CN101578775B - Method and apparatus for utilizing other sector interference (OSI) indication - Google Patents

Abstract

This invention describes techniques for reducing interference in wireless communication systems. In one design, a sector determines multiple Fast Other Sector Interference (OSI) indicators for multiple sub-regions, each sub-region corresponding to a different portion of the system bandwidth. At least one report is generated for the multiple OSI indicators, each report including at least one OSI indicator for at least one sub-region. Each report is encoded to obtain coded bits, which are then mapped to a modulation symbol sequence. For each report, a sequence of modulation symbols with zero values is generated to indicate that there is no strong interference in the corresponding sub-region, all OSI indicators in the report are set to zero. This allows reports to be transmitted at zero power in possible schemes. Alternatively, a regular OSI indicator can be determined for the system bandwidth and transmitted.

Description

Methods and apparatus using other sector interference (OSI) indications

This application claims U.S. Provisional Patent Application No. 60/883,387, filed January 4, 2007, entitled "A METHOD ANDAPPARATUS FOR FAST OTHER SECTOR INTERFERENCE (OSI) ADJUSTMENT," and filed January 5, 2007, entitled Priority to U.S. Provisional Patent Application No. 60/883,758 for "WIRELESS COMMUNICATION SYSTEM," both assigned to the applicant's assignee, is incorporated herein by reference.

technical field

In general, the present invention relates to communication, and in particular, the present invention relates to techniques for reducing interference in wireless communication systems.

Background technique

Wireless communication systems are widely deployed to provide various types of communication services such as voice, video, packet data, messaging, broadcasting, and the like. These wireless systems may be multiple-access systems capable of supporting communication for multiple users by sharing available system resources. Examples of such multiple access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single Carrier FDMA (SC-FDMA) system etc.

A wireless multiple-access communication system is capable of communicating with multiple terminals on the forward and reverse links simultaneously. The forward link (or downlink) refers to the communication link from the base station to the terminal, and the reverse link (or uplink) refers to the communication link from the terminal to the base station. Multiple terminals may transmit data on the reverse link and/or receive data on the forward link concurrently. This can be achieved by multiplexing on each link transmissions that are mutually orthogonal in the time, frequency and/or code domains.

On the reverse link, transmissions from terminals communicating with different base stations are generally not mutually orthogonal. Thus, each terminal can cause interference to other terminals communicating with neighboring base stations, and also receives interference from these other terminals. The performance of each base station is degraded due to interference from other terminals communicating with other base stations.

There is therefore a need in the art for techniques to reduce interference in wireless communication systems.

Contents of the invention

This document describes techniques for reducing interference in wireless communication systems. In one aspect, a sector estimates its observed inter-sector interference from terminals communicating with neighboring sectors. The sector generates and transmits an Other Sector Interference (OSI) Indication expressing the amount of interference observed by the sector. In one design, the OSI indications include regular OSI indications and fast OSI indications. Conventional OSI indications are generated from the long-term average interference obtained by computing the average of the interference over a large frequency range and over a long time interval. The fast OSI indication is generated from the short-term average interference obtained by computing the average of the interference over a small frequency range and over a short time interval. The terminal adjusts its transmit power according to the regular OSI indications and fast OSI indications received from neighboring sectors.

In one design, a sector determines multiple fast OSI indications for multiple subregions, each subregion corresponding to a different portion of the system bandwidth. At least one report is generated for fast OSI indications, each report including at least one fast OSI indication for at least one sub-area. Each report is encoded to obtain coded bits, which are then mapped to a sequence of modulation symbols. A zero-valued modulation symbol sequence is generated for each report for which all fast OSI indications are set to zero to indicate that there is no strong interference in the corresponding sub-region. This allows reporting to be sent with zero power in possible scenarios. And also determine and send conventional OSI indications.

In one design, the terminal receives at least one fast OSI indication for at least one subarea, and determines its transmit power based on the at least one fast OSI indication. At least one delta is saved for at least one sub-region, and the at least one delta is adjusted according to at least one fast OSI indication. The transmit power for a reference (eg, pilot) channel may be determined based on closed-loop power control. Then, the transmit power of each sub-area is determined based on the increment of the sub-area and the transmit power of the reference channel.

Various aspects and features of the invention are described in detail below.

Description of drawings

Figure 1 shows a wireless communication system.

Figure 2 shows the superframe structure.

Figure 3 shows the power control mechanism.

Figure 4 shows the process of sending an OSI indication.

Fig. 5 shows an apparatus for sending an OSI indication.

Figure 6 shows the process of receiving an OSI indication.

Fig. 7 shows an apparatus for receiving an OSI indication.

Figure 8 shows a block diagram of a terminal and two sectors/base stations.

Detailed ways

Figure 1 shows a wireless communication system 100, which may also be referred to as an access network (AN). The terms "system" and "network" are often used interchangeably. System 100 includes multiple base stations 110 , 112 and 114 and multiple terminals 120 . A base station is a radio station that communicates with terminals. A base station may also be called an access point, Node B, eNode B, or the like. Each base station provides communication coverage for a particular geographic area 102 . The term "cell" can refer to a base station and/or its coverage area depending on the context in which it is used. In order to improve the system capacity, the base station coverage area is divided into multiple smaller areas, for example, three smaller areas 104a, 104b and 104c. Each smaller area is served by its own base station subsystem. The term "sector" can refer to the smallest coverage area of a base station and/or a base station subsystem serving this coverage area.

Terminals 120 may be dispersed throughout the system and each terminal may be stationary or mobile. A terminal may also be called an access terminal (AT), mobile station, user equipment, subscriber unit, radio, and so on. A terminal may be a cellular telephone, a personal digital assistant (PDA), a wireless communication device, a wireless modem, a handheld device, a laptop computer, a cordless telephone, and the like. At any given moment, a terminal may communicate with zero, one or more base stations on the forward and/or reverse links.

For a centralized architecture, a system controller 130 couples to base stations 110 and provides coordination and control for these base stations. System controller 130 may be a single network entity or a collection of multiple network entities. For a distributed architecture, base stations communicate with each other as needed.

The techniques described herein can be used in systems with sectorized cells and can be used in systems with unsectorized cells. For clarity, a system with sectorized cells is described below. In the following description, the terms "sector" and "base station" are used interchangeably, and the terms "terminal" and "user" are also used interchangeably. A serving sector is a sector with which a terminal communicates. Neighboring sectors are sectors with which the terminal does not communicate.

The techniques described herein may be used in various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA systems. A CDMA system may implement a radio technology such as cdma2000, Universal Terrestrial Radio Access (UTRA), and others. The OFDMA system can implement such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE802.20, and other wireless technologies. UTRA and E-UTRA are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). cdma2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). These various wireless technologies and standards are well known in the art. For clarity, certain aspects of the techniques are described below for UMB, and UMB terminology is used in various places in the description that follows. UMB is described in the standards named "Physical Layer for Ultra Mobile Broadband (UMB) Air Interface Specification" in 3GPP2C.S0084-001 and "Medium Access Control Layer For Ultra Mobile Broadband (UMB) Air Interface Specification" in 3GPP2C.S0084-002 , both standards were published in August 2007 and are publicly available.

System 100 may employ Orthogonal Frequency Division Multiplexing (OFDM) and/or Single Carrier Frequency Division Multiplexing (SC-FDM). OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal sub-carriers, where the orthogonal sub-carriers are often called tones, frequency points, etc. Each subcarrier is modulated with data. In general, modulation symbols are sent in the frequency domain using OFDM and in the time domain using SC-FDM. The interval between adjacent subcarriers is fixed, and the number of subcarriers depends on the system bandwidth. For example, a system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz has 128, 256, 512, 1024 or 2048 subcarriers, respectively.

FIG. 2 shows a design of a superframe structure 200 that may be used in system 100 . Divide the transmission timeline of each link into units of superframes. Each superframe spans a specific time period, which can be fixed or configurable. On the forward link, each superframe includes a preamble followed by M physical layer (PHY) frames, where M can be any integer value. On the reverse link, each superframe includes M PHY frames, where the first PHY frame is extended by the length of the superframe preamble on the forward link. In the design shown in FIG. 2, each superframe includes 25 PHY frames, indexed 0-24. Each PHY frame can carry service data, signaling, pilot frequency, etc.

In one design, the superframe preamble includes 8 OFDM symbols, indexed 0-7. OFDM symbol 0 includes a forward primary broadcast control channel (F-PBCCH) carrying deployment-specific parameter information. OFDM symbols 1 to 4 include a Forward Supplementary Broadcast Control Channel (F-SBCCH) carrying sector-specific parameter information and a Forward Quick Paging Channel (F-QPCH) carrying paging information. OFDM symbols 5, 6, and 7 include time division multiplexed (TDM) pilots 1, 2, and 3, respectively, used by the terminal for initial acquisition. TDM Pilot 1 is used as a forward acquisition channel (F-ACQCH). The Forward Other Sector Interference Channel (F-OSICH) is transmitted in TDM pilots 2 and 3. The superframe preamble can also be defined in other ways.

The system supports Hybrid Automatic Repeat (HARQ). Using HARQ, one or more transmissions may be sent for a packet until the packet is decoded correctly or the transmission is terminated by some other condition. Multiple (Q) HARQ interlaces are defined, and HARQ interlace i includes PHY frame i, Q+1, 2Q+i, etc., where i∈{0,...,Q-1}. Each packet is sent on one HARQ interlace, and one or more HARQ transmissions may be sent for the packet on that HARQ interlace. A HARQ transmission is the transmission of one packet in one PHY frame.

Multiple (S) sub-regions may be defined, each sub-region corresponding to a different portion of the system bandwidth. A sub-region may also be called a sub-band, a frequency band, or the like. In general, a sub-region corresponds to a physical frequency resource (eg, a subcarrier) or a logical frequency resource (eg, a hop port) mapped to a physical frequency resource. In one design, K hop ports are defined and mapped to K total subcarriers according to a known mapping relationship. Port hopping simplifies the allocation of resources. The K hop ports are arranged into S subareas, each subarea includes L hop ports, where L and S may be fixed or configurable values. For example, L can be equal to 64 or 128, and S depends on the system bandwidth.

Figure 2 shows a specific frame structure design. Other frame structures may also be used to transmit service data, signaling, pilots, etc. The system bandwidth may also be divided in other ways.

Each sector may receive transmissions from terminals in that sector as well as transmissions from terminals in other sectors. The total interference observed by each sector includes: (i) intra-sector interference from terminals in the same sector and (ii) inter-sector interference from terminals in other sectors. Inter-sector interference is also known as other-sector interference (OSI) and is reduced as described below.

In one aspect, each sector determines and transmits an OSI indication representing the amount of interference observed by that sector. OSI indications may also be referred to as OSI values, OSI indicators, interference indicators, and the like. In one design, each sector may generate and send the OSI indications shown in Table 1.

Table 1

For clarity, the generation of an OSI indication for a sector 112 is described below. Sector 112 estimates the interference of different time-frequency resources observed by the sector. The interference may be quantified by interference over thermal (IoT) or some other value. IoT is the ratio of the total interference power observed by the sector to the thermal noise power. Sector 112 averages the interference over the entire system bandwidth and a superframe length to obtain the long-term average interference. In one design, sector 112 compares the long-term average interference to a set of thresholds to determine a general OSI indication, as follows:

等式(1)

Equation (1)

Where Interference _long-term (n) is the long-term average interference of superframe n,

Th1 and Th2 are thresholds used to generate conventional OSI indications,

Regular_OSI(n) is the regular OSI indication for superframe n.

The Th1 threshold is set to the target operating point of the sector 112 or system. Setting the Th2 threshold to a higher value is used to detect excessive interference in sector 112 . In this case, a conventional OSI value is set to '0' to indicate low inter-sector interference, to '1' to indicate moderate inter-sector interference, and to '2' to indicate excessive inter-sector interference. Conventional OSI indications may also be generated in other ways and may include any number of bits of information.

Sector 112 also averages the interference over each subregion and a physical frame length to obtain the short-term average interference. In one design, sector 112 compares the short-term average interference to a threshold to determine a fast OSI indication as follows:

等式(2)

Equation (2)

Among them: Interference _short-term (n, m, s) is the short-term average interference of sub-area s superframe n in PHY frame m,

Th3 is the threshold used to generate a fast OSI indication,

Fast_OSI(n, m, s) is the fast OSI indication of sub-area s superframe n in physical frame m.

In the design shown in equation (2), the fast OSI indication is set to '1' if the short-term average interference is equal to or greater than the Th3 threshold, otherwise it is set to '0'. Fast OSI indications may also be generated in other ways, and the regular OSI indications may include any number of bits of information. A threshold such as Th3>Th2>Th1 is selected. In this case, when high interference is observed in sector 112, the fast OSI indication is used to control the tail of the interference distribution. Sector 112 observes different amounts of interference on different subregions and/or in different PHY frames, and generates different fast OSI indications for different subregions in different PHY frames.

In general, regular OSI indications and fast OSI indications may be determined from any interference metric and any function. As described above, the OSI indication may be generated using a function of the interference measured on different time frequency resources. In another design, the OSI indication may be generated using a function of average and maximum interference measured over different time-frequency resources. This function is especially useful for fast OSI indications.

A conventional OSI indication represents the total interference observed by sector 112 over all or most of the system bandwidth and over an extended period of time (eg, a superframe). Conventional OSI indications are used for power control by all terminals or many terminals in neighboring sectors. A fast OSI indication represents interference in a particular portion of the system bandwidth (eg, a sub-region) and a particular time interval (eg, a PHY frame) as observed by the sector 112 . Specific terminals in adjacent sectors operating in sub-areas with strong interference and in PHY frames use fast OSI indications for power control.

Sector 112 also estimates interference from terminals in a particular neighboring sector and generates a fast OSI indication for the particular neighboring sector. Terminals in each neighboring sector causing strong interference, indicated by a fast OSI indication for that neighboring sector, may reduce their transmit power to reduce interference to sector 112 .

Typically, fast OSI indications are generated for different sub-regions, different PHY frames, different neighboring sectors, etc., or any combination thereof. Different regular OSI and/or fast OSI indications may be combined together for subareas, combinations of subareas and sectors, etc. For clarity, the following is a description of the design for generating fast OSI indications for each sub-region in each PHY frame.

Sector 112 may send regular OSI indications on the F-OSICH in different ways. It is desirable to transmit the F-OSICH over a large coverage area so that terminals not served by sector 112 are able to decode the F-OSICH. It is also desirable for F-OSICH to have the same coverage as TDM/acquisition pilots, which penetrates deeply into adjacent sectors. More ideally, the F-OSICH can be decoded without additional information about the transmitting sector (for example, information other than pilot pseudo-random (PN) information). These requirements make the transmission of F-OSICH expensive in terms of required transmit power and/or time-frequency resources, and limit the rate at which F-OSICH can be sent.

In one design, as shown in FIG. 2, the F-OSICH may be sent in TDM pilots 2 and 3 of the superframe preamble. Conventional OSI directives modulate the phases of TDM pilots 2 and 3. In one design, the regular OSI indication may take values 0, 1, or 2 and modulate the phase 0, 2π/3, or 4π/3 of the TDM pilot, respectively. TDM pilots can be sent with sufficient transmit power to penetrate deep into adjacent sectors. By adding the F-OSICH to the TDM pilot, the regular OSI indication will have the same coverage as the TDM pilot and be received by terminals distributed throughout the neighboring sectors.

Sector 112 may also send fast OSI indications in a different manner. In one design, the fast OSI indication may be sent on a forward fast OSI channel (F-FOSICH) in every PHY frame on the forward link.

In one design, the fast OSI indication may be sent in one or more fast OSI reports, with each report being encoded and modulated separately. In general, each report may include any number of bits indicated by any number of fast OSIs. In one design, each report includes four bits of four fast OSI indications for four subregions in a PHY frame. The four bits are encoded according to an encoding scheme to obtain 12 encoded bits. The coding schemes include forward error detection codes such as cyclic redundancy checks (CRC) and/or forward error correction codes such as convolutional codes. In one design, a 2-bit CRC is generated for a 4-bit report, and the resulting 6 bits are encoded with a rate 1/2 convolutional code to generate the 12 encoded bits for the report. The CRC and the convolutional code constitute a rate 1/3 concatenated code. The 12 coded bits are mapped to 6 modulation symbols according to QPSK. The 6 modulation symbols are sent for reporting.

Typically, the number of fast OSI reports to send depends on different factors such as system bandwidth, number of sub-areas, number of physical frames, etc. For example, if the system bandwidth is 5 MHz and four sub-regions of 1.25 MHz are defined, then four fast OSI indications are generated for the four sub-regions in the PHY frame. A single report containing four fast OSI indications is sent with 6 modulation symbols. If the system bandwidth is 20 MHz and 16 sub-regions of 1.25 MHz are defined, then 16 fast OSI indications are generated for the 16 sub-regions in the physical frame. Four reports are sent with a total of 24 modulation symbols, each report containing four fast OSI indications for four different sub-regions.

It is desirable to send reports of fast OSI indications with the lowest possible transmit power. The fast OSI indication is set to '1' if the short-term average interference exceeds a Th3 threshold which is higher than the highest value of the threshold Th2 for the regular OSI indication. Thus, the probability of setting the fast OSI indication to '1' is low, and the probability of setting the fast OSI indication to '0' is high. In one design, the report for the fast OSI indication that includes all zero values is sent at zero power by mapping the report to a sequence of zero-valued modulation symbols. For example, a 4-bit report containing '0000' is encoded and mapped to six modulation symbols {0, 0, 0, 0, 0, 0}, each modulation symbol 0 being sent at zero power. In fact, the 4-bit report '0000' is not sent and no power is consumed to transmit these four all-zero fast OSI indications. This design reduces the amount of transmit power used to send the fast OSI indication.

In another design, the fast OSI indication is sent separately. For example, each fast OSI indication is mapped to one or more modulation symbols. To reduce transmit power, a fast OSI indication '0' may be mapped to a zero modulation symbol, while a fast OSI indication '1' may be mapped to a non-zero modulation symbol. The number of modulation symbols and/or the transmit power of the modulation symbols used for each fast OSI indication depends on the desired reliability and coverage of the fast OSI indication.

In general, fast OSI indications can be sent in groups and/or individually. Sending Fast OSI indications in groups allows for more efficient coding of reports of a group of Fast OSI indications, which allows for the desired reliability and coverage to be sent with fewer time-frequency resources and/or lower transmit power. report. However, sending in a burst may result in a report with a lower probability of all fast OSI indications being zero. Conversely, sending a fast OSI indication alone results in a higher probability of non-transmission of a fast OSI indication with a value of '0', thereby reducing transmit power. However, higher transmit power and/or more time-frequency resources are used for the actually transmitted fast OSI indication. The way to send the fast OSI indication is selected according to the trade-off between different factors such as transmit power, resource utilization, coverage, reliability and so on.

On the reverse link, each terminal is allowed to transmit at the highest possible power level while keeping interference within acceptable levels. A terminal close to its serving sector is allowed to transmit at a higher power level since this terminal is likely to cause very low interference to neighboring sectors. Conversely, a terminal that is farther away from its serving sector and closer to the edge of coverage is allowed to transmit at a lower power level, since this terminal causes more interference to neighboring sectors. Controlling transmit power in this manner can reduce the interference observed by each sector while allowing terminals with favorable channel conditions to achieve higher data rates.

A given terminal 12Ox adjusts its transmit power according to a power control mechanism in order to achieve reliable transmissions to its serving sector and acceptable levels of interference in neighboring sectors. In general, transmit power can be given by: (i) power spectral density (PSD) in decibels per hertz (dB/Hz), (ii) transmit power per modulation symbol, or (iii) some other unit of measurement.

In the description below, the transmit power of each modulation symbol is given. In one design, terminal 120x may adjust the transmit power of the reference channel to achieve a desired performance level for the reference channel. Then, the terminal 120 determines the transmit power of the data/traffic channel according to the transmit power of the reference channel. The reference channel may be a reverse pilot channel (R-PICH), an acknowledgment channel, a dedicated control channel, an access channel, a request channel, and the like. In one design described below, the reference channel is the R-PICH and the data/traffic channel is the reverse OFDMA data channel (R-ODCH).

In one design, closed-loop power control may be performed on the R-PICH. For closed-loop power control, the serving sector receives the R-PICH from terminal 120x, determines the received symbol quality of the R-PICH, and transmits a power control (PC) bit '1' if the received symbol quality is below a threshold, and a '0' otherwise . Terminal 120x receives the PC bits from the serving sector and adjusts the transmit power of the R-PICH as follows:

等式(3)

Equation (3)

where P _STEP is the power control step size in decibels (dB),

P _PICH is the R-PICH transmit power per modulation symbol.

The closed-loop power control adjusts the transmit power of the R-PICH to achieve the desired received signal quality of the R-PICH. Closed-loop power control may also be performed on another reference channel to achieve a target performance level (eg, a target error rate) for that reference channel.

In one design, delta-based power control may be performed for R-ODCH. For delta-based power control, the transmit power of the R-ODCH is set according to the transmit power of the R-PICH and the offset increment relative to the R-PICH. In one design, terminal 120x maintains a single delta and adjusts the delta based on received regular and fast OSI indications from neighboring sectors. In another design, terminal 120x maintains multiple deltas, including (i) slow deltas, adjusted according to regular OSI directives, (ii) one or more fast deltas, adjusted according to fast OSI directives Adjustment. Transmit power is determined based on the fast and/or slow increments.

In one design, the transmit power of R-ODCH is determined as follows:

P _ODCH,s =P _PICH +Delta _tx,i,s +Boost Equation (4)

where Delta _tx,i,s is the fast increment of sub-area s in HARQ interleaving i,

Boost is the enhancement of the transmit power of the current HARQ transmission,

P _ODCH is the transmit power of R-ODCH per modulation symbol.

In the design shown in equation (4), fast increments are saved for each subregion in each HARQ interlace i of interest. Each packet is sent on the R-ODCH in a specific subregion of a specific HARQ interlace. The increment applied to each packet is then used to determine the transmit power for that packet. The Boost can be zero or non-zero, and can be the same for all HARQ transmissions, or different for different HARQ transmissions. The R-ODCH transmit power may also be determined according to other factors such as Quality of Service (QoS).

In one design, each fast increment is updated based on the fast OSI indication of the subregion in the PHY frame of the HARQ interlace, as follows:

等式(5)

Equation (5)

where FastOSISstepUp is the up-regulation of fast increments,

FastOSISstepDown is a fast incremental down,

FastOSIj,s is the fast OSI indication from neighboring sector j of subarea s.

Terminal 120x maintains a set of neighboring sectors for each sub-region of interest as follows. Call this group a monitoring group. Terminal 120x determines the fast increment for each sub-region based solely on the fast OSI indications from neighboring sectors in the monitoring group for that sub-region. In one design, terminal 120x may adjust fast increments only if terminal 120x used fast increments for data transmission in a previous HARQ interlace and in response to a corresponding fast OSI indication. In another design, terminal 12Ox adjusts fast increments all the time, even during times of no transmission and interleaving for unassigned HARQ. Fast increments can also be adjusted based on buffer size, etc. decisions.

Limit the value of the fast increment to a range of values, as follows:

Equation (6)

where Delta _{max, i, s} is the maximum value of Delta _{tx, i, s} ,

Delta _min,i,s is the minimum value of Delta _tx,i,s .

The minimum and maximum values for fast increments are chosen to achieve good performance and can be fixed or configurable values. For example, the minimum fast delta value and the maximum fast delta value are set according to the dynamic range of the received signal, the amount of intra-sector interference within the serving sector, and the like.

Terminal 120x identifies neighboring sectors for each sub-area based on different metrics for inclusion in the monitoring group. In one design, terminal 120x may use a channel difference metric, which is the difference between the channel gain of a neighboring sector and the channel gain of the serving sector. The channel gain for each sector may be estimated from the TDM pilot, other pilots, Pilot Quality Indicator (PQI), and/or other transmissions sent by the sector on the forward link. The channel difference for adjacent sectors is calculated as follows:

$\mathrm{ChanD}{\mathrm{if}}_j=\frac{{\mathrm{RxPower}}_{\mathrm{RLSS}}}{{\mathrm{EffectiveTxPower}}_{\mathrm{RLSS}}}\&Center\; Dot;\frac{{\mathrm{EffectiveTxPower}}_j}{{\mathrm{RxPower}}_j}$ Equation (7)

where RxPower _RLSS is the received power of the serving sector on the reverse link,

EffectiveTransmitPower _RLSS is the transmit power of the serving sector,

RxPower _j is the received power of adjacent sector j,

EffectiveTransmitPower _j is the transmit power of adjacent sector j, and

ChanDiff _j is the channel difference of adjacent sector j.

The channel gain of a sector is equal to the received power divided by the transmitted power. The channel difference of adjacent sector j is equal to the ratio of the channel gain of the serving sector to the channel gain of adjacent sector j. If ChanDiff _j is less than or equal to an increase threshold, then terminal 120x adds neighboring sector j to the monitoring group. This criterion ensures that the received signal strength of neighboring sector j is strong enough to reliably receive a fast OSI indication from sector j. Terminal 12Ox may only cause significant interference to neighboring sectors in the monitoring group, thereby adjusting the fast increment based only on fast OSI indications from those sectors.

Terminal 120x updates the slow increment based on various factors such as received regular OSI indications from neighboring sectors in the monitoring group, channel differences of neighboring sectors, current transmit power or PSD, and so on. Terminal 120x determines the decision variables for each sector based on the relevant factors for each sector. The decision variable indicates whether to adjust the slow increment and/or by how much to adjust the slow increment. Terminal 120x computes weighted decisions for all neighboring sectors in the monitoring group based on their decision variables and channel differences for these neighboring sectors. Terminal 120x then adjusts the slow delta according to the weighting decision. The slow delta is sent back to the serving sector, and the serving sector uses the slow delta, along with other information, to determine a C/I value for the new assignment of terminal 120x.

Typically, terminal 120x adjusts the slow and fast increments with the same or different algorithms according to the same or different sets of parameters. Different parameters are tuned for slow and fast increments including up-step and down-step sizes, decision thresholds, etc.

The initial values for fast and slow increments can be determined in different ways. In one design, the initial delta value can be calculated as follows:

$\frac{\mathrm{averageIoT}+\mathrm{pCoT}*\mathrm{Delta}}{\mathrm{averageIoT}}<\max \mathrm{IoTRise}$ Equation (8)

where averageIoT is the average interference-over-thermal (IoT) ratio of neighboring sectors,

pCoT is the received carrier power-to-noise ratio (CoT) of the reference channel measured in adjacent sectors,

maxIoTRise is the maximum allowed increase of IoT at adjacent sectors.

If the initial delta value of equation (8) is smaller than the minimum delta value Delta _min , the maximum supported bandwidth W _max will be reduced, thus:

$\frac{\mathrm{averageIoT}+(W_{\max }/W_{\mathrm{total}})*\mathrm{pCoT}*\mathrm{De}{\mathrm{lta}}_{\min }}{\mathrm{averageIoT}}<\max \mathrm{IoTRise}$ Equation (9)

where W _total is the entire system bandwidth. The maximum supportable bandwidth is sent to the serving sector and used to allocate bandwidth to terminal 120x.

If a specific bandwidth W is allocated to terminal 120x, an initial delta value can be calculated such that:

$\frac{\mathrm{averageIoT}+(W/W_{\mathrm{total}})*\mathrm{pCoT}*\mathrm{Delta}}{\mathrm{averageIoT}}<\max \mathrm{IoTRise}$ Equation (10)

The amount of interference at the start of each transmission burst is controlled by limiting the initial maximum supportable bandwidth _Wmax according to the current increment value. The W _max is calculated using equation (10), where W stands for W _max . Terminal 120x sends W _max to the serving sector, which may gradually increase the subsequent allocated bandwidth to allow enough time for the fast OSI indication to adjust the incremental value.

The initial incremental value may also be determined in other ways, and may also be referred to as an open-loop adjustment. In one design, terminal 120x may only perform open-loop adjustments at the beginning of each transmission burst. In another design, if terminal 120x is not scheduled on some HARQ interlaces, 120x uses the initial increment value as the maximum value for fast increments in order to prevent fast increments from becoming too large due to very little OSI indicated activity .

3 shows a design of a power control mechanism 300 for the reverse link. Terminal 12Ox communicates with serving sector 110 and may cause interference to neighboring sectors. The power control mechanism 300 includes a reference loop 302 and an outer loop 304 . Reference loop 302 runs between terminal 120x and serving sector 110 and adjusts the transmit power of the R-PICH. An outer loop 304 runs between terminal 120x and the neighboring sector and adjusts the slow and fast increments based on the regular OSI indications and fast OSI indications received from the neighboring sectors. Reference loop 302 and outer loop 304 run concurrently, but are updated at different rates, eg, reference loop 302 is updated more frequently than outer loop 304 .

For reference loop 302, unit 310 at serving sector 110 estimates the received signal quality of the R-PICH from terminal 12Ox. Unit 310 compares the received signal quality with a target value, and generates PC bits according to the compared result. The transmit processor 314 processes and transmits the PC bits as well as pilot, traffic data and signaling on the forward link (cloud 352). Terminal 120x receives the PC bits from sector 110 . PC bit processor 360 detects each received PC bit and provides a corresponding detected PC bit. Unit 362 adjusts the transmit power of the R-PICH based on the detected PC bits from processor 360, eg, as shown in equation (3).

For outer loop 304, adjacent sectors 112 and 114 receive transmissions on the reverse link. In each neighboring sector, unit 320 estimates the inter-sector interference observed by that sector from terminals in other sectors. Unit 322 generates a regular OSI indication and a fast OSI indication based on the estimated interference, eg, as shown in equations (1) and (2). A transmit processor 324 processes the regular OSI indications and the fast OSI indications and sends them on the forward link to terminals in other sectors. Processor 324 also processes and transmits pilot, traffic data and signaling. Each neighboring sector also forwards the OSI indication to the neighboring sector for transmission to terminals in the neighboring sector. At terminal 12Ox, OSI processor 380 receives regular OSI indications and fast OSI indications from neighboring sectors and provides detected OSI values. A channel estimator 382 determines channel differences for each neighboring sector based on pilot and/or other transmissions. Unit 384 adjusts the slow and fast increments based on detected OSI values, channel differences, and other parameters. Unit 386 determines the transmit power of R-ODCH according to the transmit power of R-PICH, increment and/or other parameters, eg, as shown in equation (4). Transmit processor 364 uses the R-ODCH transmit power to facilitate data transmission to serving sector 110 .

For clarity, the delta-based power control using fast delta adjustments according to the fast OSI indications is described above. Regular OSI indications and fast OSI indications may also be used to adjust the transmit power of terminal 120x according to other power control algorithms.

4 shows a design of a process 400 of sending OSI indications. Process 400 is performed by a sector/base station. For example, multiple OSI indications are determined for multiple sub-regions in each frame, where each sub-region corresponds to a different portion of system bandwidth (block 412). These OSI indications are equivalent to the fast OSI indications described above. Block 412 estimates the interference observed by the sector due to terminals in neighboring sectors. The estimated interference is averaged for each sub-region to obtain the average interference for that sub-region. The OSI indication for each sub-area is determined from the average interference for that sub-area. Each OSI indication consists of a single bit which is set to a first value (e.g. '1') (i) if strong interference is observed in the corresponding subregion, or (ii) if If no strong interference is observed, this bit is set to the second value (eg '0').

The plurality of OSI indications are processed for transmission, eg, broadcast, to terminals in neighboring sectors (block 414). For block 414, at least one report is generated for the plurality of OSI indications, where each report includes at least one OSI indication for at least one subregion (block 416). For example, each report includes four OSI indications for four subregions. Each report includes four bits indicated by four OSIs and is encoded to obtain coded bits that are mapped to a sequence of six modulation symbols (block 418). A sequence of six modulation symbols with zero values may be generated for each of all four OSI indications to indicate that there is no report of strong interference in the four corresponding subregions.

In each superframe, for example, based on the long-term average interference over the system bandwidth and throughout the superframe, a conventional OSI indication of the system bandwidth is determined (block 420). The conventional OSI indication is determined based on at least one first threshold against which long-term average interference is compared. A plurality of OSI indications are determined based on at least one second threshold higher than the at least one first threshold. This will result in multiple OSI indications being less likely to be set than regular OSI indications. A plurality of OSI indications are transmitted at a first rate (eg, per frame) and over a first coverage area (block 422). Regular OSI indications are transmitted at a second rate slower than the first rate (eg, every superframe) and over a second coverage area wider than the first coverage area (block 424).

FIG. 5 shows a design of an apparatus 500 for sending OSI indications. Apparatus 500 includes means for determining a plurality of OSI indications for a plurality of subregions (module 512), means for processing the plurality of OSI indications for transmission (module 514), at least one means for generating the plurality of OSI indications means for each report (block 516), means for encoding each report and mapping it to a sequence of modulation symbols (block 518), means for determining a conventional OSI indication for system bandwidth (block 520), for Means for sending multiple OSI indications (block 522) and means for sending regular OSI indications (block 524).

6 shows a design of a process 600 of receiving an OSI indication. Process 600 is performed by a terminal. At least one OSI indication for at least one subregion is received, where each subregion corresponds to a different portion of system bandwidth (block 612). The at least one OSI indication is received from at least one neighboring sector in the monitoring group. The monitoring group is updated based on the channel gain of the neighboring sectors and the channel gain of the serving sector.

A transmit power (eg, of a data channel) is determined based on the at least one OSI indication (block 614). For block 614, at least one increment of at least one subregion is adjusted according to the at least one OSI indication (block 616). The increment for each sub-area may be: (i) increased if all OSI indications for that sub-area indicate no strong interference, or (ii) decreased if any OSI indication for that sub-area indicates high interference is present. A transmit power for the reference channel is determined according to closed loop power control (block 618). The transmit power for each sub-region is then determined based on the increment for each sub-region and the transmit power for the reference channel (block 620).

The at least one OSI indication of the at least one sub-region is received for at least one interlace (eg, a HARQ interlace), wherein each interlace includes a plurality of frames separated by a predetermined number of frames. An increment for each subregion in each interlace is adjusted based on the OSI indication received for each subregion in each interlace, and the increment is used to determine transmit power for the subregion in the interlace.

A conventional OSI indication of system bandwidth may also be received in each superframe. Transmit power may also be determined from conventional OSI indications.

FIG. 7 shows a design of an apparatus 700 for receiving OSI indications. The apparatus 700 includes: a module for receiving at least one OSI indication of at least one sub-area (module 712), a module for determining transmit power according to the at least one OSI indication (module 714), and a module for adjusting the transmission power according to the at least one OSI indication A module (module 716) for at least one increment of the at least one subregion, a module for determining the transmission power of the reference channel according to closed-loop power control (module 718), and determining according to the increment of each subregion and the transmission power of the reference channel Module of transmit power for each sub-region (block 720).

The modules in FIGS. 5 and 7 may include processors, electronic devices, hardware devices, electronic components, logic circuits, memories, etc., or any combination thereof.

8 shows a block diagram of a design of terminal 120x, serving sector/base station 110, and neighbor sector/base station 112 in FIG. At sector 110, transmit processor 814a receives traffic data from data source 812a, signaling (eg, PC bits) from controller/processor 830a, and/or allocation of time-frequency resources from scheduler 834a. A transmit processor 814a processes (eg, encodes, interleaves, and symbol maps) traffic data, signaling, and pilot and provides modulation symbols. A modulator (MOD) 816a performs modulation (eg, with OFDM) on the modulation symbols and provides output chips. A transmitter (TMTR) 818a conditions (eg, converts to analog, amplifies, filters, and frequency upconverts) the output chip and generates a forward link signal, which is transmitted via antenna 820a.

Sector 112 similarly handles traffic data and signaling for the terminals it serves. The traffic data, signaling and pilot are processed by transmit processor 814b, modulated by modulator 816b, conditioned by transmitter 818b and transmitted via antenna 820b.

At terminal 120x, antenna 852 receives the forward link signals from sectors 110 and 112 and possibly other sectors. A receiver (RCVR) 854 conditions (eg, filters, amplifies, downconverts, and digitizes) the received signal from antenna 852 and provides samples. A demodulator (DEMOD) 856 performs demodulation on the samples (eg, OFDM) and provides symbol estimates. A receive processor 858 processes (e.g., symbol demapping, deinterleaving, and decoding) the symbol estimates, provides decoded data to a data sink 860 and decode signaling (e.g., PC bits, OSI indications, etc.) to a controller/processor 870 ).

On the reverse link, a transmit processor 882 receives and processes traffic data from a data source 880 and signaling from a controller/processor 870 and provides symbols. A modulator 884 performs modulation (eg, with OFDM, CDM, etc.) on the symbols and provides output chips. A transmitter 886 conditions the output chips and generates a reverse link signal, which is sent via antenna 852.

Within each sector, reverse-link signals from terminal 120x and other terminals are received by antenna 820 , conditioned by receiver 840 , demodulated by demodulator 842 and processed by receive processor 844 . Processor 844 provides decoded data to data sink 846 and decode signaling to controller/processor 830 . At serving sector 110, demodulator 842a estimates the received signal quality for terminal 12Ox. Controller/processor 830a generates PC bits for terminal 120x based on received signal quality. In neighboring sectors 112, demodulator 842b estimates the interference observed by the sector. Controller/processor 830b generates regular OSI indications and fast OSI indications based on the estimated interference.

Controllers/processors 830a, 830b, and 870 manage the operation of sectors 110 and 112, respectively, and terminal 120x. Memories 832a, 832b, and 872 store data and program codes for sectors 110 and 112, respectively, and terminal 120x. Schedulers 834a and 834b schedule terminals in communication with sectors 110 and 112, respectively, and assign channel and/or time-frequency resources to the terminals.

The processor in FIG. 8 may perform various functions of the techniques described herein. For example, processor 830a may implement elements 310 and/or 312 in FIG. 3 to serve sectors. Processor 830b may implement elements 320 and/or 322 in FIG. 3 for adjacent sectors and perform process 400 in FIG. 4 and/or other processes for the techniques described herein. Processors 858, 870, and/or 882 may implement some or all of elements 386 through 360 in FIG. 3 for terminal 120x and perform process 600 in FIG. 6 and/or other processes for the techniques described herein.

The channel concept described herein may refer to the type of information or transmission sent by a terminal or a base station. No fixed or predetermined set of subcarriers, time periods or other resources dedicated to such transmissions are required or used. Additionally, time-frequency resources are exemplary resources that may be allocated and/or used for sending data and messages/signaling. Time-frequency resources may also include frequency subcarriers, transmission symbols, and/or other resources in addition to time-frequency resources.

The techniques described herein can be implemented in different ways. For example, these techniques may be implemented in hardware, firmware, software, or a combination thereof. For hardware implementation, the processing unit (such as a base station or a terminal) of an entity for performing the described techniques may be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs) , programmable logic device (PLD), field programmable gate array (FPGA), processor, controller, microcontroller, microprocessor, electronic device, other electronic unit designed to perform the functions described herein , computer, or a combination of these.

For a firmware and/or software implementation, the techniques may be implemented using code (eg, procedures, functions, modules, instructions, etc.) that perform the functions described herein. In general, any computer/processor readable medium tangibly embodying firmware and/or software code may be used in implementing the techniques described herein. For example, firmware and/or software codes may be stored in a memory (eg, memory 832a, 832b, or 872 in FIG. 8) and executed by a processor (eg, processor 830a, 830b, or 870). The memory may be implemented inside the processor or outside the processor. Firmware and/or software code may also be stored on a computer/processor readable medium such as Random Access Memory (RAM), Read Only Memory (ROM), Non-Volatile Random Access Memory (NVRAM), Programmable Read Only Memory (PROM), Electrically Erasable PROM (EEPROM), Flash Memory, Floppy Disk, Compact Disk (CD), Digital Video Disk (DVD), Magnetic or Optical Data Storage, etc. Code can be executed by one or more computers/processors and can cause the computers/processors to perform some aspects of the functionality described herein.

The above description of the invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to this invention will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other modifications without departing from the spirit and scope of this invention. Thus, the present invention is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features of this invention.

Claims (35)

1. A method for wireless communication, comprising: determining a plurality of other sector interference OSI indications respectively corresponding to a plurality of sub-regions, each sub-region corresponding to a different portion of the system bandwidth, and The plurality of OSI indications are processed for transmission. 2. The method of claim 1, wherein said determining a plurality of OSI indications comprises: The plurality of OSI indications respectively corresponding to the plurality of sub-areas are determined within each frame of a predetermined period. 3. The method of claim 1, wherein said determining a plurality of OSI indications comprises: Estimate the interference observed by a sector caused by terminals in neighboring sectors, and The plurality of OSI indications respectively corresponding to the plurality of sub-areas are determined based on the estimated interference. 4. The method of claim 3, wherein the determining the plurality of OSI indications respectively corresponding to the plurality of sub-areas from the estimated interference comprises: Compute the average of the estimated interference for each subregion to obtain the average interference for each subregion, and The OSI indication for each sub-area is determined from the average interference for each sub-area. 5. The method of claim 1, wherein, Each OSI indication consists of a single bit; Wherein, the determining multiple OSI indications includes: set a single bit per OSI indication to the first value if strong interference is observed in the corresponding sub-region, and A single bit per OSI indication is set to the second value if no strong interference is observed in the corresponding sub-region. 6. The method of claim 3, further comprising: calculating an average of the estimated interference for said system bandwidth to obtain a long-term average interference, and A regular OSI indication is determined from the long-term average interference. 7. The method of claim 1, wherein the processing the plurality of OSI indications comprises: At least one report is generated for the plurality of OSI indications, each report including at least one OSI indication corresponding to at least one sub-area. 8. The method of claim 7, wherein each report includes four OSI indications respectively corresponding to the four sub-areas. 9. The method of claim 8, wherein, Each report includes four bits indicated by the four OSIs; Wherein, the processing the multiple OSI indications further includes: encode each four-bit report to obtain encoded bits, and A sequence of six modulation symbols is generated for each report based on the coded bits for each report. 10. The method of claim 7, wherein the processing the plurality of OSI indications further comprises: For each report for which at least one OSI indication is all set to a predetermined value, a sequence of modulation symbols with a value of zero is generated for it. 11. The method of claim 8, wherein the processing the plurality of OSI indications further comprises: For each report for which all four OSI indications are set to zero to indicate that there is no strong interference in the corresponding four sub-regions, a sequence of six modulation symbols with a value of zero is generated for it. 12. The method of claim 1, further comprising: The plurality of OSI indications are broadcast to terminals in neighboring sectors. 13. The method of claim 1, further comprising: determining a conventional OSI indication for the system bandwidth; and A conventional OSI indication of the system bandwidth is sent. 14. The method of claim 13, further comprising: sending the plurality of OSI indications respectively corresponding to the plurality of sub-areas at a first rate, and The regular OSI indication of the system bandwidth is sent at a second rate slower than the first rate. 15. The method of claim 13, further comprising: sending the plurality of OSI indications respectively corresponding to the plurality of sub-areas within the first coverage area, and The regular OSI indication of the system bandwidth is transmitted within a second coverage area larger than the first coverage area. 16. The method of claim 13, wherein: determining said regular OSI indication based on at least one first threshold against which estimated interference is compared, and The plurality of OSI indications are determined based on at least one second threshold higher than the at least one first threshold. 17. An apparatus for wireless communication comprising: means for determining a plurality of other sector interference OSI indications respectively corresponding to a plurality of sub-regions, each sub-region corresponding to a different portion of the system bandwidth; Means for processing the plurality of OSI indications for transmission. 18. The apparatus of claim 17, wherein the means for determining a plurality of OSI indications comprises: means for determining the plurality of OSI indications respectively corresponding to the plurality of sub-regions within each frame of a predetermined period. 19. The apparatus of claim 17, wherein the means for processing a plurality of OSI indications comprises: Means for generating at least one report for the plurality of OSI indications, wherein each report includes at least one OSI indication corresponding to at least one sub-region. 20. The apparatus of claim 19, wherein, Each report includes four OSI indications for four subregions; and Wherein, the module for processing multiple OSI indications further includes: A module for encoding each report to obtain encoded bits; Means for generating a sequence of six modulation symbols for each report from its coded bits. 21. The apparatus of claim 20, wherein the means for processing a plurality of OSI indications further comprises: Means for generating, for each report for which all four OSI indications are set to zero to indicate no strong interference in the four respective subregions, a sequence of six modulation symbols with values of zero. 22. The apparatus of claim 17, further comprising: means for determining a general OSI indication for the system bandwidth; and means for sending a conventional OSI indication of said system bandwidth. 23. A method for wireless communication comprising: receiving at least one other sector interference OSI indication respectively corresponding to at least one sub-region, each sub-region corresponding to a different portion of the system bandwidth, and Transmit power is determined based on the at least one OSI indication. 24. The method of claim 23, wherein said determining transmit power comprises: adjusting at least one increment of at least one sub-region according to said at least one OSI indication, and The transmission power of each sub-area is determined according to the increment of each sub-area. 25. The method of claim 24, wherein said determining transmit power comprises: determining the transmit power of the reference channel according to closed-loop power control, and The transmit power of each sub-area is determined according to the transmit power of the reference channel and the increment of each sub-area. 26. The method of claim 24, wherein said adjusting at least one increment comprises: For each sub-area for which all OSI indications indicate no strong interference, increase its increment, and For each sub-area that has an OSI indication indicating strong interference, decrease its increment. 27. The method of claim 23, wherein, The receiving at least one OSI indication includes: receiving said at least one OSI indication respectively corresponding to said at least one subregion in at least one interlace, each interlace comprising a plurality of frames separated by a predetermined number of frames, The determination of transmit power includes: adjusting the increment for each subregion in each interlace based on the received OSI indication for each subregion in each interlace, and The transmit power of each subregion in each interlace is determined according to the increment of each subregion in each interlace. 28. The method of claim 23, wherein said receiving at least one OSI indication comprises: receiving at least one OSI indication from at least one neighboring sector in the monitoring group, and The monitoring group is updated based on the channel gain of the neighboring sectors and the channel gain of the serving sector. 29. The method of claim 23, further comprising: receiving a conventional OSI indication of the system bandwidth, and Transmit power is also determined from said conventional OSI indications. 30. An apparatus for wireless communication comprising: means for receiving at least one other sector interfering OSI indication respectively corresponding to at least one sub-region, each sub-region corresponding to a different portion of the system bandwidth; and Means for determining transmit power based on the at least one OSI indication. 31. The apparatus of claim 30, wherein the means for determining transmit power comprises: means for adjusting at least one increment of at least one sub-region according to at least one OSI indication; and Module for determining transmit power per subregion based on increments per subregion. 32. The apparatus of claim 31 , wherein said means for adjusting at least one increment comprises: means for increasing the increment for each sub-area for which all OSI indications indicate no strong interference; and Means for reducing the increment for each sub-area that has an OSI indication indicating the presence of strong interference. 33. The apparatus of claim 30, wherein, The module for receiving at least one OSI indication includes: means for receiving at least one OSI indication respectively corresponding to at least one subregion in at least one interlace, each interlace comprising a plurality of frames separated by a predetermined number of frames; and The module for determining transmit power includes: means for adjusting an increment of each subregion in each interlace based on a received OSI indication for each subregion in each interlace; and Means for determining transmit power for each subregion in each interlace based on an increment for each subregion in each interlace. 34. The apparatus of claim 30, wherein the means for receiving at least one OSI indication comprises: means for receiving at least one OSI indication from at least one neighboring sector in the monitoring group; and Means for updating the monitoring group based on channel gains of neighboring sectors and channel gains of a serving sector. 35. The apparatus of claim 30, further comprising: means for receiving a conventional OSI indication of said system bandwidth, and means for determining the transmit power also based on the conventional OSI indication.

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