# Patent

## Title
Using differentiated reverse activity bits (RABs) based on mobile-station revision

## Abstract

Methods and systems are provided for improving reverse-link performance by using differentiated reverse activity bits (RABs) based on mobile-station revision. In an embodiment, an access node provides wireless service to first and second mutually exclusive sets of access terminals, the first operating according to IS-856, Release 0, the second according to IS-856, Revision A. The access node maintains first and second RAB thresholds, and periodically (a) measures reverse noise rise (RNR), (b) compares the RNR to the first and second thresholds, (c) transmits a first RAB to the first set of access terminals, and (d) transmits a second RAB to the second set of access terminals. The first RAB is set when the measured RNR exceeds the first threshold, and clear when it does not. The second RAB is set when the measured RNR exceeds the second RAB threshold, and clear when it does not.

## Background
BACKGROUND
1. Cellular Wireless Networks and EV-DO Generally
Many people use mobile stations, such as cell phones and personal digital assistants (PDAs), to communicate with cellular wireless networks. These mobile stations and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless communication protocol such as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-95 and IS-2000. Wireless networks that operate according to these specifications are often referred to as “1xRTT networks” (or “1x networks” for short), which stands for “Single Carrier Radio Transmission Technology.” These networks typically provide communication services such as voice, Short Message Service (SMS) messaging, and packet-data communication.
Mobile stations typically conduct these wireless communications with one or more base transceiver stations (BTSs), each of which send communications to and receive communications from mobile stations over the air interface. Each BTS is in turn communicatively connected with an entity known as a base station controller (BSC), which (a) controls one or more BTSs and (b) acts as a conduit between the BTS(s) and one or more switches or gateways, such as a mobile switching center (MSC) and/or packet data serving node (PDSN), which may in turn interface with one or more signaling and/or transport networks.
As such, mobile stations can typically communicate with one or more endpoints over the one or more signaling and/or transport networks from inside one or more coverage areas (such as cells and/or sectors) of one or more BTSs, via the BTS(s), a BSC, and an MSC and/or PDSN. In typical arrangements, MSCs interface with the public switched telephone network (PSTN), while PDSNs interface with one or more core packet-data networks and/or the Internet.
Recently, service providers have introduced mobile stations and wireless networks that communicate using a CDMA protocol known as EV-DO, which stands for “Evolution Data Optimized.” EV-DO networks, operating in conformance with one or more releases and/or revisions of industry specification IS-856, such as Release 0 and Revision A, both of which are hereby incorporated herein by reference, provide high rate packet-data service (including Voice over IP (VoIP) service) to mobile stations using a combination of time-division multiplexing (TDM) on the forward link (from the network to mobile stations) and CDMA technology on the reverse link (from mobile stations to the network). Furthermore, some “hybrid” mobile stations can communicate with both 1x networks and EV-DO networks.
In the EV-DO context, a mobile station is typically referred to as an access terminal, while the network entity with which the access terminal communicates over the air interface is known as an access node. The access node typically includes a device known as a radio network controller (RNC), which is similar to a BSC in 1x networks. The access node also includes one or more BTSs, each including one or more antennas that radiate to define wireless coverage areas such as cells and sectors. Note that sectors are used in the balance of this written description as an example of a wireless coverage area, though this is for explanation and not to the exclusion of cells or other coverage areas. Among other functions, the RNC controls one or more BTSs, and acts as a conduit between the BTSs and a PDSN, which provides access to a packet-data network. Thus, when positioned in a sector provided by an access node, an access terminal may communicate over the packet-data network via the access node and the PDSN.
2. Reverse Noise Rise
In general, in a given sector, an access node can provide service to access terminals on one carrier frequency (i.e. carrier), or on more than one. Furthermore, interference can be, and often is, present on a carrier in a sector. As used herein, an instance of a given carrier in a given sector may be referred to as a sector-carrier. In general, on a sector-carrier, an access node receives transmissions from access terminals operating on that sector-carrier. However, the access node often also receives transmissions on that sector-carrier from other access terminals, other devices, and/or any other sources of interference on that frequency.
At a given moment, the sum total of what an access node is receiving on a given sector-carrier is known as the reverse noise on that sector-carrier. At regular intervals, and in fact quite frequently (e.g., once for every forward-link timeslot (i.e. once every approximately 1.67 ms)), access nodes compute reverse noise rise (RNR), which is the difference between (i) the reverse noise that the access node is currently detecting and (ii) a baseline level of reverse noise. Thus, the access node computes how far the reverse noise has risen above that baseline.
To determine the baseline, EV-DO networks typically periodically utilize what is known as a silent interval, which may occur on the order of once every five minutes, and last on the order of 40-100 ms, both of which are typically configurable. During the silent interval, access terminals know not to transmit anything to the access node. The access node can then measure whatever else is out there. As such, the baseline corresponds to the amount of reverse noise when the sector-carrier is unloaded (i.e. without any transmitting access terminals). And other reverse-link-noise levels, such as 24-hour or other minimums, could be used as a baseline.
In general, the lower the RNR is at a given moment, the more favorable the RF conditions are for communication between access terminals and an access node at that moment. Correspondingly, the higher the RNR, the less favorable the RF conditions are. Moreover, a low RNR generally corresponds to a sector-carrier being lightly loaded, in other words that is supporting communications for a relatively low number of access terminals. A high RNR, as one might expect, generally corresponds to a sector-carrier being heavily loaded, in other words that is supporting communications for a relatively high number of access terminals.
3. Reverse Activity Bit (RAB)
Access nodes typically use the calculated value of RNR to, among other things, set or clear what is known as the Reverse Activity Bit (RAB), which is a value that the access node makes equal to 0 or 1, and repeatedly transmits to all the access terminals operating on a given sector-carrier. Note that making the RAB equal to 0 is known as “clearing” the RAB, while making the RAB equal to 1 is known as “setting” the RAB. As stated, the access node typically calculates RNR at the same frequency at which it transmits forward-link timeslots, or once every 1.67 ms. The access node typically sets or clears the RAB at this same frequency.
With respect to how the access node chooses whether to set or clear the RAB, if the RNR is above a threshold (i.e. the “RNR threshold”), which is a configurable parameter that may be between 0 dB and 30 dB, the access node sets the RAB. If the RNR is below the RNR threshold, the access node clears the RAB. The access node transmits the RAB in a TDM channel—known as the reverse-activity channel—on the forward link. That channel is itself a TDM portion of a forward-link channel known as the Media Access Control (MAC) channel. Note that the RAB is the same for all access terminals on a sector-carrier. The manner in which those access terminals use the value of the RAB is explained below.
4. Access Terminals Using the RAB Under IS-856, Rel. 0
The initial release of IS-856 is referred to as Release 0 (Rel. 0), while a subsequent revision is referred to as Revision A (Rev. A). This subsection relates to how EV-DO access terminals use the RAB in EV-DO networks that operate according to Rel. 0, while the next subsection relates to how EV-DO access terminals use the RAB in EV-DO networks that operate according to Rev. A. Note that some EV-DO networks may provide both Rel. 0 and Rev. A service; that is, a given EV-DO network may provide service to access terminals that operate according to Rel. 0, and also to access terminals that operate according to Rev. A.
Under Rel. 0, access terminals can transmit data to access nodes on the reverse link at five different data rates: 9.6 kilobits per second (kbps), 19.2 kbps, 38.4 kbps, 76.8 kbps, and 153.6 kbps. Transmission at these various data rates involves using different types of coding for the data to be transmitted, among other differences. Note that, during a given instance of an access terminal transmitting data to an access node, the access terminal typically starts out using the lowest of those data rates, 9.6 kbps.
Recall that the EV-DO reverse link is essentially a CDMA channel over which the access terminal transmits data to the access node. And the access terminal does so in units of time known as frames, each of which last approximately 26.67 ms, which is the length of time of 16 timeslots on the forward link. And the network is synchronized on CDMA time, such that sets of 16 timeslots on the forward link will be aligned along reverse-link-frame time boundaries.
So, the EV-DO access terminal will transmit its first frame to the access node at 9.6 kbps. And then, for the next frame, the access terminal will stay at that rate, or perhaps transition up to 19.2 kbps. From there, frame by frame for all subsequent frames, the access terminal will transmit at the rate that it is currently using, transition up to the next-higher rate, or transition down to the next-lower rate. Note that rate-setting frequencies other than every frame, such as every other frame or perhaps every four frames, could be used as well.
These (in this example) frame-by-frame decisions to maintain or change the reverse-link data rate are controlled by the RAB and by a table of reverse-link transitional probabilities that are stored by each access terminal. This table is typically sent from the access node to the access terminal during the session-setup process, though it can also be sent (or updated) as new air-interface connections are made between the access node and the access terminal, or perhaps periodically, or perhaps in response to some other event.
The table typically contains eight probabilities, each expressed as an integer between 0 and 255, as explained more fully below. The eight probabilities correspond to the eight possible transitions among the five possible data rates. So, the transitional probabilities correspond to transitioning (in kbps) (1) from 9.6 up to 19.2, (2) from 19.2 up to 38.4, (3) from 38.4 up to 76.8, (4) from 76.8 up to 153.6, (5) from 153.6 down to 76.8, (6) from 76.8 down to 38.4, (7) from 38.4 down to 19.2, and (8) from 19.2 down to 9.6.
Typically, when an access terminal is at the start of transmitting a given frame at a given data rate (say, 38.4 kbps), the access terminal checks the RAB. If the RAB is cleared (i.e. equal to 0), the RNR in the sector is not above the RNR threshold, and thus the access terminal knows that it has two options with respect to the next frame: stay at 38.4 kbps or move up to 76.8 kbps. To determine which of those options the access terminal will take for the next frame, the access terminal generates a random integer between 0 and 255, and compares that random integer with the appropriate transitional probability. In this example, the access terminal would compare the random integer with the 38.4-kbps-to-76.8-kbps value.
If the random integer is less than or equal to the 38.4-kbps-to-76.8-kbps table value, the access terminal will transition up to 76.8 kbps for the next frame. If not, the access terminal will stay at 38.4 kbps for the next frame. The table value is thus a representation of a probability, since the integer that the access terminal compares with the table value is randomly generated. If, say, the table value were 255, the access terminal would have a probability of 1.00 (100%) for moving up to the next-higher data rate; if the table value were 0, the access terminal would only have a 1/256 probability of moving up. And so on.
If the RAB is set (again, equal to 1), however, the access node has decided that there is too much reverse noise on the sector-carrier at the moment, and thus the access terminal knows that it has two options with respect to the next frame. Again using 38.4 kbps as an example of the access terminal's current rate, the two options are to stay at 38.4 kbps or move down to 19.2 kbps. To determine which of those options the access terminal will take for the next frame, the access terminal again generates a random integer between 0 and 255, and compares that random integer with the appropriate reverse-link transitional probability. This time, the access terminal would compare the random integer with the 38.4-kbps-to-19.2-kbps value.
As with transitions up to higher data rates, when talking about transitions down to lower data rates, the access terminal checks whether the random integer it generates is less than or equal to the 38.4-to-19.2 table value. If so, the access terminal will transition down to 19.2 kbps for the next frame. If not, the access terminal will stay at 38.4 kbps for the next frame. Again, the table value represents a probability, as the integer that the access terminal compares with the table value is randomly generated. If, the table value were 255, the access terminal would have a probability of 1.00 (100%) for moving down to the next-lower data rate; if the table value were 0, the access terminal would only have a 1/256 probability of moving down. And so on.
5. Access Terminals Using the RAB Under IS-856, Rev. A
As explained above, under Rev. 0, reverse-link data rates are permitted only to increase or decrease by one step at a time (i.e. up to the next-higher data rate or down to the next-lower data rate), controlled by the RAB and the tables of reverse-link transitional probabilities. Under Rev. A, however, a more dynamic, iterative, equation-based approach is utilized, which permits data rates to change more rapidly.
Briefly, under Rev. A, the access node still repeatedly transmits a RAB equal to 0 or 1. Each individual access terminal then uses that value to compute what are known as a Quick Reverse Activity Bit (QRAB) and a Filtered Reverse Activity Bit (FRAB). The QRAB is binary (equal to 0 or 1), while the FRAB is a real number having a value anywhere between −1 and 1 inclusive. The QRAB is a short-term, binary indication of loading: a QRAB of 1 is associated with congestion on the sector-carrier, while a QRAB of 0 is associated with non-congestion. The FRAB is more of a long-term, continuous, historical value, where values closer to −1 indicate a lower degree of congestion on the sector-carrier reverse link, while values closer to 1 indicate a higher degree of congestion on the sector-carrier reverse link. Thus, both the QRAB and the FRAB reflect the access terminal's interpretation of the RAB from the access node.
The access terminal then calculates a value known in Rev. A as “T2PInflow.” T2PInflow is an iterative value: prior to each reverse-link transmission, it has a current value, and that current value is one of the inputs in determining its value in the next calculation. Note that the “T2P” prefixes to many of the value and function names in this explanation means “Traffic to Pilot,” as one governing principle that drives the determination of reverse-link data rates under Rev. A is the relative values of (1) the power level that the access terminal is using to transmit on the reverse-link portion of the traffic channel and (2) the power level at which the access terminal is detecting the pilot signal from the access node, as is known in the art.
Rev. A defines two functions called “T2PDn(.)” and “T2PUp(.),” both of which are functions of the current T2PInflow, FRAB, and a filtered value of the serving sector pilot strength. If the access terminal sets QRAB to 1 (corresponding to a relatively congested sector-carrier), then T2PInflow will be decremented by the result of T2PDn(.); if, on the other hand, the access terminal sets QRAB to 0 (corresponding to a relatively non-congested sector-carrier), then T2PInflow will be incremented by the result of T2PUp(.). As with all of the details of these computations, the detailed equations can be found in IS-856, Rev. A.
Under Rev. A, this updated T2PInflow value is then used as one of the inputs in what is referred to as a “token bucket” mechanism, which is used to determine a packet size for the next reverse-link transmission. And it is this packet size that essentially determines the reverse-link data rate at which the access terminal will be transmitting, based on a table that correlates packet sizes to data rates. In general, higher reverse-link data rates are correlated with higher reverse-link transmission power levels. In general, the token bucket mechanism is used as a regulator, to provide data-rate stability over time, while still permitting some instantaneous deviation.
One of the parameters of the token bucket mechanism is the “BucketLevel.” Using that value, the updated T2PInflow, and the FRAB, the access terminal calculates a value known as “PotentialT2POutflow.” The access terminal also maintains a data queue for outgoing data (i.e. data that is ready and waiting to be transmitted to the access node on the reverse link). The access terminal keeps track of the current size of this data queue in a variable referred to here as the “data queue size.” The access terminal determines the packet size for the next transmission based on PotentialT2POutflow, the data queue size, other constraints and maximum/minimum allowed values, and the access terminal's transmission power.
As stated, the computed packet size essentially determines the reverse-link data rate. Under IS-856, Rev. A, effective reverse-link data rates can range from 19.2 kbps up to 1.84 megabits per second (Mbps). As a final part of the calculation, the access terminal computes a value known as “T2POutflow” (a.k.a. “actual T2POutflow”) based on the computed packet size. The access terminal then updates BucketLevel with the updated T2PInflow value and the newly-calculated (actual) T2POutflow value, so that BucketLevel will be ready for the next iteration.
Overview
As explained, EV-DO access terminals use the value of the RAB in different ways under IS-856, Rel. 0 and IS-856, Rev. A for determining their reverse-link data rates. However, under both standards, access nodes make repeated, periodic broadcasts of the RAB (equal to 0 or 1) on a given sector-carrier, and all of the access terminals on that sector-carrier, regardless of whether the access terminals are operating according to IS-856, Rel. 0 or IS-856 Rev. A, interpret the RAB by (a) maintaining or increasing their reverse-link data rates when the RAB is clear and (b) maintaining or decreasing their reverse-link data rates when the RAB is set.
Access terminals operating according to IS-856, Rel. 0 (“Rel. 0 access terminals”) have a maximum reverse-link burst rate of 153.6 kbps. In other words, when Rel. 0 access terminals are transmitting reverse-link data, they can do so no faster than 153.6 kbps. Access terminals operating according to IS-856, Rev. A (“Rev. A access terminals”), however, have a maximum reverse-link burst rate of 1.8 Megabits per second (Mbps). The conventional use of one RAB for all access terminals, Rel. 0 and Rev. A alike, on a sector-carrier has at least one undesirable consequence: when a sector-carrier is serving a mix of Rel. 0 and Rev. A access terminals, the Rel. 0 access terminals contribute reverse noise, which may trigger the setting of the RAB, which will hold down the reverse-link data rates of the Rev. A access terminals. Thus, Rev. A access terminals are not able to realize their full reverse-link potential, which negatively impacts the experience of users engaging in communications with Rev. A access terminals.
In accordance with the present methods and systems, an access node maintains separate RAB-triggering RNR thresholds (i.e. RAB thresholds) for Rel. 0 access terminals and for Rev. A access terminals (a “Rel. 0 RAB threshold” and a “Rev. A RAB threshold”). The access node correspondingly sends out two different RABs: one for Rel. 0 access terminals (the “Rel. 0 RAB”) and the other for Rev. A access terminals (the “Rev. A RAB”), where the set or clear state of each RAB is controlled by the respective RAB threshold corresponding to that RAB. In operation, then, an access node periodically (and, as described, quite frequently) (a) compares its most recent measurement of RNR to the Rel. 0 RAB threshold, and responsively sets or clears the Rel. 0 RAB accordingly and (b) compares its most recent measurement of RNR to the Rev. A RAB threshold, and responsively sets or clears the Rev. A RAB accordingly.
Further in accordance with the present methods and systems, Rel. 0 access terminals monitor forward-link transmissions from the access node for the state of the Rel. 0 RAB, and then process the Rel. 0 RAB as described above with respect to Rel. 0 access terminals processing the set or clear state of the RAB. Additionally, Rev. A access terminals monitor forward-link transmissions from the access node for the state of the Rev. A RAB, and then process the Rev. A RAB as described above with respect to Rev. A access terminals processing the set or clear state of the RAB. In an embodiment, the access node transmits the Rel. 0 RAB in MAC sub-channel 0, and Rel. 0 access terminals monitor that sub-channel for the state of the Rel. 0 RAB; further to this embodiment, the access node transmits the Rev. A RAB in MAC sub-channel 1, and Rev. A access terminals that sub-channel for the state of the Rev. A RAB.
In an embodiment, the access node from time to time dynamically changes the value of the Rel. 0 RAB threshold and the Rev. A RAB threshold for a given sector-carrier based on the relative mixture of Rel. 0 access terminals and Rev. A access terminals on the sector-carrier at the time. Thus, the access node may compute a ratio (which may hereinafter be referred to as the “Rel. 0 ratio”) of (a) Rel. 0 access terminals being served on the sector-carrier to (b) all access terminals being served on the sector carrier. Instead or in addition, the access node may compute a ratio (which may hereinafter be referred to as the “Rev. A ratio”) of (a) Rev. A access terminals being served on the sector-carrier to (b) all access terminals being served on the sector carrier. Of course, either or both of these ratios could be expressed as percentages, decimal numbers, etc. Thus, if there were 10 Rel. 0 access terminals and 30 Rev. A access terminals on a given sector-carrier, the Rel. 0 ratio would be 0.25, and the Rev. A ratio would be 0.75.
Upon computing the Rel. 0 ratio and/or the Rev. A ratio, the access node uses one or both of those values to determine values (until the next iteration) for the Rel. 0 RAB threshold and the Rev. A RAB threshold. In an embodiment, the access node computes the Rel. 0 ratio and then uses that computed value as a key into a table of pairs of Rel. 0 RAB thresholds and Rev. A RAB thresholds for various ranges of Rel. 0 ratios. In another embodiment, the table may contain offsets (i.e. differentials, deltas, etc.) than can be added or subtracted to respective default Rel. 0 and Rev. A RAB-threshold values to arrive at operational Rel. 0 and Rev. A RAB thresholds.
And other implementations are certainly possible as well, such as computing and using the Rev. A ratio instead of the Rel. 0 ratio as a key into a table of thresholds or offsets. In some embodiments, a Rel. 0 offset and a Rev. A offset may be identified and then added to the same default RAB threshold. For example, a certain Rel. 0 ratio may correlate with (a) adding a negative Rel. 0 offset (e.g. −2 dB) to a given default threshold to arrive at an operational Rel. 0 RAB threshold and (b) adding a positive Rev. A offset (e.g. 2 dB) to the same default threshold to arrive at an operational Rev. A RAB threshold. In some embodiments, the Rel. 0 and Rev. A RAB thresholds could be computed based on at least one of the Rel. 0 ratio and the Rev. A ratio, without reference to a lookup table. In any event, the access node may then provide service using the computed operational Rel. 0 and Rev. A RAB thresholds until the next iteration.
In general, a relatively high RAB threshold would correspond with a RAB being clear the majority of the time, since it would require a relatively high level of RNR to exceed that RAB threshold in order to set the RAB; thus, a relatively high RAB threshold would allow for reverse-link data rates to ramp up to relatively high levels, improving user experience. And a relatively low RAB threshold would correspond with a RAB being set the majority of the time, since it would require only a relatively low level of RNR to exceed that RAB threshold in order to set the RAB; thus, a relatively low RAB threshold would tend to hold down reverse-link data rates at relatively low levels, perhaps causing a worse user experience.
Thus, in an embodiment, between Rel. 0 and Rev. A access terminals, whichever group is more well represented at a given time on a given sector-carrier will be favored with an increased RAB threshold, and thus increased potential for higher reverse-link data rates, while the group that is less well represented will experience a decreased RAB threshold, and thus decreased potential for higher reverse-link data rates.
In one example, if the Rel. 0 ratio was greater than or equal to 0.20 and less than 0.30, the access node may offset the Rel. 0 RAB threshold from a default RAB threshold by −3 dB, and may offset the Rev. A RAB threshold from the same default RAB threshold by +3 dB. If, however, the Rel. 0 ratio was greater than or equal to 0.70 and less than 0.80, the access node may do the opposite; that is, the access node may offset the Rel. 0 RAB threshold from the default RAB threshold by +3 dB, and may offset the Rev. A RAB threshold from the same default RAB threshold by −3 dB. And clearly numerous other examples are possible as well.
Note that an access node may identify a given access terminal as a Rel. 0 access terminal or Rev. A access terminal by an identifier known as a MAC ID that is assigned to each access terminal during session setup. In one embodiment, MAC IDs 2-63 may be assigned to Rev. A access terminals, while MAC IDs 64-127 may be assigned to Rel. 0 access terminals. As described above, the access node may use MAC sub-channel 0 to transmit the Rel. 0 RAB, and may use MAC sub-channel 1 to transmit the Rev. A RAB. And other arrangements are certainly possible, such as assigning different ranges of MAC IDs to Rel. 0 and Rev. A access terminals, using different MAC sub-channels for the two RABs, reserving additional and/or different MAC sub-channels for other administrative purposes, and/or many other possibilities.
And it should be noted that the above overview is illustrative and not limiting. That is, additional and/or different features may be present in some embodiments of the present invention. It should be noted as well that any description of an access node and/or one or more access terminals communicating according to EV-DO is by way of example, and that any suitable modes (e.g. protocols) may be used instead, such as CDMA, iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, WiMax (e.g. IEEE 802.16), LTE, microwave, satellite, MMDS, Wi-Fi (e.g. IEEE 802.11), Bluetooth, infrared, and/or any other now known or later developed.



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



DETAILED DESCRIPTION OF THE DRAWINGS
1. Exemplary Architecture
FIG. 1 is a simplified block diagram of a communication system, in accordance with exemplary embodiments. It should be understood that this and other arrangements described herein are set forth only as examples. Those skilled in the art will appreciate that other arrangements and elements (e.g., machines, interfaces, functions, orders, and groupings of functions, etc.) can be used instead, and that some elements may be omitted altogether. Further, many of the elements described herein are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, and in any suitable combination and location. Various functions described herein as being performed by one or more entities may be carried out by hardware, firmware, and/or software. Various functions may be carried out by a processor executing instructions stored in memory.
As shown in FIG. 1, a communication system 100 includes an access terminal (AT) 102, an access node 105 (shown as comprising a BTS 103 and an RNC 104), a PDSN 106, a packet-data network (PDN) 108, a gateway 110, and a PDN 112. And additional entities not depicted could be present as well. For example, there could be more than one access terminal in communication with access node 105; also, there could be additional entities in communication with PDN 108 and/or PDN 112. Also, there could be one or more routers, switches, other devices and/or networks making up at least part of one or more of the communication links.
Access terminal 102 may be any device arranged to carry out the access-terminal functions described herein, and may include a user interface, a wireless-communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those access-terminal functions. The user interface may include buttons, a touchscreen, a microphone, and/or any other elements for receiving inputs from users, as well as a speaker, one or more displays, and/or any other elements for communicating outputs to users.
The wireless-communication interface may comprise an antenna and a chipset for communicating with one or more base stations over an air interface. As an example, the chipset could be one suitable for engaging in EV-DO communications, including IS-856, Rel. 0 and/or IS-856, Rev. A communications. The chipset or wireless-communication interface in general may also be able to communicate with a 1xRTT CDMA network, a Wi-Fi (IEEE 802.11) network, and/or one or more additional types of wireless networks. The processor and data storage may be any suitable components known to those of skill in the art. As examples, access terminal 102 could be or include a cell phone, a PDA, a computer, a laptop computer, a hybrid IS-2000/IS-856 device, and/or a multi-mode Wi-Fi/cellular device.
BTS 103 may be any one or any combination of network elements arranged to carry out the BTS functions described herein, and may include a communication interface, a processor, and data storage comprising instructions executable by the processor to carry out those BTS functions. The communication interface may include one or more antennas and chipsets or other components for providing one or more coverage areas such as cells or sectors according to a protocol such as CDMA, EV-DO, WiMax, or any other suitable protocol. The communication interface may also include a wired or wireless packet-data interface (which may be characterized as a backhaul connection), such as an Ethernet interface, for communicating with RNC 104.
RNC 104 may be any one or any combination of network elements arranged to carry out the RNC functions described herein. As such, RNC 104 may include a communication interface, a processor, and data storage comprising instructions executable by the processor to carry out those RNC functions. The communication interface may include a wired or wireless packet-data interface (which may be characterized as a backhaul connection), such as an Ethernet interface, for communicating directly or over one or more networks with PDSN 106. In general, RNC 104 functions to control one or more BTSs, and to serve as a conduit between the one or more BTSs and PDSN 106, enabling access terminals to communicate over PDN 108 and perhaps beyond.
Note that access node 105 may comprise BTS 103 and RNC 104, and may comprise one or more additional BTSs as well. In general, access node 105 provides wireless service to access terminals over an air interface, and uses a backhaul connection to provide transport service over PDN 108 (or perhaps PDN 108 and PDN 112) to those access terminals.
PDSN 106 may be any networking server or other device arranged to carry out the PDSN functions described herein. PDSN 106 may include a communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those PDSN functions. The communication interface may include a wired packet-data interface such as an Ethernet interface for communicating with access node 105 and/or over PDN 108. Note that PDSN 106 may, instead or in addition, comprise a wireless-communication interface for communicating with access node 105 and/or over PDN 108. Note also that PDSN 106 may use the same interface or separate interfaces for communicating with access node 105 and for communicating over PDN 108. PDSN 106 may generally function to provide access node 105 with access to PDN 108, and vice versa.
Each of PDN 108 and PDN 112 may include one or more wide area networks, one or more local area networks, one or more public networks such as the Internet, one or more private networks, one or more wired networks, one or more wireless networks, and/or one or more networks of any other type. Devices in communication with PDN 108 and/or PDN 112 may exchange data using a packet-switched protocol such as IP, and may be identified by an address such as an IP address. In this example, PDN 108 is the service provider's privately-operated IP network (where the service provider may operate at least access node 105 and PDSN 106), while PDN 112 is the Internet. However, this is for illustration and not by way of limitation. In some embodiments, PDSN 106 may connect directly to the Internet, in which case PDN 108 and gateway 110 may not be necessary. And other configurations are certainly possible as well.
Gateway 110 may be any networking server or other device arranged to carry out the gateway functions described herein. Thus, gateway 110 may include a communication interface, a processor, and data storage comprising instructions executable by the processor for carrying out those gateway functions. The communication interface may include a wired packet-data interface, such as an Ethernet interface, for communicating over PDN 108 and/or PDN 112. Note that gateway 110 may, instead or in addition, comprise a wireless-communication interface for communicating over PDN 108 and/or PDN 112. Gateway 110 may use the same interface or separate interfaces for communicating over PDN 108 and/or PDN 112. Gateway 110 may generally function to provide PDN 108 and PDN 112 with connectivity to each other.
2. Exemplary Operation
FIG. 2 depicts an exemplary method that may be carried out by an access node such as access node 105. And although method 200 is described herein as being carried out by access node 105, this is not required; in general, method 200 may be carried out by an access node, a BTS, an RNC, a PDSN, one or more other network entities, or some combination thereof.
At step 202, access node 105 provides wireless service to a plurality of access terminals on a carrier (e.g. a sector-carrier) in a coverage area (e.g. a sector). The plurality of access terminals consists of a first subset and a second subset, where the first and second subsets are mutually exclusive. The first subset operates according to IS-856, Rel. 0, and the second subset operates according to IS-856, Rev. A.
At step 204, access node 105 maintains a first (i.e. Rel. 0) RAB threshold and a second (i.e. Rev. A) RAB threshold. Step 204 may comprise periodically selecting values for the first and second RAB thresholds based on at least one of (1) a first ratio of (a) the number of access terminals in the first subset to (b) a total number of access terminals in the first and second subsets and (2) a second ratio of (a) the number of access terminals in the second subset to (b) the total number of access terminals in the first and second subsets. In some embodiments, only the first ratio is used. In other embodiments, only the second ratio is used. In still other embodiments, both ratios are used. Note that computing one of the ratios essentially computes the other as well, as the first and second ratios will add up to 1.
In an embodiment, selecting values for the first and second RAB thresholds involves using one or both of the first ratio and the second ratio as a key into a table, in order to identify in the table the values for the first and second RAB thresholds. Access node 105 would then operate using those identified values. In an embodiment, the identified values are correlated in the table with a range of ratio values, wherein the range includes the first or second ratio.
In an embodiment, selecting values for the first and second RAB thresholds involves using one or both of the first ratio and the second ratio as a key into a table, in order to identify in the table respective offset values for the first and second RAB thresholds. Access node 105 may maintain first and second default RAB thresholds that correspond to the first and second RAB thresholds. Note that the first default RAB threshold may be either equal or not equal to the second default RAB threshold.
As such, access node 105 may compute values for the first RAB threshold and/or the second RAB threshold by adding a respective offset value to a respective default RAB threshold to compute a respective RAB threshold to use in operation. Instead or in addition, access node 105 may subtract a respective offset value from a respective default RAB threshold to compute a respective RAB threshold to use in operation. And other examples are certainly possible as well.
At step 206, access node 105 periodically carries out a number of sub-steps including (a) measuring RNR on the carrier, (b) comparing the measured RNR to each of the first and second RAB thresholds, (c) transmitting a first RAB to the first subset of access terminals, and (d) transmitting a second RAB to the second subset of access terminals. Access node 105 sets the first RAB when the measured RNR exceeds the first RAB threshold, and clears the first RAB when the measured RNR does not exceed the first RAB threshold. Similarly, access node 105 sets the second RAB set when the measured RNR exceeds the second RAB threshold, and clears the second RAB clear when the measured RNR does not exceed the second RAB threshold.
As stated above, in an embodiment, access node 105 may transmit the first RAB to the first subset of access terminals in a first MAC sub-channel, and similarly may transmit the second RAB to the second subset of access terminals in a second MAC sub-channel different from the first. The access terminals in the first subset may monitor the first MAC sub-channel for the first RAB, and the access terminals in the second subset may monitor the second MAC sub-channel for the second RAB. As explained, a RAB being set causes an access terminal receiving that RAB to maintain or decrease its reverse-link data rate, while the RAB being clear causes the access terminal to maintain or increase its reverse-link data rate.
3. Conclusion
Various exemplary embodiments have been described above. Those skilled in the art will understand, however, that changes and modifications may be made to those examples without departing from the scope of the claims.

## Claims

1. A method comprising:
an access node providing wireless service to a plurality of access terminals on a carrier in a coverage area, the plurality of access terminals consisting of a first subset and a second subset, the first and second subsets being mutually exclusive, the first subset operating according to IS-856, Release 0, and the second subset operating according to IS-856, Revision A;
the access node maintaining a first reverse activity bit (RAB) threshold and a second RAB threshold; and
the access node periodically:
measuring reverse noise rise (RNR) on the carrier,
comparing the measured RNR to each of the first and second RAB thresholds,
transmitting a first RAB to the first subset of access terminals, wherein the first RAB is set when the measured RNR exceeds the first RAB threshold, and wherein the first RAB is clear when the measured RNR does not exceed the first RAB threshold, and
transmitting a second RAB to the second subset of access terminals, wherein the second RAB is set when the measured RNR exceeds the second RAB threshold, and wherein the second RAB is clear when the measured RNR does not exceed the second RAB threshold.

2. The method of claim 1, wherein the coverage area is a sector, and wherein the carrier is a sector-carrier.

3. The method of claim 1, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on at least one of (1) a first ratio of (a) a number of access terminals in the first subset to (b) a total number of access terminals in the first and second subsets and (2) a second ratio of (a) a number of access terminals in the second subset to (b) the total number of access terminals in the first and second subsets.

4. The method of claim 3, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on the first ratio.

5. The method of claim 3, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on the second ratio.

6. The method of claim 3, wherein selecting values for the first and second RAB thresholds comprises using at least one of the first ratio and the second ratio as a key into a table, wherein the access node uses the at least one ratio to identify in the table the values for the first and second RAB thresholds.

7. The method of claim 6, wherein the identified values are correlated in the table with a range of ratio values, wherein the range includes the first or second ratio.

8. The method of claim 3, wherein selecting values for the first and second RAB thresholds comprises using at least one of the first ratio and the second ratio as a key into a table, wherein the access node uses the at least one ratio to identify in the table respective offset values for the first and second RAB thresholds.

9. The method of claim 8, further comprising the access node maintaining first and second default RAB thresholds, wherein selecting values for the first and second RAB thresholds comprises at least one of (a) adding a respective offset value to a respective default RAB threshold to compute a respective RAB threshold and (b) subtracting a respective offset value from a respective default RAB threshold to compute a respective RAB threshold.

10. The method of claim 9, wherein the first default RAB threshold is equal to the second default RAB threshold.

11. The method of claim 9, wherein the first default RAB threshold is not equal to the second default RAB threshold.

12. The method of claim 1, wherein transmitting the first RAB to the first subset of access terminals comprises transmitting the first RAB in a first MAC sub-channel, and wherein transmitting the second RAB to the second subset of access terminals comprises transmitting the second RAB in a second MAC sub-channel different from the first MAC sub-channel,
wherein the access terminals in the first subset monitor the first MAC sub-channel for the first RAB, and wherein the access terminals in the second subset monitor the second MAC sub-channel for the second RAB.

13. The method of claim 1, wherein a given RAB being set causes a given access terminal receiving the given RAB to maintain or decrease a reverse-link data rate for the given access terminal, and wherein the given RAB being clear causes the given access terminal to maintain or increase the reverse-link data rate for the given access terminal.

14. An access node comprising:
a communication interface comprising a wireless-communication interface;
a processor; and
data storage comprising instructions executable by the processor for causing the access node to carry out functions including:
providing wireless service to a plurality of access terminals on a carrier in a coverage area, the plurality of access terminals consisting of a first subset and a second subset, the first and second subsets being mutually exclusive, the first subset operating according to IS-856, Release 0, and the second subset operating according to IS-856, Revision A;
maintaining a first reverse activity bit (RAB) threshold and a second RAB threshold; and
periodically:
measuring reverse noise rise (RNR) on the carrier,
comparing the measured RNR to each of the first and second RAB thresholds,
transmitting a first RAB to the first subset of access terminals, wherein the first RAB is set when the measured RNR exceeds the first RAB threshold, and wherein the first RAB is clear when the measured RNR does not exceed the first RAB threshold, and
transmitting a second RAB to the second subset of access terminals, wherein the second RAB is set when the measured RNR exceeds the second RAB threshold, and wherein the second RAB is clear when the measured RNR does not exceed the second RAB threshold.

15. The access node of claim 14, wherein the coverage area is a sector, and wherein the carrier is a sector-carrier.

16. The access node of claim 14, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on at least one of (1) a first ratio of (a) a number of access terminals in the first subset to (b) a total number of access terminals in the first and second subsets and (2) a second ratio of (a) a number of access terminals in the second subset to (b) the total number of access terminals in the first and second subsets.

17. The access node of claim 16, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on the first ratio.

18. The access node of claim 16, wherein maintaining the first RAB threshold and the second RAB threshold comprises periodically selecting values for the first and second RAB thresholds based on the second ratio.

19. The access node of claim 16, wherein selecting values for the first and second RAB thresholds comprises using at least one of the first ratio and the second ratio as a key into a table, wherein the access node uses the at least one ratio to identify in the table the values for the first and second RAB thresholds.

20. The access node of claim 19, wherein the identified values are correlated in the table with a range of ratio values, wherein the range includes the first or second ratio.

21. The access node of claim 16, wherein selecting values for the first and second RAB thresholds comprises using at least one of the first ratio and the second ratio as a key into a table, wherein the access node uses the at least one ratio to identify in the table respective offset values for the first and second RAB thresholds.

22. The access node of claim 21, the data storage further comprising instructions for maintaining first and second default RAB thresholds, wherein selecting values for the first and second RAB thresholds comprises at least one of (a) adding a respective offset value to a respective default RAB threshold to compute a respective RAB threshold and (b) subtracting a respective offset value from a respective default RAB threshold to compute a respective RAB threshold.

23. The access node of claim 22, wherein the first default RAB threshold is equal to the second default RAB threshold.

24. The access node of claim 22, wherein the first default RAB threshold is not equal to the second default RAB threshold.

25. The access node of claim 14, wherein transmitting the first RAB to the first subset of access terminals comprises transmitting the first RAB in a first MAC sub-channel, and wherein transmitting the second RAB to the second subset of access terminals comprises transmitting the second RAB in a second MAC sub-channel different from the first MAC sub-channel,
wherein the access terminals in the first subset monitor the first MAC sub-channel for the first RAB, and wherein the access terminals in the second subset monitor the second MAC sub-channel for the second RAB.