Multi-BTS with handover » History » Version 13
laforge, 03/23/2018 12:56 PM
legacy
| 1 | 13 | laforge | {{include(cellular-infrastructure:MacroLegacy)}} |
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| 2 | |||
| 3 | 11 | {{>toc}} |
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| 4 | 1 | ||
| 5 | 11 | h2. Configuring [[OpenBSC]] with muiltiple BTS and in-call handover |
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| 6 | 1 | ||
| 7 | 11 | ||
| 8 | |||
| 9 | h3. Prerequisites |
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| 10 | |||
| 11 | |||
| 12 | 1 | It is assumed that you already have a functioning BSC/NITB, and two or more BTS available. |
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| 13 | |||
| 14 | 11 | Note that if you are using BTS based on [[OsmoBTS]]/OsmoTRX handover requires: |
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| 15 | 1 | ||
| 16 | 11 | * osmo-bts package version >= fw-5 (this "fix":http://cgit.osmocom.org/osmo-bts/commit/?h=fairwaves/master&id=a6ad0b44ae45a2fd51b6a55507e8295605431e92 is included) |
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| 17 | * osmo-trx package version >= 0.2.0 (this "patch":http://cgit.osmocom.org/osmo-trx/commit/?h=fairwaves/master&id=19c392df82fe7acd303e4340059c87c432623881 is included) |
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| 18 | 1 | ||
| 19 | |||
| 20 | 11 | h3. Example network architecture |
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| 21 | 1 | ||
| 22 | 11 | ||
| 23 | In this example we have one system running the BSC/NITB software and two BTS that are built on the [[OsmoBTS]] software. |
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| 24 | |||
| 25 | 12 | laforge | {{graphviz_link() |
| 26 | 1 | digraph G { |
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| 27 | rankdir = LR; |
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| 28 | BSC -> BTS0 [ label = "A-bis" dir=both ]; |
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| 29 | BSC -> BTS1 [ label = "A-bis" dir=both ]; |
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| 30 | BSC [ shape = square label = "BSC\n172.30.1.10" ]; |
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| 31 | BTS0 [ shape = square label = "BTS 0\n172.30.1.11" ]; |
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| 32 | BTS1 [ shape = square label = "BTS 1\n172.30.1.12" ]; |
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| 33 | } |
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| 34 | 12 | laforge | }} |
| 35 | 8 | ipse | |
| 36 | 1 | ||
| 37 | 11 | h3. BTS configuration |
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| 38 | 1 | ||
| 39 | |||
| 40 | 11 | There are three [[OsmoBTS]] parameters in particular which must be correctly configured: |
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| 41 | |||
| 42 | * *bts* - BTS number in a config file, always 0 for a BTS configuration file, 0..n for the NITB configuration file |
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| 43 | * *band* - the band in which the BTS will operate |
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| 44 | * *ipa unit-id* - each BTS must use a unique value |
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| 45 | * *oml remote-ip* - this is the BSC IP address |
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| 46 | |||
| 47 | 3 | The example configuration that follows is for two BTS both on the GSM900 band. |
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| 48 | |||
| 49 | |||
| 50 | 11 | h4. BTS 0 |
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| 51 | |||
| 52 | |||
| 53 | 1 | Find the aforementioned parameters and ensure that they are correctly set. |
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| 54 | |||
| 55 | 11 | <pre> |
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| 56 | 1 | bts 0 |
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| 57 | band GSM900 |
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| 58 | ipa unit-id 1801 0 |
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| 59 | oml remote-ip 172.30.1.10 |
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| 60 | 3 | ... |
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| 61 | 11 | </code></pre> |
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| 62 | 3 | ||
| 63 | 1 | ||
| 64 | 11 | h4. BTS 1 |
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| 65 | 3 | ||
| 66 | 11 | ||
| 67 | Ensure that the second BTS has a different *ipa unit-id* configured from the first. |
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| 68 | |||
| 69 | <pre> |
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| 70 | 7 | bts 0 |
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| 71 | 3 | band GSM900 |
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| 72 | ipa unit-id 1802 0 |
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| 73 | oml remote-ip 172.30.1.10 |
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| 74 | ... |
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| 75 | 11 | </code></pre> |
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| 76 | 3 | ||
| 77 | 1 | ||
| 78 | 11 | h3. BSC configuration |
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| 79 | |||
| 80 | |||
| 81 | 3 | There are a number of BSC/NITB parameters that you must pay particular attention to: |
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| 82 | |||
| 83 | 11 | * *BTS _n* |
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| 84 | *** *band* - as configured in the BTS |
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| 85 | *** *base_station_id_code* - should be unique in location area |
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| 86 | *** *ip.access unit_id* - as configured in the BTS |
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| 87 | *** *trx _n_ |
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| 88 | ****** *arfcn* - this must be frequencies that you have a licence for and unique across all neighbouring BTS |
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| 89 | * *neighbor-list mode automatic* |
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| 90 | 3 | ||
| 91 | 11 | Configure the first BTS within the BSC/NITB, ensuring that you have set the correct *band* and *ip.access unit_id*, and an appropriate *arfcn* for each TRX. |
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| 92 | 3 | ||
| 93 | 11 | <pre> |
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| 94 | 10 | bts 0 |
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| 95 | 3 | ... |
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| 96 | band GSM900 |
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| 97 | 1 | ... |
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| 98 | base_station_id_code 63 |
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| 99 | 3 | ... |
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| 100 | 1 | ip.access unit_id 1801 0 |
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| 101 | ... |
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| 102 | neighbor-list mode automatic |
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| 103 | ... |
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| 104 | trx 0 |
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| 105 | rf_locked 0 |
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| 106 | arfcn 74 |
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| 107 | ... |
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| 108 | trx 1 |
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| 109 | rf_locked 0 |
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| 110 | arfcn 84 |
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| 111 | ... |
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| 112 | 11 | </code></pre> |
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| 113 | 3 | ||
| 114 | 11 | Next configure the second BTS, ensuring that a different *base_station_id_code* is used this time, once again the correct *ip.access unit_id* is set, and an appropriate *arfcn* for each TRX: |
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| 115 | 3 | ||
| 116 | 11 | <pre> |
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| 117 | 3 | bts 1 |
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| 118 | ... |
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| 119 | band GSM900 |
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| 120 | 4 | ipse | ... |
| 121 | 3 | base_station_id_code 62 |
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| 122 | 1 | ... |
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| 123 | 3 | ip.access unit_id 1802 0 |
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| 124 | ... |
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| 125 | neighbor-list mode automatic |
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| 126 | 1 | ... |
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| 127 | trx 0 |
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| 128 | rf_locked 0 |
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| 129 | 3 | arfcn 111 |
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| 130 | ... |
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| 131 | trx 1 |
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| 132 | rf_locked 0 |
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| 133 | 1 | arfcn 122 |
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| 134 | ... |
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| 135 | 11 | </code></pre> |
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| 136 | 3 | ||
| 137 | 11 | For details of all the configuration options please see the [[osmo-nitb_VTY|NITB VTY reference]]. |
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| 138 | 1 | ||
| 139 | |||
| 140 | 11 | h4. Handover |
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| 141 | |||
| 142 | |||
| 143 | 3 | The following parameters must also be configured in order to enable handover: |
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| 144 | |||
| 145 | 11 | * *handover 1* |
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| 146 | *** _Enable in-call handover between multiple BTS._ |
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| 147 | 3 | ||
| 148 | 11 | * *handover window rxlev averaging 10* |
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| 149 | *** _The receive level of the serving cell should be averaged over 10 SACCH frames._ |
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| 150 | 3 | ||
| 151 | 11 | * *handover window rxqual averaging 1* |
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| 152 | *** _The receive quality of the serving cell should be averaged over 1 SACCH frame._ |
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| 153 | 3 | ||
| 154 | 11 | * *handover window rxlev neighbor averaging 10* |
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| 155 | *** _The Rx Level of a neighbour cell should be averaged over 10 SACCH frames._ |
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| 156 | 3 | ||
| 157 | 11 | * *handover power budget interval 6* |
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| 158 | *** _Consider performing a power budget (Rx level) handover every 6 SACCH frames._ |
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| 159 | 3 | ||
| 160 | 11 | * *handover power budget hysteresis 3* |
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| 161 | *** _Set hysteresis (prevents continuous handover back and forth) to 3._ |
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| 162 | 3 | ||
| 163 | 11 | * *handover maximum distance 9999* |
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| 164 | *** _When the distance from the BTS is greater than 9999 attempt a distance handover._ |
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| 165 | 1 | ||
| 166 | 11 | These parameters must be set within the *network* section of the BSC/NITB configuration: |
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| 167 | 1 | ||
| 168 | 11 | <pre> |
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| 169 | 3 | network |
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| 170 | network country code 1 |
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| 171 | ... |
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| 172 | handover 1 |
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| 173 | 9 | ipse | handover window rxlev averaging 10 |
| 174 | handover window rxqual averaging 1 |
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| 175 | handover window rxlev neighbor averaging 10 |
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| 176 | handover power budget interval 6 |
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| 177 | handover power budget hysteresis 3 |
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| 178 | handover maximum distance 9999 |
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| 179 | 11 | </code></pre> |
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| 180 | 3 | ||
| 181 | 7 | Values can be tuned to modify the behaviour of handover. |
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| 182 | 3 | ||
| 183 | |||
| 184 | 11 | h3. Testing handover |
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| 185 | |||
| 186 | |||
| 187 | 3 | To test handover you have two options: |
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| 188 | |||
| 189 | 1. Physically move a phone to trigger handover decision. |
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| 190 | 1 | 2. Use "subscriber ID handover BTS_NR" command in the NITB VTY to force handover. |
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| 191 | |||
| 192 | 11 | h3. Complete configurations |
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| 193 | |||
| 194 | |||
| 195 | 1 | Complete example configs are included here for reference only and should not be used without modification, unless you happen to have a licence for those particular frequencies. |
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| 196 | |||
| 197 | |||
| 198 | 11 | h4. BTS 0 |
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| 199 | |||
| 200 | |||
| 201 | <pre> |
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| 202 | 1 | bts 0 |
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| 203 | band GSM900 |
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| 204 | ipa unit-id 1801 0 |
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| 205 | oml remote-ip 172.30.1.10 |
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| 206 | rtp jitter-buffer 0 |
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| 207 | paging lifetime 0 |
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| 208 | gsmtap-sapi bcch |
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| 209 | gsmtap-sapi ccch |
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| 210 | gsmtap-sapi rach |
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| 211 | gsmtap-sapi agch |
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| 212 | gsmtap-sapi pch |
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| 213 | gsmtap-sapi sdcch |
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| 214 | gsmtap-sapi pacch |
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| 215 | gsmtap-sapi pdtch |
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| 216 | gsmtap-sapi sacch |
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| 217 | fn-advance 20 |
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| 218 | ms-power-loop -10 |
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| 219 | timing-advance-loop |
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| 220 | trx 0 |
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| 221 | 8 | ipse | rxgain 12 |
| 222 | 1 | power 0 |
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| 223 | trx 1 |
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| 224 | 3 | rxgain 12 |
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| 225 | 1 | power 0 |
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| 226 | 11 | </code></pre> |
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| 227 | 1 | ||
| 228 | |||
| 229 | 11 | h4. BTS 1 |
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| 230 | |||
| 231 | |||
| 232 | <pre> |
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| 233 | 1 | bts 0 |
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| 234 | band GSM900 |
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| 235 | ipa unit-id 1802 0 |
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| 236 | oml remote-ip 172.30.1.10 |
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| 237 | rtp jitter-buffer 0 |
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| 238 | paging lifetime 0 |
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| 239 | gsmtap-sapi bcch |
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| 240 | gsmtap-sapi ccch |
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| 241 | gsmtap-sapi rach |
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| 242 | gsmtap-sapi agch |
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| 243 | gsmtap-sapi pch |
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| 244 | gsmtap-sapi sdcch |
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| 245 | gsmtap-sapi pacch |
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| 246 | gsmtap-sapi pdtch |
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| 247 | gsmtap-sapi sacch |
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| 248 | 7 | fn-advance 20 |
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| 249 | ms-power-loop -10 |
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| 250 | 1 | timing-advance-loop |
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| 251 | trx 0 |
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| 252 | rxgain 12 |
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| 253 | power 0 |
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| 254 | trx 1 |
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| 255 | rxgain 12 |
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| 256 | power 0 |
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| 257 | 11 | </code></pre> |
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| 258 | 1 | ||
| 259 | |||
| 260 | 11 | h4. [[OpenBSC]] NITB |
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| 261 | 1 | ||
| 262 | 11 | ||
| 263 | Note that whilst this configuration is for NITB operation, the updates describe above could equally be applied to [[OpenBSC]] configured in BSC-only mode and with an external MSC etc. |
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| 264 | |||
| 265 | <pre> |
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| 266 | 1 | ! |
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| 267 | ! OpenBSC (UNKNOWN) configuration saved from vty |
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| 268 | !! |
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| 269 | password foo |
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| 270 | ! |
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| 271 | line vty |
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| 272 | no login |
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| 273 | ! |
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| 274 | e1_input |
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| 275 | e1_line 0 driver ipa |
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| 276 | e1_line 0 port 0 |
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| 277 | no e1_line 0 keepalive |
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| 278 | network |
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| 279 | network country code 1 |
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| 280 | mobile network code 1 |
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| 281 | short name Osmocom |
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| 282 | long name Osmocom |
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| 283 | auth policy accept-all |
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| 284 | location updating reject cause 13 |
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| 285 | encryption a5 0 |
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| 286 | neci 1 |
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| 287 | paging any use tch 0 |
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| 288 | rrlp mode none |
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| 289 | mm info 1 |
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| 290 | handover 1 |
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| 291 | handover window rxlev averaging 10 |
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| 292 | handover window rxqual averaging 1 |
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| 293 | handover window rxlev neighbor averaging 10 |
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| 294 | handover power budget interval 6 |
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| 295 | handover power budget hysteresis 3 |
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| 296 | handover maximum distance 9999 |
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| 297 | timer t3101 10 |
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| 298 | timer t3103 0 |
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| 299 | timer t3105 0 |
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| 300 | timer t3107 0 |
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| 301 | timer t3109 4 |
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| 302 | timer t3111 0 |
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| 303 | timer t3113 60 |
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| 304 | timer t3115 0 |
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| 305 | timer t3117 0 |
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| 306 | timer t3119 0 |
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| 307 | timer t3122 10 |
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| 308 | timer t3141 0 |
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| 309 | dtx-used 0 |
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| 310 | subscriber-keep-in-ram 0 |
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| 311 | bts 0 |
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| 312 | type sysmobts |
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| 313 | band GSM900 |
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| 314 | cell_identity 0 |
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| 315 | location_area_code 1 |
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| 316 | base_station_id_code 63 |
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| 317 | ms max power 15 |
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| 318 | cell reselection hysteresis 4 |
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| 319 | rxlev access min 0 |
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| 320 | periodic location update 30 |
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| 321 | radio-link-timeout 32 |
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| 322 | channel allocator ascending |
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| 323 | rach tx integer 9 |
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| 324 | rach max transmission 7 |
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| 325 | channel-descrption attach 1 |
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| 326 | channel-descrption bs-pa-mfrms 5 |
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| 327 | channel-descrption bs-ag-blks-res 1 |
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| 328 | ip.access unit_id 1801 0 |
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| 329 | oml ip.access stream_id 255 line 0 |
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| 330 | neighbor-list mode automatic |
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| 331 | gprs mode none |
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| 332 | no force-combined-si |
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| 333 | trx 0 |
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| 334 | rf_locked 0 |
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| 335 | arfcn 74 |
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| 336 | nominal power 23 |
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| 337 | max_power_red 0 |
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| 338 | rsl e1 tei 0 |
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| 339 | timeslot 0 |
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| 340 | phys_chan_config CCCH+SDCCH4 |
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| 341 | hopping enabled 0 |
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| 342 | timeslot 1 |
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| 343 | phys_chan_config SDCCH8 |
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| 344 | hopping enabled 0 |
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| 345 | timeslot 2 |
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| 346 | phys_chan_config TCH/F |
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| 347 | hopping enabled 0 |
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| 348 | timeslot 3 |
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| 349 | phys_chan_config TCH/F |
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| 350 | hopping enabled 0 |
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| 351 | timeslot 4 |
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| 352 | phys_chan_config TCH/F |
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| 353 | hopping enabled 0 |
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| 354 | timeslot 5 |
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| 355 | phys_chan_config TCH/F |
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| 356 | hopping enabled 0 |
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| 357 | timeslot 6 |
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| 358 | phys_chan_config TCH/F |
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| 359 | hopping enabled 0 |
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| 360 | timeslot 7 |
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| 361 | phys_chan_config TCH/F |
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| 362 | hopping enabled 0 |
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| 363 | trx 1 |
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| 364 | rf_locked 0 |
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| 365 | arfcn 84 |
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| 366 | nominal power 23 |
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| 367 | max_power_red 0 |
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| 368 | rsl e1 tei 0 |
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| 369 | timeslot 0 |
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| 370 | phys_chan_config TCH/F |
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| 371 | hopping enabled 0 |
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| 372 | timeslot 1 |
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| 373 | phys_chan_config TCH/F |
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| 374 | hopping enabled 0 |
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| 375 | timeslot 2 |
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| 376 | phys_chan_config TCH/F |
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| 377 | hopping enabled 0 |
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| 378 | timeslot 3 |
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| 379 | phys_chan_config TCH/F |
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| 380 | hopping enabled 0 |
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| 381 | timeslot 4 |
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| 382 | phys_chan_config TCH/F |
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| 383 | hopping enabled 0 |
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| 384 | timeslot 5 |
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| 385 | phys_chan_config TCH/F |
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| 386 | hopping enabled 0 |
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| 387 | timeslot 6 |
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| 388 | phys_chan_config TCH/F |
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| 389 | hopping enabled 0 |
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| 390 | timeslot 7 |
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| 391 | phys_chan_config TCH/F |
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| 392 | hopping enabled 0 |
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| 393 | bts 1 |
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| 394 | type sysmobts |
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| 395 | band GSM900 |
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| 396 | cell_identity 0 |
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| 397 | location_area_code 1 |
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| 398 | base_station_id_code 62 |
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| 399 | ms max power 15 |
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| 400 | cell reselection hysteresis 4 |
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| 401 | rxlev access min 0 |
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| 402 | periodic location update 30 |
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| 403 | radio-link-timeout 32 |
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| 404 | channel allocator ascending |
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| 405 | rach tx integer 9 |
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| 406 | rach max transmission 7 |
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| 407 | channel-descrption attach 1 |
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| 408 | channel-descrption bs-pa-mfrms 5 |
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| 409 | channel-descrption bs-ag-blks-res 1 |
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| 410 | ip.access unit_id 1802 0 |
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| 411 | oml ip.access stream_id 255 line 0 |
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| 412 | neighbor-list mode automatic |
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| 413 | gprs mode none |
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| 414 | no force-combined-si |
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| 415 | trx 0 |
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| 416 | rf_locked 0 |
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| 417 | arfcn 111 |
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| 418 | nominal power 23 |
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| 419 | max_power_red 0 |
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| 420 | rsl e1 tei 0 |
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| 421 | timeslot 0 |
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| 422 | phys_chan_config CCCH+SDCCH4 |
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| 423 | hopping enabled 0 |
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| 424 | timeslot 1 |
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| 425 | phys_chan_config SDCCH8 |
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| 426 | hopping enabled 0 |
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| 427 | timeslot 2 |
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| 428 | phys_chan_config TCH/F |
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| 429 | hopping enabled 0 |
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| 430 | timeslot 3 |
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| 431 | phys_chan_config TCH/F |
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| 432 | hopping enabled 0 |
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| 433 | timeslot 4 |
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| 434 | phys_chan_config TCH/F |
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| 435 | hopping enabled 0 |
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| 436 | timeslot 5 |
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| 437 | phys_chan_config TCH/F |
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| 438 | hopping enabled 0 |
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| 439 | timeslot 6 |
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| 440 | phys_chan_config TCH/F |
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| 441 | hopping enabled 0 |
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| 442 | timeslot 7 |
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| 443 | phys_chan_config TCH/F |
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| 444 | hopping enabled 0 |
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| 445 | trx 1 |
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| 446 | rf_locked 0 |
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| 447 | 2 | arfcn 122 |
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| 448 | 1 | nominal power 23 |
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| 449 | max_power_red 0 |
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| 450 | rsl e1 tei 0 |
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| 451 | timeslot 0 |
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| 452 | phys_chan_config TCH/F |
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| 453 | hopping enabled 0 |
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| 454 | timeslot 1 |
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| 455 | phys_chan_config TCH/F |
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| 456 | hopping enabled 0 |
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| 457 | timeslot 2 |
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| 458 | phys_chan_config TCH/F |
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| 459 | hopping enabled 0 |
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| 460 | timeslot 3 |
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| 461 | phys_chan_config TCH/F |
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| 462 | hopping enabled 0 |
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| 463 | timeslot 4 |
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| 464 | phys_chan_config TCH/F |
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| 465 | hopping enabled 0 |
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| 466 | timeslot 5 |
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| 467 | phys_chan_config TCH/F |
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| 468 | hopping enabled 0 |
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| 469 | timeslot 6 |
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| 470 | phys_chan_config TCH/F |
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| 471 | hopping enabled 0 |
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| 472 | timeslot 7 |
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| 473 | phys_chan_config TCH/F |
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| 474 | hopping enabled 0 |
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| 475 | 11 | </code></pre> |
