HK1088136B - System and method for fluid power control of a reverse link communication - Google Patents

Description

System and method for flow power control for reverse link communications

Claiming priority in accordance with 35U.S.C. § 119

This application is a non-provisional application claiming priority from provisional application serial No. 60/461,756 filed on 11/4/2003 entitled "System and Method for fluid Power Control of a Reverse Link Communication".

Technical Field

The present invention relates generally to the field of telecommunications, and more particularly to a system and method for improving the performance of data transmission in a wireless telecommunications system.

Background

In a typical wireless voice/data communication system, base stations are associated with coverage areas. This area is called a sector. Mobile stations within a sector can transmit data to and receive data from a base station. Particularly in the case of data communication, a base station may be referred to as an access network (also referred to as an access point), and a mobile station may also be referred to as an access terminal. An access terminal may be able to communicate with more than one access network simultaneously, and as the access terminal moves, the set of access networks with which it communicates may change.

The communication parameters between a particular access network and a particular access terminal are based in part on their relative locations and the quality and strength of the signals that they respectively transmit and receive. For example, as an access terminal moves away from an access network, the strength of the signal received by the access terminal from the access network decreases. Therefore, the error rate of the received data will increase. Thus, the access network can typically compensate for the increased distance by reducing the rate at which it transmits data to the access terminal. This allows the access terminal to receive and decode the access network's signal with fewer errors. As the access terminal approaches the mobile network, the signal strength increases, thus enabling the use of higher data rates to transmit data to the access terminal.

Similarly, when the access terminal is far from the access network, the strength of the signal received by the access network from the access terminal may decrease, thereby possibly resulting in a higher error rate. Similar to the access network, the access terminal may typically compensate for the increased distance by decreasing its data rate to allow the access network to receive the signal with fewer errors. The access terminal may also increase its power output to reduce the error rate if requested by the access network. On the other hand, when the access terminal is close to the access network, a stronger signal may support a higher data rate.

In one system, an access terminal is responsible for determining the rate at which data may be transmitted from the access terminal to the access network. The rate is determined based on several factors. The primary factors are the absolute maximum rate at which the access terminal and access network are able to communicate, which is based on the allowable power output of the access terminal, the amount of data in the access terminal queue adjusts the maximum rate, and the allowable maximum rate is based on a ramp-up constraint. In this system, each of these rates represents some hard limit that the selected data rate cannot exceed. That is, the selected data rate cannot be higher than the minimum of the four rates.

The first two of these rates (absolute and power-limited maximum rates) arise from the physical constraints of the system and are outside the control of the access terminal. The third and fourth rates (ramp-up-limited) are variable and are dynamically determined based on specified prevailing conditions of the access terminal.

The data-justified rate is basically the maximum rate that can be justified by the amount of data that the access terminal queues for transmission. For example, if the access terminal has 1000 bits in its transmit queue, the data rate of 38.4kbps is adjusted, but the higher rate of 76.8(2048 bits/frame) may not be adjusted. A time frame may be defined as a unit of time, such as in CDMA2000 defined by the IS-856 standard^TMIn a 1xEV-DO system, one time frame is 26.666 ms. If there is no data in the access terminal's transmission queue, then it is determined that there is no transmission rate at all.

The rate of rise limiting is the maximum rate allowed, taking into account the fact that a rapid rise may suddenly increase the interference perceived by other access terminals and may degrade their performance. If the rise of each access terminal is limited, the interference level it causes may change slower, and other access terminals can more easily adjust their operating data rates and transmit powers to accommodate the increased interference. It should be noted that the rate of the rise-limiting is also calculated to control the falling (ramp-down) data rate. The overall effect is to minimize wide and/or fast fluctuations in data rates and thereby stabilize the overall operation of the access network and the access terminals in the system.

Although the rate of change of the rise limit (with respect to increasing and decreasing the data rate) is controlled, the rate of data adjustment is not controlled. If the access terminal suddenly has enough data to adjust to a high rate, the rate of data adjustment may suddenly increase. If the access terminal runs out of data, the rate of data adjustment may suddenly drop to zero. Sudden increases in the rate of data adjustment are typically not a problem since the rate of rise limiting is controlled. Since the minimum of the four rates mentioned above dictates the maximum rate of the selected data rate, the rate of the rise limit can be controlled in this case. However, since the data-justified rate is lower than the other rates and thus controllable, a sudden decrease in the data-justified rate may result in a decrease in the actual data rate (note that the data rate selected for data transmission on the next frame is the smallest of the four rates).

In prior art systems, if the access terminal has no data to transmit, no data is transmitted. This is certainly intuitive and conventional knowledge indicates that useful bandwidth should not be wasted by transmitting useless data. One of the problems caused by allowing the data rate to drop rapidly (e.g., to zero) is that it takes some time for the data rate to gradually ramp back up. Delays in the transmission of certain data may be caused by a drop in the data rate and a subsequent rise. This delay may be particularly caused where the data is bursty or has discrete arrival processes. One such type of data is real-time video, which may include 500 to 1000 byte packets that arrive at the transmit queue at discrete intervals of 60 to 70 milliseconds. Real-time video is also a notable example of such data, the transmission delay of which is particularly noticeable and therefore unacceptable. Network gaming is another class of applications where data arrival is sporadic and data latency (latency) is a key performance metric. Therefore, there is a need for a method and apparatus for properly determining a data rate for a rapid rise in the data rate while minimizing undesirable effects in a communication system.

Disclosure of Invention

A state variable called a stream (fluid) power level is defined for each access terminal. The stream power level is a continuous power level that takes into account a target power level for sector loading (loading). The actual transmission is done at discrete power levels allowed by the physical layer, but by dithering (between these discrete levels) the average power level can be made equal to the stream power level. Thus, the current transmission state of each access terminal is typically represented by a continuous variable, rather than at a discrete rate as is typical. This allows the average transmit power to be smoothly changed as the access terminal increases its power to take advantage of underutilized system capacity. As a result, the access terminal increases power using a simple deterministic power ramp-up value rather than using random discrete hops, which reduces performance variation and improves controllability of the system.

In one aspect, a method for determining a data rate for reverse link communications of an access terminal includes receiving reverse activity bits, transmitting the reverse activity bits to a digital filter to produce filtered reverse activity bits, determining a continuous stream power level based on the filtered reverse activity bits, and determining the data rate based on the continuous stream power level.

Drawings

Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings.

Fig. 1 illustrates a portion of a wireless communication system capable of operating in accordance with an embodiment;

fig. 2 illustrates in more detail an access network and an access terminal in two adjacent sectors of a wireless communication system capable of operating in accordance with an embodiment;

fig. 3 is a functional block diagram illustrating the structure of an access terminal capable of operating in accordance with an embodiment;

FIG. 4 is a flow diagram illustrating determining a data rate for a reverse link according to an embodiment;

FIG. 5 illustrates a concept of token buckets (token buckets) according to an embodiment;

fig. 6 is a block diagram of fast Reverse Activity Bit (QRAB) and Filtered Reverse Activity Bit (FRAB) generation, according to an embodiment.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular embodiment which is described. The disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the following appended claims.

Detailed Description

In general, the present invention comprises a system and method for improving data transmission performance in a wireless telecommunication system by controlling increases and decreases in the data transmission rate of the reverse link.

Referring to fig. 1, a portion of a wireless communication system is shown in accordance with an embodiment. In this embodiment, the system includes a plurality of Access Networks (ANs) 12 and a plurality of Access Terminals (ATs) 14. Each access network 12 communicates with access terminals 14 in its vicinity. An access terminal may move within a sector or may move from a sector associated with one access network to a different sector associated with another access network. The coverage area is a sector 16. Although the sectors may in fact be somewhat irregular and may overlap with other sectors, they are depicted in the figure as generally depicted by dashed lines. It should be noted that for simplicity, only one access network, one access terminal, and one sector are identified by reference numbers.

Referring to fig. 2, an access network and an access terminal in two adjacent sectors of a wireless communication system are shown in more detail, according to an embodiment. In the system, sector 20 includes an access network 22 and several access terminals 24A-24C. Sector 30 includes an access network 32 and a single access terminal 34. Access networks 22 and 32 transmit data to access terminals 24 and 34 over what is referred to herein as a Forward Link (FL). Access terminals 24A-24C and 34 transmit data back to access networks 22 and 32 via what is referred to herein as a Reverse Link (RL).

In a Code Division Multiple Access (CDMA) System conforming to the "TIA/EIA/IS-95 Mobile Station-Base Station compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System" (IS-95), data packets can be retransmitted on the FL. The technique of FL transmission is described in U.S. Pat. No. 6,574,211 issued on 3.6.2003, entitled "Method and Apparatus for High Rate packet Data Transmission". For example, the data packet can include a predetermined number of data units, each identified by a sequence number. When a mobile station incorrectly receives one or more data units, the mobile station may send a Negative Acknowledgement (NACK) on the RL ACK channel to indicate the sequence number of the missing data unit for retransmission from the base station. The base station receives the NACK message and is able to retransmit the erroneously received data unit.

Automatic repeat request (ARQ) refers to a protocol in which a receiver requests a transmitter to retransmit data. When the first half of the frame is successfully decoded, the AN can send AN acknowledgement message (ACK) to the AT to indicate that the AN has successfully decoded the data received in the first half of the frame. When the first half of the frame is not successfully decoded, the AN can send a Negative Acknowledgement (NAK) message to the AT to indicate that the AN was not successfully decoding the data received in the first half of the frame. Techniques for RL ARQ are described in U.S. patent publication No.2004-0081124, 10/280,740, filed 24.10.2002, entitled "Reverse Link Automatic Repeat Request" and assigned to the assignee of the present invention.

An ACK is a message transmitted to indicate that some data has been correctly received. Typically, if the sender (sender) does not receive an ACK message after a certain predetermined time has elapsed, or receives a NAK, the initial data will be sent again.

A NAK is a message transmitted to indicate that some data was received incorrectly, e.g., the data may have a checksum (checksum) error. An alternative to sending a NAK is to use only an ACK message, in which case no ACK is received after a certain time period is considered a NAK. As used herein, NAK refers to the receipt of a NAK message or the lack of receipt of an ACK.

The transmission unit of the physical layer of the 1x-EVDO is a physical layer packet. The data is included in a physical layer packet. In an embodiment, the physical layer is grouped and included in frames on the reverse link. In an embodiment, the duration of a frame may be 26.66 milliseconds (ms). In an embodiment, a frame may include 16 slots, each slot having a duration of 1.66 ms. In an embodiment, a frame may include 12 slots. It will be apparent to those skilled in the art that the frames may have different durations. It will be readily apparent to those skilled in the art that a frame can include any number of time slots.

In an embodiment, the physical layer packet is included in a subframe. In an embodiment, four slots constitute one subframe. In an embodiment, the physical layer allows interleaved (interleaved) data packets. Thus, for example, a first data packet may be transmitted in a first subframe, a second data packet in a second subframe, a third data packet in a third subframe, and the first data packet in a fourth subframe if an ACK has not been received at the time of the first transmission of the first data packet. It will be apparent to those skilled in the art that a frame may include any number of subframes. A frame may also be referred to as an interlace.

Referring to fig. 3, a functional block diagram illustrating the structure of an access terminal according to an embodiment is shown. In this embodiment, the access terminal includes a processor 42 coupled to a transmit subsystem 44 and a receive subsystem 46. The transmit subsystem 44 and receive subsystem 46 are coupled to a shared antenna 48. Processor 42 receives data from receive subsystem 46, processes the data, and outputs the processed data via output device 50. The processor 42 also receives data from a data source 52 and processes the data for transmission. The processed data is then forwarded over the reverse link to transmit subsystem 44 for transmission. In addition to processing data from receive subsystem 46 and data source 52, processor 42 is configured to control various subsystems of the access terminal. In particular, processor 42 controls transmit subsystem 44. The access terminal-based functionality described below is implemented in the processor 42. A memory 54 is coupled to the processor 42 for storing data used by the processor.

In one embodiment, the system is CDMA2000^TM1xEV-DO system. The main characteristics of such a system are defined by the well-known IS-856 data communication standard. The designation "1 xEV-DO" relates to the CDMA2000 family (family) ("1 x") and the evolution of standards for data optimized ("DO") operations. The 1xEV-DO system is optimized primarily for wireless internet access for which higher data throughput on the forward link is desired.

The 1xEV-DO system is designed to transmit data on the forward link at one of 12 different predetermined data rates, the 12 data rates ranging from 38.4kbps to 2.4Mbps (plus zero rate). A corresponding data packet structure (specifying such payment as packet duration, modulation type, etc.) is defined for each of these predetermined data rates. In an embodiment, communication on the reverse link occurs at one of five different data rates, ranging from 9.6kbps to 153.6kbps (plus a zero rate). On the other hand, a data packet structure is defined for each of these data rates. In other embodiments, it will be apparent to those skilled in the art that the reverse link can support any number of data rates.

The present invention relates generally to the reverse link. The data rate of the reverse link in one embodiment is set forth in table 1 below.

TABLE 1

Rate indexing	Data rate Kbps	Data rate bits/frame
			0	0	0
1	9.6	256
			2	19.2	512
3	38.4	1024
			4	76.8	2048
5	153.6	4096

In another embodiment, there may be more or less data rates, as would be apparent to one skilled in the art. For example, in table 2 shown later, there are more data rates than those shown in table 1. Table 2 shows data rates on the reverse link for another embodiment.

As described above, current 1xEV-DO based systems are built in accordance with CDMA standards. The data transmitted on the reverse link is thus code division multiplexed. That is, the data corresponding to each access terminal is identified by a respective code. Each code defines a communication channel. Thus, data from any or all access terminals can be transmitted simultaneously, and the access network can utilize the code to distinguish between different data sources.

Code Division Multiple Access (CDMA) transmissions are interference limited. That is, the amount of data that can be transmitted is limited by the amount of interference present in the environment. The main source of interference for an access terminal's transmission is other access terminals in the region, although there is some amount of interference caused by background noise or thermal noise. If there are several other access terminals and they transmit little data, there is little interference and it is therefore possible to transmit data at a higher data rate. On the other hand, if there are many other access terminals transmitting large amounts of data, the interference level will be high and only very low data rates may be used for reverse link transmissions.

Therefore, a mechanism must be provided to determine the appropriate data rate for each of the access terminals. A typical CDMA wireless communication system uses a small set of data rates for all access terminals. A set of two possible data rates IS typical in systems operating in accordance with the IS-95 standard. Some CDMA communication systems that provide for voice and data communications use some form of centralized control whereby the information needed to allocate the rates is centralized at a central location and then the rate allocations are communicated back to each access terminal. The difficulty of centralized control lies in: 1) the optimal rate calculation for all access terminals can be difficult and computationally intensive, 2) the communication cost for control signaling to and from the access terminals is prohibitive, and 3) the effectiveness of the "optimal" rate allocation is questionable once the latency and uncertainty about the network's future needs and its behavior are considered.

One aspect of the present system that differs from typical systems is that the calculation of the data rate of an access terminal is the responsibility of each individual access terminal. That is, it is distributed rather than centralized. The access terminals themselves utilize a reverse link Mac algorithm to determine the appropriate data rate for a particular access terminal ("Mac" is an industry term for multiple access communications). The reverse link Mac algorithm is discussed additionally.

When a particular access terminal calculates the data rate of its reverse link, it obviously wants to select the highest possible rate. However, there are other access terminals in the sector. These other access terminals also attempt to transmit their data at the highest possible rate. Since the power required to transmit data is roughly proportional to the data rate, increasing the data rate of each access terminal will increase its transmission power. The transmission of each access terminal will thus result in an increased amount of interference to other access terminals. To some extent, so much interference will occur that no access terminal is able to transmit its data with an acceptable error rate.

It is therefore advantageous for an access terminal to have information regarding the level of interference present in the system. If the interference level is relatively low, the access terminal can increase its data rate to some extent without significantly adversely affecting the overall performance of the system. However, if the interference level is too high, an increase in the data rate of the access terminal may have a significant adverse effect.

Thus, in one embodiment, the access network tracks the total interference level. The access network is configured to simply confirm whether the total interference level is above or below a threshold. If the interference level is below a threshold, which indicates a lower level of activity, the access network sets the Reverse Activity Bit (RAB) to-1. It will be apparent to those skilled in the art that another value may be used to indicate a lower activation level. For example, a zero value can be used to indicate a lower activation level. The RAB is sometimes also referred to as a busy bit. If the interference level is above the threshold, which indicates a higher activation level, the access network sets the RAB to 1. It will be apparent to those skilled in the art that another value may be used to indicate a higher activation level. The RAB is thus communicated to each of the access terminals to inform them of the activation/interference level in the system.

In one embodiment, the total interference level is calculated by summing the power of each access terminal's reverse link transmission and dividing by the thermal or background noise level in the environment. The quotient is then compared to a threshold. If the quotient is greater than the threshold, the interference level is considered high and the RAB is set to 1. If the quotient is less than the threshold, the interference level is considered low and the RAB is set to-1.

Since the performance of reverse link data communications depends on the interference level and the data rate in the system, the interference level must be considered in calculating the appropriate data rate. Thus, in accordance with various aspects of the invention, the data rate calculation in the reverse link Mac algorithm takes into account the interference level as if provided to the access terminal in the form of a RAB. The reverse link Mac algorithm also takes into account factors such as the requirements of the access terminal and the physical constraints of the system. Based on these factors, the data rate for each access terminal is calculated once per subframe.

A method and apparatus for determining a data rate for reverse link communications of an access terminal includes receiving a RAB from an access point in a communication system and passing the RAB to a digital filter to produce a filtered RAB.

In an embodiment, the RAB corresponds to a sector of the access network and is set at each time slot at the access network. The access terminal decodes the RAB at each slot. In an embodiment, RAB is passed to a RAB with a short time constant t_sTo generate fast reverse activation bits (QRAB). In an embodiment, the RAB is passed to a constant with a long time t_LTo generate Filtered Reverse Activation Bits (FRAB). The QRAB and FRAB are with respect to the RAB and a time constant. QRAB and FRAB provide an indication of system power loading. QRAB provides an indication of the short term loading of the system. FRAB provides an indication of long term loading of the system.

QRAB is based on the use of a short time constant t_sTo the filtered RAB. In the examples, t_sIs four time slots. In one embodiment, the QRAB is determined every time slot, but the access terminal uses the QRAB value when it occurs at the subframe boundary of the access terminal, which is every four time slots.

FRAB is a method of using a long time constant t_LTo the filtered RAB. In the examples, t_LIs 256 time slots. In an embodiment, FRABs are determined every 256 time slots.

It will be apparent to those skilled in the art that the time constant being filtered and the interval of use of the RAB values being filtered need not be the same. Thus, in other embodiments, the sampling rate of the filtered RAB values may be independent of the time constant being filtered.

In an embodiment, a reverse link data rate is determined based on the filtered RAB values. Also, a processor in the access terminal may determine whether the access terminal is in idle mode and communicate a non-busy state value of the RAB to the digital filter while the access terminal is in idle mode. This results in a short-term priority being given to newly idle access terminals, which may be expected to reduce the latency of low-rate burst sources.

In an embodiment, the reverse link data rate is determined based on a set of filters for the RAB.

Fig. 4 is a flow chart illustrating the reverse link Mac algorithm according to an embodiment with two filters for the RAB. The receiving subsystem 46 of fig. 3 receives the RAB. The processor 42 of fig. 3 executes the reverse link Mac algorithm.

The reverse link Mac algorithm is performed for each subframe n. The reverse link Mac algorithm is executed on the access terminal and enables the access terminal to derive a primary change rate based on the RABs broadcast by each sector in the active set (active set).

In step 402, QRAB_nIs set to the maximum QRAB of all sectors i in the active set, (i.e., max)_i(QRAB_n，i) QRAB), wherein QRAB_n，iIs a discrete quantity, QRAB_{n，i∈{-1，1}}。FRAB_nIs set to the maximum FRAB (max) of all sectors i_i(FRAB_n，i) Wherein, FRAB_n，iIs a continuous quantity, FRAB_{n，i∈{-1，1}}。C_nIs set to the highest priority non-empty queue, which represents the highest priority data class. The flow of control proceeds to step 404.

In step 404, a check is made to determine if QRAB is busy. If QRAB_nAnd is busy, the flow of control proceeds to step 406. In step 406, based on equation Δ Φ_n＝-f_d.cn(Φ_n，FRAB_n) To determine the power level increment delta phi_nWhich is a ramp value (rampingvalue). f. of_d，cnIs to couple the current traffic to the pilot (T2P) power level phi_nAnd long term sector loading FRAB_nAs a down function of its argument and is the highest priority data class C_nAs a function of (c). Phi_nIs a continuous state variable for the access terminal for the current T2P power level. Phi_nIs the current power resource allocation for each access terminal and is also referred to herein as the stream power.

If in step 404, QRAB_nIf not, flow of control proceeds to step 408. In step 408, a check is made to determine if the access terminal was not data or power limited in the last subframe, i.e., DatPowLim_n-1False. If the access terminal is not data or power limited, then the flow of control proceeds to step 410, otherwise the flow of control proceeds to step 412. An access terminal is data-limited if it does not have the data on the reverse link that is needed to transmit the rate assigned by the reverse link Mac algorithm.An access terminal is power limited if it does not have the power required to transmit the rate assigned by the reverse link Mac algorithm on the reverse link.

In step 410, QRAB is not busy, based on equation Δ Φ_n＝f_u，cn(Φ_n，FRAB_n) To determine the power level increment delta phi_n。f_u，cnIs to couple the current traffic to the pilot (T2P) power level phi_nAnd long term sector loading FRAB_nAs its argument, and is the highest priority data class C_nAs a function of (c).

In step 412, the power level variable Δ Φ_nIs set to zero. From steps 406, 410, and 412, the flow of control proceeds to step 414.

In step 414, the flow power Φ is updated based on the equation_n。

Φ_n＝max((1-1/τ_p)Φ_n-1+1/τ_pα_n-1+ΔΦ_n，Φ_min) Wherein, τ_pIs the time constant of the T2P level filter, alpha_n-1Is T2P transmitted for the last subframe, and Φ_minIs a minimum T2P for the access terminal. In the examples, τ_pIs 12 subframes. To be more accurate, α_n-1Is the actual discrete T2P for the last subframe. Term (1-1/τ)_p)Φ_n-1+1/τ_pα_n-1+ΔΦ_nIncluding having a ramp function Δ Φ_nAn Infinite Impulse Response (IIR) filter of the transmit power of (1). Alpha is also referred to as the transmitted T2P power level. From step 414, the flow of control proceeds to step 416.

The reverse link Mac algorithm uses token buckets to match the average of the transmit power to the flow power level Φ_n. Current power level phi_nIs continuous and the transmit power is discrete. The transmit power is limited to the actual discrete physical T2P level. Thus, to map between a stream power level and a discrete transmit power level,the token bucket is used to dither between physical power levels and adjust the transmitted data rate. The token bucket is input with a flow power phi_nAnd the allocated transmit power is subtracted.

Fig. 5 illustrates the concept of token bucket 502 according to an embodiment. The token bucket level (level)504 is denoted as β. The upper limit 506 of the token bucket level is beta_maxI.e., the maximum value of the token bucket level. Current power level phi_nIs added to the token bucket. Subtracting the transmit power α from the token bucket 504_n510。α_n510 is the T2P power allocation for subframe n, which achieves the corresponding data rate.

Block 512 in the token bucket represents T2P and the allocation of data to packets for transmission. I.e., at each new interlace assignment, the access terminal can decide how many bits to put into the packet and at what traffic-to-pilot ratio T2P to transmit the packet. The box indicates that these two quantities are selected and put together.

In step 416, based on equation β_n＝min(β_n-1+Φ_n，β_fact(Φ_n)Φ_n，β_max) To determine the token bucket level beta_n。β_n-1Is the token bucket level of the last subframe. Beta is a_maxIs the maximum size of the token bucket. Beta is a_fact(Φ_n) Representing the power of the flow phi_nA multiplier factor of (d). Beta is a_fact(Φ_n) Adjusting how much flow power Φ can be accumulated in the token bucket between allocations of transmit power_n. E.g. beta_fact(Φ_n) 2 means that the transmit power allocation may be at most twice the current stream power.

In an embodiment, the data is bursty at a higher Φ_sIs more limited, thus beta_fact(Φ_n) Is phi_nIs reduced. From step 416, control flows to step 418.

In step 418, a check is made to determine if the current subframe n is a packet continuation. If the current subframe n is a continuation of the packet, the flow of control proceeds to step 420, otherwise the flow of control proceeds to step 422.

In step 420, since the current subframe n is a continuation of the packet, the transmission power α_nIs set to the previous value alpha_n-3。

In step 420, since the current subframe n is a continuation of the packet, the transmission power α_nIs set to the previous value for a given interlace. In the embodiment with three interlaces, α_n＝α_n-3。

In step 422, the access terminal allocates transmit power α_nSo that α is_n＜＝β_nAnd α_nIs the effective T2P power level for the actual physical transmission rate and delay target (latency goal). Allocating transmission power alpha_nSo that α is_n＜＝β_nWhich means allocated for the transmission power a_nCannot be greater than the amount of power β comprised in the token bucket_n。

It is generally desirable to allocate a sufficiently high transmit power to meet the delay target. The data may have a latency deadline requirement. Such data must be transmitted over a period of time. Such data must meet latency targets. To meet the delay target, the transmit power must be high enough to transmit data within its deadline requirement. Power is allocated to transmit power so that its respective data rate and termination goal (termination goal) can cause data to be transmitted within its deadline requirements.

Table 2 below is a table of goodput versus payload size (bits) and termination time (slot) according to an embodiment. In another embodiment, there may be more or less data rates, as would be apparent to one skilled in the art.

At the time of allocation, the access terminal selects T2P based on the termination targets of 4, 8, 12, and 16 slots. Since the delay of a packet is affected by the time taken for transmission, the termination target for that packet may also be referred to as a "delay target".

TABLE 2

From steps 420 through 422, the flow of control proceeds to step 424. In step 424, a check is made to determine α_nWhether or not the choice of (c) is limited by data availability or available physical transmit power. If there is no data to send, α_nIs data limited. If the allocated transmission power alpha_nAbove the available physical transmit power, the access terminal is limited to the available physical transmit power. If α is_nIs limited by data availability or available physical transmit power, control proceeds to step 426 and DataPowLim_nIs set to true, otherwise control flows to step 428 and DataPowLim_nIs set to false. From steps 426 through 428, control passes to step 430.

In step 430, token bucket β is updated with the outgoing flow_n. Subtracting the allocated transmit power, i.e. beta, from the token bucket_n＝β_n-α_n. From step 430, control passes to step 432 where the reverse link Mac algorithm is repeated for the next subframe.

The processed data is forwarded to transmit subsystem 44 for transmission over the reverse link at the assigned transmit power α_nAnd carrying out transmission.

Although the reverse link Mac algorithm of fig. 4 uses only two filters for RAB, in another embodiment, any number of filters for RAB may be used to determine the continuous flow power level, as will be apparent to those skilled in the art.

Fig. 6 is a block diagram of QRAB and FRAB generation according to an embodiment. Each sector determines its loading level and uses its loading level to set up the RAB. The RAB is updated and broadcast every slot.

Sector i 602 sends a RAB (RAB) over wireless communication channel 604_∈{±1}) The RAB is received by the RAB demodulator 606 of the access terminal 600. The RAB demodulator 606 demodulates a received signal including the RAB, and outputs a Log Likelihood Ratio (LLR) (∞ LLR < ∞). In an embodiment, the LLRs are mapped by mapper 608 to avoid a single large value from the bias filter output before filtering. In an embodiment, a hyperbolic tangent function is used for the mapping. In an embodiment, the hyperbolic tangent function is y ═ e^x/2-e^-x/2)/(e^x/2-e^-x/2) For all real numbers x, -1 < y < 1. The mapping is a minimum mean square error solution for 1-slot RAB estimation. The output of mapper 608 is fed to IIR filter 610 and IIR filter 612 at each time slot. In an embodiment, IIR filter 610 has a short time constant τ for four slots_s. QRAB is sampled 614 at sampler 614 within each subframe n.

In each subframe, each access terminal determines a QRAB value for each sector in its active set, which is the hard-limited output of the IIR filter for each sector. The AT combines the QRAB from all sectors in its active set and adjusts its data rate accordingly.

FRAB is a measure of sector loading similar to QRAB, but by having a long time constant τ_LThe sector RAB is transmitted to obtain the FRAN. In the examples, τ_LIs 256 time slots. While QRAB is relatively instantaneous, FRAB provides long-term sector loading information.

Increment of power level Δ Φ for determining a rising value_nIs a function taking into account the data class C_nAs a function of priority. In an embodiment, the data class is quality of service (Q)oS) service classes within the framework. In one embodiment, the QoS framework is a Differentiated Service (Differentiated Service). Embodiments include (but are not limited to) three service classes: (1) expedited Forwarding (EF); (2) assured Forwarding (AF); and (3) Best Effort (BE). In an embodiment, the three categories are processed in a priority ordering, with EF having the highest priority, AF having a medium priority, and BE having a low priority. The RLMac receives these classes of service in three separate queues.

From data class c_nDetermine the increment delta phi used for determining the power level_n、f_d，cn(Φ_n，FRAB_n) And f_u，cn(Φ_n，FRAB_n) The parameters of the function of (1). c. C_nIs the highest priority class at the access terminal with any non-empty queue. The parameters of the function are determined by the data class, indicating the relative priority of the different data flows through the access terminal.

f_d，cn(Φ_n，FRAB_n) And f_u，cn(Φ_n，FRAB_n) Is a two-dimensional piecewise linear function with the parameters determined by c. In an embodiment, 11T 2P points and 3 FRAB points provide 33 points at which each f is explicitly specified_d，cnAnd f_u，cn. These points for the falling and rising functions are designated as D, respectively_1，c，D_2，c，D_3，c,.. and U_1，c，U_2，c，U_3，uWhere each U and D is an 11 x 1 vector. The access terminal performs bilinear interpolation. The highest specified FRAB point may be less than unity, at which the value saturates.

In an embodiment, for a fixed Φ_n，f_d，cn(Φ_n，FRAB_n) Monotonically non-decreasing with respect to FRAB.

In an embodiment, for a fixed Φ_n，f_u，cn(Φ_n，FRAB_n) Monotonically non-increasing with respect to FRAB.

In an embodiment, for a fixed FRABn, the ratio f_u，cn(Φ_n，FRAB_n)/f_d，cn(Φ_n，FRAB_n) About phi_nMonotonically decreasing.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, 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, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, 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. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with the following components: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a field programmable gate array (FPFA) or other programmable logic device, discrete gate or transistor logic, discrete hardware elements, or any combination of the above for implementing the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as the following: a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. 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 storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to the described embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. 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.

Although the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. Such variations, modifications, additions and improvements are intended to fall within the scope of the invention as detailed within the following claims.

Claims (21)

1. A method for determining a data rate for a reverse link communication of an access terminal, the method comprising the steps of:

receiving a reverse activation bit;

transmitting the inverse activation bits to a first digital filter to produce first filtered inverse activation bits;

determining a continuous stream power level based on the first filtered reverse activity bit; and

determining the data rate based on the continuous stream power level.

2. The method of claim 1, wherein the data rate is determined based on determining a traffic-pilot power level and a bit allocation, the traffic-pilot power level and the bit allocation being determined based on the continuous flow power level.

3. The method of claim 1, wherein the reverse activity bit is received at each slot.

4. The method of claim 1, wherein the first digital filter has a short time constant reflecting a short term power loading of the communication system.

5. The method of claim 1, wherein the first digital filter has a long time constant reflecting a long term power loading of the communication system.

6. The method of claim 1, further comprising transmitting data at the data rate, wherein the data rate is determined by mapping the continuous stream power level to a discrete power level.

7. The method of claim 6, wherein the continuous flow power levels are mapped to discrete power levels such that an average of the discrete power levels over a period of time approximates an average of the flow power levels over the period of time.

8. The method of claim 1, further comprising passing the reverse activity bits to a second digital filter to produce second filtered reverse activity bits, wherein the continuous stream power level is further based on the second filtered reverse activity bits.

9. The method of claim 8, wherein the first digital filter has a short time constant reflecting a short term power loading of the communication system and the second digital filter has a long time constant reflecting a long term power loading of the communication system.

10. The method of claim 9, wherein the continuous stream power level is determined based on a function of parameters determined by the second filtered reverse activity bits.

11. The method of claim 9, wherein the continuous flow power level is determined based on a decreasing function of a parameter determined by the second filtered reverse activity bit if the first filtered reverse activity bit indicates a busy short-term power loading of the communication system.

12. The method of claim 11, wherein the decreasing function further determines a parameter from a previous continuous flow power level.

13. The method of claim 9, wherein the continuous stream power level is determined based on determining an ascending function of a parameter from the second filtered reverse activity bits if the first filtered reverse activity bits do not indicate a busy short-term power loading of the communication system and power and data are not limited.

14. The method of claim 13, wherein the increasing function further determines a parameter from a previous continuous flow power level.

15. The method of claim 9, further comprising transmitting data at the data rate, wherein the data rate is determined by mapping the continuous stream power level to a discrete power level.

16. The method of claim 15, wherein the continuous stream power levels are mapped to discrete power levels using a token bucket such that an average of the discrete power levels over a period of time approximates an average of the stream power levels over the period of time.

17. The method of claim 15, wherein the continuous stream power levels are mapped to discrete power levels using a token bucket, the continuous stream power levels are added to the token bucket, and the mapped discrete power levels are subtracted from the token bucket.

18. The method of claim 17, wherein the mapped discrete power levels do not exceed an accumulated amount of the continuous power levels added to the token bucket.

19. The method of claim 17, wherein an accumulated amount of the continuous power levels added to the token bucket does not exceed a maximum level value for the token bucket.

20. An apparatus for determining a data rate for a reverse link communication of an access terminal, comprising:

means for receiving a reverse activation bit;

means for passing the reverse activity bits to a digital filter to produce filtered reverse activity bits;

means for determining a continuous stream power level based on the filtered reverse activity bits; and

means for determining the data rate based on the continuous stream power level.

21. An apparatus for determining a data rate for a reverse link communication of an access terminal, comprising:

a receiving subsystem for receiving the reverse activation bit; and

a processor to apply a digital filter to the reverse activity bits to produce filtered reverse activity bits, to determine a continuous stream power level based on the filtered reverse activity bits, and to determine a data rate based on the continuous stream power level.