Multi-BTS with handover » History » Version 11
Anonymous, 02/19/2016 10:48 PM
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 | <pre> |
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24 | <code class="graphviz"> |
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25 | 1 | digraph G { |
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26 | rankdir = LR; |
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27 | BSC -> BTS0 [ label = "A-bis" dir=both ]; |
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28 | BSC -> BTS1 [ label = "A-bis" dir=both ]; |
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29 | BSC [ shape = square label = "BSC\n172.30.1.10" ]; |
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30 | BTS0 [ shape = square label = "BTS 0\n172.30.1.11" ]; |
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31 | BTS1 [ shape = square label = "BTS 1\n172.30.1.12" ]; |
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32 | } |
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33 | 11 | </code></pre> |
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34 | 8 | ipse | |
35 | 1 | ||
36 | 11 | h3. BTS configuration |
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37 | 1 | ||
38 | |||
39 | 11 | There are three [[OsmoBTS]] parameters in particular which must be correctly configured: |
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40 | |||
41 | * *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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42 | * *band* - the band in which the BTS will operate |
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43 | * *ipa unit-id* - each BTS must use a unique value |
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44 | * *oml remote-ip* - this is the BSC IP address |
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45 | |||
46 | 3 | The example configuration that follows is for two BTS both on the GSM900 band. |
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47 | |||
48 | |||
49 | 11 | h4. BTS 0 |
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50 | |||
51 | |||
52 | 1 | Find the aforementioned parameters and ensure that they are correctly set. |
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53 | |||
54 | 11 | <pre> |
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55 | 1 | bts 0 |
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56 | band GSM900 |
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57 | ipa unit-id 1801 0 |
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58 | oml remote-ip 172.30.1.10 |
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59 | 3 | ... |
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60 | 11 | </code></pre> |
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61 | 3 | ||
62 | 1 | ||
63 | 11 | h4. BTS 1 |
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64 | 3 | ||
65 | 11 | ||
66 | Ensure that the second BTS has a different *ipa unit-id* configured from the first. |
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67 | |||
68 | <pre> |
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69 | 7 | bts 0 |
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70 | 3 | band GSM900 |
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71 | ipa unit-id 1802 0 |
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72 | oml remote-ip 172.30.1.10 |
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73 | ... |
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74 | 11 | </code></pre> |
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75 | 3 | ||
76 | 1 | ||
77 | 11 | h3. BSC configuration |
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78 | |||
79 | |||
80 | 3 | There are a number of BSC/NITB parameters that you must pay particular attention to: |
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81 | |||
82 | 11 | * *BTS _n* |
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83 | *** *band* - as configured in the BTS |
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84 | *** *base_station_id_code* - should be unique in location area |
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85 | *** *ip.access unit_id* - as configured in the BTS |
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86 | *** *trx _n_ |
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87 | ****** *arfcn* - this must be frequencies that you have a licence for and unique across all neighbouring BTS |
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88 | * *neighbor-list mode automatic* |
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89 | 3 | ||
90 | 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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91 | 3 | ||
92 | 11 | <pre> |
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93 | 10 | bts 0 |
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94 | 3 | ... |
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95 | band GSM900 |
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96 | 1 | ... |
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97 | base_station_id_code 63 |
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98 | 3 | ... |
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99 | 1 | ip.access unit_id 1801 0 |
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100 | ... |
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101 | neighbor-list mode automatic |
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102 | ... |
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103 | trx 0 |
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104 | rf_locked 0 |
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105 | arfcn 74 |
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106 | ... |
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107 | trx 1 |
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108 | rf_locked 0 |
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109 | arfcn 84 |
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110 | ... |
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111 | 11 | </code></pre> |
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112 | 3 | ||
113 | 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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114 | 3 | ||
115 | 11 | <pre> |
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116 | 3 | bts 1 |
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117 | ... |
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118 | band GSM900 |
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119 | 4 | ipse | ... |
120 | 3 | base_station_id_code 62 |
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121 | 1 | ... |
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122 | 3 | ip.access unit_id 1802 0 |
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123 | ... |
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124 | neighbor-list mode automatic |
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125 | 1 | ... |
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126 | trx 0 |
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127 | rf_locked 0 |
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128 | 3 | arfcn 111 |
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129 | ... |
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130 | trx 1 |
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131 | rf_locked 0 |
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132 | 1 | arfcn 122 |
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133 | ... |
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134 | 11 | </code></pre> |
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135 | 3 | ||
136 | 11 | For details of all the configuration options please see the [[osmo-nitb_VTY|NITB VTY reference]]. |
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137 | 1 | ||
138 | |||
139 | 11 | h4. Handover |
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140 | |||
141 | |||
142 | 3 | The following parameters must also be configured in order to enable handover: |
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143 | |||
144 | 11 | * *handover 1* |
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145 | *** _Enable in-call handover between multiple BTS._ |
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146 | 3 | ||
147 | 11 | * *handover window rxlev averaging 10* |
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148 | *** _The receive level of the serving cell should be averaged over 10 SACCH frames._ |
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149 | 3 | ||
150 | 11 | * *handover window rxqual averaging 1* |
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151 | *** _The receive quality of the serving cell should be averaged over 1 SACCH frame._ |
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152 | 3 | ||
153 | 11 | * *handover window rxlev neighbor averaging 10* |
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154 | *** _The Rx Level of a neighbour cell should be averaged over 10 SACCH frames._ |
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155 | 3 | ||
156 | 11 | * *handover power budget interval 6* |
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157 | *** _Consider performing a power budget (Rx level) handover every 6 SACCH frames._ |
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158 | 3 | ||
159 | 11 | * *handover power budget hysteresis 3* |
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160 | *** _Set hysteresis (prevents continuous handover back and forth) to 3._ |
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161 | 3 | ||
162 | 11 | * *handover maximum distance 9999* |
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163 | *** _When the distance from the BTS is greater than 9999 attempt a distance handover._ |
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164 | 1 | ||
165 | 11 | These parameters must be set within the *network* section of the BSC/NITB configuration: |
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166 | 1 | ||
167 | 11 | <pre> |
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168 | 3 | network |
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169 | network country code 1 |
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170 | ... |
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171 | handover 1 |
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172 | 9 | ipse | handover window rxlev averaging 10 |
173 | handover window rxqual averaging 1 |
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174 | handover window rxlev neighbor averaging 10 |
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175 | handover power budget interval 6 |
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176 | handover power budget hysteresis 3 |
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177 | handover maximum distance 9999 |
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178 | 11 | </code></pre> |
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179 | 3 | ||
180 | 7 | Values can be tuned to modify the behaviour of handover. |
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181 | 3 | ||
182 | |||
183 | 11 | h3. Testing handover |
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184 | |||
185 | |||
186 | 3 | To test handover you have two options: |
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187 | |||
188 | 1. Physically move a phone to trigger handover decision. |
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189 | 1 | 2. Use "subscriber ID handover BTS_NR" command in the NITB VTY to force handover. |
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190 | |||
191 | 11 | h3. Complete configurations |
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192 | |||
193 | |||
194 | 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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195 | |||
196 | |||
197 | 11 | h4. BTS 0 |
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198 | |||
199 | |||
200 | <pre> |
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201 | 1 | bts 0 |
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202 | band GSM900 |
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203 | ipa unit-id 1801 0 |
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204 | oml remote-ip 172.30.1.10 |
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205 | rtp jitter-buffer 0 |
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206 | paging lifetime 0 |
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207 | gsmtap-sapi bcch |
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208 | gsmtap-sapi ccch |
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209 | gsmtap-sapi rach |
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210 | gsmtap-sapi agch |
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211 | gsmtap-sapi pch |
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212 | gsmtap-sapi sdcch |
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213 | gsmtap-sapi pacch |
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214 | gsmtap-sapi pdtch |
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215 | gsmtap-sapi sacch |
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216 | fn-advance 20 |
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217 | ms-power-loop -10 |
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218 | timing-advance-loop |
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219 | trx 0 |
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220 | 8 | ipse | rxgain 12 |
221 | 1 | power 0 |
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222 | trx 1 |
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223 | 3 | rxgain 12 |
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224 | 1 | power 0 |
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225 | 11 | </code></pre> |
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226 | 1 | ||
227 | |||
228 | 11 | h4. BTS 1 |
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229 | |||
230 | |||
231 | <pre> |
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232 | 1 | bts 0 |
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233 | band GSM900 |
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234 | ipa unit-id 1802 0 |
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235 | oml remote-ip 172.30.1.10 |
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236 | rtp jitter-buffer 0 |
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237 | paging lifetime 0 |
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238 | gsmtap-sapi bcch |
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239 | gsmtap-sapi ccch |
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240 | gsmtap-sapi rach |
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241 | gsmtap-sapi agch |
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242 | gsmtap-sapi pch |
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243 | gsmtap-sapi sdcch |
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244 | gsmtap-sapi pacch |
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245 | gsmtap-sapi pdtch |
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246 | gsmtap-sapi sacch |
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247 | 7 | fn-advance 20 |
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248 | ms-power-loop -10 |
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249 | 1 | timing-advance-loop |
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250 | trx 0 |
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251 | rxgain 12 |
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252 | power 0 |
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253 | trx 1 |
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254 | rxgain 12 |
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255 | power 0 |
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256 | 11 | </code></pre> |
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257 | 1 | ||
258 | |||
259 | 11 | h4. [[OpenBSC]] NITB |
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260 | 1 | ||
261 | 11 | ||
262 | 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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263 | |||
264 | <pre> |
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265 | 1 | ! |
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266 | ! OpenBSC (UNKNOWN) configuration saved from vty |
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267 | !! |
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268 | password foo |
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269 | ! |
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270 | line vty |
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271 | no login |
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272 | ! |
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273 | e1_input |
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274 | e1_line 0 driver ipa |
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275 | e1_line 0 port 0 |
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276 | no e1_line 0 keepalive |
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277 | network |
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278 | network country code 1 |
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279 | mobile network code 1 |
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280 | short name Osmocom |
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281 | long name Osmocom |
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282 | auth policy accept-all |
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283 | location updating reject cause 13 |
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284 | encryption a5 0 |
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285 | neci 1 |
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286 | paging any use tch 0 |
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287 | rrlp mode none |
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288 | mm info 1 |
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289 | handover 1 |
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290 | handover window rxlev averaging 10 |
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291 | handover window rxqual averaging 1 |
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292 | handover window rxlev neighbor averaging 10 |
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293 | handover power budget interval 6 |
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294 | handover power budget hysteresis 3 |
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295 | handover maximum distance 9999 |
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296 | timer t3101 10 |
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297 | timer t3103 0 |
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298 | timer t3105 0 |
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299 | timer t3107 0 |
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300 | timer t3109 4 |
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301 | timer t3111 0 |
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302 | timer t3113 60 |
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303 | timer t3115 0 |
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304 | timer t3117 0 |
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305 | timer t3119 0 |
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306 | timer t3122 10 |
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307 | timer t3141 0 |
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308 | dtx-used 0 |
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309 | subscriber-keep-in-ram 0 |
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310 | bts 0 |
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311 | type sysmobts |
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312 | band GSM900 |
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313 | cell_identity 0 |
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314 | location_area_code 1 |
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315 | base_station_id_code 63 |
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316 | ms max power 15 |
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317 | cell reselection hysteresis 4 |
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318 | rxlev access min 0 |
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319 | periodic location update 30 |
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320 | radio-link-timeout 32 |
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321 | channel allocator ascending |
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322 | rach tx integer 9 |
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323 | rach max transmission 7 |
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324 | channel-descrption attach 1 |
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325 | channel-descrption bs-pa-mfrms 5 |
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326 | channel-descrption bs-ag-blks-res 1 |
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327 | ip.access unit_id 1801 0 |
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328 | oml ip.access stream_id 255 line 0 |
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329 | neighbor-list mode automatic |
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330 | gprs mode none |
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331 | no force-combined-si |
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332 | trx 0 |
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333 | rf_locked 0 |
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334 | arfcn 74 |
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335 | nominal power 23 |
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336 | max_power_red 0 |
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337 | rsl e1 tei 0 |
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338 | timeslot 0 |
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339 | phys_chan_config CCCH+SDCCH4 |
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340 | hopping enabled 0 |
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341 | timeslot 1 |
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342 | phys_chan_config SDCCH8 |
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343 | hopping enabled 0 |
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344 | timeslot 2 |
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345 | phys_chan_config TCH/F |
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346 | hopping enabled 0 |
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347 | timeslot 3 |
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348 | phys_chan_config TCH/F |
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349 | hopping enabled 0 |
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350 | timeslot 4 |
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351 | phys_chan_config TCH/F |
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352 | hopping enabled 0 |
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353 | timeslot 5 |
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354 | phys_chan_config TCH/F |
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355 | hopping enabled 0 |
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356 | timeslot 6 |
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357 | phys_chan_config TCH/F |
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358 | hopping enabled 0 |
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359 | timeslot 7 |
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360 | phys_chan_config TCH/F |
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361 | hopping enabled 0 |
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362 | trx 1 |
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363 | rf_locked 0 |
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364 | arfcn 84 |
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365 | nominal power 23 |
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366 | max_power_red 0 |
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367 | rsl e1 tei 0 |
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368 | timeslot 0 |
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369 | phys_chan_config TCH/F |
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370 | hopping enabled 0 |
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371 | timeslot 1 |
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372 | phys_chan_config TCH/F |
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373 | hopping enabled 0 |
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374 | timeslot 2 |
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375 | phys_chan_config TCH/F |
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376 | hopping enabled 0 |
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377 | timeslot 3 |
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378 | phys_chan_config TCH/F |
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379 | hopping enabled 0 |
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380 | timeslot 4 |
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381 | phys_chan_config TCH/F |
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382 | hopping enabled 0 |
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383 | timeslot 5 |
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384 | phys_chan_config TCH/F |
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385 | hopping enabled 0 |
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386 | timeslot 6 |
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387 | phys_chan_config TCH/F |
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388 | hopping enabled 0 |
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389 | timeslot 7 |
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390 | phys_chan_config TCH/F |
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391 | hopping enabled 0 |
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392 | bts 1 |
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393 | type sysmobts |
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394 | band GSM900 |
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395 | cell_identity 0 |
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396 | location_area_code 1 |
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397 | base_station_id_code 62 |
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398 | ms max power 15 |
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399 | cell reselection hysteresis 4 |
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400 | rxlev access min 0 |
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401 | periodic location update 30 |
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402 | radio-link-timeout 32 |
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403 | channel allocator ascending |
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404 | rach tx integer 9 |
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405 | rach max transmission 7 |
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406 | channel-descrption attach 1 |
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407 | channel-descrption bs-pa-mfrms 5 |
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408 | channel-descrption bs-ag-blks-res 1 |
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409 | ip.access unit_id 1802 0 |
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410 | oml ip.access stream_id 255 line 0 |
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411 | neighbor-list mode automatic |
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412 | gprs mode none |
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413 | no force-combined-si |
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414 | trx 0 |
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415 | rf_locked 0 |
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416 | arfcn 111 |
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417 | nominal power 23 |
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418 | max_power_red 0 |
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419 | rsl e1 tei 0 |
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420 | timeslot 0 |
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421 | phys_chan_config CCCH+SDCCH4 |
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422 | hopping enabled 0 |
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423 | timeslot 1 |
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424 | phys_chan_config SDCCH8 |
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425 | hopping enabled 0 |
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426 | timeslot 2 |
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427 | phys_chan_config TCH/F |
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428 | hopping enabled 0 |
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429 | timeslot 3 |
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430 | phys_chan_config TCH/F |
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431 | hopping enabled 0 |
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432 | timeslot 4 |
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433 | phys_chan_config TCH/F |
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434 | hopping enabled 0 |
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435 | timeslot 5 |
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436 | phys_chan_config TCH/F |
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437 | hopping enabled 0 |
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438 | timeslot 6 |
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439 | phys_chan_config TCH/F |
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440 | hopping enabled 0 |
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441 | timeslot 7 |
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442 | phys_chan_config TCH/F |
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443 | hopping enabled 0 |
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444 | trx 1 |
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445 | rf_locked 0 |
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446 | 2 | arfcn 122 |
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447 | 1 | nominal power 23 |
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448 | max_power_red 0 |
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449 | rsl e1 tei 0 |
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450 | timeslot 0 |
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451 | phys_chan_config TCH/F |
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452 | hopping enabled 0 |
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453 | timeslot 1 |
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454 | phys_chan_config TCH/F |
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455 | hopping enabled 0 |
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456 | timeslot 2 |
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457 | phys_chan_config TCH/F |
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458 | hopping enabled 0 |
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459 | timeslot 3 |
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460 | phys_chan_config TCH/F |
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461 | hopping enabled 0 |
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462 | timeslot 4 |
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463 | phys_chan_config TCH/F |
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464 | hopping enabled 0 |
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465 | timeslot 5 |
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466 | phys_chan_config TCH/F |
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467 | hopping enabled 0 |
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468 | timeslot 6 |
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469 | phys_chan_config TCH/F |
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470 | hopping enabled 0 |
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471 | timeslot 7 |
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472 | phys_chan_config TCH/F |
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473 | hopping enabled 0 |
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474 | 11 | </code></pre> |