MXPA06004665A - Layered reuse for a wireless communication system - Google Patents

Abstract

To reduce inter-sector interference for"weak"users and combat a potentially large variation in interference levels observed by"strong"and weak users, system resources (e.g., frequency subbands) available for data transmission in a system are partitioned into multiple (e.g., three) disjoint sets. Each sector in the system is assigned one subband set. Neighboring sectors are assigned different subband sets such that the subband set assigned to each sector is orthogonal to the subband sets assigned to neighboring sectors. Each sector has an assigned subband set and an unassigned subband set, which contains all subbands not in the assigned set. Weak users in each sector (which are typically strong interferers to neighboring sectors) are allocated subbands in the assigned set. Strong users in each sector are allocated subbands in the unassigned set. The weak users in each sector are then orthogonal to strong interferers in neighboring sectors.

Description

STRATIFIED REUSE FOR A WIRELESS COMMUNICATION SYSTEM Field of the Invention The present invention relates generally to communication, and more specifically to data transmission in a wireless multiple access communication system.

BACKGROUND OF THE INVENTION A wireless multiple access system can concurrently support communication for multiple wireless terminals in the direct and inverse links. The forward link (or downlink) refers to the communication link from base stations to terminals, and the reverse link (or uplink) refers to the communication link from terminals to base stations. Multiple terminals can simultaneously transmit data in the reverse link and / or data received in the forward link. This can be achieved by multiplexing the data transmissions on each link to be orthogonal to each other. Depending on how multiplexing is performed, orthogonality can be achieved in time, frequency and / or code domain. The orthogonality ensures that the data transmission for each terminal does not interfere with the transmission of data for other terminals. A multiple access system typically has many cells, where the term "cell" can refer to a base station and / or its coverage area depending on the context in which the term is used. Data transmissions for terminals in the same cell can be sent using orthogonal multiplexing to avoid "intra-cellular" interference. However, data transmissions for terminals in different cells may not be orthogonalized, in which case, each terminal may observe "inter-cellular" interference from other cells. Inter-cellular interference can significantly degrade performance. for certain disadvantaged terminals that observe high levels of interference. To combat inter-cellular interference, a wireless system can employ a frequency reuse scheme, by means of which not all frequency bands available in the system are used in each cell. For example, a system can employ a reuse pattern of 7 cells and a reuse factor of K = 7. For this system, the W bandwidth of the entire system is divided into several equal frequency bands, and each cell in a Grouping of 7 cells is assigned to one of the seven frequency bands. Each cell uses only one frequency band, and each seventh cell reuses the same frequency band. With this frequency reuse scheme, the same frequency band is only reused in cells that are not adjacent to each other, and the inter-cellular interference observed in each cell is reduced in relation to the case in which all the cells use the same frequency. same frequency band. However, a reuse factor greater than one represents inefficient use of the system's available resources, since each cell is able to use only a fraction of the total system bandwidth. There is therefore a need in the art for techniques to reduce inter-cellular interference in a more efficient manner.

Summary of the Invention This document describes techniques to efficiently reduce inter-sector interference for "weak" users and to combat a potentially large variation in levels of interference observed by "strong" and weak users. A weak user has a relatively poor signal quality metric for his service base station, and a strong user has a relatively good signal quality metric for his service base station. The signal quality metric can be defined as described below. These techniques are called "stratified reuse" techniques and can efficiently use the available resources of the system (for example, the total system bandwidth). These techniques can be used by several communication systems and for both forward and reverse links. In one embodiment, system resources (eg, frequency sub-bands) available for the transmission of data in the system are divided into multiple (for example, three) disjoint or non-overlapping series.

For a system in which each cell is divided into multiple sectors (for example, three), a series of sub-bands is assigned to each sector. Nearby sectors are assigned different series of sub-bands, so that the sub-band series assigned to each sector is orthogonal to the sub-band series assigned to nearby sectors. Each sector can be associated with a series of assigned sub-band and a series of unassigned sub-band, which can include all the sub-band available in the system and not included in the assigned series. The size of all series of subbands can be equal, or approximately equal if the number of subbands is not a multiple of integer number of series of subbands. Alternatively, the size of the sub-band series can not be unequal and can be determined based on, for example, provisions of the sector, terrain, contents of the sector, and successively. Weak users in each sector (which are also typically interfering with nearby sectors) can be sub-bands distributed in the assigned series. Strong users in each sector (which are also typically non-strong interferers to nearby sectors), may be sub-bands distributed in the unassigned series. Because the series of subbands assigned to nearby sectors are orthogonal to each other, the weak users in each sector are orthogonal to strong interferers in nearby sectors. Stratified reuse techniques effectively distribute more interference to strong users and less interference to weak users. This then "balances" channel conditions for weak and strong users, improving performance for weak users, and provides other benefits. Various aspects and embodiments of the invention are described in further detail below.

BRIEF DESCRIPTION OF THE FIGURES The characteristics and nature of the present invention will become more apparent from the detailed description shown below, when taken in conjunction with the drawings in which similar reference characters are correspondingly identified through it and in where: Figure 1 shows a multiple access wireless communication system; Figures 2A and 2B show a sectorized cell and its model, respectively; Figure 3 shows a division of the total subbands N into three disunited series; Figure 4 shows an exemplary multi-cellular content with cells of 3 sectors; Figure 5 shows an interference distribution in a cluster of seven sectors; Figure 6 shows a process for distributing sub-bands to users based on a signal quality metric; Figure 7 shows an allocation of series of multiple subbands to each sector; Figure 8 shows an allocation of three series of subbands to each sector; Figure 9 shows a block diagram of a transmission entity; Figure 10 shows a block diagram of a receiving entity; and Figure 11 shows a block diagram of a frequency hopping generator.

Detailed Description of the Invention The word "exemplary" is used in this document to mean "that it serves as an example, case or illustration." Any modality or design described in this document as "exemplary", is not necessarily to be constructed as preferred or advaeous over other modalities or designs. Figure 1 shows a multiple access wireless communication system 100. The system 100 includes a number of base stations 110 that support communication for a number of wireless terminals 120. A base station is a fixed station used for communication with the terminals and it can also be referred to as an access point, a Node B, or some other terminology. The terminals 120 are typically dispersed throughout the system, and each terminal can be fixed or mobile. A terminal can also be referred to as a mobile station, a user equipment (UE), a wireless communication device, or some other terminology. Each terminal can communicate with one or possibly multiple base stations in the forward and reverse links at any given time. For a centralized architecture, a system controller 130 is coupled to the base stations, provides coordination and control for these base stations, and further controls the data course for the terminals served by these base stations. For a distributed architecture, the base stations can communicate with another as necessary, for example, to serve a terminal in communication with a base station, to coordinate the user of sub-bands, and so on. Each base station 110 provides communication coverage for a respective geographic area. To increase capacity, the coverage area of each base station can be divided into multiple sectors (for example three). Each sector is served by a base transceiver sub-system (BTS). For a sectorized cell, the base station for such a cell typically includes BTSs for all sectors of such a cell. For simplicity, in the following description, the term "base station" is used or generically for both a fixed station serving a cell and a fixed station serving a sector. A "serving" base station is one in which a terminal communicates. The terms "terminal" and "user" are also used interchangeably in this document.

The stratified reuse techniques described in this document can be used by several communication systems. For example, these techniques can be used by a Time Division Multiple Access (TDMA) system, a Frequency Division Multiple Access (FDMA) system, a Code Division Multiple Access (CDMA) system, a system CDMA multi carrier, a Multiple Access Orthogonal Frequency Division (OFDMA) system, and so on. A TDMA system that uses time division multiplexing (TDM) and transmissions for different users, is orthogonalized by transmitting in different time intervals. An FDMA system uses frequency division multiplexing (FDM), and transmissions for different users are orthogonalized by transmitting on different frequency channels or subbands. An OFDMA system uses orthogonal frequency division multiplexing (OFDM), which effectively divides the bandwidth of the total system into a number of orthogonal frequency sub-bands (N). These sub-bands also refer to tones, sub-carriers, silos, frequency channels and so on. Each subband is associated with a respective sub-carrier that can be modulated with data. An OFDMA system can use any combination of time, frequency and multipection by code division.

For clarity, stratified reuse techniques are described below by an OFDMA system. This OFDMA system, can be defined multiple orthogonal "traffic" channels, with it (1) each subband is used by only one traffic channel in any given time interval and (2) each traffic channel can be assigned , zero, one or multiple subbands in each time interval. A traffic channel can be seen as a convenient way to express a subband allocation for different time intervals. A different traffic channel can be assigned to each terminal. For each sector, multiple data transmissions can be sent simultaneously in these traffic channels without interfering with each other. The OFDMA system may or may not use frequency hopping (FH). With frequency hopping, a data transmission jumps from subband to subband in a pseudo-random manner, which can provide frequency diversity and other benefits. For an OFDMA frequency hopping system (FH-OFDMA), each traffic channel may be associated with a specific FH sequence indicating the particular subband (s) to use such traffic channels in each time interval (or jump period). The FH sequences for different traffic channels in each sector are orthogonal to each other, so that two traffic channels do not use the same subband at any given hop period. The FH sequences for each sector can also be pseudo-random with respect to the FH sequences for nearby sectors. These properties for the FH sequences minimize the intra-sector interference and randomize the inter-sector interference. In the OFDMA system, there may be a large variation in interference levels across the sub-bands, with interference entities depending on nearby sectors. For example, the terminal 120 g in Figure 1 is located at the coverage edge of its service base station 110c, while the terminal 120c is located closer to the base station 120c. Terminal 120g is also closer to its nearby base stations 110a and 110b than terminal 120h to its nearby base station 11Od. Consistently, for the same power transmitted by the sub-band to the terminals 120g and 120h, the terminal 120g of the "edge sector" causes more interference to its nearby base stations 110a and 110b in the reverse link, than the terminal " inside "120h to its nearby base station 120d. Terminals communicating with base stations 110a and 110b, they will observe high levels of inter-sector interference in the reverse link when their traffic channels "collide" with (or use the same sub-band as) the traffic channel for terminal 120g. The collision with strong interfering entities has a detrimental effect that is particularly significant for sector edge terminals. For example, terminal 120b is located at the coverage edge of its service base station 110a. The strong interference from the terminal 120g in combination with the weak received signal strength for the terminal 120b can significantly degrade the performance of the terminal 120b. The harmful effect of inter-sector interference can be mitigated by an extension with frequency of hybrid automatic retransmission (H-ARQ), which is a continuous transmission of additional redundancy information for each packet, until the packet is correctly decoded . However, there may still be considerable loss in both the capacity as system coverage due to a wide variation in channel conditions, for users in the system. Stratified reuse techniques can combat potentially large variations in inter-sector interference observed by strong users (interior) and weak users (edge sector). These techniques can be used for systems composed of non-sectorized cells as well as for systems composed of sectorized cells. For clarity, the stratified reuse is described below by an exemplary system composed of cells of sector 3 and series of subbands 3. Figure 2A shows a cell 210 with three sectors. The coverage area of each base station can be of any size or shape and is typically dependent on several factors, such as terrain, obstructions and so on. The coverage area of the base station can be divided into three sectors 212a, 212b and 212c, which are labeled as sectors 1, 2 and 3 respectively. Each sector can be defined by an antenna beam pattern (for example, 65 ° horizontal), and the three beam patterns for the three sectors can point to 120 ° each other. The size and shape of each sector is generally dependent on the antenna beam pattern for that sector. Cell sectors typically overlap at the edges, with the amount of overlap being determined by antenna beam patterns, terrain, obstructions and so on for these sectors. The edge of the sector / cell can be quite complex, and a cell / sector is not yet a continuous region. Figure 2B shows a simple model for a sectorized cell 210. Each of the three sectors in the cell 210 is modeled by an ideal hexagon approaching the sector boundary. The coverage area of each base station can be represented by a trefoil of three ideal hexagons centered on the base station. Figure 3 shows a division of the total subbands N in the system into three series of subband disunions. The three series are disunions or non-overlaps in which each of the sub-bands N belongs to only one series, if they are all. In general, each series can contain any number of subbands and any of the total subbands N. To achieve frequency diversity, each series may contain subbands taken through the total subbands N. bands in each series, can be evenly distributed across the total subbands N, so that consecutive subbands is the series, they are equally spaced apart (for example, by 3 subbands), as shown in FIG. 3. Alternatively, the subbands in each series may not be uniformly (eg, randomly) distributed across the total subbands N. This may be advantageous in that it can provide frequency diversity against channel fading . The subbands in each series can also be arranged in groups of a fixed size (for example, groups of 4 subbands), so that consecutive groups of subbands in the series are equally spaced apart (for example, 3 groups of sub-bands). The three subband series are labeled as Si, S2 and S3. For each cell of sector 3, the sub-band series S can be assigned to sector 1 of the cell, the sub-band series S2 can be assigned to sector 2 and the sub-band series S3 can be assigned to the sector 3. Each sector x (where x = 1, 2 or 3), can then be associated with two series of subbands, an S-series of assigned sub-band and a sub-band Sux series not assigned. Sux subband band unassigned may contain all subbands in the other two series not assigned to sector x. For example, sector 1 is associated with an assigned sub-band Sx series and a series Su? of unassigned subband that contain all the subbands in the series S2 and S3. Figure 4 shows an exemplary multi-cellular content 400 with each cell of 3 sectors being modeled by a trefoil of three hexagons. Sector 1 for all cells in the content is associated with an assigned sub-band Sx series and an unassigned sub-band Su_ series. Sector 2 for all cells is associated with an unassigned subband S2 series and an unassigned subband band Su2 containing all the subbands in the Si and S3 series. Sector 3 for all cells is associated with an unassigned subband band S3 and an unassigned subband band Su3, which contains all the subbands in the Si and S2 series. For the exemplary content shown in the figure 4, each sector is surrounded by sectors that are labeled differently from such sector. In this way, each sector 1 is surrounded by sectors 2 and 3, each sector 2 is surrounded by sectors 1 and 3, and each sector 3 is surrounded by sectors 1 and 2. The sub-band series not assigned for each sector is in this way, different from, and orthogonal to, the series of subbands assigned to nearby sectors. Each sector can use its assigned and unassigned subband bands in several ways. For example, each sector can distribute sub-bands in the assigned and unassigned series, to users in the sector based on channel conditions. Different users may have different channel conditions and may have different distribution and tolerance to inter-sector interference. The distribution of the sub-band can be done in such a way that good operation can be achieved for all users in the sector and taking into account the following observations. A key observation is that weak users typically cause more inter-sector interference. A weak user has a relatively poor signal quality metric for his service base station, due to various factors such as antenna beam pattern, path loss, shadowing and so on. The signal quality metric can be defined by a signal-to-noise ratio (SINR), a signal-to-noise ratio (SNR), a carrier-to-interference ratio (C / I), channel gain, received pilot power and / or some other quantity measured by the service base station, some other measurements, or any combination thereof. A weak user can, in general, be located anywhere within a sector, but it is typically located far away from their base service station. For simplicity, the following description assumes that the signal quality is dependent on the position in a sector, and a weak user is also called an edge sector user. Weak users usually require high transmission power in both the direct and inverse links, to achieve an objective level of performance or grade of service (GoS). In a well-designated system, users of the edge sector must have a relatively distant signal quality metric for at least one nearby base station, so that the transfer from a current base service station to the base station can be performed. close In the reverse link, for a given user u, users of the edge sector in the near sectors with relatively good signal quality metrics for the user's base service station u, are usually the dominant sources of interference to the user u. In the forward link, the amount of interference in each subband is proportional to the amount of transmit power used by the nearby base stations for such subband. If higher transmission powers are used in the direct link for users of the edge sector in nearby sectors, then the user u may observe higher levels of interference in subbands that collide with those used for users of the edge sector. Another key observation is that weak users are typically a bottleneck in a system that imposes a requirement or equity criterion. The equity requirement can dictate the programming of users for data transmission and the distribution of system resources to users in such a way that a minimum GoS is achieved for all users. Users of the edge sector have high trajectory losses resulting in low received signal power for both direct and inverse links. In addition, the level of interference observed in the direct link is also high, due to the distance closest to the interference base stations, and it can also be high in the reverse link due to users of the edge sector in nearby sectors. The combination of low signal strength received and high interference level, may require distribution of more system resources (for example, more sub-bands and / or extended transmission time), to border sector users to satisfy the equity requirement. The performance of the system can be improved by serving users of the edge sector more effectively. In a first stratified reuse scheme, to weak users (edge sector) in each sector, sub-bands are distributed in the assigned series and strong users (inside) are distributed sub-bands in the unassigned series. Weak users in each sector are typically strong interferers to nearby sectors and are also more vulnerable to high levels of interference from nearby sectors. Because the series of subbands assigned to nearby sectors are orthogonal to each other, the weak users in each sector are orthogonal to strong interferers in nearby sectors. Stratified reuse attempts to equalize channel conditions for weak and strong users, distributing more interference between strong users and less interference to weak users. By controlling the distribution of inter-sector interference in this way, performance is improved for weak users. Stratified reuse can facilitate the provision of remote services to users with different channel conditions. Figure 5 shows the distribution of users of edge sector in a grouping of seven sectors with the subband distribution described above. For simplicity of illustration, users of the sector of edge in each sector, are assumed to be located within a hexagonal ring that borders the limit of the hexagon for such sector. The hexagonal ring for sector 1 is shown with shading, the hexagonal ring for sector 2 is shown with diagonal lines, and the hexagonal ring for sector 3 is shown with crossed lines. For the content shown in Figure 5, sector 1 is surrounded by sectors 2 and 3 and not another sector 1. Consequently, users of the sector of edge in sector 1 are orthogonal to, and do not interfere with, users of the sector of edge in the six sectors 2 and 3 that surround this sector 1. With the distribution of the sub-band as described above and illustrated in Figure 5, weak users in each sector can observe no interference from strong interferers in nearby sectors . Consequently, weak users in each sector may be able to achieve a better signal quality metric. The variation in SINR for all users in the sector is reduced by improving the SINR of weak users (via less inter-sector interference), while possibly degrading the strong user SINR. Strong users can typically achieve good performance due to their better signal quality metrics. As a result, improved communication coverage, as well as the superior total system capacity, can be achieved for the system. Figure 6 shows a flow chart of a process 600 for distributing subbands to users in a sector based on channel conditions. The process 600 can be carried out and / or for each sector. Initially, the signal quality metric is determined for each user in the sector (block 612). This can be achieved by measuring the power received by a pilot transmitted by each user on the reverse link. Alternatively, each user can determine their signal quality metric, based on a pilot transmitted on the direct link by the sector and send the signal quality metric back to the sector. In any case, the sector obtains signal quality metrics for all users in the sector and classifies these users based on their signal quality metrics, for example, from the weakest user with the worst signal quality metric to the user stronger with the best signal quality metric (block 614). The sub-bands in the series assigned to the sector, they are then distributed to the users, for example, based on their classification, until all the subbands in the assigned series are distributed (block 616). For example, the weakest user can be distributed in sub-bands in the first assigned series, then the second weakest user can be distributed in sub-bands in the next assigned series, and so on. Once the assigned series is empty, the subbands in the unassigned series are then distributed to the remaining users, for example, based on their classification (block 618). The distribution of sub-bands can be done by a user at a time, until all the users have been distributed in sub-bands or all the sub-bands in both series have been distributed. The process then ends. The process 600 can be performed by each sector in each programming interval, which can be a predetermined time interval. Each sector can then send signaling (for example, to all users or only users distributed in different sub-bands), to indicate the sub-bands distributed in each user. Process 600 can also be performed (1) whenever there is a change in users in the sector (for example, if new users are added or a current user is deleted), (2) as long as the channel conditions for users change appreciably, or (3) at any time and / or due to any activation criteria. At any given time, all sub-bands may not be available for programming, for example, some sub-bands may already be in use for H-ARQ broadcasts. Figure 6 shows distribution of subbands based on the signal quality metrics for the users. In general, any factor and any number of factors can be considered for the distribution of the subband. Some factors that can be considered include the SINR achieved by the users, the proportions of data supported by the users, the size of the payload, the type of data to be sent, the amount of delay already experienced by users, the probability of unavailability, the maximum available transmission power, the type of data service to be offered and so on. These various factors can be given appropriate weights and used to give priority to users.

Users can then be distributed sub-bands based on their priority. The user with the highest priority can be distributed sub-bands in the first assigned series, then the user with the second highest priority and so on. With the classification based on priority, a given user can be distributed sub-bands in different series at different programming intervals if the relative priority of such a user changes. For clarity, much of the description in this document assumes the classification of users based only on channel conditions (eg, signal quality metrics). The distribution of the subband as described above also reduces the probability of observing interference for users in the edge sector in a partially loaded system. The load of each sector (denoted p) is the percentage of the total capacity to be used by that sector. If each assigned series contains one third of the total subbands N and if the users are distributed sub-bands in the first assigned series, then there is no inter-sector interference when the sector load is p < 1/3 and only the subbands in the assigned series are used by each sector. Without stratified reuse, each user may observe interference from a nearby sector one third of the time interval when the sector load is p = 1/3. If the sector load is 1/3 < > < !, then all the subbands in the assigned series are distributed, only a fraction of the subbands in the unassigned series are distributed, and only the subbands distributed in the unassigned series cause interference to users of the unassigned series. edge in the near sectors. Using the first assigned series, the load factor for the unassigned series (denoted as pu) is reduced and can be given as: pa =. { 3p -l) / 2. The lower pu results in reduced likelihood of observation of interference by border sector users in nearby sectors. For example, if the load for each sector is p ~ 2/3, then the load factor for the unassigned series will be pu = 1/2. In this case, strong users in each sector will be able to observe interference from a nearby sector 75% of the time, but weak users in each sector will be able to observe interference from a nearby sector only 50% of the time. Without stratified reuse, each user in each sector will be able to observe interference from users in a nearby sector 66.7% of the time. Reuse stratified in this way reduces the likelihood that weak users will see interference in a partially loaded system. Under certain operating conditions, a system can be limited by interference, which is a phenomenon by means of which the total capacity of the system can not be increased by adding more users or transmitting at a high power level. The partial load can be used to reduce the level of interference when the system is limited by interference. The partial load can be achieved, for example, by allowing each sector to use all the subbands in the assigned series, but only a fraction of the subbands in the unassigned series. The partial load may be performed selectively, for example, when the observed interference level exceeds a predetermined threshold. Stratified reuse techniques can conveniently support transfer, which refers to the transfer of a user from a current service base station to another base station that is thought to be better. The transfer can be done as necessary, to maintain good channel conditions for users at the edge of the coverage sector. Some conventional systems (eg, a TDMA system), support "hard" transfer whereby a user first interrupts the current service base station and then switches to a new base service station. The hard transfer allows the user to achieve switched cellular diversity against loss of trajectory and effect on the cost of a brief interruption in communication. A CDMA system supports "light" and "lighter" transfers, so that a user can simultaneously maintain communication with multiple cells (for light transfer) or multiple sectors (for lighter transfer). Light and lighter transfers can provide additional mitigation against rapid fading. Stratified reuse techniques can reduce interference for users in the edge sector, which are good candidates for transfer, and can also support hard, light, and lighter transfers. A user of edge sector u in sector x can be distributed sub-bands in the sector assigned to sector x. This user of edge sector u can also communicate with a nearby sector and via sub-bands in the series assigned for sector y. Since the series assigned for sectors x and y are disjoint, the user u can communicate simultaneously with both sectors x and y (and with minimal interference from strong interferers in both sectors), for light and lighter transfers. The user u can also perform hard transfer from sector x to sector y. Since the series of subbands assigned to sectors x and y are orthogonal to each other and are absent from strong interferers, the SINR received from the user u can not change completely abruptly, when transferred from sector x to sector y, which It can ensure a smooth transfer. Stratified reuse techniques can be used for both direct and inverse links. In the reverse link, each terminal can transmit a full power with respect to whether sub-bands have been distributed in the assigned or unassigned series in the terminal. With reference to Figure 1, the terminal of the edge sector 120g causes more interference to the base stations 110a and 110b. However, the inner terminals 120a, 120c, and 120e have better signal quality metrics for these base stations and are better able to withstand the high level of interference from the 120g terminal. In the direct link, each base station can transmit to total power for subbands in the assigned series and a reduced power for subbands in the unassigned series. For example, the base station 110c can transmit (1) to full power to the terminal of the edge sector 120g to improve the SINR received from this terminal and (2) to reduced power to inner terminals 120f and 120h to reduce the amount of interference inter-sector The terminals 120f and 120h may still be able to achieve high received SINR, even with the reduced transmission power, due to their better signal quality metrics for the base station 110c and the worst signal quality metrics for nearby base stations. The reduced transmission power for subbands in the unassigned series can be achieved by limiting the transmission power in these subbands to a predetermined power level and / or via a power control use. In general, the power control may or may not be used for the transmission of data in the direct and inverse links. The power control adjusts the transmission power for transmission data, such that the SINR received for transmission is maintained at a target SINR, which can, however, be adjusted to achieve a particular level of operation, for example , 1% packet error ratio (PER). The power control can be used to adjust the amount of transmitted power used for a given data rate, so that interference is minimized. For a system that uses power control for each user, the distribution of sub-bands in the series assigned to weak users and the sub-bands in the series not assigned to strong users, can automatically result in less transmission power to be used for strong users.

The power control can also be used for certain transmissions and omitted for other transmissions. For example, power control can be used in the direct link for subbands distributed in terminals in the unassigned series, to reduce the transmission power for these subbands. Power control can be omitted in cases where full transmission power can be more advantageous. For example, the total transmit power can be used for a variable rate transmission (e.g., an H-ARQ transmission), to achieve the highest possible ratio for a given channel condition. In the above description, each sector is associated with a series of assigned sub-band and a series of unassigned sub-band, where the series of sub-bands allocated for nearby sectors are orthogonal to each other. Additional improvement in interference control can be achieved by using more series of subbands for each sector. Figure 7 shows an exemplary allocation of multiple disunited sub-band series in each sector. In this example, to each sector x (where x = 1, 2 or 3), a series of sub-bands (labeled co or Sxa) used for the weakest users in the sector, a series of sub-bands is assigned (labeled as Sx_.) used for the following weakest users in the sector, two series of sub-bands (denoted as Sxc? and Sxc2), used for the strongest users in the sector, and two series of sub-bands ( labeled as Sxd? and Sxd2) used for the remaining users (or "media") in the sector. In general, each of the six series can contain any number of subbands and any of the total subbands N in the system. To minimize inter-sector interference for weak users, the sub-band series Sxa and Sx for nearby sectors must be orthogonal to each other. This can be achieved by simply dividing the assigned sub-band series Sx for each sector into two series. The two series of sub-bands Sxc? and Sxc2 for the strongest users in each sector x, must also be the same as the series of sub-bands Sya and Sza used for the weakest users in nearby sectors y and z, where x? Y ? z. The weakest users in each sector x, will then be able to observe interference from stronger users (which are also typically the weakest interferers) in nearby sectors y and x. The following weaker users in each sector x, may observe interference from the following weaker interferers (or average users), in nearby sectors y and z. Each sector can distribute sub-bands in six series to users in the sector, for example, similar to those described above in Figure 6. Each sector can classify its user based on its signal quality metrics and can then distribute sub-bands to its users in a time starting with the weakest user. The subbands in the Sxa series are distributed first until the series is exhausted, then the subbands in the Sxb series are distributed until the series is exhausted, then the subbands in the Sxd_ and Sxd2 series and finally the sub-bands in the Sxc series? and Sxc2. For clarity, the series of sub-bands Sxc? and Sxc2 for the strongest users are shown as two separate series, and the series of sub-bands Sxdl and Sxd2 for the average users are also shown as two separate series. To improve the frequency diversity, a single Sxc series can be formed with the subbands in the Sxc series? and Sxc2, and a single Sxd series can be formed with the subbands in the Sxd series? and Sxd2. A strong user can then be distributed sub-bands in the Sxd series, and an average user can be distributed sub-bands in the Sxc series. The use of multiple assigned sub-band series for each sector (for example, as shown in Figure 7), allows for better matching of weak users and strong interferers in different sectors, which can result in better equalization of channel conditions for strong and weak users. In general, any number of series of orthogonal sub-bands can be assigned to each sector. More series of sub-bands for finer categorization of users based on channel conditions and better user pairing with different channel conditions. The series of subbands can be defined in several ways. In one modality, the sub-band series are defined based on the global frequency planning for the system and remain static. The appropriate sub-band series are assigned to each sector and therefore, use these series of sub-bands as described above. This modality simplifies the implementation for stratified reuse, since each sector can act autonomously, and signaling is not required between nearby sectors. In a second modality, the series of sub-bands can be defined dynamically based on the sector's load and possibly other factors. For example, the sub-band series allocated for each sector may be dependent on the number of weak users in the sector, which may change over time. A designated sector or system entity (e.g., system controller 130) may receive the load information by various sectors, define the sub-band series and assign sub-band series to the sectors. This modality can allow better use of system resources based on the distribution of users. In yet another modality, the sectors can send inter-sector messages to negotiate series of sub-bands and assign the series of sub-bands to the sectors. In a second stratified reuse scheme, each sector is assigned multiple series (L) of sub-bands and distributes sub-bands in these series to users in the sector, based on the sector's load. The series of subbands L can be labeled Si up to S_ ,. The sector can distribute the sub-bands in the series Si first to users in the sector, then the sub-bands in the S2 series and so on, and then the sub-bands in the SL series. The different sub-band series can be associated with different levels of orthogonality. Figure 8 shows an allocation of series of subbands in each sector for the second stratified reuse scheme. In this example, to each sector x (where x = 1, 2 or 3), three series of subbands are assigned, which are labeled Sxaa, Sxbb and Sxcc. Each sector distributes sub-bands in the Sxaa series first, then sub-bands in the next Sxb series, and then sub-bands in the last Sxcc series. The sub-band series S_aa-S2aa and Saa for sectors 1, 2 and 3 are orthogonal to each other. The second stratified reuse scheme can improve the operation by a partially loaded system. For example, if the load of each sector p <; 1/3, then only the subbands in the Saa series are used by each sector, and the user does not observe any inter-sector interference. If the sector load is 1/3 < p < 2/3, then the series of Saa and Sbb subbands are used by each sector. The sub-band series Saa has a load factor of paa = 1, and the subband series Sbb has a load factor of A, b = (33-1). The sub-bands distributed among users in the series S? Aa in sector 1, observe (1) interference of distributed sub-bands of users in the series S3b_ in the near sector 3 for 100.pb percent of the time and (2) ) no user interference in the near sector 2 since the S2cc subband series is not used. If the load sector is 2/3 < p < 1, then all three series of subbands Saa, Sbb and Scc are used by each sector. The series of sub-band Saa has a load factor of paa = 1- the series of sub-band Sbb has a load factor of pob = 1, and the series of sub-band Scc has a load factor of pcc - . { 3p-2). The distributed series of users in the S? Aa series in sector 1 observe interference from (1) distributed user sub-bands in the S3bb series in the near sector 3 percent of time and (2) distributed sub-bands of users in the S2cc series in the near sector 2 percent. pcc percent of time. For the second stratified reuse scheme, users in each sector can also be classified, for example, based on their classification and the series in the predetermined order. For clarity, stratified reuse techniques have been specifically described by a system with cells in sector 3. In general, these techniques can be used by any reuse pattern. For a K-cell / K-cell reuse pattern, the available resources of the system can be divided into disunited series M, where M can or can not be equal to K. Each sector / cell, in the reuse pattern, can be distributed in one or more of the M sub-band series. Each sector / cell can then use the assigned series (s) and series (s) not assigned as described above. For clarity, stratified reuse techniques have been described for an OFDMA system. These techniques can also be used for systems using FDM, TDM, CDM, some other orthogonal multiplexing techniques, or a combination thereof. The resources of the system to be reused (for example, frequency of sub-bands / channels, time intervals and so on), are divided into disunited series, where each series contains a portion of the resources of the system. For example, the time interval available in the system can be divided into three series, each series contains different time intervals than those in the other two series. A series can be assigned to each sector, which can use the series assigned to weak users and the series not assigned to strong users. As another example, stratified reuse techniques can be used for a system such as Global System for Mobile Communications (GSM). A GSM system can operate in one or more frequency bands. Each frequency band covers a specific range of frequencies and is divided into a number of radio frequency channels of 200 kHz (RF). Each RF channel is identified by a specific ARFCN (absolute radio frequency channel number). For example, the frequency band GSM 900, covers ARFCN 1 to 124, the frequency band GSM 1800 covers ARFCN 512 to 885, and the frequency band GSM 1900 covers ARFCN 512 to 810. To each cell of GSM a series is assigned of RF channels and only transmits on the assigned RF channels. To reduce inter-cell interference, GSM cells located close to each other are conventionally assigned different series of RF channels, such that transmissions for nearby cells do not interfere with each other. GSM typically employs a reuse factor greater than one (for example, K = 7). Stratified reuse can be used to improve efficiency and reduce inter-sector interference for the GSM system. The RF channels available for the GSM system can be divided into K-series (for example, K = 7), and each GSM cell can be assigned to one of the K-series. Each GSM cell can then distribute RF channels in its assigned series. weak user in the cell and RF channels in the series not assigned to weak users. The RF channels can thus be distributed in a way to distribute interference to weak and strong users to obtain the benefits described above. Each GSM cell can be allowed to use all available RF channels, and a reusable factor of one can be achieved with stratified reuse. The processing for transmission and reception of data with stratified reuse is dependent on the design of the system. For clarity, exemplary transmit and receive entities in a frequency hopping OFDMA system for the first stratified reuse scheme using series of assigned and unassigned subbands is described below: Figure 9 shows a block diagram of a mode of a transmission entity HOx, which may be the portion transmitted from a base station or a terminal. Within the transmission entity lOOx, a coder / modulator 914 receives the traffic / packet data from a data source 912 for a given user u, processes (e.g., encodes, interleaves and modulates) the data based on a scheme of encoding and modulation selected by the user u, and providing data symbols, which are modulation symbols for data. Each modulation symbol is a complex value for a point in a signal constellation for the selected modulation scheme. A symbol mapping unit to subband 916 provides the data symbols for the user u in the appropriate subbands determined by an FH control, which is generated by an FH 940 generator based on the traffic channel assigned to the user u . The mapping unit 916 also provides pilot symbols or subbands used for pilot transmission and a signal value of zero for each subband not used for pilot or data transmission. For each OFDM symbol period, the mapping unit 916 provides transmitted symbols N for the total subbands N, where each transmitted symbol may be a data symbol, a pilot symbol, or a zero signal value. An OFDM modulator 920 receives the transmitted symbols N for each OFDM symbol period and generates a corresponding OFDM symbol. The OFDM modulator 920 typically includes a fast inverse Fourier transform unit (IFFT) and a cyclic prefix generator. For each OFDM symbol period, the IFFT unit transforms the transmitted symbols N to the domain in time using a point N inverse to FFT to obtain a "transformed" symbol containing time-domain N chips. Each chip is a complex value to be transmitted in a chip period. The cyclic prefix generator then repeats a portion of each transformed symbol to form an OFDM symbol containing N + C chips, where C is the number of chips that are repeated. The repeated portion is often called a cyclic prefix and is used to combat inter-symbol interference (ISI) caused by selective frequency fading. An OFDM symbol period corresponds to the duration of an OFDM symbol, which is time periods of the N + C chip. The OFDM modulator 920 provides a stream of OFDM symbols. A transmitter unit 922 (TMTR) processes (e.g., upconverts an analog conversion, filters, amplifiers and frequency), the OFDM symbol stream generates a modulated signal, which is transmitted from an antenna 924a. Controller 930 directs the operation to the IlOx transmission entity. The memory unit 932 provides storage for program and data codes used by the controller 930. Fig. 10 shows a block diagram of a modality of a receiving entity 12Ox, which may be the receiving portion of a base station or a terminal. One or more modulated signals transmitted by one or more transmitting entities are received by an antenna 1012, and the received signal is provided to and processed by a receiving unit (RCVR) 1014 to obtain samples. The series of samples for an OFDM symbol period represents a received OFDM symbol. An OFDM demodulator (Desmod) 1016 processes the samples and provides received symbols, which are noisy estimates of the transmitted symbols sent by transmission entities. The OFDM demodulator 1016 typically includes a cyclic prefix eliminator unit and an FFT unit. The cyclic prefix eliminator unit eliminates the cyclic prefix in each received OFDM symbol to obtain a received transformed symbol. The FFT unit transforms each received transformed symbol to the frequency domain with a FTT of point N to obtain received symbols N for the subbands N. A unit 1018 of submapping sub-band to symbol obtains the received symbols N for each period of symbol OFDM and provides received symbols for the subbands assigned to the user u. These subbands are determined by an FH control generated by a FH 1040 generator based on the traffic channel assigned to the user u. A demodulator / decoder 1020 processes (e.g., demodulates, deinterleaves and decodes) the symbols received by the user u and provides decoded data for a data store 1022 for storage. A controller 1030 directs the operation to the receiving entity 120x. A memory unit 1032 provides storage for program and data codes used by the controller 1030. For layered reuse, each sector (or a scheduler in the system) selects users for data transmission, determines the signal quality metric and / or gives priority to the selected users, classifies these users, and distributes the sub-bands or assigns traffic channels to the selected users. Each sector then provides each user with their assigned traffic channel, for example, via airborne signage. The transmit and receive entities for each user then perform the appropriate process to transmit and receive data in the sub-bands indicated by the assigned traffic channel. Figure 11 shows a block diagram of a mode of the FH generator 940 in the transmission entity 11Ox. The traffic channel assigned to user u is provided to a lookup table 1112a for the assigned series and a lookup table 1112b for an unassigned series. Each look-up table 1112 provides information indicating the sub-bands (s) used for data transmission in each time slot based on a sub-band mapping defined by its sub-band series. A selector 1114 receives the entries from the lookup tables 1112a and 1112b, selects the output of either the lookup table 1112a or 1112b based on a selected input per subband band, and provides the output selected as the FH control. The FH 940 generator can also be implemented with other designs, for example, with pseudo-random number (PN) instead of search tables. The FH generator 1040 at the receiving entity 120x can also be implemented in the same manner as the generator 940. The stratified reuse techniques described herein can be implemented by various means. For example, these techniques can be implemented in hardware, software or a combination of these. For a hardware implementation, the processing units are used to distribute subbands, process data for transmission or reception, and perform other functions related to stratified reuse, they can be implemented within one or more specific applications of integrated circuits (ASIC ), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), programmable field output (FPGA) arrays, processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described in this document, or a combination thereof. For software implementation, stratified reuse techniques can be implemented with modules (for example, procedures, functions, and so on), which perform the functions described in this document. The software codes can be stored in a memory unit (e.g., memory unit 932 in Figure 9 or memory unit 1032 in Figure 10), and executed by a processor (e.g., controller 930 in Figure 9). or 1030 in Figure 10). The memory unit can be implemented with the processor or external to the processor, in which case, it can be communicatively coupled to the processor via various means known in the art. The prior description of the described embodiments will be provided to enable any person skilled in the art to make or use the present invention. Various modifications to these modalities 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 scope and scope of the invention. In this way, the present invention is not proposed to be limited by the modalities shown in this document, but to be in accordance with the broader scope consistent with the principles and new features described in this document.

Claims (38)

NOVELTY OF THE INVENTION Having described this is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A method for distributing system resources in a communication system, characterized in that it comprises: classifying a plurality of terminals in communication with a current base station having at least one nearby base station; and distributing available system resources to the plurality of terminals based on the classification of the terminals, wherein the current base station is assigned to a series of system resources that are orthogonal to at least one series of system resources allocated by the system. minus one nearby base station, and wherein the available system resources include the series of system resources allocated to the current base station and additional system resources not in the series assigned to the current base station.

The method according to claim 1, characterized in that the plurality of terminals is classified based on the signal quality metric achieved by the terminals for the current base station.

The method according to claim 2, characterized in that the signal quality metrics are indicative of the received sound and interference to noise ratios (SINR) achieved by the terminals and the current base station.

The method according to claim 2, characterized in that the signal quality metrics are indicative of gain channels between the terminals and the current base station.

5. The method according to claim 1, characterized in that the plurality of terminals is classified based on priority determined by the terminals.

The method according to claim 1, characterized in that the current base station is assigned to a series of frequency sub-bands that is orthogonal to at least one series of frequency sub-bands assigned by at least one nearby base station , and wherein the available resources of the system comprise the series of frequency sub-bands assigned to the current base station and additional frequency sub-bands not in the series assigned to the current base station.

The method according to claim 6, characterized in that the series of frequency sub-bands assigned to the current base station include one third of all the frequency sub-bands available for data transmission in the system.

8. The method of compliance with the claim 6, characterized in that the series of frequency sub-bands assigned to the current base station is associated with a first transmitted power limit, and wherein the sub-bands of additional frequency not in the series assigned to the current base station are associated with a second limit of transmitted power that is lower than the first limit of transmitted power.

The method according to claim 6, characterized in that the plurality of terminals are distributed frequency sub-bands based on the classification, and wherein in the plurality of terminals the frequency sub-bands in the assigned series are first distributed. for the current base station and then the additional frequency sub-bands not in the series assigned to the current base station.

The method according to claim 6, characterized in that the plurality of terminals are classified based on metrics of signal quality achieved by the terminals for the current base station, and where the terminals with metrics of poor signal quality are distributed the frequency sub-bands in the series assigned to the current base station and terminals with better signal quality metrics, are distributed to the additional frequency sub-bands not in the series assigned to the current base station.

11. The method according to claim 1, characterized in that the system resources distributed to the plurality of terminals, they are used for data transmission in a reverse link.

The method according to claim 1, characted in that the system resources distributed to the plurality of terminals are used for data transmission in a direct link.

The method according to claim 1, characted in that the total transmission power can be used to send data transmission using the system resources in the series assigned to the current base station and the reduced transmission power can be used to Send data transmissions using additional system resources.

The method according to claim 1, characted in that the available resources of the system comprise a plurality of radio frequency (RF) channels, and wherein the current base station is assigned to a series of RF channels that are orthogonal in at least one series of RF channels allocated in at least one nearby base station.

The method according to claim 1, characted in that the available resources of the system comprise time intervals, and wherein the current base station is assigned time slot that is orthogonal to assigned time slots in at least one base station close

16. The method according to claim 1, characted in that the system uses orthogonal frequency division multiplexing (OFDM), and wherein the available resources of the system comprise a plurality of frequency sub-bands.

17. The method according to claim 16, characted in that the system is an orthogonal frequency division multiple access (OFDMA) system.

18. The method according to claim 17, characted in that the OFDMA system uses frequency hopping, and wherein each of the plurality of terminals is distributed to different subbands in different time intervals.

19. A method for distributing frequency subbands in a wireless communication system using orthogonal frequency division multiplexing (OFDM), characted in that it comprises: classifying a plurality of terminals in communication with a current base station based on quality metrics of signal achieved by the terminals for the current base station, where the current base station has at least one base station nearby; and distributing available frequency sub-bands to the plurality of terminals based on signal quality metrics, wherein the current base station is assigned to a series of frequency sub-bands that are orthogonal in at least one series of sub-bands assigned frequency in at least one nearby base station, wherein the available frequency sub-bands include the series of frequency sub-bands assigned to the current base station and at least one series of frequency sub-bands assigned in at least one a nearby base station, and where the terminals with poor signal quality metrics are distributed to the frequency sub-bands in the series assigned to the current base station, and terminals with better signal quality metrics are distributed to the sub-bands. -bands of frequency in at least one series assigned in at least one nearby base station.

20. An operable apparatus for distributing system resources in a communication system, characterized in that it comprises: an operating controller for classifying a plurality of terminals in communication with a current base station having at least one nearby base station, and distributing available resources of the system to the plurality of terminals based on classification of the terminals, wherein the current base station is assigned to a series of system resources that is orthogonal to at least a series of allocated system resources in at least one nearby base station, and wherein the available system resources include the series of system resources to the current base station and additional system resources not in the series assigned to the current base station; and a working memory unit to accumulate the series of system resources allocated to the current base station and additional system resources.

The apparatus according to claim 20, characterized in that the current base station is assigned to a series of frequency sub-bands that is orthogonal in at least one series of frequency sub-bands assigned in at least one nearby base station , and wherein the available resources of the system comprise the series of frequency sub-bands assigned to the current base station and additional frequency sub-bands not in the series assigned to the current base station.

22. The apparatus according to claim 21, characterized in that the plurality of terminals are classified based on the signal quality metric achieved by the terminals for the current base station, and where terminals with poor signal quality metrics are distributed. to the frequency sub-bands in the series assigned to the current base station and terminals with better signal quality metrics are distributed to the additional frequency sub-bands.

23. The apparatus according to claim 21, characterized in that the series of frequency sub-bands assigned to the current base station is associated with a first transmitted power limit, and wherein the additional frequency sub-bands are associated with a second transmitted power limit that is less than the first transmitted power limit.

24. An operable apparatus for distributing system resources in a communication system, characterized in that it comprises: means for classifying a plurality of terminals in communication with a current base station having at least one nearby base station; and means for distributing available system resources to the plurality of terminals based on terminal classification, wherein the current base station is assigned to a series of system resources that is orthogonal to at least a number of system resources assigned to the system. minus one nearby base station, and wherein the available resources of the system include the series of system resources allocated to the current base station and additional system resources not in the series assigned to the current base station.

25. The apparatus according to claim 24, characterized in that the current base station is assigned to a series of frequency sub-bands that is orthogonal in at least one series of frequency sub-bands assigned in at least one nearby base station, and wherein the available resources of the system comprise the series of frequency sub-bands assigned to the current base station and additional frequency sub-bands not in the series assigned to the current base station.

The apparatus according to claim 25, characterized in that the plurality of terminals is classified based on signal quality metrics achieved by the terminals for the current base station, and where terminals with poor signal quality metrics are distributed to the frequency sub-bands in the series assigned to the current base station and terminals with better signal quality metrics are distributed to the additional frequency sub-bands.

27. A method for processing data in a communication system, characterized in that it comprises: obtaining a distribution of system resources for a terminal, wherein the terminal and at least one other terminal in communication with a current base station are classified and distributed resources available system-based terminal classification, where the current base station is assigned to a series of system resources that is orthogonal in at least one series of system resources allocated in at least one base station near the current base station , and where the available resources of the system include the series of system resources assigned to the current base station and additional system resources not in the series assigned to the current base station; and generate an indicative control of the system resources distributed to the terminal.

28. The method according to claim 27, further comprising: receiving a transmission of data sent using the system resources distributed to the terminal; and process the transmission of data received in accordance with the control.

29. The method according to claim 27, characterized in that it further comprises: processing data for transmission in accordance with the control; and send a data transmission using the distributed system resources to the terminal.

30. The method according to claim 29, characterized in that the data transmission is sent to full transmission power if the terminal is distributing system resources in the series assigned to the current base station and sending at reduced transmission power if the terminal is distributing system resources not in the series assigned to the current base station.

The method according to claim 27, characterized in that the system uses orthogonal frequency division multiplexing (OFDM), and wherein the system resources comprise a plurality of frequency sub-bands.

32. The method according to claim 31, characterized in that the system uses frequency hopping, and wherein the control indicates different sub-bands used for data transmission at different time intervals.

33. An apparatus in a communication system, characterized in that it comprises: an operating controller for obtaining a distribution of system resources for a terminal, wherein in the terminal and at least one other terminal in communication with a current base station are classified and distribute available system resources based on classification of the terminals, where the current base station is assigned to a series of system resources that is orthogonal in at least one series of allocated system resources in at least one base station near the station current base, and where the system's available resources include the series of system resources assigned to the current base station and additional system resources not in the series assigned to the current base station; and an operating generator to generate an indicative control of the system resources distributed to the terminal.

34. The apparatus according to claim 33, further comprising: "a scrambler operative to receive a transmission of data sent using the distributed system resources to the terminal, and an operating unit process to process the transmission of received data. in accordance with the control

35. The apparatus according to claim 33, characterized in that it further comprises: an operational unit processing for processing data for transmission in accordance with the control, and a modulator operative for sending a data transmission using the system resources distributed to the terminal

36. An apparatus in a communication system, characterized in that it comprises: means for obtaining a distribution of system resources for a terminal, wherein the terminal and at least one other terminal in communication with the base station Current system resources are classified and distributed based on the n classification of the terminals, wherein in the current base station is assigned a series of system resources that is orthogonal in at least one series of system resources allocated in at least one base station near the current base station, and in where the available resources of the system include the series of system resources assigned to the current base station and additional system resources not in the series assigned to the current base station; and means for generating an indicative control of the system resources distributed to the terminal.

37. The apparatus according to claim 36, characterized in that it further comprises: means for receiving a transmission of data sent using the resources of the system distributed to the terminal; and means for processing the transmission of data received in accordance with the control.

38. The apparatus according to claim 36, characterized in that it further comprises: means for processing data for transmission in accordance with the control; and means for sending a data transmission using the system resources distributed to the terminal.