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doc:lps:twr-tdma [2017-07-18 15:32] arnaud created |
doc:lps:twr-tdma [2017-07-18 15:41] arnaud [System performance] |
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===== Abstract ===== | ===== Abstract ===== | ||
- | The Two Way Ranging Time Division Multiple Access (TWR-TDMA) mode allows to position multiple tag in Two Way Ranging mode (TWR). | + | The Two Way Ranging |
The TWR mode is an active ranging mode where the tag is pinging the anchors in order to measure the distance between the tag and the anchor. By doing so on multiple anchor and by knowing the anchor position, the tag can calculate its own position. | The TWR mode is an active ranging mode where the tag is pinging the anchors in order to measure the distance between the tag and the anchor. By doing so on multiple anchor and by knowing the anchor position, the tag can calculate its own position. | ||
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The disadvantage is that the tag has to actively send packets, it means that two tag cannot range at the same time and so some synchronization mechanism has to be put in place to allow multiple tag to use TWR measurement concurrently. | The disadvantage is that the tag has to actively send packets, it means that two tag cannot range at the same time and so some synchronization mechanism has to be put in place to allow multiple tag to use TWR measurement concurrently. | ||
- | With TWR-TDMA | + | TWR-TDMA |
===== Compiling Crazyflie for TWR-TDMA ranging ===== | ===== Compiling Crazyflie for TWR-TDMA ranging ===== | ||
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===== System performance ===== | ===== System performance ===== | ||
- | TWR-TDMA is currently implemented with time slots of 4ms. Each time slot is used by one tag to range with one anchor. This means that the ranging rate is of //1/(0.004 * (2^TDMA_NSLOTS_BITS)// | + | TWR-TDMA is currently implemented with time slots of 4ms. Each time slot is used by one tag to range with one anchor. This means that the ranging rate is of //1/(0.004 * 2^TDMA_NSLOTS_BITS)// |
- | The more timeslots, the less often measurements can be used to estimate the tag position and so the performance of the position estimate will deteriorate. For a great number of tag the [[doc: | + | The more timeslots |