{"action":"created","issue":{"url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/51","labels_url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/51/labels{/name}","comments_url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/51/comments","events_url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/51/events","html_url":"https://github.com/ptrkrysik/gr-gsm/issues/51","id":77637150,"number":51,"title":"Proposal: channel hopping","user":{"login":"rpp0","id":8259336,"avatar_url":"https://avatars.githubusercontent.com/u/8259336?v=3","gravatar_id":"","url":"https://api.github.com/users/rpp0","html_url":"https://github.com/rpp0","followers_url":"https://api.github.com/users/rpp0/followers","following_url":"https://api.github.com/users/rpp0/following{/other_user}","gists_url":"https://api.github.com/users/rpp0/gists{/gist_id}","starred_url":"https://api.github.com/users/rpp0/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rpp0/subscriptions","organizations_url":"https://api.github.com/users/rpp0/orgs","repos_url":"https://api.github.com/users/rpp0/repos","events_url":"https://api.github.com/users/rpp0/events{/privacy}","received_events_url":"https://api.github.com/users/rpp0/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":9,"created_at":"2015-05-18T12:27:23Z","updated_at":"2015-05-19T15:05:17Z","closed_at":null,"body":"Dear all,\r\n\r\nI'm trying to implement real time channel hopping for gr-gsm. Here are some approaches that I considered:\r\n* Capture a wide portion of the spectrum, channelize using the Polyphase Channelizer block and then parse all channels simultaneously similar to how it is done in this project: https://github.com/BogdanDIA/airprobe-hopping. The disadvantage of this approach is that doing this in real time is very expensive, and in my opinion infeasible. Could be handy though when decoding from a file instead of real time.\r\n* Parse an Immediate Assignment, calculate the hopping sequence and \"follow\" it in the same way an ordinary phone would. Currently I have a basic implementation that does this by parsing the Immediate Assignment and communicating the frequency to the Source block over Unix domain sockets. However, I'm not sure whether this is fast enough considering the switch must happen in 1ms.\r\n\r\nIn any case, I'm currently stuck with parsing the first hop to a SDCCH channel. I tried using the TCH/F demapper from [this branch](https://github.com/ptrkrysik/gr-gsm/tree/romankh-master) but I'm not getting any data in Wireshark. I was expecting to see some control data or occasional packets from phones hopping to the channel in question. Is decoding the SDCCH already supported? If not I would be happy to help :)."},"comment":{"url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/comments/103539481","html_url":"https://github.com/ptrkrysik/gr-gsm/issues/51#issuecomment-103539481","issue_url":"https://api.github.com/repos/ptrkrysik/gr-gsm/issues/51","id":103539481,"user":{"login":"rpp0","id":8259336,"avatar_url":"https://avatars.githubusercontent.com/u/8259336?v=3","gravatar_id":"","url":"https://api.github.com/users/rpp0","html_url":"https://github.com/rpp0","followers_url":"https://api.github.com/users/rpp0/followers","following_url":"https://api.github.com/users/rpp0/following{/other_user}","gists_url":"https://api.github.com/users/rpp0/gists{/gist_id}","starred_url":"https://api.github.com/users/rpp0/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rpp0/subscriptions","organizations_url":"https://api.github.com/users/rpp0/orgs","repos_url":"https://api.github.com/users/rpp0/repos","events_url":"https://api.github.com/users/rpp0/events{/privacy}","received_events_url":"https://api.github.com/users/rpp0/received_events","type":"User","site_admin":false},"created_at":"2015-05-19T15:05:17Z","updated_at":"2015-05-19T15:05:17Z","body":"I had less time today than expected, but I created a channelized data set and managed to receive multiple streams simultaneously. SDCCH reception is working fine, but I'm still working on getting data from the hopping CX channels."}}