Basic Overview of GSM Communications
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
