different between TRANSMISSION AND COMMUNICATION

Let us now understand the difference between transmission and communication. Transmission means physical movement of information from one point to another. Communication means meaningful exchange of information between the communicating devices.

Example

Two persons, one knowing English language only and the other knowing French language only cannot communicate with each other.

Here transmission is taking place, but communication is not there. Therefore, for communication, we need much more than the transmission. For communication, we must have the same language, i.e. Data codes should be understood both by transmitter and the receiver. Moreover, receiver should be in a position to receive, i.e. Timing is also very important.

We have two types of communication :

(1)               Synchronous Communication.

(2)               Asynchronous Communication.

Synchronous Communication

In Synchronous communication the exchange of information is in a well disciplined manner, e.g. if A want to send some information to B, it can do so only when B permits it to send. Similarly, vice-versa is true. There is complete synchronisation of dialogues, i.e. each message of the dialogue is either a command or a response. Physical transmission of data may be in synchronous or asynchronous mode already decided between A and B.

Asynchronous Communication

In Asynchronous communication the exchange of information is in less disciplined manner, e.g. A and B can send messages whenever they wish to do so. Physical transmission of data may be in synchronous / asynchronous mode.

Thus, we see that Simplex Transmission is one way communication (OW), Half Duplex Transmission is two way Alternate Communication (TWA), and Full Duplex Transmission is two way Simultaneously Communication (TWS).

Remote OMT and Remote OMT over IP

The features Remote OMT (Operation and Maintenance Terminal) and Remote OMT over IP are updated to support the new RBS 6000 DUG-20/RUS-01 configurations. In MCPA backwards compatible mode, having a BTS G11A or newer in a BSS 07B-G10B network, the configuration of an MCPA is made using OMT. Configuration in MCPA single mode (BTS G11B with BSS G10B or newer) is made from the BSC, refer to Section 5.7 on page 43.

All TRXs in a DUG are connected to one or several RUSs. It is the connections between RUSs and antennas that will decide which MCPAs to use for which antenna sectors (cells).

Each antenna sector is configured in the OMT with the default configuration of 3*20W (3*43.0 dBm) per MCPA. If desired it is possible to choose a different number of TRXs per MCPA, and it is possible to choose some configurations where the total MCPA mean power will end up on less than 60 W (47.8 dBm). Also the levels 40W (46.0 dBm) and 20W (43.0 dBm) are available.

The chosen number of TRXs and MCPA maximum mean power corresponds to different GSM RUS HW activation codes, although there is no licensing mechnism involved in the OMT based configuration.

Antenna Control - Standard TMA

The RBS 6000 Radio Units have built-in functionality for what would otherwise require external equipment so there is no need for installation of extra hardware for supervision and power feed for TMAs. The radio units in RBS 6000 will provide the power and also supervise standard TMAs by monitoring the current consumed by the TMA.

Commands:

• RXBFC, Radio X-ceiver Administration, BTS Feature Data, Change

The parameter to activate Standard TMA (CSTMA) is added to this existing

command.

Printouts:

• RADIO X-CEIVER ADMINISTRATION BTS FEATURE DATA (command RXBFP)

• RADIO X-CEIVER ADMINISTRATION MANAGED OBJECT

CONFIGURATION DATA (command RXCDP)

Automatic IRC Tuning - Interference Rejection Combining

Automatic IRC Tuning is used instead of Automatic FLP by operators that wants to maximize IRC (and SAIC) performance but do not use FLP. As with Automatic FLP, the feature performs daily downlink interference matrix measurements and creates synchronization clusters for synchronization status monitoring. TSC and FSOFFSET parameters are continuously supervised and automatically adjusted to network changes when needed.

By using Automatic IRC Tuning an operator will get the following benefits:

>Automatic configuration of IRC (Interference Rejection Combining) related parameters:

- TSC for hopping channel groups.

- FSOFFSET for neighbor cells that are GPS synchronized. By this co-TSC interference can be suppressed.

> Maximum gain from IRC and SAIC.

> Possibility to monitor synchronization status for Synchronized Radio Network cells.

Automatic IRC Tuning is allowed to be activated in the same BSC as Automatic FLP. When both features are active in the same cell it will behave as Automatic FLP.

Commands and Printouts

Commands:

RFFBI: Radio Control Function, BSC Automatic FLP, Initiate

RFFBE: Radio Control Function, BSC Automatic FLP, End

RFFBC: Radio Control Function, BSC Automatic FLP, Data, Change

RFFBP: Radio Control Function, BSC Automatic FLP, Data, Print

RFFLP: Radio Control Function, Synchronization Cluster Data, Print

RLFCC: Radio Control Cell, Cell Automatic FLP Data, Change

RLFCP: Radio Control Cell, Cell Automatic FLP Data, Print

Automatic FLP - Frequency Load Planning

Automatic FLP will enable operators to run Frequency Load Planning (FLP) networks, including Synchronized Radio Networks, with minimum effort and maximum performance. The feature performs daily downlink interference matrix measurements and creates synchronization clusters for synchronization status monitoring. FLP parameters are continuously supervised and automatically adjusted to network changes when needed due to for instance lost synchronization, addition of TRX HW, or changes in hopping frequency sets. The parameters that are put under direct BSC control by Automatic FLP activation are, HSN, FNOFFSET, MAIOs, TSC and FSOFFSET.

By using Automatic FLP an operator will get the following benefits:

·         Maximum capacity gain from FLP (best parameter configuration always used. Parameter settings can be kept continuously optimized)

·         Maximizes performance in all types of FLP networks (for example lower drop call rate, better speech quality)

·         Reduced O&M cost for FLP networks (Ease of use). Parameter settings will be optimized made without user intervention.

·         Necessary parameter changes in response to unplanned network changes can be very fast

·         Possibility to monitor synchronization status for each cell. Enables immediate FLP reconfiguration after loss of synchronization.

GSM - LTE Cell Reselection

 Broadcasts LTE system information in the GSM network to enable idle and packet transfer  mode cell reselection from GSM to LTE networks.

Each GSM cell broadcasts information about:

• Neighboring cells (WCDMA and LTE)

• Thresholds for IRAT

• Priority between GSM, WCDMA and LTE cells

The information is broadcasted in the GSM network via the system information message SI2quater.

The main purpose with priority based cell reselection is to allow reselection to LTE, but at the same time it also introduces cell reselection based on priority towards WCDMA. This is an alternative to the existing non priority based cell reselection to WCDMA. When cell reselection to LTE is used, cell reselection to WCDMA will be priority based as well. In MSs not supporting priority based cell reselection, the non-priority based cell reselection to WCDMA is used if the feature "GSM-UMTS Cell Reselection and Handover" is activated.

Commands and Printouts

• RLSRI: Radio Control Cell, System Information RAT Priority, Initiate - This new command is used to inform that priority based cell reselection shall be used.

• RLSRC: Radio Control Cell, System Information RAT Priority Data, Change - This new command have three formats, one each for GSM, WCDMA and LTE. The purpose with the commands are to configure different priorities between GSM, WCDMA and LTE in the cells.

• RLSRE: Radio Control Cell, System Information RAT Priority, End - This new command is used to inform that priority based cell reselection shall be deactivated.

• RLSRP: Radio Control Cell, System Information RAT Priority Data, Print This new command prints the state of the priority based cell reselection.

• RLSEI: Radio Control Cell, System Information E-UTRAN Restriction, Initiate - This new command is used to black list individual E-UTRAN (LTE) cells for cell reselection per LTE frequency in each GSM cell.

• RLSEC: Radio Control Cell, System Information E-UTRAN Restriction, Change - This new command is used to black list specific LTE cell groups for cell reselection per LTE frequency in each GSM cell.

Time Division Multiple Access (TDMA)

 GSM uses Time Division Multiple Access (TDMA) as its access scheme. This is how the MS interfaces with the network. TDMA is the protocol used on the Air (Um) Link. GSM uses Gaussian Minimum-Shift Keying (GMSK) as its modulation methods.

Time Division means that the frequency is divided up into blocks of time and only certain logical channels are transmitted at certain times. Logical channels will be introduced in the next lesson. The time divisions in TDMA are known as Time Slots.

Time Slots : A frequency is divided up into 8 time slots, numbered 0 to 7.

Absolute Radio Frequency Channel Number (ARFCN)

The ARFCN is a number that describes a pair of frequencies, one uplink and one downlink. The uplink and downlink frequencies each have a bandwidth of 200 kHz. The uplink and downlink have a specific offset that varies for each band. The offset is the frequency separation of the uplink from the downlink. Every time the ARFCN increases, the uplink will increase by 200 khz and the downlink also increases by 200 khz.

The given below table summarizes the frequency ranges, offsets, and ARFCNs for several popular bands.

Calculating Uplink/Downlink Frequencies

The following is a way to calculate the uplink and downlink frequencies for some of the bands, given the band, the ARFCN, and the offset.

GSM 900

Uplink = 890.0 + (ARFCN * .2) & Downlink = Up + 45.0

Example:

 Given the ARFCN 72, and we know the offset is 45MHz for the GSM900 band: Up = 890.0 + (72 * .2) Up = 890.0 + (14.4) Up = 904.40 MHz

Down = Up + Offset Down = 904.40 + 45.0 Down = 949.40 MHz

Advantage of CDMA Network

1      Larger Capacity :

let us discuss this issue with the help of Shannon’s Theorem. It states that the channel capacity is related to product of available band width and S/N ratio.

C         = W log 2 (1+S/N)

Where C         = channel capacity

            W        = Band width available

            S/N      = Signal to noise ratio.

It is clear that even if we improve S/N to a great extent the advantage that we are expected to get in terms of channel capacity will not be proportionally increased. But instead if we increase the bandwidth (W), we can achieve more channel capacity even at a lower S/N. That forms the basis of CDMA approach, wherein increased channel capacity is obtained by increasing both W & S/N. The S/N can be increased by devising proper power control methods.

2              Less (Optimum) Power per cell:

Power Control Methods: As we have already seen that in CDMA the entire bandwidth of 1.25Mhz is used by all the subscribers served in that area. Hence they all will be transmitting on the same frequency using the entire bandwidth but separated by different codes. At the receiving end the noise contributed by all the subscribers is added up. To minimize the level of interfering signals in CDMA, very powerful power control methods have been devised and are listed below:

1. Reserve link open loop power control

2. Reserve link closed loop power control

3. Forward link power control

The objective of open loop power control in the reverse link (Mobile to Base) is that the mobile station should adjust its transmit power according to the changes in its received power from the base. Open loop power control attempts to ensure that the received signal strength at the base station from different mobile stations, irrespective of their distances from the base site, should be same.

In Closed loop power control in reverse link, the base satation provides rapid corrections to the mobile stations’ open loop estimates to maintain optimum transmit power by the mobile stations. The base station measures the received signal strength  from the mobile connected to it and compares it with a threshold value and a decision is taken by the base every 1.25 ms to either increase or decrease the power of the mobile.

In forward link power control (Base to Mobile) the cell (base) adjusts its power in the forward link for each subscriber, in response to measurements provided by the mobile station so as to provide more power to the  mobile who is relatively far away from the base or is in a location experiencing more difficult environment.

These power control methods attempt to have an environment which permits high quality communication (good S/N) and at the same time the interference to other mobile stations sharing the same CDMA channel is minimum. Thus more numbers of mobile station are able to use the system without degradation in the performance. Apart from the capacity advantage thus gained power control extends the life of the battery used in portables and minimizes the concern of ill effects of RF radiation on the human body.

3              Seamless Hand-off :

CDMA provides soft hand-off feature for the mobile crossing from one cell to another cell by combining the signals from both the cells in the transition areas. This improves the performance of the network at the boundaries of the cells, virtually eliminating the dropped calls.

4              No Frequency Planning :

A CDMA system requires no frequency planning as the adjacent cells use the same common frequency. A typical cellular system (with a repetition rate of 7) and a CDMA system  is shown in the following figures which clearly indicates that in a CDMA network no frequency planning is required.

5         High Tolerance to Interference :

The primary advantage of spread spectrum is its ability to tolerate a fair amount of interfering signals as compared to other conventional systems. This factor provides a considerable advantage from a system point of view.

6              Multiple Diversity :

Diversity techniques are often employed to counter the effect of fading. The greater the number of diversity techniques employed, the better the performance of the system in a difficult propagation environment.

CDMA has a vastly improved performance as it employs all the three diversity techniques in the form of the following:

A .Frequency Diversity:          A wide band RF signal of 1.25 Mhz being used.

B. Space Diversity:     Employed by way of multipath rake receiver.

codes in CDMA

Walsh Code :

In CDMA the traffic channels are separated by uinique “Walsh” code. All such codes are orthogonal to each other. The individual subscriber can start communication using one of these codes. These codes are traffic channel codes and are used for orthogonal spreading of the information in the entire bandwidth. Orthogonality provides nearly perfect isolation between the multiple signals transmitted by the base station.

The basic concept behind creation of the code is as follows:

(a)        Repeat the function right

(b)        Repeat the function below

(c)                Invert function (diagonally)

0  -----  0          0 --------           0          0          0          0

             0         1                     0          1          0          1

                                                0          0          1          1

                                                0          1          1          0

Long code :

the long pseudo random noise (PN) sequence is based on 2⁴² characteristic polynomial. With this long code the data in the forward direction (Base to Mobile) is scrabled. The PN codes are generated using linear shift registers. The long code is unique for the subscribers and is known as users address mask.

Short Code :

The short pseudo random noise (PN) sequence is based on 2¹⁵ characteristic polynomial. This short code differentiates the cells & the sectors in a cell. It also consists of codes for I & Q channel feeding the modulator.

CDMA WLL SYSTEM IS 95

The Wireless Local Loop platform is a versatile supplement or substitute for wired local switching service. Based on IS-95 cdmaOne and 1XRTT, it possesses the quality, reliability and functionality of wired networks with the quick, cost-effective deployment associated with wireless access. It's an exceptionally powerful product for creating revenue. It is connected with mobile stations through air interfaces on one hand, and with Local Exchange(LE) through V5-interfaces on the other.

The WLL system enables complete transparency to the Local Exchange (LE) services, such as PSTN call, charging meters, reverse polarity, and variable data services.

            WLL consists of the following two primary components that are required to supply telecommunication services to subscribers:

1. BSC: The main controller of the WLL system. The BSC is connected to both the LE and radio base stations and can be located either at the LE building, another site close by, or at a remote location.

2. BTS: The radio base station that provides coverage for serviced area.

As the control part of the base station system, the BSC(base station controller) includes High-speed Interconnect Router Subsystem (HIRS), selector/vocoder bank subsystem (SVBS), call processing subsystem (CPS), base station management subsystem (BSM) and timing subsystem (TS). One end of the BSC is connected with the BTS through a CDSU, and the other end is connected with the LE through as SVICM, with the BSS system’s operation and maintenance performed at the BSC side. The BSC is mainly responsible for wireless network management, wireless resource management, BSS maintenance and management, call processing and control, MS handoff and voice coding.

The BTS(base transceiver system) is the wireless part of the BSS. It includes baseband digital subsystem (BDS), radio frequency subsystem (RFS) and timing frequency subsystem (TFS). Controlled by the BSC, the BTS realizes the wireless transmission and related control functions. Modules in the BDS are interconnected through the internal S_HIRS.

Call Processing Subsystem (CPS) in CDMA

The Call Processing Subsystem (CPS) is the hub for the BSS system’s resource management and call signaling protocol processing. The CPS contains only two modules — call processing module (CPM) and power alarm module (PAM). The CPM is connected to a port of the NIM module in the HIRS through an RS422 interface, and communicates with other subsystems in the BSC (including SVBS, BSM and the NCM module of the HIRS) and the BDS subsystem in the BTS via the HIRS.

Since the CPS does not contain many boards, it shares the same frame with the CDSU and GPSTM, as sketched in Fig

 Call Processing Module (CPM)

CPM is short for Call Processing Module. In the BSC of the CDMA WLL system, the CPM is responsible for call management. As the concentration point of SCWLL system management and signaling processing, its main functions are signaling processing of the Abis interface of the whole CDMA WLL system, wireless resource management and assignment, ground link resource management and V5 LAP data processing and V5 layer3 different protocols AN side implementation. Modularized design is employed on the hardware, and the advanced features of system realization, as well as various factors such as thermal design and electromagnetic compatibility design have been taken into consideration from the selection of components to PCB arrangement, so as to ensure board reliability. Due to the importance of the board in the whole system, the 1+1 hot backup mode is adopted. 

  Power Alarm Module (PAM)

The full name of the PAM board is Power Alarm Module. It is located in the BSC-side CDSU frame. Its main function is to monitor the running status of the power supply modules in the BSC-side frames and the equipment room environment signals, including temperature, humidity and smoke, and report the result to the background operation and maintenance console through the NCM for processing; in addition, the PAM board also provides duplex RS232 and RS485 interfaces for the connection of external monitoring devices and alarm box. 

 Channel Data Service Unit (CDSU)

In the SCWLL system, the interface between the BSC and BTS is called Abis interface. This interface links the BSC with the BTS through an E1 trunk line in the daisy chain mode. The CDSU board is the board module that implements the Abis interface functions. 

SVM - Selector & Vocoder Module

SVM (Selector & Vocoder Module) is the basis for the SVBS, and each SVM contains 15 vocoders. The SVMs are mainly responsible for the conversion between 64kb/s coding and QCELP coding. They are the center of voice data processing in the BSC. They support voice channels in soft handoff by means of multi-channel backward packet service data selecting function. They take part in backward outer-loop power control by means of backward FER statistics and adjustment of backward SNR threshold. Modularized design is employed on the hardware, and state-of-the-art technologies are adopted on the basis of careful analysis and studies. Product upgrading and development potentials, as well as various factors such as thermal design and electromagnetic compatibility design have been taken into consideration from the selection of components to PCB arrangement, so as to ensure the board reliability.

Basic Structure and Functions of SVM

The functions of SVM are briefly described as follows:

Main control unit:

Performs the control of SVE and data interface; implements selector and power control functions; fault detection and reporting;

Data interface unit:

Provides a packet data interface for the communication within the BSS system;

HW interface unit:

 Implements clock conversion and provides code flow data channel for SVE;

SVE:

Implements QCELP conversion, with 15 vocoders;

Clock, power supply and rest circuit:

 Implements clock and board reset of the main control unit, and provides all types of power supplies, including 5V, 3.3V and 2.5V. 

Network Interface Module (NIM)

 NIM is the short form of Net Interface Module, which is the interface unit for the access of various port devices in the SCWLL BSS system to the HIRS network. Based on the current overall design requirement, each HIRS frame of the BSC contains 18 NIM boards, of which 16 are working boards and two are standby boards, forming two N+1 backup systems. The active/standby switchover is implemented in the daisy chain mode. Each NIM board provides eight bi-directional 422 ports, with the supporting data rate being 8Mb/s. In addition, various clocks required for various devices, such as even second and chip signal, are also transmitted in form of differential signals through the 422 port of the NIM boards. 

   Basic structure and Functions of NIM

Control unit: Implements board startup, self-test, status error reporting, N+1 switchover etc.

DISCO logic: Transmits the data in the reception buffer to the UGATE of the NCM, or saves the data from the UGATE into the sending buffer.

HDLC logic: Receives the HDLC data frames from the CPM, NCM, SVICM or CDSU and save them into the buffer, or takes data from the sending buffer, converts them into the HDLC format and sends them to the CPM, NCM, SVICM or CDSU.

422 driving: Drives the HDLC data code flow, even second and CHIP signals.

GLTP driving: Drives the DISCO dual-bus data and control signals.

The NIM panel contains three indicators and one reset button, as shown in Figure 

RUN: A green indicator, blinking when the board works normally.

ALM: A red indicator, blinking in case of board failure.

ACT: A green indicator, lighting up when the board is in active state. 

Network Control Module (NCM) High-speed Interconnect Router Subsystem

The network control module (NCM) is the core module of the HIRS frame. At the same time, as a relatively independent unit, its CPU system is connected downward to an NIM port through an RS422 for the communication with other boards of the system to implement monitoring of the whole system. Its performance directly affects the HIRS and the whole system. For this reason, active/standby configuration is employed for it. In addition, error locating and automatic recovery technologies have been adopted in the design, and various factors such as thermal design and electromagnetic compatibility design have been taken into consideration from the selection of components to PCB arrangement, so as to ensure the stable and reliable working of the module

Basic Structure and Functions of NCM

U gateway unit: Implements dual-bus mediation and routing between the present frame and outgoing data.

ATM interface unit: Implements interconnection of inter-frame data, and provides interfaces for future expansion.

Main control unit: The CPU system, which implements dispatching of various modules’ software and configuration information; local device status modification notification and confirmation; maintenance of configuration database local copy; detection, isolation, reporting and recovery of HIRS network errors; HIRS network performance monitoring; reception of TOD broadcast data, control and maintenance of GPSR (GPS receiver); as well as operation and maintenance of the BSS system.

Clock power supply reset unit: Feeds the boards, and provides 1.5V supply to the back plane; clock driving and dispatching; board reset.

Main control logic unit: Implements active/standby competition and switchover, in-board status detection, control and reporting.

HIRS Network Subsystem CDMA

HIRS Network Subsystem  CDMA ( HIRS - High-speed Interconnect Router Subsystem)

The system structure of the whole HIRS adopts fast packet switching network based on shared storage (bus type) and hierarchical and modularized structure. A bus type packet switching network is based on two uni-directional buses — CO and DIS buses, which compose the framework of the HIRS network switching platform. The CO bus is contributing bus.

 Under the mediation and control of the U gateway of the NCM module, the NIMs send the data frames received from the RS422 port to the CO bus. After the U gateway receives the data frames from the CO bus, it distributes the data according to the data frame’s destination addresses: to the ATM or DIS bus. The DIS bus (Distribution BUS) is the broadcast distribution bus. Data frames from the directions of both the ATM interface and CO bus are sent to the DIS bus in the broadcast distribution mode under the

control of the U gateway. All the NIMs receive the broadcast data frames from on DIS bus simultaneously, and determine whether to accept the data frame based on the node number of the destination address. For accepted data frames, the NIM will further send the data frames to the corresponding RS422 port according to the port number of the data frame destination address. 

The HIRS network is composed of two HIRS frames. Each HIRS frame contains 22 slots. The two slots in the middle are NCM slots; nine slots at both sides of the NCM slots are for NIMs, and the NIMs at both ends serves as backup. The hardware structure of the HIRS subsystem is shown in Fig.

 

CDMA Interface

8.1.1          Descriptions of inter-entity interfaces

  Interface between MSC and BSS (A-interface)

In fact, it is the interface between MSC and BSC. Adopting 2Mb/s PCM digital link, the standard protocols for this interface include IS-634, IOS2.4, IOS4.0 etc.

A-interface is mainly used to transmit the following information:

1. BSS management information,

2. Call processing, and

3. Mobility management information.

 Interface between MSC and VLR (B-interface)

This interface is an internal interface, without standard definition. Its functions are as follows:

VLR is the location and management database for subscribers that have roamed into related MSC area. When the MSC needs the subscriber data of the particular MSC area, the MSC is to inquire the VLR; in the case of mobile station location updating, the MSC will request VLR to store the related information; when the user activates the supplementary services or modifies data, the MSC will request the HLR (through VLR) to store the related data.

This interface has no standard definition, and generally uses an internal interface.

 Interface between MSC and HLR (C-interface)

Interface between the MSC and the HLR.

The system adopts the IS-41E protocol. This interface is based on 2Mb/s digital interface or 64Kb/s interface, with its interface electrical performance conforming to GF002-9002.1 The General Technical Specifications for Telephone Switching Equipment of the Ministry of Posts and Telecommunications Volume 1 Digital SPC Switching Equipment General Technical Specifications Chapter 7 and GB7611-87 Pulse Coding Modulation Communication System Network Digital Interface Parameters; As for the signaling specifications, for detailed description of MAP, refer to Technical Requirements for 800MHz CDMA Digital Cellular Mobile Communication Network Mobile Application Part (MAP); for detailed description of SCCP, refer to GF010-95 Technical Requirements for National No.7 Signaling Mode Technical Specifications Signaling Connection Control Part (SCCP); for detailed description of MTP, refer to GF001-9001 China Telephone Network No.7 Signaling Mode Technical Specifications.

C-interface adopts 24-bit No.7 signaling mode.

  Interface between VLR and HLR (D-interface)

The system adopts the IS-41E protocol. This interface is based on 2Mb/s digital interface or 64Kb/s interface , with its interface electrical performance conforming to GF002-9002.1 The General Technical Specifications for Telephone Switching Equipment of the Ministry of Posts and Telecommunications Volume 1 Digital SPC Switching Equipment General Technical Specifications Chapter 7 and GB7611-87 Pulse Coding Modulation Communication System Network Digital Interface Parameters; As for the signaling specifications, for detailed description of MAP, refer to Technical Requirements for 800MHz CDMA Digital Cellular Mobile Communication Network Mobile Application Part (MAP); for detailed description of SCCP, refer to GF010-95 Technical Requirements for National No.7 Signaling Mode Technical Specifications Signaling Connection Control Part (SCCP); for detailed description of MTP, refer to GF001-9001 China Telephone Network No.7 Signaling Mode Technical Specifications.

D-interface uses 24-bit No.7 signaling mode.

This interface is used for switching of subscriber location information, authorization information and service data. The major service function of a mobile station is: it must have the capability of initiating and receiving calls within the service area. In order to support this capability, the HLR has to perform data switching. The VLR notifies the HLR about the subscriber location information, and provides the subscriber roaming number. The HLR sends the subscriber service data required by the VLR. The switching data usually occurs when a subscriber requests for a special service, or when a subscriber or network operator modifies the subscriber data.

  Interface between MSC and MSC (E-interface)

The system adopts the IS-41E protocol. This interface is based on 2Mb/s digital interface or 64Kb/s interface, with its interface electrical performance conforming to GF002-9002.1 The General Technical Specifications for Telephone Switching Equipment of the Ministry of Posts and Telecommunications Volume 1 Digital SPC Switching Equipment General Technical Specifications Chapter 7 and GB7611-87 Pulse Coding Modulation Communication System Network Digital Interface Parameters; as for the signaling specifications, for detailed description of MAP, refer to Technical Requirements for 800MHz CDMA Digital Cellular Mobile Communication Network Mobile Application Part (MAP); for detailed description of SCCP, refer to GF010-95 Technical Requirements for National No.7 Signaling Mode Technical Specifications Signaling Connection Control Part (SCCP); for detailed description of MTP, refer to GF001-9001 China Telephone Network No.7 Signaling Mode Technical Specifications.; the ISUP part is still to be defined.

E-interface adopts the 24bit No.7 signaling mode. Its functions are as follows:

When a mobile station roams from one MSC to another, the MSC will perform handoff in order to keep the subscribers’ conversation uninterrupted. In this case data switching must be implemented between the MSCs.

 Interface between MSC and EIR (F-interface)

This interface has no standard definition. Its functions are as follows:

When the mobile station is in communication, and the MSC authenticates the mobile station, it has to inquire the EIR, so as to determine whether the mobile station is legal, and thus deciding whether to provide services to this mobile station.

 Interface between HLR and AUC (H-interface)

Currently an internal interface is used. Its functions are as follows:

When the HLR receives an authentication request from an MS, the HLR gets data from the AUC. When the AUC initiates the authentication instruction to the MS, the AUC transfers the authentication information to the subscriber via the HLR.

  Interface between MC and SME and MC (M-interface)

Current the SMPP phase III standard is used. The interface’s function is as follows:

When the short message center performs information interaction with the short message entity and another short message center, this protocol must be abided by.

 Interface between HLR and MC (N-interface)

The interface standard is ANSI-41E. Its function is as follows:

When the short message center sends a short message to a subscriber, if the called subscriber’s address information is not available, it has to inquire the HLR for the subscriber’s route before it can send the short message to the subscriber.

  Interface between MC and MSC (Q-interface)

The interface standard is ANSI-41E. Its function is as follows:

During the submission and reception of a short message, short message transfer needs to be conducted between the short message center and mobile switching center. At the same time, when the subscriber’s short message capability changes, the mobile switching center needs to notify the short message center in time.

  Interface between MSC and OMC

This interface conforms to the network requirements of TMN, and provides standard Q3 interface to the upper-level TMN.

   Interfaces with PSTN/ISDN (Ai/Di Interfaces)

The CDMA digital cellular mobile network inter-works with PSTN/ISDN through the mobile switching center (MSC) and provides voice, data and certain supplementary services for subscribers. Its interfaces are 2048kb/s-based digital interfaces. TUP and ISUP of the SS7 signaling are adopted with priority as the interface signaling specifications. Where conditions are not available, China No.1 signaling can be used.

   Interfaces with Other PLMN Networks

The CDMA digital mobile network is normally connected with different types of PLMN networks (such as GSM) through other public networks (such as PSTN and ISDN), or directly connected with other types of PLMN networks. The adopted protocol can be TUP or ISUP, or China No.1 signaling. 

CDMA cellular mobile communication system

Base station subsystem (BSS)

Base station subsystem is the general term for the wireless devices and wireless channel control devices that serve one or several cells. Generally, a BSS contains one more base station controllers (BSC) and base transmitter stations (BTS).

 Mobile switch center (MSC)   

MSC is a functional entity that performs control and switching to the mobile stations within the area that it serves, and an automatic connecting device for the subscriber traffic between the CDMA network and other public networks or other MSCs. MSC is the kernel of the CDMA cellular mobile communication system, and it is different from a wired switch in that an MSC must consider the allocation of the wireless resources and the mobility of subscribers, and at least it must implement the follows processing activities:

1. Location Registration processing;

2. Handoff.

   Gateway MSC (GMSC)

When a non-CDMA subscriber calls a CDMA subscriber, the call will first be routed to an MSC, which will inquires the corresponding HLR and further route the call to the called party’s MSC. This kind of MSC is called Gateway MSC (GMSC). It is up to the network operator to select which MSCs as GMSCs.

  Visitor location register (VLR)

VLR is responsible for the storage and updating of the subscriber data of mobile stations that roamed to the service area of this VLR. The VLR is generally configured together with the MSC. When the mobile station enters a new location area, the MSC will notice the VLR, which will initiate registration processing to the HLR to update the subscriber location information. The VLR also stores necessary information for the establishment of calls in the database for the MSC to search. One VLR can cover one or more MSC areas. Specifically, the following information is included:

Service profile information (PROFILE)

Mobile identification number/international mobile subscriber identity (MIN/IMSI)

Shared secret data                       SSD

Electronic serial number (ESN)

Mobile station authentication data (AUTHEN)

Mobile station authorization data (AUTHOR)

Mobile station temporary local directory number (TLDN)

Mobile station location area information (LAI)

  Home location register (HLR)

The HLR provides subscriber information storage and management functions for the mobile network, including mobile subscriber subscription and cancellation and service authorization and cancellation. At the same time, it helps in the implementation of subscriber’s call and service operations. A CDMA can contain one or more HLRs based on the number of subscribers, equipment capacity and network organization mode, with multi-HLR mode realized in the form of virtual HLRs. The subscriber information stored in the HLR includes the following two types in information:

1. Subscription information

Some location information that enables the realization of call routing and accounting, such as VLR address, MSC address and local mobile station identity.

2. Subscriber-related information stored in the HLR

Mainly including:

Service profile information (PROFILE)

Mobile identification number/international mobile subscriber identity (MIN/IMSI)

Shared secret data SSD

Electronic serial number (ESN)

Mobile directory number (MDN)

IMSI/MIN and MDN are often used as key for access to the mobile subscriber database.

The HLR also contains the following mobile subscriber information:

Telecom services

Data services

IN services

Short message service data

Service restriction (such as roaming restriction)

Supplementary service parameters

  Authentication center (AUC)

Authentication center is a function entity for the management of authentication information related to the mobile station. It implement mobile subscriber authentication, stores the mobile subscriber authentication parameters, and is able to generate and transmit the corresponding authentication parameters based on the request from MSC/VLR. The authentication parameters in the AUC can be stored in the encrypted form. The authentication center is generally configured together with the HLR. The authentication parameter stored in the AUC include:

1. Authentication key (A_KEY);

2. Share secret data  (SSD);

3. Mobile identification number/international mobile subscriber identity (MIN/IMSI);

4. Authentication algorithm (AAV);

5. Accounting (COUNT).

   Short message center (MC or SC)

As an independent entity in the CDMA cellular mobile communication system, the short message center works in coordination with other entities such as MSC, HLR to implement the reception, storing and transfer of the short messages from CDMA cellular mobile communication system subscribers, and store subscriber-related short message data. 

  Short message entity (SME)

SME is a function entity for synthesis and analysis of short messages.