Adaptive uplink/downlink timeslot assignment in a hybrid wireless time division multiple access/code division multiple access communication system

Abstract

A wireless network device may receive a first list indicating a first assignment for uplink and downlink time intervals in a time division duplex (TDD) frame and determine at least first downlink time intervals based on the first list. The device may receive a second list indicating a second assignment for uplink and downlink time intervals in a TDD frame and determine at least first uplink time intervals based on the second list. The device may determine at least second downlink time intervals and second uplink time intervals based on a third list, wherein the third list indicates a third assignment for uplink and downlink time intervals in a TDD frame, and wherein the second downlink time intervals include downlink time intervals of at least the first downlink time intervals and the second uplink time intervals include uplink time intervals of at least the first uplink time intervals.

Claims

1. A first wireless device comprising: a receiver configured to receive a first list indicating a first assignment for uplink and downlink time intervals in a time division duplex (TDD) frame; a controller configured to determine at least first downlink time intervals for communication in a TDD frame based on the first list; the receiver further configured to receive a second list indicating a second assignment for uplink and downlink time intervals in a TDD frame; the controller further configured to determine at least first uplink time intervals for communication in a TDD frame based on the second list; the controller further configured to determine at least second downlink time intervals and second uplink time intervals for communication in a TDD frame based on a third list, wherein the third list indicates a third assignment for uplink and downlink time intervals in a TDD frame, and wherein the second downlink time intervals include downlink time intervals of at least the first downlink time intervals and the second uplink time intervals include uplink time intervals of at least the first uplink time intervals; and the receiver configured to communicate, with a second wireless device during at least one TDD frame for communication, in the downlink based on at least the second downlink time intervals and, in the uplink based on at least the second uplink time intervals.

2. The first wireless device of claim 1, wherein the third list dynamically changes.

3. The first wireless device of claim 2, wherein the third list dynamically changes on a TDD frame basis.

4. The first wireless device of claim 1, wherein the first list and the second list are received from the second wireless device.

5. The first wireless device of claim 1, wherein the first list is received from the second wireless device and the second list is received from a third wireless device.

6. The first wireless device of claim 1, wherein the first list is received from the third wireless device and the second list is received from the second wireless device.

7. The first wireless device of claim 1, wherein each time interval includes at least one time slot.

8. The first wireless device of claim 1, wherein the first wireless device and the second wireless device are network nodes.

9. The first wireless device of claim 1, wherein the receiver is further configured to receive the third list.

10. The first wireless device of claim 1, wherein at least one of the first assignment and the second assignment is the same as the third assignment.

11. A method comprising: receiving, by a first wireless device, a first list indicating a first assignment for uplink and downlink time intervals in a time division duplex (TDD) frame; determining, by the first wireless device, at least first downlink time intervals for communication in a TDD frame based on the first list; receiving, by the first wireless device, a second list indicating a second assignment for uplink and downlink time intervals in a TDD frame; determining, by the first wireless device, at least first uplink time intervals for communication in a TDD frame based on the second list; determining, by the first wireless device, at least second downlink time intervals and second uplink time intervals for communication in a TDD frame based on a third list, wherein the third list indicates a third assignment for uplink and downlink time intervals in a TDD frame, and wherein the second downlink time intervals include downlink time intervals of at least the first downlink time intervals and the second uplink time intervals include uplink time intervals of at least the first uplink time intervals; and communicating, by the first wireless device with a second wireless device during at least one TDD frame for communication, in the downlink based on at least the second downlink time intervals, and in the uplink based on at least the second uplink time intervals.

12. The method of claim 11, wherein the third list dynamically changes.

13. The method of claim 11, wherein the third list dynamically changes on a TDD frame basis.

14. The method of claim 11, wherein the first list and the second list are received from the second wireless device.

15. The method of claim 11, wherein the first list is received from the second wireless device and the second list is received from a third wireless device.

16. The method of claim 11, wherein the first list is received from the third wireless device and the second list is received from the second wireless device.

17. The method of claim 11, wherein each time interval includes at least one time slot.

18. The method of claim 11, wherein the first wireless device and the second wireless device are network nodes.

19. The method of claim 11, further comprising: receiving, by the first wireless device, the third list.

20. The method of claim 11, wherein at least one of the first assignment and the second assignment is the same as the third assignment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a wireless spread spectrum CDMA system.

(2) FIG. 2 illustrates timeslots in repeating frames.

(3) FIG. 3 illustrates cross cell interference.

(4) FIG. 4 is an availability list.

(5) FIG. 5 is a flow chart for generating an availability list using base station to base station (BS-BS) and user equipment to user equipment (UE-UE) interference cells.

(6) FIG. 6 is an example of a cross interference cell list.

(7) FIG. 7 is a table showing a hypothetical timeslot allocation for each cell.

(8) FIG. 8 is an availability list for cell 1 constructed using FIGS. 6 and 7.

(9) FIG. 9 is a flow chart for producing an availability list using only BS-BS interference cells.

(10) FIG. 10 is an illustration of a BS-BS cross interference list.

(11) FIG. 11 is a flow chart for producing an availability list using only UE-UE interference cells.

(12) FIG. 12 is a UE-UE cross interference list.

(13) FIGS. 13 and 14 are flow charts using base station and user equipment interference measurement to determine timeslot availability.

(14) FIG. 15 is an illustration of a user equipment specific availability list.

(15) FIGS. 16 and 17 are flow charts for using only interference measurements to determine timeslot availability.

(16) FIGS. 18, 19 and 20 are flow charts for determining timeslot availability using hybrid approaches.

(17) FIG. 21 is a flow chart of a timeslot assignment approach.

(18) FIG. 22 is a flow chart of availability list updating.

(19) FIG. 23 is the updated table of FIG. 7.

(20) FIG. 24 is an updated availability list for cell 7 based on FIG. 23.

(21) FIG. 25 is a centralized architecture embodiment.

(22) FIG. 26 is a decentralized architecture embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(23) Although the following describes timeslot assignment in context of a TDD/CDMA system, the same timeslot elimination procedures and availability lists can be applied to a hybrid TDMA/CDMA system where uplink and downlink communications occur in the same timeslot in a cell.

(24) FIG. 4 illustrates an availability timeslot list 76. Along the horizontal axis, each timeslot is listed as S1, S2, . . . , SN. Along the vertical axis, each cell, listed here by the subscript of its associated base station's reference number, is listed for both the uplink and downlink. Each row indicates the timeslot availability for either the uplink or the downlink for a cell. Timeslots not available are indicated with an X. Available timeslots are left empty.

(25) One procedure for generating the availability list is shown in FIG. 5 and is explained in conjunction with FIGS. 6, 7 and 8. Initially, the cross interference between each cell pair is measured. Initially, base station 30.sub.1-30.sub.11 to base station 30.sub.1-30.sub.11 (BS-BS) interfering cells are determined, step 77. BS-BS interfering cells are cells where a base station's 30.sub.1-30.sub.11 transmissions interfere with another base station's 30.sub.1-30.sub.11 reception.

(26) Each cell determines its BS-BS interfering cells by estimating interference from the other cells. One approach estimates the BS-BS interfering cells using pre-measured link gains between the base stations 30.sub.1-30.sub.11. If the estimated interference exceeds a threshold, the base stations' cells are considered BS-BS interfering cells, step 77. Based on the threshold comparison, BS-BS interfering cells are determined and stored in a cross interference cell list 84 as illustrated in FIG. 6. The vertical axis of the cross interference cell list 84 has each cell. The horizontal axis has potential cross interfering cells. A cell that BS-BS interferes with another cell is marked in the appropriate box by an I, step 79. For example, since communications in cell 2 cross interfere with cell 1, the first row, second column box is marked with an I. Since a cell does not interfere with itself, these boxes are marked by an X.

(27) Additionally, cells where UEs 32.sub.1-32.sub.n may interfere with other UEs 32.sub.1-32.sub.n are determined, step 78. Due to the relatively low EIPR of UEs 32.sub.1-32.sub.n, the UE-UE interfering cells are in close geographic proximity, such as being adjacent. One UE's 32.sub.1 uplink transmission can interfere with a neighboring cell's UE reception, as shown in FIG. 3. Since cells with close geographic proximity may have UEs 32.sub.1-32.sub.n which may interfere with each other, these cells are also listed as interfering cells. In FIG. 6, the UE-UE interfering cells which were not BS-BS interfering cells are marked with an I*, step 79.

(28) Using the cross interference cell list 84, for each cell, the potential cross interference cells are determined, step 78. For a particular cell in the vertical axis, each cell in the corresponding row marked with an I or I* is a cross interference cell. For instance, cell 1 is potentially cross interfered by cells 2, 3, 5, 6, 9 and 10. For each cross interference cell, the timeslot allocation is determined. For instance, using the hypothetical timeslot allocation of table 86 of FIG. 7, cell 2 is allocated downlink timeslots 1 and 2 and uplink timeslot 9. For each downlink timeslot allocated in a cross interference cell, a corresponding uplink timeslot is eliminated, step 80. To illustrate using FIGS. 6, 7 and 8, for cell 1, cell 2's allocated downlink timeslot 1 eliminates timeslot 1 from cell 1's available uplink timeslots as shown by an X in cell 1's availability list 88 of FIG. 8.

(29) For each uplink timeslot allocated in a cross interference cell, a corresponding downlink timeslot is eliminated, step 82. To illustrate for cell 1, cell 2's uplink timeslot 9 eliminates that timeslot from cell 1's possible downlink timeslots as shown in cell 1's availability list 88. After eliminating the appropriate timeslots due to the cross interference cells, an availability list 76 for each cell is produced, step 90. As a result, uplink and downlink timeslots used in cross inference cells are made unavailable reducing cross cell interference.

(30) To relax the assignment conditions, either only the BS-BS interfering cells or only the UE-UE interfering cells are considered. These approaches may lead to freeing up more resources for each cell. However, the looser criteria may result in unacceptable interference levels with respect to some users.

(31) FIG. 9 is a flow chart for producing an availability list using only BS-BS interference cells. The BS-BS interference cells are identified, step 122. A BS-BS cross interference list 132 is produced, such as in FIG. 10. If a cell uses a timeslot for the uplink, that slot is eliminated for use by BS-BS interfering cells for the downlink, step 126. Conversely, if a cell uses a timeslot for the downlink, that slot is eliminated for use by BS-BS interfering cells for the uplink, step 128. A list of available timeslots is produced for each cell, step 130. Although this approach more aggressively uses the system's resources, unacceptable downlink interference may be suffered by some users.

(32) FIG. 11 is a flow chart for producing an availability list using only UE-UE interference cells. The UE-UE interference cells are identified, step 134. A UE-UE cross interference list 142 is produced, such as in FIG. 12. If a cell uses a timeslot for the downlink, that slot is eliminated for use by UE-UE interfering cells for the uplink, step 136. Conversely, if a cell uses a timeslot for the uplink, that slot is eliminated for use by UE-UE interfering cells for the downlink, step 138. A list of available timeslots for each cell is produced, step 140. This approach may result in unacceptable uplink interference levels for some users.

(33) Another approach for determining available timeslots uses interference measurements of timeslots, such as by interference signal code power (ISCP). The interference measurements may be taken at the base stations 30.sub.1-30.sub.11, UEs 32.sub.1-32.sub.n or both.

(34) FIG. 13 is a flow chart using base station and UE interference measurements to determine available timeslots for each UE 32.sub.1-32.sub.n. For a particular cell, the interference level in each timeslot is measured at the base station 30.sub.1, step 144. Each of the cell's UEs 32.sub.1, 32.sub.3-32.sub.4 also measure interference levels in each timeslot, step 146. The timeslot interference measurements by the base stations are used to determine the availability of uplink timeslots. The downlink timeslot availability is determined on a UE by UE basis (UE specific basis).

(35) For the uplink, if the base station's measured interference exceeds a threshold in a timeslot, that timeslot is eliminated for the uplink, step 148. For the downlink, each UE 32.sub.1, 32.sub.3, 32.sub.4 eliminates downlink timeslots for its use, if that UE's interference measurement exceeds a threshold, step 150. An availability list 154 is produced showing the available uplink timeslots and the available downlink timeslots for each UE as illustrated in FIG. 15, step 152.

(36) Although two cells are adjacent, the location of specific UEs 32.sub.1-32.sub.n in the cells may be distant. To illustrate using FIG. 1, cell 1 and cell 2 are adjacent. However, a UE 32.sub.4 is distant from cell 2. Accordingly, if UE 32.sub.2 in cell 2 uses a slot for uplink, it will most likely not interfere with the downlink reception of UE 32.sub.4. However, UE 32.sub.2 uplink transmissions would likely interfere with UE 32.sub.1 downlink transmissions. As a result, a more aggressive resource allocation is available using a UE specific availability list 154. One drawback is the increased signaling required. Due to UE mobility and other cells' reassignments, the interference measurements must be updated and signaled to the base station 30.sub.1-30.sub.11 on a frequent basis.

(37) FIG. 14 is a flow chart using base station and UE interference measurements to determine non-UE specific available timeslots. The base station 30.sub.1 measures the interference in each timeslot, step 144, and so does each UE 32.sub.1, 32.sub.3, 32.sub.4, step 146. For the uplink, if the base station measured interference exceeds a threshold in a timeslot, that timeslot is eliminated, step 148. For the downlink, if any of that cell's UEs measured interference in a timeslot exceeds the threshold, that timeslot is eliminated for the downlink, step 156. Using the eliminated timeslots, an availability list 88 for each cell is produced, such as per FIG. 8. Since the UE measurements are effectively combined, missing UE interference measurements are not critical to resource unit assignment.

(38) FIGS. 16 and 17 are flow charts using only UE interference measurements to determine available timeslots. In a cell, each UE measures the interference in each timeslot, step 160. For the uplink, if any UE interference measurement exceeds the threshold, that timeslot is eliminated for the uplink, step 160. Alternately, to reduce the number of eliminated uplink timeslots, only the timeslots where most of the UEs have unacceptable interference are eliminated from the uplink, step 160. If only a few UEs report unacceptable interference, it is assumed these UEs are at the fringe of the cell and are not representative of the overall cell conditions.

(39) Using a UE specific assignment approach as in FIG. 16, each UE 32.sub.1, 32.sub.3, 32.sub.4 has its own set of available downlink timeslots, such as per FIG. 15. For each UE 32.sub.1, 32.sub.3, 32.sub.4, a downlink timeslot is eliminated, if that UE interference measurement on the timeslot exceeds a threshold, step 164. A UE specific availability list 150 is produced, step 166.

(40) A non-UE specific approach is shown in FIG. 17. If any UE or most UEs' interference measurement exceeds a threshold in the timeslot, that timeslot is eliminated for the downlink, step 168. An availability list 88, such as in FIG. 8, is produced for the entire cell.

(41) FIGS. 18, 19 and 20 are timeslot availability determination approaches, using hybrid BS-BS interference, UE-UE interference and interference measurement approaches. FIGS. 18 and 19 use BS-BS interference cells and UE interference measurements. The BS-BS interfering cells are determined, step 172. Each UE 32.sub.1, 32.sub.3, 32.sub.4 measures the interference in each timeslot, step 174. For the uplink, timeslots are eliminated, if a BS-BS interfering cell uses it for the downlink, step 176.

(42) Downlink availability is determined on a UE by UE or a collective basis. Using a UE by UE basis per FIG. 18, each UE 32.sub.1, 32.sub.3, 32.sub.4 compares each timeslot interference measurement to a threshold. If a timeslot measurement exceeds the threshold, that timeslot is eliminated for that UE 32.sub.1, 32.sub.3, 32.sub.4 in the downlink, step 178. A UE specific availability list 150, such as FIG. 15, is produced, step 180.

(43) Using a collective basis per FIG. 19, if any UE timeslot interference measurement exceeds a threshold, that timeslot is eliminated for the downlink for the cell, step 182. An availability list 88, such as FIG. 8, is produced, step 184.

(44) FIG. 20 uses UE-UE interference cells and base station interference measurements. A cell's base station 30.sub.1 measures the interference levels in each timeslot, step 186. UE-UE interfering cells are identified, step 188. For the uplink, eliminate uplink timeslots, if that timeslot's interference exceeds a threshold, step 190. For the downlink, a downlink timeslot is eliminated, if a UE-UE interfering cell uses it for the uplink, step 192. Based on the eliminated timeslots, an availability list 88, such as FIG. 8, is produced.

(45) For sectored cells, the cross interference list and availability lists 84 are constructed for each sector within the cells. The cross interference between all cell's sectors is determined. Although the following discussion focuses on non-sectorized cells, the same approach also applies to sectorized cells where the assigning is performed on a per sector basis instead of a per cell basis.

(46) Using the availability list 76, each base station 30.sub.1-30.sub.n is assigned timeslots to support its communications using the procedure of FIG. 21. Initially, a request for an additional allocated timeslot or timeslots is made, step 92. Referring to that base station's availability list 76, corresponding available timeslots are assigned. To illustrate using the availability list 88 of FIG. 8, the base station 30.sub.1 requires both an additional allocated downlink and an uplink timeslot. The available uplink timeslots are slots 4 and 7-16 and the available downlink timeslots are slots 1-3, 5, 6, 8, 10-13 and 16. One uplink timeslot and downlink timeslot will be assigned out of the corresponding available downlink and uplink timeslots. If a UE specific availability list 150 is used, the downlink assignment is based on the UE 32.sub.1-32.sub.n requiring the downlink resource unit(s).

(47) Since the base stations 30.sub.1-30.sub.n need to dynamically assign and release timeslots due to varying uplink/downlink demand, the information in the availability list 76 requires updating. For approaches using interference measurements, the updates are performed by updating the measurements and the lists.

(48) For BS-BS and UE-UE approaches, this procedure is shown in FIG. 22. Initially, the cross interference cells are identified for each assigned or released timeslot, step 96. For each assigned downlink timeslot, the corresponding timeslots in the cross interference cells are eliminated for the uplink, step 98. Conversely, if the uplink timeslot is assigned, the corresponding timeslots in the cross interference cells for the downlink are eliminated, step 100. To illustrate using FIGS. 23 and 24, the base station 30.sub.6 associated with cell 6 assigns timeslot 7 for the downlink, D*, and timeslot 8 for the uplink, U*, as indicated in table 106 of FIG. 23. The cross interference cells are cells 1, 2, 5 and 7. As shown for cell 7's availability list 107 of FIG. 24, timeslot 7 is eliminated for the uplink and timeslot 8 is eliminated for the downlink, both marked as X*.

(49) If a downlink timeslot was released, the corresponding timeslots in the cross interference cells are freed for the uplink unless unavailable for other reasons, such as being used as a downlink timeslot in another cross interference cell, step 102. For instance, if timeslot 6 of cell 6 is released as indicated in table 106 as D**, cell 1's uplink timeslot 6 is not made available. Cell 9 is a cross interference cell to cell 1, which also uses downlink timeslot 6. By contrast, for cell 7, the release of downlink timeslot 6 frees the cell for uplink communications as shown in cell 7's availability list 108 by an R. If an uplink timeslot was released, the corresponding timeslots in the cross interference cells are freed for the downlink unless unavailable for other reasons, step 104.

(50) One approach for using uplink/downlink timeslot assignment is shown in FIG. 25 using a centralized architecture. The radio network controller (RNC) 110 has a resource allocation device 11 to assign or release a timeslot based on user demand. If assigning, the resource allocation device 116 in the RNC 110 assigns an appropriate timeslot using availability list 76, stored in its memory 117, per the procedure of FIG. 21. The selected timeslots and channel codes are communicated to the base station 30.sub.1-30.sub.N and UEs 32.sub.1-32.sub.N, via the node-B timeslot assignment and release device 112.sub.1-112.sub.n. If releasing a timeslot, the RNC resource allocation device 116 releases that timeslot and updates the availability list 76. Accordingly, updating of the availability list 76 is centralized by occurring at the RNC 110.

(51) Another approach for uplink/downlink timeslot assignment is shown in FIG. 26 using a decentralized architecture. Each node-B 122.sub.1-122.sub.N has its own timeslot controller 120.sub.1-120.sub.n. When a timeslot assignment and release device 112.sub.1-112.sub.n requests timeslots for a communication, the node-B's timeslot controller 120.sub.1-120.sub.n selects an appropriate timeslot from its availability list 76, as stored in its memory 121.sub.1. The stored availability list 76 to reduce its size may only contain the available timeslots for that node-B's cell(s). Conversely, the stored availability list 76 may contain the availability for all the RNC's cells. The decentralized approach allows for faster updates.

(52) The selected timeslot is assigned to the communication by the timeslot assignment and release device 112.sub.1-112.sub.n. To update the lists 76, that node-B 122.sub.1-122.sub.n updates its list 76. The assigned and released timeslots are also sent to the RNC 110. The RNC 110 directs the appropriate timeslot update information to the other cells. The timeslot information either contains an updated availability list 76 or merely the changes to the list 76. If only the changes are sent, each cell's controller 120.sub.1-120.sub.n updates its own availability list 76 with that information. The type of timeslot information sent is based on the processing and signaling requirements of the system.

(53) Assigning uplink/downlink timeslots is adaptable to systems supporting differing signaling rates. For systems supporting only slow network signaling, the allocated timeslot information is updated on a daily basis using a statistical analysis of the uplink/downlink demand. Since communication traffic varies during the day, a faster update rate performs better and is preferred. For medium speed network signaling, the updating is performed periodically ranging from a fraction of an hour to several hours. Medium speed network signaling also uses statistical analysis but over a shorter time period. For fast network signaling, the allocated timeslots are updated on a per call basis or frame basis. Once a timeslot is assigned or released, the appropriate lists are updated. The fast network signaling allocates timeslots on an as needed basis. As a result, it more efficiently uses the system's resources.