Apparatus and method for determining data transmission rate in multi-hop relay system

1. A Base Station (BS) apparatus in a multi-hop relay system, comprising:

a receiver for receiving channel condition information and queue length information of a queue for buffering data to be relayed to a Mobile Station (MS) from a Relay Station (RS);

a target queue length determiner for determining a target queue length for the MS using the channel condition information; and

a data rate determiner for determining a data transmission rate between the BS and the RS for data of the MS using the target queue length, the channel condition information and the queue length information.

2. The BS apparatus of claim 1 , further comprising a scheduler for performing a resource scheduling operation for communication between the BS and the RS using the data transmission rate received from the data rate determiner.

3. The BS apparatus of claim 1 , wherein the channel condition information includes a Signal-to-Interference plus Noise Ratio (SINR).

4. The BS apparatus of claim 1 , wherein the target queue length determiner calculates a channel capacity using the channel condition information and calculates the target queue length using a long-term average of the channel capacity.

5. The BS apparatus of claim 1 , wherein the data rate determiner determines the data transmission rate such that a queue length of the RS for the MS is converged on the target queue length.

6. The BS apparatus of claim 1 , wherein the data rate determiner reduces the data transmission rate when a queue length is greater than previous data transmission rate value or the target queue length, and increases the data transmission rate when the queue length is less than the previous data transmission rate or the target queue length.

7. The BS apparatus of claim 1 , wherein the data rate determiner determines the data transmission rate using the following equation:

r i [t+Δt]=r i [t]−A ( q i [t]−q i [t−Δt ])− BΔt ( q i [t]−q Ti −ΔC i )

where r i [t] is a BS-RS data transmission rate (bit/sec) for an i th MS at a time point t, q i [t] is an RS queue length (bit) for the i th MS at the time point t, q Ti is the target queue length (bit) for the i th MS, Δt is an update period (sec) of the data transmission rate, ΔC i is a channel capacity change (bit) versus the previous frame between the RS and the i th MS, and A and B are parameters for adjusting a change of the data transmission rate (A: 1 sec −1 ; B: 1 sec- 2 ).

8. A Relay Station (RS) apparatus in a multi-hop relay system, comprising:

a channel condition information collector for collecting channel condition information fed back from Mobile Stations (MSs);

a queue length information collector for collecting queue length information of queues for buffering data to be relayed to the MSs; and

a feedback unit for feeding at least one of (1) the channel condition information from the channel condition information collector and the queue length information from the queue length information collector and (2) channel condition information and queue length information for MSs of a subordinate RS from the subordinate RS, back to a Base Station (BS).

9. A communication method for a Base Station (BS) in a multi-hop relay system, comprising the steps of:

receiving channel condition information and queue length information of a queue for buffering data to be relayed to a Mobile Station (MS) from a Relay Station (RS);

determining a target queue length for the MS using the channel condition information; and

determining a data transmission rate between the BS and the RS for data of the MS using the target queue length, the channel condition information, and the queue length information.

10. The communication method of claim 9 , further comprising performing a resource scheduling operation for communication between the BS and the RS using the data transmission rate.

11. The communication method of claim 9 , wherein the channel condition information includes a Signal-to-Interference plus Noise Ratio (SINR).

12. The communication method of claim 9 , wherein determining the target queue length further comprises:

calculating a channel capacity using the channel condition information; and

calculating the target queue length using a long-term average of the channel capacity.

13. The communication method of claim 9 , wherein the data transmission rate is determined such that a queue length of the RS for the MS is converged on the target queue length.

14. The communication method of claim 9 , wherein the determining of the data transmission rate further comprises:

reducing the data transmission rate when a queue length is greater than previous data transmission rate value thereof or the target queue length; and

increasing the data transmission rate when the queue length is less than the previous value thereof or the target queue length.

15. The communication method of claim 9 , wherein the data transmission rate is determined using the following equation:

r i [t+Δt]=r i [t]−A ( q i [t]−q i [t−Δt ])− BΔt ( q i [t]−q Ti −ΔC i )

where r i [t] is a BS-RS data transmission rate (bit/sec) for an i th MS at a time point t, q i [t] is a RS queue length (bit) for the i th MS at the time point t, q Ti is the target queue length (bit) for the i th MS, Δt is an update period (sec) of the data transmission rate, ΔC i is a channel capacity change (bit) versus a previous frame between the RS and the i th MS, and A and B are parameters for adjusting a change of the data transmission rate (A: 1 sec −1 ; B: 1 sec- 2 ).

16. A communication method for a Relay Station (RS) in a multi-hop relay system, comprising the steps of:

collecting channel condition information fed back from Mobile Stations (MSs);

collecting queue length information of queues for buffering data to be relayed to the MSs; and

reporting the collected channel condition information and the collected queue length information to a Base Station (BS);

receiving channel condition information and queue length information for MSs of a subordinate RS from the subordinate RS; and

relaying the received channel condition information and the received queue length information for the MSs of the subordinate RS to the BS.