無線資料下載服務之排程感知功率控制

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2009

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在高速資料蜂巢式網路中,如HDR系統,採用的是分時多工(TDM)的技術來達到高速下載的目的。而在TDM系統中,時間被分隔為許多的時間槽(time slots),且在每一個時間槽中只有一位使用者可以被其基地台服務。而這位被服務的使用者是根據基地台的排程策略來挑選。因此我們提出根據此排程使用者的頻道品質狀況(channel condition)來調整基地台的傳輸功率(transmission power),此外,我們將基地台的流量負載(traffic loading)也一併考慮到我們的演算法中。我們的基地台功率調整方法會讓流量負載高且排程使用者之頻道品質狀況不佳的基地台使用最大的傳輸功率,同時,讓流量負載低且排程使用者之頻道品質狀況好的基地台使用較低的傳輸功率減少對其他基地台的干擾。另外,我們考慮到功率調整頻繁的問題,修改我們的演算法使得基地台不會因為太過頻繁的切換功率而導致系統無法運作。 我們在不同的環境情景中,如慢速衰弱(slow fading)、 快速衰弱(fast fading)及空間型聚集熱點(spatial hotspot),利用電腦模擬實驗。實驗結果顯示,我們提出的方法在封包延遲時間(packet delay)以及有效服務速率(effective service rate)上都能有優異的表現,並且在空間型聚集熱點中,能有效減少基地台的流量負載(load relief)。另外,透過有效的控制cell間的干擾(inter-cell interference),位於cell邊界的使用者的各項效能表現也能有所改善。
In high speed cellular data network, such as HDR system, TDM (time division multiplexing) technique is adopted. In TDM system, time is divided into time slots and only one user can be served by the BS during a time slot. The user to be served by the BS is chosen by the scheduling policy. We then propose a base station antenna power level control scheme based on the channel condition of the scheduled user. In addition, we assumed that the information of sectorized loading is available and this information is taken into account for modifying the proposed algorithm. Our proposed scheme let high loading BSs with scheduled user who is in bad channel condition to transmit in full transmission power. Meanwhile, the proposed scheme let low loading BSs with scheduled user who is in good channel condition to transmit in lower transmission power. In addition, we considered the switching power frequency and modified the proposed scheme that let the BSs not to switch the antenna power too frequently. We simulated the proposed scheme in slow fading, fast fading and spatial hotspot scenarios. The simulation results show that our proposed scheme outperforms in delay-throughput characteristics, and provides higher effective service rate. Moreover, the proposed scheme improves the performance of users near the cell edge through the control of inter-cell interference.

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蜂巢式網路, 功率等級控制, 下行鏈路, 訊號干擾, cellular networks, power level control, forward link, inter-cell interference

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