HK1092965A - System and method for efficiently allocating wireless resources - Google Patents

Description

System and method for efficiently allocating radio resources

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to a method for resource allocation in a wireless communication system.

Background

All known communication standards restrict system resource usage regardless of the type of resource allocated. Resource management is used in communication systems to efficiently allocate system resource limits to all users. The resources may comprise time slots, radio frequency bearers or codes. For example, the Universal Mobile Telecommunications System (UMTS) Time Division Duplex (TDD) standard defines a single bearer that includes pointers and other common channels and time slots. Thus, in this example, bearer selection is equal to cell selection.

In contrast, the Chinese Wireless Telecommunications Standard (CWTS) group time division synchronous code division multiple access (TD-SCDMA) mobile system (TSM) standard defines multiple bearer cells. However, it is necessary that all physical channels belonging to a single application are allocated to the same carrier.

Non-proprietary multi-carrier tdd systems may allocate physical resources to wireless transmit/receive units (WTRUs) in different time slots of different carriers. For example, the fast dynamic channel allocation (F-DCA) algorithm is used to allocate resources (i.e., which time slots on which carriers) to users called coded composite traffic channels (cctrchs). The allocation is based on an optimized allocation quality metric, which may be expressed as a combination of a slot-based allocation metric and a partition metric for the entire cctrch. In the slot-based allocation metric, slot interference, slot transmit power, or slot load is used. In the partition metric for the entire cctrch, partition penalties using multiple time slots within a carrier are assigned, or partition penalties using multiple time slots are assigned. Let TS _ Frag _ Penalty (j) denote the slot-based partition penalty when j slots are used. For example, TS _ Frag _ Penalty (j) is defined as:

equation (1)

Where p is the slot-based partition penalty increment and C is the maximum number of slots supportable by the user.

Let Carrier _ Frag _ penalty (j) denote the vector-based split penalty when j vectors are used. For example, Carrier _ Frag _ penalty (j) is defined as:

carrier _ Frag _ penalty (j) q · (j-1); equation (2)

Wherein q is the vector-based segmentation penalty increment.

While some wtrus may use multiple receivers without implementation limitations on slot selection, most wtrus have a single receiver and limited transition times between Uplink (UL) and Downlink (DL) time slots. Thus, for most wtrus, when time slots from more than one bearer are used, the following two restrictions apply: 1) if a timeslot is used by a wtru in one carrier, the same timeslot cannot be used by a wtru in another carrier; and 2) if a timeslot is used by a wtru in one carrier, only timeslots other than the used timeslot that allow a sufficient guard time for the wtru transceiver to switch frequencies may be used by the same wtru in another carrier. These timeslots that cannot be used because of the particular timeslot usage and the two limitations described above are a forbidden set of timeslots defined as the particular timeslot.

Although channel allocation algorithms have been developed for time division duplex systems, these systems typically comprise a single carrier for use by an operator. In a multi-carrier tdd system, the network is free to allocate wtrus to one or several carriers. Therefore, there is a need for proper allocation of multi-carrier tdd system resources.

Disclosure of Invention

According to the invention, dynamic resource allocation is first implemented by means of the generation of a plurality of slot sequences. Quality indicators based on weighted Interference Signal Code Power (ISCP) and weighted resource units are then generated for each time slot of each slot sequence. The time slots within each slot sequence are arranged in a decreasing quality indicator manner. The sequence of slots is then processed to determine whether it can support the encoding to be transmitted.

Drawings

FIGS. 1A and 1B are flow charts of methods according to the present invention.

Fig. 2 is a multiple carrier communication system in accordance with the present invention.

Detailed Description

The present invention will be described with reference to the drawings, wherein like reference numerals represent like elements throughout.

The preferred embodiments of the present invention are described in terms of a communication system supporting voice and data transmission in a wideband code division multiple access (W-CDMA) communication system according to the third Generation partnership project (3 GPP). It should be noted, however, that the third generation partnership project system is only used as an example, and the present invention may be applied to other cdma systems. Although the embodiments are described in terms of wireless spread spectrum communication types, the invention is also applicable to other slotted, non-slotted, multi-carrier, and single carrier communication system types, and may be applied broadly to all communication type types. Furthermore, the present invention can be applied to wireless and systems using hard-wired connections. Although base-to-mobile transmission has been described, the inventive concept is also useful for peer-to-peer (peer) communications.

As used herein, a wtru item can include, but is not limited to, a user equipment, a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. Examples of these types of wireless environments include, but are not limited to, Wireless Local Area Networks (WLANs) and Public Land Mobile Networks (PLMNs). A base station term used hereafter may include, but is not limited to, a node-B, site controller, access point, or other interconnecting elements in a wireless environment.

In accordance with an exemplary aspect of the present invention using the TSM standard, an improved resource allocation procedure is implemented. The TSM standard requires that all physical channels belonging to a single application are allocated to the same carrier. The resource allocation procedure according to the invention is performed for each bearer. Then, the carrier that yields the best allocation quality metric is selected among all the carriers.

To support a non-patent multi-carrier time division duplex system, several codes are required. Typically, the codes are arranged in ascending order of code spreading factor. This coding arrangement is called a coding set. Those skilled in the art will appreciate that the lower the code spreading factor, the more resource units are required to transmit the code.

Reference toFIGS. 1A and 1B illustrate a dynamic resource allocation process 100 according to the present invention. The process 100 begins at step 10, whereby a plurality of slot sequences are generated. The slot sequence of a group of time slots in a particular order is based on alpha^(k)＝1 β^(k)＝2^k(sequence k +1) and alpha^(k+m+1)＝2^m β^(k+m+1)Applying k + m +1 pairs of α and β values to 1 (sequence k + m +1) to generate; where α is a weighting parameter for the interference signal code power and β is a weighting parameter for the number of resource units that can be used by the coded composite traffic channel in the slot.

By applying k + m +1 pairs of α and β values, a k + m +1 bin sequence is generated as follows:

a) since α is kept equal to 1 and β is increased, the following sequence supports low segmentation:

α⁽¹⁾＝1 β⁽¹⁾＝2⁰(sequence 1) in the presence of a catalyst,

α⁽²⁾＝1 β⁽²⁾＝2¹(sequence 2) in the presence of a catalyst,

α⁽³⁾＝1 β⁽³⁾＝2²(sequence 3) in the presence of a catalyst,

therefore, the first and second electrodes are formed on the substrate,

α^(k)＝1 β^(k)＝2^k(sequence k +1) equation (3)

b) Since β is kept equal to 1 and α is increased, the following sequence supports low interference:

α^(k+1)＝2¹ β^(k+1)1 (sequence k +2),

α^(k+2)＝2² β^(k+2)1 (sequence k +3),

therefore, the first and second electrodes are formed on the substrate,

α^(k+m+1)＝2^m β^(k+m+1)equation (4) 1 (sequence k + m +1)

F_iThe quality indicator is thenIs calculated for each time slot (step 11). Quality indicator F of slot i_iIs generated as:

Fx＝-α·ΔI_i+β·f(C_i) (ii) a Equation (5)

Wherein Δ I_iIs defined as ISCP_i-ISCP_min；ISCP_iEncode the measured interference signal in slot i with power (expressed in dB); ISCP_minThe lowest interferer code power (in dB) between all available timeslots in the same direction (i.e., uplink or downlink); and f (C)_i) Is the number of resource units that can be used by the coded composite traffic channel in slot i.

Parameter f (C)_i) Is calculated as:

f(C_i)＝min(C_i，min(M，RU_{max_slot}) Equation (6)

Wherein C is_iIs the number of available resource units in slot i; m is the number of resource units needed by the coded composite traffic channel; and RU_{max_slot}The maximum number of resource units that can be used by the cctrch in a slot.

Suppose a WTRU supports m-code composite traffic channels (m ≧ 1) simultaneously and the number of codes used by the other code composite traffic channels of the WTRU in the slot is N_USEDSince the WTRU has N in each time slot_WTRUCapacity, so that the number of codes available for the coded composite traffic channel is N_WTRU-N_USED. Therefore, RU_{max_slot}By N in the composite traffic channel which can be encoded_WTRU-N_USEDThe highest number of resource units used for coding.

The time slot of each slot sequence is then indexed by a quality index F_iArranged in descending order (step 12). This provides a sequence of slots that are arranged.

Starting with a first sequence of slots (step 14), a first time slot in the first sequence of slots is selected (step 16). The code with the smallest spreading factor in the code set will also be selected because most resource units will be needed (step 18).

A determination is made as to whether coding for the corresponding spreading factor is available in the selected time slot (step 20). If (i.e., the code is available and the allocation does not violate any function of the wtru, such as the maximum number of timeslots available to be used by the wtru), the process proceeds to step 23.

If the determination in step 20 is negative (i.e., the corresponding code is not available or the allocation violates some functions of the wtru), then action is taken depending on whether it is an uplink timeslot or a downlink timeslot (step 24). If it is an uplink timeslot, the process 100 proceeds to step 26. If it is a downlink timeslot, the process 100 proceeds to step 28 because all codes in the downlink have the same spreading factor and, if the current code cannot be supported in the timeslot, none of the remaining unassigned codes cannot be supported in the timeslot.

In step 26, it is determined whether there are codes with higher spreading factors in the code set. If so, the code from the code set having the next largest spreading factor is selected (step 30) and the process 100 returns to step 20. If the code from the code set having the higher spreading factor is not available, the process 100 proceeds to step 28 where the current slot is eliminated from the slot sequence and the slot sequence is updated.

If any slots remain in the sequence (step 32), the next slot in the sequence of slots is tried and the slot counter initialized at the beginning of each slot sequence analysis is updated (step 34). If any time slots remain in the sequence as determined in step 32, the slot sequence cannot find a slot allocation solution.

It is then determined whether any more slot sequences are available (step 40). If so, the next slot sequence is selected (step 42) and the iscp of each time slot is reset. The process 100 then returns to step 16.

If the time slot is to be used for encoding the composite traffic channel, a determination is made as to whether the total number of time slots that will be needed is within the capabilities of the wtru at step 36. For example, some wtrus can only support a certain number of time slots. An allocation solution using more than this number of time slots will automatically fail. If the total number of timeslots is within the capabilities of the wtru, the process 100 returns to step 20. If the total number of time slots is outside of the wtru capabilities, the cctrch cannot be allocated to more time slots and the slot sequence cannot find a slot allocation solution (step 38). The process 100 proceeds to step 40.

Referring back to step 20, if the determination at step 20 is positive, then if a code with this spreading factor is added, the noise rise in the slot and the code transmit power are estimated (step 23). It is then determined whether the spreading factor can be supported in a timeslot (step 44). This determination is such that if the estimated noise rise and transmit power violate any of the following requirements, the spreading factor cannot be supported for that slot:

1. the noise rise cannot exceed a predetermined threshold. The threshold is a design parameter.

2. The interference signal code power cannot exceed a predetermined threshold. The threshold is a design parameter.

3. In the uplink, the wtru transmit power cannot exceed its maximum allowed transmit power (i.e., the sum of all coded transmit powers used for the ues in the timeslot).

4. In the downlink, the node-B bearer functionality cannot exceed its maximum transmit power (i.e., the sum of all coded transmit powers for all wtrus in the timeslot) as defined by the power class.

5. In the downlink, the difference between the code transmit power of any two codes in the same time slot cannot exceed the maximum dynamic range. The maximum dynamic range value is a design parameter.

If the code (i.e., spreading factor) cannot be supported in the slot determined at step 44, the process 100 proceeds to step 28.

If coding can be supported in the timeslot, the process 100 proceeds to step 46 where the interference of the timeslot is updated. The slot sequence is updated by deleting all slots that cannot be used for other bearers due to the use of that slot.

It is then determined whether there are more codes that must be allocated (i.e., whether there are any codes left in the code set). If so, the process 100 proceeds to step 50 and attempts to assign the next code in the code set to the time slot. Note that for this estimation, the interference signal code power should be updated.

If all codes have been assigned (step 48), then an assignment solution has been found (step 52). The allocation solution is recorded in the slot sequence (i.e., the number of codes for each used slot in each used carrier and its spreading factor). Assume that the coded composite traffic channel uses N carriers, and each carrier N is intra, S_nTime slots are used, ISCP_total(n) represents the total interference of the coded composite traffic channel in carrier n, weighted interference ISCP_weightedIs calculated as total interference plus slot partition penalty and bearer partition penalty:

equation (7)

If there are more slot sequences as determined in step 40, the next slot sequence is selected and the iscp is reset to the iscp of the first slot of the selected slot sequence. The process 100 then returns to step 16. In this manner, other assignment solutions each having its corresponding weighted interference can be found. If slot selection for all slot sequences is performed as determined in step 40, a determination is made as to whether at least one sequence yields an allocation solution (step 54). If not, no solution in power/interference acquisition form is found and the process 100 is completed (step 58). If at least one allocation solution is found, the one with the lowest weighted interference among all allocation solutions is selected as the best allocation solution. The routine 100 is completed (step 58).

Fig. 2 is a general outline of a wireless communication system 200 that includes a core network 202 and a plurality of mobile wtrus 204, 206. The network 202 includes a Radio Network Controller (RNC)210 coupled to a node B212, which is further coupled to a plurality of base stations 214, 216, 218. In operation, the network 202 communicates with the wtrus 204, 206 via the base station 208. Each wtru 204, 206 includes a transceiver section 222 and a signal processing section 220 that allocates communication slots among other factors. In one embodiment, the processes shown in fig. 1A and 1B are performed at the rnc for dedicated channels and at the node B for common channels. For an ad hoc network (e.g., a wireless local area network), the process may be performed at a wtru.

Claims (9)

1. A method of allocating time slots to support a plurality of codes in a set of transmitted codes in a time slotted communication system; the method comprises the following steps:

generating a plurality of slot sequences using at least one selective weight, each slot sequence comprising a plurality of time slots;

calculating a quality indicator for each time slot, the quality indicator based at least in part on the selective weight;

allocating the plurality of time slots in each slot sequence in descending order of quality indicator to provide a permuted slot sequence; and

comparing each of the plurality of codes in the code set with each of the arranged slot sequences to determine whether the arranged slot sequence can support the code set, and if so, identifying the slot sequence as an allocation solution.

2. The method of claim 1 further comprising calculating a weighted interference value for each assignment solution.

3. The method of claim 2 further comprising selecting the allocation solution with lowest weighted interference as a best solution.

4. The method of claim 1 wherein the at least one selective weight value comprises a weighting parameter associated with Interference Signal Code Power (ISCP) α and a weighting parameter associated with a number of Resource Units (RUs) available for a particular time slot.

5. The method of claim 1 wherein the plurality of codes in the code set have a plurality of different spreading factors.

6. The method of claim 5 wherein the comparing step further comprises:

selecting the code within the code group having the smallest spreading factor;

selecting a time slot in the permutation slot sequence;

determining whether there are available codes in the selected time slot to support the minimum spreading factor, and if so, identifying the code as an available code.

7. The method of claim 6, wherein the comparing step further comprises:

estimating a noise rise and a transmit power of the selected timeslot if the available codes are allocated to the selected timeslot; and

determining whether the noise rise and the transmit power in the selected time slot are excessive.

8. The method of claim 7, wherein the comparing step further comprises:

updating the interference in the selected timeslot if the noise rise and the transmit power in the selected timeslot are not excessive.

9. The method of claim 7, wherein the comparing step further comprises:

if the noise rise and the transmit power in the selected time slot are not excessive, the slot sequence is updated by deleting time slots that cannot be used due to the use of the selected time slot.