Attribution dynamique de ressources radio

TECHNICAL FIELD [0001] The present invention relates generally to the allocation of radio resources in mobile communication systems.

BACKGROUND ART [0002] The radio spectrum allocated to the mobile communication system must, in general, be reused in various geographical sub-areas, so-called cells, to provide both coverage and bandwidth. Depending on the choice of technology and factors such as the type of multiple access method used, the interference resistance of the mobile and base station receiver, the so-called re-use distance between different cells using the same part of the spectrum may, however, change. This change occurs not only between different types of systems, but also within the same system. The latter is caused, for example, by the topology of the service area.

[0003] In practice, a heterogeneous grid of regular hexagons is often used to model the cellular arrangement of a mobile communication system. Although they do not accurately describe the actual cells and their coverage area, the hexagons have proved useful for cell planning purposes because they are a convenient framework that can be used to define a wide range of mosaic cell reuse clusters to describe the distribution of available spectral / channel resources throughout the service area given system.

[0004] It is known that N-size mosaic clusters can be constructed if

N ^ e + ii + f, where i and j are non-negative integers, and i> j. The above relationship shows that the possible cluster sizes are N = 1, 3, 4, 7, 9, 12, ...

[0005] Of course, it is desirable to use a low reuse factor to optimize the spectral efficiency of a given system. However, regardless of the spread spectrum or spatial division multiplication methods used, it may not be possible to use a low reuse factor as the effect of co-channel interference from neighboring cells may become too strong. This means that the impact of co-channel interference can potentially eliminate the possibility of receivers demodulating various cells and extracting data intended for them that meets the quality expectations. To work around this problem and achieve control over the emission and impact of co-channel interference, many systems typically reuse factors greater than one in practice.

[0006] The use of a fixed rate of reuse greater than one automatically entails that only a certain portion of the available bandwidth is made available to any mobile station. This is obviously disadvantageous, both from the network's point of view and from the user's perspective for many reasons. In a small selection, the reasons are: l] The maximum peak capacity is reduced.

ί I As the transmission time increases, the degree of exposure to co-channel interference increases. Thus, the probability of base stations in nearby cells increases

- 2 simultaneously transmit packets to different users using the same channel resources.

[1 The base station's interference emission period for neighboring cells increases.

The availability of channel resources is reduced. When operating multiple mobile stations, the delay at the base station can become significant. This will be due to both the actual transmission time, but also the time required for retransmission.

Γ1 There is also a risk associated with reduced peak data transmission speed and channel availability that the user may feel the radio interface as slow to a greater extent.

[0007] One example of frequency planning is the one described in US Patent 6,498,934. Extended path loss estimators are used to allocate channels for different base stations. Path loss estimators are obtained by issuing commands attached to a mobile station system to measure the signals of some neighbor cells and block the power of mobile stations to enable synchronized measurements in neighboring base stations. The statistics of path loss estimators are calculated from the results of these measurements, which in turn are used to improve frequency planning.

[0008] Published US Patent Application 2003/0013451 A1 describes a method in which a re-use plan for cells of a communication system is dynamically redefined. Based on a number of factors, e.g. observed interference levels, load conditions, system requirements, etc., the reuse plan for sharing resources can be adapted to different cells. The publication also describes how to effectively allocate resources within an available resource set for each cell.

[0009] A problem with the customization of a reuse plan presented in US

2003/0013451 A1 is that the entire system must be involved in adaptation. The resources affected by the adaptation must be unused and the system data must be updated throughout the system before using the new reuse foam. This problem causes that the rules for applying adaptation, at least for adaptation to short-term changes in the communication system, are less favorable.

SUMMARY [0010] The basic problem with known resource allocation is that radio resources cannot be used effectively from the point of view of a real situation with interference affecting a mobile station at a specific location and at a specific time.

[0011] The main purpose of the present invention is therefore to develop devices and methods to improve the efficiency of radio resource utilization. Another additional purpose of the present invention is to allow allocation adjustments for very short periods.

[0012] The above objects are achieved by the methods and systems of the appended claims. Generally, radio resources are allocated for communication between the mobile and base station. The available radio resource set may include radio resources originally allocated to a neighbor cell if the mobile station has a temporarily low co-channel interference from such neighbor cells. The presence of co-channel interference is preferably inferred from the results of pilot signal quality measurements. The allocation may relate to communication to, and / or from, the base station. Measurement devices are placed in a mobile station, while devices for analysis, selection and actual allocation can be placed in different parts of the communication system - in a mobile station, in a base station or in a core network node, or as distributed means.

[0013] An advantage of the present invention is that it is possible to increase the use of radio resources in general. In addition, it is possible to efficiently support fluctuations in demand for resources on a short-term scale.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] The invention, together with its additional objectives and advantages, can be presented in the best manner understood in the following description with reference to the attached drawings, in which:

Fig. 1 is a simplified representation of a cellular communication system;

Fig. 2A illustrates the reuse of radio resources in a cellular communication system;

Fig, 2B is a graph illustrating the division of radio resource space into subsets;

Fig. 3 is a simplified representation of an embodiment of a cellular communication system operating in accordance with the present invention;

Fig. 4A is a block diagram of embodiments of a base station and a mobile station according to the present invention;

Fig. 4B is a block diagram of other embodiments of a base station and a mobile station according to the present invention;

Fig. 4C is a block diagram of a core network, base station and mobile station according to

0 of the present invention;

Fig. 4D is a block diagram of other embodiments of the core network, base station and mobile station according to the present invention;

Fig. 5 is an illustration attempting to visualize the separation of the conventional reuse concept as a result of applying the present invention; and

Fig. 6 is a flowchart of basic steps of an embodiment of the method of the present invention,

DETAILED DESCRIPTION [0015] The primary reason for considering re-use with a value above one is that it provides a means to control the co-channel interference (CCI - co30 channel interference). Since mobile stations on the periphery of the cells are the ones most exposed to CCI, the idea of ​​using a re-use coefficient greater than one guarantees, at least to some extent, throughput in all positions of all cells. This is obviously very desirable from a network point of view because it is possible to serve the most mobile stations. However, this approach is conservative. In some cell positions, for example, in an area close to the base station, but potentially also in other sub-areas, the interference situation may be such that most of the spectrum could be used without causing strong co-channel interference in other neighboring cells. This means that if there are only mobile stations in such areas, a smaller re-use rate could be used. This observation forms the basis of this

0 description of the use of the invention. The actual interference situation in the part of the cell in which the mobile station is located may allow for traffic using more part of the system bandwidth than was originally allocated in the originally used reuse scheme.

[0016] To illustrate this basic principle, the main mobile communication network is first described below. In Fig. 1, the mobile communication network 1 includes a core network 10. A core network

10 it is in turn connected to 12 external networks. A number of base stations 20: 1-20: 5 are connected to the core network 10. Each 20: 1-20: 5 base station is responsible for covering a specific geographical area, i.e. 30: 1-30: 5 cells. In the present specification, 30: 1-30: 5 cells are represented, for convenience of illustration, by hexagons. A mobile station located within a certain cell will typically be connected to a communication network via a radio link to a corresponding base station 20: 1-20: 5.

[0017] The mobile station being located in the outer part of the cell will be subjected to the influence of signals having relatively high powers also from neighboring cells. In order to prevent interference between different cells, in typical cases only part of the general radio resources are used in each cell. In a commonly used manner, available resources are divided into a number of groups, and each cell has the opportunity to use radio resources within one such group. This is the basic principle of resource reuse. One typical example is shown in Fig. 2A. There, the radio resources are divided into three parts, R1, R2, R3, and each cell can use one of these radio resource sets. In the example shown, the so-called reuse factor is 3. You can immediately

0 note that the same radio resources are not used in any of the neighboring cells, but are used in distant cells.

[0018] Fig. 2B shows the volume of radio resource space. In this representation, the radio resource space is enclosed between time, frequency and code. Depending on the radio methods actually used, the available resource space is divided into smaller volumes that are allocated for the uplink or downlink communication link between the base station and the mobile station. When a reuse plan is used, the total available radio resource space is divided into a number of partial volumes. In Fig. 2B, the total available radio resource space is divided into three parts, R1, R2, R3, which, for example, could be used as shown in Fig. 2A. The division in Fig. 2B is made in terms of frequency, i.e. the radio resources allocated to each cell are determined by a number of frequencies. However, the determination of partial resource spaces can be performed in other ways, in a time dimension, in a code dimension, or in any combination thereof. The resource space can also be extended to more dimensions, for example in the form of a spatial domain.

[0019] Fig. 3 shows an embodiment of a mobile communication system according to the present invention. A number of 20: 1-3 base stations, of which only three are designated, are assigned to the corresponding 30: 1-3 cells. The R4 radio resource set is mainly assigned to a 20: 1 base station, the R5 radio resource set is mainly assigned to a 20: 2 base station, and the R6 radio resource set is mainly assigned to a 20: 3 base station. Typically R4, R5 and R6

0 they remain only in mutual relations in the distance of the expected interference, i.e. they are non-shared resources if co-channel interference is likely to occur. However, radio resource collections located at greater mutual distances may contain common resources, i.e. these collections are typically non-exclusive when considered on a larger scale. Radio resource collections are typically allocated in accordance with a reuse plan, but may be managed differently.

[0020] Three 40: 1-3 mobile stations are shown as being in the coverage area of ​​5 cells 30: 1 and 30: 2. The 40: 1 mobile station is located near its own 20: 1 base station and communicates with the 20: 1 base station via radio resources 50. The 40: 2 mobile station is located inside the 30: 1 cell, but relatively close to the 30: 2 cell border and communicates with the base station

20: 1 via radio resources 51. The 40: 3 mobile station is located inside the 30: 2 cell, but relatively close to the 30: 3 cell and communicates with the 20: 2 base station via the 52: 2 radio resource.

[0021] A 40: 1 mobile station is typically affected by a plurality of radio signals 60 from different base stations in the communication system. The strongest signals are probably the radio signals from your own 20: 1 base station, but normally you can also detect signals from the closest other base stations. For a 40: 1 mobile station located close to its own 20: 1 base station, the signals from this own 20: 1 base station are probably much stronger than the second largest signals from the 20: 3 base station. However, for a 40: 2 mobile station, the signal strength from 20: 1 and 20: 2 base stations will probably not be very different. It is obvious to a skilled person that a 40: 2 mobile station is typically more exposed to co-channel interference than a 40: 1 mobile station. The assignment of radio resources is therefore typically in the worst case, for example a 40: 2 mobile station. However, in the case of

0 40: 1 mobile station, higher radio resource utilization could be beneficial.

[022] According to one embodiment of the present invention, the base station is also allowed to allocate radio resources that are not originally allocated to the base station for use in the entire cell. In some cases, that is to say, for some mobile stations located in certain places or having some interference situations, radio resources allocated to neighboring cells may also be used. In other words, with the variable allocation of resources according to the present invention, mobile stations may "borrow" spectrum from other cells in certain situations. The condition is that co-channel interference allows this. This remains valid in both uplink and downlink situations [0023] For the uplink, and with reference to Fig. 3, mobile stations typically have permission to use R4-R6 radio resources allocated to a certain cell. For example, 40: 1 and 40: 2 mobile stations can communicate with a 20: 1 base station using radio resources within R4, while a 40: 3 mobile station communicates with a 20: 2 base station using radio resources with R5.

[0024] However, a 40: 1 mobile station that is located close to the 20: 1 base station and far (in the radio sense) from, for example, a 20: 2 base station can also perform transmission using radio resources from R5. The reason is that the interference generated at the 20: 2 base station is very small due to the long distance and the fact that the 40: 2 mobile station probably transmits at low power The 40: 2 mobile station, on the other hand, cannot use radio resources from R5, because this can cause significant interference in the 20: 2 base station and spoil the possibility of implementation by

0 terminals in the appropriate cell 30: 2 transmission to the base station 20: 2.

[0025] For a downlink, the situation is similar. Dia to ensure good performance for a 40: 2 mobile station, downlink transmission from a 20: 1 base station to the mobile station

40: 2 is the only one using R4 resources. However, for a 40: 1 mobile station, the situation is slightly different because it is located far from base stations other than the 20: 1 base station. Thus, transmission to a 40: 1 mobile station from a 20: 1 base station can also be performed using resources from R5 and R6 (assuming that the 40: 1 mobile station reports a sufficiently low level of interference at frequencies other than inside R4).

[0026] To cause the base station to decide whether the use of a greater use of radio resources than originally allocated may be considered or not, when operating a particular mobile station, the base station should know the interference situation at the location of the mobile station when the packet is to be actually transmitted. In the general case, the mobile station measures the qualitative parameters of the signals transmitted from many base stations. Based on these qualitative parameters, an assessment is made by concluding which base stations among many base stations do not pose a risk of causing any significant co-channel interference. In other words, base stations are designated outside and inside, respectively, the range of distance or area of ​​inter-channel interference with respect to the first mobile station. Radio resources can then be designated that are used exclusively by non-interference base stations for eventual allocation of communications to and / or from the mobile station in question.

[0027] It is important to note here that the set of radio resources allowed or available to choose is specific for each mobile terminal and for each situation. Allocations of radio resources for general use by different base stations are not changed. Instead, the rules for allowing, in some interference situations, to use resources outside of the resources originally allocated to neighboring cells are changed. Thanks to this, there is no need for general adaptation of the entire distribution of resource space in the entire coverage area of ​​the communication system. The use or "borrowing" of the spectrum is done on a temporary basis in connection with a specific mobile station in a given situation. The adaptation time scale can be very fast and can even change between one series and the next. In addition, there is no need to send any notifications in the rest of the communication system.

[0028] In most communication systems, packaged data transmissions are pulsed in nature. This is potentially a problem because the mobile station may not be able to compile an accurate estimation of the interference situation based on the actual interference observed at a certain time point or period of data signals that is valid during the actual transmission of the base station. In a preferred embodiment of the present invention; typically in an Orthogonal Frequency Division Multiplexing (OFDM) based system, individual mobile stations measure observed pilot powers. Pilot tones, or more generally pilot signals, are transmitted on different subcarriers or groups of subcarriers from different cells with different reuse cluster identification numbers. The measured pilot strengths for the various reuse cluster groups are preferably reported before the packet to be transmitted from the base station to the mobile station. This means that the decision to allocate the spectrum is based on the received pilot power, not on real data traffic. This approach is beneficial because, unlike packet data traffic,

0 pilot information transmission from various cells is continuous over time.

[0029] If the power of pilot carriers transmitted in all cells defines these cells, i.e. no other carrier in a given cell is transmitted with greater power than pilot carriers, then the pilot power measurement report from the mobile station will provide the base station serving it with two important elements information. First, the worst case estimators of the interference levels that can be expected in adjacent radio resource spaces, i.e. all resources other than those originally allocated by the reuse scheme. It should be noted that the actual interference situation is probably better. In addition, it also provides a means for estimating the absolute path losses from the base station to the mobile station by comparing the reported received signal power in the allocated frequency band with known transmitted power. Since the transmission of pilots in all cells is continuous, the obtained interference estimators will be conservative. However, for the same reason that causes them to be conservative, they will also be quasi-stationary, making them valid during packet transmission if the request from the base station to make the measurement is close enough in real time to the transmission time.

[0030] Thus, for a given mobile station measurement report, the base station can, based on the estimated path loss and some predefined signal-to-interference ratio (SIR) calculate what transmit power is needed in each a subband for transferring data to a mobile station with a certain pre-defined quality of service. If these calculated power levels can be accepted, i.e. they are less than certain maximum values ​​finally determined by a certain network control algorithm or set at certain fixed levels proportional to the maximum allowable power in the initially allocated resources, then the base station can decide whether individual resources can be used or not for data transfer. Finally, depending on the packet size to be carried and the number of resources that can theoretically be allocated to a given mobile station, the base station can inform the mobile station using, for example, a logical control channel about which resources to include in the transmission of the next packet.

5 [0031] Interference estimators transmitted from mobile stations to the network can also be used to determine the radio resources allowed for a particular mobile station on the uplink. If the mobile station reports a low power level on downlink frequencies other than its own, such as in Fig. 3, 40: 1 mobile station reports a low level of interference in downlink resources belonging to R5, it is likely that the mobile station is close to its own base station, and the network may decide to allow mobile station to communicate on multiple resources on the link uplink, i.e. borrowing resources from neighboring cells. The mobile station could also autonomously decide on the bandwidth to be used in uplink transmission based on downlink measurements, although it is preferred to include the network in the decision-making process. Activity indicators transmitted from base stations to terminals could be used to decide on the temporary use of uplink radio resource. If all base stations in the vicinity report low traffic in their resources, then terminals in neighboring cells could borrow these resources for uplink transmission.

[0032] Although the present description generally includes the context of frequency reuse and OFDM systems, the use of the invention is not limited to this case. Others are possible

0 transmission techniques, for example CDMA, and reuse in dimensions other than frequency.

[0033] Fig. 4A illustrates an embodiment of a communication system according to the present invention having mobile station 40 and base station 20 cooperating in accordance with the principles of ~ 8 of the present invention. Base station 20 is additionally connected to the core network 10 and its nodes 70. Mobile station 40 receives a number of signals 60 from surrounding base stations. As mentioned above, the signals 60 are preferably pilot signals, but other signals, e.g., containing user data, may also be used. Mobile station 40 includes means 41 for measuring the signal quality parameter 54, 60. The basis of the quality parameter may be the signal strengths resulting in, for example, path loss parameter, channel gain parameter or various types of interference parameters. The measurement results are compiled and transmitted 53 to base station 20 in the measurement report.

[0034] The base station 20 receives a measurement report. The base station 20 in this embodiment includes an evaluation means 22 for evaluating quality parameters assigned to different base stations. More specifically, the evaluation means 22 determines which of the base stations is the one that presents problems of potential co-channel interference. In other words, it is determined whether the various base stations are, relative to mobile station 40, inside or outside the co-channel interference distance range. The range of co-channel interference distance is determined, for example, by the threshold C / L ratio. The base station 20 of the present embodiment further includes a dial means 23 for receiving a set of radio resources that the mobile station would be allowed to use. This permissible resource set obviously contains radio resources originally allocated to base station 20. In addition, if there are other radio resources that are originally allocated only to base stations outside the co-channel interference distance range, these radio resources are included in the resource set available for a particular mobile station 40. The risk of co-channel interference is low even if you use these resources not originally allocated to your own base station 20.

[0035] The base station 20 further includes an allocation means 24 which is responsible for the actual allocation of radio resources for communication between mobile station 40 and the base station

twenty. In this embodiment, radio resources selected from the available radio resource set are allocated for downlink communication 54. The allocation is carried out with the mobile station 40 given the appropriate quality of service in competition with other mobile stations attached to the same base station 40. Each of the attached mobile stations may then have its own available set of resources. When using shared resources that are not initially allocated to base station 20 to mobile stations having a favorable interference situation, resources originally allocated to base station 20 may be retained for any mobile stations more exposed to co-channel interference. In this way, a higher degree of utilization of the general radio resource can be achieved.

[0036] Fig. 4B illustrates another embodiment of a communication system according to the present invention. Similar parts as in Fig. 4A have the same reference numerals and are generally not further described. In the present embodiment, the mobile station 40 includes a measuring means 41. However, in this embodiment, mobile station 40 also includes an evaluation means 42, which in function is similar to the corresponding center station base in the previous embodiment. Base station 20 can supply mobile 40 station

0 information on relative emission powers between data signals and pilot signals. Such information can be provided not only for its own base station, but also for base stations that are presumably within the range of the audible (radio) distance. A message 55 is sent from the mobile station 40 to the base station 20, the message 55 now containing information about which neighboring base stations are received as interfering. This information is used in the middle of a dial 23 to receive an available set of radio resources for mobile station 40.

[0037] If the mobile station 40 is also provided with information about the original radio resource range, then also the functions of the dial means 23 may be performed instead at the mobile station, in which case the mobile station 40 may even suggest radio resources for use at the next communication.

[0038] Various functions of the method of the present invention may be performed in various parts of the communication system. This means that the device for implementing the procedure of the present invention is typically a diffuse agent. The base station signals must be measured at the mobile station. However, the remaining steps can be performed where it is more appropriate for each implementation.

[0039] Fig. 4C illustrates another embodiment of a communication system according to the present invention. In this embodiment, measurements are performed at mobile station 40, and the measurement report 53 is delivered to base station 20. However, in this embodiment, base station 20 forwards this information to node 70 in the core network 10. Node 70 then includes assessment means 72 and selection means 73, in analogy to previous embodiments. The available radio resource set is then transmitted back to base station 20 as the basis for

0 downlink traffic allocation.

[0040] Fig. 4D is, for the most part, identical to Fig. 4C, but the available radio resource set now includes resources for uplink communication 56. Mobile station 40 measures signals from neighboring base stations as before and sends a measurement report to base station 20, which forwards this information to node 70 in core network 10. The basic rule for allocating traffic to uplinks is that a mobile station that is not exposed to interference from other base stations is less likely to cause interference at the same base stations. Node 70 may, for example, perform actual C / l estimation and using C / 1 parameters exceeding a certain level as indicators of presumed co-channel interference. The node 70 may advantageously also use additional geographic information about the communication system to improve evaluation of the interference situation. Other complementary information may be indicators of activity from neighboring cells.

[0041] When the node 70 selects an available set of radio resources, it may also set the maximum emission power allowed to be used for each resource. Such power restrictions can be considered when allocating resources for uplink communications 56.

[0042] It is obvious to a person skilled in the art that the allocation of uplink resources can preferably be combined with the allocation of downlink resources.

[0043] In a conventional cellular communication system, the "reuse" principle is used frequently. Reuse is then defined on the basis of cells, i.e. each cell is allocated a certain proportion of radio resources. The present invention causes, however

0 disintegration of the conventional principle of reuse, since each of the individual mobile stations may have its own set of acceptable radio resources. Fig. 5 is an attempt to illustrate this state. This drawing figure shows a number of cells 30 in the form of hexagons. In part 31, external in the radio sense, of each cell 30, some of the radio resources may be used. Since the risk of interference from neighboring cells is high, a "reuse" factor greater than 1 is typically used. In part 33, internally in the radio sense, each cell 30 risk of interference is significantly lower, and in principle all radio resources can be used. This corresponds to a reuse factor of 1. In part 32, indirectly in the radio sense, of each cell 30, the risk of interference with some base stations is high, while it is still small with other base stations. This means that some additional resources are available compared to the outer part 31. In contrast, compared to the inner part 33, there is a limit on acceptable radio resources. It is obvious to the skilled person that the transition between these different stages is smooth, and that the position can vary from one cell to another or from one mobile station to another.

[0044] Fig. 6 is a flowchart for the basic steps of an embodiment of the method of the present invention. This embodiment essentially corresponds to the system shown in Fig. 4A. The procedure starts at step 200. At step 202, the mobile station measures the quality parameters of the signals from all base stations of the base stations in the range of audibility. At step 204, the measurement results are reported to the base station. At step 206, it is judged which base stations are inside and which are outside the mobile interference range of the mobile station. Based on the result of step 206, the available resource set is selected in step 208.

0 This selection includes resources originally allocated to its own base stations as well as resources allocated only to non-interfering base stations. At step 210, resources from the available resource set are allocated for communication between the mobile station and base stations. The data is then sent in step 212 using the allocated resources. The procedure ends in step 214. [0045] The embodiments described above are understood to be illustrative embodiments only

5 of the present invention. It is obvious to those skilled in the art that various modifications, combinations and changes of these embodiments can be made without departing from the scope of the present invention. In particular, if technically possible, partial solutions can be combined in other configurations. The scope of the present invention is, however, defined by the appended claims.