Interference control in a wireless communication system

Description

BACKGROUND

I. Field of technology

[0001] The present invention relates generally to communication, and more specifically to interference control in a wireless communication system.

II. Background

[0002] Wireless multiple-access communication systems can communicate with multiple terminals on the forward and reverse link simultaneously. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. Multiple terminals may simultaneously transmit data on the reverse link and / or receive data on the forward link. This is often achieved by multiplexing the transmissions on each link so as to be orthogonal to each other in the time, frequency, and / or code domains.

[0003] On the reverse link, transmissions from terminals communicating with other base stations typically are not orthogonal to each other. Consequently, each terminal may cause interference to other terminals communicating with nearby base stations, and may also receive interference from those other terminals. The performance of each terminal is degraded by interference from other terminals communicating with other base stations.

[0004] There is therefore a need in the art for methods to reduce interference in a wireless communication system.

53 / 59P33632PL00

[0005] Reference is made to US 2001/053695, which describes that not only information in the cell in which the call is established but also cell state information from cells is used as input when making decisions in a telecommunications network. which are adjacent to the cell where the call is established. Cell state information from neighboring cells is obtained even in situations where an adjacent cell is controlled by another telephone exchange, e.g. another radio network controller. The cell state information used for decision making includes measured data obtained over at least a portion of a plurality of cell connections, one example of which is radio interference information. Cell state information used in network decision making is transmitted between telephone exchanges using common channel signaling.

[0006] Further, reference is made to GB 2 378 858 which describes a method for minimizing interference caused by transmissions from the antenna of a first base station detected by a mobile station located in the coverage area of ​​a neighbor base station. The antenna direction of the first base station is computed and at least one neighbor base station is identified, whose coverage area partially overlaps the coverage area of ​​the first base station. The intensity of the radiation of the directional pattern towards the adjacent base station is calculated. The mobile station reports carrier signal levels versus interference (C / I) within the coverage area of ​​a neighbor base station, preferably versus time, with interference originating from the carrier signal of the first base station. The C / I level is compared with the preset threshold to provide the desired attenuation level of the first base station carrier signal. It is

The 53 / 59P33632PL00 is then used to adjust the directional characteristic, adopting a second radiation to replace the first radiation. A weighting factor for a plurality of mobile stations served by neighbor base stations may be used in the adjustment factor as well as a change in the C / I measurement reports and the relative heights of the base stations.

[0007] Moreover, attention is drawn to US2004229615 A1 which relates to techniques for supporting soft handover in an OFDMA system with frequency hopping. Each sector simultaneously serves non-soft-handing users and soft-handing users. Users without soft handover communicate with only one sector, and users with soft handover communicate with multiple sectors simultaneously. Users without soft handover are assigned traffic channels by their only sectors and users with soft handover are assigned traffic channels by their "serving sectors." For each sector, the traffic channels assigned to users without soft handover are orthogonal to each other and may or may not be orthogonal to the traffic channels assigned to users with soft handover. Each sector processes its received signal and recovers data transmissions from the user without soft sector switching. Each sector then estimates user interference without soft handover and eliminates interference from the received signal. Each sector further processes its noise canceled signal to recover data transmission from soft handover users.

SUMMARY OF THE INVENTION

[0008]

According to the present invention, it is provided

An apparatus and a communication control method as set forth in claims 1, 6, 8 and 12. Embodiments of the invention are claimed in the dependent claims.

[0009] Methods for controlling the interference observed by each sector from its neighbor sectors in a wireless communication system are described herein. Sector m estimates interference observed from terminals in neighbor sectors and obtains the interference estimate or related measurements. For network based interference control, sector m generates an inter-sector (IS) OSI report based on the interference estimate and sends the IS OSI report to neighbor sectors over a wired connection, e.g., a backhaul link. Sector m also receives IS OSI reports from neighbor sectors and regulates data transmissions for terminals in sector m based on received IS OSI reports. Sector m may regulate data transmissions by (1) controlling the access of new terminals to sector m, (2) receiving an assignment from already granted terminals, (3) scheduling terminals in sector m so as to reduce interference for neighboring sectors and / or (4) assigning the terminals in sector m of traffic channels that cause less interference to neighbor sectors.

[0010] Various aspects and embodiments of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features and essence of the present invention will become more apparent from the detailed description provided below taken in conjunction with the drawings, wherein the same reference numerals are used for identification throughout the description.

[0012] In FIG. 1 shows a communication system with base stations and terminals.

53 / 59P33632PL00

<td> [0013]</td><td>On</td><td>FIG. 2 shows the process performed by</td><td>one</td>

<td>sector for [0014]</td><td colspan="2">a disturbance control. In FIG. 3 shows the process performed by</td><td>one</td>

<td>terminal [0015]</td><td>for On</td><td>disturbance control. FIG. 4 shows the adjustment process</td><td>power</td>

<td>transmitting [0016]</td><td>in On</td><td>deterministic way. FIG. 5 shows the adjustment process</td><td>power</td>

<td>transmitting [0017]</td><td>in On</td><td>probabilistic way. FIG. 6 shows the control mechanism</td><td>power</td>

suitable for disturbance control.

[0018] In FIG. 7 shows a base station duplex.

[0019] In FIG. 8 shows the disturbance control.

[0020] In FIG. 9 shows interference control provisioning.

the terminal block diagram and the device suitable for the device suitable for

DETAILED DESCRIPTION

[0021] The term "exemplary is used to mean" serving as an example, instance, or illustration. Any embodiment or structure described herein as "exemplary" need not necessarily be interpreted as being preferred or preferred over the other embodiment or structure.

[0022] FIG. 1 shows a wireless communication system 100 with a plurality of base stations 110 and a plurality of terminals 120. A base station is a generally fixed station that communicates with terminals and may also be referred to as an access point, a node B, or by means of a different nomenclature. Each base station 110 provides communication coverage for a specific geographic area 102. The term "cell may refer to a base station and / or its base station.

53 / 59P33632PL00 of the coverage area, depending on the context in which the term is used. To improve system performance, the base station coverage area may be divided into multiple smaller areas, such as three smaller areas 104a, 104b and 104c, for example. Each smaller area is served by a corresponding base transceiver subsystem (BTS). The term "sector may refer to a BTS and / or its coverage area, depending on the context in which the term is used. For a sectorized cell, the BTSs for all sectors of that cell are typically co-located within the base station for the cell. The system controller 130 communicates with the base stations 110 and provides coordination and control for those base stations.

[0023] The terminal may be stationary or mobile, and may also be referred to as a mobile station, wireless device, user equipment, or some other nomenclature. Each terminal may communicate with any, one, or more base stations at any given time.

[0024] The interference control methods described herein may be used for a system with sectorized cells and a system with non-sectorized cells. In the following description, the term "sector refers to (1) a legacy BTS and / or its coverage area for a system with sectorized cells and (2) a legacy base station and / or its coverage area for a system with non-sectorized cells. . The terms "terminal and" user are used interchangeably, and the terms "sector and" base station are also used interchangeably. The serving base station / sector is the base station / sector with which the terminal communicates. A neighbor base station / sector is a base station / sector with which the terminal is not in communication.

[0025] The interference control methods may also be used for various communication systems from

53 / 59P33632PL00 multi-access. For example, these methods may be used for a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, an interleaved system ( IFDMA), FDMA Localization System (LFDMA); a spatial division multiple access (SDMA) system, a guasiorthogonal multiple access system, and so on. The IFDMA system is also referred to as distributed FDMA system, and LFDMA is also referred to as narrowband FDMA system or classic FDMA. The OFDMA system uses orthogonal frequency division multiplexing (OFDM). OFDM, IFDMA, and LFDMA systems efficiently divide the total bandwidth into multiple (K) subbands with orthogonal frequencies. These subbands may also be referred to as tones, subcarriers, bins, and so on. The OFDM system transmits frequency domain modulation symbols on all subbands or a subset of the K subbands. The IFDMA system transmits time-domain modulation symbols on the subbands that are evenly spread across the K subbands. An LFDMA system transmits modulation symbols in the time domain and typically on adjacent subbands.

[0026] As shown in FIG. 1, each sector can receive "desired transmissions from terminals in the sector as well as" interfering transmissions from terminals in other sectors. The total interference observed for each sector consists of (1) intra-sector interference from terminals in the same sector and (2) intra-sector interference from terminals in different sectorings. Inter-sector interference, which is also called Other Sector Interference (OSI), results from the fact that transmissions in each sector are not orthogonal to transmissions in other sectorings. Inter-sector interference and intra-sector interference do

The performance is greatly affected and can be reduced as described below.

[0027] Cross-sector interference may be controlled by various mechanisms such as user based interference control and network based interference control. For user-based interference control, the terminals are informed of the inter-sector interference observed by neighbor sectors and adjust their transmit powers accordingly such that inter-sector interference is kept at acceptable levels. For network based interference control, each sector is informed of the intersectoral interference observed by neighboring sectors and regulates data transmissions for the terminal pins such that the intersectoral interference is kept within acceptable levels. The system may use only user-based disturbance control, or only network-based disturbance control, or both. The interference control mechanisms, and the combinations thereof, may be implemented in various manners, as described below.

[0028] In FIG. 2 shows a process 200 performed by one sector m for inter-sector interference control. Sector m estimates interference observed from terminals in other sectors and obtains an interference estimate (block 210). Additionally, the generated information need not be interference estimates and may be raw measurements and, or, thresholds obtained by sector m for terminals of other sectors.

[0029] For user based interference control, sector m generates an over-air-air (OTA) OSI report based on the interference estimate (block 212). The OTA OSI report carries the amount of inter-sector interference observed by sectors and can exist in a variety of forms as described below. Sector m broadcasts an OTA OSI report to terminals in its neighbor sector (block 214). These terminals can regulate their transmitting powers on

Based on the OTA OSI report from sector m, if necessary, to limit the amount of inter-sector interference observed by sector m.

[0030] For network based interference control, sector m generates an inter-sector (IS) OSI report based on the interference estimate (block 222). The IS OSI report and the OTA OSI report are two interference reports that may be the same or different formats. For example, the IS OSI report may be the same as the OTA OSI report. Alternatively, the IS OSI report may consist of information pertaining to interference thresholds, interference measurements, path loss, power received from the terminals of sector m measured in other sectors, and / or any other information is received that may be used to determine interference caused by terminals. m and other sector from the IS OSI report. Sector m may send the IS OSI report to neighboring sectors periodically or only when sector m observes excessive interference (block 224). Sector m also receives IS OSI reports from neighbor sectors (block 226). The rate at which IS OSI reports are exchanged between sectors may be the same or different than the rate at which OTA OSI reports are broadcast to the terminals. Sector m regulates data transmissions for terminals in sector m based on IS OSI reports received from neighbor sectors (block 228). The blocks in FIG. 2 are described in more detail below.

[0031] Sector m may estimate inter-sector interference in a variety of ways. For a system using orthogonal multiplexing, one terminal may transmit data or a pilot on each subcarrier in each symbol period. The remote control is the transmission of symbols that are known a priori by both the transmitter and the receiver. The data symbol is the modulation symbol for data, the pilot symbol is the modulation symbol for the pilot, and the modulation symbol is a complex value for

53 / 59P33632PL00 point in the signal constellation, e.g. for M-PSK, M-QAM modulation and so on.

[0032] Sector m may estimate the interference on a given subcarrier k in a given symbol period n based on the pilot received from terminal u, as follows:

= P_at(k, n) ~ R_m^ k, n) \² , Equation (1) where P._at (k, n) is the pilot symbol sent by terminal u on the subcarrier k in symbol period n;

H._mrU{k, n) is an estimate of the channel gain between sector m and terminal u;

Rn-_lfU(k, n) is the received symbol received by sector m from terminal u; and

T._x(k, n) is an estimate of the disturbances observed by sector m.

The quantities in equation (1) are scalar values.

[0033] Sector m may also estimate the interference based on data received from terminal u, as follows:

L. ⁿ) = I (*. «) (M) - R_mjl (k, n) |² , Equation (2) where D._mfU(k ^ n) is an estimate of the data symbol transmitted by terminal u on a subcarrier k in period n of the symbol. The sector m can derive estimates of D._m,_at(k, n) data symbols by (1) performing data discovery on the received R symbols_m^_at(k ^ n) using the estimate of H._mrU{k, n) channel to obtain detected symbols, (2) determining difficult decisions based on the detected symbols, and (3) using difficult decisions as estimates of data symbols. Alternatively, sector m can determine data symbol estimates by (1) performing data discovery on received symbols, (2) decoding detected symbols to obtain decoded data, and (3) re-encoding and

Mapping to decoded data symbols to obtain data symbol estimates.

[0034] Sector m may also perform joint channel and interference estimation to obtain both the channel response estimates and the interference estimates.

The estimate Imik ^ n) of the interference obtained from equation (1) or (2) includes both intersectoral interference and intra-sector interference. Intra-sector interference may be kept within acceptable levels via power control, as described below, and may then be insignificant compared to intersectoral interference.

[0036] Sector m may average the interference estimates in the frequency, spatial and / or time domains. For example, sector m may average the interference estimates across the plurality of receive antennas. Sector m may average the interference estimates for all subbands using any of the following averaging schemas:

Equation (3)

<img file="PL1859588T3_D0001.tif" />

1 / K

Equation (4) log 1 +

<img file="PL1859588T3_D0002.tif" />

Pam Ί

Equation (5) where I_m(n) is the average interference power for sector m over n symbol period, and P_mon is the nominal received power for each subcarrier. Imik ^ n) and ΙπΛη) are linear units in equations (3) to (5). Equation (3) is for arithmetic averaging, equation (4) is for geometric averaging, and equation (5) is for averaging based on SNR. For arithmetic averaging, several larger disturbance estimates may cause the mean power cutoff

Noise. 53 / 59P33632PL00. Geometric averaging and averaging based on SNR can suppress large interference estimates for several subbands.

[0037] Sector m may also filter the average interference power over a plurality of symbol periods to improve the quality of the interference estimation. Filtering may be achieved with a finite impulse response (FIR) filter, an infinite impulse response (IIR) filter, or some other type of filter. Sector in receives the measured disturbance I_meas,_mfor each measurement period that may span one or more symbol periods.

[0038] Sector m generates an OTA OSI report based on the measured interference. In an embodiment, the measured interference is quantized to a predetermined number of bits which is included in the OTA OSI report. In another embodiment, the OTA OSI report includes a single bit that indicates whether the measured interference is greater or less than an interference threshold. In yet another embodiment, the OTA OSI report includes a plurality of bits that convey the measured interference with respect to the plurality of interference thresholds. For clarity, the following description relates to an embodiment in which the OTA OSI report conveys the measured interference with respect to the double interference thresholds. [0039] In an embodiment, the OTA OSI report includes two binary OSI bits, which are referred to as the OSI bit 1 and the OSI bit 2. These OSI bits can be set as follows:

OSI bitl =, if - Inomuth '' θ'- J^if

Equation (6a) bit 2 OSI = 'V. if^Ό'&gt; if I ^ &lt;1 ^,

Equation (6b)

53 / 59P33632PL00 where I_nom th is the nominal disturbance threshold, I_hand_gh th is the large disturbance threshold i_hand_gh_th&gt; Inomth · OSI bit 1 indicates whether the measured disturbance is above or below the nominal disturbance threshold. OSI bit 2 indicates whether the measured interference is above or below the high interference threshold. For this embodiment, sector m is considered to observe low interference if the measured interference is below Inomth, large interference if the measured interference is between I_nom th and Ih ±_gh th, and excessive interference if the measured interference is greater than or equal to Ih ±_gh th · OSI bit 2 may be used to indicate excessive interference observed by the sector.

[0040] In another embodiment, the OTA OSI report comprises a single OSI value having three levels. The OSI value can be set as follows:

and '2' if I_meas,_m &gt; I_wgIuh, OSI VALUE — j 1, if ^ nonuh »

[Ό ', if Ι ^, ", &lt;i_nomJh ·

Equation (7)

The three-level OSI value may be transmitted using a signal constellation having three signal points. For example, an OSI value of '0' can be sent with the symbol 1 + jO or e^j0, an OSI value of '1' can be sent with the symbol 0 + gl or e ^^{n / 2}and an OSI value of '2' can be sent with the symbol -1 + jO or e^jn.

[0041] Alternatively, sector m may obtain a measured thermal-noise-interference (IOT), which is the ratio of the total power of the interference observed by sector m to that of the thermal noise. The total interference power can be calculated as described above. The thermal noise power can be estimated by turning off the transmitter and measuring the noise at the receiver. A specific operating point can be selected for

53 / 59P33632PL00 system. A higher operating point allows the terminal to transmit on average with higher power levels. However, a high operating point has a negative effect on the link balance and may be undesirable. For a given maximum transmit power and a given data rate, the tolerable maximum path loss decreases as the IOT ratio increases. A very high operating point is also undesirable as the system can become interference constrained, which is a situation where an increase in transmit power does not translate into an increase in the received SNR. Furthermore, a very high operating point increases the probability of system instability. In any case, sector m may set its three-level OSI value as follows:

'2' if LOT ^ ŁOT, OSI value = T, if IOT_IN &gt; IOT ",&gt; IOT_Mnuh,

Equation (8)

Ό ', if IOT "&lt;ΙΟΤ ^, where IOT_nom__volh is the threshold of the nominal IOT ratio and the IOT_hlgh th is the high IOT threshold value.

[0042] The OSI bits / value may also be generated using hysteresis so that the excessive noise indication is not changed too often. For example, OSI bit 2 may be set to '1' only if the measured interference exceeds the high threshold for the first duration T_W1 (e.g. 50 milliseconds) and can only be reset to '0' if the measured disturbances are below the high threshold for the second duration T_w2. As another example, OSI bit 2 may be set to '1' only if the measured interference exceeds the first high threshold I_hand_gh thi i can then be reset to '0' only if the measured interference is below the second high threshold I_hand_gh_th2, where i_hand_gh_thi&gt; I_hand_gh_th2 · Sector m broadcasts its OTA OSI report, which may include two OSI bits or a three-level OSI value, for

User based interference control. Sector m may broadcast the OTA OSI report in various ways. In an exemplary embodiment, sector m broadcasts an OTA OSI report in each measurement period. In another embodiment, sector m broadcasts OSI bit 1 in each measurement period and broadcasts OSI bit 2 only if this bit is set to '1'. Sector m may also broadcast OSI reports from other sectors to terminals in sector m for better OSI coverage area.

[0044] Sector m also sends its IS OSI report to neighbor sectors for network based interference control. The IS OSI report may contain two OSI bits; the three-level OSI value; quantized or non-quantized measured interference of a predetermined number of bits; I0T_nom th, IOT_hand_gh th and I0T_meas,_m; Inom_th, Ihigh_th and Imea_S.,_m; track loss; received power from the terminals of sector m measured in other sectors; some other information; and their combinations. Sector m may send an IS OSI report in each measurement period, or only if excessive interference is observed, or if some other criterion is met. The other sector q may also request sector m to send an IS OSI report if the terminals in sector q indicate that they cannot receive OSI bits from sector m. Each sector uses IS OSI reports from neighbor sectors to control data transmissions from terminals in its sector to reduce inter-sector interference in neighbor sectors.

[0045] Network based interference control may be achieved in various ways. Some embodiments of a network based interference control are described below.

[0046] In one embodiment, sector m schedules terminals in the sector based on IS OSI reports received from neighbor sectors. For example, if one or more of the neighboring sectors observe excessive interference, then sector m may limit transmit powers used by disadvantaged terminals in sector m such that

These terminals cause less interference to other sectors. The terminal is disadvantaged having low channel gain (or high path loss) for the serving sector and must transmit at a high power level in order to obtain a given signal-to-noise and interference ratio (SNR) in the serving sector. The disadvantaged terminal is typically closer to the neighbor sector and the high transmit power level results in high cross-sector interference for that neighbor sector.

Sector m can identify disadvantaged terminals based on various quality metrics such as channel gain, pilot strength, carrier signal to noise ratio (C / N), channel gain ratio, and so on. These quality metrics can be estimated from the pilot and / or other transmissions sent by the terminals. For example, the estimated channel gain for a terminal may be compared with a channel gain threshold and the terminal may be considered a disadvantaged terminal if its channel gain is below the channel gain threshold. Additionally, disadvantaged terminals may be identified in the IS OSI report together with their measured values, e.g., I0T_meas,_m or measured received power. In addition, in some cases, the IS OSI report may provide information regarding terminal identification and nothing else to enable the other approaches described below.

[0048] Sector m may limit transmit powers used by disadvantaged terminals by (1) lowering the transmit power upper limit that is applied to the terminals, (2) lowering the transmit power lower limit that is applied to the terminals, (3) assigning disadvantaged terminals with lower data rates which require lower SNRs and therefore lower transmit powers. (4) bypassing scheduling of disadvantaged terminals for data transmission, or

53 / 59P33632PL00 (5) using some other method or combination of methods.

[0049] In another embodiment, sector m uses access control to reduce the inter-sector interference observed by neighbor sectors. For example, if one or more neighboring sectors observe excessive interference, then sector m may limit the number of active terminals in the sector by (1) denying access to new terminals requesting transmission on the reverse link, (2) denying access to disadvantaged terminals, (3) ) receiving an assignment from terminals that have already been granted access, (4) receiving an assignment from disadvantaged terminals, or (5) employing any other means of access control. The frequency of receiving assignments to terminals may also become a function of IS OSI reports from neighbor sectors (e.g., observed interference levels), the number of neighboring sectors observing excessive interference, and / or other factors. Sector m may therefore adjust sector load based on IS OSI reports from neighbor sectors.

[0050] In yet another embodiment, sector m assigns traffic channels to terminals in the sector such as to reduce inter-sector interference observed by neighbor sectors. For example, each sector may be assigned a set of traffic channels, which sectors may in turn assign to terminals in the sector. Adjacent sectors may also share a common set of traffic channels that is orthogonal to the set of traffic channels assigned to each sector. If one or more neighboring sectors observe excessive interference, then sector m may assign disadvantaged terminals in sector m traffic channels in a common set. These disadvantaged terminals would then not cause any interference to the neighboring sectors because the traffic channels in a common set are orthogonal to the traffic channels.

53 / 59P33632PL00 assigned to neighbor sectors. As another example, each sector may be assigned a set of traffic channels, which sector may assign to strong terminals that can tolerate high levels of interference. If one or more neighboring sectors observe excessive interference, then sector m may assign disadvantaged terminals in sector m the traffic channels assigned to strong terminals in the neighbor sectors.

[0051] A combination of one or more of the above approaches may also be used for flexibility or other reasons.

For the sake of clarity, much of the description above is for one sector m. Each sector in the system may implement interference control as described above for sector m.

User based interference control may also be achieved in various manners. In an exemplary embodiment, user-based interference control is achieved by allowing terminals to autonomously adjust transmit power bolts based on OTA OSI reports received from neighbor sectors.

[0054] It should be noted that while FIG. 2 shows the use of both network based interference control and user based interference control, only one approach can be used. For example, blocks 212 and 214 may be omitted and all interference control may be provided by using only network based interference control, e.g., as discussed in relation to blocks 222228.

[0055] In FIG. 3 shows a process 300 performed by one terminal u for interference control. Terminal u receives the OTA OSI report from the neighbor sector (block 312). It is then determined whether the neighbor sector is observing excessive interference, e.g., whether OSI bit 2 is set to '1' (block 314).

53 / 59P33632PL00

If the answer is 'Yes' then terminal u limits its transmit power with a larger step size and / or a higher rate (block 316). Otherwise, it is determined whether the neighbor sector is observing large interference, e.g., whether OSI bit 1 is set to '1' and bit 2 of the OSI is set to '0' (block 318). If the answer is "Yes", then terminal u limits its transmit power by the nominal shrink step size and / or at the nominal rate (block 320). Otherwise, terminal u will increase its transmit power by the nominal size of the step-up and / or at the nominal rate (block 322).

[0056] In FIG. 3 shows an embodiment in which the OTA OSI report carries the inter-sector interference observed by a neighbor sector at one of three possible low, high and excessive levels. Process 300 may be extended to include any number of interference levels. In general, transmit power for terminal u may be (1) reduced by a gradual reduction that is related to the amount of interference observed by a neighbor sector (e.g. greater stepwise reduction for greater interference) when the measured interference is above a given threshold, and / or (2) increased by a stepwise increase which is inversely related to the amount of noise observed by a neighbor sector (e.g. a greater stepwise increase for less interference) when the measured disturbances are below a given threshold value. The size of the gradual change and / or the rate of regulation may also be determined based on other parameters such as, for example, the current transmit power level for the terminal, the channel gain for the neighbor sector with respect to the channel gain for the serving sector, previous OTA OSI reports, and so on. on.

53 / 59P33632PL00

Terminal u may adjust its transmit power based on an OTA OSI report from one or more neighboring sectors. Terminal u may estimate the channel gain for each sector based on the pilot received from the sector. Terminal u may then determine the channel gain ratio for each neighbor sector as follows:

S "(»)

Equation (9) where g_nSrand (n) is a channel gain between terminal u and adjacent sector i;

g_pp (n) is a channel gain between terminal u and serving sector; and ri (n) is the channel gain ratio for the neighbor sector i.

[0058] In one embodiment, terminal u identifies the strongest neighbor sector with the largest channel gain ratio. Terminal u then adjusts its transmit power based on the OTA OSI report from only this strongest neighbor sector. In another embodiment, terminal u adjusts its transmit power based on OTA OSI reports from all sectors in the OSI set. This OSI set may include (1) T strongest adjacent sectors, where Th1, (2) adjacent sectors with channel gain ratios exceeding the channel gain ratio threshold, (3) adjacent sectors with channel gains exceeding the channel gain threshold, (4) adjacent sectors sectors included in a neighbor list broadcast by the serving sector, or (5) some other group of neighbor sectors. Terminal u may adjust its transmit power in various ways based on OTA OSI reports from multiple neighboring sectors in the OSI set. For example, terminal u may decrease its transmit power if any neighbor

A sector in the OSI set observes high or excessive interference. As another example, terminal u may determine transmit power control for each neighbor sector in the OSI set and may then combine adjustments for all neighbor sectors in the OSI set to obtain complete transmit power control.

[0059] In general, transmit power control for interference control may be performed in conjunction with various power control schemes. For the sake of clarity, the specific power control scheme is described below. For this power control scheme, the transmit power for the traffic channel assigned to terminal u may be expressed as:

P._dch = P_ref 00 + ΔΡ (η), Equation (10) where P_dch (n) is the transmit power for the traffic channel for the update interval n;

P._ref (n) is the reference power level for the update interval n; and

ΔΡ (η) is the transmit power delta for the update interval n. P transmit power levels_dch(n) and P_ref (n) and the transmit power delta ΔΡ (η) are given in decibel units (dB).

[0060] Reference power level P_ref (n) is the amount of transmit power needed to obtain the target SNR for the designated transmission, which may be signaling sent by the terminal on a control channel or some other transmission. The reference power level and the target SNR may be adjusted to obtain the desired performance level for the designated transmission, e.g., packet error rate (PER) of 1¾. If the data transmission on the traffic channel and the designated transmission observe similar noise and interference characteristics, then the received SNR for data transmission, SNR_dch(n) can be estimated as:

53 / 59P33632PL00

SNR_dch(π) = SNR_targe1 + ΔΡ (η). Equation (11)

[0061] The transmit power delta ΔΡ (η) may be adjusted in a deterministic, probabilistic or some other way based on OTA OSI reports from neighbor sectors. The transmit power may be adjusted (1) by different amounts for different interference levels using deterministic control or (2) at different rates for different levels of interference using probabilistic adjustment. Exemplary deterministic and probabilistic transmit power control schemes are described below. For simplicity, the following description relates to transmit power control for an OSI bit received from one neighbor sector. This OSI bit may be the 1 or 2 OSI bit.

[0062] In FIG. 4 shows a process 400 for adjusting the transmit power of a terminal in a deterministic manner. Initially, terminal u processes an OTA OSI report from a neighbor sector (block 412) and determines whether the OSI bit is '1' or '0' (block 414). If the OSI bit is '1', indicating that the observed interference exceeds the interference threshold, then terminal u determines the amount of transmit power reduction, or the size ΔΡ_άη(η) stepwise reduction (block 422). ΔΡ_άη(η) may be determined from the transmit power delta for the prior update interval, ΔΡ (η-Ι), and the channel gain ratio for the neighbor sector, r_ns(n). Terminal u then reduces the transmit power delta by ΔΡ_άη(η) (block 424). Conversely, if the OSI bit is '0', then terminal u determines the amount of transmit power boost, or a size ΔΡ_υρ(η) incremental increase (block 432). ΔΡ_υρ(η) can also be determined from ΔΡ (η-Ι) ir_ns(n). Terminal u then increases the transmit power delta by ΔΡ_υρ(η) (block 434). The transmit power adjustments at blocks 424 and 434 may be expressed as:

53 / 59P33632PL00 'ΔΡ (η -1) + ΔΡ_{# ρ} (η) if the OSI bit = '0', i

ΔΡ (η) = &lt;

ΔΡ (η -1) - AP_dQ(«) If the OSI bit = '1'.

Equation (12)

[0063] After blocks 424 and 434 have been implemented, terminal u limits the transmit power delta ∆Ρ (η) to be within the allowed transmit power deltas (block 442), as shown below:

ΔΡ ^ θΕΔΡ ^, ΔΡ ^],

Equation (13) where hP_mdn is the minimum transmit power delta allowed for the traffic channel, and hP_max is the maximum transmit power delta allowed for the traffic channel.

By limiting the transmit power deltas for all terminals in a sector to be within the transmit power deltas, as shown in equation (13), intra-sector interference can be kept within acceptable levels. Minimum transmit power delta hP_mdn it can be adjusted by the control loop to ensure that each terminal can meet the requirements of the quality of service (QoS) class to which the terminal belongs. hP_mdn for different QoS classes, it may be adjusted at different rates and / or with different gradation sizes.

[0064] Terminal u then calculates the transmit power P_dch(n) for a traffic channel based on the transmit power delta ΔΡ (η) and the reference power level P_ref (n) as shown in equation (10) (block 444). Terminal u may limit the transmit power P_dch(n) so as to be within the maximum power level P_max (block 446), as follows:

(PdcJn), if P ^ óOi P ^,

Ρ ^ (») = Equation (14) l Am» · ⁱⁿ another case

Terminal u uses the transmit power P._dch(n) for data transmission on the traffic channel.

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[0065] In an embodiment, the sizes of the gradual change ΔΡ_άη(η) AP_up(n) are calculated as:

ΔΡ ^ π) = ΔΡ (η-Ι), r ^ n), k_on), and Equation (15a)

ΔΡ ^ ρ (n) = /_up (AP_{up min}, ΔΡ (η -1), (n),, Equation (15b) where AP_dnfmln and AP_uPfmln are the minimum values ​​for AP, respectively_on (n) and AP_up (n);

k_on ik_up are the scaling factors for AP, respectively_on(n) and AP_up(n); a ń_on () and b_ATp () are functions for computing AP, respectively_on(n) and ΔΡ_υρ (n).

[0066] Function с_on () may be specified such that AP_on(n) is related to both ΔΡ (η-Ι) and izr_ns(n). If a neighbor sector observes high or excessive interference, then (1) a higher channel gain for the neighbor sector results in a higher AP value._on(n) and (2) the greater the value of ΔΡ (η1) results in the greater the value of ΔΡ_άη(η). Function f_up () can be defined such that ΔΡ_υρ(η) is inversely related to both ΔΡ (η-Ι) and izr_ns(n). If the neighbor sector observes low interference, then (1) a higher channel gain for the neighbor sector results in a lower value of ΔΡ_υρ(η) and (2) the greater the value of ΔΡ (η -1) results in a lower value of ΔΡ_υρ(η).

[0067] In FIG. 4 shows processing for one OSI bit from one neighbor sector. A larger value may be used for ΔΡ_άη(η), when the neighboring sector observes excessive interference. A smaller value may be used for ΔΡ_άη(η), when the neighboring sector observes high interference. Different sizes of the stepwise reduction may be obtained, e.g., by using different scaling factors k_dnl ik_dn2for high and excessive noise, respectively.

[0068] In FIG. 5 shows a process 500 for adjusting the u terminal transmit power in a probabilistic manner. Initially, terminal u processes an OTA OSI report from a neighbor sector (block 512) and determines whether the OSI bit is '1' or '0' (block

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514). If the OSI bit is '1', then terminal u determines the transmit power reduction probability, Pr_on(n), e.g. based on ΔΡ (η-Ι) ir_ns(n) (block 522). Terminal u then randomly selects a value of x between 0.0 and 1.0, where x is a random variable evenly distributed between 0.0 and 1.0 (block 524). If x is less than or equal to Pr_on(n), as determined at block 526, then terminal u decreases its transmit power delta by AP_on (block 528). Otherwise, if x is greater than Pr_on(n), then terminal u maintains the transmit power delta at the current level (block 530).

[0069] If the OSI bit is '0' in block 514, then terminal u determines the transmit power upgrade probability, Pr_up(n), e.g. based on ΔΡ (η-Ι) ir_ns(n) (block 532). Terminal u then randomly selects a value x between 0.0 and 1.0 (block 534). If x is less than or equal to Pr_up(n), as determined at block 536, then terminal u increases its transmit power delta by ΔΡ_υρ (block 538). Otherwise, if x is greater than Pr_up(n), then terminal u maintains the transmit power delta at the current level (block 530). The transmit power adjustments at blocks 528, 530, and 538 can be expressed as:

ΔΡ (η -1) - ΔΡ ^ if the OSI bit = '1' AND x&lt;Pr ^ Cn),

ΔΡ (π) = ΔΡ (η -1) + ΔΡ "_ρ , if the OSI bit = * 0 'AND x £ Pr_up(n),

Equation (16)

AP (n -1), otherwise

ΔΡ_άη and ΔΡ_υρ they may be the same values ​​(e.g., 0.25 dB, 0.5 dB, 1.0 dB, and so on) or they may be different values.

[0070] After blocks 528, 530, and 538 have been executed, terminal u constrains the transmit power delta, as shown in equation (13) (block 542). Terminal u then calculates the transmit power P._dch(n) based on the transmit power delta ΔΡ (η) and the reference power level P_ref (n) as shown in equation (10) (block 544), and further restricts transmit power P_dCh (n) so that it is within the maximum level

53 / 59P33632PL00 as shown in equation (14) (block 546). Terminal u uses the transmit power P._dch(n) for data transmission on the traffic channel.

[0071] In an embodiment, the probabilities are computed as follows:

*% □ (») = (Pr_on. ηΰί, ΔΡ (Π -1), r_ns (n), k_on), Equation (17a) i

% («) = /4(%.min· ΔΡ (η-Ι), r_m(n), k_e.g.), Equation (17b) where Pr_dnfmin and Pr_up,_min are the minimum values ​​for Pr, respectively_on(n) and Pr_up(n); and ń '_on() and ń '_up() are functions to compute Pr, respectively_on (n) and Pr_up (n).

The function ń '_on() can be defined such that Pr_on(n) is related to both ΔΡ (η-Ι) and izr_ns(n). If a neighbor sector observes large or excessive interference, then (1) a higher channel gain for the neighbor sector results in a greater Pr_on(n) and (2) the greater the value of ΔΡ (η-Ι) results in a greater Pr_on(n). Greater Pr_on(n) results in a greater likelihood of a reduction in transmit power. Function ń '_up() can be defined such that Pr_up(n) is inversely related to both ΔΡ (η-Ι) and isr_ns(n). If the neighbor sector observes low interference, then (1) more channel gain for the neighbor sector results in lower Pr_up(n) and (2) the greater the value of ΔΡ (η-Ι) results in a smaller Pr_up(n). Smaller Pr_up(n) is less likely to increase transmit power.

[0073] In FIG. 5 shows processing for one OSI bit from one neighbor sector. A larger value may be used for Pr_on(n) when a neighbor sector observes excessive interference. A smaller value may be used for Pr_on (n) when a neighbor sector observes high interference. Different reduction probabilities and therefore different rates

The power controls may be obtained, e.g., by using different scaling factors k_dnl ik_dn2for high and excessive noise, respectively.

[0074] In general, various functions may be used to calculate the AP step size_on(n) and AP_up(n) and the probabilities of Pr_on(n) and Pr_up(n). The function can be determined based on various parameters such as current transmit power, current transmit power delta, current OTA OSI report, previous OTA OSI reports, channel gain, and so on. Each function may have a different effect on the different power control characteristics, such as the rate of transmit power control convergence and distribution of transmit power deltas to terminals in the system. Gradual change sizes and probabilities may also be determined from lookup tables or some other means.

[0075] The transmit power adjustment and / or access control described above may also be performed based on QoS class, user priority class, and so on. For example, the terminal using the emergency service and the supervisor terminal may have a higher priority and may be able to adjust transmit power at a faster rate and / or with larger gradation sizes than the regular priority user. As another example, a terminal sending voice traffic may adjust transmit power at a slower rate and / or with smaller gradation sizes.

Terminal u may also change the way the transmit power is adjusted based on previous OTA OSI reports received from neighbor sectors. For example, terminal u may limit its transmit power by a particular step size and / or rate if a neighbor sector reports excessive interference, and it may limit transmit power by a larger step size and / or at a higher rate if the neighbor sector continues to report. excessive interference.

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Alternatively or additionally, terminal u may ignore -P_min in equation (13) if a neighbor sector is reporting excessive interference, or if a neighbor sector continues to report excessive interference.

[0077] Various embodiments of power control to reduce inter-sector interference have been described above. The interference control and the power control may also be performed in other ways and are within the scope of the invention.

[0078] In an embodiment, each sector broadcasts its OTA OSI report to terminals in neighbor sectors as described above. The OTA OSI report may be broadcast with sufficient transmit power to obtain the desired coverage area in adjacent sectors. Each terminal can receive OTA OSI reports from neighboring sectors and process these OTA OSI reports in such a way as to obtain a sufficiently small defective detection ratio and a sufficiently low false alarm probability. Defective Detection refers to a failure to detect an OSI bit or value that has been transmitted. A false alarm is related to the erroneous detection of the received bit or OSI value. For example, if the OSI bit is transmitted using BUSK, then the terminal may declare that the received OSI bit: (1) is '0', if the detected OSI bit is below the first threshold, the OSI bit &lt;-B_volh, (2) is '1', if the detected OSI bit exceeds the second threshold, the OSI bit&gt; + B_volh, and (3) is otherwise a blank bit, + B_volh - OSI bit 1 -B_volh · The terminal can usually reconcile the ratio of failed detections with the probability of false alarm by adjusting the thresholds used for detection.

[0079] In another embodiment, each sector also broadcasts OTA OSI reports generated by neighbor sectors to terminals within its sector. Each sector thus acts as an intermediary for neighboring sectors. This embodiment can ensure that each terminal can reliably

Receive OTA OSI reports generated by neighbor sectors, as the terminal can receive these OTA OSI reports from the serving sector. This embodiment is well suited for use in an asymmetric network where sector coverage sizes are not equal. Smaller sectors typically transmit at lower power levels, and OTA OSI reports broadcast by these smaller sectors may not be reliably received by terminals in neighboring sectors. Smaller sectors would then benefit from broadcasting their OTA OSI reports by neighboring sectors.

[0080] Generally, a given sector m may broadcast OTA OSI reports generated by any number and any of the other sectors. In an embodiment, sector m broadcasts OTA OSI reports generated by sectors in the neighbor list for sector m. The neighbor list may be created by the network operator or some other way. In another embodiment, sector m broadcasts OTA OSI reports generated by all sectors that are included in active terminal sets in sector m. Each terminal may maintain an active set that includes all sectors with which the terminal is in communication. Sectors may be added to or removed from the active set as the terminal is handed over from one sector to another. In yet another embodiment, sector m broadcasts OTA OSI reports generated by all sectors that are included in potential terminal sets in sector m. Each terminal may maintain a potential set that includes all sectors with which the terminal may communicate. Sectors may be added to or removed from a potential set, e.g., based on channel gain and / or some other parameter. In yet another embodiment, sector m broadcasts OTA OSI reports generated by all sectors that are included in the terminal OSI sets in sector m. The OSI set for each terminal may be determined as described above.

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[0081] As indicated above, the system may use only user based interference control or only network based interference control. User-based interference control may be easier to implement as each sector and each terminal can operate independently. Network-based disturbance control can provide better performance because the disturbance control is performed in a coordinated manner. The system may also use both user based interference control and network based interference control at the same time. The system may also use user based interference check each time, and may invoke network based interference check only if excessive interference is observed. The system can also call up any kind of disturbance check for various operating conditions.

[0082] In FIG. 6 shows a power control mechanism 600 that may be used to adjust transmit power for terminal 120x in system 100. Terminal 120x communicates with serving sector 110x and may interfere with adjacent sectors HOa through 1101. Power control mechanism 600 includes (1) a reference loop 610 that operates between terminal 120x and serving sector 110x and (2) a second loop 620 that operates between terminal 120x and adjacent sectors HOa through 1101. Reference loop 610 and second loop 620 may be run simultaneously, but may be updated at different rates, with reference loop 610 being a faster loop than second loop 620. For simplicity, in FIG. 6 only a portion of the loops 610 and 620 in terminal 120x are shown.

[0083] Reference loop 610 adjusts the reference power level P_ref (n) such that the received SNR for the designated transmission, measured in the serving sector 110x, is as close as possible to the target SNR. For reference loop 610, serving sector 110x estimates the received one

The SNR for the designated transmission, compares the received SNR with the target SNR, and generates transmit power control (TPC) commands based on the results of the comparison. Each TPC command may be either (1) a INCREASE command to control an increase in the reference power level or (2) a DECREASE command to control a decrease in the reference power level. Serving sector 110x transmits TPC commands on the forward link (cloud 670) to terminal 120x.

[0084] At terminal 120x, a TPC command processor 642 detects TPC commands transmitted by serving sector 110x and provides TPC decisions. Each TPC decision may be a decision of INCREASE, if the received TPC command is recognized as an INCREASE order, or a decision of DECREASE, if the received TPC command is considered to be a DECREASE order. Reference power control unit 644 adjusts the reference power level based on the TPC decision. Entity 644 can increase P_ref (n) by a gradual increase for each INCREASE decision and decrease P_ref (n) by a progressive decrease for each DECOMMEND decision. A transmit data (TX) processor 660 scales the determined transmission to obtain a reference power level. Terminal 120x sends the designated transmission to serving sector 110x.

[0085] Due to path losses, fading, and multiple path interactions on the reverse link (cloud 640), which typically vary with time and particularly for a mobile terminal, the received SNR for the designated transmission continuously fluctuates. Reference loop 610 attempts to keep the received SNR for the designated transmission equal to or near the target SNR in the presence of uplink channel condition changes.

[0086] The second loop 620 controls the transmit power P_dch (n) for the traffic channel assigned to terminal 120x such that a power level as high as possible is used

53 / 59P33632PL00 for the traffic channel while keeping inter-sector interference within acceptable levels. For the second loop 620, each neighbor sector 110 receives reverse link transmissions, estimates the inter-sector interference observed by the neighbor sector from terminals in other sectors, generates an OTA OSI report based on the interference estimate, and broadcasts the OTA OSI report to the terminals in other sectors.

[0087] At terminal 120x, the OSI report processor 652 receives OTA OSI reports broadcast by neighboring sectors and provides detected OSI reports to the transmit power delta calculation unit 656. Channel estimator 654 receives pilots from the serving and neighboring sectors, estimates the channel gain for each sector, and provides the estimated channel gains for all sectors to unit 656. Unit 656 determines channel gain ratios for adjacent sectors and further adjusts the transmit power delta ∆Ρ (η) based on the detected OSI reports and channel gain ratios as described above. Unit 656 may implement the processes 300, 400, and / or 500 shown in FIG. 3 through 5. Transmit power calculation unit 658 calculates transmit power P_dch(n) on the basis of the reference transmit level P_ref (n) from unit 644, transmit power delta ΔΡ (η) from unit 656, and possibly other factors. TX data processor 660 uses the transmit power P_dch(n) for transmitting data to serving sector 110x.

[0088] In FIG. 6 shows an exemplary power control mechanism that may be used for interference control. The interference check may also be performed in other ways and / or with other parameters than those described above.

[0089] In FIG. 7 is a block diagram of an embodiment of a terminal 120x, serving base station 110x and neighbor base stations IlOy. For preservation

For clarity, the following description assumes use of the power control mechanism 600 shown in FIG. 6.

[0090] On the uplink, at terminal 120x, the TX data processor 710 encodes, interleaves, and symbol maps uplink traffic (RL) data and control data and provides data symbols. A modulator (Mod) 712 maps data symbols and pilot symbols to the appropriate subbands and symbol periods, performs OFDM modulation, if applicable, and provides a sequence of complex valued chips. The transmitter unit (TMTR) 714 conditions (e.g. analog converts, amplifies, filters, and frequency-upconverts the chip sequence and generates an uplink signal that is transmitted via antenna 716.

[0091] At the serving base station 110x, multiple antennas 752xa through 752xt receive uplink signals from terminal 120x and other terminals. Each antenna 752x delivers a received signal to a corresponding receiver unit (RCVR) 754x. Each receiver unit 754x conditions (e.g., filters, amplifies, downconverts, and digitizes) its received signal, performs OFDM demodulation, if applicable, and provides the received symbols. RX spatial processor 758 performs receiver spatial processing on the received symbols from all receiver units and provides data symbol estimates that are estimates of transmitted data symbols. RX data processor 760x performs demapping, deinterleaves and decodes the data symbol estimates, and provides decoded data for terminal 120x and other terminals currently served by base station 110x.

[0092] The processing for a forward link transmission may be performed similar to the processing described above for a reverse link. The processing for transmissions on the forward and reverse links is typically determined by the system.

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For interference control and power control, at serving base station 110x, RX spatial processor 758x estimates a received SNR for terminal 120x, estimates inter-sector interference observed by base station 110x, and provides an SNR estimate for terminal 110x and an interference estimate (e.g. measured disturbances I._meas, m) to the 770x controller. Controller 770x generates TPC commands for the terminal 120x based on the estimated SNR for the terminal and the target SNR. Controller 770x may generate an OTA OSI report and / or an IS OSI report based on the interference estimate. Controller 770x may also receive IS OSI reports from neighbor sectors via a communication unit (Comm) 774x. TPC commands, OTA OSI report to base station 110x, and possibly OTA OSI reports to other sectors are processed by TX data processor 782x and TX spatial processor 784x, conditioned by transmitter units 754xa through 754xt and transmitted via antennas 752xa through 752xt. An IS OSI report from base station 110x may be sent to neighbor sectors via communication unit 774x, e.g. over a backhaul or other wired communication link.

[0094] At neighbor base station HOy, RX spatial processor 758y estimates the inter-sector interference observed by base station HOy and provides an interference estimate to controller 770y. Controller 770y may generate an OTA OSI report and / or an IS OSI report based on the interference estimate. The OTA OSI report is processed and broadcast to the terminals on the system. The IS OSI report may be sent to neighbor sectors via communication unit 774y.

[0095] At terminal 120x, antenna 716 receives downlink signals from serving and neighbor base stations and provides the received signal to receiver unit 714.

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The received signal is conditioned and digitized by receiver unit 714 and additionally processed by demodulator (Demod) 742 and RX data processor 744. Processor 744 provides TPC commands sent by serving base station 110x for terminal 120x and OTA OSI reports broadcast by neighbor base stations. A channel estimator within demodulator 742 estimates the channel gain for each base station. Controller 720 detects received TPC commands and updates the reference power level based on the TPC decision. Controller 720 also adjusts the transmit power for the traffic channel based on OTA OSI reports received from neighbor base stations and channel gains for serving and neighbor base stations. Controller 720 provides transmit power for the traffic channel assigned to terminal 120x. Processor 710 and / or modulator 712 scales the data symbols based on transmit power provided by controller 720.

[0096] Controllers 720, 770x, and 770y direct the operation of various processing units at terminal 120x and base station 110x and IlOy, respectively. These controllers may also perform various functions for disturbance control and power control. For example, controller 720 may implement any or all of units 642 through 658 shown in FIG. 6 and / or the processes 300, 400, and / or 500 shown in FIG. from 3 to 5. Controller 770 for each base station 110 may implement all or part of the process 200 in FIG. 2. Memory units 722, 772x, and 772y store data and program codes for controllers 720, 770x, and 770y, respectively. Scheduler 780x schedules terminals for communication with base station 110x, and also assigns traffic channels to scheduled terminals, e.g., based on IS OSI reports from neighbor base stations.

[0097] In FIG. 8 shows a device suitable for interference control. The apparatus includes means 800 for receiving IS OSI report (s) and means 802 for adjusting

Data transmissions for terminals in the sector based on received IS OSI reports.

[0098] In FIG. 9 shows a device suitable for providing interference control. The apparatus includes means 900 for generating IS OSI report (s) and means 902 for transmitting IS OSI reports to one or more sectors. In some cases, the generating means may include means for generating a different IS OSI report for each sector, and the transmitting means may be connected to a wired connection, e.g., a backhaul link.

[0099] The interference control methods described herein may be implemented by a variety of means. For example, these methods may be implemented on a hardware platform, with software, or a combination thereof. For a hardware implementation, the processing units used to implement interference control at the base station may be implemented in one or more specialized integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices ( PLD), directly programmable gate arrays (FPGA), processors, controllers, microcontrollers, microprocessors, electronic devices, Other electronic units designed to perform the functions described herein, or combinations thereof. The processing units used to perform interference control at the terminal may also be implemented in one or more ASICs, DSPs, processors, electronic devices, and so on.

[0100] For a software implementation, the interference control methods may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. Software codes can be

53 / 59P33632PL00 stored in a memory unit (e.g., memory unit 722, 722x, or 722y in FIG. 7) and executed by a processor (e.g., controller 720, 770x, or 770y). The memory unit may be implemented within or outside the processor. [0101] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not to be limited to the embodiments described herein, but is to be understood as broadly as possible consistent with the principles and novel features set forth herein.

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