Explicit congestion notification based rate adaptation using binary marking in communication systems

A method, apparatus, and computer program product for responding to congestion levels in a communication system by rate adaptation. A congestion condition is indicated by marking data packets. In response to receiving an indication of congestion, a data rate is reduced. A rate reduction inhibit timer is started, and further rate reduction is initiated if congestion is indicated after the rate reduction inhibit timer has expired. A rate increase timer is used to initiate a rate increase if no indication of congestion is received during a rate increase time.

TECHNICAL FIELD

The present disclosure relates generally to a communication system and, in particular, to a method and apparatus for responding to congestion in a communication system.

BACKGROUND

A mobile or cellular telephone system is an example of a communication system that is capable of transmitting and receiving data between end user equipment or applications and network equipment. Transmitted and received data may be in the form of data packets. Transmitted data packets may be in a variety of formats and include a variety of different types of data, including voice data, binary data, video data, and the like.

In a communication system, such as a mobile or cellular telephone communication system, various methods are used to establish the rate of communication or bitrate at which data packets are transferred between a user's mobile device, such as a mobile telephone, and the rest of the system. For example, if Adaptive MultiRate (AMR) or Adaptive MultiRate-Wideband (AMR-WB) transmission is used, at call set-up a mode set is negotiated through the Session Description Protocol (SDP). The Session Description Protocol parameter “mode-set” takes a value that represents a subset of bitrates that can be used during a call. The value is selected from the set {0, . . . , 7} for Adaptive MultiRate transmissions and from the set {0, . . . , 8} for Adaptive MultiRate-Wideband transmissions. The value to be used may be selected, for example, based on detected signal strength between the mobile device and the rest of the network at the time of call set-up. When a sender encodes speech it must use one of the bitrates in the mode set. The mode used to encode is then indicated to the receiver in a Codec Mode Indication (CMI) field of the Real-time Transport Protocol payload.

For Long Term Evolution (LTE), the relevant specification in terms of codec rate adaptation is 3GPP TS 26.114, which specifies the Multimedia Telephony Services over IP Multimedia Subsystem (MTSI). Included in this specification are several means of adaptation. For example, bit rate, number of frames per packet, and amount of redundant frames per packet, may all be adapted according to requests from the receiver of the encoded media. These requests are generally included in the RTP Control Protocol Application Defined (RTCP APP) packets.

Problems arise in a communication system when demands on the network system to process data packets for transmission through the system in a timely manner exceed network capacity. In such situations the network is said to be experiencing congestion. A typical response to such congestion is for the network simply to drop packets received from, or to be transmitted to, a user application or equipment, and that cannot be processed by the network in a timely manner.

Explicit Congestion Notification (ECN) is a method for the network to indicate to user applications that the network is experiencing congestion. In response to receiving such a notification, a user application or equipment can reduce its sending rate, in order to avoid packets being dropped. For example, Explicit Congestion Notification may be implemented by marking two bits in the Internet Protocol (IP) header of a packet as ‘11’, indicating that congestion is being experienced by a network element processing the packet. Via a feedback mechanism, the sender of the packet is notified of the congestion, and can then reduce its sending rate.

Until recently, it has not been specified how to apply Explicit Congestion Notification to User Datagram Protocol (UDP) traffic. The User Datagram Protocol itself does not contain a feedback mechanism. However, most real-time applications, such as voice, video, real-time text, and the like, use Real-timeTransport Protocol (RTP) over User Datagram Protocol, which does have a feedback mechanism, namely RTP Control Protocol (RTCP). It has been proposed to use Explicit Congestion Notification with Real-time Transport Protocol. In this proposal, the receiver of Internet Protocol packets that are marked “Congestion Experienced” communicates this information to the sender through the RTP Control Protocol feedback packets. The sender can then reduce its bitrate in order to reduce congestion. For Adaptive MultiRate (AMR) or Adaptive MultiRate-Wideband (AMR-WB) transmissions, the sender can change its transmission mode to reduce congestion.

As an alternative, the receiver of packets marked “Congestion Experienced” may use the Codec Mode Request (CMR) field in the Real-time Transport Protocol payload to request that the sender reduce its bitrate. This has the advantage that additional RTP Control Protocol traffic is not created, when the network is already congested, in order to communicate which packets were marked “Congestion Experienced” to the sender. It has the disadvantage that it cannot be used to control bitrates when data packet flow is unidirectional. For codecs that do not have a Codec Mode Request field in the Real-time Transport Protocol payload, and for other media types, it is possible that a Temporary Maximum Media Stream Bit Rate Request (TMMBR) may be used to request the sender to reduce its bitrate.

It would be advantageous to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.

DETAILED DESCRIPTION

The different embodiments disclosed herein recognize and take into account a number of different considerations. For example, the disclosed embodiments recognize and take into account that current communication system specifications do not describe how a sender's bitrate is to be reduced when packets marked to indicate that congestion is being experienced are observed. Consider, for example, the scenario where an Adaptive MultiRate speech codec and the default Adaptive MultiRate mode set for a Multimedia Telephony Service for IP Multimedia Subsystem corresponding to bitrates of 12.2 kbps, 7.4 kbps, 5.9 kbps, and 4.75 kbps is used. If the sender is currently using the 12.2 kbps bitrate, and packets marked “Congestion Experienced” are observed, current specifications do not specify how the sender is to respond. In this case, response options include jumping immediately all the way down to 4.75 kbps or stepping down to the next lowest rate in the mode set and then stepping down again if packets marked “Congestion Experienced” continue to be observed. The disclosed embodiments recognize and take into account that current specifications do not specify how the bitrate should be adapted back up if congestion eases. Furthermore, the disclosed embodiments recognize and take into account that current specifications do not specify how user priority and emergency calls should be handled in the context of a system or method for adapting the bitrate in response to an explicit congestion notification.

The disclosed embodiments recognize and take into account that current solutions for Explicit Congestion Notification employ only an on/off or binary indication of congestion. Either data packets are marked to indicate that congestion is experienced or they are not. The disclosed embodiments recognize and take into account that a mechanism is needed for codec selection and adaptation in communication systems that employ binary “Congestion Experienced” marking for Explicit Congestion Notification.

The disclosed embodiments recognize and take into account that Internet Protocol traffic in a UTRAN or EUTRAN network can be very dynamic. Congestion detection and binary “Congestion Experienced” marking of data packets based on that detection can be very noisy and may be prone to oscillation. This may result in very unstable codec adaptation based network congestion control using Explicit Congestion Notification. Frequent and unnecessary adaptation could have a negative impact on perceived quality by a user.

The embodiments disclosed herein provide a system and method for rate adaptation in a communication system when a receiving terminal receives data packets with “Congestion Experienced” marked or unmarked. In accordance with disclosed embodiments, congestion is indicated as detected by the transmission of marked packets and congestion is indicated as cleared by the transmission of unmarked packets. Based upon the marked or unmarked packets detected, a receiver of the data packets determines a rate reduction or increase based on sequences provided by the network or configured on the receiver. If a rate adaptation is determined to be required, the receiver may send a codec rate change request with the determined rate to the sender.

Embodiments disclosed herein are particularly adapted to a mechanism for Explicit Congestion Notification based codec adaptation using binary “Congestion Experienced” marking in a UMTS Terrestrial Radio Access Network (UTRAN) or an Evolved UTRAN (E-UTRAN). For Long Term Evolution (LTE), the relevant specification in terms of codec rate adaptation is 3GPP TS 26.114, which specifies the Multimedia Telephony Services over IP Multimedia Subsystem (MTSI). Illustrative embodiments are applicable also to other communication systems and radio or fixed networks.

Turning first toFIG. 1, a wireless communication system is depicted in accordance with an illustrative embodiment. Wireless communication system100includes wireless network102. Wireless network102may comprise a single network or multiple networks forming a network of networks. Wireless network102provides for wireless communication by user equipment104,106, and108via wireless communication channels110,112, and114established between user equipment104,106, and108and wireless network102. As will be discussed in more detail below, examples of user equipment104,106, and108include mobile wireless communication devices including pagers, cellular phones, cellular smart-phones, wireless organizers, personal digital assistants, computers, laptops, handheld wireless communication devices, wirelessly enabled notebook computers and the like. Although only three user equipment104,106, and108are shown by example inFIG. 1, wireless network102may support use of much larger numbers of user equipment of various different types.

Wireless communication channels110,112, and114are established dynamically between user equipment104,106, and108and individual nodes116,118, and120of wireless network102. Channels110,112, and114may be established, for example, at the time that a call to or from one of user equipment104,106, and108is initiated. Certain characteristics of communication channels110,112, and114are established at call set-up. For example, such characteristics may include the codec that is to be employed by the communication channel110,112, or114during the call. For example, the codec to be used may be selected based on factors such as the signal strength or signal quality between user equipment104,106, and108and a corresponding one of nodes116,118, or120of network102at call set-up. Although only three nodes116,118, and120are shown by example inFIG. 1, wireless network102may include many more such nodes.

Network102operates to transfer data packets between user equipment104,106, and108using network nodes116,118, and120. Network102also may operate to transfer data packets between user equipment104,106, and108and other networks, such as conventional public switched telephone network (PSTN)122, or other public or private networks124, such as the Internet. This transfer of data packets to and from other networks122and124also uses network nodes116,118, and120. As data packet traffic through one or more of nodes116,118, and120increases, the capacity of network102to process and transfer packets in a timely manner to and from user equipment104,106, and108may be exceeded. In this case, network102, or one or more network nodes116,118, or120, is said to be congested. The embodiments disclosed herein provide an improved system and method for responding intelligently and more effectively when such network congestion occurs.

Referring now toFIG. 2, a block diagram of an implementation of wireless network102in which illustrative embodiments may be implemented is presented. Wireless network102may be, for example, a Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN). However, illustrative embodiments may be implemented in other similar or different communication networks, such as wireless networks using Long Term Evolution (LTE) technology. Illustrative embodiments also may be implemented in wireless networks configured in accordance with General Packet Radio Service (GPRS) and Global Systems for Mobile (GSM) technologies.

Wireless network102includes node202. In this example, node202is an example of one of nodes116,118, or120ofFIG. 1. As mentioned above, in practice, wireless network102comprises one or more of nodes202. For example, node202may be implemented as a Node B in a UMTS Terrestrial Radio Access Network or as the evolved Node B (eNodeB) in a Long Term Evolution network.

Node202may be referred to as a base transceiver station. Node202includes one or more radio frequency transmitters204and receivers206coupled to one or more antennas207. Transmitters204and receivers206are used by node202to communicate directly with mobile devices, such as user equipment104, via wireless communication channel110. Node202provides wireless network coverage for a particular coverage area, commonly referred to as a “cell”. Node202also includes one or more processing systems208, such as computer data processing systems, for implementing the functionality provided by node202.

Node202is coupled to, and controlled by, radio network controller210. Multiple nodes202may be coupled to radio network controller210in network102in accordance with an illustrative embodiment. Radio network controller210is responsible for controlling all nodes202that are connected to it. Radio network controller210carries out radio resource management, such as the management of radio channels and some mobility management functions. Radio network controller210may be the point where encryption is done before user data is sent to and from user equipment104.

Radio network controller210connects to core network212. Multiple radio network controllers210may be coupled to core network212. A main function of core network212is to provide for the routing of data packets between user equipment on network102and between user equipment on network102and users on other networks, such as public switched telephone network122and other public or private networks124, such as the Internet. Functions provided by core network212in a UMTS network may be implemented, for example, by a media gateway and a Serving General Packet Radio Service (GPRS) Support Node (SGSN). A media gateway is a translation device or service that converts digital media streams between disparate telecommunications networks. Media gateways enable multimedia communications across networks over multiple transport protocols, such as Asynchronous Transfer Mode (ATM) and Internet Protocol (IP). An SGSN is responsible for the delivery of data packets from and to mobile user equipment within its geographical service area. Its tasks may include packet routing and transfer, mobility management, logical link management, and authentication and charging functions. In a Long Term Evolution (LTE) network, similar functions may be provided in core network212by, for example, a mobility management entity (MME), a serving gateway (SGW) and a packet data network (PDN) gateway (PGW).

The list of components presented with respect toFIG. 2is not meant to be an exhaustive list of the components of a wireless network, but rather a list of components that are commonly used in communications through wireless network102.

User equipment104is a two-way communication device with advanced data communication capabilities, including the capability to communicate with other user equipment or computer systems through a network of transceiver stations or nodes as described above. User equipment104may also have the capability to allow voice communication. Depending on the functionality provided by user equipment104, it may be referred to as a data messaging device, a two-way pager, a cellular telephone with data messaging capabilities, a wireless Internet appliance, or a data communication device, with or without telephony capabilities.

Shown inFIG. 3is a block diagram of an illustrative embodiment of user equipment300. In this example, user equipment300is an example of user equipment104inFIG. 1andFIG. 2. User equipment300includes a number of components such as main processor302that controls the overall operation of user equipment300. Communication functions, including data and voice communications, are performed through communication subsystem304. Communication subsystem304receives messages from and sends messages to wireless network102, described above. In this illustrative embodiment of user equipment300, communication subsystem304may be configured in accordance with Universal Mobile Telecommunications System (UMTS) technology using the UMTS Terrestrial Radio Access Network (UTRAN) or Long Term Evolution (LTE) technology using Evolved UTRAN (E-UTRAN). Alternatively, communication subsystem304may be configured in accordance with the Global System for Mobile Communication (GSM) and General Packet Radio Services (GPRS) standards. New standards are still being defined, but it is believed that they will have similarities to the network behavior described herein, and it will also be understood by persons skilled in the art that the embodiments described herein are intended to use any other suitable standards that are developed in the future.

The wireless link connecting communication subsystem304with wireless network102represents one or more different radio frequency (RF) channels, operating according to defined protocols specified for the particular communication technologies being employed. With newer network protocols, these channels are capable of supporting both circuit switched voice communications and packet switched data communications.

Other wireless networks also may be associated with user equipment300in various implementations. The different types of wireless networks that may be employed include, for example, data-centric wireless networks, voice-centric wireless networks, and dual-mode networks that can support both voice and data communications over the same physical base stations. Combined dual-mode networks include, but are not limited to, Code Division Multiple Access (CDMA) or CDMA2000 networks, GSM/GPRS networks, as mentioned above, third-generation (3G) networks like EDGE and UMTS, and Long Term Evolution (LTE) networks. Some other examples of data-centric networks include WiFi 802.11, Mobitex™ and DataTAC™ network communication systems. Examples of other voice-centric data networks include Personal Communication Systems (PCS) networks like GSM and Time Division Multiple Access (TDMA) systems.

Some of the subsystems of user equipment300perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. By way of example, display310and keyboard316may be used for both communication-related functions, such as entering a text message for transmission over network102, and device-resident functions, such as a calculator or task list.

User equipment300can send and receive communication signals over wireless network102after required network registration or activation procedures have been completed. Network access is associated with a subscriber or user of user equipment300. To identify a subscriber, user equipment300requires a Subscriber Identity Module (SIM) or a Removable User Identity Module (RUIM) card326to be inserted into SIM/RUIM interface328in order to communicate with a network. SIM or RUIM card326is one type of a conventional “smart card” that can be used to identify a subscriber of user equipment300and to personalize user equipment300, among other things. SIM or RUIM card326includes a processor and memory for storing information.

Without card326, user equipment300is not fully operational for communication with wireless network102. By inserting SIM or RUIM card326into SIM/RUIM interface328, a subscriber can access all subscribed services. Services may include web browsing and messaging such as e-mail, voice mail, Short Message Service (SMS), and Multimedia Messaging Services (MMS). More advanced services may include point of sale, field service and sales force automation. Once SIM or RUIM card326is inserted into SIM/RUIM interface328, it is coupled to main processor302. In order to identify the subscriber, SIM or RUIM card326can include user parameters, such as an International Mobile Subscriber Identity (IMSI). An advantage of using SIM or RUIM card326is that a subscriber is not necessarily bound by any single physical user equipment. SIM or RUIM card326may store additional subscriber information for user equipment as well, including datebook or calendar information and recent call information. Alternatively, user identification information can also be programmed into flash memory308.

User equipment300is a battery-powered device and includes battery interface332for receiving one or more rechargeable batteries330. In at least some embodiments, battery330may be a smart battery with an embedded microprocessor. Battery interface332is coupled to a regulator (not shown), which assists battery330in providing power V+ to user equipment300. Although current technology makes use of battery330, future technologies, such as micro fuel cells, may provide the power to user equipment300.

User equipment300also includes operating system334and other programs336. Programs336are described in more detail below. Operating system334and programs336may be implemented as software components that are run by main processor302. Operating system334and programs336typically are stored as program code on a media readable by a processor, such as main processor302. Such readable storage media may include a persistent storage device, such as flash memory308, which may alternatively be a read-only memory (ROM) or similar storage element. Those skilled in the art will appreciate that portions of operating system334and programs336, such as specific device applications, or parts thereof, may be loaded temporarily into a volatile storage device, such as RAM306. Other software components also may be included, as is well known to those skilled in the art.

Programs336that control basic device operations, including data and voice communication applications, normally will be installed on user equipment300during its manufacture. Other programs336include message application338. Message application338can be any suitable software program that allows a user of user equipment300to send and receive electronic messages. Various alternatives exist for message application338, as is well known to those skilled in the art. Messages that have been sent or received by the user are typically stored in flash memory308of user equipment300, or some other suitable storage element in user equipment300. In at least some embodiments, some of the sent and received messages may be stored remotely from user equipment300, such as in a data store of an associated host system that user equipment300communicates with.

Programs336may further include device state module340, personal information manager (PIM)342, and other suitable modules. Device state module340provides persistence, i.e., device state module340ensures that important device data is stored in persistent memory, such as flash memory308, so that the data is not lost when user equipment300is turned off or loses power.

PIM342includes functionality for organizing and managing data items of interest to the user, such as, but not limited to, e-mail, contacts, calendar events, voice mails, appointments, and task items. A PIM application has the ability to send and receive data items via wireless network102. PIM data items may be seamlessly integrated, synchronized, and updated via wireless network102with the user equipment subscriber's corresponding data items stored or associated with a host computer system. This functionality creates a mirrored host computer on user equipment300with respect to such items. This can be particularly advantageous when the host computer system is the user equipment subscriber's office computer system.

User equipment300also includes connect module344, and IT policy module346. Connect module344implements the communication protocols that are required for user equipment300to communicate with the wireless infrastructure and any host system, such as an enterprise system, that user equipment300is authorized to interface with.

Connect module344includes a set of APIs that can be integrated with user equipment300to allow user equipment300to use any number of services associated with an enterprise system. Connect module344allows user equipment100to establish an end-to-end secure, authenticated communication pipe with the host system. A subset of applications for which access is provided by connect module344can be used to pass IT policy commands from the host system to user equipment300. This can be done in a wireless or wired manner. These instructions can then be passed to IT policy module346to modify the configuration of user equipment300. Alternatively, in some cases, the IT policy update can also be done over a wired connection.

IT policy module346receives IT policy data that encodes the IT policy. IT policy module346then ensures that the IT policy data is authenticated by user equipment300. The IT policy data can then be stored in flash memory306in its native form. After IT policy data is stored, a global notification can be sent by IT policy module346to all of the applications residing on user equipment300. Applications for which the IT policy may be applicable then respond by reading the IT policy data to look for IT policy rules that are applicable. After the IT policy rules have been applied to the applicable applications or configuration files, IT policy module346sends an acknowledgement back to the host system to indicate that the IT policy data was received and successfully applied.

In accordance with a disclosed embodiment, congestion response module348may be provided to adapt the bitrate of user equipment300in response to receiving packets marked “Congestion Experienced” or unmarked packets, using one or more rate adaptation sequences provided by network102or configured on user equipment300, as will be described in more detail below. Congestion response module348may include one or more stand alone modules, or may be implemented, in whole or in part, as part of another module, such as connect module344.

Other types of programs or software applications also may be installed on user equipment300. These software applications may be third party applications, which are added after the manufacture of user equipment300. Examples of third party applications include games, calculators, utilities, etc.

Additional applications can be loaded onto user equipment300through at least one of wireless network102, auxiliary I/O subsystem312, data port314, short-range communications subsystem322, or any other suitable device subsystem324. This flexibility in application installation increases the functionality of user equipment300and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using user equipment300.

Data port314enables a subscriber to set preferences through an external device or software application and extends the capabilities of user equipment300by providing for information or software downloads to user equipment300other than through a wireless communication network. The alternate download path may, for example, be used to load an encryption key onto user equipment300through a direct and thus reliable and trusted connection to provide secure device communication.

Data port314can be any suitable port that enables data communication between user equipment300and another computing device. Data port314can be a serial or a parallel port. In some instances, data port314can be a USB port that includes data lines for data transfer and a supply line that can provide a charging current to charge battery330of user equipment300.

Short-range communications subsystem322provides for communication between user equipment300and different systems or devices, without the use of wireless network102. For example, subsystem322may include an infrared device and associated circuits and components for short-range communication. Examples of short-range communication standards include standards developed by the Infrared Data Association (IrDA), Bluetooth, and the 802.11 family of standards developed by IEEE.

In use, a received signal, such as a text message, an e-mail message, or web page download, will be processed by communication subsystem304and input to main processor302. Main processor302will then process the received signal for output to display310or alternatively to auxiliary I/O subsystem312. A subscriber may also compose data items, such as e-mail messages, for example, using keyboard316in conjunction with display310and possibly auxiliary I/O subsystem312. Auxiliary subsystem312may include devices such as a touch screen, mouse, track ball, infrared fingerprint detector, or a roller wheel with dynamic button pressing capability. Keyboard316preferably is an alphanumeric keyboard or telephone-type keypad. However, other types of keyboards also may be used. A composed item may be transmitted over wireless network102through communication subsystem304.

For voice communications, the overall operation of user equipment300is substantially similar, except that the received signals are output to speaker318, and signals for transmission are generated by microphone320. Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, can also be implemented on user equipment300. Although voice or audio signal output is accomplished primarily through speaker318, display310can also be used to provide additional information, such as the identity of a calling party, duration of a voice call, or other voice call related information.

Referring now toFIG. 4, a block diagram of communication subsystem component304of user equipment300ofFIG. 3is shown. Communication subsystem304includes receiver450and transmitter452, as well as associated components, such as one or more embedded or internal antenna elements454and456, local oscillators (LOs)458, and a processing module, such as a digital signal processor (DSP)460. The particular design of communication subsystem304is dependent upon the communication network102with which user equipment300is intended to operate. Thus, it should be understood that the design illustrated inFIG. 4serves only as one example.

Signals received by antenna454through wireless network102are input to receiver450, which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection, and analog-to-digital (A/D) conversion. A/D conversion of a received signal allows more complex communication functions, such as demodulation and decoding, to be performed in DSP460. In a similar manner, signals to be transmitted are processed, including modulation and encoding, by DSP460. These DSP-processed signals are input to transmitter452for digital-to-analog (D/A) conversion, frequency up conversion, filtering, amplification and transmission over wireless network102via antenna456. DSP460not only processes communication signals, but also provides for receiver and transmitter control. For example, gains applied to communication signals in receiver450and transmitter452may be adaptively controlled through automatic gain control algorithms implemented in DSP460.

The wireless link between user equipment300and wireless network102can contain one or more different channels, typically different RF channels, and associated protocols used between user equipment300and wireless network102. An RF channel is a limited resource that must be conserved, typically due to limits in overall bandwidth and limited battery power of user equipment300.

When user equipment300is fully operational, transmitter452typically is keyed or turned on only when it is transmitting to wireless network102and is otherwise turned off to conserve resources. Similarly, receiver450is periodically turned off to conserve power until it is needed to receive signals or information during designated time periods.

One or more of the disclosed embodiments may be applied to types of communications and standards other than those described above with respect toFIGS. 1-4. For example, without limitation, the different illustrative embodiments may be implemented using LTE Advanced. Additionally, the wireless networks illustrated may take the form of or include 4G networks.

Turning now toFIG. 5, a diagram of data processing system500is depicted in accordance with an illustrative embodiment. In this example, data processing system500is an example of one implementation of processing system208in node202inFIG. 2. Data processing system500, or portions thereof, also may be used to implement one or more functions of user equipment300as illustrated inFIG. 3. In this illustrative example, data processing system500includes communications fabric502, which provides communications between processor unit504, memory506, persistent storage508, communications unit510, input/output (I/O) unit512, and display514.

Communications unit510, in these examples, provides for communication with other data processing systems or devices. In these examples, communications unit510is a network interface card. Communications unit510may provide communications through the use of either or both physical and wireless communications links.

Input/output unit512allows for the input and output of data with other devices that may be connected to data processing system500. For example, input/output unit512may provide a connection for user input through a keyboard, a mouse, and/or some other suitable input device. Further, input/output unit512may send output to a printer. Display514provides a mechanism to display information to a user.

Instructions for the operating system, applications, and/or programs may be located in storage devices516, which are in communication with processor unit504through communications fabric502. In these illustrative examples, the instructions are in a functional form on persistent storage508. These instructions may be loaded into memory506in order to be run by processor unit504. The processes of the different embodiments may be performed by processor unit504using computer implemented instructions, which may be located in a memory, such as memory506.

These instructions are referred to as program code, computer usable program code, or computer readable program code that may be read and run by a processor in processor unit504. The program code, in the different embodiments, may be embodied on different physical or computer readable storage media, such as memory506or persistent storage508.

Program code518is located in a functional form on computer readable media520that is selectively removable and may be loaded onto or transferred to data processing system500to be run by processor unit504. Program code518and computer readable media520form computer program product522. In one example, computer readable media520may be computer readable storage media524or computer readable signal media526. Computer readable storage media524may include, for example, an optical or magnetic disc that is inserted or placed into a drive or other device that is part of persistent storage508for transfer onto a storage device, such as a hard drive, that is part of persistent storage508. Computer readable storage media524also may take the form of a persistent storage, such as a hard drive, a thumb drive, or a flash memory that is connected to data processing system500. In some instances, computer readable storage media524may not be removable from data processing system500.

Alternatively, program code518may be transferred to data processing system500using computer readable signal media526. Computer readable signal media526may be, for example, a propagated data signal containing program code518. For example, computer readable signal media526may be an electro-magnetic signal, an optical signal, and/or any other suitable type of signal. These signals may be transmitted over communications links, such as wireless communications links, an optical fiber cable, a coaxial cable, a wire, and/or any other suitable type of communications link. In other words, the communications link and/or the connection may be physical or wireless in the illustrative examples.

In some illustrative embodiments, program code518may be downloaded over a network to persistent storage508from another device or data processing system through computer readable signal media526for use within data processing system500. For instance, program code stored in a computer readable storage media in a server data processing system may be downloaded over a network from the server to data processing system500. The data processing system providing program code518may be a server computer, a client computer, or some other device capable of storing and transmitting program code518.

As another example, a storage device in data processing system500is any hardware apparatus that may store data. Memory506, persistent storage508, and computer readable media520are examples of storage devices in a tangible form.

The illustrations of hardware components inFIGS. 1-5are not meant to imply physical or architectural limitations to the manner in which different illustrative embodiments may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be unnecessary in some illustrative embodiments. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined or divided into different blocks when implemented in different illustrative embodiments.

Turning now toFIG. 6, a block diagram illustrating communication environment600is depicted in accordance with an illustrative embodiment. Communication network100ofFIG. 1is an example of one implementation of communication environment600ofFIG. 6. Communication environment600includes one or more networks602in association with user equipment604. Wireless network102inFIG. 1is an example of one implementation of network602inFIG. 6. User equipment104inFIG. 1and user equipment300inFIG. 3are examples of user equipment604inFIG. 6. As discussed above, user equipment604may include a variety of devices, such as mobile wireless communication devices including pagers, cellular phones, cellular smart-phones, wireless organizers, personal digital assistants, computers, laptops, handheld wireless communication devices, wirelessly enabled notebook computers and the like. In operation, user equipment604is in communication with network602via wireless communication channel605in the manner described above. Thus, network602and user equipment604exchange data packets via wireless channel605.

Network602includes one or more network nodes606. Wireless network node202ofFIG. 2is one example of node606ofFIG. 6. Node606may comprise a base transceiver station, as described above. Generically, node606may include any equipment, device, group of devices, or functionality that sends, receives, or otherwise processes data packets as they pass through network602. Thus, node606may itself comprise user equipment, as described above, which is a part of or in communication with network602.

In accordance with an illustrative embodiment, node606includes a module for performing a function of congestion detection608. Any system or method currently known, or which becomes known, for detecting congestion on network602may be employed to implement this function. Congestion detection608preferably may include continually estimating a level of congestion at node606or at any other location in network602that may affect processing by network602of data packets to be delivered to or received from user equipment604. Congestion may be considered detected when a current level of congestion is greater than a selected threshold. Congestion is not detected when the current level of congestion is less than selected threshold.

The congestion estimate within node606, or another network element, may be a combined measure with many different measurements as inputs, such as one or more of radio related measurements of signal power, interference, or other radio related measurements, as well as other measurements, such as the amount of queued data to be processed in node606, queuing delays, or other measurements. Modifications to the congestion estimation, or to the determination of whether or not congestion is considered detected, may be used. Such modifications may include one or more of filtering of the congestion estimate, application of hysteresis at the congestion threshold, or other modifications. The congestion estimation method and the selected threshold employed for congestion detection608may vary depending on the specific network node606or other element in which congestion detection608is implemented or for which congestion is to be determined.

In accordance with an illustrative embodiment, network node606includes a module for performing a function of data packet marking610. Data packet marking610includes marking data packets to be transmitted to user equipment604. Data packets are marked with a marker indicating “Congestion Experienced” if congestion is considered detected. Data packets are not marked if congestion is not detected.

Packet marking indicating “Congestion Experienced” may include the use of markings currently used or as proposed for Explicit Congestion Notification. Such marking includes marking two bits in the Internet Protocol (IP) header of a packet as ‘11’. Marking a packet “Congestion Experienced” in accordance with an illustrative embodiment may employ other marking schemes, dependent upon the types of data and packets to be transmitted, and may include marking in the header and/or in other portions of a data packet.

Node606includes structures and functionality to transmit data packets612, including marked and unmarked packets, via wireless communication channel605, to user equipment604in a normal manner. Similarly, user equipment604includes structures and functionality to receive the data packets618transmitted from network602in a normal manner.

In accordance with an illustrative embodiment, transmissions of data packets between network602and user equipment604may be at one or more adaptable codec rates620. In accordance with an illustrative embodiment, a sender, such as node606, and a receiver, such as user equipment604, are built or adapted and configured to support multiple codec rates620. Multiple codec rates620also may be referred to as a mode set. Examples of multiple codec rates620include the Adaptive MultiRate codec rates of 4.75 kbps, 7.4 kbps, 12.2 kbps, etc.

In accordance with an illustrative embodiment, user equipment604includes congestion response module622. Functions of congestion response module622may be implemented in software, firmware, or the like, such as in software running on the main processor or another processor provided in user equipment604. Functions of congestion response module622include functions to detect marked data packets624received by user equipment604and functions to implement codec rate adaptation sequences626in response to detected marked and unmarked data packets received by user equipment604. As will be discussed in more detail below, codec rate adaptation sequences626may include codec rate reduction sequence628and codec rate increase sequence630.

In accordance with an illustrative embodiment, when there is no congestion, and absent any constraints unrelated to Explicit Congestion Notification, the highest codec rate in a mode set established between a sender and receiver is assumed to be used by the sender. When the receiver, such as user equipment604, receives packets marked “Congestion Experienced”, indicating congestion in network602, the receiver decides to which lower rate codec in the mode set to adapt to. This rate adaptation in response to congestion is defined by codec rate reduction sequence628. When congestion is cleared, unmarked data packets will be received and detected by the receiver. If one or more higher codec rates are available, the receiver decides to which higher rate codec to adapt to, or to remain at the current codec rate. This rate adaptation in response to clearing congestion is defined by codec rate increase sequence630.

Codec rate adaptation sequences626, including codec rate reduction sequence628and codec rate increase sequence630, may include system level configuration parameters that are provided by network602. Network provided codec rate adaptation sequences626may be static or dynamic. For example, codec rate adaptation sequence626parameters may be stored statically in a Home Subscriber System (HSS) as part of network602. Alternatively, codec rate adaptation sequence626parameters may be determined dynamically at a packet data network (PDN) gateway (PGW) on network602, for example, according to expected congestion and handling requirements and capacity. Codec rate adaptation sequences626from network602may be stored in network sender and receiver endpoints, such as user equipment604, as known parameters for a given user equipment604. Codec rate adaptation sequences626may be sent to the endpoints on attach or Tracking Area Update (TAU)/Routing Area Update (RAU)/Location Area Update (LAU) responses. For static codec rate adaptation sequences626, sequence parameters may be sent to the endpoints just once for a call or for multiple calls. Codec rate adaptation sequence626parameters may be delivered from network602to a receiving terminal, such as user equipment604, via system messages. For example, codec rate adaptation sequence626parameters may be delivered to user equipment604using user equipment attachment, user equipment service request, and handover procedures.

As an alternative to, or in addition to, rate adaptation sequences626provided by network602, endpoint senders and receivers, such as user equipment604, may be configured with preferred codec rate adaptation sequences626. In this case, the endpoints may adapt the codec rates according to the configuration in the manner described herein. If a receiver, such as user equipment604, with configured codec rate adaptation sequences626also receives codec rate adaptation sequences626from network602, an operational determination may be made to determine which of the two codec rate adaptation sequences626, from network602or configured on receiver604, will take precedence. In this case, network602may inform receiver604of the precedence or the precedence may be configured on receiver604. One or more of the codec rate adaptation sequences626or the precedence information configured on receiver604may be provided by an Open Mobile Alliance (OMA) Device Management (DM) object under operational policy.

If a codec rate adaptation sequence626, such as codec rate reduction sequence628or codec rate increase sequence630, is not specified by network602or configured on user equipment604, a default codec rate adaptation sequence626may be used. The default codec rate adaptation sequence626may follow the order of the codec rates in the codec set negotiated between user equipment604and network602at call setup. For example, if the negotiated codec rate set is (4.75 kbps, 7.4 kbps, 12.2 kbps), then the default codec rate reduction sequence628may be (12.2 kbps, 7.4 kbps, 4.75 kbps) and the default codec rate increase sequence630may be (4.75 kbps, 7.4 kbps, 12.2 kbps).

Codec rate parameter values for the codec rate adaptation sequences626may be indicated as scalar values. For example, codec rate adaptation sequence626rate parameter values 1, 2, and 3 may indicate corresponding mode set bitrates of 4.75 kbps, 7.4 kbps, and 12.2 kbps, respectively. Optionally, codec rate adaptation sequence626may indicate real codec rates for adaptation directly.

Codec rate reduction sequence628and codec rate increase sequence630may use the same set of rates for their respective rate adaptation sequences, but in a reverse direction or order. For example, if codec rate increase sequence630uses the sequence (4.75 kbps, 7.4 kbps, 12.2 kbps) for increasing the codec rate in response to congestion clearing, then codec rate reduction sequence628may use the sequence (12.2 kbps, 7.4 kbps, 4.75 kbps) for decreasing the codec rate in response to congestion detection.

Alternatively, two different sets of rates may be configured for the codec rate reduction sequence628and for the codec rate increase sequence630, one set of rates for reducing the codec rate in response to detecting congestion and a different set of codec rates for increasing the codec rate in response to congestion clearing. For example, the codec rate reduction sequence628might be (12.2 kbps, 4.75 kbps) with the codec rate increase sequence630being (4.75 kbps, 7.4 kbps, 12.2 kbps). In this example, when congestion is detected, the rate steps down in one step from 12.2 kbps to 4.75 kbps. However, when congestion is cleared, the codec rate steps up in two steps, from 4.75 kbps to 7.4 kbps and from 7.5 kbps to 12.2 kbps.

In accordance with an illustrative embodiment, if a data packet marked “Congestion Experienced” is received by a receiving terminal, such as by user equipment604, then the codec rate is reduced by one step within the set of the negotiated or specified codec rates or one step according to codec rate reduction sequence628. Codec rate reduction may be implemented by user equipment604by generating and sending to node606an appropriate codec rate change request648. At this point, codec rate reduction inhibit timer632, provided in user equipment604, is started. While codec rate reduction inhibit timer632is running, the codec rate will not be reduced further, even if another marked data packet is received during this time.

The length of time that codec rate reduction inhibit timer632runs after being started is referred to herein as codec rate reduction inhibit time634. Codec rate reduction inhibit time634preferably should be set to a value that is longer than the round trip time between the two endpoints in communication, such as between node606and user equipment604, plus some additional observation time. Setting of rate reduction inhibit time634thus should allow sufficient time for the receiver to request the reduced codec rate from the sender, for the sender to switch to the reduced rate, and then for the network element, such as node606, that was experiencing congestion and marking data packets “Congestion Experienced” to observe that congestion has been cleared and to stop marking packets. Any appropriate or desired length of time may be used for codec rate reduction inhibit time634in accordance with illustrative embodiments. In accordance with illustrative embodiments, codec rate reduction inhibit time634may be configurable636or fixed638. Codec rate reduction inhibit time634may be dynamically provided by network602, such as via a Non Access Stratum (NAS) or a call setup message.

If a rate reduction does not relieve congestion on network602, node606may continue to mark data packets in order to trigger a further reduction in the codec rate. If the receiving terminal receives a data packet marked “Congestion Experienced” after the codec rate reduction inhibit timer632times out, the receiving terminal may initiate the next lower rate codec adaptation, such as in accordance with codec rate reduction sequence628, if the current codec rate is not the lowest in the mode set.

If a congestion condition on network602has not improved for some time period after network602has triggered a codec rate reduction, by marking data packets “Congestion Experienced” to indicate to receivers to initiate codec rate reduction for congestion control, then network602may determine that it is necessary to notify the receivers of the need for continued codec rate reduction. Network602may notify receivers, such as user equipment604, of the need for continued codec rate reduction to reduce network congestion by sending specific notifications on codec rate adaptation continuation to the receivers. Thus, in accordance with an illustrative embodiment, node606may include a module or function for providing codec rate adaptation continuation notification614.

Upon receiving a codec rate adaptation continuation notification, a receiver, such as user equipment604, may adapt to the next lower rate codec rate, if the current codec rate is not the lowest one. In certain special situations, such as when network602is heavily congested, the codec rate adaptation continuation notification may notify the receiver to initiate immediately the lowest codec rate. Thus, a codec rate adaptation continuation notification message sent by network602, such as by node606, for example, via broadcasting or specific message to network endpoints, such as user equipment604, may include a codec rate adaptation continuation notification type indicator that may take on one of two values, to indicate either a codec rate adaptation to the next lower codec rate or a codec rate adaptation to the lowest codec rate.

Other than sending codec rate adaptation continuation notifications to receivers, such as user equipment604, for the receivers to initiate continued codec rate reductions to senders, such as node606, codec rate adaptation continuation notifications can be sent by network602to senders, such as node606, directly. In this manner, senders may be notified directly to reduce the sending codec rate, without initiation from receivers. This may speed up congestion control in some cases.

In accordance with illustrative embodiments, use of codec rate adaptation continuation notifications to reduce congestion may be inclusive or exclusive with codec rate adaptation for congestion reduction using “Congestion Experienced” marking of data packets as described above. In cases where continued codec rate adaptation in accordance with illustrative embodiments is insufficient to clear a congestion condition, network602may employ other types of mechanisms for congestion control, such as dropping packets or services.

In accordance with an illustrative embodiment, when a codec rate is reduced in response to user equipment604receiving a data packet marked “Congestion Experienced”, codec rate increase timer640, provided in user equipment604, may be started. Codec rate increase timer640is adapted to time codec rate increase time642. Codec rate increase time642typically may be much longer than codec rate reduction inhibit time634. For example, codec rate increase time642may be selected to be ten seconds or more. Any other appropriate or desired length of time may be used for codec rate increase time642in accordance with an illustrative embodiment. Using a longer time period for codec rate increase time642is preferable, because increasing the codec rate after congestion is cleared is much less critical than timely codec rate reduction for congestion control. Use of a longer codec rate increase time642can also reduce the potential for codec adaptation oscillation between codec rate reduction and increase. At least a portion of codec rate increase time642may be random644. Use of a random element in codec rate increase time642also helps to prevent oscillation between codec rate reduction and increase that might result if many user devices supported by a network node simultaneously request codec rate increases as their individual codec rate increase times simultaneously expire.

In accordance with an illustrative embodiment, when codec rate increase timer640expires, the codec rate may be increased by one step within the set of negotiated codec rates or increased one step according to codec rate increase sequence630. A codec rate increase may be implemented by user equipment604by generating and sending to node606an appropriate codec rate change request648. When a data packet marked “Congestion Experienced” is received while codec rate increase timer640is running, then the receiver, such as user equipment604, will reduce the codec rate, in the manner described above, and codec rate increase timer640will restart646. In addition, codec rate increase timer640will restart646when codec rate increase timer640expires, in order to allow for the codec rate to increase again when codec rate increase timer640expires. In this manner, illustrative embodiments provide a mechanism whereby the codec rate can gradually step back up to its highest value, absent any other constraints.

In accordance with illustrative embodiments, codec rate reduction inhibit timer632and codec rate increase timer640may operate independently. Alternatively, codec rate increase timer640may not be reset646while codec rate reduction inhibit timer632is running. However, because codec rate reduction inhibit time634is likely to be very short in comparison to codec rate increase time642, there is likely to be very little difference in performance between the two options.

In accordance with an alternative illustrative embodiment, data packets marked “Congestion Experienced” that are received by user equipment604may be ignored for purposes of restarting codec rate increase timer640while codec rate increase timer640is running. In this case, codec rate increase timer640is not restarted when marked packets are received while codec rate increase timer640is running. In this alternative embodiment, when codec rate increase timer640expires, user equipment604checks whether or not marked packets were received while codec rate increase timer640was running. If no marked packets were received while codec rate increase timer640was running, then the codec rate may be increased and codec rate increase timer640may be restarted. However, if marked packets were received while codec rate increase timer640was running, then codec rate increase timer640is restarted without increasing the codec rate. In this case, the next possible time when the codec rate can be increased is at the next expiration of codec rate increase timer640. As compared with the approach of restarting codec rate increase timer640whenever marked packets are received while codec rate increase timer640is running, as described above, this alternative approach may be simpler. However, in cases where a marked packet is received just after codec rate increase timer640is started, and no other marked packets are received while codec rate increase timer640is running, this alternative approach has the effect of almost doubling the time to increase the codec rate, because user equipment604must wait for almost two entire codec rate increase time periods to expire before increasing the codec rate.

Explicit Congestion Notification based codec adaptation for congestion control as disclosed herein may not be desirable for priority users and priority or emergency services, except in catastrophic situations. Thus, in accordance with an illustrative embodiment, user equipment604may include appropriate functionality to provide for priority/emergency handling650.

Emergency services usually are carried over emergency bearers, such as connections established with either an emergency attach or an emergency Public Data Network (PDN) connection establishment. Thus, network602may not enable Explicit Congestion Notification as described herein for emergency bearers and priority/emergency handling650for user equipment604may include knowing that codec rate adaptation as described herein will not be applied on emergency bearers.

In accordance with an illustrative embodiment, under normal operation, priority/emergency handling650provides that codec rate adaptation as described herein will not be applied to priority users and priority/emergency services. However, if a catastrophic condition occurs, massive numbers of simultaneous service requests, such as emergency calls, may be made to the system. In accordance with an illustrative embodiment, priority/emergency handling650may provide for applying codec rate adaptation as disclosed herein to such emergency calls if the number of such emergency calls exceeds a specific threshold number or the percentage of all calls that are emergency calls exceeds a threshold percentage. Handling of emergency calls when such catastrophic conditions occur may be realized by network602by marking data packets “Congestion Experienced” in the packet delivery for emergency services when a catastrophic condition occurs and otherwise not marking such data packets.

In accordance with an illustrative embodiment, priority/emergency handling650may provide that very high priority user equipment604, by a very special user, need not implement codec rate reduction as described herein per policy control rule and/or authorization by the Home Public Land Mobile Network (HPLMN) operator. Very high priority user equipment may not be allowed to ignore codec rate reduction by a Visited Public Land Mobile Network (VPLMN) operator.

The illustration ofFIG. 6is not meant to imply physical or architectural limitations to the manner in which different embodiments may be implemented. Other components in addition and/or in place of the ones illustrated may be used. Some components may be unnecessary in some embodiments. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined and/or divided into different blocks when implemented in different advantageous embodiments.

An example of codec rate reduction in accordance with an illustrative embodiment is illustrated inFIG. 7. The example presented inFIG. 7illustrates codec rate reduction in accordance with an illustrative embodiment when congestion in the downlink direction, from network to user equipment, is detected within a network node. Initially, data packets from a sender peer Multimedia Telephony Services for IP Multimedia Subsystem (MTSI) client702are delivered via network704and network node706, such as an eNodeB network node, to an MTSI client in user equipment (UE)708at a rate of 12.2 kbps. Congestion is not initially experienced, so data packets are not marked “Congestion Experienced” (CE) by node706. At some point in time, congestion is detected in the node710. In response to detecting congestion, node706begins to mark data packets “Congestion Experienced”. Such a marked packet is received by user equipment708. In response to receiving a marked packet, user equipment708reduces the codec rate by one step712. Codec rate reduction by user equipment708includes sending a packet with a Codec Mode Request (CMR)714requesting a rate change to 7.4 kbps back through node706and network704to client702. At the same time as requesting the rate change, user equipment708starts codec rate reduction inhibit time716and codec rate increase time718running.

As congestion continues to be detected in node706data packets continue to be marked. However, as long as codec rate reduction inhibit time716is running, marked packets received by user equipment708do not result in further rate reductions. Eventually, the requested rate change is received by client720, and the transmission rate is reduced to 7.4 kbps, as requested by user equipment708. Packets continue to be marked by node706until, eventually, the reduced codec rate results in clearing the congestion in node706. Node706detects this relief in congestion722, and thus stops marking packets at this point. At the point in time where codec rate inhibit time716expires721, the congestion has been cleared, packets are not being marked by node706, and thus no further codec rate reduction is initiated by user equipment708.

An example of codec rate increase in accordance with an illustrative embodiment is illustrated inFIG. 8. The example presented inFIG. 8illustrates codec rate increase in accordance with an illustrative embodiment in the downlink direction, from network to user equipment, when there is no congestion detected within a network node. Initially, data packets from a sender peer Multimedia Telephony Services for IP Multimedia Subsystem (MTSI) client802are delivered via network804and network node806, such as an eNodeB network node, to an MTSI client in user equipment (UE)808at a rate of 5.9 kbps. Congestion is not detected in node812, so data packets are not marked “Congestion Experienced” (CE) by node806. A codec rate increase timer is running as a result of an earlier rate reduction814. As long as the codec rate increase timer is running, client808does not attempt to increase the codec rate, even though data packets received by client808are not marked, indicating no congestion.

Eventually, the codec rate increase timer expires816. In response to the codec rate increase timer expiring, user equipment808increases the codec rate by one step818. The codec rate increase by user equipment808includes sending a packet with a Codec Mode Request (CMR)820, requesting a rate increase to 7.4 kbps, back to client802via node806and network804. At the same time as requesting the rate increase, user equipment808restarts the codec rate increase timer822. Eventually, the rate increase request from user equipment808is received by client802, and client802increases the transmission rate to 7.4 kbps824, as requested. The increased codec rate does not result in congestion, so data packets continue not to be marked.

Eventually, the restarted codec rate increase timer expires826. In response to the codec rate increase timer expiring again, user equipment808increases the codec rate by another step828. This codec rate increase by user equipment808includes sending a packet with a Codec Mode Request (CMR)830, requesting a rate increase to 12.2 kbps, back to client802via node806and network804. At the same time as requesting the rate increase, user equipment808restarts the codec rate increase timer832. Eventually, the rate increase request from user equipment808is received by client802, and client802increases the transmission rate to 12.2 kbps834, as requested. The further increased codec rate does not result in congestion, so data packets continue not to be marked.

The flowchart ofFIG. 9illustrates an example method900for codec rate reduction in accordance with an illustrative embodiment. Method900may be implemented, for example, in user equipment, such as in user equipment300ofFIG. 3. Received data packets are examined, preferably continuously, to determine when a packet marked “Congestion Experienced” is detected (step902). When a marked packet is detected, the rate is reduced, if possible (step904). For example, step904may include reducing the codec rate by one step within a set of the negotiated or specified codec rates or one step according to a codec rate reduction sequence. It may not be possible to reduce the codec rate if the codec rate is already at the lowest rate. Step904may include generating and sending an appropriate codec rate change request from user equipment to the network. The codec rate reduction inhibit timer is started (step906), preferably at substantially the same time or simultaneously with step904. Steps904and906may be performed in any order. Until the codec rate reduction inhibit timer expires, no further action is taken to reduce the rate, even if another marked data packet is received during this time. When it is determined that the codec rate reduction inhibit timer has expired (step908), the method returns to step902to look for marked data packets indicating that further rate reduction is required.

The flowchart ofFIG. 10illustrates an example method1000for codec rate increase in accordance with an illustrative embodiment. Method1000may be implemented, for example, in user equipment, such as in user equipment300ofFIG. 3. Method1000begins by starting a codec rate increase timer (step1002). It is determined whether a packet marked “Congestion Experienced” is received during the time that the codec rate increase timer is running (step1004). If a marked packet is received during the time that the codec rate increase timer is running, the codec rate increase timer is restarted, by returning to step1002. It is determined when the codec rate increase timer expires (step1006). When the codec rate increase time expires, it is determined whether the current rate is the highest rate (step1008). If it is determined that the current rate is the highest rate, then no further rate increase is possible, and the codec rate increase timer is restarted by returning to step1002. If it is determined that the current rate is not the highest rate, then the codec rate is increased (step1012). Step1012may include increasing the codec rate by one step within a set of negotiated codec rates or by one step according to a codec rate increase sequence. Step1012may include generating and sending from user equipment an appropriate codec rate change request. The codec rate increase timer is restarted after increasing the rate, by returning to step1002.

The flowchart ofFIG. 11illustrates an example of another method1100for codec rate increase in accordance with an illustrative embodiment. Method1100may be implemented, for example, in user equipment, such as in user equipment300ofFIG. 3. Method1100begins by starting a codec rate increase timer (step1102). It is determined when codec rate increase timer expires (step1104). When codec rate increase timer is determined to have expired, it is determined whether a packet marked “Congestion Experienced” was received during the rate increase time timed by the codec rate increase timer (step1106). If a marked packet was received during the rate increase time, the codec rate increase timer is restarted, by returning to step1102. If a marked packet was not received during the rate increase time, it is determined whether the current rate is the highest rate (step1108). If the current rate is the highest rate, no increase in the rate is possible, and the codec rate increase timer is restarted by returning to step1102. If the current rate is not the highest rate, the codec rate is increased (step1112). Step1112may include increasing the codec rate by one step within a set of negotiated codec rates or by one step according to a codec rate increase sequence. Step1112may include generating and sending from user equipment an appropriate codec rate change request. The codec rate increase timer is restarted after increasing the rate, by returning to step1002.

The flowchart ofFIG. 12illustrates another example of a method1200for rate adaptation in accordance with an illustrative embodiment. In accordance with method1200, the adaptation of codec rate using Explicit Congestion Notification (ECN) is controlled by two parameters, the code rate reduction inhibit time and the code rate increase time. These parameters may be configured into a Multimedia Telephony Services for IP Multimedia Subsystem (MTSI) client based on operator policy, for example, using Open Mobile Alliance-Device Management (OMA-DM). If the parameters are not configured, then default values of 200 ms and 10 seconds, respectively, may be used.

It is determined if a receiving MTSI client in terminal that supports and has negotiated ECN detects an ECN “Congestion Experienced” (CE) marking in a received Internet Protocol/User Datagram Protocol/Real-time Transport Protocol (IP/UDP/RTP) packet (step1202). If a marked packet is received, it is determined whether the receiving MTSI client is already operating at the lowest codec rate (step1204). If the MTSI client is not already operating at the lowest codec rate, the receiving MTSI client in terminal reduces the codec rate by one codec rate within the set of negotiated codec rates (step1206). The receiving MTSI client in terminal notifies the sender of the new code rate via the Codec Mode Request (CMR) bits in the RTP payload if supported by the codec and via a Temporary Maximum Media Stream Bit Rate Request (TMMBR) message if the RTP payload for the codec does not support a CMR field (step1208). The receiving MTSI client in terminal starts a codec rate reduction inhibit timer with the value of the codec rate reduction inhibit time (step1210). The receiving MTSI client in terminal starts or, if already started running, restarts a codec rate increase timer with the value of the codec rate increase time (step1216).

It is determined whether the codec rate reduction inhibit timer is running (step1212). If the codec rate reduction inhibit timer is running, the receiving MTSI client in terminal will not act on the ECN marking of received IP/UDP/RTP packets (step1214). If the codec rate reduction inhibit timer expires, the receiving MTSI client in terminal shall again act on the ECN marking of received IP/UDP/RTP packets.

It is determined whether the codec rate increase timer expires (step1218). It is determined if there is no ECN-CE marked IP/UDP/RTP packet received during the time period (step1220). It is determined whether the rate is already at the highest codec rate (step1222). If the codec rate timer expires and there is no ECN-CE marked IP/UDP/RTO packet received during the time period and the rate is not already at the highest codec rate the MTSI client in terminal increases the codec rate by one codec rate within the set of negotiated codec rates (step1224). The receiving MTSI client in terminal notifies the sender of the new codec rate via the CMR bits in the RTP payload, if supported by the codec, and via a TMMBR message if the RTP payload for the codec does not support a CMR field (step1226). The receiving MTSI client in terminal then starts the codec rate increase timer with the value of the codec rate increase time.

The flowcharts and block diagrams in the different depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of apparatus and methods in different illustrative embodiments. In this regard, each block in the flowchart or block diagrams may represent a module, segment, function, or a portion of an operation or step. In some alternative implementations, the function or functions noted in the block may occur out of the order noted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

The description of the different illustrative embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the embodiments to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. In the illustrative examples, the user equipment has been described with respect to a mobile phone. The different illustrative embodiments may be applied to other types of platforms in addition to or in place of the ones described, such as a mobile platform, a stationary platform, a land-based structure, an aquatic-based structure, a space-based structure, a smart phone, a personal digital assistant, a desktop computer, a server computer, a set-top box, a game console, a workstation, and any other suitable platform. A component may be included in a platform in a number of different ways. For example, the component may be located inside the platform, outside of the platform, formed as part of the platform, mechanically secured to the platform, or otherwise associated with the platform.

The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.