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2024-08-15 01:14本頁面
【正文】 Uplink Interference (7) A cell is considered OK if it has RSSI coverage and both uplink and downlink SIR’s are higher than 10 dB. Now, OF in formula (3) can be used to find the best configuration for the system. That is, what AP’s to use and what channel to use at each AP. After the calculation is done, OK cells, cells with excessive uplink and/or downlink interference can all be graphically displayed. (3) .The same example is used for channel assignment demonstration. In order to keep the % coverage, we keep the same configuration, . we used the 40 AP’s suggested by the coverage optimization. After the OF of (3) is optimized, we get a % OK rate. That is while % of the area has signal coverage, only % of the area has adequate munications quality. The result is shown in Figure 5. The white number shows the channel assigned. The green shows OK area. The black cells show area without coverage. The dark gray area is where there is coverage but the downlink cochannel interference is too high, . SIR is less than 10 dB. The light gray cells are where there is coverage, high enough downlink SIR but uplink interference is too high. It can be seen that uplink interference is far more serious than the downlink. Under the current conditions, only % of the outdoor areas have adequate munications. %(3)%的cell %%%擁有良好的通訊品質(zhì)Figure 5 Optimum channel assignment with 3 channels shows that % of the area has adequate munications.Using all 60 AP’s in the optimization process actually makes it worse. Only % of the area is OK in this case as shown in Figure 6 below:%.Figure 6 Optimum channel assignment with 60 AP’s has worse result. Only % area is OK.D． Overlapping ChannelsWe have only used the nonoverlapping channels, 1, 6, and 11 in above discussions. Since in the frequency spectrum, the other channels are partially overlapping with channels 1, 6, and 11, and with each other, there is a potential that these channels can be used when the spatial factor proves appropriate. In other words, when the spatial separation is not enough for a channel to be reused because it’s spectrum overlaps fully with itself, there is the possibility that a partially overlapping channel can be used. Also, there are spectrum gaps between these three channels. For example, if we put half of the AP’s already on channel 1 on channel 2, we reduce the cochannel interference because some fully overlapping AP’s are partially overlapping now.,This situation opens up the possibility of using the other channels and thus enhances the capacity and/or coverage of the RF system. Since it depends on the configuration and geography of the system, the results cannot be ascertained in general. For the example on hand we get the following, if we utilize all eleven channels.. Figure 6 Optimum channel assignment using all 11 channels boosts OK area to %.We can now boost the OK area from % to %. The amount of improvement depends on the system configuration as mentioned before. Here for better viewing, dark gray i
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