Method of joint optimization of channel selection and frame scheduling for coexistence of LTE and WLAN in unlicensed band

1. A method of joint optimization of channel selection and frame scheduling for coexistence of LTE and WLAN in an unlicensed band, the method being performed by a baseband unit (BBU) pool, comprising:

selecting a component carrier (CC) having a highest idle probability by considering an idle probability of the CC for the unlicensed band;

determining the number N I of idle subframes in the selected CC by considering a residence time in a WLAN system queue; and

allocating a resource block (RB) to an LTE user terminal in a cell based on the number of selected CCs and the number of idle subframes.

2. The method of claim 1 , wherein:

the cell is a macro cell served by an LTE base station (eNB), the cell includes a plurality of small cells served by an LTE-U base station (remote radio head (RRH)), and a WLAN service is performed by at least one WLAN AP in at least some of the plurality of small cells.

3. The method of claim 2 , wherein:

in selecting the CC having the highest idle probability,

N CC k CCs having the idle probability in a higher order are selected with respect to k respective plural small cells and N CC k CCs are determined according to carrier aggregation (CA) currently provided by a k-th small cell, and

in selecting N CCk CCs having the idle probability in the higher order, N CCk CCs are in an order in which the number of WLAN APs using the CC is smaller.

4. The method of claim 1 , wherein:

the determining of the number N I of idle subframes in the selected CC includes,

calculating S k,c B which is the residence time in the WLAN system queue when no idle subframe is allocated, and

determining the number N k,c I of idle subframes using CC c which is a c-th CC in a k-th small cell based on (N k,c I /Ns)μ k,c <λ k,c , Ns, μ k,c , and λ k,c representing the number of subframes per frame, and a service processing speed and a packing arrival speed of a WLAN system using the CC c in the k-th small cell, respectively.

5. The method of claim 4 , wherein:

the determining of the number N I of idle subframes in the selected CC further includes,

determining not to use the CC c when the number N k,c I of idle subframes in which the WLAN system queue may be stabilized does not exist, and

determining the minimum number of idle subframes in which the rate of the increase in residence time in the WLAN system queue does not exceed σ which is a predetermined level while increasing the number N k,c I of idle subframes by one for another CC c.

6. The method of claim 2 , wherein:

in the allocating of the resource block (RB) to the LTE user terminal in the cell based on the number of selected CCs and the number of idle subframes,

the RB is preferentially allocated to a first LTE user which may not be allocated with the RB for a predetermined time or more,

the RB capable of guaranteeing maximum throughput is allocated to the first LTE user, and

the remaining RBs are allocated to a second LTE user which is an LTE user having a good channel state in order to maximize throughput.

7. A method of joint optimization of channel selection and frame scheduling for coexistence of LTE and WLAN in an unlicensed band, the method being performed by an LTE terminal, comprising:

allocating a resource block (RB) based on the number of component carriers (CCs) selected by a baseband unit (BBU) pool and the number N I of idle subframes, the selected CC representing a CC having a highest idle probability considering an idle probability of the CC with respect to the unlicensed band and the number N I of selected idle subframes being determined by considering a residence time in a WLAN system queue in the selected CC, and

receiving data from an LTE-U base station (remote radio head (RRH)) through the selected RB.