prepaid wire

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Prepaid Wireless Service Billed inReal Time

Definition

Prepaid wireless service requires payment from the subscriber before wirelessproviders will extend service. Real-time billing debits the prepaid subscriber'saccount as the prepaid subscriber uses service and prevents the prepaidsubscriber from exceeding the account's available balance.

Overview

Transmission control protocol (TCP)/Internet protocol (IP) and signaling system7 (SS7) networks are designed to provide reliable communications betweenservice nodes 365 days a year, seven days a week, and 24 hours a day. The wireless intelligent network (WIN) uses the existing TCP/IP and SS7 networkinfrastructures in combination with the American National Standards Institute(ANSI)–41 standard to allow wireless providers to offer the enhanced servicesmade possible by an intelligent network without the expense of deploying a new

network infrastructure.

One such enhanced service is real-time billing for prepaid accounts. Real-time billing decreases the wireless provider's credit exposure due to prepaid accounts while offering the prepaid subscriber the ease of a prepaid account that mirrorspostpaid convenience.

After completing this tutorial, the reader will understand how the WIN enables a wireless provider to bill prepaid accounts in real time when the subscriber islocated in the home area. The reader is expected to be familiar with networking,signaling, and telecommunication technologies and standards.

Topics1. Network Architecture

2. Positive-Balance Call Origination

3. Positive-Balance Call Termination

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4. Mid-Call Zero Talk Time at Home

5. Zero Talk Time at Home

Self-Test

Correct Answers

Glossary

1. Network Architecture

The network architecture of a WIN platform links signal switching points (SSP),signal transfer points (STP), and signal control points (SCP). The WIN platformrests upon the SS7, TCP/IP, and voice networks. Serving Mobile ServicesSwitching Center (S_MSC): The S_MSC is the interface between the radio systemand the public switched telephone network (PSTN). The S_MSC provides thetransport and translation support for call origination from and termination to the

subscriber.

Signal Transfer Point (STP): The STP is a SS7 network packet switch thatroutes SS7 messages to the proper destination.

Signaling Interface Unit (SIU): The SIU converts SS7 messages into TCP/IP.The SIUs are redundantly deployed to provide alternate paths for greaterreliability.

ISUP Call Control Unit (ICC): The ICC is the gateway between the SIU andthe SCP's intelligent peripheral. The ICC directs messages to the properdestination.

Remote Service Unit (RSU): The RSU is an intelligent peripheral co-located with the S_MSC. The RSU is an adjunct switch that controls the prepaid calls andprocesses integrated voice response (IVR) messages.

Market Server: The market server contains the subscriber database and servesas the call rating engine.


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Figure 1: Network Architecture

2. Positive-Balance Call Origination

The prepaid subscriber initiates a call within the home area. When the S_MSCdetects the origination attempt, it sends an origination request invoke message(ORREQ) to its remote service unit (RSU). The RSU determines that the mobile

identification number (MIN) is a prepaid account and queries the market serverfor talk time available to this account. The market server calculates the availabletalk time and forwards it to the RSU.

The RSU sends an origination request return result message (orreq) to theS_MSC to indicate that call processing can continue. The S_MSC attempts toconnect the call. When the S_MSC detects an answer, it sends an originationanswer message (OANSWER) to the RSU. The RSU begins timing the call, andthe call is connected.

The subscriber ends the call. The S_MSC sends an origination disconnect invokemessage (ODISCONNECT) to the RSU. The RSU stops timing the call and sendsthe call duration to the market server. The market server prices the call anddecrements the subscriber's account. The RSU sends an origination disconnectreturn result message (odisconnect) to the S_MSC, and the S_MSC releases thecall.


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Figure 2: Positive-Balance Call Origination

3. Positive-Balance Call Termination A call arrives at the S_MSC for the prepaid subscriber. Recognizing thesubscriber's ID, the S_MSC sends a location request invoke message (LOCREQ)to its home location register (HLR). The HLR returns a location request returnresult message (locreq) to the S_MSC, indicating that the S_MSC should send an ANLYZD to the RSU.

Upon receipt of the ANLYZD from the S_MSC, the RSU queries the marketserver to determine if the MIN is a prepaid account and, if so, the amount of talktime available to the MIN. The market server validates the MIN, calculates the

available talk time, and forwards the available talk time to the RSU. The RSUsends an anlyzd to the S_MSC to indicate that call processing can continue. TheS_MSC routes the call to the subscriber.

The RSU starts timing the call when the subscriber answers. The calling party isthen connected to the subscriber.


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When the subscriber ends the call, the S_MSC sends a termination disconnectinvoke message (TDISCONNECT) to the RSU. The RSU stops timing the call andsends the call duration to the market server. The market server prices the call anddecrements the subscriber's account. The RSU sends a termination disconnectreturn result message (tdisconnect) to the S_MSC. The S_MSC releases the call.

Figure 3: Positive-Balance Call Termination

4. Mid-Call Zero Talk Time at Home

The prepaid subscriber initiates a call within the home area. When the S_MSCdetects the origination attempt, it sends an ORREQ to its RSU. The RSUdetermines that the MIN is a prepaid account and queries the market server fortalk time available to this account. The market server calculates the available talktime and forwards it to the RSU.

The RSU sends an orreq to the S_MSC to indicate that call processing cancontinue. The S_MSC attempts to connect the call. When the S_MSC detects ananswer, it sends an OANSWER to the RSU. The RSU begins timing the call, andthe call is connected.


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During the call, the RSU detects that the subscriber's balance has reached the lowthreshold. The RSU then sends a CCDIR to the S_MSC, indicating that thesubscriber should hear the low-balance warning. The S_MSC plays the low- balance warning to the subscriber. The S_MSC responds to the RSU with accdir to indicate that the low-balance warning was played.

The subscriber ends the call. The S_MSC sends an ODISCONNECT to the RSU.The RSU stops timing the call and sends the call duration to the market server.The market server prices the call and decrements the subscriber's account. TheRSU sends an odisconnect to the S_MSC and the S_MSC releases the call.

Figure 4: Mid Call Zero Talk Time

5. Zero Talk Time at Home

The prepaid subscriber initiates a call within the home area. When the S_MSCdetects the origination attempt, it sends an ORREQ to its RSU. The RSU


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determines that the MIN is a prepaid account and queries the market server fortalk time available to this account. The market server returns zero availableminutes of talk time to the RSU.

The RSU sends an orreq to the S_MSC to indicate zero talk time and the need toplay the insufficient balance announcement. The S_MSC plays the insufficient balance announcement to the subscriber and releases the call.

Figure 5: Start of Call Zero Available Minutes

Self-Test

1. Real-time billing of prepaid accounts decreases the wireless provider's creditexposure.

a. True

b. False

2. The ______________ is a SS7 network packet switch.

a. SIU

b. ICCc. STP

d. S_MSC

3. The _______________ is an adjunct switch that controls prepaid calls andprocesses IVR messages.


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a. ICC

b. SIU

c. RSU

d. Market Server

4. When the S_MSC detects an origination attempt, it sends an _______________ to the RSU.

a. orreq

b. ODISCONNECT

c. OANSWER

d. ORREQ

5. The RSU does not allow the S_MSC to connect the call if the prepaid account balance is sufficient to make the call.

a. True

b. False

6. Before terminating a call to the subscriber, the S_MSC must first:

a. start timing the call

b. calculate the available talk time

c. send a LOCREQ to its HLR

d. send an ANLYZD to the RSU

7. If the subscriber's account reaches zero during a call, the S_MSC does notdisconnect the call.

a. True

b. False

8. The _______________ message directs the RSU to stop timing the call.

a. ORREQ

b. ODISCONNECT


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c. CCDIR

d. Odisconnect

9. If a subscriber attempts to make a call with a zero account balance, theS_MSC connects the call.

a. True

b. False

10. The WIN platform rests upon the following network(s):

a. SS7

b. TCP/IP

c. Voice

d. All of the Above

Correct Answers

1. Real-time billing of prepaid accounts decreases the wireless provider's creditexposure.

a. True

b. False

See Overview

2. The ______________ is a SS7 network packet switch.

a. SIU

b. ICC

c. STP

d. S_MSC

See Topic 1

3. The _______________ is an adjunct switch that controls prepaid calls andprocesses IVR messages.


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a. ICC

b. SIU

c. RSU

d. Market Server

See Topic 1

4. When the S_MSC detects an origination attempt, it sends an _______________ to the RSU.

a. orreq

b. ODISCONNECT

c. OANSWER

d. ORREQ

See Topic 2

5. The RSU does not allow the S_MSC to connect the call if the prepaid account balance is sufficient to make the call.

a. True

b. False

See Topic 2

6. Before terminating a call to the subscriber, the S_MSC must first:

a. start timing the call

b. calculate the available talk time

c. send a LOCREQ to its HLR

d. send an ANLYZD to the RSU

See Topic 3

7. If the subscriber's account reaches zero during a call, the S_MSC does notdisconnect the call.


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a. True

b. False

See Topic 4

8. The _______________ message directs the RSU to stop timing the call.

a. ORREQ

b. ODISCONNECT

c. CCDIR

d. Odisconnect

See Topic 2

9. If a subscriber attempts to make a call with a zero account balance, theS_MSC connects the call.

a. True

b. False

See Topic 5

10. The WIN platform rests upon the following network(s):

a. SS7

b. TCP/IP

c. Voice

d. All of the Above

See Topic 1

Glossary ANSI American National Standards Institute

HLRHome Location Register


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ICCISUP Call Control Unit

IVRIntegrated Voice ResponseLOCREQLocation Request Invoke Message

locreqLocation Request Return Result Message

MINMobile Identification Number

OANSWEROrigination Answer Message

ODISCONNECTOrigination Disconnect Invoke Message

odisconnectOrigination Disconnect Return Result Message

ORREQOrigination Request Invoke Message

orreqOrigination Request Return Result Message

PSTNPublic Switched Telephone Network

RSUservice node

Remote Service UnitSignal Interface Unit

S_MSCServing Mobile Switching Center

SCPSignal Control Point

SS7Signaling System 7

SSP


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Signal Switching Point

STPSignal Transfer Point

TCP/IPTransmission Control Protocol/Internet Protocol

TDISCONNECTTermination Disconnect Invoke Message

tdisconnectTermination Disconnect Return Result Message

WIN Wireless Intelligent Network

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