140 lines
4.6 KiB
Plaintext
140 lines
4.6 KiB
Plaintext
[[net]]
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== OsmoNITB Core Network Subsystem
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The OsmoNITB Core Network is a minimalistic implementation of the
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classic MSC/VLR/HLR/AUC/SMSC components. None of the standardized core
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network protocols (such as SCCP/TCAP/MAP) are used, interfaces between
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VLR and HLR are simple function calls inside the same software package.
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OsmoNITB can thus provide autonomous voice and SMS services to its
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coverage area, but it cannot provide roaming interfaces to classic GSM
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operators. To support this configuration, it is suggested to use the
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OsmoBSC variant of OpenBSC and interface it with a conventional MSC
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using A-over-IP protocol.
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If you have classic GSM network/operator background, many of the
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concepts used in OsmoNITB will appear foreign to you, as they are very
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unlike the conventional GSM networks that you have worked with.
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=== Configuring the Core Network
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Like everything else, the core network related parameters are configured
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using the VTY. The respective parameters are underneath the
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`network` config node.
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You can get to that node by issuing the following commands:
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.Entering the config network node
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----
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OpenBSC> enable
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OpenBSC# configure terminal
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OpenBSC(config)# network
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OpenBSC(config-net)#
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----
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A full reference to them can be found in the _OsmoNITB VTY reference
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manual_ <<vty-ref-osmonitb>>. This section will only introduce the most
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commonly used settings in detail.
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[TIP]
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====
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You can always use the `list` VTY command to get a list of all possible
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commands at the current node.
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====
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=== Configuring the MCC/MNC
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The key identities of every GSM PLMN is the MCC and MNC. They are
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identical over the entire network. In most cases, the MCC/MNC will be
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allocated to the operator by the respective local regulatory authority.
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For example, to set the MCC/MNC of 262-89, you may enter:
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.Configuring the MCC/MNC
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----
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OpenBSC(config-net)# network country code 262
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OpenBSC(config-net)# mobile network code 89
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----
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=== Configuring MM INFO
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The __MM INFO__ procedure can be used after a successful __LOCATION
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UPDATE__ in order to transmit the human-readable network name as well as
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local time zone information to the MS.
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By default, MM INFO is not active. You can activate it, and set its
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configuration using the VTY. An example is provided below.
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.Configuring MM INFO
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----
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OpenBSC(config-net)# mm info 1
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OpenBSC(config-net)# short name OpenBSC
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OpenBSC(config-net)# long name OpenBSC
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----
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[NOTE]
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====
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Not all phone support the MM INFO procedure. Unless they already are
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factory-programmed to contain the name for your MCC/MNC, then they will
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likely only provide a numeric display of the network name, such as
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__262-89__ or with the country code transformed into a letter, such as
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__D 89__.
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====
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The time information transmitted is determined by the local system time
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of the operating system on which OsmoNITB is running. As BTSs attached
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to one OsmoNITB can reside in different time zones, it is possible to
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use the `timezone` command at each BTS node to set different time
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zone offsets in hours and quarter hours.
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=== Setting the NECI bit
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NECI (New Establishment Cause Indication) is an optional change of the
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definition for establishment cause in the RACH burst. Among other
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things, in a network with NECI, a MS can explicitly indicate its TCH/H
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capability while asking for a dedicated radio channel.
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It is strongly recommended to use NECI. You can do so by issuing the following command:
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.Enabling NECI
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----
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OpenBSC(config-net)# neci 1
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----
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=== Configuring Handover
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As opposed to cell re-selection in idle mode, handover refers to the
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explicit transfer of a MS dedicated channel from one radio channel to
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another. This typically happens due to a MS moving from one cell to
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another while in an active call.
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OsmoNITB has a number of hand-over related parameters by which the
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hand-over algorithm can be tuned. Logically, those settings are settings
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of the BSC component, but for historic reasons, they are also configured
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under the __network__ VTY node.
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.Configuring Handover
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----
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OpenBSC(config-net)# handover 1
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OpenBSC(config-net)# handover window rxlev averaging 10
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OpenBSC(config-net)# handover window rxqual averaging 1
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OpenBSC(config-net)# handover window rxlev neighbor averaging 10
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OpenBSC(config-net)# handover power budget interval 6
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OpenBSC(config-net)# handover power budget hysteresis 3
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OpenBSC(config-net)# handover maximum distance 9999
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----
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[NOTE]
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====
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If you are receiving the following error message:
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----
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OpenBSC(config-net)# handover 1
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% Cannot enable handover unless RTP Proxy mode is enabled by using the -P command line option
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----
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then you should do as indicated and make sure to start your `osmo-nitb` process using
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the `-P` command line option.
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====
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