The benefit OF U.S. provisional application No.60/843,219 entitled "a METHOD and apparatus FOR INTERACTION OF FAST OTHER Search Interference (OSI) WITH SLOW OSI", filed on 8.9.2006, which is hereby incorporated by reference in its entirety.
Detailed Description
Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such embodiment(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.
As used in this application, the terms "component," "module," "system," and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. For example, in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the internet with other systems via the signal), the components may communicate by way of local and/or remote threads.
Moreover, various embodiments are described herein in connection with a wireless terminal and/or a base station. A wireless terminal may refer to a device that provides voice and/or data connectivity to a user. The wireless terminal may be connected to a computing device such as a laptop computer or desktop computer, or it may be a self-contained device such as a Personal Digital Assistant (PDA). A wireless terminal can also be called a system, a subscriber unit, subscriber station, mobile station, handset, remote station, access point, remote terminal, access terminal, user agent, user device, or user equipment. A wireless terminal may be a subscriber station, wireless device, cellular telephone, PCS telephone, cordless telephone, Session Initiation Protocol (SIP) phone, Wireless Local Loop (WLL) station, Personal Digital Assistant (PDA), handheld device having wireless connection capability, or other processing device connected to a wireless modem. A base station (e.g., access point) can refer to a device in an access network that communicates over the air-interface, through one or more sectors, with wireless terminals. By converting received air-interface frames into IP packets, the base station may act as a router between the wireless terminal and the rest of the access network, which may include an Internet Protocol (IP) network. The base station also coordinates management of attributes for the air interface.
Moreover, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media may include magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., Compact Disk (CD), Digital Versatile Disk (DVD), etc.), smart cards, and flash memory devices (e.g., card, stick, key drive, etc.).
Various embodiments will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include devices, components, modules, etc. other than those discussed in connection with the figures and/or may not include all of the devices, components, modules, etc. discussed in connection with the figures. Combinations of these approaches may also be used.
Referring now to fig. 1, fig. 1 illustrates a wireless multiple-access communication system 100 in accordance with various aspects. In one example, wireless multiple-access communication system 100 includes a plurality of base stations 110 and a plurality of terminals 120. Further, one or more base stations 110 can communicate with one or more terminals 120. By way of non-limiting example, a base station 110 can be an access point, a node B, and/or another suitable network entity. Each base station 110 provides communication coverage for a particular geographic area 102 a-c. As used herein and generally in the art, the term "cell" can refer to a base station 110 and/or its coverage area 102 depending on the context in which the term is used.
To improve system capacity, the coverage area 102 corresponding to a base station 110 may be partitioned into multiple smaller areas (e.g., areas 104a, 104b, and 104 c). Each of the smaller areas 104a, 104b, and 104c may be served by a respective base transceiver subsystem (BTS, not shown). As used herein and generally in the art, the term "sector" can refer to a BTS and/or its coverage area depending on the context in which the term is used. In one example, sectors 104 in cell 102a can be formed by groups of antennas (not shown) at base station 110, where each group of antennas is responsible for communication with terminals 120 in a portion of cell 102. For example, a base station 110 serving cell 102a can have a first antenna group corresponding to sector 104a, a second antenna group corresponding to sector 104b, and a third antenna group corresponding to sector 104 c. However, it should be appreciated that the various aspects disclosed herein may be used in a system having sectorized cells and/or unsectorized cells. Moreover, it should be appreciated that all suitable wireless communication networks having any number of sectorized and/or unsectorized cells are intended to fall within the scope of the hereto appended claims. For simplicity, the term "base station" as used herein may refer to both a station serving a sector as well as a station serving a cell. As also used herein, a "serving" access point is an access point with which a given terminal is primarily engaged in forward link and/or reverse link traffic transmissions, and a "neighboring" access point is an access point with which the given terminal is not primarily transmitting traffic data. Although the following description generally refers to a system in which each terminal communicates with one serving access point for simplicity, it should be appreciated that terminals can communicate with any number of serving access points. For example, terminals 120 in system 100 can communicate with multiple base stations 110 using separate links, where a given terminal 120 can have different serving sectors for multiple forward and reverse links. In this example, the forward link serving sector can be considered a neighbor sector for interference management purposes. In another example, an access terminal can conduct traffic transmissions on the forward link or control transmissions on the forward link and/or reverse link with non-serving neighbor sectors.
According to one aspect, terminals 120 can be dispersed throughout system 100. Each terminal 120 may be fixed or mobile. By way of non-limiting example, a terminal 120 can be an Access Terminal (AT), a mobile station, a user device, a subscriber station, and/or another suitable network entity. Terminal 120 may be a wireless device, a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem, a handheld device, or another suitable device. Further, at any given moment, a terminal 120 can communicate with any number of base stations 110 or no base stations 110.
In another example, system 100 can employ a centralized architecture through the use of a system controller 130 that can connect to one or more base stations 110 and provide coordination and control for base stations 110. According to alternative aspects, system controller 130 may be a single network entity or a collection of network entities. Additionally, system 100 can employ a distributed architecture, allowing base stations 110 to communicate with one another as needed. In one example, system controller 130 may additionally contain one or more connections to multiple networks. These networks may include the internet, other packet-based networks, and/or circuit-switched voice networks that may provide information to terminals 120 in communication with one or more base stations 110 in system 100 and/or obtain information from terminals 120 in communication with one or more base stations 110 in system 100. In another example, system controller 130 can include or be coupled with a scheduler (not shown) that can schedule transmissions to and/or from terminals 120. Alternatively, the scheduler may be included in each cell 102, each sector 104, or a combination thereof.
In one example, system 100 can employ one or more multiple-access schemes such as CDMA, TDMA, FDMA, OFDMA, Single-Carrier FDMA (SC-FDMA), and/or other suitable multiple-access schemes. TDMA utilizes Time Division Multiplexing (TDM), in which transmissions for different terminals 120 are orthogonalized by transmitting the transmissions for the different terminals 120 in different time intervals. FDMA utilizes Frequency Division Multiplexing (FDM), in which transmissions for different terminals 120 are made orthogonal by sending the transmissions for different terminals 120 in different frequency subcarriers. In one example, TDMA and FDMA systems can also use Code Division Multiplexing (CDM), in which transmissions for multiple terminals can be orthogonalized using different orthogonal codes (e.g., walsh codes) even though they are sent within the same time interval or frequency subcarrier. OFDMA utilizes Orthogonal Frequency Division Multiplexing (OFDM), and SC-FDMA utilizes single-carrier frequency division multiplexing (SC-FDM). OFDM and SC-FDM may partition the system bandwidth into multiple orthogonal subcarriers (e.g., tones, bins, etc.), each of which may be modulated with data. Typically, modulation symbols are sent in OFDM in the frequency domain and in SC-FDM in the time domain. Additionally and/or alternatively, the system bandwidth can be partitioned into one or more frequency carriers, each of which can contain one or more subcarriers. System 100 may also utilize a combination of multiple access schemes, e.g., a combination of OFDMA and CDMA. While the power control techniques provided herein are generally described for an OFDMA system, it should be appreciated that the techniques described herein may be equally applied to any wireless communication system.
According to one aspect, base station 110 and/or terminal 120 in system 100 can employ multiple (N) for data transmissionTMultiple) transmit antennas and/or multiple (N)RMultiple) receiving antennas. May be composed of NTA transmitting antenna and NRA MIMO channel formed by receiving antennas is decomposed into NSA separate channel, or NSThe individual channels are called spatial channels, where NS≤min{NT，NR}. In one example, NSEach of the individual channels may correspond to a dimension. By using a plurality of hairThe additional dimensionalities created by the transmit and receive antennas allow system 100 to achieve higher throughput, greater reliability, and/or other performance gains.
In another example, base stations 110 and/or terminals 120 in system 100 can communicate data using one or more data channels and signaling using one or more control channels. The data channels used by system 100 may be assigned to active terminals 120 such that each data channel is used by only one terminal at any given time. Alternatively, a data channel may be assigned to multiple terminals 120, and the multiple terminals 120 may be superimposed on or orthogonally scheduled on the data channel. Control channels used by system 100 can also be shared among multiple terminals 120 using, for example, code division multiplexing, in order to conserve system resources. In one example, data channels orthogonally multiplexed only in frequency and time (e.g., data channels not multiplexed using CDM) may be less susceptible to loss of orthogonality due to channel conditions and receiver imperfections than corresponding control channels.
According to one aspect, system 100 can employ centralized scheduling via one or more schedulers implemented at system controller 130 and/or each base station 110, for example. In a system using centralized scheduling, the scheduler may rely on feedback from the terminals 120 to make appropriate scheduling decisions. In one example, the feedback can include a delta offset added to the OSI information of the feedback to allow the scheduler to estimate the supportable reverse link peak rate for the terminal 120 that sent the feedback and allocate system bandwidth accordingly.
According to another aspect, system 100 can employ reverse link interference control to ensure minimum system stability and quality of service (QoS) parameters for the system. For example, the probability of decoding error for a Reverse Link (RL) acknowledgement message may result in an error floor (error floor) for all forward link transmissions. By using interference control on the RL, system 100 can facilitate power efficient transmission of control and QoS traffic and/or other traffic with stringent error requirements.
Fig. 2 is a block diagram of a system 200 that facilitates reverse link power control and interference management in a wireless communication system in accordance with various aspects described herein. In one example, the system 200 includes a terminal 2101Terminal 2101May be provided via at terminal 2101One or more antennas 216 at1And one or more antennas 224 at serving sector 220 communicate with serving sector 220 on the forward and reverse links. Serving sector 220 can be a base station (e.g., base station 110) or an antenna group at a base station. Further, serving sector 220 may provide coverage for a cell (e.g., cell 102) or an area within a cell (e.g., sector 104). Additionally, system 200 can include one or more neighboring sectors 230, terminals 2101No communication is made with neighboring sectors 230. Neighboring sector 230 may provide coverage via one or more antennas 234 for various geographic areas that may include all, part, or none of the area covered by serving sector 220. Although serving sector 220 and neighbor sector 230 are shown as separate entities in system 200, it should be appreciated that a terminal can employ different sectors for primary communication on the forward and reverse links. In this example, a single sector can be serving sector 220 on the forward link and neighbor sector 230 on the reverse link, and/or serving sector 220 on the reverse link and neighbor sector 230 on the forward link. Additionally, it is to be appreciated that terminal 210 can communicate traffic on the forward link or control on the forward link and/or reverse link with neighboring sector 230.
In accordance with one aspect, a terminal 210 and a serving sector 220 can communicate to control an amount of transmit power utilized by the terminal 210 to communicate with the serving sector 220 via one or more power control techniques. In one example, neighbor sector 230 can transmit OSI indicators from OSI indicator component 232 to terminal 210. Based on OSI indicators from neighboring sectors 230, terminal 210 can adjust one or more delta values via power control component 212 that are utilized to manage resources utilized for communication with serving sector 220 on a reverse link. In addition, terminal 210 can communicate the calculated delta value and/or a report of OSI activity caused by terminal 210 as feedback to serving sector 220. At serving sector 220, power control component 222 can then use feedback from terminal 210 to allocate transmit power and/or other resources for communication to terminal 210. After power control component 222 generates a transmit power assignment, serving sector 220 can transmit the assignment back to terminal 210. The terminal 210 can then adjust its transmit power accordingly based on the assignment via the power adjustment component 212.
According to another aspect, the power control techniques used by entities in system 200 can additionally take into account interference present in system 200. For example, in a multiple-access wireless communication system, such as an OFDMA system, multiple terminals 210 may concurrently uplink transmit by multiplexing their uplink transmissions orthogonally to one another in the time, frequency, and/or code domain. However, complete orthogonality between transmissions from different terminals 210 is typically not achieved due to channel conditions, receiver imperfections, and other factors. As a result, a terminal 210 in system 200 can generally cause interference to other terminals 210 communicating with the same sector 220 or 230. Moreover, because transmissions from terminals 210 communicating with different sectors 220 and/or 230 are typically not orthogonal to one another, each terminal 210 can also cause interference to terminals 210 communicating with neighboring sectors 220 and/or 230. As a result, the performance of the terminals 210 in the system 200 may be degraded by interference caused by other terminals 210 in the system 200.
Fig. 3A-3B are block diagrams illustrating operation of an example system 300 for power control and interference management in a wireless communication system. In a manner similar to system 200, system 300 can include a terminal 310 in communication with a serving sector 320 on the forward and reverse links via respective antennas 316 and 324. System 300 can also include one or more neighboring sectors (e.g., neighboring sector 230) that can include dominant interference sector 330, e.g., dominant interference sector 330 is most likely to be affected by interference caused by terminal 310 due to being the neighboring sector closest to terminal 310.
In accordance with one aspect, terminal 310 can communicate with serving sector 320 to control a transmit power level utilized by terminal 310. In one example, the power control techniques employed by terminal 310 and serving sector 320 can be based on a level of interference caused by terminal 310 at serving sector 320 and/or other sectors, such as dominant interference sector 330. By using interference as a factor in the power control techniques employed by terminals 310 and serving sectors 320, the techniques may achieve better overall performance of system 300 than similar techniques that do not consider interference.
Referring to fig. 3A, reverse link transmissions 318 from a terminal 310 to a serving sector 320 are illustrated. In accordance with one aspect, entities in system 300 can employ one or more reverse link traffic channel power control techniques to control an amount of resources utilized by terminal 310 for reverse link transmissions, and thus control an amount of interference caused by terminal 310 at non-serving sectors, such as dominant interference sector 330. By using these techniques, terminal 310 can be allowed to transmit at an appropriate power level while keeping inter-sector interference within an acceptable level. In one such technique, dominant interference sector 330 can broadcast information to terminals 310 regarding the interference level it observes. Terminal 310 can adjust its transmit power based on the information, its current transmit power, and a channel strength measurement between terminal 310 and a non-serving sector, such as dominant interference sector 330.
In accordance with another aspect, dominant interference sector 330 can transmit interference indicators, OSI indications 338, and/or other signaling to access terminal 310 on the forward link via an Other Sector Interference (OSI) indicator component 332 and one or more antennas 334. For example, the interference indicator generated by OSI indicator component 332 can comprise an indication of reverse link interference present at dominant interference sector 330. In one example, OSI indication 338 generated by OSI indicator component 332 can be a regular OSI indication 336 carried on a forward link physical channel (e.g., F-OSICH). In another example, the channels can be given a large coverage area to facilitate decoding of the indication at terminals not served by dominant interference sector 330. More specifically, the channel used by dominant interference sector 330 can have a coverage area similar to the channel used to transmit the acquisition pilot, which can extend deep into neighboring sectors in system 300. In another example, regular OSI indications 336 transmitted by dominant interference sector 330 can be made decodable without requiring additional information about dominant interference sector 330 beyond the sector pilot. Due to these requirements, the rate of regular OSI indications 336 can be limited to, for example, one transmission per superframe to account for the power and time-frequency resources required for these indications.
For many applications where system 300 is fully loaded, transmitting OSI indications may be sufficient to control interference in system 300 and/or provide acceptable control over interference present in system 300. However, in some cases, a faster power control mechanism may be required. An example of this is the case for a partially loaded system, where a single terminal 310 located near the boundary of two sectors suddenly starts a new transmission after being silent for a long time and causes a significant amount of interference to reverse link transmissions currently present in neighboring sectors. Using a slow OSI indication on the F-OSICH, a neighboring sector may take several superframes to force the terminal to reduce its transmit power to an acceptable level. During this time, reverse link transmissions in neighboring sectors may suffer from severe interference and experience a large number of packet errors.
According to one aspect, it is appreciated that long-term channel quality on the forward and reverse links is typically highly correlated. Thus, a terminal that is causing strong interference to a non-serving sector on the reverse link will likely observe a strong signal (e.g., pilot) from that sector on the forward link and add that sector to its active set. Thus, according to one aspect, in addition to regular transmissions over F-OSICH, sectors such as dominant interfering sector 330 can additionally transmit fast OSI indications 337 on a lower overhead forward link control channel (e.g., fast forward link OSI channel, F-FOSICH) to terminals 310 that added dominant interfering sector 330 to their active set. Since fast OSI indications 337 are intended for more stringent groups of terminals (e.g., terminals having dominant interference sector 330 in their active set), the coverage requirements for this segment are not as large as F-OSICH. In this case, F-FOSICH may occur in each FL PHY frame, which allows a sector to more quickly suppress interference from terminals in neighboring sectors before the interference from terminals in neighboring sectors causes packet errors in the current sector.
According to another aspect, OSI indicator component 332 can utilize a metric based upon an amount of interference it observes on different time-frequency resources to generate OSI indications 336 and/or 337. In one example, OSI indicator component 332 can utilize an average interference over all frequency resources and over a number of recent reverse link frames as a metric for generating OSI indications 336 and/or 337. For example, OSI indicator component 332 can utilize a regular OSI channel, F-OSICH, to control average interference by generating a regular OSI indication 336 based on a long-term average (e.g., a filtered version) of the average interference measured over all frequency resources, and OSI indicator component 332 can utilize a fast OSI channel (F-FOSICH) to control a tail of the interference distribution by generating a fast OSI indication 337 based on a short-term average of the interference measurements. Additionally and/or alternatively, OSI indicator component 332 can utilize a function of measured interference over different time-frequency resources to generate OSI indications 336 and/or 337. Further, a combination of the average and maximum interference measured over different time-frequency blocks of the most recent reverse link frame can be used to generate fast OSI indications 337.
OSI indicator component 332 can communicate OSI indications 336 and/or 337 to terminal 310 in a variety of ways. As a non-limiting example, OSI indicator component 332 can provide interference information using a single OSI bit. More specifically, OSI bits (OSIB) can be set as follows:
wherein the IOTmeas，m(n) is an interference-over-thermal (IOT) value measured for the m-th sector at time interval n, and IOTtargetIs the desired operating point for the mth sector. As used in equation (1), IOT refers to the ratio of the total interference power observed by the access point to the thermal noise power. Based on this, a specific operating point may be selected for the system and denoted IOTtarget. In one example, OSI can be quantized to multiple levels and accordingly contain multiple bits. For example, an OSI indication can have, for example, IOTMINAnd IOTMAXSuch that if the observed IOT is at IOTMINAnd IOTMAXIn between, no transmit power adjustment at terminal 310 is made. However, if the observed IOT is above or below a given level, then the transmit power should be adjusted up or down accordingly.
In system 300, terminal 310 can adjust resources for subsequent reverse link transmissions via power adjustment component 312 upon terminal 310 receiving OSI indications 336 and/or 337 from dominant interference sector 330 as illustrated in fig. 3A, and/or terminal 310 can provide feedback to serving sector 320 based upon received OSI indications via feedback component 318 as illustrated in fig. 3B. In one example, as illustrated in fig. 3A, terminal 310 can include a delta computation component 314 that can be configured to compute one or more delta offset values based upon OSI indications received by terminal 310.
In accordance with one aspect, a power adjustment component at terminal 310 can maintain a reference power level or Power Spectral Density (PSD) level and can add an appropriate offset value (in dB) to the reference levelThe transmit power or PSD used by terminal 310 on the traffic channel is calculated. In one example, the offset can be a delta value maintained by delta calculation component 314. In a particular example, delta computation component 314 can maintain a single delta value that can be adjusted based on regular and/or fast OSI indications. Alternatively, delta computation component 314 can maintain two delta values, wherein a first delta can be based upon a slow OSI indication and can be employed as a maximum value for a second delta, and wherein the second delta can be adjusted based upon a fast OSI indication and can be employed for access terminal transmissions. In another example, access terminal 310 can maintain multiple delta values Δ for a fast methodtxAnd uses the slow OSI indicator as a pair of deltastxThe maximum value at which the value is adjusted. Each fast delta value can then be adjusted based on OSI indications.
In another example, terminal 310 can maintain a slow delta value and provide the slow delta value to serving sector 320 via feedback component 318. In this example, terminal 310 can maintain a delta based on fast OSI indicationstxThe value is obtained. More specifically, terminal 310 may set the maximum and minimum values based on traffic flow parameters such that each Δ is independent of the slow Δ valuestxWith maximum upward and downward adjustment. The terminal 310 may then maintain a delta value between the maximum indication and the minimum indication. Based on these delta values, feedback component 318 can feed back a slow delta value for future allocations and/or a delta valuetxThe value is used for future allocations. Where more than one fast delta value is maintained at access terminal 310, each delta value can correspond to a different reverse link interlace.
Power adjustment component 312 can be connected to delta computation component 314 via a wired connection and/or a wireless connection. In one example, power adjustment component 312 prevents fast delta adjustments from interfering with regular delta-based power control operations by limiting the range of fast delta values as described above to slow delta values. In the event that signal distortion caused by the physical channel results in a lack of orthogonality and thus intra-sector interference, power adjustment component 312 can also take into account requirements for the received signal dynamic range and limit the minimum and maximum delta values accordingly. Further, power adjustment component 312 can adjust the minimum and/or maximum delta values based upon information related to interference levels broadcast from serving sector 320.
It is to be appreciated that while delta computation component 314 is illustrated in fig. 3B as a component of terminal 310, serving sector 320 and/or another suitable network entity can perform some or all of the computations performed by delta computation component 314 independently of terminal 310 or in cooperation with terminal 310.
As a specific, non-limiting example, delta computation component 314 and/or power adjustment component 312 can monitor OSI bits broadcast by neighboring access points in system 300 and can be configured to respond only to OSI bits of dominant interference sector 330, dominant interference sector 330 can have a minimum channel gain ratio among multiple neighboring access points. In one example, if the OSI bit for dominant interference sector 330 is set to "1" due to access point 310 observing higher than nominal inter-sector interference, for example, delta computation component 314 and/or power adjustment component 312 can adjust the transmit power of terminal 310 downward accordingly. Conversely, if the OSI bit for dominant interference sector 330 is set to "0," delta computation component 314 and/or power adjustment component 312 can adjust the transmit power of terminal 310 upward. Further, delta computation component 314 and/or power adjustment component 312 can then determine a magnitude of the transmit power adjustment for terminal 310 based on the current transmit power level and/or the transmit power delta for terminal 310, the channel gain ratio for dominant interference sector 330, and/or other factors. Alternatively, delta computation component 314 and/or power adjustment component 312 can utilize OSI bits from more than one access point 330 and can employ various algorithms to adjust the maximum allowable transmit power for terminal 310 based upon the multiple received OSI bits.
According to another aspect, terminal 310 can include a feedback component 318, and feedback component 318 can transmit to serving sector 320 the transmit PSD Δ, Δ computed by power adjustment component 312,One or more delta values computed by delta computation component 314 and/or a maximum number of subcarriers or subbands N that terminal 310 can support at a current transmit PSD deltasb，max(n) of (a). In addition, feedback component 318 can also send desired quality of service (QoS) and buffer size parameters to serving sector 320. To reduce the amount of signaling required, feedback component 318 can send Δ p (N) and N on the data channel via in-band signaling and/or otherwise over a subset of the update time intervalsb，max(n) of (a). It should be appreciated that a low transmit PSD delta for terminal 310 does not mean that terminal 310 is not using all of the resources available to it. Rather, terminal 310 can be given more subcarriers or subbands for transmission in order to utilize all of the available transmit power for terminal 310.
According to another aspect, terminal 310 can employ a metric, referred to as ChanDiff, for each identifiable sector in system 300, which is an estimate of the difference between the reverse link channel quality of an identifiable sector and the reverse link channel quality of serving sector 320 to determine whether to respond to OSI indications from the serving sector. In one example, ChanDiff values can be computed using forward link acquisition pilots. Additionally and/or alternatively, ChanDiff values can be computed based on reverse link pilot metric indications carried on a forward link pilot quality indicator channel (e.g., F-PQICH). In another example, terminal 310 can respond to fast OSI indications only from sectors whose forward link channel strength is within an interval around that of serving sector 310. The standard may ensure a reasonable reliability of fast OSI indications and pilot quality indications received from those sectors. Further, it can be appreciated that terminal 310 is most likely to cause significant interference to only the sector.
Terminal 310 can then use the ChanDiff quantity with a measure of the current transmit power of terminal 310 (e.g., total transmit power or PSD offset (e.g., delta value) from a reference PSD) via delta computation component 314 and/or other suitable components to determine a distribution from which to derive a decision variable corresponding to the sector and/or a weight value for the corresponding decision variable. Based on the decision variable, the terminal 310 can determine whether to increase or decrease its delta value.
In addition, terminal 310 can use similar algorithms with similar parameters for slow and fast delta adjustments. Alternatively, the terminal 310 may use different algorithms and/or different sets of parameters to adjust for different delta values. Examples of parameters that may be different for slow and fast delta adjustments are up and down step sizes and different decision thresholds. In addition, similar information can be incorporated into PSD constraints or related channel/interference feedback utilized by terminal 310 and/or serving sector 320. For example, delta settings in a delta-based power control algorithm used by system 300 can be modified to reflect a maximum per-user interference target.
Referring to fig. 4-5, methodologies for power and interference control in a wireless communication system are illustrated. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with one or more embodiments.
Referring to fig. 4, illustrated is a methodology 400 for providing reverse link feedback for power control and interference management in a wireless communication system (e.g., system 300). It should be appreciated that methodology 400 can be implemented, for example, by a terminal (e.g., terminal 310) and/or any other suitable network entity. Methodology 400 begins at block 402, one or more OSI indications are received from a neighboring access point (e.g., dominant interference sector 330).
In one example, OSI indications received at block 402 can be generated based on a metric that takes into account an amount of interference observed by the neighboring access point on different time-frequency resources. An example of a metric for this purpose is the average interference over a number of recent reverse link frames and over the entire frequency resource. For example, a neighboring access point can use a regular OSI channel, F-OSICH, to control average interference by generating OSI indications based on a long-term average of measured interference over all frequency resources, and a fast OSI channel (F-OSICH) to control the tail of the interference distribution by generating fast OSI indications based on a short-term average of interference measurements. In general, to generate OSI indications, neighboring access points can use a function of interference measured over different time-frequency resources. An example of such a function that may be used to generate fast OSI indications is a combination of average and maximum interference measured over different time-frequency blocks of a recent reverse link frame.
Next, at block 404, one or more delta values can be adjusted based on the OSI indications received at block 402. In one example, a single delta value can be maintained based on regular and/or fast OSI indications. In another example, two delta values can be maintained, where the first delta is maintained based on slow OSI indications and is taken as the maximum of the second delta, which is maintained based on fast OSI indications. In another example, to prevent fast delta adjustments from interfering with conventional delta-based power control operations, the range of fast delta values as calculated at block 404 may be limited to slow delta values. In the event that signal distortion caused by the physical channel results in loss of orthogonality and thus intra-sector interference, the adjustment at block 404 may also take into account the requirements on the dynamic range of the received signal and limit the minimum and maximum delta values accordingly. The minimum and maximum delta values may then be additionally adjusted based on interference information received from the serving access point.
Upon completing the actions described at block 404, the method 400 may end or may optionally proceed to block 406 where the reverse link communication resources for communicating with the serving access point may be adjusted based on the delta value calculated at block 404. In a particular example, the adjustment at block 406 can be based on the slow delta value and the fast delta value calculated at block 404, where the fast delta value is used for the adjustment and the slow delta value is taken as the maximum of the fast delta value.
Upon completion of the optional actions described at block 406, the method 400 may end or may optionally proceed to block 408 before ending. At block 408, one or more delta values may be communicated to the serving access point. After completing the acts described at blocks 404 and/or 406, the method may additionally optionally continue to block 408, where one or more delta values are communicated to the serving access point. In one example, at block 408, a plurality of delta values can be maintained and transmitted to the serving access point. Additionally, at block 408, a report of the OSI indication received at block 402 can be communicated with the delta value. In another example, only a slow delta can be maintained at block 404, which can be communicated to the serving access point for assignment at block 408. Additionally and/or alternatively, one or more fast delta values can additionally be maintained at block 404 and communicated to the serving access point at block 408. Where more than one fast delta value is maintained at block 404, each delta value can correspond to a different reverse link interlace.
Fig. 5 illustrates a methodology 500 for reverse link power control in a wireless communication system. It should be appreciated that method 500 may be implemented, for example, by a terminal and/or any other suitable network entity. The methodology 500 begins at block 502, and at block 502, an OSI indication is received from a neighbor sector. For example, OSI indications received at block 502 can be fast OSI indications, slow OSI indications, and/or other suitable indications.
Next, at block 504, a channel quality difference between the neighboring sector and the serving sector may be calculated. In one example, a metric known as ChanDiff, which is an estimate of the difference between the reverse link channel quality of the neighbor sector and the reverse link channel quality of the serving sector, can be used for the neighbor sectors to determine whether to respond to OSI indications from the neighbor sectors. In another example, ChanDiff values can be computed using forward link acquisition pilots. Alternatively, ChanDiff values can be computed based on reverse link pilot metric indications, which can be carried on a forward link pilot quality indicator channel (e.g., F-PQICH).
Upon completing the actions described at block 504, method 500 proceeds to block 506 where a decision is made at block 506 whether to respond to the OSI indication based at least in part on the difference in channel quality. In one example, a decision may be made at block 506 to respond to fast OSI indications only from those sectors that meet the following condition: the forward link channel strengths of those sectors are within a close interval of the forward link channel strengths of their reverse link serving sectors. The standard may ensure a reasonable reliability of fast OSI indications and pilot metric indications received from those sectors.
Methodology 500 can then conclude at block 508, and at block 508, one or more delta values can be adjusted based on the received OSI indications and one or more weighted decision variables, which can be determined based at least in part on the channel quality differences found at block 506. According to one aspect, if a delta value is used for data transmission on a previous interlace, the delta value may be adjusted at block 508. In addition, delta values can be adjusted at block 508 in response to corresponding OSI values obtained at block 502. Alternatively, delta adjustments may be made at block 508 at any time including silent periods and unassigned interlaces. The adjustment decision may also be based on the buffer size. For example, the delta value may be adjusted for all interlaces at block 508 only when there is a non-zero buffer size.
According to another aspect, the ChanDiff quantity can be used with current transmit power measurements, such as total transmit power or PSD offset from a reference PSD, to determine a distribution from which to derive decision variables corresponding to sectors and/or weights for the respective decision variables. The delta value may be increased or decreased at block 508 based on a metric that may be a function of the weighted decision variables. Further, similar algorithms with similar parameter sets may be used for slow and fast delta adjustments at block 508. Alternatively, different algorithms or different sets of parameters may be used to adjust different delta values.
Referring now to fig. 6, a block diagram illustrating an exemplary wireless communication system 600 is provided, and one or more embodiments described herein may be used in system 600. In one example, system 600 is a multiple-input multiple-output (MIMO) system that includes a transmitter system 610 and a receiver system 650. It should be appreciated, however, that transmitter system 610 and/or receiver system 650 can also be applied to a multiple-input single-output system, wherein, for example, multiple transmit antennas (e.g., at a base station) can transmit one or more symbol streams to a single antenna device (e.g., a mobile station). Additionally, it should be appreciated that various aspects of transmitter system 610 and/or receiver system 650 described herein may be used in conjunction with a single-output, single-input antenna system.
In accordance with one aspect, at transmitter system 610, traffic data for a number of data streams is provided from a data source 612 to Transmit (TX) data processor 614. In one example, each data stream can then be transmitted via a respective transmit antenna 624. Additionally, tx data processor 614 may format, encode, and interleave traffic data for each data stream based on a particular coding scheme selected for the respective data stream in order to provide coded data. In one example, the coded data for each data stream can then be multiplexed with pilot data using OFDM techniques. For example, the pilot data may be a known data pattern that is processed in a known manner. In addition, the pilot data can be used at receiver system 650 to estimate channel response. Returning to transmitter system 610, the multiplexed pilot and coded data for each data stream can be modulated (i.e., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. In one example, the data rate, coding, and modulation for each data stream can be determined by instructions performed on processor 630 and/or provided by processor 630.
Next, modulation symbols for all data streams can be provided to a transmit processor 620, and transmit processor 620 can further process the modulation symbols (e.g., for OFDM). The TXMIMO processor 620 can then assign N to the data streamTOne modulation symbol stream is provided to NTAnd transceivers (TMTR/RCVR)622a through 622 t. In one example, each transceiver 622 can receive and process a respective symbol stream to provide one or more analog signals. Each transceiver 622 may then further process (e.g., amplify, filter, and upconvert) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Thus, N from transceivers 622a through 622t may then be combinedTEach modulated signal being from NTThe antennas 624a through 624t transmit.
According to another aspect, N may be defined at receiver system 650RThe transmitted modulated signals are received by antennas 652a to 652 r. The received signal from each antenna 652 may then be provided to a respective transceiver (RCVR/TMTR) 654. In one example, each transceiver 654 can process (e.g., filter, amplify, and downconvert) a respective received signal, digitize the processed signal to provide samples, and then processes the samples to provide a corresponding "received" symbol stream. RX MIMO/data processor 660 may then pair the signals from N based on a particular receiver processing techniqueRN of a transceiver 654RA stream of received symbols is received and processed to provide NTA "detected" symbol stream. In one example, each detected symbol stream can comprise a plurality of symbols that are estimates of the modulation symbols transmitted for the corresponding data stream. Receive processor 660 can then perform symbol estimation at least in part by demodulating each detected symbol stream,Deinterleaves and decodes to process each symbol stream to recover the traffic data for the corresponding data stream. Thus, the processing by rx data processor 660 is complementary to that of TX MIMO processor 620 and TX data processor 614 at transmitter system 610. Receive processor 660 may additionally provide processed symbol streams to a data sink 664.
In accordance with one aspect, the channel response estimate generated by receive processor 660 can be used for spatial/temporal processing at the receiver, for adjustments to power levels, for changes in modulation rate or scheme, and/or for other suitable actions. In addition, receive processor 660 may further estimate channel characteristics such as signal-to-noise-and-interference ratios (SNRs) of the detected symbol streams. Receive processor 660 may then provide estimated channel characteristics to a processor 670. In one example, receive processor 660 and/or processor 670 can further derive an estimate of the "operating" SNR for the system. Processor 670 can then provide Channel State Information (CSI), which can comprise information regarding the communication link and/or the received data stream. For example, the information may include an operating SNR. The CSI can then be processed by a tx data processor 618, modulated by a modulator 680, processed by transceivers 654a through 654r, and transmitted back to transmitter system 610. Additionally, a data source 616 at receiver system 650 can provide additional data, which is processed by transmit data processor 618.
Returning to transmitter system 610, the modulated signals from receiver system 650 may then be received by antennas 624, conditioned by transceivers 622, demodulated by a demodulator 640, and processed by a rx data processor 642 to recover the CSI reported by receiver system 650. In one example, the reported CSI can then be provided to processor 630 and used to determine data rates and coding and modulation schemes to be used for one or more data streams. The determined coding and modulation schemes can then be provided to transmitter 622 for quantization and/or use in later transmissions to receiver system 650. Additionally and/or alternatively, processor 630 may use the reported CSI to generate various controls for TX data processor 614 and TX MIMO processor 620. In another example, CSI and/or other information processed by rx data processor 642 can be provided to a data sink 644.
In one example, processor 630 at transmitter system 610 and processor 670 at receiver system 650 direct operation on their respective systems. Additionally, memory 632 at transmitter system 610 and memory 672 at receiver system 650 can provide storage for program codes and data used by processors 630 and 670, respectively. Further, at receiver system 650, various processing techniques can be used for NRProcessing the received signals to obtain NTOne transmitted symbol stream is detected. These receiver processing techniques may include spatial and space-time receiver processing techniques, which may also be referred to as equalization techniques, and/or "successive nulling/equalization and interference cancellation" receiver processing techniques, which may also be referred to as "successive interference cancellation" or "successive cancellation" receiver processing techniques.
Fig. 7 is a block diagram of a system 700 that coordinates maintenance of reverse link power levels in a wireless communication system in accordance with various aspects described herein. In one example, system 700 includes an access terminal 702. As shown, access terminal 702 can receive signal(s) from one or more access points 704 and transmit signal(s) to the one or more access points 704 via antenna 708. Additionally, access terminal 702 can comprise a receiver 710 that receives information from antenna 708. In one example, receiver 710 can be operatively associated with a demodulator (Demod)712 that demodulates received information. Demodulated symbols can then be analyzed by a processor 714. Processor 714 can be coupled to memory 716, which memory 716 can store data and/or program codes related to access terminal 702. Additionally, access terminal 702 can employ processor 714 to perform methodologies 400, 500, and/or other suitable methodologies. Access terminal 702 can also include a modulator 718, modulator 718 that multiplexes signals for transmission by a transmitter 720 via antenna 708 to one or more access points 704.
Fig. 8 is a block diagram of a system 800 that coordinates reverse link power control and interference management in a wireless communication system in accordance with various aspects described herein. In one example, system 800 includes a base station or access point 802. As shown, access point 802 can receive signal(s) from one or more access terminals 804 via a receive (Rx) antenna 806 and transmit signal(s) to the one or more access terminals 804 via a transmit (Tx) antenna 808.
In addition, access point 802 can comprise a receiver 810 that receives information from receive antenna 806. In one example, the receiver 810 can be operatively associated with a demodulator (Demod)812 that demodulates received information. Demodulated symbols can then be analyzed by a processor 814. Processor 814 can be coupled to a memory 816 that can store information related to code clusters, access terminal assignments, lookup tables associated therewith, unique scrambling sequences, and/or other appropriate types of information. Access point 802 can further comprise a modulator 818 that can multiplex the signal for transmission by a transmitter 820 via transmit antennas 808 to one or more access terminals 804.
Fig. 9 illustrates an apparatus 900 that facilitates reverse link transmission resource adjustment and interference management in a wireless communication system. It is to be appreciated that apparatus 900 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). Apparatus 900 can be implemented in a terminal (e.g., terminal 310) and/or another suitable network entity of a wireless communication system, and apparatus 900 can include a module 902 for receiving a slow OSI indication and/or a fast OSI indication from a neighbor sector. Apparatus 900 can further comprise a module for adjusting one or more delta values based upon received OSI indications 904, and a module for adjusting reverse link communication resources based upon delta values and/or communicating delta values to a serving sector 906.
Fig. 10 illustrates an apparatus 1000 that facilitates adjusting reverse link transmissions based upon received interference indications in a wireless communication system. It is to be appreciated that apparatus 1000 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). Apparatus 1000 can be implemented in a terminal and/or another suitable network entity of a wireless communication system, and apparatus 1000 can include a module 1002 for receiving OSI indications from neighboring sectors. Moreover, apparatus 1000 can comprise a module 1004 for calculating a channel quality difference between a neighbor sector and a serving sector, a module 1006 for determining whether to respond to OSI indications based at least in part on the channel quality difference, and a module 1008 for adjusting one or more delta values based on received OSI indications and one or more weighted decision variables determined based at least in part on the channel quality difference.
It is to be understood that the embodiments described herein may be implemented by hardware, software, firmware, middleware, microcode, or a combination thereof. When the systems and/or methods are implemented in software, firmware, middleware or microcode, program code or code segments, they can be stored in a machine-readable medium, such as a storage component. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program declarations. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted using any suitable means including memory sharing, message passing, token passing, network transmission, etc.
For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.
What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim. Furthermore, the word "or" as used in either the detailed description or the claims means "or, but not mutually exclusive.