Multi-BTS with handover » History » Version 12
laforge, 02/21/2016 07:50 AM
| 1 | 11 | {{>toc}} |
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| 2 | 1 | ||
| 3 | 11 | h2. Configuring [[OpenBSC]] with muiltiple BTS and in-call handover |
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| 4 | 1 | ||
| 5 | 11 | ||
| 6 | |||
| 7 | h3. Prerequisites |
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| 8 | |||
| 9 | |||
| 10 | 1 | It is assumed that you already have a functioning BSC/NITB, and two or more BTS available. |
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| 11 | |||
| 12 | 11 | Note that if you are using BTS based on [[OsmoBTS]]/OsmoTRX handover requires: |
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| 13 | 1 | ||
| 14 | 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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| 15 | * 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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| 16 | 1 | ||
| 17 | |||
| 18 | 11 | h3. Example network architecture |
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| 19 | 1 | ||
| 20 | 11 | ||
| 21 | 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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| 22 | |||
| 23 | 12 | laforge | {{graphviz_link() |
| 24 | 1 | digraph G { |
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| 25 | rankdir = LR; |
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| 26 | BSC -> BTS0 [ label = "A-bis" dir=both ]; |
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| 27 | BSC -> BTS1 [ label = "A-bis" dir=both ]; |
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| 28 | BSC [ shape = square label = "BSC\n172.30.1.10" ]; |
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| 29 | BTS0 [ shape = square label = "BTS 0\n172.30.1.11" ]; |
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| 30 | BTS1 [ shape = square label = "BTS 1\n172.30.1.12" ]; |
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| 31 | } |
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| 32 | 12 | laforge | }} |
| 33 | 8 | ipse | |
| 34 | 1 | ||
| 35 | 11 | h3. BTS configuration |
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| 36 | 1 | ||
| 37 | |||
| 38 | 11 | There are three [[OsmoBTS]] parameters in particular which must be correctly configured: |
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| 39 | |||
| 40 | * *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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| 41 | * *band* - the band in which the BTS will operate |
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| 42 | * *ipa unit-id* - each BTS must use a unique value |
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| 43 | * *oml remote-ip* - this is the BSC IP address |
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| 44 | |||
| 45 | 3 | The example configuration that follows is for two BTS both on the GSM900 band. |
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| 46 | |||
| 47 | |||
| 48 | 11 | h4. BTS 0 |
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| 49 | |||
| 50 | |||
| 51 | 1 | Find the aforementioned parameters and ensure that they are correctly set. |
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| 52 | |||
| 53 | 11 | <pre> |
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| 54 | 1 | bts 0 |
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| 55 | band GSM900 |
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| 56 | ipa unit-id 1801 0 |
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| 57 | oml remote-ip 172.30.1.10 |
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| 58 | 3 | ... |
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| 59 | 11 | </code></pre> |
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| 60 | 3 | ||
| 61 | 1 | ||
| 62 | 11 | h4. BTS 1 |
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| 63 | 3 | ||
| 64 | 11 | ||
| 65 | Ensure that the second BTS has a different *ipa unit-id* configured from the first. |
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| 66 | |||
| 67 | <pre> |
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| 68 | 7 | bts 0 |
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| 69 | 3 | band GSM900 |
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| 70 | ipa unit-id 1802 0 |
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| 71 | oml remote-ip 172.30.1.10 |
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| 72 | ... |
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| 73 | 11 | </code></pre> |
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| 74 | 3 | ||
| 75 | 1 | ||
| 76 | 11 | h3. BSC configuration |
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| 77 | |||
| 78 | |||
| 79 | 3 | There are a number of BSC/NITB parameters that you must pay particular attention to: |
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| 80 | |||
| 81 | 11 | * *BTS _n* |
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| 82 | *** *band* - as configured in the BTS |
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| 83 | *** *base_station_id_code* - should be unique in location area |
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| 84 | *** *ip.access unit_id* - as configured in the BTS |
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| 85 | *** *trx _n_ |
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| 86 | ****** *arfcn* - this must be frequencies that you have a licence for and unique across all neighbouring BTS |
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| 87 | * *neighbor-list mode automatic* |
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| 88 | 3 | ||
| 89 | 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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| 90 | 3 | ||
| 91 | 11 | <pre> |
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| 92 | 10 | bts 0 |
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| 93 | 3 | ... |
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| 94 | band GSM900 |
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| 95 | 1 | ... |
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| 96 | base_station_id_code 63 |
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| 97 | 3 | ... |
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| 98 | 1 | ip.access unit_id 1801 0 |
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| 99 | ... |
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| 100 | neighbor-list mode automatic |
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| 101 | ... |
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| 102 | trx 0 |
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| 103 | rf_locked 0 |
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| 104 | arfcn 74 |
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| 105 | ... |
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| 106 | trx 1 |
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| 107 | rf_locked 0 |
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| 108 | arfcn 84 |
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| 109 | ... |
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| 110 | 11 | </code></pre> |
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| 111 | 3 | ||
| 112 | 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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| 113 | 3 | ||
| 114 | 11 | <pre> |
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| 115 | 3 | bts 1 |
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| 116 | ... |
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| 117 | band GSM900 |
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| 118 | 4 | ipse | ... |
| 119 | 3 | base_station_id_code 62 |
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| 120 | 1 | ... |
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| 121 | 3 | ip.access unit_id 1802 0 |
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| 122 | ... |
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| 123 | neighbor-list mode automatic |
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| 124 | 1 | ... |
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| 125 | trx 0 |
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| 126 | rf_locked 0 |
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| 127 | 3 | arfcn 111 |
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| 128 | ... |
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| 129 | trx 1 |
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| 130 | rf_locked 0 |
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| 131 | 1 | arfcn 122 |
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| 132 | ... |
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| 133 | 11 | </code></pre> |
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| 134 | 3 | ||
| 135 | 11 | For details of all the configuration options please see the [[osmo-nitb_VTY|NITB VTY reference]]. |
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| 136 | 1 | ||
| 137 | |||
| 138 | 11 | h4. Handover |
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| 139 | |||
| 140 | |||
| 141 | 3 | The following parameters must also be configured in order to enable handover: |
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| 142 | |||
| 143 | 11 | * *handover 1* |
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| 144 | *** _Enable in-call handover between multiple BTS._ |
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| 145 | 3 | ||
| 146 | 11 | * *handover window rxlev averaging 10* |
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| 147 | *** _The receive level of the serving cell should be averaged over 10 SACCH frames._ |
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| 148 | 3 | ||
| 149 | 11 | * *handover window rxqual averaging 1* |
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| 150 | *** _The receive quality of the serving cell should be averaged over 1 SACCH frame._ |
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| 151 | 3 | ||
| 152 | 11 | * *handover window rxlev neighbor averaging 10* |
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| 153 | *** _The Rx Level of a neighbour cell should be averaged over 10 SACCH frames._ |
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| 154 | 3 | ||
| 155 | 11 | * *handover power budget interval 6* |
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| 156 | *** _Consider performing a power budget (Rx level) handover every 6 SACCH frames._ |
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| 157 | 3 | ||
| 158 | 11 | * *handover power budget hysteresis 3* |
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| 159 | *** _Set hysteresis (prevents continuous handover back and forth) to 3._ |
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| 160 | 3 | ||
| 161 | 11 | * *handover maximum distance 9999* |
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| 162 | *** _When the distance from the BTS is greater than 9999 attempt a distance handover._ |
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| 163 | 1 | ||
| 164 | 11 | These parameters must be set within the *network* section of the BSC/NITB configuration: |
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| 165 | 1 | ||
| 166 | 11 | <pre> |
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| 167 | 3 | network |
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| 168 | network country code 1 |
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| 169 | ... |
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| 170 | handover 1 |
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| 171 | 9 | ipse | handover window rxlev averaging 10 |
| 172 | handover window rxqual averaging 1 |
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| 173 | handover window rxlev neighbor averaging 10 |
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| 174 | handover power budget interval 6 |
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| 175 | handover power budget hysteresis 3 |
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| 176 | handover maximum distance 9999 |
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| 177 | 11 | </code></pre> |
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| 178 | 3 | ||
| 179 | 7 | Values can be tuned to modify the behaviour of handover. |
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| 180 | 3 | ||
| 181 | |||
| 182 | 11 | h3. Testing handover |
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| 183 | |||
| 184 | |||
| 185 | 3 | To test handover you have two options: |
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| 186 | |||
| 187 | 1. Physically move a phone to trigger handover decision. |
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| 188 | 1 | 2. Use "subscriber ID handover BTS_NR" command in the NITB VTY to force handover. |
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| 189 | |||
| 190 | 11 | h3. Complete configurations |
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| 191 | |||
| 192 | |||
| 193 | 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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| 194 | |||
| 195 | |||
| 196 | 11 | h4. BTS 0 |
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| 197 | |||
| 198 | |||
| 199 | <pre> |
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| 200 | 1 | bts 0 |
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| 201 | band GSM900 |
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| 202 | ipa unit-id 1801 0 |
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| 203 | oml remote-ip 172.30.1.10 |
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| 204 | rtp jitter-buffer 0 |
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| 205 | paging lifetime 0 |
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| 206 | gsmtap-sapi bcch |
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| 207 | gsmtap-sapi ccch |
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| 208 | gsmtap-sapi rach |
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| 209 | gsmtap-sapi agch |
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| 210 | gsmtap-sapi pch |
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| 211 | gsmtap-sapi sdcch |
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| 212 | gsmtap-sapi pacch |
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| 213 | gsmtap-sapi pdtch |
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| 214 | gsmtap-sapi sacch |
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| 215 | fn-advance 20 |
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| 216 | ms-power-loop -10 |
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| 217 | timing-advance-loop |
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| 218 | trx 0 |
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| 219 | 8 | ipse | rxgain 12 |
| 220 | 1 | power 0 |
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| 221 | trx 1 |
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| 222 | 3 | rxgain 12 |
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| 223 | 1 | power 0 |
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| 224 | 11 | </code></pre> |
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| 225 | 1 | ||
| 226 | |||
| 227 | 11 | h4. BTS 1 |
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| 228 | |||
| 229 | |||
| 230 | <pre> |
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| 231 | 1 | bts 0 |
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| 232 | band GSM900 |
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| 233 | ipa unit-id 1802 0 |
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| 234 | oml remote-ip 172.30.1.10 |
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| 235 | rtp jitter-buffer 0 |
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| 236 | paging lifetime 0 |
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| 237 | gsmtap-sapi bcch |
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| 238 | gsmtap-sapi ccch |
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| 239 | gsmtap-sapi rach |
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| 240 | gsmtap-sapi agch |
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| 241 | gsmtap-sapi pch |
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| 242 | gsmtap-sapi sdcch |
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| 243 | gsmtap-sapi pacch |
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| 244 | gsmtap-sapi pdtch |
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| 245 | gsmtap-sapi sacch |
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| 246 | 7 | fn-advance 20 |
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| 247 | ms-power-loop -10 |
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| 248 | 1 | timing-advance-loop |
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| 249 | trx 0 |
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| 250 | rxgain 12 |
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| 251 | power 0 |
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| 252 | trx 1 |
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| 253 | rxgain 12 |
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| 254 | power 0 |
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| 255 | 11 | </code></pre> |
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| 256 | 1 | ||
| 257 | |||
| 258 | 11 | h4. [[OpenBSC]] NITB |
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| 259 | 1 | ||
| 260 | 11 | ||
| 261 | 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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| 262 | |||
| 263 | <pre> |
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| 264 | 1 | ! |
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| 265 | ! OpenBSC (UNKNOWN) configuration saved from vty |
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| 266 | !! |
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| 267 | password foo |
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| 268 | ! |
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| 269 | line vty |
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| 270 | no login |
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| 271 | ! |
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| 272 | e1_input |
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| 273 | e1_line 0 driver ipa |
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| 274 | e1_line 0 port 0 |
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| 275 | no e1_line 0 keepalive |
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| 276 | network |
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| 277 | network country code 1 |
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| 278 | mobile network code 1 |
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| 279 | short name Osmocom |
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| 280 | long name Osmocom |
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| 281 | auth policy accept-all |
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| 282 | location updating reject cause 13 |
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| 283 | encryption a5 0 |
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| 284 | neci 1 |
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| 285 | paging any use tch 0 |
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| 286 | rrlp mode none |
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| 287 | mm info 1 |
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| 288 | handover 1 |
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| 289 | handover window rxlev averaging 10 |
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| 290 | handover window rxqual averaging 1 |
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| 291 | handover window rxlev neighbor averaging 10 |
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| 292 | handover power budget interval 6 |
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| 293 | handover power budget hysteresis 3 |
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| 294 | handover maximum distance 9999 |
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| 295 | timer t3101 10 |
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| 296 | timer t3103 0 |
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| 297 | timer t3105 0 |
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| 298 | timer t3107 0 |
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| 299 | timer t3109 4 |
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| 300 | timer t3111 0 |
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| 301 | timer t3113 60 |
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| 302 | timer t3115 0 |
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| 303 | timer t3117 0 |
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| 304 | timer t3119 0 |
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| 305 | timer t3122 10 |
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| 306 | timer t3141 0 |
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| 307 | dtx-used 0 |
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| 308 | subscriber-keep-in-ram 0 |
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| 309 | bts 0 |
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| 310 | type sysmobts |
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| 311 | band GSM900 |
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| 312 | cell_identity 0 |
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| 313 | location_area_code 1 |
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| 314 | base_station_id_code 63 |
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| 315 | ms max power 15 |
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| 316 | cell reselection hysteresis 4 |
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| 317 | rxlev access min 0 |
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| 318 | periodic location update 30 |
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| 319 | radio-link-timeout 32 |
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| 320 | channel allocator ascending |
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| 321 | rach tx integer 9 |
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| 322 | rach max transmission 7 |
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| 323 | channel-descrption attach 1 |
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| 324 | channel-descrption bs-pa-mfrms 5 |
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| 325 | channel-descrption bs-ag-blks-res 1 |
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| 326 | ip.access unit_id 1801 0 |
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| 327 | oml ip.access stream_id 255 line 0 |
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| 328 | neighbor-list mode automatic |
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| 329 | gprs mode none |
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| 330 | no force-combined-si |
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| 331 | trx 0 |
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| 332 | rf_locked 0 |
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| 333 | arfcn 74 |
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| 334 | nominal power 23 |
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| 335 | max_power_red 0 |
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| 336 | rsl e1 tei 0 |
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| 337 | timeslot 0 |
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| 338 | phys_chan_config CCCH+SDCCH4 |
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| 339 | hopping enabled 0 |
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| 340 | timeslot 1 |
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| 341 | phys_chan_config SDCCH8 |
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| 342 | hopping enabled 0 |
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| 343 | timeslot 2 |
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| 344 | phys_chan_config TCH/F |
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| 345 | hopping enabled 0 |
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| 346 | timeslot 3 |
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| 347 | phys_chan_config TCH/F |
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| 348 | hopping enabled 0 |
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| 349 | timeslot 4 |
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| 350 | phys_chan_config TCH/F |
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| 351 | hopping enabled 0 |
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| 352 | timeslot 5 |
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| 353 | phys_chan_config TCH/F |
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| 354 | hopping enabled 0 |
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| 355 | timeslot 6 |
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| 356 | phys_chan_config TCH/F |
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| 357 | hopping enabled 0 |
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| 358 | timeslot 7 |
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| 359 | phys_chan_config TCH/F |
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| 360 | hopping enabled 0 |
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| 361 | trx 1 |
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| 362 | rf_locked 0 |
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| 363 | arfcn 84 |
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| 364 | nominal power 23 |
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| 365 | max_power_red 0 |
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| 366 | rsl e1 tei 0 |
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| 367 | timeslot 0 |
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| 368 | phys_chan_config TCH/F |
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| 369 | hopping enabled 0 |
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| 370 | timeslot 1 |
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| 371 | phys_chan_config TCH/F |
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| 372 | hopping enabled 0 |
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| 373 | timeslot 2 |
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| 374 | phys_chan_config TCH/F |
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| 375 | hopping enabled 0 |
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| 376 | timeslot 3 |
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| 377 | phys_chan_config TCH/F |
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| 378 | hopping enabled 0 |
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| 379 | timeslot 4 |
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| 380 | phys_chan_config TCH/F |
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| 381 | hopping enabled 0 |
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| 382 | timeslot 5 |
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| 383 | phys_chan_config TCH/F |
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| 384 | hopping enabled 0 |
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| 385 | timeslot 6 |
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| 386 | phys_chan_config TCH/F |
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| 387 | hopping enabled 0 |
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| 388 | timeslot 7 |
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| 389 | phys_chan_config TCH/F |
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| 390 | hopping enabled 0 |
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| 391 | bts 1 |
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| 392 | type sysmobts |
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| 393 | band GSM900 |
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| 394 | cell_identity 0 |
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| 395 | location_area_code 1 |
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| 396 | base_station_id_code 62 |
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| 397 | ms max power 15 |
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| 398 | cell reselection hysteresis 4 |
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| 399 | rxlev access min 0 |
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| 400 | periodic location update 30 |
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| 401 | radio-link-timeout 32 |
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| 402 | channel allocator ascending |
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| 403 | rach tx integer 9 |
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| 404 | rach max transmission 7 |
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| 405 | channel-descrption attach 1 |
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| 406 | channel-descrption bs-pa-mfrms 5 |
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| 407 | channel-descrption bs-ag-blks-res 1 |
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| 408 | ip.access unit_id 1802 0 |
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| 409 | oml ip.access stream_id 255 line 0 |
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| 410 | neighbor-list mode automatic |
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| 411 | gprs mode none |
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| 412 | no force-combined-si |
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| 413 | trx 0 |
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| 414 | rf_locked 0 |
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| 415 | arfcn 111 |
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| 416 | nominal power 23 |
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| 417 | max_power_red 0 |
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| 418 | rsl e1 tei 0 |
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| 419 | timeslot 0 |
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| 420 | phys_chan_config CCCH+SDCCH4 |
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| 421 | hopping enabled 0 |
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| 422 | timeslot 1 |
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| 423 | phys_chan_config SDCCH8 |
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| 424 | hopping enabled 0 |
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| 425 | timeslot 2 |
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| 426 | phys_chan_config TCH/F |
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| 427 | hopping enabled 0 |
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| 428 | timeslot 3 |
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| 429 | phys_chan_config TCH/F |
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| 430 | hopping enabled 0 |
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| 431 | timeslot 4 |
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| 432 | phys_chan_config TCH/F |
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| 433 | hopping enabled 0 |
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| 434 | timeslot 5 |
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| 435 | phys_chan_config TCH/F |
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| 436 | hopping enabled 0 |
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| 437 | timeslot 6 |
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| 438 | phys_chan_config TCH/F |
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| 439 | hopping enabled 0 |
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| 440 | timeslot 7 |
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| 441 | phys_chan_config TCH/F |
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| 442 | hopping enabled 0 |
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| 443 | trx 1 |
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| 444 | rf_locked 0 |
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| 445 | 2 | arfcn 122 |
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| 446 | 1 | nominal power 23 |
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| 447 | max_power_red 0 |
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| 448 | rsl e1 tei 0 |
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| 449 | timeslot 0 |
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| 450 | phys_chan_config TCH/F |
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| 451 | hopping enabled 0 |
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| 452 | timeslot 1 |
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| 453 | phys_chan_config TCH/F |
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| 454 | hopping enabled 0 |
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| 455 | timeslot 2 |
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| 456 | phys_chan_config TCH/F |
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| 457 | hopping enabled 0 |
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| 458 | timeslot 3 |
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| 459 | phys_chan_config TCH/F |
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| 460 | hopping enabled 0 |
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| 461 | timeslot 4 |
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| 462 | phys_chan_config TCH/F |
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| 463 | hopping enabled 0 |
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| 464 | timeslot 5 |
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| 465 | phys_chan_config TCH/F |
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| 466 | hopping enabled 0 |
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| 467 | timeslot 6 |
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| 468 | phys_chan_config TCH/F |
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| 469 | hopping enabled 0 |
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| 470 | timeslot 7 |
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| 471 | phys_chan_config TCH/F |
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| 472 | hopping enabled 0 |
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| 473 | 11 | </code></pre> |
