Method and system for maintaining wireless links in a communication network

A method of operating a communication system comprises sending a frame by an access node to a wireless device where the frame comprises a packet. A counter is initialized and a timer for each frame is initiated. The method continues with the access node determining if a response associated with the packet is received before the expiration of the timer. If the response is received prior to the expiration of the timer, the counter and the timer are reset. If a response is not received prior to the expiration of the timer, the counter is incremented. Upon the counter meeting a criteria of a certain quantity of lost packets, the access node performs a synchronization process.

TECHNICAL BACKGROUND

Wireless networks commonly perform multiple processes when establishing communication sessions with wireless devices. These processes may be referred to as network entry processes. One such process is sometimes referred to as a ranging process or random access channel (RACH) process. Ranging between the wireless network and a wireless device allows the wireless device to synchronize the uplink (UL) connection with the network by maintaining timing, frequency and power-levels for the UL connection.

Wireless communication devices commonly communicate at various layers with wireless communication networks. Links established at lower layers allow communications to commence at upper layers. The failure of a lower layer link may cause the failure of upper layer links.

In many cases, wireless links may degrade due to various factors or conditions. For example, the wireless link may experience fading due to the mobility of the wireless device or the over-the-air conditions that exist at a particular point in time. Such a degradation of a wireless link may cause upper layer links, such as a network connection, to fail. In some instances, the network may not know that the link to a particular wireless device has failed and the network may needlessly continue to send data destined for the wireless device, wasting valuable network resources.

One aspect that affects user experiences and device performance is the link status between a wireless device and the network. Maintaining proper link quality reduces delay and latency and improves user experiences. In contrast, when a device is not have properly adjusted wireless links with a network, fundamental operations can be inhibited.

OVERVIEW

A method of operating a communication system comprises sending a frame by an access node to a wireless device where the frame comprises a packet. A counter is initialized and a timer for each frame is initiated. The method continues with the access node determining if a response associated with the packet is received before the expiration of the timer. If the response is received prior to the expiration of the timer, the counter and the timer are reset. If a response is not received prior to the expiration of the timer, the counter is incremented. Upon the counter meeting a criteria of a certain quantity of lost packets, the access node performs a synchronization process.

Another method of operating a communication system is also provided. A communication transmission is initiated from an access node to a wireless device. A frame that includes a packet that requires a response is sent by the access node to the wireless device. A counter is initialized and a timer for each frame is initiated. The method continues with the access node determining if the response associated with the packet is received before the expiration of the timer. If the response is received prior to the expiration of the timer, the counter and the timer are reset. If a response is not received prior to the expiration of the timer, the counter is incremented. Upon the counter meeting a criteria of a certain quantity of lost packets, the access node performs a synchronization process and stops the communication transmission to the wireless device.

DETAILED DESCRIPTION

FIG. 1illustrates communication system100. Communication system100includes wireless device101, network access node105, and communication network109. Wireless device101and network access node105communicate over wireless link103. Network access node105and communication network109communicate over communication link108.

FIG. 2illustrates process200describing the operation of communication system100. Network access node105sends a frame that includes a packet to wireless device101(Step201). If a response by wireless device101is required for the packet, a counter is initialized and a timer is initiated (Steps202&203). If a response associated with the packet is received before the expiration of the timer, the process200begins again (Step204).

If a response is not received at network access node105before the expiration of the timer, the counter is incremented (Step205). When the counter reaches a threshold, network access node105performs a synchronization process (Steps206&207).

The synchronization process allows wireless device101to adjust its UL (uplink) timing and power control levels with network access node105over wireless link103. In some examples, the UL synchronization process may be referred to as a ranging process or random access channel (RACH) process for establishing initial UL transmissions over wireless link103.

Referring back toFIG. 1, wireless device101is any device capable of communicating wirelessly with network access node105. Wireless device101comprises communication interface and processing elements configured to operate as described herein for wireless device101. Communication interface elements may include an antenna (or antennas) coupled to Radio Frequency (RF) communication circuitry that processes RF signals received over the antenna. The RF communication circuitry typically includes at least an amplifier, filter, modulator, and signal processing circuitry. Wireless device101may also include a user interface, memory device, software, processing circuitry, or some other communication components. Wireless communication device101may be a phone, computer, e-book, mobile Internet appliance, wireless network interface card, media player, game console, or some other wireless communication apparatus—including variations or combinations thereof.

Network access node105comprises RF communication circuitry and an antenna. The RF communication circuitry typically includes an amplifier, filter, RF modulator, and signal processing circuitry. Network access node105may also comprise a router, server, memory device, software, processing circuitry, cabling, power supply, network communication interface, structural support, or some other communication apparatus. Network access node105could be a base station, Internet access node, telephony service node, wireless data access point, or some other wireless communication system—including variations or combinations thereof.

Communication network109comprises any network or collection of networks capable of communicating with network access node105over communication link108. Examples of communication network109include a Wide Area Network (WAN), Local Area Network (LAN), internet, intranet, public switch telephone network (PSTN), wireless communication network, cable multi-service operator (MSO) network, or any combination or variation thereof.

Wireless link103uses the air or space as the transport media. Wireless link103may use various protocols, such as Code Division Multiple Access (CDMA), Evolution Data Only (EVDO), Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile Communication (GSM), Long Term Evolution (LTE), Wireless Fidelity (WIFI), High Speed Packet Access (HSPA), or some other wireless communication format.

Communication link108uses metal, glass, air, space, or some other material as the transport media. Communication link108could use various communication protocols, such as Time Division Multiplex (TDM), Internet Protocol (IP), Ethernet, communication signaling, CDMA, EVDO, WiMAX, GSM, LTE, WIFI, HSPA, or some other communication format—including combinations thereof. Communication link108could be a direct link or may include intermediate networks, systems, or devices.

In operation, a user operates wireless communication device101to establish communication sessions between wireless device101and communication network109. For example, a user may operate wireless device101to place a phone call, check an email account, browse the Internet, or otherwise communicate with a destination via communication network109.

In order to exchange communications in this manner, wireless communication device101first establishes wireless link103with network access system105. Upon establishing wireless link103, wireless device101performs a network entry process to establish an initial network connection with communication network109. The network entry process may comprise several steps, at the completion of which wireless device101is able to exchange communications with communication network109.

At times, the quality of wireless link103may vary. For example, the signal strength of wireless link103as measured by wireless device101may increase or decrease due to a variety of factors. Fluctuations in signal strength may occur because of mobility of wireless device101, fast fading, shadow fading, or combinations of these factors. In fact, the quality of wireless link103may suffer so greatly that wireless link103is dropped, thereby inhibiting wireless device101from exchanging communication sessions over the network connection with communication network109.

Referring toFIG. 1once again, an example is illustrated showing a possible scenario where packets are lost between network access node105and wireless device101due to link degradation of link103because of the mobile nature of wireless device101. As wireless device101moves from one geographic location to another (as illustrated by the dotted line), link103experiences a degradation in signal quality. If the link quality degrades below a certain threshold, packets may be lost that are sent by network access node105to wireless device101. After a certain number of packets are lost as determined by the process illustrated inFIG. 2, network access node105invokes the UL synchronization process.

As in other communication systems, state synchronization among different entities in wireless communication systems is important for proper system operations, including state synchronization between a wireless device and a wireless network.

State synchronization means that state information, including the wireless device's operation mode (e.g. active mode or idle mode) as well as context associated with the wireless device, is retained at both ends. Retaining this context information is important because a wireless network's operating behavior towards a wireless device (and vice versa) would be different depending on the knowledge of the overall connection state between them, such as radio link state, whether the device is in idle mode or sleep mode or active mode, and so on. For example, when the wireless device is in idle mode and there is incoming data for the wireless device, the network will page the wireless device. In contrast, when the wireless device is in active mode, the network will simply send packets to the wireless device. Hence, it is essential for the device and the network to maintain and synchronize state information, so that the device and the network can at all times be aware of each other's state.

Improved synchronization between the wireless device and the network will avoid many problems. For example, due to lack of synchronization, when a wireless device experiences a degradation of service over the wireless link, the network may continue to send data destined for the wireless device wasting valuable network resources.

Disclosed herein are mechanisms to provide a wireless network with the status of the wireless link to a wireless device and allow for prompt initiation of link maintenance mechanisms. This will allow the network to maintain and synchronize state information between the wireless device and network to improve network operations and performance.

FIG. 3illustrates a network architecture suitable for the WiMAX wireless interface protocol. However, it should be understood that other wireless protocols could be used, as well as other network architectures. Examples of other suitable wireless protocols include WCDMA, CDMA2000, CDMA, EVDO, GSM, LTE, WIFI, and HSPA, as well as other variations and combinations thereof.

Continuing withFIG. 3, communication system300is illustrated and includes wireless communication device (wireless device)301, base station305, base station306, access service network (ASN) gateway307, service network309, public switched telephone network319, and Internet Protocol (IP) network329.

Mobile station301and base station305communicate over wireless link303. Base station305and access gateway307communicate over link302. Base station system306and access gateway system307communication over link312. Access gateway system307and communication network309communicate over communication link308.

Mobile station301comprises any device capable of communicating with service network309and thus, with PSTN319and IP network329over a wireless interface with base station systems305and306over an air interface. Mobile phones, portable computers, mobile media devices, and network interface cards are examples of such devices. Mobile station301may sometimes be referred to as a mobile station (MS).

Base stations305and306provide the wireless interface to mobile station301, over which mobile station301exchanges communications with service network309. Base stations305and306provide functions such as mobility management, hand off provisioning and control, radio resource management, quality of service enforcement, and session management, as well as other functions.

ASN gateway307provides a traffic aggregation point for base stations305and306. Additional functions may include location management and paging, radio resource management and admission control, subscriber profile management, AAA functionality, and quality of service provisioning and management.

Service network309provides mobile station301with connectivity to IP network319, and connectivity to PSTN319. It should be understood that service network309could provide connectivity to other networks as well, such as a 3GPP/3GPP2 network, an intranet, LAN, WAN, public networks, corporate networks, or the like. Service network309may include elements such as AAA servers that provide authentication and authorization services to devices, such as mobile station301. Service network309handles IP address management, roaming support, location management, and interworking of communications to formats suitable for other networks, such as PSTN319.

It should be understood that any of the functions described as pertaining to base stations305and306, ASN gateway307, or service network309could reside in or be performed by any of those elements. In addition, the elements themselves could be combined or otherwise contained within each other. For example, ASN gateway could be contained in or combined with at least one of base stations305and306.

FIG. 4is a flow diagram illustrating process400that describes the operation of communication system300to improve synchronization between mobile stations and base stations. In particular, process400provides an example quickly detecting a failed link. This is accomplished by base station305counting the number of packets that are in a frame that fail to receive responses from mobile station301. Upon reaching a certain number of lost packets, base station305invokes a link maintenance process.

Referring again toFIG. 3, mobile station301has established wireless connection303with base station system305. Wireless connection303may be considered a layer 1, or physical layer link. Likewise, mobile station301has established a network connection with service network309by performing a network entry process. The network entry process may include steps such as scanning for downlink channels, synchronizing with the downlink of a serving base station, obtaining uplink parameters, ranging, negotiating basic capabilities, authorization and key exchange, network registration, obtaining an IP address, obtaining time of day, transferring operational parameters, and establishing provisioned parameters. It should be understood that some steps could be omitted and other, different steps included in a full network entry process.

Mobile station301is initially located in a geographic area and exchanges communications over the network connection. The network connection may be considered an upper layer link relative to layer 1 link wireless connection303. For example, the network connection may be a layer 2 or layer 3 connection.

The communications are exchanged using context information that identifies the network connection. Examples of context information include internet protocol (IP) addresses, media access control (MAC) identifiers, and the like. Establishing the network connection can be referred to as “entering” a service network that provides mobile station301with access service. The access service allows mobile station301to communicate over service network309with destinations in PSTN319or IP network329. For example, a user operating mobile station301may place phone calls, browse the world-wide web, check email, or otherwise utilize voice, video, media, or data services provided by service network309.

Referring now toFIG. 4, during a communication session between mobile station301and base station305, base station305maintains a counter, n, for tracking consecutive lost packets (Step401). Initially, the counter n is set at 0. For each frame k, base station305sends m(k) packets to mobile station301where packet i(k)(i(k)=1, 2, . . . , m(k)) requires responses from mobile station30lwithin time T(i,k) (Steps402&403). Each time a response is received at base station305, base station305resets n to 0, discards any tracking data, restarts the tracking from the next frame (Steps404,405, &406).

If no response is received from mobile station301for any of the m(k) packets within the time T(i,k), the counter n is incremented by 1 (Steps404&407). Frames are counted containing packets requiring responses in this fashion until n=N, where N is that largest count of lost packets reasonable for this link and that is negotiated between base station305and mobile station301(Steps407&408). When n=N, base station305invokes the link maintenance mechanisms (Steps408&409) that is initiated by sending an unsolicited RNG-RSP (ranging response) message to mobile station301.

Retransmissions of the same packet may be considered a new transmission. Additionally, packet the do not require responses from mobile station301are not considered when incrementing counter n or initiating timer T(i,k). Messages that are considered for this process may include management messages in addition to data payload messages. Some management messages require responses from mobile station301when sent by base station305. Further, for HARQ packets, both ACK and NACK messages are considered responses from mobile station301.

Hybrid automatic repeat request (HARQ) is a mechanism in packet networks that provides for error control when sending and receiving packets of data. When a packet is sent, the receiver sends back a HARQ ACK (acknowledgement) or HARQ NACK (negative acknowledgement) message back to the sender to acknowledge the successful or unsuccessful reception of the packet. HARQ is one possible example of packets that require responses from mobile station301.

It should also be noted that timer T(i,k) may vary for each packet thus resulting in expiration of timers in a different order from when they were sent by base station305.

Ranging is a link maintenance UL synchronization process utilized in WiMAX and CDMA. Typically, mobile station301will initiate the ranging process at the request of base station305. Initial ranging allows mobile station301to obtain the relative timing, frequency, and power-level adjustment required to maintain the UL link with base station305. Because the quality of wireless link303fluctuates, base station305will monitor link303by periodically performing ranging. As stated above, fluctuations with link305may be caused by the mobility of mobile station301, fast fading, shadow fading, or combinations of these factors.

Referring toFIG. 3once again, an example is illustrated showing a possible scenario when packets are lost between base station305and mobile station301due to link degradation of link303because of the mobile nature of mobile station301. As mobile station301moves from one geographic location to another (as illustrated by the dotted line), link303experiences a degradation in signal quality. If the link quality degrades below a certain threshold, packets may be lost that are sent by base station305to mobile station301. After N number of packets are lost as determined by the process illustrated inFIG. 4, base station305invokes the link maintenance mechanisms.

FIG. 5is an operational flow diagram further illustrating the operation of communication system300. InFIG. 5, an example is provided where base station305initiates a link maintenance process when mobile station301fails to respond according to the process illustrated inFIG. 4.

In this example, counter n is set to 0. In frame1, two data packets1(1) and2(1) are sent by base station305to mobile station301. These packets have HARQ employed that requires either an ACK or NAK response from mobile station301. The timers are set for each packet at T(1,1) and T(2,1) respectively. When there is not a response from mobile station301prior to the expiration of the timers T(1,1) and T(2,1), counter n is incremented by 1 and is now set at 1.

In frame2, there are no packets sent that require a response. Thus, counter n is unaffected and a timer is not initiated. Frame3is sent by base station305that contains a MAC management message that requires a response from mobile station301within time T(1,3). When no response is received, counter n is incremented by 1 and is now set at 2. Packets requiring responses are sent in the next 8 frames by base station305and in each case, timers T(1,4) to T(1,11) expire without receiving a response from mobile station301. Further, counter n is incremented by 1 each time and after the expiration of timer T(1,11), counter n=10. In this example, the number of lost packets is set at N=10 and thus base station305ceases transmitting data to mobile station301and invokes the link maintenance process by sending an unsolicited RNG-RSP message to start the ranging procedure.

As seen in this example, in cases where mobile station301has left base station305due to mobility or if the link conditions degrade due to shadowing or the like, this process invokes the link maintenance mechanisms much sooner than in previous link detection systems. Further, in cases where the transmissions requiring responses are all HARQ messages, the duration to invoke the link maintenance procedures are shortened to less than one second. Existing processes to invoke link maintenance procedures may take tens of seconds. This delay in detecting poor link quality leads to base station305to continue to send data transmissions to mobile station301without mobile station301actually receiving them, thus wasting valuable network resources and degrading the user's experience.

FIG. 6illustrates communication control system600. Communication control system600may be an example of one or more components of network access node105, base stations305&306, and ASN-Gateway307, although these devices may use alternative configurations. Communication control system600comprises communication interface601, user interface602, and processing system603. Processing system603is linked to communication interface601and user interface602. Processing system603includes storage system604that stores software605.

Communication interface601comprises components that communicate over communication links, such as network cards, ports, RF transceivers, processing circuitry and software, or some other communication devices. Communication interface601may be configured to communicate over metallic, wireless, or optical links. Communication interface601may be configured to use TDM, IP, Ethernet, optical networking, wireless protocols, communication signaling, or some other communication format—including combinations thereof.

User interface602comprises components that interact with a user. User interface602may include a keyboard, display screen, mouse, touch pad, or some other user input/output apparatus. User interface602may be omitted in some examples.

Processing system603may comprise a microprocessor and other circuitry that retrieves and executes software605from storage system604. Storage system604may comprise a disk drive, flash drive, data storage circuitry, or some other memory apparatus. Software605comprises computer programs, firmware, or some other form of machine-readable processing instructions. Software605may include an operating system, utilities, drivers, network interfaces, applications, or some other type of software. When executed by processing system603, software605directs processing system603to operate communication control system600as described with respect toFIGS. 1-5.