EXHIBIT A

Case 6:20-cv-00458-ADA Document 1-1 Filed 06/02/20 Page 1 of 11
United States Patent 

USOO7388868B2 

(12) (10) Patent No.: US 7,388,868 B2 

O'Connell et al. (45) Date of Patent: Jun. 17, 2008 

(54) CALL-ROUTING APPARATUS, AND 5,418,776 A 5/1995 Purkey et al. 

ASSOCIATED METHOD, FOR PROVIDING 5,661,779 A 8, 1997 Lee 

LOCAL CALL HANDLING FUNCTIONS IN A 6,058,178 A * 5/2000 McKendry et al. ... 379/212.01 

COMMUNICATION NETWORK 6,130,892 A * 10/2000 Short et al. ................. 370/401 

2001/0012343 A1* 8, 2001 Dal Molin ............. 379,100.12 

2003/0142682 A1* 7/2003 Bressoud et al. ........... 370/401 

(75) Inventors: E.E."x"Say 2003/0152210 A1* 8/2003 Delaney et al. ........ 379,220.01 

HallUS, ano, ; E. Sabu s IVlan, Since". Flano, FOREIGN PATENT DOCUMENTS 

TX (US) WO WO 96/21989 A T 1996 

WO WOOO,31933. A 6, 2000 

(73) Assignee: Alcatel Lucent, Paris (FR) 

* cited by examiner 

(*) Notice: Subject to any disclaimer, the term of this 

patent is extended or adjusted under 35 Primary Examiner Wing Chan 

U.S.C. 154(b) by 792 days. Assistant Examiner Prenell Jones 

(21) Appl. No.: 10/321,230 (57) ABSTRACT 

(22) Filed: Dec. 17, 2002 Emergency call-routing apparatus, and an associated 

(Under 37 CFR 1.47) method, for use in a packet-based, telephonic network. An 

emergency call router is positioned selectably to provide 

(65) Prior Publication Data local call handling functionality to a local network that is 

US 2004/0114611 A1 Jun. 17, 2004 normally connected by way of an access gateway to the • s telephonic network whose operation is normally controlled 

(51) Int. Cl. by a SoftSwitch. The apparatus is used when, e.g., a total 

H04L 2/28 (2006.01) communication link failure condition occurs between the 

H04L 2/56 (2006.01) access gateway and the softswitch. The emergency call 

(52) U.S. Cl. ...................................................... 040 router selectably routes calls within the local network to 

(58) Field of Classification Search 37O/4O1 permit continued, local calling functionality in spite of the 

37O/237, 3563893 95.352.37 9/374 9. failure of the communication link. High-priority calls, such 

379/.4645 20 265 220 266 93 29. 709,229. as calls placed to an emergency dispatch center, are routed 

709/245 230 238 203. 455,404. 445 456. within the local network to a designated, local-network 

s s s s s 4 55 /521 station. And local calls are also selectably routed by the 

S lication file f let h hist emergency call router. A call priority Scheme is also used in 

ee appl1cauon Ille Ior complete searcn n1story. the event that call capacity is exceeded. Calls of higher 

(56) References Cited priority are permitted while calls of lower priority are 

U.S. PATENT DOCUMENTS 

5,253,288 A 10, 1993 Rosenbluth et al. 

Detector 62 

Priority list 

Emergency 

Cal Router 

blocked. 

18 Claims, 3 Drawing Sheets 

 

 

 

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US 7.388,868 B2 

?8 

| ss

U.S. Patent 

 

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U.S. Patent Jun. 17, 2008 Sheet 2 of 3 US 7.388,868 B2 

24 24 16-1 42 48 

76 -- 4. 

78 

56 

-h 84 

CALL 

FIG. 2 

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U.S. Patent Jun. 17, 2008 Sheet 3 of 3 US 7,388,868 B2 

FIG. 3 

Detect Failure Of 

Normal-Operation 

Communication Link 

Selectably Route Ca 

Of The Selected-Call 

Type Via Substitute 

Call Router 

FIG. 4 

 

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US 7,388,868 B2 

1. 

CALL-ROUTINGAPPARATUS, AND 

ASSOCIATED METHOD, FOR PROVIDING 

LOCAL CALL HANDLING FUNCTIONS IN A 

COMMUNICATION NETWORK 

The present invention relates generally to a manner by 

which to route a call in a packet-based, or other, commu 

nication system. More particularly, the present invention 

relates to apparatus, and an associated method, by which to 

provide at least selected rudimentary local call handling 

functions. The call handling is provided at a local network 

associated with an access gateway upon total failure of a 

communication link between the access gateway and a 

softswitch which controls operations of the system. An 

emergency call router is provided that is operable upon 

detection of occurrence of the failure of the communication 

link. The call router provides at least selected, rudimentary 

local handling functions that otherwise would not be per mitted due to the failure of the communication link. Routing of a priority call. Such as a call to an emergency service 

position located beyond the local network, that would not be 

completed due to the failure of the communication link, can 

be routed, instead, by the call router to a substitute service 

position. And, call handling of selected lower-priority calls 

is also provided by the emergency call router. 

BACKGROUND OF THE INVENTION 

The use of communication systems through which to 

communicate data is an endemic part of modem Society. Telephonic communication systems are, perhaps, best exem 

plary of communication systems that have been widely 

employed and are regularly utilized by large numbers of USCS. 

In a telephonic communication system, telephonic com 

munication of Voice, as well as non-voice, data is generally provided. Telephonic communication networks have been 

installed throughout significant portions of the world, and 

users communicate telephonically therethrough by way of 

telephonic, or other communication, stations connected to 

the telephonic networks. 

Conventionally, telephonic networks provide for circuit 

Switched communications between telephonic stations that are to be connected to effectuate a communication session 

therebetween. When a circuit-switched connection is 

formed, a dedicated channel is provided to permit the 

telephonic communications between the telephonic stations, 

a calling party and at least one called party, is provided. For 

So long as the connection is maintained, telephonic commu 

nications between the telephonic stations is permitted. As 

data forming the telephonic communication might only be 

intermittently communicated between the telephonic sta 

tions during the communication session effectuated by way 

of the circuit-switched connection, the communication 

capacity of communication channels defined upon the cir 

cuit-switched connection might well not be fully utilized. 

Use of circuit-switched connections, formed in a telephonic 

network, as a result, inefficiently utilizes the communication 

capacity of a telephonic network. 

Communication schemes which provide for shared-chan 

nel communications, in contrast, more efficiently utilize the 

communication capacity of a communication system, Such 

as a telephonic communication system. Packet-based com 

munication systems, for instance, utilize shared channels 

upon which to communicate packet-formatted data. When a 

shared channel is utilized, more than one communication 

session is effectuable upon a single shared channel. Because 

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packet-formatted data can be communicated during discrete 

intervals, the same channel can be utilized to communicate 

packet-formatted data, during separate time periods to effec 

tuate communication services pursuant to separate commu 

nication sessions. More efficient utilization of the commu 

nication capacity of a communication system is thereby 

possible, in contrast, to conventional circuit-switched com 

munication schemes. 

Various packet formatting protocols are used when form 

ing, and sending, data packets formed of digital data bits. 

One protocol scheme, the Internet protocol (IP), or IP 

protocol, is regularly utilized in many different communi 

cation systems and communication applications. Communi 

cation devices and apparatus constructed to send, receive, 

transport, and operate upon IP-formatted data can be con 

figured together in a communication system to provide for 

the communication of IP-formatted data. 

Next-generation telephonic communication systems now 

being developed include telephonic networks that are predi 

cated upon packet-based communications. In such next 

generation systems, voice, non-voice, and multimedia com 

munication services shall be effectuable through the use of 

packet-based communications, using IP-formatted data. 

Such a new-generation telephonic network generally 

includes a packet data network, or fabric, through which 

packet-switched channels are formed. Devices referred to as 

gateways are coupled to the packet data network. Devices 

referred to as gateways form gateways to the packet data 

network. Gateways are operable, amongst other things, to 

form gateways to the packet data network from local net 

works. When communications in a local network are effec 

tuated using a different type of communication protocol than 

the protocol used in the packet data network, the gateway 

connecting the local network to the packet data network 

performs protocol translation, as well as, perhaps, also voice 

encoding operations. 

For instance, a local network might form a legacy, TDM 

(time division multiplexed) network. The call handling 

procedures of the local network would therefore be different 

than that of a packet-based network. 

Operational control of the telephonic communication sys 

tem is effectuated by a softswitch that functionally forms a 

part of, or is connected to, the packet data network. The 

SoftSwitch operates to control connection services of the 

gateways, operates to control call routing based upon sig 

naling information and database information related to the 

calling party and called party. 

Public safety answering points are amongst the commu 

nication devices that can be connected to a packet data 

network by way of a gateway. An emergency dispatch center 

is, for instance, the location to which an emergency call, 

such as a "911 call in the United States is routed. Such a call 

is originated at a calling station located at a local network, 

through a gateway connecting the local network to the 

packet data network, through the packet data network, to the 

gateway to which the public service access point is located. 

While the new-generation, telephonic networks include 

various redundancies, such as redundant SoftSwitches, in the 

event of total failure of a communication link between the 

gateway to which the local network is coupled and a 

softswitch associated with the packet data network, the call 

originated at the telephonic station of the local network 

cannot be routed to the public safety answering point. Other 

calls analogously originated at the telephonic station of the 

local network also cannot be completed. Included amongst 

the additional calls that cannot be completed are calls to a 

called party, i.e., the terminating station, at the local net 

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work. That is to say, even if a local call is to be originated 

and terminated entirely within a local network, the new 

generation telephonic communication system would not be 

able to complete such a call. 

Calls within the local network could still be completed in 

spite of the total failure of the communication link, but for 

the external control provided only by the softswitch in the 

next-generation system. That is to say, the call handling 

functionality provided by the softswitch, but unavailable due 

to the failure of the communication link, prevents continued 

operation of calls within the local network. 

If a manner could be provided by which to provide local 

call control in the event of failure of a communication link, 

at least limited communications within the local network 

could still be effectuable. And, if the local calls could still be 

effectuable, a call originated at the local network for termi 

nation at the public safety answering point could be routed, 

instead, to a local-network, telephonic station thereby to 

complete the call another party. 

It is in light of this background information related to 

packet-based, telephonic communication systems that the 

significant improvements of the present invention have 

evolved. 

SUMMARY OF THE INVENTION 

The present invention, accordingly, advantageously pro 

vides call-routing apparatus, and an associated method, by which to provide at least rudimentary call routing functions 

to route a call in a packet-based, or other, communication 

system. 

Through operation of an embodiment of the present 

invention, local call handling at a portion of the communi 

cation system associated with an access gateway is provided 

Subsequent to total failure of a communication link at a point 

beyond the access gateway and a SoftSwitch. Local call 

control is provided to the local network, Such as at the access 

gateway, Subsequent to failure of the communication link. 

Local calling between telephonic station associated with the 

access gateway is provided by way of an emergency call 

router in substitution for the softswitch that normally would 

otherwise control calling functions. And, when a call is 

placed by a calling party positioned in the local network to 

be terminated at a remote public safety answering point, 

detection of the call at the emergency call router permits the 

call to be routed to a substitute station, thereby to permit the 

calling party to report to at least a Substitute calling station 

so that a response thereto can be initiated by personnel positioned at the Substitute calling location. 

In one aspect of the present invention, a detector is 

provided to an access gateway for detecting the occurrence 

of a communication link failure of a communication link 

extending beyond the access gateway and to the Softswitch. 

When the communication link fails, control functions pro vided by a softswitch are not able to be provided to tele 

phonic stations associated with the access gateway. And, call 

connections requested by a calling party cannot be com 

pleted. When the detector detects the failure of the commu 

nication link, the emergency call router becomes operational 

to provide at least rudimentary local call control and han 

dling functions. In one implementation, the Substitute call 

router is embodied together with the access gateway. And, in 

another implementation, the call router forms a stand-alone 

unit permitting its connection to a gateway, or an aggrega 

tion point of more than one gateways. And, in a further 

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implementation, the emergency call router also includes an 

additional voice call capability, Such as that provided by a 

portable cellular phone. 

Because local call control functions are provided by the 

emergency call router, calls within the local network are at 

least selectably effectuable. 

In another aspect of the present invention, when the 

emergency call router becomes operational, due to the 

detection of the failure of the communication link, a tele 

phonic station within the local network is selected, or 

otherwise designated, to be an emergency receiving station. 

The detection may be either automatically made or manually 

made. Calls originated by another calling party within the 

local network are routed by the call router to the selected 

telephonic station. Calls originated by the calling party that 

would be routed during normal telephonic system operation, 

to a public safety answering point, are instead routed to the 

selected telephonic station. Through appropriate positioning 

of personnel at the selected telephonic station, a request for 

assistance initiated by the calling station is able thereby at 

least to be delivered locally to personnel associated with the 

selected telephonic station. 

In another aspect of the present invention, an alternate 

calling mechanism provided by a cellular, or other radio 

telephonic device, also is embodied at the emergency call 

router. Personnel positioned at the emergency call router are 

thereby able to establish voice connections by way of the 

radiotelephonic device. And, more elaborately, Switching 

functionality can also be provided by the alternate calling 

mechanism. 

In another aspect of the present invention, a listing is 

maintained at the emergency call router of priorities to be 

associated with the type of call that is made while the 

substitute call router is operable to perform call control 

operations. The call-types include, for instance, emergency 

calls, such as calls that are placed to the public service access 

point, calls placed to published lower-digit, such as three 

digit, service centers, calls placed to from priority parties, 

and finally, low-priority, local calls. Additional listings pri oritizing calls placed upon the identities of the calling parties 

can also alternately, or additionally, be utilized. When a call 

is routed to the emergency call router, access is made to the 

listing and comparison between the appropriate indicia of 

the call request and the prioritization of call-types contained 

in the listing. Calls are selectably permitted, or prevented, 

from routing within the local network responsive to the 

priority listing. And, calls are terminated, if necessary, by the 

call router if a higher-priority call is placed by a calling party 

and capacity in the local network is unavailable, but lower 

priority calls are in process, the call router selectably ter 

minates one, or more, of the lower-priority calls to permit the higher-priority call to be completed. 

Thereby, in spite of the total failure of the communication 

link between the access gateway and the SoftSwitch, local 

call control functionality is provided to permit at least 

limited communication in the local network associated with 

the access gateway. A calling party located in the local 

network is thereby also able to place a call to a designated 

emergency telephonic station. 

In these and other aspects, therefore, apparatus, and an 

associated method, is provided for a communication system 

having a communication network. The communication sys 

tem is controlled by a communication system controller also 

connected to the communication network. And, the commu 

nication network is connectable to an originating station 

operable to originate a call of at least a first selected call-type 

therefrom. The call is routable by way of a normal-operation 

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communication link. Call completion of the call is facilitated 

when the call is of at least a first selected call-type and 

Subsequent to failure of the normal-operation communica 

tion link. An emergency call router is at least coupled to the 

access gateway. The emergency call router selectably oper 

ates responsive to failure of the normal-operation commu 

nication link for routing the call of the first selected call 

type, thereby to facilitate call completion of the first selected 

call-type originated by the origination station. 

A more complete appreciation of the present invention 

and the scope thereof can be obtained from the accompa nying drawings that are briefly Summarized below, the 

detailed description of the presently preferred embodiments 

of the invention, and the appended claims. 

BRIEF DESCRIPTION OF THE DRAWINGS 

FIG. 1 illustrates a functional block diagram of a packet 

based, telephonic communication system in which an 

embodiment of the present invention is operable. 

FIG. 2 illustrates a message sequence diagram represen tative of signaling generated during exemplary operation of 

the telephonic communication system shown in FIG. 1 

Subsequent to failure of a communication link. 

FIG. 3 illustrates a functional block diagram of a portion 

of a telephonic communication network, analogous to the 

telephonic communication network forming part of the 

system shown in FIG. 1, here to represent the portability of 

the substitute call router of an embodiment of the present invention. 

FIG. 4 illustrates a method flow diagram listing the 

method of operation of an embodiment of the present 

invention. 

DETAILED DESCRIPTION 

Referring first to FIG. 1, a telephonic communication 

system, shown generally at 10, operates to provide for 

communications between communication stations, here tele 

phonic stations, that are connected to, or otherwise operable in, the communication system. In the exemplary implemen 

tation, the communication system includes a next-genera 

tion, packet data network (PDN) 14. The network 14 is 

sometimes referred to as the communication fabric of the 

communication system. The network 14 here forms a packet network capable of communicating packet-formatted data. 

Communication of Voice data, non-voice data, and combi 

nations of different types of data is provided by the com 

munication fabric formed of the packet data network. 

A plurality of gateways, here access gateways (AGWS) 16 

are coupled to the packet data network. Here, four exem 

plary gateways, gateways 16-1, 16-2, 16-3, and 16-4, are 

shown to be directly connected to the packet data network, 

here represented by way of communication links 18. While 

separately identified for purposes of illustration, the gate 

ways form integral parts of the network. The communication 

links 18 are functionally represented in the figure, and the 

communication links are actually representative of any 

portion of a communication link extending beyond the 

respective gateway and through the packet data network. 

The communication link 18-1 extends beyond the gateway 

16-1, the communication link 18-2 extends beyond the 

gateway 16-2, the communication link 18-3 extends beyond 

the gateway 16-3, and the communication link 18-4 extends 

beyond the gateway 16-4. Other communication links can 

analogously be represented. More generally, the failure can 

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be of any type that interrupts normal communications 

through the absence of call control functionality. 

The access gateway 16-4 here is connected to the network 

14 by way of an aggregation location or point 20 to which 

other gateways or other functional devices are connected. 

Additional gateways, gateways 16-5 and 16-6, are coupled 

to the aggregation point 20 and are connected to the packet 

data network therethrough. 

The gateways are associated with local networks 22 at 

which individual telephonic stations 24 are positioned. The 

gateways to which the local networks are connected form 

the access mechanism through which the telephonic stations 

are connected to the packet data network and through which 

all calls originated at, or to be terminated at, the telephonic 

stations of a particular local network are routed. If the local 

network associated with the access gateway is operable 

pursuant to a protocol that differs with the protocol pursuant 

to which the packet data network is operable, the access 

gateway performs translation operations to facilitate com 

munications between telephonic stations of the local net 

work and other telephonic stations. The local network may, 

for instance, form a legacy network that utilizes SS7 sig naling. A gateway associated with Such a local network 

operates, amongst other things, to convert the legacy SS7 

signaling into a format appropriate for communication 

through the packet-based, packet data network. Encapsula 

tion protocols, for instance, are utilized by the gateway to 

encapsulate SS7 messages to permit their communication 

through the packet data network. 

The communication system 10 here further includes a 

public safety answering point (PSAP) 28 that is coupled to 

the packet data network by way of a trunking gateway 

(TGW) 32. The public safety answering point is generally 

representative of any public-service location. Here, more 

particularly, the public safety answering point is represen 

tative of an emergency dispatch center, such as a dispatch 

center associated with an emergency dialing code that call 

ing parties enter to request emergency assistance. In the 

United States, the calling code formed of the digits 9-1-1 is 

the calling code associated with an emergency dispatch 

center of which the access point 28 is representative. When 

a call is made to the access point 28, appropriate responses 

to a request contained in the call is provided. 

The communication system also includes a SoftSwitch 34. 

also coupled to the packet data network. The softswitch, 

during normal operation of the communication system, provides call control functionality throughout the entire 

communication system. In a next-generation, telephonic 

communication system in which the packet data network 

forms an all-IP network, the softswitch is operable to com 

municate utilizing SIP (session initiation protocol) or 

another appropriate protocol. As, during normal operation of 

the communication system, the SoftSwitch controls the call 

handling operations of all calls within the network, commu 

nication systems typically include redundant SoftSwitch 

devices. In the event that a problem develops with one of the 

softswitches, at least one other redundant softswitch 

becomes operable to continue call handling operations. 

However, corresponding redundancy of the communica 

tion links 18 is not necessarily provided. If a failure, i.e., 

absence of call control, occurs in a communication link 18, 

the access gateway, and, in turn, the local network associated 

therewith is unable to communicate pursuant to normal 

operation of the communication system. The failure might 

occur at any location between the access gateway and the 

SoftSwitch. And, because call handling operations are pro 

vided by the softswitch 34, telephonic communication is 

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unable to be effectuated within the local network. That is to 

say, a call to be originated and terminated within a local 

network cannot be completed due to the inability of the 

softswitch to provide call handling functions due to the 

failure of the communication link. And, because of the 

remote positioning of the public safety answering point, a 

call placed thereto by a telephonic station positioned in the 

local network cannot be completed due to the failure of the 

communication link. 

Apparatus 38 of an embodiment of the present invention 

provides local call handling functionality in the event of 

failure of a communication link. The call handling function 

ality is provided locally and does not rely upon operation of 

the softswitch. Thereby, call control is effectuated at a local 

network, selectably to permit completion of local calls and 

also to route a call placed to the public service access point 

28 to a designated local-network station. By routing the call 

to the access point 28 a designated local-network Station, a 

calling party is able to alert personnel positioned at the 

local-network station of an emergency request. In the exem 

plary implementation, rudimentary call handling function 

ality is provided upon the occurrence of the communication 

link failure. For instance, Supplementary services are dis 

abled, or otherwise not provided. Only a subset of call 

handling functionality is provided, sometimes in manners 

different than in normal system operation. 

The apparatus 38 here also includes a detector embodied 

at the access gateway with which the apparatus 38 is 

associated. The detector operates to detect the occurrence of 

a communication failure, here indicated by the marking 44. 

beyond the access gateway. Upon occurrence of the failure 

of the communication link, the call control functionality provided by the softswitch is no longer available. 

Upon detection of the communication link failure, the 

detector generates an indication, here represented on the line 

46, that is provided to an emergency call router 48. In one 

implementation, the emergency call router is also embodied 

at the access gateway with which the apparatus 38 is 

associated. In another implementation, the emergency call 

router forms a stand-alone unit that is releasably engageable with the gateway. The emergency call router 48 is operable 

to provide selected, rudimentary local call control function 

ality to the access gateway and the local network associated 

with the gateway. By providing the local call handling 

functionality to the local network, calls placed between 

telephonic stations of the local network are at least select 

ably completable. Selection of which calls are completed as 

well as routing of certain priority calls to designated, local 

network telephonic stations is dependent, e.g., upon the 

call-type of the call being placed. Higher-priority calls are 

permitted to be completed prior to lower-priority calls. 

Call-types include, for instance, local calls, long distance 

calls, e.g., local toll calls, intra-state calls, inter-state calls, 

international calls, toll-free calls, operator calls, collect calls, 

and emergency calls. Upon failure of the communication 

link, many of Such calls are no longer able to be completed. 

The emergency call router is coupled to the gateway also 

to receive indications, here represented by indicia generated 

on the line 52, to receive indications of calls originated by 

telephonic stations in the local network associated with the 

access gateway 16. The emergency call router includes a 

priority detector 56 that prioritizes call requests to selectably permit completion of the calls originated by originating 

stations in the local network. If the originating, telephonic 

station requests a call with another local-network, telephonic station, depending upon the priority level of the call deter 

mined by the priority determiner 56, the call is permitted to 

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be completed. Prioritization, in the exemplary implementa 

tion, is dependent upon priority listings contained in one or 

more priority lists 58 of the emergency call router. Here, 

N-priority lists are maintained, 58-1 through 58-N. The 

contents of one or more of the lists are accessed by the 

priority detector, and the priority level associated with a call, 

indicated by the indicia provided to the call router on the line 

52 is compared by a comparator 62 of the priority detector 

against the priority contained in the accessed list. Respon sive to the comparison, the call is either permitted to be 

completed, routed to a designated local-network station, or 

prevented from being completed. 

In the exemplary implementation, a voice path 63 also 

extends from the access gateway to the emergency call 

router. And, the call router further comprises a radio tele 

phonic station, here a cellular mobile station 64. Personnel 

operating the emergency call router are able to utilize the 

mobile station to establish a voice call, here by way of a 

cellular access network 65 with another location. Alter 

nately, radio Switching functionality can be provided to the 

mobile station to direct voice signals generated on the voice 

line 63 to the access network 65. 

The priority in the list 58-1 is a calling party, priority 

listing in which priority levels are associated with the 

originating, telephonic stations from which calls are placed. 

And, the priority contained in the list 58-N is dependent 

upon the priority level associated with the called party. Such 

priority levels can also be maintained in a single listing. Prioritization, in one exemplary implementation, provides 

emergency calls placed to the public safety answering point 

28 as the highest-priority calls. When a call is placed to the 

public safety answering point, the failure of the communi 

cation link prevents routing of the call thereto. The emer 

gency call router, upon detection of the call, routes the call, 

instead, to a designated, local-network Station thereby to 

complete the priority call thereto. Appropriate response to 

the call can thereafter be made. In an exemplary priority listing, a next-highest priority level is associated with calls 

originated at a telephonic station to be placed to a published, 

three-digit service center. And, next in line, are calls placed 

to, or from, priority callers, i.e., a selected list of calling stations, such as police, hospitals, and fire stations. And, 

finally, as a lowest-priority, calls placed within the local 

network between non-priority calling stations are provided. 

The priority detector selectably routes the call or prevents routing of the call, depending upon the calling capacity 

within the local network and the priority level of the call. If 

a high-priority call is placed and capacity is not otherwise 

available, a lower-priority call is terminated by the emer 

gency call router to permit the higher-priority call to be 

completed. 

When an emergency call is placed, for instance, the access 

gateway is programmed to provide dialtone to the calling 

station and to accept call origination requests permitted for 

emergency situations. The emergency call router, in one 

implementation, processes only calls to emergency centers 

and calls within the local community encompassed by the 

local network. Priority is given to emergency calls, i.e., local 

calls within the local network are denied if the percentage of 

emergency calls rise above a defined limit. All other calls, 

Such as long distance, 800 calls, etc., are denied. The access 

gateways are programmed to play an announcement or tone 

to indicate that only emergency and local calls are being accepted at a particular time. All requests for Supplementary 

services, normally otherwise provided by the softswitch, are 

also denied. And, in one implementation, the emergency call 

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US 7,388,868 B2 

router forms a simplex configuration analogous to the redun 

dancy created in the SoftSwitch, redundant emergency call 

rOuterS. 

During operation of one implementation, the access gate 

way registers with the associated emergency call router in 

the same manner as a failure-over to a backup SoftSwitch 

subsequent to failure of a primary softswitch. Non-emer 

gency calls can be denied by the access gateway automati 

cally by activating call gapping upon a SoftSwitch link 

failure or by the emergency call router when an access 

gateway registers with it for emergency service. 

FIG. 2 illustrates a message sequence diagram, shown 

generally at 72, representative of operation of signaling 

during operation of the communication system 10. 

When a communication link extending beyond the access 

gateway fails, detection is made of the failure by the detector 

42 of the access gateway and an indication is provided, indicated by the segment 74, to the emergency call router. 

The emergency call router becomes operable responsive 

thereto. 

Subsequently, when an originating calling station 24 

originates a call, a call request associated therewith is 

routed, indicated by the segment 76, to the access gateway. 

The access gateway, in turn, generates an indication of the 

call, indicated by the segment 78, to the emergency call 

router. When the emergency call router receives the indica 

tions of the call origination, determinations are made by the 

priority determiner 56 as to whether the call shall be 

permitted to be completed, in manners analogous to those 

described above. The results of the determinations, here 

permission to route the call to a designated, local-network 

station, is provided, indicated by the segment 82, to the 

access gateway. The access gateway, in turn, performs 

appropriate call setup procedures so that the call is com 

pleted between the originating calling station and a termi 

nating calling station 24. The communication session, indi 

cated by the block 84, is thereby provided. 

FIG. 3 illustrates the access gateway 16-4, 16-5, and 16-6, 

shown to form a portion of the communication system 10 in 

FIG. 1 connected to the network 14 by way of the aggre gation point 20. Here, the emergency call router 48 forms a 

portable, stand-alone unit, connectable to any of the access 

gateways. When connected to the access gateway 16-4, the 

emergency call router operates to provide local call handling functionality to all gateways Subtending therefrom. That is 

to say, when the emergency call router is positioned at the 

gateway 16-4, the emergency call router provides call han 

dling functionality to, in addition to the gateway 16-4, the 

gateways 16-5 and 16-6. When the emergency call router is 

implemented as a portable, stand-alone unit, the router is 

positionable at any location within the communication sys 

tem made necessary due to the occurrence of a failure of a 

communication link. 

FIG. 4 illustrates a method flow diagram, shown generally 

at 92, that lists the method steps of an embodiment of the 

present invention. The method facilitates call completion of 

a call when the call is of at least a first selected call-type, Subsequent to failure of a normal-operation communication 

link. 

First, and as indicated by the block 94, failure of the 

normal-operation communication link is detected. Then, and 

as indicated by the block 96, a call request of the selected 

call-type is selectably routed by way of an emergency call 

router that is at least coupled to the access gateway. Thereby, 

call completion of the selected call of the call-type is 

facilitated between an origination station and a terminating 

station. 

10 

15 

25 

30 

35 

40 

45 

50 

55 

60 

65 

10 

The previous descriptions are of preferred examples for 

implementing the invention, and the Scope of the invention 

should not necessarily be limited by this description. The 

scope of the present invention is defined by the following 

claims: 

What is claimed is: 

1. In a communication system having a communication 

network, the communication system controlled by a com 

munication system controller also connected to the commu 

nication network, and to an originating station operable to 

originate a call of at least a first selected call-type therefrom, 

the call routable by way of a normal-operation communi 

cation link, an improvement of apparatus for facilitating call 

completion of the call when the call is of the at least the first 

selected call-type and Subsequent to failure of the normal 

operation communication link, said apparatus comprising: 

an emergency call router at least coupled to the access 

gateway, said emergency call router selectably operable 

responsive to failure of the normal-operation commu 

nication link for routing the call of the first selected 

call-type, thereby to facilitate call completion of the 

first selected call-type originated by the origination 

station; and 

a target gateway coupled to the emergency call router; 

said emergency call router determines whether the call 

request is for a call of the first selected call-type prior 

to said operation of routing the call of the first selected 

call-type. 

2. The apparatus of claim 1 wherein the communication 

network further is coupled to at least a first access gateway 

and wherein said emergency call router is embodied at the 

first access gateway. 

3. The apparatus of claim 1 wherein the communication 

network is further coupled to at least a first access gateway 

and wherein said emergency call router forms a standalone 

entity, connectable to the access gateway. 

4. The apparatus of claim 1 wherein the communication 

network is further coupled to at least a first access gateway 

and wherein the access gateway comprises a functional 

aggregation point at which a first gateway device and at least 

a second gateway device are connected and wherein said 

emergency call router is coupled to the functional aggrega tion point. 

5. The apparatus of claim 1 further comprising a detector 

coupled to receive indications of communication integrity 

on the normal-operation communication link, said detector 

for detecting failure of the normal-operation communication 

link. 

6. The apparatus of claim 5 wherein the communication 

network is further coupled to at least a first access gateway 

and wherein said detector is embodied at the access gateway, said detector further for notifying said emergency call router 

of detection thereat of the failure of the normal-operation 

communication link. 

7. The apparatus of claim 1 wherein the communication 

network is further coupled to at least a first access gateway 

and wherein said emergency call router further comprises a 

call priority determiner operable at least responsive to 

failure of the normal-operation communication link, said 

priority determiner for determining a priority level associ 

ated with the call of the at least the first selected call-type pursuant to a priority hierarchy. 

8. The apparatus of claim 7 wherein the call comprises a 

call priority indicia and wherein said call priority determiner 

determines the priority level associated with the call respon 

sive to the call priority indicia. 

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US 7,388,868 B2 

11 

9. The apparatus of claim 8 wherein said emergency call 

router further comprises a priority sequence list containing 

a listing of at least relative call-priority types and wherein 

said emergency call router further comprises a priority-level 

comparator coupled to receive indications of the priority 

level associated with a call request and indications of the 

priority sequence list, said priority-level comparator for 

comparing the priority level associated with the call of the 

at least the first selected call-type with the call-priority types 

contained in the listing. 

10. The apparatus of claim 9 wherein the communication 

system further comprises a public safety answering point 

coupled to the communication network, wherein the call of 

the first call-type comprises public-safety-answering-point 

directed call, and wherein said emergency call router oper 

ates to route the public-safety-answering-point directed call. 

11. The apparatus of claim 10 wherein the communication 

system further comprises a local-network alternate station 

coupled to an access gateway and wherein said emergency 

call router operates to route the public-service-access-point 

directed call to the local-network alternate station. 

12. The apparatus of claim 1 wherein the communication 

system further comprises a local-network alternate station, 

wherein said emergency call muter is further for determining 

whether the call of the selected call-type shall be comple table by way of the normal-operation communication link 

and for rerouting a call request to the local-network alternate 

station upon determination that the call completion by way 

of the normal-operation communication link. 

13. The apparatus of claim 1 wherein the communication 

system further comprises a local network having at least a 

first local-network station, the local network associated with 

an access gateway, and wherein said emergency call router 

is further selectably operable responsive to failure of the 

normal-operation communication link for routing a call 

request to the local-network station. 

14. The apparatus of claim 13 wherein the call request comprises a request for call termination at a selected one of 

the at least the first local-network station. 

10 

15 

25 

30 

35 

12 

15. The apparatus of claim 14 wherein said emergency 

call router selects to route the call request to the local 

network station responsive to detection of the call and 

responsive to levels of call routing of the selected call-type. 

16. The apparatus of claim 1 wherein said emergency call 

router comprises a portable standalone entity, deployable on an as-needed basis. 

17. The apparatus of claim 16 wherein said emergency 

call router comprises a selectable database. 

18. In a method of communicating in a communication 

system having a communication network, the communica 

tion system controlled by a communication system control 

ler also connected to the communication network, and to an 

originating station operable to originate a call of at least a 

first selected call-type therefrom, the call routable by way of 

a normal-operation communication link, an improvement of 

a method for facilitating call completion of the call when the 

call is of the at least the first selected call-type and subse 

quent to failure of the normal-operation communication 

link, said method comprising: 

detecting failure of the normal-operation communication 

link; 

selectably routing a call request of the selected call-type 

by way of an emergency call router, thereby to facilitate 

call-completion of the selected call-type between the 

origination station and the terminating station; 

connecting the emergency call router, as a preliminary 

operation, between at least a first access gateway and a 

target gateway of the communication system; and 

determining whether the call request is for a call of the 

selected call-type prior to said operation of selectably 

routing. 

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