# Patent

## Title
Using DRCLocks for conducting call admission control

## Abstract

Methods and systems are provided for using DRCLocks for conducting call admission control. In an embodiment, an access node provides service to a plurality of access terminals on a carrier in a coverage area, where the plurality of access terminals does not include a first access terminal. The access node receives a request for new service on the carrier in the coverage area from the first access terminal over an air interface, and responsively determines whether an aggregate-DRCLock condition is met. If the aggregate-DRCLock condition is met, the access node denies the request for new service.

## Background
BACKGROUND
Many people use mobile stations, such as cell phones and personal digital assistants, to communicate with cellular wireless networks, which typically provide communication services such as voice, text messaging, and packet-data communication to these mobile stations. The mobile stations and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless protocol such as 1×RTT CDMA, EV-DO, WiMax, etc.
Mobile stations typically conduct these wireless communications with one or more base transceiver stations (BTSs), each of which send communications to and receive communications from mobile stations over the air interface. Each BTS is in turn communicatively connected with an entity known as a base station controller (BSC), which (a) controls one or more BTSs and (b) acts as a conduit between the BTS(s) and one or more switches or gateways, such as a mobile switching center (MSC) and/or packet data serving node (PDSN), which may in turn interface with one or more signaling and/or transport networks.
As such, mobile stations can typically communicate with one or more endpoints over the one or more signaling and/or transport networks from inside one or more coverage areas (such as cells and/or sectors) of one or more BTSs, via the BTS(s), a BSC, and an MSC and/or PDSN. In typical arrangements, MSCs interface with the public switched telephone network (PSTN), while PDSNs interface with one or more core packet-data networks and/or the Internet.
OVERVIEW
A mobile station may engage in packet-data communication over one or more packet-data networks with one or more different types of endpoints, some examples of which include other mobile stations, landline phones, conference servers, gateways, etc. In the case of landline phones, a media gateway may reside between a packet-data network and a circuit-switched network such as the PSTN. For simplicity of explanation, examples involving mobile stations communicating with one respective endpoint over a packet-data network via one BTS, one BSC, and one PDSN may be described herein; however, the present disclosure could just as well be applied to more complex examples, perhaps involving communication sessions between mobile stations and multiple endpoints, such as may be the case in a conference call.
Furthermore, a given instance of packet-data communication engaged in by a mobile station may be of any type. One popular type is Voice over IP (VoIP), which may have a user experience that is similar to voice calls conducted over the PSTN via a BTS, a BSC, and an MSC. VoIP calls (i.e. sessions) may also or instead take the form of push-to-talk (PTT) sessions, known to those in the art. In general, as used herein, “VoIP” encompasses any type of voice-over-packet communication that may be engaged in by mobile stations. More generally, the methods and systems described herein may be applied to any type of data communication, though doing so with respect to latency-sensitive types such as VoIP, videoconferencing, streaming media, etc. may yield the greatest dividends with respect to user satisfaction.
When a base station—and a wireless network in general—provides packet-data service (e.g. VoIP service) to a given mobile station, the base station is providing at least two services to that mobile station. The first is wireless service over the air interface, and the other is transport service (i.e. connectivity) over one or more packet-data networks, such as direct transport service over the service provider's privately-operated core packet-data network, as well as indirect transport service over a public packet-data network such as or including the Internet.
Note that, in contexts where wireless service is provided according to a protocol known as EV-DO (perhaps according to IS-856, Revision 0 and/or IS-856, Revision A, both of which are hereby incorporated herein by reference in their entirety), mobile stations are often referred to as access terminals, and BSCs are often referred to as RNCs (radio network controllers). Furthermore, a combination of an RNC and one or more BTSs is often referred to as an access node. This terminology will be adopted for the balance of this written description, though again for illustration and not to limit the described embodiments to any particular protocol.
As known to those of skill in the art, in EV-DO networks, access terminals use a reverse-link channel known as the DRC channel to request forward-link service from a particular network sector. Typically, an access terminal will specify the sector (or coverage area, more generally) from which the access terminal is requesting forward-link service by transmitting a particular value known as a DRC cover in the reverse-link DRC channel, where the DRC cover sent by the access terminal indicates a particular sector. Incidentally, the access terminal also includes data in the reverse-link DRC channel that indicates a particular data rate or particular packet-transmission format, depending on the implemented release or revision of IS-856.
In any event, upon receiving a request for forward-link service (i.e. a DRC request) from an access terminal via the reverse-link DRC channel, a given EV-DO network sector may grant the request and provide forward-link service, in which case the access terminal receives forward-link service from that sector until the access terminal selects another sector, powers down, ceases communication, and/or some other event occurs. If, however, the sector (or more generally perhaps, the access node) determines that the requested sector is not able or willing to provide forward-link service to the access terminal, the sector typically transmits a value to the access terminal known as a DRCLock. In current implementations, the DRCLock is sent when a potential serving sector determines that it is not properly receiving (e.g. cannot properly decode) the reverse-link DRC channel from the access terminal, and thus concludes that it is not a good candidate to provide forward-link service to the access terminal.
Essentially, then, the DRCLock is a message from a sector to an access terminal, informing the access terminal that, at least for the time being, the sector is not an option for providing forward-link service to the access terminal. The DRCLock typically takes the form of a bit, where one of the two possible values (referred to herein as the DRCLock being “set”) indicates that the sector is not an option for providing forward-link service to the access terminal, and where the other of the two possible values (referred to herein as the DRCLock being “clear” or “cleared”) indicates that the sector is an option for the access terminal. In response to detecting that a sector has set the DRCLock for an access terminal, the access terminal typically points its DRC channel at another sector (i.e. transmits a DRC cover corresponding to another sector). The access terminal may then periodically check whether the first sector has cleared its DRCLock for that access terminal and, if so, point its DRC cover back at that first sector.
Note that the serving network maintains what is known as an “active set” of sectors for each access terminal; and it is the sectors in a given access terminal's active set that will evaluate whether they are able to properly receive DRC transmissions from that access terminal: if a given sector is not, that sector will set a DRCLock for that access terminal and later reevaluate. Note as well that sectors can provide service on multiple carrier frequencies (carriers), and that a given instance of a carrier in a given sector may be referred to herein as a sector/carrier.
Furthermore, some possible causes of a DRCLock needing to be set are high reverse noise on a sector/carrier, weak reverse-link transmissions from an access terminal, fading conditions, improper link imbalance, etc. If a high number of access terminals on a sector/carrier are receiving DRCLocks from an access node, this is likely an indication of poor RF conditions on the sector/carrier. And poor RF conditions are even more strongly indicated if the aggregate number of DRCLocks on a sector/carrier stays high for a sustained period of time.
Furthermore, call-admission control refers to admitting or denying new users (i.e. access terminals) service in a given wireless coverage area, such as a cell or sector. In particular, call-admission control involves making decisions to grant or deny service to access terminals upon receiving requests for new service (e.g. call-origination messages, handoff requests, etc.) from access terminals not currently being served by an access node. Note that these decisions may be described as being made by the access node, which includes the possibilities of the decisions being made by a BTS, an RNC, some other entity, or perhaps by a combination thereof.
Note that, in current implementations, call-admission-control decisions are made based on air-interface conditions on a sector/carrier, but they are not made in such a manner that takes into account an aggregate number of DRCLocks (i.e. DRCLocks that are currently set) on a sector/carrier. Nor are they made in such a manner that takes into account the aggregate number of DRCLocks remaining high for a timeout period.
In accordance with the present methods and systems, however, an EV-DO access node may receive a request for service on a sector/carrier from an access terminal that is not currently receiving service on that sector/carrier (i.e. a request for new service). In response to receiving that request, the access node may identify how many (or perhaps what ratio of, percentage of, etc.) access nodes having that sector/carrier in their active set are currently being sent DRCLocks by the access node (i.e. the aggregate DRCLock). If the aggregate DRCLock exceeds a given threshold, the access node may deny the request for new service.
In some embodiments, the access node may include a time element in making the above-described determination. That is, the access node may, in response to determining that the aggregate DRCLock exceeds the threshold, start a timer: if, until expiration of the timer, the aggregate DRCLock remains above the threshold, the access node may deny the request for new service. In other embodiments, checking whether the aggregate DRCLock exceeds the threshold may involve checking whether the aggregate DRCLock has been above the threshold for at least a certain amount of time. And other examples are clearly possible as well.
Note that, in some embodiments, a dual-mode (e.g. EV-DO and 1×RTT CDMA (“1×”)) access terminal that is denied service from a first network (e.g. an EV-DO network) may attempt to acquire resources from a second network (e.g. a 1× network).
And it should be noted that the above overview is intended to be illustrative and not limiting. Additional and/or different features may be present in some embodiments. And any description of a mobile station, access terminal, or other network element operating according to any particular protocol is by way of example and not limitation; any suitable wireless protocol(s) may be used, such as but not limited to 1×RTT CDMA, EV-DO, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, WiMax (e.g. IEEE 802.16), LTE, microwave, satellite, MMDS, Wi-Fi (e.g. IEEE 802.11), Bluetooth, infrared, and/or any other now known or later developed.



BRIEF DESCRIPTION OF THE DRAWINGS
Various exemplary embodiments are described herein with reference to the following drawings, wherein like numerals denote like entities.
FIG. 1 is a simplified block diagram of a communication system, in accordance with exemplary embodiments;
FIG. 2 is a flowchart of a method, in accordance with exemplary embodiments.



DETAILED DESCRIPTION OF THE DRAWINGS
1. Exemplary Architecture
FIG. 1 is a simplified block diagram of a communication system, in accordance with exemplary embodiments. It should be understood that this and other arrangements described herein are set forth only as examples. Those skilled in the art will appreciate that other arrangements and elements (e.g., machines, interfaces, functions, orders, and groupings of functions, etc.) can be used instead, and that some elements may be omitted altogether. Further, many of the elements described herein are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, and in any suitable combination and location. Various functions described herein as being performed by one or more entities may be carried out by hardware, firmware, and/or software. Various functions may be carried out by a processor executing instructions stored in memory.
As shown in FIG. 1, a communication system 100 includes an access terminal (AT) 102, an access node 105 (shown as comprising a BTS 103 and an RNC 104), a PDSN 106, a packet-data network (PDN) 108, a gateway 110, a PDN 112, and an endpoint 114. Note that additional entities not depicted in FIG. 1 could be present as well. As an example, there could be more than one access terminal in communication with access node 105; also, there could be additional entities in communication with PDN 108 and/or PDN 112. Also, there could be one or more routers, switches, other devices and/or networks making up at least part of one or more of the communication links.
Access terminal 102 may be any device arranged to carry out the access-terminal functions described herein, and may include a user interface, a wireless-communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those access-terminal functions. The user interface may include buttons, a touchscreen, a microphone, and/or any other elements for receiving inputs from users, as well as a speaker, one or more displays, and/or any other elements for communicating outputs to users.
The wireless-communication interface may comprise an antenna and a chipset for communicating with one or more base stations over an air interface. As an example, the chipset could be one suitable for engaging in EV-DO communications, including IS-856, Rel. 0 and/or IS-856, Rev. A communications. The chipset or wireless-communication interface in general may also be able to communicate with a 1×RTT CDMA network, a Wi-Fi (IEEE 802.11) network, and/or one or more additional types of wireless networks. The processor and data storage may be any suitable components known to those of skill in the art. As examples, access terminal 102 could be or include a cell phone, a PDA, a computer, a laptop computer, a hybrid IS-2000/IS-856 device, and/or a multi-mode Wi-Fi/cellular device.
BTS 103 may be any one or any combination of network elements arranged to carry out the BTS functions described herein, and may include a communication interface, a processor, and data storage comprising instructions executable by the processor to carry out those BTS functions. The communication interface may include one or more antennas and chipsets or other components for providing one or more coverage areas such as cells or sectors according to a protocol such as CDMA, EV-DO, WiMax, or any other suitable protocol. The communication interface may also include a wired or wireless packet-data interface (which may be characterized as a backhaul connection), such as an Ethernet interface, for communicating with RNC 104.
RNC 104 may be any one or any combination of network elements arranged to carry out the RNC functions described herein. As such, RNC 104 may include a communication interface, a processor, and data storage comprising instructions executable by the processor to carry out those RNC functions. The communication interface may include a wired or wireless packet-data interface (which may be characterized as a backhaul connection), such as an Ethernet interface, for communicating directly or over one or more networks with PDSN 106. In general, RNC 104 functions to control one or more BTSs, and to serve as a conduit between the one or more BTSs and PDSN 106, enabling access terminals to communicate over PDN 108 and perhaps beyond.
Note that access node 105 may comprise BTS 103 and RNC 104, and may comprise one or more additional BTSs as well. In general, access node 105 provides wireless service to access terminals over an air interface, and uses a backhaul connection to provide transport service over PDN 108 (or perhaps PDN 108 and PDN 112) to those access terminals.
PDSN 106 may be any networking server or other device arranged to carry out the PDSN functions described herein. PDSN 106 may include a communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those PDSN functions. The communication interface may include a wired packet-data interface such as an Ethernet interface for communicating with access node 105 and/or over PDN 108. Note that PDSN 106 may, instead or in addition, comprise a wireless-communication interface for communicating with access node 105 and/or over PDN 108. Note also that PDSN 106 may use the same interface or separate interfaces for communicating with access node 105 and for communicating over PDN 108. PDSN 106 may generally function to provide access node 105 with access to PDN 108, and vice versa.
Each of PDN 108 and PDN 112 may include one or more wide area networks, one or more local area networks, one or more public networks such as the Internet, one or more private networks, one or more wired networks, one or more wireless networks, and/or one or more networks of any other type. Devices in communication with PDN 108 and/or PDN 112 may exchange data using a packet-switched protocol such as IP, and may be identified by an address such as an IP address. In this example, PDN 108 is the service provider's privately-operated IP network (where the service provider may operate at least access node 105 and PDSN 106), while PDN 112 is the Internet. However, this is for illustration and not by way of limitation. In some embodiments, PDSN 106 may connect directly to the Internet, in which case PDN 108 and gateway 110 may not be necessary. And other configurations are certainly possible as well.
Gateway 110 may be any networking server or other device arranged to carry out the gateway functions described herein. Thus, gateway 110 may include a communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those gateway functions. The communication interface may include a wired packet-data interface, such as an Ethernet interface, for communicating over PDN 108 and/or PDN 112. Note that gateway 110 may, instead or in addition, comprise a wireless-communication interface for communicating over PDN 108 and/or PDN 112. Gateway 110 may use the same interface or separate interfaces for communicating over PDN 108 and/or PDN 112. Gateway 110 may generally function to provide PDN 108 and PDN 112 with connectivity to each other.
Endpoint 114 may be any device arranged to carry out the endpoint functions described herein. As such, endpoint 114 may include a (wired and/or wireless) communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those endpoint functions. Endpoint 114 may be or include a media gateway (perhaps connected to the PSTN), a packet-based telephone, a personal computer, a PDA, a mobile station, an access terminal, a PTT server, a call server, and/or any other type of device capable of functioning as an endpoint of a VoIP—or other type of packet-data-communication—session in accordance with various embodiments.
2. Exemplary Operation
FIG. 2 depicts a flowchart of an exemplary method, in accordance with an exemplary embodiment. In some embodiments, as described below in connection with FIG. 2, method 200 may be carried out by an access node, such as access node 105. In other embodiments, the method may be carried out by another network entity mentioned herein, such as BTS 103, RNC 104, PDSN 106, some other network entity, or some combination thereof. In general, method 200 may be carried out by a base station, an access node, a BTS, a BSC, an RNC, an MSC, a PDSN, some other network entity, or perhaps some combination thereof.
As shown in FIG. 2, method 200 begins at step 202, where access node 105 provides service to a plurality of access terminals (not depicted) on a carrier in a coverage area (which may be a cell or a sector), wherein the plurality of access terminals does not include a first access terminal (here, access terminal 102). As noted above, access node 105 may be or include an EV-DO access node, the access terminals may be or include EV-DO access terminals, and the service may be or include EV-DO service (in compliance with at least one of IS-856, Release 0 and IS-856, Revision A). And access node 105 may include an RNC and at least one BTS.
At step 204, access node 105 receives a request for new service on the carrier in the coverage area from access terminal 102 over an air interface. The request for new service may be or include at least one of a call-origination message and a handoff request. In an embodiment, method 200 may only be carried out when the request for new service is associated with a certain type of packet-data communication (e.g. VoIP, PTT, teleconferencing, streaming media, etc.).
At step 206, in response to receiving the request for new service, access node 105 determines whether an aggregate-DRCLock condition is met. At step 208, if the aggregate-DRCLock condition is met, access node 105 denies the request for new service. In an embodiment, if the aggregate-DRCLock condition is not met, access node 105 grants the request for new service. In another embodiment, if (a) the aggregate-DRCLock condition is not met and (b) at least one additional condition (perhaps related to one or more factors such as air-interface conditions, capacity, etc.) is met, access node 105 grants the request for new service. And certainly variations on this are possible as well.
With respect to the aggregate-DRCLock condition that is evaluated in step 206, a number of possibilities exist. In one embodiment, the condition is whether access node 105 currently has a DRCLock set for at least a threshold number of access terminals in the plurality of access terminals. In another embodiment, the condition is whether access node 105 currently has a DRCLock set for at least a threshold percentage of access terminals in the plurality of access terminals. And certainly other possibilities exist as well.
In one embodiment, the condition is whether an aggregate-DRCLock sub-condition is met for a threshold period of time. Note that this sub-condition could be either of the options mentioned in the preceding paragraph, or another option. Furthermore, in an embodiment, the threshold period of time ends approximately when access node 105 receives the request for new service; that is, access node 105 may evaluate whether the sub-condition had prevailed for the previous second, 10 seconds, 30 seconds, or some other option. In another embodiment, the threshold period of time starts approximately when access node 105 receives the request for new service; that is, access node 105 may evaluate whether the sub-condition then prevails for the ensuing second, 10 seconds, 30 seconds, or some other option. And other possibilities exist.
3. Conclusion
Various exemplary embodiments have been described above. Those skilled in the art will understand, however, that changes and modifications may be made to those examples without departing from the scope of the claims.

## Claims

1. A method comprising:
an access node providing service to a plurality of access terminals on a carrier in a coverage area, wherein the plurality of access terminals does not include a first access terminal;
the access node receiving a request for new service on the carrier in the coverage area from the first access terminal over an air interface;
in response to receiving the request for new service, the access node determining whether an aggregate-DRCLock condition is met; and
if the aggregate-DRCLock condition is met, the access node denying the request for new service.

2. The method of claim 1, wherein the access node comprises an EV-DO access node, wherein the access terminals comprise EV-DO access terminals, and wherein the service comprises EV-DO service.

3. The method of claim 1, wherein the access node comprises a radio network controller (RNC) and at least one base transceiver station (BTS).

4. The method of claim 1, wherein the service complies with at least one of IS-856, Release 0 and IS-856, Revision A.

5. The method of claim 1, wherein the coverage area is a cell or a sector.

6. The method of claim 1, wherein the request for new service is a call-origination message or a handoff request.

7. The method of claim 1, wherein the aggregate-DRCLock condition is whether the access node currently has a DRCLock set for at least a threshold number of access terminals in the plurality of access terminals.

8. The method of claim 1, wherein the aggregate-DRCLock condition is whether the access node currently has a DRCLock set for at least a threshold percentage of access terminals in the plurality of access terminals.

9. The method of claim 1, wherein the aggregate-DRCLock condition is whether an aggregate-DRCLock sub-condition is met for a threshold period of time.

10. The method of claim 9, wherein the aggregate-DRCLock sub-condition is whether the access node currently has a DRCLock set for at least a threshold number of access terminals in the plurality of access terminals.

11. The method of claim 9, wherein the aggregate-DRCLock sub-condition is whether the access node currently has a DRCLock set for at least a threshold percentage of access terminals in the plurality of access terminals.

12. The method of claim 9, wherein the threshold period of time ends approximately when the access node receives the request for new service.

13. The method of claim 9, wherein the threshold period of time starts approximately when the access node receives the request for new service.

14. The method of claim 1, further comprising:
if the aggregate-DRCLock condition is not met, granting the request for new service.

15. The method of claim 1, further comprising:
if (a) the aggregate-DRCLock condition is not met and (b) at least one additional condition is met, granting the request for new service.

16. The method of claim 1, carried out only if the request for new service is associated with a type of packet-data communication selected from a set of types of packet-data communication.

17. The method of claim 16, wherein the set of types of packet-data communication includes at least one of VoIP, PTT, teleconferencing, and streaming media.

18. An access node comprising:
a wireless-communication interface;
a backhaul connection;
a processor; and
data storage comprising instructions executable by the processor for carrying out functions including:
providing service to a plurality of access terminals on a carrier in a coverage area, wherein the plurality of access terminals does not include a first access terminal;
receiving a request for new service on the carrier in the coverage area from the first access terminal over an air interface;
in response to receiving the request for new service, determining whether an aggregate-DRCLock condition is met; and
if the aggregate-DRCLock condition is met, denying the request for new service.

19. The access node of claim 18, wherein the access node comprises an EV-DO access node, wherein the access terminals comprise EV-DO access terminals, wherein the service comprises EV-DO service, and wherein the service complies with at least one of IS-856, Release 0 and IS-856, Revision A.

20. The access node of claim 18, wherein the access node comprises a radio network controller (RNC) and at least one base transceiver station (BTS).

21. The access node of claim 18, wherein the request for new service is a call-origination message or a handoff request.

22. The access node of claim 18, wherein the aggregate-DRCLock condition is whether the access node currently has a DRCLock set for at least a threshold number of access terminals in the plurality of access terminals.

23. The access node of claim 18, wherein the aggregate-DRCLock condition is whether the access node currently has a DRCLock set for at least a threshold percentage of access terminals in the plurality of access terminals.

24. The access node of claim 18, wherein the aggregate-DRCLock condition is whether an aggregate-DRCLock sub-condition is met for a threshold period of time, and wherein the threshold period of time either starts or ends approximately when the access node receives the request for new service.

25. The access node of claim 18, further comprising:
if (a) the aggregate-DRCLock condition is not met and (b) zero or more additional conditions are met, granting the request for new service.