the coded set of instructions can be stored in memory, e.g., in semiconductor memory (e.g., read only memory [ROM]) or other magnetic or electronic memory (e.g., on CD. floppy disk, etc.).
• the CDD decision logic 52 receives the aforementioned indication of interference distribution.
• the determination made by CDD decision logic 52 whether to implement the cyclical delay diversity can be made affirmatively if the indication of the interference distribution indicates that noise is a greater factor than interference for a signal to interference noise ratio (SINR) for the wireless terminal.
• SINR signal to interference noise ratio
• CDD decision logic 52 receives the indication of interference distribution from wireless terminal 30.
• the wireless terminal 30 of the embodiment of Fig. 3 comprises a transceiver 60 connected to antenna 62.
• the transceiver 60 receives the information transmitted over radio interface 32 from radio base station 26, and further comprises an interference distribution detector 64 which detects or measures the interference distribution as perceived by wireless terminal 30.
• the interference distribution can pertain to, be related, or be derived from the signal to interference noise ratio (SFNR).
• the wireless terminal 30 further comprises reporting unit 66 which processes or formats the indication of interference distribution for inclusion in a report message which is transmitted by transceiver 60 back to radio base station 26.
• Fig. 3 shows by arrow 68 the transmission of an interference distribution indication message to radio base station 26, which is received by receiver 36 and forwarded to CDD decision logic 52.
• Fig. 4 illustrates example acts or steps performed by CDD decision logic for the embodiment of Fig. 3.
• Act 4- 1 of the CDD decision logic of Fig. 4 reflects start of the cyclic delay diversity (CDD) decision process performed by CDD decision logic
• the CDD decision process can be triggered or started by several events, such as (for example) when the wireless terminal 30 judges it is close to a cell center by SINR measurement or the wireless terminal 30 is with multi-streams transmission in case of a spatial multiplex system.
• Act 4-2 involves each wireless terminal estimating or predicting the interference;
• act 4-3 involves each wireless terminal providing interference distribution feedback (e.g., an interference distribution indication message 68) to radio base station.
• Act 4-4 involves base station 26, and in particular CDD decision logic 52, deciding whether to turn on cyclic delay diversity (CDD) for each wireless terminal.
• CDD cyclic delay diversity
• Fig. 5 shows the interference distribution for a resource block in a multi- cell system with frequency reuse equal to one (e.g., 1 : 1 ). Due to the co-channel interference, each cell can have two different areas i.e., centrally-located noise dominating area 90 and peripherally-located interference dominating area 92. The noise dominating area 90 is marked with stippling; the interference dominating area 92 is marked with hatching. Through the measurement of the channel by the wireless terminal, the wireless terminal can decide whether it is located in an interference or noise dominating area, e.g., in interference dominating area 92 or noise dominating area 90. For wireless terminals in the different areas, different processes can be employed.
• the cyclic delay diversity can introduce more frequency domain variation and accordingly the cyclic delay diversity (CDD) is turned on.
• CDD cyclic delay diversity
• the frequency and time allocations to map information for a certain wireless terminal to resource blocks is determined by the radio base station (e.g., NodeB) scheduler and may depend, e.g., on the frequency-selective CQI (channel-quality indicator) reported by the wireless terminal to the radio base station.
• the radio base station e.g., NodeB
• CQI channel-quality indicator
• CDD decision logic 52 can decide to turn on cyclic delay diversity (CDD).
• Act 4-5 of Fig. 4 reflects a turning on or implementation of cyclic delay diversity (CDD).
• the CDD decision logic 52 can decide to turn off (e.g., not implement) cyclic delay diversity (CDD). Act 4-6 of Fig.
• CDD 4 reflects a turning off or non-implementation of cyclic delay diversity (CDD).
• the system e.g., radio base station 26
• CDD implementation unit 46 can then further employ frequency domain scheduler 42 and CDD implementation unit 46 to obtain the multi-user diversity gain.
• the CDD may be either fixed cyclic delay diversity (CDD) or adaptive cyclic delay diversity (CDD).
• CDD fixed cyclic delay diversity
• CDD adaptive cyclic delay diversity
• 'fixed delay it is meant that the delay from one delay element 49 to another, and thus the delay from one transmit antenna 38 to another, is fixed or of the same delay interval.
• adaptive it is meant that the delay can vary between antennas and/or over time. If the system employs fixed cyclic delay diversity (CDD), other than the interference distribution indication no further feedback from wireless terminal is needed.
• Fig. 4 shows as optional act 4-4A, the radio base station obtaining such further feedback from the wireless terminal. It will also be appreciated that optionally such further feedback may instead be obtained at the time of obtaining the interference distribution (at the time of act 4-3).
• Fig. 6 shows another example embodiment wherein the indication of interference distribution can take the form of information received from a wireless terminal.
• the cyclic delay diversity (CDD) implementation determination is made by wireless terminal 30(6).
• wireless terminal 30(6) comprises CDD decision logic 70.
• the CDD decision logic 70 of wireless terminal 30(6) receives the indication of interference distribution [e.g., the signal to interference noise ratio (SINR)] and uses the indication of interference distribution, in a manner such as that described hereinafter, to make the determination whether cyclic delay diversity (CDD) is to be implemented.
• the determination made by CDD decision logic 70 whether to implement the cyclical delay diversity can be made affirmatively if the indication of the interference distribution indicates that noise is a greater factor than interference for a signal to interference noise ratio (SINR) for the wireless terminal.
• SINR signal to interference noise ratio
• the reporting unit reports as message
• CDD controller 44 operates CDD implementation unit 46 so that one or more transmit antenna 38] through 38 n arc operative, as the case may be. Only transmit antenna 38o is utilized if CDD is not implemented, whereas one or more of transmit antenna 38) through 38 n may be utilized when CDD is implemented.
• Fig. 7 illustrates example acts or steps performed by CDD decision logic for the embodiment of Fig. 6.
• Act 7- 1 of the CDD decision logic of Fig. 7 reflects start of the cyclic delay diversity (CDD) decision process performed by CDD decision logic 70.
• the CDD decision process can be triggered or started by several events, such as (for example) when the wireless terminal 30 judges it is close to a cell center by SINR measurement or the wireless terminal 30 is with multi-streams transmission in case of a spatial multiplex system.
• Act 7-2 involves each wireless terminal estimating or predicting the interference.
• Act 4-3 involves each wireless terminal judging, according to the distribution of the interference perceived or measured by the wireless terminal, whether it is located at an area in which noise dominates the whole interference (e.g., noise dominating area 90 of Fig. 5) or an area in which the inter-cell interference dominates the whole interference (e.g., interference dominating area 92 of Fig. 5).
• the CDD decision logic 70 of wireless terminal decides to turn on CDD if the white noise dominates the whole interference, but to turn off (e.g., not implement) CDD if the interference is dominate.
• each wireless terminal then provides feedback to the radio base station of the wireless terminal's decision whether or not to turn on CDD, e.g..
• a CDD decision message 72 (see Fig. 6).
• the radio base station 26(6) Upon receipt of the CDD decision message 72 from wireless terminal 30(6), the radio base station 26(6) responds accordingly. If CDD is to be turned on, as act 7-5 the system (e.g., radio base station) further employs its frequency domain scheduler 42 and CDD implementation unit 46 to obtain the multi-user diversity gain. On the other hand, if the decision made by CDD decision logic 70 is negative, as act 7-6 the CDD is not turned on. [0055] In like manner as Fig. 4, Fig. 7 shows as optional act 7-4A, the radio base station obtaining such further feedback from the wireless terminal as may be needed for implementation of adaptive CDD. It will also be appreciated that optionally such further feedback may instead be obtained at the time of obtaining the interference decision (at the time of act 7-4).
• the indication of interference distribution can take the form of frequency reuse plan information for interfering cells.
• the radio base station 26(8) of the embodiment of Fig. 8 comprises CDD decision logic 52.
• Fig. 8 further shows CDD decision logic 52 as having access to network information 76, which particularly includes at least relevant portions of a frequency reuse plan for the radio network 20.
• the frequency reuse plan for the radio network 20 can (in at least some example implementations) be received via network signaling or other messages from one or more other nodes, e.g., from other radio network nodes.
• the determination the determination to implement the cyclical delay diversity can be made affirmatively by CDD decision logic 52 if the frequency reuse for interfering cells is above a predetermined frequency reuse number.
• the determination whether to implement the cyclical delay diversity is made in accordance with two criteria.
• a first criteria comprises frequency reuse plan information for interfering cells (similar to that of the embodiment of Fig. 8);
• a second criteria comprises interference power as measured (or otherwise perceived) at the wireless terminal (similar to that of the embodiment of Fig. 3).
• the radio base station 26(9) of Fig. 9, like the radio base station 26(8) of Fig. 8. includes network information 76.
• Fig. 10 shows an example of logic which is executed or otherwise utilized by CDD decision logic 52 for the embodiment of Fig. 9.
• Fig. 10 illustrates example acts or steps performed by CDD decision logic 52 for the embodiment of Fig. 9.
• Act 10-1 of the CDD decision logic of Fig. 10 reflects start of the cyclic delay diversity (CDD) decision process.
• the CDD decision process can be triggered or started by several events , such as (for example) when the wireless terminal 30 judges it is close to a cell center by SINR measurement or the wireless terminal 30 is with multi- streams transmission in case of a spatial multiplex system.
• the CDD decision logic obtains the frequency reuse plan of the network (if not already known).
• the frequency reuse plan is shown in Fig. 9 as being stored in network information memory 76.
• the frequency reuse plan can be configured in network information memory 76, or can be fetched or periodically updated by network signaling (indicated by arrow 78) which carries the frequency reuse plan.
• the CDD decision logic determines whether to turn on cyclic delay diversity (CDD) based on the frequency reuse plan. In particular, the CDD decision logic checks for the frequency(ies) involved in the resource block allocated to the connection by resource allocator/scheduler 42, and determines to what extent that/those frequency(ies) are utilized by other cells.
• CDD cyclic delay diversity
• the CDD decision logic obtains the interference distribution information from the wireless terminal.
• the interference distribution information may be obtained through an interference distribution indication message 68 such as that depicted in Fig. 3. for example.
• the CDD decision logic determines whether to turn on cyclic delay diversity (CDD) based on interference power perceived or experienced at the wireless terminal.
• the CDD decision logic makes a determination to implement the cyclical delay diversity if the interference distribution indication message indicates that the wireless terminal is in a noise- dominated area of a cell served by the radio base station.
• the CDD decision logic adds cyclic delay diversity (CDD) to one or more of the transmits antenna 38) through 38 n on the specific resource blocks utilized by the connection.
• CDD cyclic delay diversity
• a determination not to implement the cyclical delay diversity is made if either a first criteria (frequency reuse plan check of act 10-3) or the second criteria
• interference distribution check of act 10-6 indicates that cyclical delay diversity is not necessary to obtain signal gain for the wireless terminal.
• a determination to implement the cyclical delay diversity is made if both the first criteria (frequency reuse plan check of act 10-3) and the second criteria (interference distribution check of act 10-6) indicate that cyclical delay diversity is desirable to obtain the signal gain for the wireless terminal.
• the example acts of the CDD decision logic of Fig. 10 can be performed by CDD decision logic 52 of radio base station 26(9).
• the CDD decision logic can be distributed between radio base station 26(11) and wireless terminal 30( 1 1 ) and can operate in the manner depicted by Fig. 12.
• the embodiment of Fig. 1 1 and mode of Fig. 12 are essentially similar to Fig. 9 and Fig. 10, respectively, except for differing numbered elements and differing suffixed action numbers.
• Fig. 1 1 and mode of Fig. 12 are essentially similar to Fig. 9 and Fig. 10, respectively, except for differing numbered elements and differing suffixed action numbers.
• CDD decision logic 52(1 1) shows CDD decision logic being distributed between CDD decision logic 52(1 1) in radio base station 26(1 1 ) and CDD decision logic 70(1 1) of wireless terminal 30(1 1 ).
• CDD decision logic 52( 1 1) has made its determination based on frequency reuse plan (as act 11-3), as act 11-5(12) the CDD decision logic 52( 1 1 ) checks a report of the decision made by CDD decision logic 70( 1 1) based on interference distribution. If the CDD decision logic 70( 1 1 ) has determined that it thinks CDD should be turned on based on interference power measured or experienced at wireless terminal 30(1 1 ).
• the CDD decision logic 52( 1 1) adopts the decision of CDD decision logic 70(11 ) and turns on the CDD (see act 12-7).
• the CDD decision logic 70(11) has determined that it thinks CDD is not necessary based on interference power measured or experienced at wireless terminal 30(11)
• the CDD decision logic 52(11) adopts the decision of CDD decision logic 70(1 1) and does not turn on the CDD (see act 12-4).
• Act 10-8 of the CDD decision logic includes determining whether to turn on either fixed delay for the cyclic delay diversity (CDD) or an adaptive delay.
• fixed delay it is meant that the delay from one delay element 49 to another, and thus the delay from one transmit antenna 38 to another, is fixed or of the same delay interval.
• adaptive it is meant that the delay can vary between antennas and/or over time.
• the radio base station may also obtaining such further feedback from the wireless terminal as may be needed for implementation of adaptive CDD.
• CDD can be triggered based on the interference measurement and/or based on the inter-cell communication or inter-cell coordination.
• each radio base station can obtain the frequency reuse or ICIC planning on different resource blocks of the other cells, based on the estimated or predicted interference.
• SINR signal to interference noise ratio
• expression (2) interference (power) is that which comes from allocation of the same resource block to other wireless terminals in the interfering cells.
• total noise and “total noise power” includes both interference power both and white noise power.
• Interference power comes from the allocation of the same resource block to other wireless terminals in interfering cells.
• the ratio of interference power to the total noise power is used to determined whether to apply/implement cyclic delay diversity (CDD).
• CDD cyclic delay diversity
• the interference power can be estimated as follows: A base station employs various pilot signal values, which other base stations cannot use in other cells, and which can be used to estimate the white noise power. Yet other pilot signal values are employed not only by a reference cel ⁇ ase station, but also by base stations of interfering cells, which can be used to estimate the total noise power. Thus, the interference power equals the total noise power less the white noise power.
• the frequency planning can be done by considering the CDD decision of the interfering cells.
• the system can then employ frequency domain scheduler to obtain the multi-user diversity gain.
• different cells can have a different frequency reuse plan, but the different frequency reuse can lead to different co-channel interference distribution, which have a big contribution to the usage of CDD.
• each base-station obtains the frequency reuse plan on different resource blocks of the other cells. Then, as act 13-2, and based on the statistics of the channel quality indication (CQI) of the wireless terminal or other feedback about the interference, the base station can judge the scenario of each wireless terminal, e.g., user position (cell center or cell edge), geometric factor (inter-cell interference dominated or noise dominated), etc. Based on the above information, as act 13-3 the base-station can decide for which wireless terminals to turn on cyclic delay diversity (CDD).
• CDD channel quality indication
• CDD is to be implemented, as act 13-5 the system can then further employ its frequency domain scheduler (e.g., resource allocator/scheduler 42) and CDD implementation unit 46 to obtain the multi-user diversity gain. Otherwise (act 13-6) the CDD is turned off.
• frequency domain scheduler e.g., resource allocator/scheduler 42
• CDD may be turned on only for some of users, depending on the interference measurements or prediction, but for other users be turned off.
• the frequency reuse planning can be decided with CDD decision jointly. Whether to turn on CDD or not can be either decided by base station or wireless terminal, which involves different signalling or feedbacks depending on which unit is the decision maker.
• the base station can take a static-CDD decision for each user with almost no increase of the signalling overhead.
• the present technology exploits the benefits from both cyclic delay diversity (CDD) and frequency reuse technologies for OFDM-MIMO system in multi- cell scenario.
• CDD cyclic delay diversity
• frequency reuse technologies for OFDM-MIMO system in multi- cell scenario.
• the technology thus has many advantages.
• the technology is an interference-dependent application of CDD technologies, which switches CDD on in the noise dominating area, but switches CDD off in the interference dominating area. Since CDD only bring gains in some specific scenarios, the technology reduces useless CDD applications and therefore reduces the related system signalling overhead but still keeps CDD support for those users that can gain by using CDD.
• the technology is also a joint frequency reuse and
• Frequency reuse plan of an OFDM system can have an important contribution to the co-channel interference, but enables a cellular system to handle a huge number of calls with a limited number of channels.
• the switching of CDD on/off based on interference distribution can jointly together with frequency reuse, i.e., with the knowledge of frequency reuse plan, well adapt the CDD potential gain in frequency domain flat SINR scenario.
• this technology is compatible with and can exploit the OFDM system performances with MIMO and frequency reuse technologies.
• the technology can be applied to and used in conjunction with 3GPP LTE [3GPP TR 25.814, "3rd
• CDD decision logic 52 and CDD decision logic 70 can be performed such devices as a controller or processor as those terms are expansively defined herein.
• This invention is not limited to any particular way of obtaining interference distribution information, since the person skilled in the art knows how to obtain interference information in various ways (all of which are encompassed herein). Similarly, the invention is not limited to any particular way of applying delay or phase shift parameters to the CDD implementation. Several example ways are described by documents listed and/or incorporated herein.

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• 2007
  • 2007-08-01 US US11/832,314 patent/US8131228B2/en not_active Expired - Fee Related
• 2008
  • 2008-07-01 BR BRPI0814458-3A2A patent/BRPI0814458A2/pt not_active IP Right Cessation
  • 2008-07-01 EP EP08779388.1A patent/EP2174429B1/en not_active Not-in-force
  • 2008-07-01 WO PCT/SE2008/050810 patent/WO2009017447A2/en not_active Ceased
  • 2008-07-01 CN CN200880110408A patent/CN101809888A/zh active Pending
  • 2008-07-01 JP JP2010519174A patent/JP5226786B2/ja not_active Expired - Fee Related

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