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

The present invention relates in general to the allocation of resources in wireless arrangements of multiple access communication by hybrid time division / multiple access by code division. More specifically, the invention relates to the allocation of uplink and downlink time slots in said arrangements.

Figure 1 illustrates a wireless communication arrangement. The arrangement has a plurality of base stations 3 (^ - 30 ^. Each base station 30_x communicates with user equipment (DEs) 32_lz 32₃, 32₄ in your area or operating cell. Communications transmitted from the base station 30i to the EU 32j are known as c downlink communications and communications transmitted from the EU 32₃The base station 30j is known as uplink communications.

In addition to communicating about different frequency spectra, the multiple access provisions by division of various spectrum code (CDMA) carry multiple communications on the same spectrum. Multiple signals are distinguished by their respective chip codes (codes). To more effectively use the diverse spectrum, some hybrid time division (TDMA) / CDMA multiple access arrangements as illustrated in Figure 2 use repetitive frames 34 divided into a number of slots

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of time 36j-36_n, like being fifteen. In time division duplex (TDD) arrangements using CDMA, a time slot is used only for downlink or uplink communications in a cell. In these provisions ions, a communication is sent in selected time slots 36₁-36_n using selected codes. According to Elio, a frame 34 is capable of transporting multiple communications distinguished by both time slot 36J-36, as per code. The use of a single code in a single time slot with a dispersion factor of sixteen is known as a resource unit. Based on the bandwidth requirements of a communication, one or multiple resource units can be assigned to a communication.

□ n problem in such arrangements is cross cell interference as illustrated in Figure 3. A second cell base station 30₂ sends a downlink communication 4 0 to the UE 32₂ of a second cell in a certain time slot. In the same time slot, an uplink communication 38 is sent from the UE 32j of a first cell. E communication Uplink 38 may be received by the base station of the first cell 30χ at an unacceptable level of interference. While the base station of the second cell 30₂ is further than the UE of the first cell 32 !, the greatest radiated power

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isotopically effective (EIPR) of the second cell base station 30₂ it may result in unacceptable interference at the base station of the first cell 30 ^

Also shown in Figure 3 is cross interference between UEs 32_lz 32₂. An uplink signal 38 of a UE 32! from the first cell will create unacceptable levels of interference to a downlink communication 40 in the same time slot received by the UE 32₂ of the second cell due to its close proximity.

According to him, there is a need to reduce cross-interference of cells.

A particular cell of. A multiple access communication arrangement by hybrid time division / multiple access by code division has a base station and a plurality of user equipment. Time slots that have unacceptable interference to the uplink are estimated. Time slots are estimated that have an unacceptable interference to the downlink. An availability list is produced. The availability list indicates available uplink and downlink time slots with acceptable interference levels. Time slots with uplinks and downlinks are assigned using the availability list.

Figure 1 is a CDMA arrangement of various wireless spectrum.

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Figure 2 illustrates time slots in repeated frames.

Figure 3 illustrates cross cell interference.

Figure 4 is a list of availability.

Figure 5 e s a flow chart to generate an Availability List using base-to-base station (BS-BS) and user-to-user equipment (EU-EU) interference cells.

Figure 6 is an example of a list of cross-interference cells.

Figure 7 is a table showing a hypothetical time slot allocation for each cell. ·

Figure 8 is an availability list for cell 1 constructed using Figures 6 and 7.

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

Figure 10 is an illustration of a BS-BS cross interference list.

Figure 11 is a flow chart for producing an availability list using EU-EU interference cells only.

Figure 12 is an EU-EU cross interference list.

Figures 13 and 14 are flow charts that they use the

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User time measurement.

The

Figure 15 is an illustration of a specific availability list for user equipment.

Figures 16 and 17 are flow charts for using only interference measurements to determine the availability of time slots.

Figures 18, 19 and 20 are flow charts to determine the availability of time slots using hybrid approaches.

Figure 21 is a flow chart of a time slot allocation approach.

Figure 22 is a flow chart of availability list update.

Figure 23 is the updated table of Figure 7.

Figure 24 is an updated availability list for cell 7 based on Figure 23.

Figure 25 is an embodiment of centralized architecture.

Figure 26 is an embodiment of decentral architecture zada

While the allocation of time slots in the context of a TDD / CDMA arrangement is described below, the same time slot removal procedures

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and availability lists can be applied to a hybrid TDMA / CDMA arrangement where uplink and downlink communications occur in the same time slot in a cell:

Figure 4 illustrates a time slot availability list 76. Along the horizontal axis, each time slot is expressed as SI, S2, ..., SN. Along the vertical axis, each cell, expressed here by the sub-index of its associated base station reference number, is expressed for the uplink and the downlink. Each row indicates the time slot availability for the uplink or downlink of a cell. Unavailable time slots are indicated by an X. The available time slots are left empty. ias.

A procedure for generating the availability list is shown in Figure 5 and explained in conjunction with Figures 6, 7 and 8. Initially, cross interference between each pair of cells is measured. Initially the base station 3 interference cells are determined (^ - 30 ^ to base station 30₁-30₁₁ (BS-BS), step 77. BS-BS interference cells are cells in which the transmissions of base stations 3 (^ - 30 ^ interfere with the reception of other base stations 30₁-30₁₁.

Each cell determines its BS-BS interference cells by estimating the interference of other cells. An approach estimates ·&gt;

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. BS-BS interference cells using pre-released link gains between base stations 3 (^ - 30 ^. If the estimated interference exceeds a threshold, the base assumption cells are considered BS-BS interference cells, □ aso 77. Based on the threshold comparison, interference cells B are determined S-BS and are stored in the cross-interference cell list 84 as illustrated in Figure 6.

The vertical axis of the cross interference cell list 84 has each cell. The horizontal axis has potential cross interference cells. A cell that has BS-BS interference with respect to another cell is marked in the appropriate box by an I, step 79. For example, since the communications in cell 2 produce a cross interference with cell 1, the box of the first row, second column is marked with an I. Since a cell does not interfere with itself, these lockers are marked with an X.

In addition, the cells in which the UEs 32 are determined_x-32_n may interfere with other UEs 32 ^ 32 ,,, step 78. Due to the relatively low EIPR of UEs 32i ~ 32_n EU-EU interference cells are in close geographical proximity, for example adjacent it is. An uplink transmission of UEs 32j may interfere with the reception of the UE from a neighboring cell, as shown in Figure 3. Due to

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Thu very close cells geographically can have UEs 52! -32_n which can interfere with each other, these cells are also classified as interference cells. In Figure 6, EU-EU interference cells that were not BS-BS Interference cells are marked with an I *, step 79.

Using the list of cross interference cells 84, □ for each cell the potential cross interference cells are determined, step 78. For a particular cell on the vertical axis, each cell in the corresponding row narrated with an I ο I * is a cross interference cell. For example, cell 1 potentially receives cross interference from cells 2, 3, 5, 6, 9 and 10. For each cross interference cell, the time slot allocation is determined. For example, using the hypothetical time slot assignment in Table 86 of Figure 7, Cell 2 is assigned downlink time slots 1 and 2 and uplink time slot 9. For each link time slot downlink assigned in a cross interference cell, a corresponding uplink time slot is eliminated, step 80. To illustrate using Figure 6, 7 and 8, for cell 1, cell 2 to which the downlink time slot 1 is assigned, the available uplink time slots of cell 1 are deleted, as shown with an X in the availability list 88 of cell 1 of

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.a Figure 8.

For each uplink time slot assigned to a cross-interference cell, a corresponding downlink time slot is removed, step 82. To illustrate cell 1, the uplink time slot 9 of cell 2 removes that time slot of l The possible downlink time slots in cell 1, as shown in the availability list 88 in cell 1. After removing the appropriate time slots due to cross interference cells, an availability list 76 is produced for each cell, step 90. As a result, the uplink and downlink time slots used in cross interference cells are they become unavailable, reducing cross cell interference.

To lighten the allocation conditions, only BS-BS interference cells or only EU-EU interference cells are considered. These approaches can achieve the release of more resources for each cell. However, less stringent criteria may result in unacceptable levels of interference for some users.

Figure 9 is a flow chart for producing an availability list using only BS-BS interference cells. The cells BS-BS interference are identified, step 122. A cross-interference list BS-BS 132 is produced,

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as shown in Figure 10. If a cell uses a time slot for the uplink, that slot is removed for use by BS-BS interference cells for the downlink, step 126. On the contrary, if a cell uses a time slot for the downlink, that slot is removed for use by BS-BS interference cells for the uplink, step 128. A list of available time slots is produced for each cell, step 130. While this approach uses the resources of the provision more aggressively, some users may suffer unacceptable downlink interferences.

Figure 11 is a flow chart for producing an availability list using only EU-EU interference cells. The EU-EU interference cells are identified, step 134. An interf list is produced EU-UE cross-interference 142, as in Figure 12. If a cell uses a time slot for the uplink, that slot is removed for use by EU-EU interference cells for the downlink, step 136. On the contrary, if a cell uses a time slot for the uplink, that slot is removed for use by EU-EU interference cells for the uplink, step 138. A list of available time slots is produced for each cell, step 140. This approach can result in levels of link interference

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ascending unacceptable for some users.

Another approach to determine unavailable time slots uses interference measurements of slots of time, such as by means of serial interference code (ISCP) power. Interference measurements can be taken at base stations 30! -30u, UEs 32i ~ 32_n or both.

The figure 13 is a flow chart that uses measurements ie base station and UE interference to determine available time slots for each UE 32 ^ 32 ,,. For a cell in □ articulate, the level of interference in each time slot is measured at the base station 30_lz step 144. Each of the cells in the UEs 32_lf 32₃-32₄ also measures the interference levels in each time slot, step 146. The measurements of time slot interference by the base stations are used to determine the availability of uplink time slots. The availability of downlink time slot is determined on a UE by UE basis (specific basis for UE).

For the uplink, if the measured interference of the base station exceeds a threshold in a time slot, that time slot is eliminated for the uplink, step 148. For the downlink, each UE 32_lr 32₃, 32₄eliminates downlink time slots for use, if the interference measure of that UE exceeds a threshold,

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use 150. An availability list 154 is produced showing the available uplink time slots and the available downlink time slots for each UE as illustrated in Figure 15,? or 152.

While two cells are adjacent, the location of the

JEs 32! ~ 32_n In cells it can be distant. To illustrate using Figure 1, cell 1 and cell 2 are adjacent. However, a UE 32₄ is distant from cell 2. According to elio, if the UE 32₂ in cell 2 use a slot for the uplink, most likely it will not interfere with the downlink reception of the UE 32₄. However, the upstream transmissions of the UE 32₂they would probably interfere with the transmission of the UE 32! from downlink As a result, a more aggressive resource allocation is available using a specific availability list for UE 154. A disadvantage is the greater signaling required. Due to the mobility of the UE and other cell reallocations, interference measurements must be updated and signaled to the base station 30i-30n frequently.

Figure 14 is a flowchart using base station and UE interference measurements to determine available time slots not specific to UE. The base station 3Û! measure the interference in each slot of

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time, step 144, and so does each UE 32i step 146. For the uplink, if the given interference from the base station exceeds a threshold in a time slot, that time slot is eliminated, step 148. For the snlace descending, if any measured interference from the UEs je that cell in a time slot exceeds the threshold, that time slot is removed na for the downlink, step 156. Using the deleted time slots, an availability list 88 is produced for each cell, for example as in Figure 8. Because the UE measurements are effectively combined, the missing EU interference measurements are not critical for the allocation of resource unit

Figures 16 and 17 are flow charts using only EU interference measurements to determine available time slots. In one cell, each UE measures the interference in each time slot, step 160. For the uplink, if any measure of UE interference exceeds the threshold, that time slot is eliminated for the uplink, step 160. Alternatively, to reduce the amount of uplink time slots removed, only the time slots in which most UEs have unacceptable interference are removed from the uplink, step 160. If only a few UEs have an int unacceptable interference, it is assumed that these UEs are

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they are in the margin of the cell and are not representative &lt;pe the global conditions of the cell.

Using a specific allocation approach for UE as in Figure 16, each UE 32_lz 32₃, 32₄, has its own set of downlink time slots available, as for example shown in Figure 15. One downlink time slot is eliminated for each UE 32i, 32₃, 32₄, if the interference measurement of that UE in the time slot exceeds a threshold, step 164. Lina availability list 150 specific to UE occurs, step 166.

A non-specific approach to THU is shown in Figure 17. If the interference measurement of any UE or of the EU Heading exceeds a threshold in the time slot, that time slot is removed for the downlink, step 168. An availability list 88 is produced, as is the case mues Figure 8, for the entire cell.

Figures 18, 19 and 20 are time slot availability determination approaches, using hybrid BS-BS interference measurement, EU-EU interference and interference approaches. Figures 18 and 19 are measurements of BS-BS interference cells and UE interference. Interference cells BS-BS are determined, step 17 2. Each UE 32_1:, 32₃, 32₄, measure the interference in each time slot, step 174. For the uplink, the time slots are eliminated, if a BS-BS interference cell uses it for the

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z downlink, step 176.

Downlink availability is determined on a non EU basis by EU or collective basis. Using one EU base per EU as in Figure 18, each EU 32_lz 32₃, 32₄ Compare each time slot interference issue with a threshold. When a time slot measurement exceeds the threshold, the time / length is eliminated for that EU 32i, 32₃, 32₄, on the downlink, step 178. A specific availability list is produced for UE 150, as in Figure L5, step 180.

Using a collective base as shown in Figure 19, if any measurement of time slot interference UE exceeds a threshold, that time slot is removed for the downlink to the cell, step 182. An availability list is produced 88 , as shown in Figure 8, step 184.

Figure 20 uses EU-EU interference cells and base station interference measurements. A base station of cell 30₃ measure the interference levels in each time slot, step 186. EU-EU interference cells are identified, step 188. For the uplink, the uplink time slots are eliminated, if the interference for that time slot exceeds a threshold, step 190. For the downlink, a downlink time slot is eliminated you, if a cell of

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EU-EU interference uses it for the uplink, step Ï92. Based on the deleted time slots, an availability list 88 is produced, as in Figure 8.

For sectorized cells, the cross interference list and availability lists 84 are constructed for a given sector within the cells. Cross interference between all sectors of the cell is determined. While the following analysis deals with non-ectorized cells, the same approach is applied to ectorized cells where the assignment is made on a sector basis rather than per cell.

Using availability list 76, each case station SOj-SOn receives the allocation of time slots to support its communications using the procedure of Figure 21. Initially an order is made for a slot ie additional allocated time or more, step 92. Referring to the availability list 76 of that station oase, available time slots are assigned. To illustrate using the availability list 88 of Figure 8, the base station 30_x It requires both an additional assigned downlink and an uplink time slot. The available uplink time slots are slots 4 and 7-16 and the available downlink time slots are slots 1-3, 5, 6, 8, 10-13 and 16. A time slot will be assigned of link

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ί Scenario and a downlink time slot between the corresponding available downlink and uplink time slots. If a specific 150 availability list is used for UE, the downlink assignment is based on UE 32γ —32_n which requires the downlink resource unit (s).

Since base stations 30 ^ 30 ,, need to allocate ί dynamically free time slots due to the variable demand of uplink / downlink, the information in the availability list 7 6 requires updating. In the case of approaches that use interference measurements, updates are carried out by updating the measurements and lists.

For BS-BS and EU-EU approaches, this procedure is ours in Figure 22. Initially, cross interference cells are identified by each assigned or released time slot, step 96. For each assigned downlink time slot. , the corresponding time slots in the cross interference cells are removed for the uplink, step 98. On the contrary, if the uplink time slot is assigned, the corresponding time slots in the cross interference cells for the downlink are eliminated, step 100. To illustrate with Figures 23 and 24, the base station 30₆ associated with cell 6 allo to the groove

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Time 7 for the downlink D *, and the time slot 8 for the uplink, U *, as indicated in Table 106 of Figure 23. The cross interference cells are cells 1, 2, 5 and 7. As shown in the availability list 107 for 'cell 7 of Figure 24, the time slot 7 is removed for the uplink and the time slot 8 is removed for the downlink, both marked as X * .

When a downlink time slot has been released, the corresponding time slots in the cross interference cells are released for the uplink, unless they are not available for other reasons, for example used as a downlink time slot. in another cross interference cell, step 102. &gt; or, for example, if time slot 6 in cell 6 is released as indicated in table 106 as D **, the uplink time slot 6 in cell 1 is not It puts Iisposition. Cell 9 is a cross interference cell to cell 1, which also uses the downlink time slot 6. On the contrary, for cell 7, the Release of the downlink time slot 6 Releases the cell for uplink communications as shown in the availability list 108 for cell 7, zone R. If one has been released sscendent link time slot, the corresponding time slots in the

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Cross-interference calls are released for the link (Ascending unless not available for other reasons, maso 104.

An approach to using the uplink / downlink time slot assignment is shown in Figure 25 using a centralized architecture. The radio network toner (RNC) 110 has a resource allocation device 11 for allocating or releasing a time slot based on user demand. If you are assigning, the d Resource allocation device 116 in RNC 110 allocates an appropriate time slot using the list and availability 76, stored in its memory 117, in accordance with the procedure of Figure 21. The selected time slots and channel codes are communicated. to base station 30! -30_N and to the EU 30₂-30_N through time slot assignment node B and release device 112₁-112_n. If you are releasing a time slot, the resource allocation device RNC 116 releases the time slot and updates the availability list 76. According to it, the update of the availability list 76 is centralized as it takes place in the RNC 110.

Another approach to the uplink / downlink time slot assignment is shown in Figure 36 using a decentralized architecture. Each node B

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]22!-122_N has its own contr time slot odor] 20! -120_n. When an allocation and release device ce time slot 112₁-112_n requests time slots for ina communication, the time slot controller of node B 120₁-120_n select an appropriate time slot from :: or availability list 76, as stored in its memory 121j. The stored availability list 76, to reduce its capacity, can only contain the time slots for the cell or cells of that node B. On the contrary, the stored availability list 76 may contain the availability of all the RNC cells. The decentralized approach allows for faster updates.

The selected time slot is assigned to the communication by means of the device for assigning and releasing time slots 112₁-112_n. To update lists 76, said node B 122₁-122 „ updates its list 76. The assigned and Released time slots are also sent to the RNC 110. The RNC 110 directs the appropriate time slot update information to the other cells. The information on time slots contains an updated availability list 76 or merely changes in list 76. If only changes are sent, the controller in each cell 1202-120 ,, updates its own availability list 76 with that information. The type of time slot information sent is based on the requirements of

-Z

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processing and signaling of the provision.

The allocation of uplink / downlink time slots is adaptable to arrangements that support different signaling rates. For provisions that only support slow network signaling, the assigned time slot information is updated daily using a statistical analysis of the uplink demand dente / downlink. Because communication traffic varies during the day, a faster refresh rate operates better and is preferred. In the case of medium speed network signaling, the update is carried out periodically oscillating between a fraction of an hour and several hours. Medium speed network signaling also uses statistical analysis but in less time. In the case of fast network signaling, the assigned time slots are updated by call or by frame. Once a time slot is assigned or released, the appropriate lists are updated. Fast network signaling allocates time slots as needed. As a result, it uses the resources of the provision more effectively.