APPARATUS AND METHOD FOR INCREASING CELL CAPACITY THROUGH OPTIONAL SIGNAL COMBINING BETWEEN RELAY STATIONS IN A CELLULAR SYSTEM USING WIRED RELAY STATIONS

• US 20080198906A1
• Filed: 12/28/2007
• Published: 08/21/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., University-Industry Foundation Yonsei University
• Original Assignee: Samsung Electronics Co. Ltd., University-Industry Foundation Yonsei University
• Inventors: Hwang, Seong-Taek, Park, Jong-Hyun, Kim, Jong-Hyun, Sung, Won-Jin, Choe, Jin-Woo, KIM, Byung-Jik
• Granted Patent: US 8,134,945 B2
• Time in Patent Office: Days
• US Class Current: 375/211
• CPC Class Codes: H04B 7/026 Co-operative diversity, e.g. using fixed or mobile stations as relays

Abstract

A method, apparatus and system for increasing cell capacity through optional signal combining between Relay Stations (RSs) in a cellular system using wired RSs is disclosed. The method includes receiving, by a Base Station (BS), an average Carrier-to-Interference ratio (C/I) value of transmission signals from Mobile Stations (MSs) located inside each coverage area, being fed back from the RSs or the MSs in its corresponding cell; classifying the MSs into two groups according to the C/I value; performing resource allocation satisfying a minimum data rate from a corresponding RS, for MSs belonging to a group having a C/I value greater than a preset threshold Γ among the classified groups; performing resource allocation by applying an optional signal combining scheme taking into account two RSs having a highest C/I value, for MSs belonging to a group having a C/I value below the threshold among the classified groups; and allocating all unallocated subchannels of each individual RS in an order of an MS having a high C/I value among MSs of a corresponding RS until there is no more unallocated subchannel of each RS.

Claims

1. A method for increasing cell capacity through optional signal combining between Relay Stations (RSs) in a cellular system using wired RSs, the method comprising:

receiving, by a Base Station (BS), an average Carrier-to-Interference ratio (C/I) value of transmission signals from Mobile Stations (MSs) located inside each coverage area, being fed back from the RSs or the MSs in its corresponding cell;

classifying the MSs into two groups according to the C/I value;

performing resource allocation satisfying a minimum data rate from a corresponding RS, for MSs belonging to a group having a C/I value greater than a preset threshold Γ

among the classified groups;

performing resource allocation by applying an optional signal combining scheme taking into account two RSs having a highest C/I value, for MSs belonging to a group having a C/I value below the threshold among the classified groups; and

allocating all unallocated subchannels of each individual RS in an order of an MS having a high C/I value among MSs of a corresponding RS until there is no more unallocated subchannel of each RS.

2. The method of claim 1, wherein classifying the MSs into two groups according to the C/I value comprises:

calculating, by the BS, each average transmission bit receivable from each RS;

finding an RS having a maximum value among the calculated average transmission bits;

comparing an average transmission bit corresponding to the RS having the maximum value with the threshold; and

classifying a group of the corresponding MSs into two groups according to the comparison result.

3. The method of claim 1, wherein performing resource allocation satisfying a minimum data rate for MSs belonging to a group having a C/I value greater than a preset threshold comprises:

selecting, by the BS, a subchannel having a high C/I value for the MSs belonging to a group having the C/I value greater than the threshold among the unallocated subchannels to allocate a subchannel to each MS; and

allocating subchannels until the minimum data rate for the corresponding MS is satisfied.

4. The method of claim 1, wherein performing resource allocation by applying an optional signal combining scheme for MSs belonging to a group having a C/I value below the threshold comprises:

defining a parameter a for a signal combining condition of an RS belonging to a corresponding group;

calculating the C/I value for available subchannel resources between all RSs and MSs belonging to the corresponding group using Equation (9) below;

finding, by the BS, a combination of an RS having a highest C/I value and an MS;

checking a condition of Equation (10) below by finding a combination of an RS having a second highest C/I value and an MS;

applying signal combining of the RS with the highest C/I value and the RS with the second highest C/I value, if the condition of Equation (10) is satisfied;

allocating corresponding subchannel only for the RS with the highest C/I value if the condition of Equation (10) is not satisfied; and

allocating the subchannels until the minimum data rate of the corresponding MS is satisfied;

wherein the above steps are repeatedly performed for all MSs in the corresponding group;

$d_{k,s}=\frac{1}{N_s}<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>c_{k,n,s}<br><br>\left(1-\left[{\mathrm{\rho <br><br>}}_{n,s}\right]\right)$

where N_s denotes a number of subchannels unallocated for each individual RS, an RS is defined as s (=1, 2, . . . ,S), a subchannel is defined as n (=1, 2, . . . ,N), an MS is defined as k (=1, 2, . . . ,K),

c_k,n,s is defined as a number of transmission bits satisfying a target Bit Error Rate (BER) taking into account a signal level for a subchannel #n that an MS #k has received from an RS #s, and

ρ

_n,s is defined as a parameter that has a value of k when an MS #k uses a subchannel #n of an RS #s, and otherwise, has a value of 0;

α

×

c<sub>k′

,n′

,s1</sub><

c<sub>k′

,n′

,1,2</sub>

where Equation (10) is a conditional metric to which optional signal combining is applied, α

is defined as a parameter related to signal combining condition, an MS having a highest C/I value in a corresponding group is defined as k′

, an RS with a highest C/I value and an MS with a second highest C/I value are defined as s₁ and s₂, respectively, and a subchannel corresponding to a maximum value of transmittable bits among available subchannels n for k′ and

s₁ is defined as n′

.

12. The method of claim 4, wherein α

=2.

5. A system for increasing cell capacity through optional signal combining between Relay Stations (RSs) in a cellular system using wired RSs, the system comprising:

a Base Station (BS) for receiving a signal of a Mobile Station (MS) from each of the RSs and the MS, and transmitting data to each of the RSs and the MS depending on the received signal;

a plurality of wired RSs for delivering information on MSs in corresponding coverage to the BS, and performing resource allocation to corresponding MSs; and

a plurality of MSs for receiving resources allocated from each of the RSs and updating the resource allocation information.

6. The system of claim 5, wherein the BS receives an average Carrier-to-Interference ratio (C/I) of a transmission signal of the MS, being fed back from each of the RSs and the MS, and performing resource allocation and scheduling depending thereon in an integrated manner.

7. The system of claim 5, wherein the RS delivers information on MSs in the corresponding coverage to the BS, performs scheduling independently for packets to be transmitted to a corresponding MS, and performs resource allocation from the BS to the corresponding MS.

8. An apparatus for increasing cell capacity through optional signal combining between Relay Stations (RSs) in a cellular system using wired RSs, the apparatus comprising:

a processor in communication with a memory, the memory including code therein which provides instruction to said processor to cause the processor to execute;

determining an average Carrier-to-Interference ratio (C/I) value of transmission signals from Mobile Stations (MSs) located inside each coverage area, being fed back from the RSs or the MSs in its corresponding cell;

classifying the MSs into two groups according to the average C/I value;

performing resource allocation satisfying a minimum data rate from a corresponding RS, for MSs belonging to a group having a C/I value greater than a preset threshold Γ

among the classified groups;

performing resource allocation by applying an optional signal combining scheme taking into account two RSs having a highest C/I value, for MSs belonging to a group having a C/I value below the threshold among the classified groups; and

allocating all unallocated subchannels of each individual RS in an order of an MS having a high C/I value among MSs of a corresponding RS until there is no more unallocated subchannel of each RS.

9. The apparatus of claim 8, wherein classifying the MSs into two groups according to the C/I value comprises:

calculating each average transmission bit receivable from each RS;

finding an RS having a maximum value among the calculated average transmission bits;

comparing an average transmission bit corresponding to the RS having the maximum value with the threshold; and

classifying a group of the corresponding MSs into two groups according to the comparison result.

10. The apparatus of claim 8, wherein performing resource allocation satisfying a minimum data rate for MSs belonging to a group having a C/I value greater than a preset threshold comprises:

selecting a subchannel having a high C/I value for the MSs belonging to a group having the C/I value greater than the threshold among the unallocated subchannels to allocate a subchannel to each MS; and

repeatedly allocating subchannels until the minimum data rate for the corresponding MS is satisfied.

11. The apparatus of claim 8, wherein performing resource allocation by applying an optional signal combining scheme for MSs belonging to a group having a C/I value below the threshold comprises:

defining a parameter α

for a signal combining condition of an RS belonging to a corresponding group;

calculating the C/I value for available subchannel resources between all RSs and MSs belonging to the corresponding group using Equation (9) below;

finding a combination of an RS having a highest C/I value and an MS;

checking a condition of Equation (10) below by finding a combination of an RS having a second highest C/I value and an MS;

applying signal combining of the RS with the highest C/I value and the RS with the second highest C/I value, if the condition of Equation (10) is satisfied;

allocating corresponding subchannel only for the RS with the highest C/I value if the condition of Equation (10) is not satisfied; and

repeatedly allocating the subchannels until the minimum data rate of the corresponding MS is satisfied;

wherein the above steps are repeatedly performed for all MSs in the corresponding group; and

$d_{k,s}=\frac{1}{N_s}<br><br>\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>c_{k,n,s}<br><br>\left(1-\left[{\mathrm{\rho <br><br>}}_{n,s}\right]\right)$

where N_s denotes a number of subchannels unallocated for each individual RS, an RS is defined as s (=1,2, . . . ,S), a subchannel is defined as n (=1,2, . . . ,N), an MS is defined as k (=1,2, . . . ,K),

c_k,n,s is defined as a number of transmission bits satisfying a target Bit Error Rate (BER) taking into account a signal level for a subchannel #n that an MS #k has received from an RS #s, and

ρ

_n,s is defined as a parameter that has a value of k when an MS #k uses a subchannel #n of an RS #s, and otherwise, has a value of 0;

α

×

c<sub>k′

,n′

,s1</sub><

c<sub>k′

,n′

,s1,2</sub>

where Equation (10) is a conditional metric to which optional signal combining is applied, α

is defined as a parameter related to signal combining condition, an MS having a highest C/I value in a corresponding group is defined as k′

, an RS with a highest C/I value and an MS with a second highest C/I value are defined as s₁ and s₂, respectively, and a subchannel corresponding to a maximum value of transmittable bits among available subchannels n for k′ and

s₁ is defined as n′

.

13. The apparatus of claim 11, wherein α

=2.

14. A method for resource allocation in a cellular communication system comprising:

determining an average carrier-to-interference ratio (C/I) value from a plurality of signals received from mobile stations;

allocating each of the plurality of mobile stations to a selected group, wherein allocation is based on said average carrier-to-interference ratio;

allocating resources satisfying a minimum data rate from a group of mobile stations having a C/I value greater than a preset threshold;

allocating resources by applying an optional signal combining scheme considering two remote stations having a highest C/I value of the mobile stations having a C/I value less than the preset threshold; and

allocating remaining unallocated subchannels of each to mobile stations having a high C/I value among mobile stations.

15. The method of claim 14, wherein allocating the mobile stations into groups comprises:

calculating an average transmission bit received from each mobile station;

finding a mobile stations having a maximum value among the calculated average transmission, and

comparing the average transmission bit corresponding to the mobile station having the maximum value with a threshold.

16. The method of claim 14, wherein performing resource allocation satisfying a minimum data for mobile stations belonging to a group having a C/I value greater than a preset threshold comprises:

selecting a subchannel having a high C/I value for the mobile stations belonging to a group having the C/I value greater than the threshold among the unallocated subchannels to allocate a subchannel to each mobile station; and

allocating subchannels until the minimum data rate for the corresponding mobile station is satisfied

17. An apparatus for resource allocation in a cellular communication system comprising:

a processor in communication with a memory, the memory including code which provides instruction to the processor to cause the processor to execute;

determining an average carrier-to-interference ratio (C/I) value from a plurality of signals received from mobile stations;

allocating each of the plurality of mobile stations to a selected group, wherein allocation is based on said average carrier-to-interference ratio;

allocating resources satisfying a minimum data rate from a group of mobile stations having a C/I value greater than a preset threshold;

allocating resources by applying an optional signal combining scheme considering two remote stations having a highest C/I value of the mobile stations having a C/I value less than the preset threshold; and

allocating remaining unallocated subchannels of each to mobile stations having a high C/I value among mobile stations.

18. The apparatus of claim 17, wherein allocating the mobile stations into groups comprises:

calculating an average transmission bit received from each mobile station;

finding a mobile stations having a maximum value among the calculated average transmission, and

comparing the average transmission bit corresponding to the mobile station having the maximum value with a threshold.

19. The apparatus of claim 17, wherein performing resource allocation satisfying a minimum data rate for mobile stations belonging to a group having a C/I value greater than a preset threshold comprises:

selecting a subchannel having a high C/I value for the mobile stations belonging to a group having the C/I value greater than the threshold among the unallocated subchannels to allocate a subchannel to each mobile station; and

allocating subchannels until a minimum data rate for the corresponding mobile station is satisfied.