Gsm (Part 2)

Traffic/Signaling

Traffic/Signaling

The network can carry two types of information: Traffic: it concerns all the «user to user»

information. It can be voice as well as data. Signaling: the network also requires to

carry information for its own working. Their purposes are numerous: traffic data routing, maintenance, security... These data are usually not visible from user’s point of view.

Teleservices

Telephony Emergency Call Short Message Cell Broadcast Short Message Service Fax User's Data Call Features Voice Messaging

Teleservices

Teleservices Teleservices cover regular telephony, emergency

calls, voice messaging, and short messages handling.

The most important service provided by GSM users is telephony which enables bi-directional speech calls to be placed between GSM users and any telephone subscriber who is reachable through the general telephony network.

Fixed telephone subscribers worldwide as well as mobile network subscribers or subscribers of specific networks connected to a public telephone network can be reached.

Before either Mobile Originated or Mobile Terminated calls can be established, the mobile telephone must be switched on and registered into the system.

Teleservices

Teleservices To place an emergency call enter 112 followed by

SEND. Additional means to place such call are also allowed by a dedicated button.

The Mobile Telephone supports the initiation of an emergency call without a SIM present in it, regardless of the call being accepted or not by the network.

Note that calls to national emergency services may be standard for the country of the serving GSM network (number 17 to call the police in France, number 911 to make an emergency call in U.S.A.).

However, with the exception of code "112", these are not treated within the GSM network as "teleservice emergency call" and would require a valid IMSI.

Teleservices

Teleservices The cell broadcast enables an Information Provider to submit short

messages for broadcasting to a specified area within the GSM network.

The cell broadcast service has the following features: The cell broadcast message is sent (on control channels) in a limited

area, defined by the originator of the message, by agreement with the GSM Operator.

The mobile telephone only receive the broadcast message in idle mode. The short message function running in the mobile is able not to store

broadcast messages which are not wanted or which have already been received.

The mobile telephone does not send acknowledgment. The GSM network continuously sends cell broadcast messages so that

all such messages are sent in turn, an then repeated. On the other hand, the cycle time is short enough for important messages to be received by travelers (subscribers) moving through a group of cells.

The maximum length of each cell broadcast message will be 93 characters and GSM specifications allows up to 15 of these 93 character messages treated as segment of a longer message.

Teleservices

Teleservices Short Message Service (SMS) allows the point to

point transmission of a short message to/from MS, using their IMSI.

A short message is an alphanumeric string that can be up to 160 characters long.

Two different types of short message are defined: Short message MT/PP (Mobile Terminated / Point to Point), Short message MO/PP (Mobile Originated / Point to Point).

Point to point messages may be sent or received when the MS is engaged on a call (voice or data), or in idle mode. However, messages which overlap the boundary of such a call, or during a handover, may be lost, in which case they will be sent again.

Teleservices

Teleservices Fax transmissions are possible via a PLMN

only with a Fax-group3 (14.4 kbps). Two modes are available:

Manual mode allows to switch alternatively from voice transmission to fax transmission,

Automatic mode allows to send and receive a fax without any human intervention;

However, voice transmission is impossible in this mode.

Teleservices

Teleservices

Connections can be made with a suitable data/fax kit adaptation either to other Mobile Station or to other data users on circuit-switched (PSTN).

In the case of making a Fax-call to a PSTN subscriber, the GSM network automatically selects the suitable modem for the link to the similar modem at the remote end.

Teleservices

Teleservices Another service derived from telephony is

voice messaging. Many operators offer it as a basic feature.

It enables a voice message to be stored for later retrieval by the mobile recipient, either because he was not reachable at time of the call or because the calling party choose to access the voice mailbox of the GSM subscriber directly.

Supplementary Services

Line Identification Call Transfer and Call

Forwarding Waiting / Hold and Multi Party Call Barring Call Completion (CCBS) Advice of Charge


Calling line identification presentation (CLIP) provides the ability to indicate the number of the calling party with possible additional address information to the called party. This identity is provided to the called subscriber before answering, thus enabling him to make the decision of whether to take the call or not.

Calling line identification restriction (CLIR) enables the calling party not to send any address information to the called party.

Connected line identification restriction (CoLR) enables the called party not to send its phone number to the calling party.

Calling Name Presentation (CNAP) provides the calling party name instead of the ISDN number. However, this service is not yet specified by GSM recommendations.


Call forwarding unconditional (CFU) allows a called mobile subscriber to have the network send all incoming calls, which are addressed to the called mobile subscriber’s directory number, to another directory number.

Call forwarding on mobile subscriber busy (CFB): allows a called mobile subscriber to have the network send the incoming calls, which are addressed to the called mobile subscriber’s directory number and which meet mobile subscriber busy, definition to another directory number.

Call forwarding on no reply (CFNRy) allows an called mobile subscriber to have the network send the incoming calls, which are addressed to the subscriber’s directory number and which meet no reply, to another directory number.

Call forwarding on MS not reachable (CFNRc) provides for a mobile subscriber to have the network send all incoming calls, which are addressed to the called mobile directory number and meet the not reachable definition, to another directory number.


Call waiting (CW): provides a mobile subscriber with the possibility of being notified of an incoming call while his mobile telephone is in the busy state. Subsequently, the user can either answer, reject, or ignore the incoming call. Both the call waiting and call hold (described further) options are the same as those offered by the PSTN.

Call Hold (HOLD): allows a served mobile subscriber to interrupt communication on an existing call and then subsequently, if desired, to reestablish communication.

Multi party service (MPTY): This Supplementary Service provides a mobile subscriber with the

ability to have a multi-connection call, in other words a simultaneous communication with more than one party.

A precondition for the multi-party service is that the served mobile subscriber is in control of one active call and one call on hold, both calls having been answered. In this situation the served mobile subscriber can request the network to begin the multiParty service.

Once a multiParty call is active, remote parties may be added, disconnected or separated (i.e.. removed from the multiParty call but remain connected to the served mobile subscriber).

The maximum number of remote parties is 5.


Barring of all outgoing call (BAOC): makes it possible for a mobile subscriber to prevent all outgoing calls.

BOIC except those directed to the home PLMN country (BOIC-exHC)

Barring of all incoming international (BAIC). Barring of all incoming calls when roaming

outside the home GSM network country (BIC-Roam): makes it possible for a mobile subscriber to prevent all incoming calls that would otherwise be terminated at his directory number. This only applies to the case when the mobile subscriber roams outside his home GSM network.


Completion of calls to busy subscribers (CCBS): allows a calling mobile subscriber who encounters a busy called subscriber to be notified by the system operator when the busy called subscriber becomes free and have the operator re-initiate the call if the caller so desires.

This feature has to be supported by both the originating and the terminating networks.


Advice of charge Information (AoCI): informs the user of the real-time information on progress of the cost of the call.

Advice of charge Charging (AoCC): the mobile may be a money-operated mobile telephone or a standard mobile station that can display the charging information and can accept either coins or charge a credit-card.

Intelligent Network Services

Main IN Services: Personal Number Virtual Private Network (VPN) Sponsored Cell & Call Prepaid Calling Location Inquiry Geo Zone

IN and CAMEL

Intelligent Network Services

The aim of the CAMEL (Customized Application for Mobile network Enhanced Logic) is to provide GSM network operators with the ability to create specific services in their home network, and export these services to their subscribers when roaming outside the home network.

CAMEL introduces the ability to provide location dependent IN type of services to mobiles subscribers.

IN and CAMEL

Intelligent Network (IN) The Intelligent Network or IN is a switching network concept. Its idea is to make GSM services system an open system; that is

to say new services modules can always be added on the previous system without changing its architecture.

Basic call processing is performed by the switch and when it recognizes that a call requires an IN service, this service processing is provided by another entity, located either in the same site or in a remote site.

This concept allows to implement numerous new services such as: Personal Number: gives the GSM subscribers more control over

incoming calls, Virtual Private Network: a set of corporate services that enables

similar functions to those of private network, among a group of GSM subscribers,

Sponsored Cell and Call: allows a third party, as sponsor, to play announcement at the beginning of the call,

Prepaid Calling: allows subscriber to pay in advance for the calls they will make.

Customized Application for Mobile network Enhanced Logic (CAMEL)

To communicate between Intelligent Network platforms, GSM specifications define CAMEL (Customized Application for Mobile network Enhanced Logic).

The aim of the CAMEL is to provide network operators with the ability to create specific services in their home network, and export these services to their subscribers when roaming outside the home network.

CAMEL introduces the ability to provide location dependent IN type of services to mobiles subscribers: Location Enquiry and Geo Zone.

IN Services: Virtual Private Network


Virtual Private Network (VPN) is a set of corporate services that enables private network like features among a group of GSM subscribers and wireline users; thus, corporations can distribute GSM phones to their employees, providing them with many of the services that they use on their existing corporate network: Private Numbering Plan: subscribers can reach all

members of the corporate private network, GSM as well as wireline, by dialing their usual internal number instead of the longer, harder to remember, public number.

Off Net Calling: subscribers are allowed to call public numbers that are outside the corporate private network.

Forced On Net Calling: when a subscriber makes a call to a member of the corporate private network using their public number (he must also be provisioned with Off Net Calling), the feature recognizes the call as a private call and treats it as such (appropriate billing, etc.).


White (/Black) List Screening: subscribers with White (/ Black) List, can only (/ can not) place calls to numbers listed on it.

Geographic Routing: specific numbers can be configured to route calls differently depending on the location of the caller.

Time Screening (/ Routing): some specific numbers can be configured to restrict access (/ to route calls differently) depending on the time of the day, day of the week, day of the year or whether the day is a statutory holiday.

Privileged Routing: specific numbers can be configured to route calls differently depending on the identity of the caller.

Closer user group (CUG): provides the possibility for a group of subscribers, connected to the GSM network and or to the PSTN/ISDN, to communicate only among themselves or receive external calls; emergency calls still are available.

IN Services: Prepaid Calling


Prepaid Calling enables subscribers to control their phone call expenditure, by deciding how much to spend and limiting themselves to that amount if required.

Subscribers pay in advance for their calls and get their calls released when the balance becomes null; thus, subscribers get a cost-control (useful for rental companies, hotels, special events, parents wanting to give mobiles to their children).

With Prepaid Calling, subscribers are able to: Make and receive calls (service is totally transparent to the

subscriber during normal use), Be notified of a low balance or a pending expiry date (if the

threshold is reached, the subscriber can be notified by warning tones before the call is taken down),

Use Voice Mail, Query the status of their account at any time from any phone

and recharge their account.


The subscriber can also be informed of his account balance and of the cost of his last call, at the end of each call, via a short message.

Additionally, the Operator can apply different rates to calls and manage the life of prepaid subscriptions.

Nortel’s prepaid solution currently supports all major recharging options, for increased service usage and enhanced customer satisfaction: Automatically, by vouchers (e.g. scratch card), Automatically, by credit card, Manually (through Customer Services), by any

means of payment.

IN Services: Sponsored Cell & Call

IN Services: Sponsored Cell & Call

Sponsored Cell & Call allows a third party (the sponsor) to play a promotional announcement at the beginning of a call and for this service, pays for part of the ongoing call.

The main features of Sponsored Cell & Call are: Choice to sponsor the call & choice of sponsor based on one or more

of the following: The calling party location, The calling party profile (age ...), Time of day, day of week, Destination (emergency, freephone ...).

Sponsor can change his announcement on the phone. User can specify certain destinations as not sponsored. User can have the choice of having his call sponsored or not. User can cut through the announcement, but the call is not

sponsored. User can be prevented from cutting through the announcement.

IN Services: Location Inquiry

IN Services: Location Inquiry

Location Inquiry provides GSM subscribers with information on where to locate useful services in their current area.

It enables easy connection to any service they are interested in and wish to talk to.

However, while GSM subscribers are out of the office or away from home, they do not have access to this information easily e.g. yellow pages, guides.

Most of time, they may be even more reliant on this information because they often are in a foreign environment, e.g. in another part of town or out of town.

The Location Inquiry service brings in a third party known as the “Advertiser” who seeks to sell their products/services using the operator’s network.

Location Inquiry may also list services such as hospitals, doctors, pharmacies, etc. and be promoted as a personal security service.

The main features of Location Inquiry are: Location dependent information based on subscriber’s cell, Possible customization of the announcement by the advertiser (special offer of the

day...).

IN Services: Geo Zone

IN Services: Geo Zone The main features of the outgoing side of

Geo Zone are: Zone dependent tariffing of outgoing calls:

up to 4 zones per subscriber, each zone has its own tariff,

Information on the current zone available to the subscriber via: announcement or tones at the beginning of the

call, optionally by a display on the mobile (in which

case it must support it, which means specific development on the handset).


The main features of the incoming side of Geo Zone are: Routing of incoming calls according to the

subscriber’s location: if the subscriber is in his Geo Zone, the call is routed to his

mobile handset, thus he does not have to pay anything, if the subscriber is out of his Geo Zone, the call can be either

routed to his voice-mail, or to his mobile handset; in the last case the subscriber pays for the forwarding leg,

Information on the current zone available to the subscriber, when receiving a call via: announcement or tones before the call is connected.

Channels

Channel can be Signaling or for Traffic

These are of two types Downlink Uplink

TCH/F - Traffic Channel Full Rate

The Full Rate channel in GSM is identified as a 22.8Kbps gross bit rate channel. This channel is bidirectional enabling the transfer of speech or circuit switched data. Signaling associated with this traffic channel will be carried on either the SACCH (Slow Associated Control Channel) or the FACCH (Fast Associated Control Channel). The latest releases of GSM include EDGE (Enhanced Data rates for Global Evolution) functionality which increases the gross rate.

FACCH - Fast Associated Control Channel

The Fast Associated Control Channel appears in place of the traffic channel when lengthy signaling is required between a GSM mobile and the network while the mobile is in call. The channel is indicated by use of the stealing flags in the normal burst. Typical signaling where this may be employed is during cell handover.

SACCH - Slow Associated Control Channel

A GSM signalling channel that provides a relatively slow signalling connection. The SACCH is associated with either a traffic or dedicated channel. The SACCH can also be used to transfer SMS (Short Message Service) messages if associated with a traffic channel.

BCCH - Broadcast Control Channel

This downlink channel contains specific parameters needed by a mobile in order that it can identify the network and gain access to it. Typical information includes the LAC (Location Area Code) and RAC (Routing Area Code), the MNC (Mobile Network Code) and BA (BCCH Allocation) list.

ACCH - Associated Control Channel

The GSM signalling channels associated with a user’s traffic channel or dedicated signalling channel. Two ACCH are defined for GSM Circuit Switched operation. These are SACCH (Slow Associated Control Channel) and FACCH (Fast Associated Control Channel). In GPRS packet operation, a ACCH is allocated in conjunction with a PDTCH (Packet Data Traffic Channel) and is termed a PACCH (Packet Associated Control Channel).

DCCH - Dedicated Control Channel (GSM)

These channels are used for signaling between the network and the mobile. They comprise of the SDCCH (Standalone Dedicated Control Channel), the SACCH (Slow Associated Control Channel) and the FACCH (Fast Associated Control Channel).

DCCH - Dedicated Control Channel (UMTS)

A UMTS (Universal Mobile Telecommunication System) point to point bidirectional channel that transmits dedicated control information between a UE (User Equipment) and the network. This channel is established through the RRC (Radio Resource Control) connection setup procedure.

AGCH - Access Grant Channel

The Access Grant Channel is used to assign resources to a user requesting access to the network. These resources will include the dedicated channel to be used along with timing advance information.

PCH - Paging Channel (Generic)

The Paging Channel is used to alert a mobile that there is a call or text message waiting. The alert is broadcast from all cells within a given area.

PACCH - Packet Associated Control Channel

The Packet Associated Control Channel conveys signalling information related to a given GPRS mobile such as acknowledgements and power control information. The PACCH also carries resource assignment and reassignment messages.

SCH - Synchronization Channel

The Synchronization Channel is a downlink signal channel used for cell search and conveying of synchronization information.

Gsm (Part 2)

Technology

Transcript of Gsm (Part 2)