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.

corDECT Wireless Access System

Following the conceptual model, the corDECT Wireless Access System uses a similar architecture to provide telephone and Internet service to a subscriber, as shown The subscriber premises equipment, Wallset IP (WS-IP)

could also incorporate switching maintenance functions when required. Further, is possible to co-locate lnternet servers with Ea AC.

The subscriber premises equipment, Wallset IP (WS-IP) or Wallset (WS), bias a wireiess Connection through a Compact Base Station CBS) to an Access Switch, called a DECT Interface Unit (DIU). The air interface is compliant c) the DECT standard specified by ETSI. The )IU switches the voice traffic to the telephone I network using the V5.2 protocol to connect to in exchange. The DIU also switches the Internet built-in Remote Access Switch(which then routes the traffic to the Int network. The Ras has an Ethernet into which is connected to the Internet using suitable routing device.

The CBS is normally connected to the DIU three twisted-pair wires, which carry sign well as power from the DIU to the Alternatively, it can be connected to through a Base Station Distributor (BSD BSD is remote unit connected to the DIU a standard E1 interface ( on radio, fibre, A BSD can sup to four CBS’s.

The long range communication, a WS is can also be connected to the CBS using hop DECT wireless link, one between V WS and a Relay Base Station (RBS) and between the RBS and CBS, The wireless range supported be WS 0 Ip or WS and the CBS or RBS is

line-of-Sight (LOS)'conditions. The range supported between a CBS and RBS is 25 km in LOS conditions. 

A typical system consists of one DIU with one or two RAS units, up to 20 CBS'S, and up to a 1 000 WS-IP's or WS's. The BSD and RBS units are used as required by the deployment scenario.

The Network and Switching Subsystem

Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, fixed telephony users, etc. It also includes data bases needed in order to store information about the subscribers and to manage their mobility. The different components of the NSS are described below. 

The Mobile services Switching Center (MSC)
It is the central component of the NSS. The MSC performs the switching functions of the network. It also provides connection to other networks.

  The Gateway Mobile services Switching Center (GMSC)

A gateway is a node interconnecting two networks. The GMSC is the interface between the mobile cellular network and the PSTN. It is in charge of routing calls from the fixed network towards a GSM user. The GMSC is often implemented in the same machines as the MSC.

Home Location Register (HLR)

The HLR is considered as a very important database that stores information of the subscribers belonging to the covering area of a MSC. It also stores the current location of these subscribers and the services to which they have access. The location of the subscriber corresponds to the SS7 address of the Visitor Location Register (VLR) associated to the terminal.

Visitor Location Register (VLR)

The VLR contains information from a subscriber's HLR necessary in order to provide the subscribed services to visiting users. When a subscriber enters the covering area of a new MSC, the VLR associated to this MSC will request information about the new subscriber to its corresponding HLR. The VLR will then have enough information in order to assure the subscribed services without needing to ask the HLR each time a communication is established.
The VLR is always implemented together with a MSC; so the area under control of the MSC is also the area under control of the VLR.

The Authentication Center (AuC)

The AuC register is used for security purposes. It provides the parameters needed for authentication and encryption functions. These parameters help to verify the user's identity.

The Equipment Identity Register (EIR)

The EIR is also used for security purposes. It is a register containing information about the mobile equipments. More particularly, it contains a list of all valid terminals. A terminal is identified by its International Mobile Equipment Identity (IMEI). The EIR allows then to forbid calls from stolen or unauthorized terminals (e.g., a terminal which does not respect the specifications concerning the output RF power).

 The GSM Inter-working Unit (GIWU)

The GIWU corresponds to an interface to various networks for data communications. During these communications, the transmission of speech and data can be alternated. 

Call re-establishment

Call re-establishment enables the mobile station to resume the contact with the cellular network when the connection to a particular VBTS is suddenly broken. This may happen because of a brutal propagation loss, due to obstacles such as bridges and tunnels.

Call re-establishment is a GSM feature that can be enabled or disabled on a per cell basis.

   Call re-establishment process : After the communication has been lost, the mobile station selects the cell with the highest signal strength from the neighbor cell list. The neighbor cell list contains the cell identifiers to which a handover is allowed. It is kept in the BSC of a particular cell. The list is transferred to the mobile station in the BCCH during the registration phase of a wireless call. The mobile station uses the neighbor cell list by only measuring the signals from the BTSs located in the cells that are on the list.

The selected cell identifier is used to re-establish the connection to that particular cell by following the normal access procedures. Actually, it sends an access request on the RACH (Random Access Channel) of the particular frequency channel.

At the moment of time the communication is lost, a timer is initiated in the serving MSC. When the timer expires, it is not possible anymore for the mobile station to re-establish the call. A typical value for the timer is 4 seconds

What is a cell?

A cell is a base transceiver service area as seen by the mobile station (MS). A cell uses a specific set of frequencies.

  

There are two  types of cells:

Omni cells:

An omni cell is a cell where the antenna transmits omni-directional. The coverage area of an omni cell is in principle a hexagon/circle, but in reality a rough pattern.

Sector cells:

A sector cell is a cell where the antenna transmits directional. 

Examples of sector cell types are:

-           2-sector cells (e.g. for highways)

-           3-sector cells.

The following figure shows examples of different cell types

  Sector vs. omni cells

Advantages of sector cells are (compared to omni cells):

•           Increased coverage area per site (by the use of higher gain antennas)

•           Possibility of mechanical tilting antennas (to reduce unwanted interference)

•           Simpler antenna mounting (reduced clearance to prevent interaction with other antennas).

Disadvantages of sector cells are:

•           More equipment required at each site

•           Greater environmental impact (more antennas)

•           Longer frequency re-use distance for a given C/I

•           Increased cell handovers.