HK1063119B - Method and apparatus for data rate control in a communication system - Google Patents

Description

Method and apparatus for data rate control in a communication system

Background

Technical Field

The present invention relates generally to communications, and more particularly to a method and apparatus for data rate control in a communication system.

Technical Field

The increasing demand for wireless data transmission and the expansion of services provided through wireless communication technologies has led to the development of specific data services. One such service is known as High Data Rate (HDR). An exemplary HDR service IS proposed by the EIA/TIA-IS856 cdma2000 high Rate packet data air interface Specification, referred to as the HDR Specification for short.

HDR services are generally the coverage of voice communication systems that provide a means for efficiently transmitting packet data within a wireless communication system. As the amount of data sent and the number of transmissions increases, the limited bandwidth available for wireless transmission becomes a critical resource. Therefore, there is a need for an efficient and accurate method of transmitting information in a communication system to optimize the use of available bandwidth.

Summary of The Invention

According to one aspect of the invention, a wireless device operating within a wireless data communication system includes a processor and a memory. The memory is coupled to the processor. The processor operates on a plurality of computer readable instructions. These instructions include: a first set of computer readable instructions for determining whether there are enough available time slots to transmit a data packet before the interrupt; and a second set of computer readable instructions for generating an interrupt indication to prevent transmission of the data packet when there are insufficient time slots to receive the data packet.

In accordance with another aspect of the present invention, in a wireless communication system capable of data communication, a method determines a data service interruption and transmits a data interruption indication to prevent data transmission during the interruption.

Brief description of the drawings

FIG. 1 is a communication system according to an embodiment;

fig. 2 is a state diagram of the operation of an access network within the communication system shown in fig. 1 according to one embodiment;

fig. 3 is a state diagram of the operation of an access terminal within the communication system shown in fig. 1 according to one embodiment;

fig. 4 is a timing diagram illustrating data rate control timing within the communication system shown in fig. 1 according to one embodiment;

fig. 5 is a timing diagram illustrating data rate control generation and corresponding data transmission within the communication system shown in fig. 1, according to one embodiment;

6-7 are additional timing illustrations of data rate control generation and corresponding data transmission within the communication system shown in FIG. 1, according to one embodiment;

fig. 8 is a flow diagram of data rate control for the communication system shown in fig. 1, according to one embodiment.

Detailed description of the invention

Fig. 1 illustrates AN architectural reference model of a communication system 10 with AN Access Network (AN)12 in communication with AN Access Terminal (AT)16 over AN air interface 14. In one embodiment, system 10 IS a Code Division Multiple Access (CDMA) system having a High Data Rate (HDR) overlay system, such as that specified in the EIA/TIA-IS856 CDMA2000 high rate packet data air interface Specification, referred to as the "HDR Specification". The AN 12 communicates with AN AT16 and other ATs (not shown) within the system 10 over AN air interface 14. The AN 12 includes a plurality of sectors, wherein each sector provides at least one channel. A channel is defined as a set of links for communication between the AN 12 and the AT a given frequency assignment. The channels include a Forward Link (FL) to enable transmission from the AN 12 to the AT16 and a Reverse Link (RL) to enable transmission from the AT16 to the AN 12.

Fig. 2 and 3 illustrate the corresponding HDR operation of the AN 12 and the AT 16. In addition to the signal processing module, the AN 12 and the AT16 each include a processor and AT least one memory storage device. The processor may be a central processing unit or a dedicated controller. The memory storage device stores computer readable instructions and/or programs that control communications within wireless system 10. Within the AN 12, a memory storage device may store instructions that control the transfer of data. Within the AT16, the memory storage device may store instructions that control the transfer of data, including data requests.

Fig. 2 illustrates a state diagram 40 of data transmission states, i.e., HDR states, for the AN 12 of the AT 16. In general, the state of the AN 12 refers to the state of the protocol engines within the AN 12, as it applies to a particular AT, such as the AT 16. Since the AN 12 communicates with multiple ATs, there are multiple independent protocol instances within the AN 12, each with its own independent state machine. The state diagram 40 includes two states: ENABLE and DISABLE (DISABLE), where each state refers to data transfer to the AN 12. In the enabled state 42, the AN 12 is configured to receive a request for a data transmission from the AT16 for sending any pending data transmission to the AT 16. In the deactivated state 43, the AN 12 interrupts transmission of pending data transmissions to the AT 16.

For data transmission, the AN 12 receives a data request from the AT 16. The data request specifies the data rate at which data is to be transmitted, the length of the data packet to be transmitted, and the sector from which the data is to be transmitted. The AT16 determines the data rate based on the channel quality between the AN 12 and the AT 16. In an embodiment, the quality of the channel is determined by the carrier-to-interference ratio C/I. Another embodiment may use other metrics corresponding to channel quality. The AT16 provides a request for data transmission by sending a data rate control, DRC, message over a particular channel called DRC. The DRC message includes a data rate portion and a sector portion. The data rate portion indicates a requested data rate at which the AN 12 is transmitting data and the sector indicates from which sector the AN 12 is transmitting data. To handle data transmission, both data rate and sector message are required. The data rate part is called DRC value and the sector part is called DRC cover. The DRC value is a message sent to the AN 12 over the air interface 14. In one embodiment, each DRC value corresponds to a data rate of kbits/sec of the associated packet length with a predetermined DRC value assignment. The value assignment includes a DRC value of instruction zero data. In effect, a zero data rate indicates to the AN 12 that the AT16 is unable to receive data. For example, one situation is that the channel quality is not good enough for the AT16 to receive the data accurately.

In operation, the AT16 continuously monitors the quality of the channel to calculate the data rate AT which the AT16 can receive the next data packet transmission. The AT16 then generates a corresponding DRC value; the DRC value is sent to the AN 12 to request data transmission. Note that typically data transmissions are divided into packets. The time required to transmit a data packet is a function of the data rate of the application.

In an embodiment, the AT16 covers the DRC value with a DRC cover. The DRC value is a code applied to identify the sector from which data is transmitted. In one embodiment, the DRC cover is a Walsh code applied to the DRC value, where a unique code corresponds to each sector in the AT16 active set. The active set AS, includes the sectors with which the AT16 is currently transmitting and receiving information. According to this embodiment, at least one Walsh code is designated AS not corresponding to zero coverage for any sector within the AS. Since the DRC value specifies the data rate and the DRC cover identifies the transmission sector, the DRC value and DRC cover provide a complete data request. Still other embodiments may include a sector identification within the DRC value.

Continuing with fig. 2, the AN 12 transitions from the enabled state 42 to the disabled state 43 upon receiving a DRC value corresponding to a zero data rate or a DRC value with zero coverage. Upon transitioning to the deactivated state 43, the AN 12 does not process any pending data transmissions to the AT 16. From the deactivated state 43, the AN 12 transitions to the enabled state 42 upon receiving a DRC value indicating a data rate other than zero, i.e., a valid non-zero data rate. Similarly, the AN 12 transitions to the enabled state upon receiving a DRC value specifying the DRC cover for the active sector, i.e., the sector within the AT16 active set. In the enabled state 42, the AN 12 handles data transmission to the AT16 in a wait state. Specifically, the AN 12 processes the next data transmission according to the data rate specified in the DRC value and the sector specified by the DRC cover.

Fig. 3 illustrates a state diagram 41 of the operation of the AT16 indicating a transition between an enabled state 44 and a disabled state 45. In the enabled state 44, the AT16 requests data from the AN 12 and processes data transmissions from the AN 12. In the deactivated state 46, the AT16 does not request data from the AN 12. The AT16 enters the deactivated state 46 when there are not enough available slots for a given data transmission or message. The determination of the number of available slots, i.e., the amount of time allowed for data transmission, is a function of several conditions, including the DRC start time, the DRC length, the DRC value indicating the transmission, and the turnaround time. The time available to the AT16 to receive the data transmission is from the DRC start timeThe measurement of the elapsed DRC length and the turnaround time is started. For example, referring to FIG. 5, DRC Start time is at time t₀To (3).

As shown in fig. 5, the available time for the AT16 to receive a data transmission is AT time t₁₀At any time, and may in fact be from time t₀To t₁₀And (6) measuring. As illustrated, the DRC may be many slots long. This example DRC (i) consists of four slots, where the DRC length is from time t₀Measure t₄And comprises four time slots: t is t₀To t₁、t₁To t₂、t₂To t₃And t₃To t₄. The turn-around time being from time t₄To t₅. After the turnaround time, there are four available time slots in which data transmission can begin. Since the length of the DRC window is equal to the DRC length, the DRC window includes the same number of slots as the DRC being transmitted. In other words, the DRC length is equal to the DRC window length. In particular, as shown in fig. 5, the length of drc (i) is equal to the length of the drc (i) window. The available time, in addition to the DRC start time, DRC length and turn around time, is calculated from the latest time that the transmission may be completed. Data transmission may begin in any of the four slots of the drc (i) window, with the latest possible transmission completion beginning at t₈Is completed at t₁₀. Thus, the latest possible transmission is used to calculate the available time. Note that it is possible to process transmissions from each slot of the DRC window, for a total of four possible transmissions in this example. However, none of the four transmissions will be more than at time t₈Late completion of start.

Returning to fig. 3, in effect, in the deactivated state 46, the AT16 does not request any further HDR transmissions. The AT16 transitions to the deactivated state to "tune away" to another frequency, and thus, the data transmission frequency is not available for reception. The AT16 may be processing the requested data before transitioning to the deactivated state. Similarly, the AT16 may store the received data in a memory device for later processing. It is also possible to store some data for later processing while other data is being processed. When the AT16 does not request data transmission and is in the deactivated state 46, the AT16 may continue to process received data and may receive messages within the available time before transitioning to the deactivated state 46. Thus, if any message in a wait state may complete transmission while the AT16 is modulating, the message may be transmitted from the AN 12 and received by the AT 16. In one embodiment, the AT16 may be in the deactivated state 46 to process voice transmissions.

Multi-carrier wireless communication systems, such as systems supporting voice and data, employ different carrier frequencies for different services and/or sectors. For example, in one embodiment, a wireless HDR system includes different frequencies per sector. Other systems include services using different carriers such as short message service, SMS, fax services, etc. In a multi-carrier system, the AN may need to search for different frequencies, either periodically or when AN event occurs. AT any time the AT searches for a different frequency, the AT tunes to the different frequency. In an HDR system, the AT may tune to search for other sectors.

In operation, the AT16 determines a data rate based on the quality of the channel. Based on the data rate, the AT16 can calculate the time required to transmit the next data packet. Time is measured as time slots, where each time slot is a predetermined period of time. In an HDR system, the AT16 may receive both voice and data communications. To accomplish this, the AT16 switches between the data and voice portions of the system. When the AT16 switches to the voice portion of the system, the data portion is temporarily interrupted AT the AT 16. In particular, the AT16 periodically monitors the paging channel for requests for voice communications.

In addition to handling data transmissions from the AN 12, the AT16 also handles voice transmissions. The voice transmission may be received from AN 12 or another AN within system 10. To handle voice transmissions, the AT16 periodically checks for voice system pages indicating that a voice call is waiting. Note that the voice system may include other services, such as SMS and may implement an inter-frequency search. HDR and voice transmissions are processed separately in different frequency domains. To locate a page, the AT16 monitors a particular frequency other than the HDR frequency. The result of checking for paging results in a substantial interruption in the HDR frequency. To avoid losing any data packets that may be transmitted during the interruption, the AT16 determines the schedule for each interruption. If a given data transmission can be completed before a scheduled interruption, the AT16 sends a request to the AN 12 in the form of a DRC with AN effective data rate and AN effective sector. In other words, the AT16 compares the number of time slots N required to transmit or receive a given data transmission or data packet with the number of time slots M prior to the scheduled interrupt. If N is less than or equal to M, data transmission may occur. If there is insufficient time to handle the data transmission before the scheduled interruption, i.e., N is greater than M, the AT16 provides instructions indicating to the AN 12 not to send the next data transmission. In an embodiment, the message is a DRC with either a zero data rate or a zero cover.

As shown in fig. 3, upon determining that no time slot is available for the next data transmission, the AT16 transitions from the enabled state 44 to the disabled state 46. In the deactivated state 46, the AT16 discontinues requesting data transmission from the AN 12. Upon determining that the next data transmission has sufficient time slots, the AT16 transitions from the deactivated state 46 to the enabled state 44. In the enabled state 44, the AT16 sends a DRC with AN effective data rate and sector to the AN 12 and processes the data transmission received from the AN 12.

In one embodiment, the DRC is provided over multiple slots, as shown in fig. 4. The time slots are labeled A, B, C and D and correspond at time t₀、t₁、t₂And t₃And begins. The DRC value may use multiple slots and may include repetition coding techniques. The AT16 transmits DRC information in a particular slot on the RL. The DRC value is determined and continuously generated by the AT 16.

After a predetermined turnaround time, the AN 12 receives the DRC information and prepares to transmit data at the specified data rate and in the specified sector. As shown in FIG. 5, the DRC window begins t after the turn-around time₅. In one embodiment, the turnaround time is half of a time slot. The data transmission specified by DRC (i) may be within the DRC (i) window, i.e., t₅To t₈At any time.

FIG. 6 illustrates a first case where no sufficiently available time slot is available to handle the next data transmissionAnd (4) environmental conditions. To avoid losing any transmitted data packets AT the time of the interrupt, the AT16 determines when to schedule the next interrupt. From t is required to handle a given data transmission₆To t₁₀The time slot of (2). However, the AT16 is AT time t₁₀Marked with t in front_SWITCHIs scheduled with an interrupt. Since there are insufficient time slots available for the next data transmission, the AT16 provides AN indication to the AN 12 that no data should be sent during the upcoming interruption phase. In one embodiment, the indication is to provide a zero cover for the DRC. In effect, zero coverage provides a data rate request that does not specify a sector. The AN 12 receives zero coverage and does not have enough information to provide data, so no data is sent during this time period. In another embodiment, the indication is a zero rate request. Again, the AN 12 does not have sufficient information to provide data and therefore relinquishes transmission for that period of time.

Fig. 7 illustrates a second scenario in which the data transmission specified by drc (i) does not have enough slots to be received by AT 16. Data transmission at t_SWITCHLater time t₁₀And (4) finishing. The AT16 continues to generate DRC messages by determining the data rate as a function of the channel. The next calculation results in DRC (i +1) having a higher data rate than DRC (i). Based on the newly calculated data rate, the data transmission specified by the DRC (i +1) has sufficient slots to be received by the AT16, i.e., time t₁₂To t₁₃. In this case, the AT16 transmits DRC (i) with zero data rate or zero cover and the AN 12 has no data transmission start between DRC (i) windows, t₅To t₈. However, 0, the AT16 sends a DRC (i +1) with an effective data rate and an effective sector. In response, AN 12 may transmit data specified by DRC (i + 1). In this case, the channel conditions change sufficiently to increase the available data rate and reduce the transmission time required for the AT16 to receive the data transmission.

The AT16 continuously determines the data rate AT which data transmissions are received. The time required to process the data transmission at this data rate is determined and compared to the time available before the next interrupt. If there is time to receive a data transmission, the data rate is converted to a corresponding DRC value. Fig. 8 illustrates a process 50 for generating DRC information in anticipation of an interrupt, according to an embodiment. AT step 52, the AT16 calculates a data rate AT which a given data transmission is received. Based on the data rate, the AT16 calculates the number of slots N required to receive the transmission AT the data rate calculated AT step 52. The AT also calculates the number of slots M before the next interrupt AT step 54. N and M are compared at decision diamond 56. If N is less than or equal to M, i.e., the next transmission consists of sufficient available slots, the process proceeds to step 60 to determine the DRC value corresponding to the calculated data rate. The DRC value is sent at step 62 to identify the data rate and sector. Processing continues to step 66 to process the interrupt. If there are not enough slots available at decision diamond 58, processing continues to step 64 to transmit a DRC value with a zero data rate or zero cover. AT decision diamond 68, the AT16 determines whether to continue data transmission or to abort HDR processing. For example, the AT16 may receive a voice call and suspend data transmission until the call is completed. If the data transmission is to continue, the process returns to step 52 to determine the next data rate. If no call is received, HDR processing continues.

The method of fig. 8 may be applied in a wireless communication system capable of data communication, wherein an access terminal first determines a data service interruption and then sends a data interruption flag to prevent data transmission during the interruption. In fact, the access terminal does not request any data transmission that could not be completed before the interruption. The access interruption continues to provide DRC requests to the access network, wherein if there is no time available for a received data transmission, the corresponding DRC specifies a zero data rate or a zero sector. In response, the access network does not send data to the access terminal that could not be completed before the interruption.

Thus a novel and improved rate control has been described. Those of skill in the art would understand that the data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description are advantageously represented by voltages, circuits, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Those of skill would further appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The skilled person will recognize the interactivity of the hardware and software in these cases and how best to implement the described functionality for each particular application. By way of example, various illustrative logical blocks, modules, and algorithm steps may be implemented or performed in the following: a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components such as registers and FIFO, a processor executing a set of firmware instructions, any conventional programmable software module and a processor, or any combination of devices designed to perform the functions described herein. The processor is preferably a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary processor is preferably coupled to the memory to enable reading and writing of information from and to the storage medium. The processor and the storage medium may reside in an application specific integrated circuit, ASIC. The ASIC may reside in a telephone or other terminal. In addition, the processor and the storage medium may reside in a telephone or other terminal. A processor may be implemented as a combination of a DSP and a microprocessor, or as two microprocessors in conjunction with a DSP core, etc.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (18)

1. A mobile wireless device for use in a wireless data communication system, comprising:

a processor; and

a memory coupled to the processor, wherein the processor is configured to:

determining whether there are sufficient time slots to receive a data packet prior to the interruption; and generating an interrupt flag to disable transmission of the data packet if sufficient time slots are not available, wherein the interrupt flag is transmitted from the mobile wireless device via a reverse link.

2. The apparatus of claim 1, wherein the outage flag indicates data rate control zero coverage.

3. The apparatus of claim 1, wherein the outage flag indicates data rate control with a zero data rate.

4. The apparatus of claim 1, wherein the interrupt flag is associated with an expected interruption of data services within the apparatus.

5. The apparatus of claim 4, wherein the expected interruption originates from paging monitoring.

6. The apparatus of claim 4, wherein the expected interruption is due to a frequency search.

7. In a wireless communication system capable of data communications, a method comprising:

determining a data traffic disruption for a mobile wireless device operating in a wireless data communication system; and

transmitting a data outage indication to prevent data transmission from the access point during the data traffic outage.

8. The method of claim 7, wherein the data traffic disruption is due to a frequency search.

9. The method of claim 7, wherein the data outage flag is a data rate control message.

10. The method of claim 9, wherein the data rate control message indicates a zero data rate.

11. The method of claim 9, wherein the data rate control message indicates a zero sector.

12. The method of claim 7, wherein the step of determining comprises:

determining a time of the data service interruption.

13. The method of claim 12, further comprising:

a first time period to receive the data transmission is determined.

14. The method of claim 7, further comprising:

determining a first data rate at which to receive a next data transmission;

determining a first time slot number N required by the next data transmission;

determining a second time slot number M before the data service is interrupted;

if N is greater than M, sending a data rate request requesting the next data transmission at the first data rate; and

if N is not greater than M, a data rate request is sent requesting the next data transmission at a zero data rate.

15. The method of claim 14, further comprising:

processing the data traffic interruption after sending the data rate request.

16. A wireless device operable in a multi-carrier wireless communication system, comprising:

time calculation means for determining a data outage of the wireless device for a carrier; and

interrupt indication means for generating an interrupt flag to prevent transmission of data on said carrier during said data interrupt.

17. The wireless apparatus of claim 16, further comprising:

data computing means for determining whether a next data transfer will be completed before the data interrupt.

18. A mobile wireless communications device adapted for wireless data communications, comprising:

means for determining that the mobile wireless communications device data service is disrupted; and

means for transmitting a data interrupt flag from said mobile wireless device for preventing data transmission when there are not enough time slots to receive a data packet prior to the interrupt.