Basic Overview of GSM Communications

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watt to decibel conversions - deccreasing by 10's

/10 --- -10 dBm 1 watt --- 30 dBm 0.1 watt --- 20 dBm 0.01 watt --- 10 dBm

watt to decibel conversions - (halving)

/2 --- -3 dB's 1 watt --- 30 dBm 0.5 watt --- 27 dBm 0.025 watt --- 24 dBm 0.0125 watt --- 23 dBm 0.0075 watt --- 20 dBm

common location update reject/ cause codes

000- no error 002- IMSI unknown in HLR 003- illegal MS 004- IMSI unknown in VLR 005- IMEI not accepted 006- illegal ME 011- PLMN not allowed 012- LA not allowed 013- romaing not allowed in LA

Composition of IMEI before 2003

6 digits (TAC), 2 digits (FAC), 6 digits (SN), 1 digit (CD)

A TDMA frame in GSM contains how many timeslots

8

GSM frequency channels contain how many TDMA conversation channels

8 at 200 kHz bandwidth each

Composition of IMEI after 2003

8 digits (TAC), 6 digits (SN), 1 digit (CN)

common GSM bands

CONUS- 850 MHz and 1900 MHz Europe and OCONUS- 900 MHz and 1800 MHz Rural areas- 450 MHz occasionallly

Who developed GSM?

ETSI

A GSM network can immediately decide whether or not to accept calls by means of what

IMEI

4G - broadband data

LTE/ LTE-A WiMAX

1xRTT

Single-Carrier Radio Transmission Technology

What does a MSISDN consist of

a 1-3 digit country code (CC), a 3 digit national designation code (NDC), and a subscriber number (SN)

What does a PLMN consist of

a 3 digit mobile country code (MCC) and a 2-3 digit mobile network code

What does a cell global identification (CGI) consist of

a 3 digit mobile country code (MCC), a 2-3 digit mobile network code (MNC), a location area code (LAC) of up to 5 digits, and a cell identity (CI) of up to 5 digits

What does a location area identity (LAI) consist of

a 3 digit mobile country code (MCC), a 2-3 digit mobile network code (MNC), and a location area code (LAC) of up to 5 digits

As of April 1, 2004, the IMEI no longer consists of what

a 6 digit Type Approval Code (TAC) and 2 digit Final Assembly Code (FAC)

barred location areas (LA's) and access control

a MS cannot select in idle mode any broadcast control channel (BCCH) that is restricted by the CELL_BAR_ACCESS PARAMETER; network operators can restrict access in certain areas; MS cannot register when CELL_BAR_ACCESS is set to 1

logical channels

a burst of digital information, both of voice or data traffic mapped on a 200 kHz channel; made to fit into one of the GSM TDMA timeslots

What was GSM in the past?

a digital, circuit-switched network which was optimized for full duplex voice telephony

What does a cell identity (CI) consist of

a fixed length of two octets and can be coded using a full hexadecimal

BA list

a list of allowable absolute radio frequency channel numbers (ARFCN) the MS can use for reselecction if one were to become stronger; six strongest channelson BA list will be determined by the handset and will be the neighbor

location area (LA)

a location area code (LAC) can be comprised of hundreds of base tranceiver stations (BTS's), serviced by a single mobile switching center (MSC)/ visitor location register (VLR) and controlled by a single base station controller

What does a BSIC consist of

a network color code (NCC) - (0-7) - consists of 3 bits which are used to differentiate between operators utilizing the same frequencies a base station color code - (0-7) - consists of 3 bits which are used to differentiate between cells utilizing the same frequencies

CRO

a value between 0-6, measured between zero and 126 dBm, in increments of 2; is used by the network to artificially increase the chances of a handset reselecting to a particular and is the value transmitted by each broadcast control channel (BCCH) and added to the calculated C1 value

temporary offset

a value from 0-7, representing values of 0 to 60 dBm, in increments of 10; 7 is infinite value; temporary offset is then subtracted from the result until the penalty timer expires

ARFCN

absolute radio frequency channel number/ GSM physical channels information is broken down into logical channels

AGCH

access grant channel downlink part of the common control channel (CCC); used to assign a SDDCH or TCH to a MS

The structure and coding of a TMSI can be chosen by what

agreement between operator and manufacturer because of the TMSI's local significance

umbrella cells

also called a covering cell; micro-cell can cover several pico-cells; micro-cells covered by at least one macro-cell

micro-cells

antenna height is below average rooftop level; typically used in urban areas; 200-1000m of coverage

Stored in a SIM

authentication and encryption keys MSISDN subscriber access control class PIN/ PUK inter-PLMN roaming allowed/ not allowed indicator phone book last known location area code SMS charging information - sccumulated total of advice charge indications fixed phone number barring of outgoing calls pre-programmed PLMN seletor

AuC

authentication center

BSC

base station controller; controls up to several hundred base stations

BSIC

base station identity code; each cell is allocated a BSIC which is broadcasted in each burst sent on the synchronization channel (SCH); used by the mobile station in order to avoid ambiguity or interference which can arise when a mobile station can receive two cells using the same BCCH frequency

BTS

base transceiver station; maximum range of 35km; Tx/ Rx antennas/ towers

BCH

broadcast channels BCHs are used by the base station to broadcast the same information to all mobile stations in a cell

BCCH

broadcast control channel a logical broadcast channel on the airlink Um interface used to broadcast to the MS' radio channel configurations of the currently used cell, neighboring cells, synchronization information (frequencies and frame numbering), and network identification information (LAI, CI, BSIC, BA list, and CRO); is found on timeslot zero

CI

cell identity; a cell within a base station subsystem is identified within a location area by adding a CI to the location area identification

CRH

cell reselection hysteresis cell reselecction parameter is used to prevent a MS from repeatedly changing between cells (changing between cells in border areas between location areas (LA's) requires a location update (LU), which could cause a heavy signal overload -> risk of paging message being lost); cell in a different LA only selected if it can beat the cell currently being camped on by the CRK value in decibels for at least 5 seconds, and upon completing C2 calculation

CDMA

code division multiple access; each user occupies a signal on a particular frequency simultaneously with many other users, but is uniquely distinguishable by correlation with a special code used only by this user

CCCH

common control channel a point-to-multipoint signaling channel to deal with access management functions -> uncludes the assignment of dedicated channels and paging to localize a MS

T

countdown timer current value

DCCH

dedicated control channels a point-to-point signaling channel between the base transceiver station and the MS; associated control channel (ACCH) is a dedicated control channel (DCCH) but is only assigned in connection with traddic channel (TCH) or a stand-alone dedicated control channel (SDCCH)

3G - digital/ HS data

developed in 2000s; UMTS; WCDMA CDMA2000 - 1xRTT; EV-DO HSDPA; HSUPA; HSPA+

1G analog

developed in the 1980s; NTT- nippon telephone and telegraph for japan NMT- nordic mobile telephone system for europe and asia AMPs- advanced mobile phone systems for US, australia, asia, and africa TACs- total access communications systems for europe

2G digital

developed in the 1990s; IS-54/ 136 TDMA for US IS-95 A/B CDMAOne for US GSM - FDMA/ TDMA - worldwide

EDGE

enhanced data rates for GSM

EIR

equipment identity register; authenticates the IMEI of a handset; optional, but not generally used

ETSI

european telecommunications standards institute

EV-DO

evolution data optimized

FACCH

fast associated control channel additional badwidth can be made available for signaling by using dynamic preemptive multiplexing on a traffic channel (TCH); handles high priority messaging, call waiting, SMS, and handovers of MS in a call from one bast transceiver station (BTS) to another

reverse/ uplink frequency

frequency #2 carries information from the MS to the tower

FCCH

frequency correction channel a beacon channel with information about correction of the transmission frequency

FDMA

frequency division multiple access; frequency band is divided into certain bandwidth such that each conversation is carried on a different frequency

GMSC

gateway mobile switching center; works like a mobile switching center, but also serves as a gateway to other outside networks

GMSK

gaussian minimum shifting key

GSM uses what as its form modulation

gaussian minimum shifting key (GMSK)

GPRS

general packet radio services

How many digits are in a MSISDN

generally 10-12 digits long, but can be 10-14

GSM

global system for mobile communications

HSDPA/ HSUPA

high speed downlink packet access/ high speed uplink packet access

HLR

home location register; permanent storage database for subscriber data, one per network

forward/ downlink frequency

i.e. frequency #1 carries information from the tower to the MS

three instances of location update (LU)

initial registration -> international mobile subscriber identity (IMSI) attach/ detach; T3212 timer (periodic)- 0-255 deci-hours, six minute increments each deci-hour; 0= no updates; different location area (LA)- crossing into new LAC

ISDN

integrated services digital network

IMEI

international mobile equipment identity; the IMEI shall directly or indirectly contain all information which is necessary for the network operator to make relations through its administrative system; IMEI consists of 15 digits, however the 15th digit is not part of the digits transmitted at IMEI check occasions;

IMSI

international mobile subscriber identitiy; a 15 digit number that contains information uniquely identifying a subscriber to the GSM network; mobile stations can only be operated if a valid IMSI is present except for emergency calls; IMSI consists of a mobile country code, mobile network code, and mobile subscriber identification number

What is GSM currently?

it now includes data communications by packet data transport using GPRS and EDGE

LAC

location area code

LTE

long-term evolution

MCC

mobile country code; consists of 3 digits

MNC

mobile network code; consists of 2 digits; identifies home GSM network of mobile subscriber

MSISDN

mobile station integrated services digital network number; the permanent dialed phone number

MSRN

mobile station roaming number; a temporary number used to route calls directed to a mobile station; MSRN has the same structure as an international ISDN in the area its roaming number is allocated

MSIN

mobile subscriber identity number; last 9 digits of IMSI; number assigned by the service provider to that SIM card

MSC

mobile switching center; an ISDN switch that can handle mobile handsets, controls 5-10 base station controllers, and is considered the brains of the GSM network

NSS

network switching subsystem

PCH

paging channel part of the downlink of the common control channel (CCC); used for paging to find a specific MS; notifies the MS of mobile terminated cells

H

penalty time - T; a value from 0-21, measured in increments of 20; penalty time ranges from 20-620 seconds; a penalty time value of 31 is reserved to indicate that the cell reselection offset is subtrcted from C2 and the temporary offset is ignored

PUK

personal unblocking key

PIN

provider identification number

PLMN

public land mobile network; the entire area of service offered by service provider

handover procedure

purpose- to completely modify the channels allocated to the mobile station (when the cell is changed); handover procedure always initiated by the network; network can request inter-cell or intra-cell change of channel

RACH

random access channel the uplink portion of the common control channel (CCC); is accessed from the mobile stations in a cell without reservation in a competitive multiple-access mode using the principle of slotted Aloha (wireless data packet networking) to ask for a dedicated signaling channel for exclusive use by one MS for one signaling transaction

Rx

receive

location management

refers to the network keeping track of where a MS is located in the system area; information for each MS stored in functional units called location registers

macro-cells

regarded as macro-cells where the base station antenna is installed on a mast or larger building structure taller than an average rooftop level; covers areas up to 25km

SACCH

slow associated control channel always assigned and used with a traffic channel (TCH) or an ADCCH; carries information for the optimal radio operation (i.e.) commands for sychronization, transmitter power contol, timing advance, receive level quality, and reports on channel requirements

pico-cells

small, specialized cells whose diameter is only a few dozen meters; used mainly in indoor applications; can cover floor of a building or the entire building itself

SDCCH

stand-alone dedicated control channel a dedicated point-to-point signaling channel found on timeslot one that is not tied to the existence of a traffic channel (TCH) (i.e.) is used for signaling between a MS and a base switching subsystem (BSS) when there is no active connection; stand-alone dedicated control channel (SDCCH) is requested from the MS via a random access channel (RACH) and assigned via an access grant channel (AGCH)

SIM

subscriber identity module; a module that contains all the processes involving the authentication key; contains IMSI and mobile subscriber information

SCH

synchronization channel broadcasts information to identify a base station controller (BTS) (i.e. base station identity code (BSIC)); frequency correction channel (FCCH) and SCH always broadcast together with the broadcast control channel (BCCH)

TMSI

temporary mobile subscriber identity; a temporary number used to support the subscriber identity confidentiality service; the Visitor Location Registry (VLR) may allocate a unique Temporary Mobile Subscriber Identity (TMSI);

The Visitor Location Registry (VLR) must be capable of correlating what

the IMSI of an MS and the current TMSI for that MS

IMSI attach operation

the action taken by a MS to indicate that the station has re-entered an active state (i.e. station is powered up)

IMSI detach operation

the action taken by a MS to indicate to the network that the station has entered an inactive state (i.e. station powered down)

modulation

the process of changing the amplitude frequency, or phase of a radio frequency carrier signal to change with the information signal

TDMA

time division multiple access; individual mobile stations are cyclically assigned a frequency for exclusive use only for the duration of a timeslot, which requires frame synchronization between Tx and Rx

Why was the GSM standard developed?

to replace the first generation/ 1G analog cellular networks

TCH

traffic channel used for actual point-to-point sending and receiving of messaages in the form of voice or data communications; TCH is a combination of voice and data signals existing within the communications channel

Tx

transmit

UMTS

univeral mobile telecommunications system

location cancellation procedure

used by the home location register (HLR) to remove a mobile station from the losing visitor location register (VLR) (i.e. when a MS has a location area code (LAC) change); normally used when the MS has moved to an area controlled by a different location register

location update (LU)

used if the MS recognizes that its in a new location area, which leads to updating the location information in the home location register (HLR) record and the MS receiving updated temporary mobile subscriber identity (TMSI), location area identity (LAI), and location update message; ccan occur periodically, regardless of location -> time interval value is broadcast on broadcast control channel (BCCH); objective- knowing current location for incoming calls/ SMS -> call directed to current location

location update reject messages

used to turn a handset away from the network in the mobility management layer

numerical value of cell reselection hysteresis (CRH)

value of 0-7 (zero indicates that no CRH is applied); each increase in value up to seven, then decibel increases by two (i.e. CRH0 = 0dB ; CRH1 = 2dB ; CRH2 = 4dB ; CRH3 = 6 dB)

VLR

visitor location register; temporary storage database for subscriber data, normally co-located with a mobile switching center

WiMAX

worldwide interoperability for microwave access

watt to decibel converstions - increasing by 10's

x10 --- +10 dBm's 1 watt ---30 dBm 10 watt --- 40 dBm 100 watt --- 50 dBm

watt to decibel conversions - (doubling)

x2 --- +3 dB's 1 watt --- 30 dBm 2 watt --- 33 dBm 4 watt --- 36 dBm 8 watt --- 39 dBm 16 watt --- 42 dBm 32 watt --- 45 dBm

Is it possible to have more than one MSISDN on a GSM SIM card

yes


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