Wireless communication method and apparatus for assigning cell and resource blocks

• US 8,095,139 B2
• Filed: 09/11/2007
• Issued: 01/10/2012
• Est. Priority Date: 09/14/2006
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Marinier, Paul
• Primary Examiner(s): Afshar, Kamran
• Assistant Examiner(s): Zewari, Sayed T
• Application Number:
  US11/853,091
• Publication Number:
  US 20080068981A1
• Time in Patent Office: 1,582 Days
• Field of Search: 455/446
• US Class Current: 455/446
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04W 36/20 for optimising the interference level
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

A method and apparatus for assigning cell and resource blocks to a wireless transmit/receive units (WTRU) in a wireless communication system including a resource management unit and a plurality of cells having resource blocks are disclosed. The WTRU is currently associated with a particular one of the cells. Path losses between the WTRU and cells neighboring the particular cell are determined. The average level of inter-cell interference on each resource block at each cell neighboring the particular cell is then determined. A signal-to-interference ratio (SIR) is then determined to support a guaranteed bit rate of the WTRU on an uplink.

Claims

1. A method of assigning a cell and resource blocks to a wireless transmit/receive unit, WTRU, the method comprising:

determining a current cell and a resource block that a WTRU is allocated to;

determining path losses between the WTRU and cells neighboring the current cell;

determining an expected change of inter-cell interference generated based on the WTRU being allocated to each neighboring cell and resource block among all possible candidate cell and resource block combinations, subject to the constraint of a predetermined power of the WTRU and a predetermined level of cell interference;

assigning the WTRU to the candidate cell with the resource block having the lowest expected change of intercell interference required to support a predetermined bit rate of the WTRU on an uplink based on the predetermined power of the WTRU and the predetermined level of cell interference;

estimating the required transmission power, TxPower, of the WTRU based on a required signal-to-interference ratio, SIR, the average level of inter-cell interference on the candidate cell and resource block, I_cand, and the path loss to the candidate cell, L_cand, based on the following formula;

TxPower(dBm)=SIR(dB)+L_cand(dB)+I_cand(dBm),

calculating the resulting level of inter-cell interference, Δ

I_i, generated by the WTRU at each neighboring cell, i, and resource block, j, based on the required transmission power and the path loss between the WTRU and the neighboring cell L_i;

Δ

I_i(dBm)=TxPower(dBm)−

L_i(dB),

estimating the relative increase of inter-cell interference, I_ij/I_ij, on each resource block at each cell based on the pre-existing level of inter-cell interference;

I_ij'"'"'/I_ij(dB)=10 log 10[1+Δ

I_i(mW)/I_ij(mW)].

2. The method of claim 1 further comprising:

measuring the received signal strength of a certain beacon signal transmitted by each of the cells at a known transmission power on a known resource block; and

reporting the received signal strength to a resource management unit.

3. The method of claim 2 wherein an average received signal strength is reported to the resource management unit.

4. The method of claim 1 further comprising:

transmitting a probe signal on a certain reserved resource block at a specified transmission power.

5. The method of claim 4 further comprising:

receiving measurements of the received signal strength of the probe signal.

6. The method of claim 1 further comprising:

measuring the average level of inter-cell interference by candidate cells on each resource block.

7. The method of claim 6 wherein the measurement of the average level of inter-cell interference is performed upon request.

8. The method of claim 6 wherein the measurement of the average level of inter-cell interference is performed on a periodic basis.

9. The method of claim 1 further comprising:

determining, based on a signal-to-interference ratio, SIR, whether a maximum transmission power of the WTRU would be exceeded, or if a maximum level of inter-cell interference on a candidate cell/resource block would be exceeded.

10. The method of claim 1 further comprising:

determining an expected increase of inter-cell interference on resource blocks at neighboring cells for each candidate cell assignment.

11. The method of claim 1 wherein after the set of estimated relative increases of inter-cell interference has been estimated for each candidate cell and resource block assignment, an elected assignment is determined based on the smallest sum of estimated relative increases of inter-cell interference.

12. The method of claim 1 wherein after the set of estimated relative increases of inter-cell interference has been estimated for each candidate cell and resource block assignment, an elected assignment is determined based on the smallest maximum among the estimated relative increases of inter-cell interference.

13. The method of claim 1 wherein after the set of estimated relative increases of inter-cell interference has been estimated for each candidate cell and resource block assignment, an elected assignment is determined based on the smallest weighted sum of estimated relative increases of inter-cell interference.

14. A resource management unit for managing a plurality of cells and resource blocks, the resource management unit comprising:

a receiver configured to receive information used to i) determine a current cell and a resource block that a wireless transmit/receive unit, WTRU, is allocated to, and ii) determine path losses between the WTRU and cells neighboring the current cell and

a processor configured to determine an expected change of inter-cell interference generated based on a wireless transmit/receive unit, WTRU, being allocated to each neighboring cell and resource block among all possible candidate cell and resource block combinations, subject to the constraint of a predetermined power of the WTRU and a predetermined level of cell interference, and assign the WTRU to the candidate cell with the resource block having the lowest expected change of intercell interference required to support a predetermined bit rate of the WTRU on an uplink based on the predetermined power of the WTRU and the predetermined level of cell interference;

wherein the processor estimates the required transmission power, TxPower, of the WTRU based on a required signal-to-interference ratio, SIR, the average level of inter-cell interference on the candidate cell and resource block, I_cand, and the path loss to the candidate cell, L_cand, based on the following formula;

TxPower(dBm)=SIR(dB)+L_cand(dB)+I_cand(dBm),

wherein the processor calculates the resulting level of inter-cell interference, Δ

I_i, generated by the WTRU at each neighboring cell, i, and resource block, j, based on the required transmission power and the path loss between the WTRU and the neighboring cell, L_i;

Δ

I_i(dBm)=TxPower(dBm)−

L_i(dB),

wherein the processor estimates the relative increase of inter-cell interference, I_ij'"'"'/I_ij, on each resource block at each cell based on the pre-existing level of inter-cell interference;

I_ij'"'"'/I_ij(dB)=10 log 10[1+Δ

I_ij(mW)/I_ij(mW)].

15. The resource management unit of claim 14 wherein the receiver is further configured to receive a signal from the WTRU indicating an average received signal strength measurement.

16. The resource management unit of claim 14 wherein the receiver is further configured to receive signals from the neighboring cells indicating received signal strength measurements.

17. The resource management unit of claim 16 wherein the neighboring cells report an average received signal strength.

18. The resource management unit of claim 14 wherein the average level of inter-cell interference by the candidate cells on each resource block is measured.

19. The resource management unit of claim 18 wherein the measurement of the average level of inter-cell interference is performed upon request.

20. The resource management unit of claim 18 wherein the measurement of the average level of inter-cell interference is performed on a periodic basis.

21. The resource management unit of claim 14 wherein the processor determines whether the maximum transmission power of the WTRU would be exceeded, or if the maximum level of inter-cell interference on a candidate cell/resource block would be exceeded, based on a signal-to-interference ratio, SIR, estimate.

22. The resource management unit of claim 14 wherein the processor determines an expected increase of inter-cell interference on resource blocks at neighboring cells for each candidate cell assignment.

23. The resource management unit of claim 14 wherein after the resource management unit has estimated the set of estimated relative increases of inter-cell interference for each candidate assignment, the assignment being determined based on the smallest sum of estimated relative increases of inter-cell interference.

24. The resource management unit of claim 14 wherein after the resource management unit has estimated the set of estimated relative increases of inter-cell interference for each candidate cell and resource block assignment, an elected assignment is determined based on the smallest maximum among the estimated relative increases of inter-cell interference.

25. The resource management unit of claim 14 wherein after the resource management unit has estimated the set of estimated relative increases of inter-cell interference for each candidate cell and resource block assignment, an elected assignment is determined based on the smallest weighted sum of estimated relative increases of inter-cell interference.

26. A wireless transmit/receive unit, WTRU, comprising:

a receiver configured to receive information used to i) determine a current cell and a resource block that a wireless transmit/receive unit, WTRU, is allocated to, and ii) determine path losses between the WTRU and cells neighboring the current cell; and

a processor configured to determine an expected change of inter-cell interference generated based on the WTRU being allocated to each neighboring cell and resource block among all possible candidate cell and resource block combinations, subject to the constraint of a predetermined power of the WTRU and a predetermined level of cell interference, and assign the WTRU to the candidate cell with the resource block having the lowest expected change of intercell interference required to support a predetermined bit rate of the WTRU on an uplink based on the predetermined power of the WTRU and the predetermined level of cell interference;

wherein the processor estimates the required transmission power, TxPower, of the WTRU based on a required signal-to-interference ratio, SIR, the average level of inter-cell interference on the candidate cell and resource block, I_cand, and the path loss to the candidate cell, L_cand, based on the following formula;

TxPower(dBm)=SIR(dB)+L_cand(dB)+I_cand(dBm),

wherein the processor calculates the resulting level of inter-cell interference, Δ

I_i, generated by the WTRU at each neighboring cell, i, and resource block, j, based on the required transmission power and the path loss between the WTRU and the neighboring cell, L_i;

Δ

I_i(dBm)=TxPower(dBm)−

L_i(dB),

wherein the processor estimates the relative increase of inter-cell interference, I_ij'"'"'/I_ij, on each resource block at each cell based on the pre-existing level of inter-cell interference;

I_ij'"'"'/I_ij(dB)=10 log 10[1+Δ

I_i(mW)/I_ij(mW)].

27. The WTRU of claim 26 further comprising:

a transmitter configured to transmit a signal indicating an average received signal strength.

28. The WTRU of claim 26 further comprising:

a transmitter configured to request interference levels of specified resource blocks at specified neighboring cells from a resource management unit.

29. The WTRU of claim 26 wherein the received information further includes a maximum bit rate or a maximum transmission power that the WTRU should use to limit inter-cell interference that the WTRU generates.