STATION ID - 7047/3.12

9x Datakit Network
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official 9x business only. Anyone using this system, network or data
is subject to being monitored at any time for system administration and
for identifying unauthorized users or system misuse. Anyone using this
system expressly consents to such monitoring and is advised that any
evidence of criminal activity revealed through such monitoring may be
provided to law enforcement for prosecution.

Cellular Mobile Carrier Interconnection
by mastry0da

Contents:

1.0..........General
     .......... Definition of Terms
     .......... Background Information
     .......... Description of Basic Cellular System Configuration

2.0.......... Interconnection Types
     .......... Description
     .......... Type 1
     .......... Type 2A
     .......... Type 2b

3.0.......... Numbering, Dialing, and Routing Plans
     .......... Land Line Station to Mobile Station Calls
     .......... Mobile Station to Land Line Station Calls

4.0.......... Interfaces
     .......... General
     .......... Transmission Interface
     .......... Digital Interface

5.0.......... Circuit Designs
     .......... Descriptions
     .......... Interconnection Circuit
     .......... Cell Site Link
     .......... Transmission Limits for Interconnection Circuits
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1.0 General
Definition Of Terms

1.01 - The following generic terms are used to describe various components of cellular systems.

* Cell Site: A transmitter-receiver location, operated by the Cellular
Mobile Carrier (CMC), through which radio links are established between
the cellular system and mobile units. The area served by a cell site is
referred to as a "cell"

* Cellular Geographic Service Area: The geographic area served by the
cellular system within which a CMC is authorized to provide service.

* Mobile Telephone Switching Office (MTSO): The hub controller, operated
by the cellular carrier, which exercises system control over a cellular
communications system.

* Cellular System: A high capacity land mobile radio system in which an
 assigned frequency spectrum is divided into discrete channels that are
  assigned in groups to cells covering the Cellular Geographic Service
  Area (CGSA). The discrete channels can be reused in different cells
  within the same service area. Calls are "handed off" automatically
  from a channel in one cell to a different channel in a an adjacent
   cell as the mobile unit moves across cell boundraries with the CGSA.
 
*Cell Site Link: A circuit that interconnects an MTSO with a cellsite.

*Radio Links: Radio frequency communication channels between cell site
 transmitter-receivers and mobile portable units.

*Interconnection Circuit: A circuit that interconnects a Bell Operating
 Company (BOC) switching office with a cellular MTSO.

1.02 - Background Information
The CMC defines the cellular geographic service area for a given cellular
 system in accordance with guidelines set by the FCC. The Cellular Geographic
  Area is divided into cells varying in size, according to terrrain, density
  of mobile subscribers, and anticipated traffic volumes.
Cellular communications systems reuse the radio frequencies within each
Cellular Geographic Service Area. The assigned frequency spectrum is
 divided into discrete channels that are assigned in groups to cells
 convering the service area. The discrete channels can be reused in
 different non-adjacent cells within the service area. As a mobile
 unit moves across cell boundaries within the Cellular Geographic Service
 Area, an established call is transferred automatically from a channel in
 one cell to a different channel in an adjacent cell under the control of
 the MTSO.
Cellular technology promotes efficient use of the readio frequency spectrum
and accomodates large numbers of mobile customers through frequency reuse.
The ability to split cells and reassign channels permits cellular systems
to adapt to increasing or changing subscriber and traffic densities.

1.03 - Description of Basic Cellular system configuration
        In the badic cellular system, the mobile units interact with the
        cell site transmitter-receiver equipment via radio links. Cell
        sites connect to the MTSO via Cell Site links. The MTSO interconnects
        with one or more BOC switcing offices via interconnection circuits.
        These have been classified as one of three interconnection opations
        and are explained further later in the text.

2.0 - Interconnection Types
        There are various switched interconnecetion alternatives available
        for the interconnection of a cellular mobile system with a BOC
        network. Three specific typed of interconnections are identified
        in this section: connection through a BOC end office (Type 1) ,
        direct CMC connection with a BOC Tandem office (Type 2a), and a
        direct connection limited to a specific BOC end office (Type 2b).
        CMC connection to the BOC local access and Transport Area (LATAs) 
        and other carries ( another CMC, exchange carriers,  or interexchange
        Carriers) for Type 1 and Type 2a is proveded through the BOC
        interface swtich. The type 2b interconnection may be used in
        conjunction with the Type 2a tandem interconnection on a high
        usage alternate routing basis.

2.02 - Type 1
        Type 1 interconnection is between the CMC0-designated POT and a BOX
        end office switching system that enables a path to be established
        between the CMC's MTSO and the BOC endo office. The CMC established
        connections to other end offices and other carriers through this
        interconnection.

2.03 - Type 2a
        Type 2a interconnection is at the POT of a trunk between a cellular
        MTSO and a designated BOC tandem switching system. Through this option,
        the CMC can establish intra-LATA connections to the BOC end offices
        connected to the tandem. Type 2a interconnection may be used on an
        inter-LATA basic through proper arrangement with the ICs.

2.04 - Type 2b
        Type 2b interconnection is at the POT of a trunk between a cellular
        MTSO and a BOC end office switching system. Through this option, the
        CMC established connections to NXXs served by the one end office to
        which it is interconnected. A type 2b interconnection may be used in
        conjuntion with the Type 2a on a high usage alternate routing basis
        to serve the high-volume traffic between the MTSO and the BOC end office. 


3.0 - Numbering, Dialing, and Routing Plans

3.01 - Each Mobile station served by a cellular MTSO is identified by a unique North American Numbering Plan destination address code (Telephone Number). Because Cellular systems have the capability to accomodate large numbers of mobile stations, sizable quantities of telephone numbers are needed. In large metropolitan cellular market areas, cellular carriers, may require, the equivalent of several, complete central office (NXX) codes to provide each mobile station its own unique telephone number.



3.02 - Cellular mobile carriers can design their systems so that MTSO interfaces, via Type 1 interconnection circuits, with more that one end office. Cellular systems designed in this manner may require allocation of blocks of telephone numbers from each end office they interconnect with, rather than having all telephone numbers appear in just one central office code.



3.03 - Calls from land line stations to mobile stations served by cellular systems are dialed and routed in the same manner as calls between land line stations. The land line calling party dials the mobile station's 7 - 10 digit telephone number without an access code unless there is a need to specify an IC for transport of the call. The BOC makes a call record when necessary for billing purposes.



3.04 - Land line station to cellular system mobile station calls are routed over the BOC network to the BOC switching office, which interconnects with the MTSO. That office translates the digits received, seizes a circuit to the MTSO and, adter receiving the appropriate start signal, outpulses a sufficient number of digits to identify the called mobile station.



3.05 - The cellular MTSO signals the called mobile station upon receipt of digits from the telephone company office. The cellular MSO will transmit and answer signal to the BOX switching office when the called mobile station goes off-hook (answers), and a disconnect signal when the mobile station goes on-hoook (hangs up).



3.06 - On calls from mobile stations served by cellular systems to land line stations, the cellular MTSO seizes an interconnection circuit to the designated BOC switching office and, after receiving a wink signal, outpulses the called land line number to the station's 7 or 10 digit phone number. The BOC makes a call record when necessary for billing purposes.



3.07 - Inta-Lata calls handles by the BOC are routed over the BOC network to the end office where the called land line stations's phone number is assigned. That end office rings the called land line station. An answer signal is transmitted to the cellular MTSO when the called land line station goes off-hook, and a disconnect is transmitted when the land line station goes on-hook to terminate the call.



3.08 - Calls which are to be routed via the BOC network to an IC may be indicated by the mobile station by dialing hte proper carrier access code. For example, calls routed to an IC that has Feature Group A (FG A) switched access service may be indicated by dialing the appropriate 7 - 10 digit FG A code. Similarly, for FG B the appropriate 950-0xxx or 950-1xxx code is dialed by the mobile station.



4.0 - Interfaces

4.01 - Many cellular mobile carriers use digital systems to perform the cellular MTSO and/or cell site functions. Direct connection of these digital switching systems to digital facilities may be technically and economically desirable to elimate the need for digital to analpg to digital converstion and allows digital transmission facilities to be used where most cost-effective.



4.02 - Digital Facilities may be used to interconnect cell sites with the cellular MTSO and/or the MTSO office with BOC offices where appropriate tariffs or contracts are available. Normally these facilities provide point to point 1.544 mbps (DS1) full duplex transmission of serial bipolar pulses, with constraints on signal format. 



4.03 - Timing information for synchronization of a digital cellular switching office is needed whenever that office is connected to the land line network via digital facilities. In such a case, the timing information can be transmitted isochronously over the DS1 lineas part of the 1.544 mbps signal, subject to the constraint that a given statum level clock cannot derive from a lower stratum level clock. If a digital MTSO is of a higher stratum level than the BOC office to which it is connected, timing information for synchonization is derived from a separate digital connection to a network node of the appopriate stratum level. The cellular carrier is the source of all timing information on DS1 lines between a digial MTSO and digital cell sites.



5.0 - Circuit Descriptions

5.01 - The interconnection circuits and cell site links described herein are intended to provide a grade of service to the cellular subscriber which is comparable to that achieved on the public switched network. A wide range of transmission level points (TLPs) are available at the POT to accomodate various transmission schemes



5.02 - Interconnnection circuits connect the BOC offices with the Cellular MTSOs. For example, the Type 1 interconnection provides a trunk connection between the BOC end office and the MTSO, and uses line type addressing sequences and multifrequency (MF) trunk signalling. In contrast, the Type 2a interconnection provides a trunk connection between a BOC tandem and the MTSO, and uses trunk addressingsequences and multifrequency (MF) trunk signalling.



5.03 - At the BOC test position, 0 TLP is used for transmission toward, the CMC. The reveive level from the CMC is also stated at the BOC test position and is the equivalent of the inserted connection loss (ICL) of the switch to switch trunk plus the valus of test pads (T) at both the CMC and BOC switches. 



5.04 - The test level of switches operating as offices is a nominal 0 TLP (0db test pad) regardless of whether the switch is digital of analog. The BOC tandem switch may operate as a 0 TLP (analog), -2 TLP (analog) or eqivalent -3 TLP (digital). Where a BOC has a 0 TLP tandem, interconnection information should be obtained locally on an individual case basis.



5.05 - The physical interface between the BOC and the CMC is defined as a function of the interface group used by the CMC. The most commonly used interface groups for cellular interconnections are described later below.



Interface Group 1: provides 2 wire voice frequency transmission at the CMC POT. The interface is capable of transmission of voice and assosciated telephone signals withing the frequency bandwidth of about 300 - 3000 hz.



Interface Group 2: provides 4 wire voice frequency transmission at the CMC POT. The interface is capable of transmission of voice and assosciated telephone signals within the frequency bandwidth of 300 - 3000 hz.



Interface Group 6 : provides DS1 digital transmission at the CMC POT at the carrier terminal location. The interface is capable of localizing up to 24 different voice frequency paths.



Interface Group 9 : provides DS3 digital transmission at the CMC POT at the carrier terminal location. The interface is capable of localizing up to 672 different voice frequency paths.



5.06 - At both the cellular MTSO and cell site, one configuration which may be selected by the cellular carrier provides a loss less 4 wire interface. Signalling for this interconnection is typically E and M, Type 1 or 2, and can be either A Type (terminal equipment that originates on the M lead) or B Type (terminal equipment that originates on E lead).
5.07 - Transmit and receive levels at both interfaces must be specified by the CMC within a defined range of levels. To accommadate a wide range of interfaces and levels, service is generally terminates in channel terminating equipment, and can be either separate equipment or included in an analog or digital carrier system channel unit.
5.08 - Acceptable circuit performance dictates that 2 sets of transmission limits be met between the POT and the first point of BOC switching. First, the acceptance limit must be satisfied at the time the circuit is provided for service. Second, the immediate action limit threshold must not be exceeded during the time that service is provided. A circuit that exceeds the immediate action limit threshold requires immediate corrective action.
5.09 - The voice grade transmission parameters which are represesnted by these limits are loss deviation C-message noise, C-notched noise, 3-tone slope, and balance. The control of these parameters within the stated limits should provide voice and permissive data transmission performance which is consistent with that offered for switched intra-LATA and LATA access message service. The following provides a brief definition of each impairment and its effect.
5.10 - Loss is the primary design parameter and refers to the attentuation of a signal traversing a communication parth. Expected Meausured Loss (EML) is commonly used to express the difference between the transmitted and measured test levels.The loss deviation limit is the difference between the ETL (Expected Test Level) and the AML (Actual Measured Loss). This is used to provide assurance of continuity and alignment within the basic constraints.
5.11 - C-message noise is the combined steady state noise from such sources as thermal, 60 hz power or intermodulation. This measurement is taken using a standard C-message weighted filter in the receive circuit of the measuring set. Measurements are expressed in decibels above reference noise (dBrn) with that reference being -90 dBm and equating to a 0-dBrn reading. The notation dBrnC, refers to the usage of C_messaeg weighting. In addition to ensuing that circuit specifications are met, noise measurements are valuable in detecting common noise conditions affecting other circuits.
5.13 - C-notched noise measurements are used to determine if harmonic distortion or quantizing noise is present on a given channel. To measure this noise, a 1004 hz holding tone at -16dBm0 must be applied at teh far end of the channel under test and then filtered out by the use of a C-notched fileter in the measuring set. This process allows for measuring any noise on the channel created by the holding tone while not measuring the tone itself.

5.14 - 3-tone slope is measured primarily to ensure that the channel under test has a frequency response which will not distort voice transmission quality or inband signalling. In this test, the loss of a channel is measured at three different frequencies: 404, 1004, and 2804 hz, each applied at a -16dBm0 level. The difference in loss at 404 and 2804 Hz when compared to 1004 Hz is used to determine the slope of a channel.

5.15 - Balace refers to the matching of a impedance irregularities which can occur at any 4 to 2-wire junction and can result echo, near singing or singing conditions. These conditions are made worse by incresed delay and decreased loss. Balance valuse are stated as Equal Level Echo Path Loss (ELEPL) for a 4-wire interface or Return Loss (RL) for a 2 wire interface.
In Conclusion...
This is pretty much all I know about Cellular Mobile Carrier Interconnection, I have purposely over-simplified this article for people who find it necessary to ask me to explain things to them "in english" on irc. I don't really expect to have any questions about CMCI because its all pretty self explanatory.

masty0da@phunc.com
http://www.ninex.com/~masty0da
