# Uplink & downlink at the same channel frequency

**URL:** <https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824>\
**Category:** LimeSDR\
**Created:** [23 February 2017 04:39 UTC](https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824 "2017-02-23T04:39:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![rohkes](https://avatars.discourse-cdn.com/v4/letter/r/87869e/32.png) [@rohkes](https://discourse.myriadrf.org/u/rohkes)\
**Post date:** [23 February 2017 04:39 UTC](https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824/1 "2017-02-23T04:39:34Z")

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Hi,

Since the LimeSDR is a full duplex radio, has anyone here attempted self-interference cancellation on the FPGA to transmit and receive at the same channel frequency?

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**Author:** ![Kryan92](https://avatars.discourse-cdn.com/v4/letter/k/e480ec/32.png) [@Kryan92](https://discourse.myriadrf.org/u/Kryan92)\
**Post date:** [24 February 2017 04:50 UTC](https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824/2 "2017-02-24T04:50:02Z")

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I haven’t, but am very much interested in making the FPGA modifications for items like this and other accelerated processing.

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**Author:** ![Kryan92](https://avatars.discourse-cdn.com/v4/letter/k/e480ec/32.png) [@Kryan92](https://discourse.myriadrf.org/u/Kryan92)\
**Post date:** [25 February 2017 21:09 UTC](https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824/3 "2017-02-25T21:09:45Z")

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@rohkes, I just compiled v1.4 gateware. It looks like only 17% of the Cyclone IV LE’s are being used at the moment, so there should be plenty of room to add on-board real-time signal processing.

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**Author:** ![rohkes](https://avatars.discourse-cdn.com/v4/letter/r/87869e/32.png) [@rohkes](https://discourse.myriadrf.org/u/rohkes)\
**Post date:** [27 February 2017 06:18 UTC](https://discourse.myriadrf.org/t/uplink-downlink-at-the-same-channel-frequency/824/4 "2017-02-27T06:18:33Z")

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@Kryan92 this paper ([https://arxiv.org/pdf/1607.01912.pdf](https://arxiv.org/pdf/1607.01912.pdf)) seems to indicate the need of active analog cancellation as well as digital. I don’t think this would be possible with the current version of the limesdr but if there were programmable analog elements then the limesdr would probably be a very good platform for further research into this. Although, I don’t know of any way in which we could make configurable analog elements for something like this.