Rf Amps

Advanced Mobile Phone Service (AMPS) • Initially allocated 40 MHz of spectrum in the 800 MHz band. • It contained 666 channels • Channel spacing: 30 kHz • Duplex spacing: 45 MHz (between transmit and receive) • 624 voice channels • 42 signaling channels www.3g4gtraining.com

AMPS SPECTRUM

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Extended Advanced Mobile Phone Service (E-AMPS)

• Additional 5 MHz of reserved spectrum was allocated. • Voice channels were added . • To compensate the need to use additional filtering equipment it was allocated both side (A and B). • 790 voice channels • 42 signaling channels www.3g4gtraining.com

E - AMPS SPECTRUM

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A cellular system

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Basic terminology Channel Types Both forward and reverse voice and signaling channels are used. Data or voice are sent.

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Basic terminology Supervisory Audio Tone (SAT) Is one of three tones in the 6 kHz region. Used to verify the presence of the telephone's signal on a designated channel

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• 5970 Hz • 6000 Hz • 6030 Hz

Basic terminology SAT Color Code (SCC)

A digital value indicating the subscriber the new SAT to expect.

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• • • •

00 01 10 11

5970 Hz 6000 Hz 6030 Hz not used

Basic terminology Digital Color Code (DCC)

Allows signaling channel reuse. The subscriber transponds a seven bit "coded DCC"

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DCC 00 01 10 11

Coded DCC 0000000 0011111 1100011 1111100

Channels • A radio channel used to transmit signaling information from the land station to the mobile is referred to as a “Forward Control Channel” (FOCC). • Similarly, a radio channel used to transmit signaling information from the mobile to the land station is referred to as the “Reverse Control Channel” (RECC). • The system also has “Forward Voice Channels” (FOVC) and “Reverse Voice Channels” (REVC www.3g4gtraining.com

Mobile station • Each mobile station EEPROM has two sections: the Number Assignment Module (NAM) and the Serial Number Module (SNM). • NAM: mobile’s directory number, system parameter information, options, features, and configuration information. • SNM: unique electronic serial number. • SCM indicates the maximum transmitter power level of the mobile station. Class I..........................................6 dBW (4.0 watts) Class II.........................................2 dBW (1.6 watts) Class III.......................................-2 dBW (0.6 watts)

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Data encoding and transmission • The data is transmitted FSK • Non-return to zero (NRZ) is used. • The data speed, in both directions, is 10 KB/sec • L-M data word contains 40 bits • M-L data word contains 48 bits

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Control channel functions • A control channel is used to inform all mobiles of system parameters and to communicate with an individual mobile when it attempts to “access” the system. • Mobile access involves the mobile transmitting his MIN on a reverse control channel (RECC).

Forward control channels messages • Overhead message • Mobile station control message • Control-Filler message (Control-Filler messages may be inserted between messages and between word blocks of a multi-word message)

Overhead messages • Are repeated every 0.8 seconds, and contain information intended to be received by all mobiles active in the system. This information includes: – System Identification (SID) – Whether or not the paging and access channels are combined (Parameter CPA) on the same channel. – The range of paging channels that the mobile must scan (Parameter N). – The number of access channels that the mobile must scan (Parameter CMAX). – Information regarding when each mobile should register.

Mobile station control messages • Contain information directed to a specific mobile. This information includes: – Paging Data – Mobile transmit power level control on the voice channel. This parameter is referred to as the Voice Channel Mobile Attenuation Code (VMAC). – “Orders.” An order is a signal that causes a specific mobile to respond. Orders are used to make the mobile alert, generate ATB tone, release the mobile, and other functions.

Control filler messages • Part of the overhead message train and are sent when there are no other messages to be sent on the FOCC. • This enables the FOCC to send a continuous data stream. • The control filler message can also be used to inform all mobiles of the transmit power level is to be used when transmitting on the RECC (Control Channel Mobile Attenuation Code)

Power Control Parameters • Each Motorola cell uses parameters

to define a “power box”. • The power box is a range of signal strengths that define the mobile power control from the base site. • The CHANGE MOB SECPRM MMIs contain the mobile power control parameters.

Power Control Parameters CMPFLG • Indicates whether relative (REL) or absolute (ABS) power value measurements will be used for handoffs. Always use RELATIVE. handoffs. PSHO Power setting for handoffs • Valid inputs are 1-255 (SSI units). The mobile’s RSSI at which a handoff will be requested. When mobiles are scanned below this threshold, the VCC will increment the #IHO counter. To convert RF power from dBm to SSI units, use: SSI = (2.25 x dBm) dBm) + 314.5 dBM = (SSI - 314.5) / 2.25

Power Control Parameters #IHO Number of indications required for handoff. • The minimum number of consecutive scan measurements below PSHO to generate a handoff request. Valid inputs are 1-15. MAXSS • Maximum signal strength required before reducing the mobile’s transmit power. MAXSS defines the “top of the power box”. When mobiles are scanned above this threshold, the VCC increments the MAXRED counter. Valid inputs are 1-255 (SSI units).

Power Control Parameters MAXRED • Number of scans above MAXSS required to power a mobile down. Valid inputs are 1-15. MINSS • Minimum signal strength required before increasing the mobile’s transmit power. MINSS defines the “bottom of the power box.” When mobiles are scanned below this threshold, the VCC increments the MINRED counter. Valid inputs are 1-255 (SSI units).

Power Control Parameters PWRVAL • The relative power value (RPV) by which the signal strength at the target cell must exceed the signal strength at the source cell to be an acceptable handoff candidate. (Target_RSSI > Source_RSSI + Target_RPV) FCT • Foreign Carrier Threshold is the signal strength threshold above which an idle channel will taken out of service due to the presence of an interference problem. Motorola SE recommends setting the FCT approximately 10 dB lower then MINSS. Valid inputs are 1-255 (SSI units).

Power Control Parameters LNAOFF • Low Noise Amplifier Offset is used to compensate for “artificial” differences in the signal strength measurements between cells in various configurations. The standard value for the LNAO is 51. For sites using low noise amplifiers, the standard value is 83. LNAOFF only affects the reported signal strength, strength, not the actual signal strength. strength. The valid inputs are 1-101. NOMSS • The optimal signal strength for a mobile to arrive at the target cell site after a handoff. This value is used by the BSC to assign a VMAC to the mobile. • The target cell site calculates the lowest power level which will bring the mobile’s RSSI in above NOMSS. Note: If NOMSS is set to a value outside of the power box, the BSC will set it to a default value equal to the middle of the power box. Valid inputs are 1-255 (SSI units).

Power Control Parameters MAXPL • Specifies the maximum transmit power level for mobiles in the sector. Valid inputs are 0-7. EHOTHR • Emergency Handoff Threshold is the signal strength used to initiate the emergency handoff algorithm. The algorithm is initiated when a mobile is scanned once below this threshold. Valid inputs are 1-255 (SSI units). O/U MAXPL • Specifies the maximum transmit power level for mobiles in the inner group of the sector in a Underlay/Overlay cell site. Valid inputs are 0-7. (Prompt only appears if the O/U feature has been loaded onto the EMX)

Power Control Parameters OUEHA • Emergency Handoff Indicator is a flag which will enable/disable emergency handoffs from the inner group of channels in a Underlay/Overlay cell. (Prompt only appears if the O/U feature has been loaded onto the EMX) SIGFCT • The Foreign Carrier Threshold for the Signaling channel. The signal strength threshold that will issue an IPR when interference is detected on the signaling channel. Valid inputs are 1-255 (SSI units).

PRIORITY OF EVENTS (COUNTERS)

• The power box counters have been prioritized into a hierarchy because different mobile events may trigger different counters at the same time. Action

Priority over

Resets

Type of Counter

Emergency

All

Depends on result

One Scan reading

Port Change

Power Change / Handoff Power Change / Handoff Consecutive

Power Change Handoff

Handoff

Increment/Decrement

Handoff

None

Consecutive

None

PRIORITY OF EVENTS (COUNTERS) • The power control counters are increment/ decrement

counters. For example, three scans below MINSS and one scan above MINSS gives the power-up counter a net value of two. • All counters are SAT/DSAT qualified. There must be a positive SAT/DSAT reading on the scan job to increment the counter. • When calculating a new attenuation level (VMAC), after a power change, the BSC attempts to place the mobile in the middle of the power box. • A power change or port change will reset the hand-off counter.

Handoff • The scan receiver, periodically examines the RF signal of each mobile active on a voice channel in the cell. • The scan receiver examines each mobile's signal strength about once every 3.6 seconds • If the received signal strength falls below a minimum predetermined threshold level (Power Setting for handoff) for a number of successive scans NIR (Number of Indications Required), the GLI generates a handoff request to the EMX

Handoff types • There are three basic kinds of handoff: – The inter-cell handoff which is the handoff between two cells controlled by the same EMX – The inter-EMX handoff which is the handoff between two cells controlled by two different EMXs – The inter-sector handoff which is the handoff between two sectors of the same cell.

Handoff types • There are also four other special kinds of handoff: – The inter-vendor handoff which is based on the IS -41 feature and is the handoff between two cells controlled by switching systems of different vendors – The interference driven handoff which is based on the MRI and the C/I features, and which is performed within the same sector of a cell – The emergency handoff which is based on the emergency handoff feature, and which is an inter-cell handoff – The inter-tier handoff which is based on the overlay/underlay feature, and which is the handoff between the inner and the outer tiers of the same sector.

Emergency HO • If the mobile signal strength is below

the emergency re-scan is scheduled. • If the average of the two scans is still below the emergency threshold, action will be taken so that the mobile is powered up, if possible, or handed off to the first acceptable candidate. • If a hand-off request is made, the EMX does not wait for a second response after the first one arrives.

HANDOFF- HOLDOFF TIMER • Suspends any non- Handoff activity

(such as power changes or port changes) on a mobile for a period of time after a handoff request is issued for that mobile. • All counters still increment and decrement accordingly, but no action will be taken until the first scan after the expiration of the Handoff- Holdoff timer.

System Failures • RF Losses • HO Failures • Access Failures

RF LOSS DECLARATION (WIDE) • Uplink: With DTX disabled, an RF Loss is

declared after 10 seconds of no SAT on voice transceiver or 7 scans with no SAT. • The base station reports the dropped call as an ‘Uplink RF Loss’. The transceiver will report to the VCC after 2 seconds of no SAT from the mobile. An RF loss is declared after 12 seconds total (2 seconds from xcvr + 10 second timer).

RF LOSS DECLARATION (WIDE) • Downlink: If the mobile does not detect

SAT for 5 seconds, it de-keys and retunes to the signalling channel. • Note: the base station cannot discern an uplink RF Loss from a downlink RF Loss! Because there is no communication from the mobile before de-keying, all RF losses appear as uplink losses from the base station’s perspective.

RF LOSS DECLARATION (NAMPS) • Uplink: With DTX disabled, an RF Loss is

declared after 10 seconds of no DSAT on voice transceiver or 7 scans with no DSAT. The base station reports the dropped call as an ‘Uplink RF Loss’. • Downlink: If mobile does not detect DSAT for 5 seconds, the mobile sends a “Fade Release” order to base station before dekeying. The base station reports the dropped call as a ‘Downlink RF Loss’.

HO Failures

Access Failures

SCANNING • • • • •

DUAL MODE SCAN RECEIVER Tunable receiver Capable of scanning AMPS, EAMPS and NAMPS channels. Supports voice SAT rely The mobile’s signal strength will be measured every 3.6 seconds The scan also process HOMRS.

LOCAL SCAN JOBS • Are periodic scans of active

mobiles to ascertain their SSI, antenna position, and whether or not SAT (or DSAT) can be detected. • The report information is used to update the power control parameters.

HOMR JOBS • Hand-Off Measurement Requests,

are scans of neighboring cells’mobiles to determine if a handoff is appropriate. • The job records the mobile’s SSI, strongest antennas, and whether SAT/DSAT is present. • HOMRs are processed in a “RoundRobin” order by one of the idle scan receivers in the site.

FOREIGN CARRIER JOBS • Foreign carrier jobs are scans of

idle channels to determine if an interferer is present. • If interference is present above a user-defined threshold, the channel will be taken out of service and a MCON-374 IPR will be generated at the EMX.

SCAN LOADING • With the default scan rate of 3.6 seconds, each SC9600 scan transceiver can support up to 15 client TCHs. • Increasing the scan rate (shorter Interval) will lower the number of client TCHs that a scan could handle at the desired scan rate. • client TCHs = 30 / [(7.2 sec)/(scan rate)] (rounded up It remainder exists). scan rate = 2.8 secs client TCHs = 30 / [7.2/2.8] = 11.67 (rounded up) = 12

Registrations • A process in which a mobile makes his whereabouts known to the system. • When a mobile registers, the system will update the subscriber record of the mobile.

How many kinds of Registration are there? Supposedly "Different" types of Registration 1) Fixed Registration 2) Incremental Registration 3) Forced Registration 4) Home/Roam Registration 5) Implicit Registration 6) Power-on Registration 7) Sysid Registration 8) Originating Cell origination 9) Terminating Cell origination

How many kinds of Registration are there? "Real" types of Registration 1) SYSID Induced Registration - - SYSID changes 2) REGID Induced Registration - - REGID is out - ofbounds

SYSID and REGID • REGID and SYSID are numbers which are periodically transmitted over the signaling channels of cells sites • Mobiles monitor these numbers and compare them to numbers in their own memory. • If a SYSID is different than a number stored in the mobile's memory, the mobile will register. • If a REGID is larger than an upper limit stored in the mobile's memory (NXTREG), the mobile will register

REGID

NXTREG • In addition to the REGID messages transmitted over the signaling channel, messages containing a value called REGINC (seconds) • Every time a mobile receives a REGINC message, it copies the number into a location called REGINC • Whenever a mobile registers, it adds REGID and REGINC to determine a new NXTREG value.

REGINC+REGID=NEXTREG • When REGID becomes greater than or equal to NXTREG, or when REGID becomes less than or equal to the quantity NXTREG minus the Registration Increment minus 5, the mobile unit will reregister.

DISPLAY MOB REGDAT DISPLAY MOB REGDAT PAGING AREA: / Enter the cellular paging area. (Range and multiple entries are not allowed.) [1-10] : 1 PAGING REGISTRATIONS ENABLED AREA (HOME/ROAM) ------------------------------------------1 HOME/ROAM

REGID REGID REGISTRATION REGISTRATION MODE PERIOD ZONE NUMBER INCREMENT ----------------------- ---------------------- ---------------------INCREMENT 5 240 2820

IMPLICIT DEREGISTRATION • Provides the EMX with the means to block pages to mobiles who have been considered inactive for a given length of time. • Implicit DeRegistration (IDR) will reduce the paging load on the system. • The IDR time out should be set to a time interval greater than the registration expiration interval

DISP CP IMDREG DISP CP IMDREG IMPLICIT DEREGISTRATION ENABLED -------------Y

EXPIRATION INTERVAL ----------------------------------DAYS HOURS MINUTES -------- ---------- -------------0 8 0

Electronic Mobile Exchange (EMX) • It is the controlling device of

the cellular system. • It is connected to the cell sites. • It is the interface between the

subscriber and the Public Switched Telephone Network (PSTN)

EMX Overview There are 7 main functional subsystems within the EMX: •Admin Subsystem •Call Proccessing Subsystem •Cellular Networks Subsystems •Common channel signaling subsystem •Matrix Subsystem •Mobile Control subsystem •Trunk manager subsystem

Admin Subsystem •Collects and store Billing and Stats. •Download program and database information. •Stores databases and configurations of the EMX. •Provide access to terminal, modems and high speed data links. •Manages the Alarm and Trunk Test Subsystems. •Process commands.

Call Proccessing Subsystem •Responsible for dialed digits translation. •Selecting trunking routes and mantaining their idle status. •Mantaining a mobile busy list. •Collecting and distributing CDR for billing purpouses. •Download programs to the line/trunk managers and processors. •Collects statistics and send them each 30 minutes to the Admin.

Cellular Networks Subsystems

•Manages inter-EMX communications.

Common channel signaling subsystem

•Manages SS7 or C7 signaling capability. •C7 and SS7 are structured so signaling information for a voice circuit is carried over a different circuit than the voice itself.

Matrix Subsystem •Operates the switch matrix hardware. •Operates the Service Circuits.

Mobile Control subsystem •Provides a interface between EMX and

cellsites. •Monitors the status of cellsites. •Performs HO managements. •Generates pages.

Trunk Manager subsystem •Controls the flow of a call through the switch. •Controls the processing status. •Manage the signaling and supervisory control of line/trunk ports.