Resource Allocation for Multiple Femtocells

The simulation results of the system model mentioned in chapter 4 are displayed in this section. 5 fBSs are randomly located in a ”femtocell region” with radius of 30 meters.

In Fig. 5.8, Fig. 5.9, and Fig. 5.10, the fMS number is fixed to be 1 in any one fBS.

The line denoted as ”macro” in Fig. 5.8 is the bandwidth efficiency of the macrocell without femtocell deployment. And lines marked as ”macro wfemto (scheme A)” and

”macro wfemto (scheme A)” represent bandwidth efficiency of macrocell overlaid by multiple femtocells using resource allocation methods in 4.2.1 and 4.2.2 respectively.

We can read from the figure that scheme B results in much interference to the macrocell network. On the other side, scheme B outperforms scheme A in femtocells’ position, shown in Fig. 5.9. Fig. 5.10 is the total bandwidth efficiency of the overall network. In addition, Fig. 5.11, 5.12, and 5.13 are bandwidth efficiency of macrocell’s, femtocells’ and overall network’s. The fMS number discussed in Fig. 5.11, 5.12, and 5.13 is between 1 and 3. Comparing Fig. 5.9 and Fig. 5.12, we may acquire the fact that femtocell bandwidth efficiency will increase if multiple fMSs are considered due to user diversity.

−5 0 5 10 15 20 25 7.5

8 8.5 9

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

macro

macro wfemto (scheme A) macro wfemto (scheme B)

Figure 5.8: Macrocell bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with 1 fMS.

−5 0 5 10 15 20 25

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

femto (scheme A) femto (scheme B)

Figure 5.9: Femtocell bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with 1 fMS.

−5 0 5 10 15 20 25 15

20 25 30 35 40 45

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

total (scheme A) total (scheme B)

Figure 5.10: Total bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with 1 fMS.

−5 0 5 10 15 20 25 7.5

8 8.5 9

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

macro without femto macro wfemto (scheme A) macro wfemto (scheme Bl)

Figure 5.11: Macrocell bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with random amount of fMSs.

−5 0 5 10 15 20 25 5

10 15 20 25 30 35 40

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

femto (scheme A) femto (scheme B)

Figure 5.12: Femtocell bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with random amount of fMSs.

−5 0 5 10 15 20 25 15

20 25 30 35 40 45

SINR constraint of macrocell user

Bandwidth Efficiency (bit/s/Hz)

total (scheme A) total (scheme B)

Figure 5.13: Total bandwidth efficiency versus mMS’ SINR constraints with different resource allocation methods in the scenario of multiple fBSs with random amount of fMSs.

Chapter 6 Conclusion

The purpose of this thesis is to give practicable solutions to downlink resource allo-cation problems in femtocell-macrocell coexisting OFDMA network while meeting SINR requirements for both femtocell and macrocell users.

We first present subcarrier assignment algorithms among multiple femtocell users. In the case of higher mMS’ SINR constraints, there would be tight femtocell power upper bound on each subcarrier, and the algorithm in 3.1.2 gives better performance. On the other side, the algorithm proposed in 3.1.1 is more suitable for the condition of relative lower mMS’ SINR constraints. We then proffer power allocation algorithms which can be applied to multiple users or single femtocell user. The results show that ”iterative water-filling algorithm” contributes better performance but it is more complicated. If we take femtocell users’ SINR constraints into account, total bandwidth efficiency of femtocell network will be reduced. In the case of multiple fBSs, scheme B addressed in 4.2.2 provides better performance in femtocells’ standpoints but cause severe interference to mMSs.

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