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10 Figure 5.11: Allocation of New Resources The last point is visualized in Fig. 5.12, where a cellular system and a single subcar- rier are considered. The receive power is plotted for all base stations from one mobile terminal localized at the green cross. The dark blue color represents the noise power while the dark red color represents high signal power. Obviously, for the MISO system lots of more resources are still usable for every base station compared to the SISO system. SISO MISO Figure 5.12: Interference at BS Expectedly, the zeroforcing beams achieve the highest performance, yielding an increase of 10 users compared to fixed beams. Beside the advantages of the MISO system pointed out before, the ideal channel knowledge is exploited so that intra- sector interference is fully avoided. Additionally, the steering of transmit power towards the users is enhanced. 186 5 System Level Aspects for Multiple Cell Scenarios Reallocation Due to the fluctuation of the interference power level within the network, the CQI values are only valid for a short duration. Therefore, the measurement of the useful and interference power is updated after each frame. In doing so, each user measures the power on the resources occupied by the base station and signals it back. In other words, a subset of the entire resources is available for the scheduler at the base station to perform reallocation, while the interference situation for users in other cells remains the same. By reallocation, the scheduler is capable of balancing the QoS demands between users with high CQI and those with low CQI. Scheduler PHY CQI of all users DLC QoS criteria: - delay, - throughput, … MPEG tải về 7.55 Mb. Chia sẻ với bạn bè của bạn:
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