HK1104750A - Intra-cell common reuse for a wireless communication system - Google Patents

Description

Intra-cell common reuse for wireless communication systems

Cross Reference to Related Applications

Priority of the present application to U.S. provisional patent application No.60/578,214, filed on 8.6.2004, is hereby incorporated by reference in its entirety.

Technical Field

The present invention relates generally to communications, and more particularly to data transmission in a wireless communication system.

Background

A multiple-access system may concurrently support communication for multiple terminals on the forward and reverse links. 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 may be achieved by multiplexing the data transmissions on each link to be orthogonal to each other in the time, frequency and/or code domain. Orthogonality ensures that data transmission for each terminal does not interfere with data transmission for other terminals.

Typically, a multiple access system has many cells, where the term may refer to a base station and/or its coverage area depending on the context in which the term "cell" is used. To increase capacity, the coverage of each base station may be partitioned into multiple (e.g., 3) sectors by using an appropriate antenna pattern. Each sector is served by a Base Transceiver Subsystem (BTS). Typically, the BTSs for all sectors in the same cell are located within the base station for that cell, and these sectors may be considered co-located. In general, the term "sector" can refer to a BTS and/or its coverage area depending on the context in which the term is used.

In sectorized systems, the sectors of each cell typically utilize the same frequency band. Then the data transmission in each sector of a given cell represents potential interference to data transmissions in other sectors of the same cell. Typically, interference isolation between multiple sectors of the same cell is achieved by controlling the antenna pattern for each sector such that the antenna gain drops rapidly outside the expected coverage area of that sector. Typically, however, the edge of each sector overlaps the edge of the adjacent sector. Then a terminal located on the border between two sectors of the same cell may observe very high "intra-cell" interference from neighboring sectors. This interference can substantially degrade performance.

There is therefore a need in the art for techniques to mitigate the deleterious effects of intra-cell interference for terminals located on the boundaries between sectors of the same cell.

Disclosure of Invention

Techniques for efficiently avoiding or reducing intra-cell interference for terminals within a cell are described herein. These techniques are referred to as "intra-cell common reuse" techniques and may be used in various wireless communication systems and on both the forward and reverse links. With intra-cell common reuse, each sector of a cell is associated with a set of sector-specific system resources and at least one set of common system resources. The system resources may be subbands, time slots, etc. The sector-specific set for each sector is non-overlapping with the at least one common set for the sector and includes system resources that are different from the at least one common set for the sector. Each common set for each sector includes system resources that observe little or no interference from at least one other sector in the cell. As described below, different common sets may be defined for different embodiments of intra-sector common reuse.

To allocate system resources to a terminal within a given sector x, the channel condition for the terminal is first determined based on, for example, forward link measurements made by the terminal for different sectors and/or reverse link measurements made by different sectors for the terminal. System resources are allocated for a terminal from either the common set for sector x or the sector-specific set based at least on the channel conditions for the terminal. For example, if a terminal observes high interference from another sector y, system resources may be allocated for the terminal from a common set that observes little or no interference from sector y. Resources may also be allocated for a terminal from the common set if the terminal is in a "softer" handoff and is communicating with both sectors x and y. In any case, the data transmission for the terminal is sent on the forward and/or reverse link using the allocated system resources.

Intra-cell common reuse may be used for Orthogonal Frequency Division Multiple Access (OFDMA) systems utilizing Orthogonal Frequency Division Multiplexing (OFDM). For an OFDMA system, each common set and each sector-specific set includes a plurality of subbands, and the terminal may be assigned one or more subbands for data transmission. For a frequency hopping OFDMA (FH-OFDMA) system, multiple orthogonal FH patterns may be formed for each common set and each sector-specific set. The terminal may be assigned one FH pattern in a set for data transmission.

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

Drawings

The features and characteristics of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like or similar reference characters identify correspondingly throughout, and wherein:

fig. 1 illustrates a wireless communication system;

FIG. 2 shows an exemplary antenna pattern for a sector;

FIG. 3A shows a cell with 3 sectors;

fig. 3B illustrates the intra-cell interference observed by two users within a cell;

fig. 4 shows a common set and a sector-dedicated set for a first embodiment of intra-cell common reuse;

figures 5A to 5D show 3 common sets and 3 sector-specific sets for a second embodiment of intra-cell common reuse;

fig. 6A to 6D show 4 common sets and 3 sector-dedicated sets for a third embodiment of intra-cell common reuse;

figure 7 shows the distribution of 8 users within 3 sectors of a cell;

8A, 8B and 8C show the formation of common and sector-specific sets for the first, second and third embodiments of intra-cell common reuse, respectively;

FIG. 9 illustrates a frequency hopping scheme;

fig. 10 shows a process for data transmission with intra-cell common reuse;

FIG. 11 shows a process for allocating subbands to terminals;

FIG. 12 shows a process for transmitting data on the assigned subbands;

FIG. 13 shows a process for receiving data on the assigned sub-bands; and

fig. 14 shows two base stations, one cell entity and one terminal.

Detailed Description

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

The intra-cell common reuse techniques described herein may be used for various wireless multiple-access communication systems. For clarity, these techniques are described for an OFDMA system utilizing OFDM. OFDM effectively partitions the overall system bandwidth into multiple (N) orthogonal subbands, which may also be referred to as tones (tones), subcarriers, bins (bins), frequency channels, and so on. Each subband is associated with a respective subcarrier, which may be modulated with data.

Fig. 1 shows an exemplary OFDMA system 100 having multiple base stations 110 supporting communication for multiple wireless terminals 120. A base station is a fixed station used for communicating with the terminals and may also be referred to as an access point, a node B, or some other terminology. Terminals 120 are typically dispersed throughout the system, and each terminal may be fixed or mobile. A terminal may also be called a mobile station, User Equipment (UE), a wireless communication device, or some other terminology. Each terminal may communicate with one or possibly multiple base stations on the forward and reverse links at any given moment. For a centralized architecture, a system controller 130 connects to and provides coordination and control for the base stations. For a distributed architecture, for example, the base stations can communicate with one another as needed to service terminals, adjust the use of system resources, and so forth.

Each base station 110 provides communication coverage for a respective geographic area. The coverage area of each base station may be partitioned into multiple (e.g., 3) sectors by using a directional antenna pattern.

Fig. 2 shows an exemplary antenna pattern 210 for one sector. The antenna pattern shows normalized antenna gain at different angular positions, where the normalization results in a maximum antenna gain of 0 decibels (dB). Antenna pattern 210 has a main lobe with a-3 dB beamwidth of approximately 65 degrees.

Fig. 3A shows a cell 310 having 3 sectors 312a, 312b, and 312c, the 3 sectors being labeled as sectors 1, 2, and 3, respectively. Each sector may be defined by a respective antenna pattern 210. The main lobes of the 3 antenna patterns for the 3 sectors may be directed at 120 horizontal angles from each other. By using the proper antenna pattern, the interference isolation between these sectors is good for most users in 3 sectors.

Fig. 3B shows the intra-cell interference observed by two users u and v within cell 310, which uses the 65 deg. antenna pattern shown in fig. 2. User u is located at a horizontal angle of 132.5 deg. from sector and has an antenna gain of-3 dB for sector 1. User u also has an antenna gain of-18 dB for sector 2, which is at the 87.5 ° horizontal angle, and an antenna gain of-31 dB for sector 3, which is at the 152.5 ° horizontal angle. The intra-cell interference observed by user u from sectors 2 and 3 is 14.8dB lower than the desired signal level observed from sector 1. User v is located at a horizontal angle of 160 deg. from sector 1 and on the boundary between sectors 3. It can be seen that the intra-cell interference observed by user v is above the desired signal level.

In general, the coverage area of each base station may be any size and shape, and may depend on various factors such as terrain, obstacles, and the like. The size and shape of each sector depends on the antenna pattern used for that sector, among other factors. Typically, the sectors of a cell overlap at the edges to ensure good communication coverage for the cell and to facilitate handovers between sectors. A cell/sector may or may not be a contiguous area and the cell/sector edges may be very complex.

Each sector is typically served by a BTS. Typically, the BTSs for all sectors of the same cell are located within the base station for that cell. For simplicity, in the following description, the term "base station" is generally directed to a fixed station that serves a cell and a fixed station that serves a sector. A "serving" base station or "serving" sector is one base station or sector with which a terminal communicates. The terms "terminal" and "user" may also be used interchangeably herein.

In an OFDMA system, users with different channel conditions may be distributed throughout each cell. These users may have different contributions and tolerances to the intra-cell interference. The channel condition for each user may be quantified by received pilot strength, received pilot power, channel gain, signal-to-interference-and-noise ratio (SINR), and/or some other measure for one or more sectors. Typically, users located at the edge of a sector (or simply "sector-edge users") have poor channel conditions, e.g., low SINR for the serving sector due to low channel gain for the sector, high intra-cell interference, etc. In general, sector-edge users are less tolerant of intra-cell interference, cause more interference to other users in neighboring sectors, have poor performance, and may be a bottleneck in systems that impose fairness requirements.

Intra-cell common reuse techniques may avoid or reduce interference observed by sector-edge users. With intra-cell common reuse, user u, located at the boundary of multiple sectors, is assigned multiple subbands that are orthogonal to those assigned to other users in those sectors. User u will then observe little or no intra-cell interference from these other users and improved performance will be available. Various embodiments of intra-cell common reuse are described below.

Fig. 4 shows a venturi diagram of common subband sets and sector-specific subband sets according to a first embodiment of intra-cell common reuse. The common set is labeled C and is represented by a circle with white fill. The sector specific set is marked S and is indicated by the area with diagonal lines. Common set C contains subbands that are common to all sectors of the cell. Sector-specific set S contains subbands that each sector may assign to its users. The subbands in sets C and S are taken from the full set of all subbands available for data transmission. Since each usable subband belongs only to set C or S, the common set C and the sector-specific set S are non-overlapping (i.e., do not intersect or are mutually exclusive).

The common and sector-specific sets may be defined as:

formula (1) where S is Ω \ C and S ═ C is Θ

Wherein "\\" represents a difference set operation;

"D" represents an intersection operation;

"Ω" represents a complete set containing all available subbands; and

"Θ" represents an empty set.

Common set C contains subbands selected from a total of N subbands in the system. As described below, to achieve frequency diversity, the subbands in common set C may be distributed across a total of N subbands. The sector-specific set S may be formed by a difference set operation between the full set Ω and the common set C. The size of the common set may be selected based on various factors such as the desired number of sector-edge users, the desired overall spectral efficiency of the cell, and so on. The size of the common set may be selected to achieve efficient use of system bandwidth while providing reduced interference for a significant number of users.

Each sector may assign subbands in the sector-specific set S to its users observing good or fair channel conditions. The subbands in common set C may be assigned to weak users observing poor channel conditions. One sector in a cell or the cell itself may be designated to allocate subbands in common set C to all weak users in the cell. Each subband in the common set is allocated to only one user in the cell. Since sets C and S are non-overlapping, weak users assigned subbands in common set C will observe little or no interference from other users assigned subbands in sector-specific set S.

Each sector may have strong users with good channel conditions and high SINR. These strong users may be adequately served with low power transmission on the forward and/or reverse links. Each sector may assign subbands in common set C to its strong users and may control or limit the use of these subbands to avoid causing excessive interference to the weak users assigned these subbands. For example, data transmission for strong users on the common intra-set subbands may be limited to below a predetermined transmit power limit.

The common set C may be used to support users in "softer" handovers. Softer handoff refers to the process of a user communicating with multiple sectors of the same cell at the same time. Softer handoff may provide diversity gain due to data transmission or reception to multiple sectors via different signal paths. Softer handoff may be supported on the forward link, the reverse link, or both.

If a given user u is assigned subbands in common set C, forward link traffic/packet data for user u may be transmitted from one or more sectors in the same cell. If traffic data is transmitted from a single sector, the subbands assigned to user u may be reused in other sectors, as long as sufficient interference isolation can be obtained for user u from other users assigned the same subbands. User u benefits from the diversity gain obtained via multiple transmissions if traffic data for user u is transmitted from multiple sectors for softer handoff.

If user u is transmitting on the reverse link, then the reverse link data transmission from user u may be received and decoded by one or more sectors within the same cell. Since the sectors are co-located, the soft-decision symbols obtained by the sectors for user u can be combined and subsequently decoded to improve decoding performance. This is commonly referred to as joint decoding. User u benefits from the diversity gain achieved by the multiple sectors receiving the reverse link transmission from user u if joint decoding is performed. The subbands assigned to user u may be reused in other sectors if no joint decoding is performed. Other users with the same subbands as assigned to user u may cause negligible interference to user u on the reverse link.

Referring back to fig. 3B, user v is located on the boundary between sectors 1 and 3 and may observe little interference from sector 2. Similarly, users located on the boundary between sectors 1 and 2 may observe little interference from sector 3, while users located on the boundary between sectors 2 and 3 may observe little interference from sector 1. Improved bandwidth utilization may be obtained by defining a common set for pairs of sectors rather than all sectors.

FIG. 5A shows a Venturi diagram of 3 common subband sets, labeled C, according to a second embodiment of intra-cell common reuse₁₂、C₁₃And C₂₃. For this embodiment, the 3 common sets do not overlap with each other. Common set C₁₂Comprising subbands common to sectors 1 and 2 of the same cell, common set C₁₃Contains subbands that are common to sectors 1 and 3, and has a common set C₂₃Containing subbands common to sectors 2 and 3.

For each sector x, a sector-specific set S may be defined for sector x_xSo that it is common to both sets C for sector x_xyAnd C_xzAnd (2) no overlapping, wherein x belongs to {1, 2, 3}, y belongs to {1, 2, 3}, z belongs to {1, 2, 3}, x is not equal to y, x is not equal to z, and y is not equal to z. Sector specific set C_xMay contain all not included in the common set C_xyAnd C_xzAvailable sub-bands in (1). The common set and sector-specific set for sector x may be defined as:

S_x＝Ω\(C_xy∪C_xz) And C_xy∩C_xz∩C_yzΘ formula (2)

FIG. 5B shows a common set C for sector 1₁₂And C₁₃And sector specific set S₁The venturi diagram of (a). Each common set C is represented by a circle with white fill₁₂And C₁₃. The sector-specific set S is represented by an area with diagonal lines₁. Sector specific set S₁Containing the full set omega not included in the common set C₁₂And C₁₃All sub-bands in (1). Sector 1 may dedicate sectors to set S₁The subbands in (a) are assigned to strong and fair users who are located in the sector and observe good or fair channel conditions.

FIG. 5C shows a common set C for sector 2₁₂And C₂₃And sector specific set S₂The venturi diagram of (a). Sector specific set S₂Containing the full set omega not included in the common set C₁₂And C₂₃All sub-bands in (1). Sector 2 may dedicate sectors to set S₂The subbands in (a) are assigned to strong and fair users in the sector.

FIG. 5D shows a common set C for sector 3₁₃And C₂₃And sector specific set S₃The venturi diagram of (a). Sector specific set S₃Containing the full set omega not included in the common set C₁₃And C₂₃All sub-bands in (1). Sector 3 may dedicate sectors to set S₃The subbands in (a) are assigned to strong and fair users in the sector.

For fig. 5B through 5D, common set C may be used₁₂The subbands in (a) are assigned to weak users located on the boundary between sectors 1 and 2. May be a common set C₁₃The subbands in (a) are assigned to weak users located on the boundary between sectors 1 and 3. May be a common set C₂₃The subbands in (b) are assigned to weak users located on the boundary between sectors 2 and 3.

For a second embodiment of intra-cell common reuse, common set C_xySubband and sector specific set S in_xAnd S_yThe subbands in (1) are orthogonal. Thus, weak users located on the boundary between sectors x and y may be assigned a common set C_xyAnd then the weak user will observe little or no data from the assigned sector-specific set S_xAnd S_yInter-cell interference of other users of the sub-band in (b). The second embodiment of intra-cell common reuse can also improve bandwidth utilization. Common set C_xyIs included in the sector-specific set S_zAnd may be a common set C_xyThe subbands in (b) are assigned to strong and fair users in sector z.

In an alternative second embodiment, sectors are dedicated to set S₁₂₃Defined as containing the full set omega not included in the 3 common sets C₁₂、C₁₃And C₂₃All subbands in (b), as follows:

S₁₂₃＝Ω\(C₁₂∪C₁₃∪C₂₃) Formula (3)

Each sector x may dedicate a sector to a set S₁₂₃The sub-bands in (1) are allocated to its strong and fair users. Can be combined with a common set S_xyCan be assigned to weak users located on the boundary between sectors x and y, and a common set S can be assigned_xzThe subbands in (b) are assigned to weak users located on the boundary between sectors x and z. Sector x may be a common set S_yzIs assigned to a strong user who will be located on the boundary between sectors y and z and assigned the common set S_yzThe weak users of the sub-band in (b) cause negligible interference.

A user may observe high interference from two other sectors. A common set may be defined to serve that user at a disadvantage while achieving good bandwidth utilization.

FIG. 6A shows 4 common subband sets C according to a third embodiment of intra-cell common reuse₁₂、C₁₃、C₂₃And C₁₂₃The venturi diagram of (a). Common set C₁₂Comprising subbands common to sectors 1 and 2 of the same cell, common set C₁₃Containing subbands common to sectors 1 and 3, common set C₂₃Contains subbands that are common to sectors 2 and 3, and has a common set C₁₂₃Containing subbands that are common to all 3 sectors 1, 2, and 3.

For each sector x, a sector-specific set S may be defined for sector x_xTo be associated with 3 common sets C for sector x_xy、C_xzAnd C_xyzDo not overlap. Sector specific set S_xMay contain data not included in the common set C_xy、C_xzAnd C_xyzAll usable subbands in the set. The common set and sector-specific set for sector x may be defined as:

S_x＝Ω\(C_xy∪C_xz∪C_xyz) And C_xy∩C_xz∩C_yz∩C_xyzΘ formula (4)

FIG. 6B shows a common set C for sector 1₁₂、C₁₃And C₁₂₃And sector specific set S₁The venturi diagram of (a). The common set C is represented by an area having vertical lines₁₂The common set C is represented by areas with lattices₁₃Common set C by circles with white fill₁₂₃And the sector exclusive set S is represented by an area with diagonal lines₁. Sector specific set S₁Containing the full set omega not included in the common set C₁₂、C₁₃And C₁₂₃All sub-bands in (1). Sector 1 may dedicate sectors to set S₁The subbands in (a) are assigned to strong and fair users in the sector.

FIG. 6C shows a common set C for sector 2₁₂、C₂₃And C₁₂₃And sector specific set S₂The venturi diagram of (a). Sector specific set S₂Containing the full set omega not included in the common set C₁₂、C₂₃And C₁₂₃All sub-bands in (1). Sector 2 may dedicate sectors to set S₂The subbands in (a) are assigned to strong and fair users in the sector.

FIG. 6D shows a common set C for sector 3₁₃、C₂₃And C₁₂₃And sector specific set S₃The venturi diagram of (a). Sector specific set S₃Containing the full set omega not included in the common set C₁₃、C₂₃And C₁₂₃All sub-bands in (1). Sector 3 may dedicate sectors to set S₃The subbands in (a) are assigned to strong and fair users in the sector.

For fig. 6B through 6D, common set C may be used₁₂The subbands in (a) are assigned to weak users located on the boundary between sectors 1 and 2. May be a common set C₁₃The subbands in (a) are assigned to weak users located on the boundary between sectors 1 and 3. Can be combined withCommon set C₂₃The subbands in (b) are assigned to weak users located on the boundary between sectors 2 and 3. May be a common set C₁₂₃The subbands in (a) are assigned to weak users located on the boundary between all 3 sectors 1, 2, and 3.

For a third embodiment of intra-cell common reuse, common set C_xySubband and sector specific set S in_xAnd S_yThe subbands in (1) are orthogonal. A weak user located on the boundary between sectors x and y may be assigned a common set C_xyAnd then the weak user will observe little or no data from the assigned sector-specific set S_xAnd S_yInter-cell interference of other users of the sub-band in (b). Common set C_xyzSubband and sector specific set S in_x、S_yAnd S_zThe subbands in (1) are orthogonal. A common set C may be assigned to weak users located on the boundary between all 3 sectors x, y and z_xyzAnd then the weak user will observe little or no data from the assigned sector-specific set S_x、S_yAnd S_zInter-cell interference of other users of the sub-band in (b). The third embodiment can also improve bandwidth utilization. Common set C_xyIs included in the sector-specific set S_zAnd may be a common set C_xyThe subbands in (b) are assigned to strong and fair users in sector z. Sector x may also have a common set S_yzIs assigned to a strong user who will be located on the boundary between sectors y and z and is also assigned set S_yzThe weak users of the sub-band in (b) cause negligible interference.

Fig. 7 shows an example of the distribution of 8 users in 3 sectors of a single cell. Fig. 7 also shows subband allocation for a third embodiment based on intra-cell common reuse. In this example, user a is located in sector 1 and is assigned a sector-specific set S₁Of (2). User b is located between sector 1 and sector 2 and is assigned a common set C₁₂Of (2). Users c and d are located in sector 2 and are assigned a sector-specific set S₂Seed of ChineseA belt. User e is located between sector 2 and sector 3 and is assigned a common set C₂₃Of (2). User f is located in sector 3 and is assigned a sector-specific set S₃Of (2). User g is located between sector 1 and sector 3 and is assigned a common set C₁₃Of (2). User h is located between sectors 1, 2 and 3 and is assigned a common set C₁₂₃Of (2).

The common set and the sector-dedicated set may be formed in various ways. For an OFDMA system, a total of N subbands created by OFDM are available. Traffic data, pilot, and signaling may be transmitted using all or a subset of the N total subbands. Typically, some subbands are not used for transmission but are used as guard subbands to make the system meet spectral mask (spectral mask) requirements. For simplicity, the description below assumes that all N total subbands are available for transmission, i.e., no guard subbands.

Fig. 8A shows an example for constructing a common set C and a sector-specific set S for the first embodiment of intra-cell common reuse. In this example, a total of N subbands are arranged into M groups, each group containing L subbands, where M ≧ 1, L > 1, and M · L ═ N. Common set C contains one (e.g., the first) subband in each group. The sector-specific set S contains the remaining subbands in each group. In general, a common set may contain any number of subbands and any one of the total N subbands. To achieve frequency diversity, the common set may contain subbands taken from a total of N subbands. The subbands in the common set may be distributed across a total of N subbands based on a predetermined pattern (e.g., as shown in fig. 8A) or pseudo-randomly distributed across a total of N subbands.

Fig. 8B shows a second embodiment for forming a common set C for intra-cell common reuse₁₂、C₁₃And C₂₃And sector specific set S₁、S₂And S₃Examples of (3). In this example, a total of N subbands are arranged into M groups as described above for fig. 8A. Common set C₁₂Containing the first subband in each group, common set C₁₃Comprises in each groupOf the second sub-band, and a common set C₂₃Containing the third subband in each group. In general, each common set may contain any number of subbands and any one of a total of N subbands, subject to the constraint that no two common sets contain the same subbands. These common sets may contain the same number of subbands (as shown in fig. 8B) or different numbers of subbands. The number of subbands in each common set may depend on various factors, such as the desired number of weak users assigned to the common set. To achieve frequency diversity, each common set may contain subbands taken from a total of N subbands (e.g., uniformly or pseudo-randomly distributed across the total of N subbands).

Sector specific set S₁Containing not included in the common set C₁₂And C₁₃All usable subbands in the set. Sector specific set S₂Containing not included in the common set C₁₂And C₂₃All usable subbands in the set. Sector specific set S₃Containing not included in the common set C₁₃And C₂₃All usable subbands in the set.

Fig. 8C shows a third embodiment for forming a common set C for intra-cell common reuse₁₂、C₁₃、C₂₃And C₁₂₃And sector specific set S₁、S₂And S₃Examples of (3). In this example, a total of N subbands are arranged into M groups as described above for fig. 8A. Common set C₁₂Containing the first subband in each group, common set C₁₃Containing the second subband in each group, common set C₂₃Containing the third subband in each group, and a common set C₁₂₃Containing the fourth subband in each group. In general, each common set may contain any number of subbands and any one of a total of N subbands, subject to the constraint that no two common sets contain the same subbands. Sector specific set S₁Containing not included in the common set C₁₂、C₁₃And C₁₂₃All usable subbands in the set. Sector specific set S₂Containing not included in the common set C₁₂、C₂₃And C₁₂₃All of the available ones in (1)A belt. Sector specific set S₃Containing not included in the common set C₁₃、C₂₃And C₁₂₃All usable subbands in the set.

The common set and the sector-specific set may be defined in various ways. In one embodiment, the common set and the sector-specific set are static and do not change or change at a low rate. In another embodiment, the common set and the sector-specific sets may be dynamically defined based on sector loading and possibly other factors. For example, the common set for each sector may depend on the number of weak users within the sector, which may change over time. The designated sector or cell may receive load information for various sectors, define common and sector-specific sets, and inform the sectors of these sets. This embodiment may allow for better utilization of system resources based on the distribution of users.

To facilitate assignment of subbands to terminals, multiple orthogonal "traffic" channels may be defined for each (common or sector-specific) subband set. For a given set of subbands, each subband is used for only one traffic channel in any given time interval, and each traffic channel may be assigned 0, 1, or more subbands in each time interval. The traffic channels for each sector-specific set do not interfere with each other and do not interfere with the traffic channels for the common set that does not overlap with that sector-specific set. Similarly, the traffic channels for each common set do not interfere with each other and do not interfere with the traffic channels for the sector-specific sets that do not overlap with the common set. Traffic channels may be viewed as a convenient way of representing the sub-band assignments for different time intervals. A traffic channel for the appropriate (common or sector-specific) subband set may be assigned to a user depending on the channel condition of the user.

The OFDMA system may or may not use Frequency Hopping (FH). With frequency hopping, data transmission hops from one sub-band to another in a pseudo-random or deterministic manner. Frequency hopping can provide frequency diversity to combat deleterious path effects as well as randomization of interference from other cells/sectors.

Fig. 9 illustrates a frequency hopping scheme 900, which can be used for the forward and/or reverse links in an FH-OFDMA system. For the embodiment shown in FIG. 9, the subbands in a given (common or sector-specific) set of subbands are arranged into K subsets, and each subset contains P subbands, where K > 1 and P ≧ 1. The subbands in each subset may be contiguous subbands in the set (as shown in fig. 9) or non-contiguous subbands (e.g., distributed across the set).

Each traffic channel of a subband set is associated with a FH pattern that indicates a particular subset of P subbands to use in each "hop" period. The FH pattern may also be referred to as an FH sequence, a frequency hopping pattern, or some other terminology. The hop period is the amount of time spent on a given subset and lasts for Q OFDM symbol periods (or simply "symbol periods"), where Q > 1. The FH patterns for different traffic channels in a set of subbands are orthogonal to one another so that no two traffic channels use the same subband in any given hop period. This property avoids or minimizes intra-sector interference. The FH pattern for each traffic channel may pseudo-randomly select different subbands in different hop periods. Frequency diversity is achieved by selecting all or most of the subbands in the set for a certain number of hopping periods. To randomize inter-sector interference, the FH pattern for each sector-specific set may be pseudo-random with respect to the FH patterns for other sector-specific sets.

Fig. 10 shows a flow diagram of a process 1000 for transmitting data with intra-cell common reuse. First, channel conditions for terminals within a given sector x are determined (block 1012). As described below, the channel condition may be determined in various ways, and may indicate whether the terminal observes high interference from at least one other sector within the same cell. A terminal may be assigned subbands in either the common set or the sector-specific set for sector x based on at least the channel conditions for the terminal (block 1014). The common set and the sector-specific sets are non-overlapping. The sector-specific set includes subbands that may be allocated to terminals in sector x. The common set contains subbands that experience little, if any, interference from sector x and at least one other sector in the cell. Data for the terminal is processed and transmitted on the assigned subbands via the forward and/or reverse links (block 1016).

Each sector may assign subbands to its terminals in various manners. For example, multiple groups of terminals may be formed for each sector, with each subband set corresponding to a group of terminals, and terminals in each group may be assigned subbands in the associated set. Each terminal may be classified into one of the groups based on the channel conditions of the terminal, the number of subbands in each set, the number of terminals sharing subbands in each set, and so on. The terminals in each group may then be allocated subbands in the associated set based on quality of service (QoS), system load, fairness requirements, other information, and/or other considerations.

Fig. 11 shows a flow diagram of a process 1100 for allocating subbands to terminals. Process 1100 may be used for blocks 1012 and 1014 in fig. 10 and may be performed by each sector in each scheduling interval, which may be any time interval. First, the terminal obtains measurements for different sectors and/or obtains measurements for the terminal for different sectors (block 1112). Each sector may transmit a pilot on the forward link that terminals in the system may use for signal detection, timing and frequency synchronization, channel estimation, and so on. The pilot is typically composed of known modulation symbols that are processed and transmitted in a known manner. The terminal may also transmit pilot on the reverse link to facilitate reception of data by the sector. The measurements for the terminal may be based on the pilot sent by the sector on the forward link, the pilot sent by the terminal on the reverse link, and/or some other transmission.

In one embodiment, a terminal searches for pilots transmitted by sectors in the system and reports a number of the highest pilot measurements to the serving sector. In another embodiment, the terminal measures the observed interference for different subband sets, derives a Channel Quality Indication (CQI) for each subband set, and sends the CQI for the different subband sets to the serving sector. The CQI indicates the received signal quality achieved by the terminal for the subband set. The received signal quality may be quantified by a signal-to-interference-and-noise ratio (SINR), an energy-to-total-noise-ratio-per-chip (Ec/No), an energy-to-noise-per-chip (Ec/Nt), a carrier-to-interference ratio (C/I), or some other signal quality metric. The CQI can be measured and reported in a shorter time than the pilot measurements, which then allows for fast allocation of subbands and faster response to rapidly changing channel conditions. In another embodiment, the sector makes measurements for pilots transmitted by the terminal and reports the pilot measurements to the serving sector.

Intra-cell interference for the terminal is determined based on measurements obtained for the terminal (block 1114). For the forward link, intra-cell interference may be determined based on pilot measurements for all sectors in the same cell that are not designated to transmit to the terminal. For the reverse link, the intra-cell interference may be determined based on pilot measurements for terminals from all sectors in the same cell. The terminal may also measure intra-cell interference and report the measurement to the serving sector. Intra-cell interference may also be inferred based on a location estimate for the terminal. Thus, intra-cell interference may be determined in various ways and based on various measurements. In general, intra-cell interference may be determined based on forward link and/or reverse link measurements. The forward and reverse links are reciprocal (reciprocal) in the long term that can be assumed. In this case, a strong pilot measurement for a given sector by a terminal on the forward link may mean that the sector will be strong interference on the forward link and will also receive strong interference from the terminal on the reverse link. The same reasoning applies to reverse link pilot measurements.

The intra-cell interference for the terminal is compared to an interference threshold (block 1116). As determined in block 1120, if the intra-cell interference exceeds a threshold, the terminal is assigned a subband from the common set (block 1122). Otherwise, the terminal is assigned subbands from the sector-specific set for the serving sector (block 1124). The assigned subbands are then transmitted to the terminal (block 1126). Blocks 1112 and 1114 may correspond to block 1012 in fig. 10, and blocks 1116 through 1124 may correspond to block 1014.

In general, a terminal may be assigned subbands from a common set or a sector-specific set based on various factors such as intra-cell interference observed by the terminal, a handover request of the terminal, quality of service (QoS) requirements, a priority of the terminal, and so on. The decision to use a common set or a sector-specific set may be determined based on direct or indirect inputs from different sectors, e.g., measurements for/from different sectors.

Fig. 12 shows a flow diagram of a process 1200 for transmitting data on subbands assigned to a terminal. Process 1200 may be used for data transmission on the forward and/or reverse links. Traffic data for the terminal is processed (e.g., encoded and symbol mapped) to generate data symbols (block 1212). As used herein, a "data" symbol is a modulation symbol for traffic data, a "pilot" symbol is a modulation symbol for pilot, and a modulation symbol is a complex value of a point in a signal constellation of a modulation scheme. The data symbols are mapped to subbands assigned to the terminal (block 1214). The mapped data symbols and pilot symbols and/or signaling are further processed and transmitted (1) from the one or more sectors to the terminal on the forward link or (2) from the terminal to the one or more sectors on the reverse link (block 1216).

Fig. 13 shows a flow diagram of a process 1300 for receiving data on a subband assigned to a terminal. Process 1300 may be used for data reception on the forward and/or reverse links. (1) The terminal receives a data transmission for the terminal via the forward link or (2) the sector via the reverse link (block 1312). A determination is then made as to whether the terminal is assigned subbands in the common set or the sector-specific set (block 1314) and whether a softer handoff is performed for the terminal (block 1316). If the terminal is assigned subbands in the sector-specific set or if a softer handoff is not occurring, then the data transmission received from/by one sector (the serving sector) is processed to obtain soft decision symbols for the terminal (block 1322). Soft-decision symbols are multi-bit values obtained by the receiver for a single-bit (or "hard") value transmitted by the transmitter, with additional bits used to capture uncertainty in the single-bit value due to noise and other artifacts (artifacts). The soft-decision symbols for the terminal are then processed (e.g., detected and decoded) to obtain decoded data for the terminal (block 1324).

If the terminal is assigned subbands in the common set and if softer handoff is occurring, then data transmissions received from/by multiple sectors (the serving sector and at least one other sector) for the terminal are processed to obtain soft decision symbols for each sector (block 1332). For forward link transmission, the terminal may combine the soft-decision symbols obtained for multiple sectors to obtain combined soft-decision symbols with improved signal quality (block 1334). For reverse link transmission, the serving sector may receive soft decision symbols obtained by other sectors for the terminal and combine the soft decision symbols obtained by the different sectors to obtain combined soft decision symbols for the terminal (again, block 1334). In any case, the combined soft decision symbols for the terminal are decoded to obtain decoded data for the terminal (block 1336).

Fig. 14 shows a block diagram of an embodiment of base station 110x for sector x, base station 110y for sector y, wireless terminal 120, and cell entity 150. Base stations 110x and 110y and cell entity 150 are network entities of a cell.

At base station 110x, an encoder/modulator 1412x receives traffic data for the terminals served by base station 110x, processes (e.g., encodes, interleaves, and symbol maps) the traffic data for each terminal based on the coding and modulation schemes selected for that terminal, and generates data symbols for each terminal. Symbol-to-subband mapper 1414x maps the data symbols for each terminal to the subbands assigned to that terminal as indicated by a control signal from controller 1430 x. Mapper 1414x also provides pilot symbols on the subbands used for pilot transmission and provides zero signal values for each subband not used for transmission. For each OFDM symbol period, mapper 1414x provides N transmit symbols for a total of N subbands, where each transmit symbol may be a data symbol, a pilot symbol, or a zero signal value.

An OFDM modulator (Mod)1416x receives the N transmit symbols for each OFDM symbol period and generates corresponding OFDM symbols. Typically, OFDM modulator 1416x includes an Inverse Fast Fourier Transform (IFFT) unit and a cyclic prefix generator. For each OFDM symbol period, the IFFT unit transforms the N transmit symbols to the time domain with an N-point inverse FFT to obtain a "transformed" symbol that contains N time-domain chips. Each chip is a complex value to be transmitted in one chip period. A cyclic prefix generator then repeats a portion of each transformed symbol to form an OFDM symbol comprising N + C chips, where C is the number of chips being repeated. The repeated portion is commonly referred to as a cyclic prefix and is used to combat inter-symbol interference (ISI) caused by frequency selective fading. One OFDM symbol period corresponds to the duration of one OFDM symbol, which is N + C chip periods. OFDM modulator 1416x provides a stream of OFDM symbols. A transmitter unit (TMTR)1418x processes (e.g., converts to analog, filters, amplifies, and frequency upconverts) the OFDM symbol stream to generate a modulated signal, which is transmitted from an antenna 1420 x.

At terminal 120, the modulated signals transmitted by one or more base stations are received by an antenna 1452 and the received signal is provided to a receiver unit (RCVR)1454 and processed to generate samples. The set of samples for one OFDM symbol period represents one received OFDM symbol. An OFDM demodulator (Demod)1456 processes the samples and provides received symbols, which are noisy estimates of the transmitted symbols sent by the base station. Typically, the OFDM demodulator 1456 includes a cyclic prefix removal unit and an FFT unit. A cyclic prefix removal unit removes the cyclic prefix within each received OFDM symbol to obtain a received transformed symbol. An FFT unit transforms each received transformed symbol to the frequency domain with an N-point FFT to obtain N received symbols for a total of N subbands. A subband-to-symbol demapper 1458 obtains the N received symbols for each OFDM symbol period and provides the received symbols for the subbands assigned to terminal 120 as indicated by a control signal from controller 1470. Demodulator/decoder 1460 processes (e.g., detects, deinterleaves, and decodes) the received symbols for terminal 120 and provides decoded data for the terminal.

For reverse link transmission, at terminal 120, the traffic data is processed by an encoder/modulator 1462, mapped to subbands assigned to terminal 120 by a symbol-to-subband mapper 1464, further processed by an OFDM modulator 1466, conditioned by a transmitter unit 1468, and transmitted via an antenna 1452. At base station 110x, the modulated signals from terminal 120 and other terminals are received by antennas 1420x, conditioned by receiver units 1422x, and processed by OFDM demodulators 1424 x. Symbol-to-subband demapper 1426x obtains the N received symbols for each OFDM symbol period and provides the received symbols for each terminal from the subbands assigned to that terminal. Demodulator/decoder 1428x processes the received symbols for each terminal and provides decoded data for that terminal.

Base station 110y processes the data and transmits data on the forward link to the terminals in communication with base station 110y and also receives data on the reverse link from the terminals. The processing by base station 110y is similar to the processing by base station 110 x. For softer handoff users, the base stations of the same cell may exchange soft decision symbols, which are not shown in fig. 14.

In one embodiment of intra-cell common reuse, controller 1430 at each base station 110 identifies terminals desiring to transmit data on the forward and/or reverse links, ascertains the channel conditions for each terminal, and determines whether each terminal should be assigned subbands in the common set or in the sector-specific set. The channel conditions for each terminal can be ascertained and reported back to the base station based on reverse link measurements made by the base station 110 or forward link measurements made by the terminals. Sector scheduler 1434 at each base station then assigns subbands (or traffic channels) in the sector-specific set to the terminals and schedules the terminals for data transmission on the forward and/or reverse links. Each base station then provides each scheduled terminal with its assigned traffic channel, e.g., via over-the-air signaling. Cell scheduler 1434w within cell entity 150 allocates subbands (or traffic channels) in the common set for the cell to the terminals and schedules the terminals for data transmission. Cell scheduler 1434w may communicate with sector schedulers 1434x and 1434y to coordinate terminal scheduling within a cell. In another embodiment, a single scheduler schedules all terminals in a cell for data transmission on the forward and reverse links. The subbands may also be assigned in various other manners to the terminal for forward and/or reverse link transmission.

Controllers 1430x, 1430y, 1430w, and 1470 direct operation at base stations 110x and 110y, cell entity 150, and terminal 120, respectively. Memory units 1432x, 1432y, 1432w, and 1472 store program codes and data used by controllers 1430x, 1430y, 1430w, and 1470, respectively. Controllers 1430x and 1430y may also perform other processing for data transmission and reception, such as generating FH patterns for each terminal in communication with base stations 110x and 110y, respectively. The controller 1470 can generate an FH pattern for the terminal 120 based on the assigned traffic channel.

For clarity, intra-cell common reuse is described specifically as a system for cells with 3 sectors. In general, intra-cell common reuse may be used with any number of sectors. For a cell with R sectors (where R > 1), one common set may be formed for all sectors (for the first embodiment) or multiple common sets may be formed for different combinations of sectors (for the second and third embodiments). The sector-specific set for each cell may be formed based on a common set defined for that cell.

The above description of intra-cell common reuse is for a single cell. As described above, a system typically includes many cells. Intra-cell common reuse may be applied in various ways for cells in the system. To randomize inter-cell interference, the FH patterns for the sector-specific set in each cell may be pseudo-random with respect to the FH patterns for the sector-specific set in neighboring cells. The common set for different cells may be defined and operated on in various ways.

In one embodiment, the same common set is used for all cells in the system. The same FH pattern may be used for a common set in neighboring cells. This may simplify soft handover between cells. Alternatively, a common set may be defined for different neighboring cells in a common and pseudo-random FH pattern. The common FH pattern may be used to support soft handoffs between different cells. The pseudo-random FH pattern may randomize the interference observed by users in different cells assigned subbands in the common set. This embodiment simplifies the frequency planning for the system. In addition, sufficient interference averaging or diversity can be achieved if the common set is large enough that each user does not frequently collide with the same strong interference. In another embodiment, the common sets for neighboring cells are non-overlapping. For this embodiment, users assigned subbands in a common set in one cell observe random interference from users in neighboring cells. This embodiment may provide better interference diversity, especially for small common set sizes. In another embodiment, the common set for each cell is pseudo-random with respect to the common sets for neighboring cells. This embodiment may also provide good interference diversity. Each cell may communicate with neighboring cells to form a common set and a sector-specific set and/or exchange set information.

Intra-cell common reuse may also be described as being used for OFDMA systems. Intra-cell common reuse may also be used for Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Code Division Multiple Access (CDMA) systems, multi-carrier CDMA systems, and the like. TDMA systems use Time Division Multiplexing (TDM) and orthogonalize the transmission for different users by transmitting in different time intervals. FDMA systems use Frequency Division Multiplexing (FDM) and orthogonalize the transmission for different users by transmitting in different frequency channels or subbands. In general, the available system resources (e.g., subbands/channels, time slots, etc.) may be arranged into a common set and a sector-specific set. As described above, each sector may allocate system resources within a common set and a sector-specific set to users.

Intra-cell common reuse may also be used for global system for mobile communications (GSM) systems. The GSM system may operate in one or more frequency bands. Each frequency band covers a particular frequency range and is divided into a number of Radio Frequency (RF) channels of 200 kHz. Each RF channel is identified by a dedicated ARFCN (absolute radio frequency channel number). For example, the GSM 900 band covers ARFCNs 1 to 124, the GSM 1800 band covers ARFCNs 512 to 885, and the GSM 1900 band covers ARFCNs 512 to 810. Intra-cell common reuse may be used to improve efficiency and reduce intra-cell interference. The RF channels available to the GSM system may be arranged into a common set and a sector-specific set. Each GSM sector (commonly referred to as a "GSM cell") may then assign RF channels within its sector-specific set to strong and fair users, and RF channels within the common set to weak users. Intra-cell common reuse may allow a greater proportion of the available RF channels to be used by each GSM cell to achieve higher spectral efficiency.

The intra-cell common reuse techniques described herein may be implemented in various ways. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units used to support intra-cell common reuse at a base station may be implemented with one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. The processing unit for supporting intra-cell common reuse at the terminal may also be implemented with one or more ASICs, DSPs, etc.

For a software implementation, the intra-cell common reuse techniques may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a storage unit (e.g., the storage unit 1432x, 1432y, 1432w, or 1472 in fig. 14) and executed by a processor (e.g., the controller 1430x, 1430y, 1430w, or 1470). The memory unit may be implemented within the processor or external to the processor.

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 generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (44)

1. A method of allocating system resources in a wireless communication system, comprising:

determining a channel condition of a terminal; and

the terminal is assigned system resources in a first set or a common set based at least on channel conditions of the terminal, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals in a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector in the cell.

2. The method of claim 1, further comprising:

classifying the terminal into one of a plurality of groups based at least on channel conditions of the terminal, each group being associated with a different set of system resources, and wherein the terminal is allocated system resources based at least on the group into which the terminal is classified.

3. The method of claim 2, wherein the terminals are classified into one of the groups further based on an amount of system resources within the first and common sets, or a number of other terminals sharing the system resources within the first and common sets, or both.

4. The method of claim 1, wherein the terminal is allocated system resources further based on information for quality of service (QoS), system load, fairness requirements, or any combination thereof.

5. The method of claim 1, wherein the system resources are frequency subbands, and wherein the terminal is allocated at least one frequency subband in the first set or the common set.

6. The method of claim 1, wherein the system resources are time slots, and wherein the terminal is allocated at least one time slot of the first set or the common set.

7. The method of claim 1, wherein the system resources are Radio Frequency (RF) channels, and wherein the terminal is assigned at least one RF channel of the first set or the common set.

8. The method of claim 1, wherein the system resources in the common set are allocable to terminals in softer handoff and in communication with the first sector and the at least one other sector.

9. The method of claim 1, wherein the system resources in the common set are allocable to terminals located on a boundary between the first sector and the at least one other sector.

10. The method of claim 1, wherein the cell includes the first sector and second and third sectors, and wherein the common set includes system resources with little, if any, interference from the first, second, and third sectors within the cell.

11. The method of claim 1, wherein the cell includes the first sector and second and third sectors, and wherein the common set includes system resources with little, if any, interference from the first and second sectors within the cell.

12. The method of claim 11, wherein the system resources in the common set are included in a second set of system resources allocable to terminals in the third cell.

13. The method of claim 1, wherein the determining channel conditions for the terminal comprises

Obtaining a pilot frequency measurement result of the terminal; and

determining an amount of interference from the at least one other sector observed by the terminal based on the pilot measurements, and wherein the terminal is allocated system resources in the common set if the terminal observes high interference from the at least one other sector.

14. The method of claim 1, wherein the determining channel conditions for the terminal comprises

Received signal quality estimates for the first set and the common set are obtained, and wherein system resources in the first set or the common set are allocated to the terminal based on the received signal quality estimates.

15. The method of claim 1, wherein the wireless communication system utilizes Orthogonal Frequency Division Multiplexing (OFDM), and wherein the system resources within the first set and the common set are subbands obtained via OFDM.

16. The method of claim 1, wherein the wireless communication system is an Orthogonal Frequency Division Multiple Access (OFDMA) system that utilizes frequency hopping, wherein a first set of Frequency Hopping (FH) patterns is defined for the first set and a second set of Frequency Hopping (FH) patterns is defined for the common set, and wherein the terminal is assigned an FH pattern selected from the first or second set of FH patterns.

17. A method of allocating a sub-band in an Orthogonal Frequency Division Multiple Access (OFDMA) system using Frequency Hopping (FH), comprising:

determining a channel condition of a terminal; and

allocating a terminal a first set of FH patterns or a second set of FH patterns based at least on channel conditions for the terminal, the first set of FH patterns defined for a first set of subbands and the second set of FH patterns defined for a common set of subbands, the first and common sets being non-overlapping and including different subbands, the first set including subbands allocable to terminals in a first sector of a cell, and the common set including subbands with little, if any, interference from the first sector and at least one other sector in the cell.

18. The method of claim 17, further comprising:

classifying the terminal into one of a plurality of groups based at least on channel conditions of the terminal, a number of FH modes in the first and second groups of FH modes, a number of other terminals to be assigned FH modes in the first and second groups of FH modes, or any combination thereof, and wherein the terminal is assigned the FH mode based at least on the group into which the terminal is classified.

19. An apparatus in a wireless communication system, comprising:

a controller for determining a channel condition of a terminal; and

a scheduler to allocate system resources of a first set or a common set for the terminal based at least on channel conditions for the terminal, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals within a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector within the cell.

20. The apparatus of claim 19, wherein the cell comprises the first sector and second and third sectors, and wherein the common set comprises system resources with little, if any, interference from the first, second, and third sectors within the cell.

21. The apparatus of claim 19, wherein the cell comprises the first sector and second and third sectors, and wherein the common set comprises system resources with little, if any, interference from the first and second sectors within the cell.

22. An apparatus in a wireless communication system, comprising:

means for determining channel conditions for a terminal; and

means for allocating system resources of a first set or a common set for the terminal based at least on channel conditions for the terminal, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals within a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector within the cell.

23. The apparatus of claim 22, wherein the cell comprises the first sector and second and third sectors, and wherein the common set comprises system resources with little, if any, interference from the first, second, and third sectors within the cell.

24. The apparatus of claim 22, wherein the cell comprises the first sector and second and third sectors, and wherein the common set comprises system resources with little, if any, interference from the first and second sectors within the cell.

25. A method of allocating system resources in a wireless communication system, comprising:

forming at least one common set of system resources from all system resources available to a cell, each common set being defined for a different combination of at least two sectors within the cell and each common set including system resources with little, if any, interference from the at least two sectors; and

forming a sector-specific set of system resources for each sector within the cell, the sector-specific set for each sector including all but the system resources within each common set defined for the sector among all the system resources, and

wherein the terminal is assigned the sector-specific set of each sector and the system resources in the at least one common set based at least on channel conditions of the terminal in the cell.

26. The method of claim 25, wherein the wireless communication system utilizes Orthogonal Frequency Division Multiplexing (OFDM), and wherein the total system resources are a plurality of subbands obtained via OFDM.

27. The method of claim 26, wherein the cell includes first, second, and third sectors, and wherein each sector is associated with a first set of common subbands with little interference, if any, from the first, second, and third sectors.

28. The method of claim 27, wherein the first sector is further associated with second and third common sets, the second common set including subbands with little interference if there is little interference from the first and second sectors, and the third common set including subbands with little interference if there is little interference from the first and third sectors.

29. An apparatus in a wireless communication system, comprising:

means for forming at least one common set of system resources from all system resources available to a cell, each common set defined for a different combination of at least two sectors within the cell and each common set comprising system resources with little, if any, interference from the at least two sectors; and

means for forming a sector-specific set of system resources for each sector in the cell, the sector-specific set for each sector including all but the system resources in each common set defined for the sector in total system resources, and

wherein the terminal is assigned the sector-specific set of each sector and the system resources in the at least one common set based at least on channel conditions of the terminal in the cell.

30. A method of transmitting data in a wireless communication system, comprising:

obtaining an allocation of system resources for a terminal, the system resources allocated to the terminal being selected from a first set or a common set based at least on channel conditions for the terminal, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals within a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector within the cell; and

generating a control signal indicating the system resources allocated to the terminal.

31. The method of claim 30, further comprising:

processing the data of the terminal to obtain a data symbol; and

mapping the data symbols onto the system resources allocated to the terminal based on the control signal.

32. The method of claim 30, further comprising:

processing the received data transmission to obtain a received symbol; and

demapping symbols received from the system resources allocated to the terminal based on the control signal.

33. The method of claim 30, wherein the terminal is allocated system resources in the common set, and wherein data is transmitted to the terminal from at least two base stations for at least two sectors.

34. The method of claim 33, further comprising:

receiving data transmissions from the at least two base stations;

processing the data transmissions received from each base station to obtain soft-decision symbols for the base station;

combining the obtained soft decision symbols for the at least two base stations; and

decoding the combined soft decision symbols to obtain decoded data for the terminal.

35. The method of claim 30, wherein the terminal is allocated system resources in the common set, and wherein data is transmitted by the terminal to at least two base stations for at least two sectors.

36. The method of claim 35, further comprising:

receiving data transmissions from the terminal through the at least two base stations;

processing the received data transmission at each base station to obtain soft-decision symbols for the terminal;

combining, by the at least two base stations, the obtained soft decision symbols for the terminal; and

decoding the combined soft decision symbols to obtain decoded data for the terminal.

37. The method of claim 30, wherein the wireless communication system utilizes Orthogonal Frequency Division Multiplexing (OFDM), and wherein the system resources allocated to the terminal comprise at least one subband.

38. The method of claim 30, wherein the wireless communication system is an Orthogonal Frequency Division Multiple Access (OFDMA) system that utilizes Frequency Hopping (FH), and wherein the control signal indicates different subbands to use for data transmission in different time intervals.

39. An apparatus in a wireless communication system, comprising:

a controller configured to obtain system resource assignments for terminals and to generate control signals indicative of the system resources assigned to the terminals, the system resources assigned to the terminals being selected from a first set or a common set based at least on channel conditions of the terminals, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals within a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector within the cell.

40. The apparatus of claim 39, further comprising:

the data processor is used for processing the data of the terminal to obtain data symbols; and

a mapper for mapping the data symbols onto the system resources allocated to the terminal based on the control signal.

41. The apparatus of claim 39, further comprising:

a demodulator for processing a received data transmission to obtain received symbols; and

a demapper for demapping symbols received from the system resources allocated to the terminal based on the control signal.

42. An apparatus in a wireless communication system, comprising:

means for obtaining an allocation of system resources to a terminal, the system resources allocated to the terminal selected from a first set or a common set based at least on channel conditions for the terminal, the first set and the common set being non-overlapping and comprising different system resources, the first set comprising system resources allocable to terminals within a first sector of a cell, and the common set comprising system resources with little, if any, interference from the first sector and at least one other sector within the cell; and

means for generating a control signal indicating the system resources allocated to the terminal.

43. The apparatus of claim 42, further comprising:

means for processing data of the terminal to obtain data symbols; and

means for mapping the data symbols onto the system resources allocated to the terminal based on the control signal.

44. The apparatus of claim 42, further comprising:

means for processing a received data transmission to obtain received symbols; and

means for demapping symbols received from the system resources allocated to the terminal based on the control signal.