Service priorities in multi-cell network

The present invention relates to a radio resource manager and a radio resource management method.

In the future, it is proposed that wireless communication networks will consist of two or more wireless access technologies such as WCDMA (Wideband Code Time Division Multiplexing) and GSM / EDGE (Global System for Mobile Communications). By utilizing different wireless access technologies, the network as a whole can take advantage of the coverage and capacitance characteristics of each technology. The result is a more economical solution and the most appropriate wireless bearer for a variety of different services.

<p> In known radio access networks, the management of radio resources between systems is distributed. The radio network controllers of different systems manage the radio resources of each system independently. The efficiency of resource management functions is limited by the area under the control of the radio resource controller in each system.</p><p> The inventor has found that in order to utilize existing resources most efficiently, it is necessary to manage traffic within different systems. In a known configuration in which resources are controlled by the wireless network controller of each system, there is a particular problem with the execution of handover determination between systems. This is because the information that can be considered to perform the handover is limited to the resources under the control of each radio resource controller. Within a single system, the main limitation is the small amount of information that can be exchanged between different radio resource controllers. This makes it difficult to manage radio resources in the boundary area of the radio resource controller because the knowledge of the cells under the control of the adjacent radio resource controller is limited. In a multi-system environment, the information available from cells in another wireless access system is further limited and there is no standard way to check the state of cells in another system. In addition, if such an interface is standardized, for example, between two known radio resource controllers, a new radio access system that can be introduced later will be separate for all such radio resource controllers. Requires an interface.</p><p> As an additional problem, operating and maintaining a large number of systems individually is not cost effective, it reduces resource utilization and reduces network quality. Third-generation wireless communication networks can provide a wide variety of different services to end users. Continuous coverage or continuous coverage for all services anywhere in the cell due to the high signal-to-interference ratio required by high bitrate 3rd generation services, as opposed to existing 2nd generation networks. Quality of service (QoS) is not guaranteed. If the cell to which the call is assigned, handed over, etc. does not support the required quality of service, it means that the service cannot be supported or is not fully supported.</p>

<p> An object of the present invention is to address one or more of the problems described above. According to one feature of the invention, a method for use in a network covering an area, wherein the area comprises a plurality of areas, the user is designated as at least one of those areas, and A plurality of candidate areas that can be specified by a user are related, and the method receives information that identifies the plurality of candidate areas, and estimates a parameter that assumes that the user is designated as the candidate area for each candidate area. A method is provided in which the plurality of candidate areas are prioritized in consideration of the estimated values of the parameters.</p><p> According to yet another feature of the present invention, it is a radio resource manager for use in a network covering an area, the area comprising a plurality of areas, which the user designates as at least one of those areas. And a plurality of candidate areas that can be designated by the user are related, and the radio resource manager specifies a means for receiving information for identifying the plurality of candidate areas and the user designates the candidate area as the candidate area for each candidate area. A radio resource manager is provided that includes means for estimating parameters that are assumed to be, and means for prioritizing the plurality of candidate areas, taking into account the estimated values of the parameters.</p>

In order to better understand the present invention and how to implement it, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 shows a network of different wireless access technologies. Mobile station 2 or similar user equipment can use two or more wireless access technologies. It is clear that the mobile station is actually fixed and may be, for example, a PC, a personal digital assistant (PDA), or the like.

In the illustrated example, the wireless access technology is a macro, micro or pico system of 4, 6 or 8 respectively. These different systems have cells of different sizes, and macro cells are significantly larger than pico cells. Usually, the coverage area of one macrocell overlaps with many micro and / or picocells. Different wireless access technology systems can also be used within macro, micro and pico systems. In the illustrated example, different wireless access technologies include GSM / EDGE10, WCDMA12, WLAN14 (Wireless Local Area Network) or TDD16 (Time Division Duplex). Obviously, this is only an example, any system or wireless access technology can be omitted, and / or other suitable technology and the like can be used in embodiments of the present invention.

Mobile station 2 is configured to be able to communicate with these different systems. Common Radio Resource Management (CRRM) is provided to perform these tasks in order to obtain the best from different resources. This CRRM is formed by the server, but here, the entity that provides the CRRM function is referred to as CRRM. This will be explained with reference to FIG.

CRRM20 is formed by the server. The CRRM function is described in this embodiment as being formed by a single entity, but in another embodiment of the invention it is conceivable that many different entities provide this same function. These different entities may be part of different systems. The Iur interface is used with a distributed solution to exchange the required network element load information and / or other information. Load information can be exchanged between wireless network controllers via the Iur interface. This interface is defined between wireless network controllers. However, it will also be clear that the same or similar interfaces can be defined, for example, between a wireless network controller and a base station controller, and between a base station controller and a base station controller.

The CRRM20 is configured to be connected to each of the different systems, which in the embodiment shown in FIG. 2 are the WCDMA system 12, the GSM / EDGE system 10, the TDD system 16 and the IP RAN (Internet Protocol Radio Access Network). ) Equipped with system 22. The CRRM20 also receives and sends information from the operation and maintenance entity 24 to the entire network.

The interface between the CRRM20 and the different systems 10, 12, 16 and 22 is preferably formed by the elements that handle radio resource management in these systems. These elements are the radio network controller (RNC) of the WCDMA network, the base station controller (BSC) of the GSM / EDGE network, and the cell resource server (CRS) of the IP RAN network or some other radio resource controller. These elements are only given as an example of a controller, and the term wireless resource controller is intended to include all of these elements herein.

CRRM20 is a policy manager that controls access to wireless resources. As described in detail below, one of its tasks is to prioritize candidate target cells in handover and call configuration. The main effects of CRRM20 are as follows. -Share the load and use resources efficiently. -Disperses interference and gives high spectral efficiency. -Improved quality of service (QoS) management. Optimal end-user performance can be obtained by seamlessly integrating wireless technologies based on QoS management.

The characteristics of different wireless access systems are generally quite different, so signaling to take charge of common wireless resource management functions to avoid defining new interfaces when new wireless access systems should be used by the network. , Handover algorithms, harmonized load indicators, and other common languages are preferably defined between different systems and entities. A cell prioritization algorithm that can be used in CRRM to select or specify the optimal target cell for connection in call configuration, idle mode, handover / cell reselection, etc. will be described below.

In a mobile environment, handover / cell reselection occurs when the mobile station holding the connection leaves one coverage area or the network moves the mobile station to another cell for some other reason. You will need it. In the presence of two or more wireless access technologies and / or two or more services with different QoS requests, the handover / cell reselection decision (whether the connection must be handed over and to which cell it should be handed over) Judgment) is not as simple as in a known mobile environment where there is only one wireless access system and traffic is mostly a speech service. Similar problems arise in call configuration when a call cams into a connected cell in idle mode.

In the latter case, call configuration candidates are sent to CRRM20, which selects the best cell for the connection. Instead of using the commanded retry only when the cell is completely congested, the load threshold can be used to trigger the commanded retry. If the system knows a reliable idle mode movement measurement from an available cell before the signaling channel is assigned in the call configuration, the call can be directed to the optimal cell from the beginning.

Target cell selection in the CRRM20 is based on a prioritization algorithm that orders the cells contained in the candidate target cell list sent to the CRRM20 by each radio resource controller in a different radio access system. The candidate target cell list is then reconstructed based on the suitability grade of each cell to hold for the connection. Additional information can also be considered, such as whether the handover / cell reselection means a change in wireless access technology, a change in position, or a change in the routing area. The reordered candidate cell list is sent back to the radio resource controller, which directs the actual handover / cell reselection process.

The method according to the invention always connects the mobile station to the most suitable cell by integrating different wireless access systems so that the QoS requirements of the user connection are satisfied and the network performance is optimized with respect to spectral efficiency and trunk efficiency. can do. In fact, this can 1) accept a large number of users (and / or achieve high bitrates) while maintaining the quality of the connection; 2) minimize the number of unsatisfied users. Can; 3) make the handover / cell reselection procedure more reliable while minimizing unnecessary handover / cell reselection, and 4) use hardware resources in different wireless access systems. Can be optimized.

The process executed by CRRM20 as the handover judgment function is schematically shown in FIG. The different inputs to CRRM used by the CRRM algorithm are described in detail below. CRRM receives information about the status of cell resource 30 periodically or at the time of demand. This information includes, for example: 1. The current traffic load of the cell. This information can be used to check if new connections are expected to introduce a high load on the target cell. This load information can be divided as follows.

--Real-time (RT) load. This RT load can be easily measured as follows. --Percentage of hardware (HW) usage (eg, taking into account basic bandwidth capacity, transmission capacity, digital signal processor (DSP) capacity, spread code limits in WCDMA, etc.) --In WCDMA, this is the relationship between the transmit / receive (Tx / Rx) power used by the RT user and measured by the system and the target Tx / Rx power. One or the other, or both of the upling (Rx) and downlink (Tx) ratios can be transmitted.

--Non-real-time (NRT) load. This NRT load can be measured by measuring the average delay of the NRT user. The average delay is preferably sent separately for each format of the NRT traffic QoS class / priority combination. This means that the next average delay must be reported. --Average latency experienced by interactive traffic class packets with priority 1 to handle traffic. --Average latency experienced by interactive traffic class packets with priority 2 to handle traffic. --Average latency experienced by interactive traffic class packets with priority 3 to handle traffic. --Average latency experienced by background traffic class packets.

The reporting of these values is the relationship between the average delay and the retransmission time of higher layer (logical link control) frames. Other options for reporting delays are: --Average delay value (over different priority classes) --Weighted average delay. However, the weights are related to the scheduling priority of each priority class.

2. Full load. The relationship between the total Tx / Rx power measured by the system and the target Tx / Rx power in the cell's total HW utilization, or in WCDMA. Information about the upling (Rx) and / or downlink (Tx) can be sent to the CRRM.

3. Cell interference condition. The cell interference statistics can be used to select the most appropriate cell for interference. For real-time data services with guaranteed throughput, this interference measurement can be used to estimate how many resources the new service is trying to occupy in the target cell. Thus, in the case of a real-time user, CRRM can approximate the new real-time and total load of each candidate cell based on the load and interference information described above when prioritizing different cells.

Cell interference states can be transmitted with respect to: --95% Outage Carrier to Interference Ratio (C / I). This means that 95% of users in a cell will experience C / I greater than this value. Of course, other outage values and statistical scales can also be used. Alternatively, the interference measurement may be, for example, a bit error rate (BER) or bit error probability (BEP) outage (or other statistical measure). -Also, the interference value can be mapped to the throughput value in the radio resource controller, which can then be used to estimate the new real-time and full load of the candidate cell.

Another option for estimating the interference experienced by the user in different candidate cells is per connection associated with each candidate cell when an event such as an ordered retry (DR), handover, cell reselection, etc. is triggered. Is to send an interference estimate of. DR means a facility in a cellular radio system that allows mobile subscribers to make a second attempt and gain access if the first attempt fails due to congestion. Methods for estimating interference or potential throughput are described in detail below.

The CRRM20 can also receive information 32 about the state of other radio access network (RAN) elements, such as information related to gateway load, periodically or at demand. To map the percentage cell load value to the number of available / reserved time slots or a particular transmit power, CRRM knows the configuration information for different cells and / or the configuration information for different RAN elements. is required. This configuration information preferably includes the capacity of the cell. For example, this includes information on whether a particular cell supports GSM's GPRS (General Packet Radio Service) and / or EDGE (8-PSK modulation). This information can be received, for example, from network operation and maintenance entities.

Apart from the configuration information, parameters such as power budget handover margin between different cells (GSM specific) for circuit switching (CS) and packet switching (PS) (or RT and NRT) connections must be known by CRRM20. It doesn't become. Handover margins are related to power budgets and are used to avoid ping-pong effects between adjacent areas.

Other information that CRRM20 can use when prioritizing candidate cells includes: Received signal strength or link quality information from serving cells and commanded retry, direct access, handover or call reselection candidates prior to such an event (eg, RxLev (received signal level) in GSM, received signal code power in WCDMA. (RSCP) or Energy to Interference Ratio per Chip (Ec / I)). This is an important (but not essential for all embodiments of the invention) input when selecting the optimal cell. This is because it defines whether the mobile station is within the coverage area of a particular cell candidate. Connection quality of service (QoS) requirements. QoS requirements, such as guaranteed throughput requirements, must be taken into account when choosing the best cell. Throughput can be measured as the number of bits (or data bits) transferred in one direction across a partition per unit time (eg, bps). The format of the traffic class associated with the connection must be considered in relation to the QoS request. There are many packet data protocol (PDP) contexts associated with a connection. In such cases, the target cell prioritization preferably considers all relevant contexts.

In embodiments of the invention, parameters related to cell capacity, number of transceiver TRXs, target transmit to receive TX / RX power ratio, EDGE / GPRS capabilities, adjacent cell list, or initial handover HO threshold / margin, etc. are used. can do. The CRRM20 also receives information defining a candidate cell list, mobile station information, and connection information 34. As detailed below, CRRM uses the information it receives to give candidate cells a revised list of candidate target cells with weights or priority ratings.

The method according to the present invention will be described below with reference to FIG. 4, which shows the handover process. When the CRRM20 receives the candidate target cell list, it gives a priority value or weight to each cell included in the list. To calculate this priority value, the CRRM20 uses an algorithm, fuzzy logic, neural network or other procedure consisting of a linear or non-linear combination of its inputs. An example of a prioritization algorithm is shown in Figure 5. The priority Wn specified for each cell that is the target cell of the handover is obtained as a function of a large number of inputs as described above. Wn = f (Cell_Resources_Status, Other_RAN_Elements_Status, QoS_Requirements, MS_Measurements, MS_Classmark, O &amp; M_Settings, Operator_Preferences)

In the prioritization of candidate cells, the cells currently in service are also included in the candidate list. In this way, the CRRM20 can also prevent the commanded retries, handovers, cell reselections, etc. required by the radio resource controller when they are unnecessary or non-optimal. The next step is performed. It is clear that the CRRM will receive the information described above while this method is being performed. In step 1, a handoff trigger is detected. This may be any of the traditional triggers in known communication systems. In step 2, the candidate target cell list is sent to CRRM. This list is compiled with information received from different wireless access systems 10, 12 and 22. Only one radio resource controller reports the candidate list. The candidate cell list is based on the measurement report measured by the mobile station MS. The adjacent cell list in each radio resource controller also includes cells from other systems. Otherwise, they cannot be measured by the user connected to the cell belonging to a given radio resource controller.

In step 3, CRRM20 orders the list of candidate target cells, i.e., in order of priority. This is done using the algorithm described with reference to FIG. In step 4, the CRRM20 sends an ordered list of target cells to the radio resource controller of the system that has the cells currently associated with the mobile station. The radio resource controller then commands the handover operation based on the candidate cell list. In particular, the radio resource controller selects the cell with the highest priority. If that cell is unavailable for some reason, the cell with the next highest priority is selected, and so on.

In step 5, the mobile station receives a handover command from the wireless network controller, and in step 6, the connection is handed over to a new cell. The new cell may be in a different wireless access system or in the same system. The old connection will be broken. FIG. 5 showing a prioritization algorithm will be described. In the illustrated embodiment, the algorithm is shown as having N parts 50, where N is the number of cells in the candidate cell list. Each part 50 receives the following information related to the candidate cell it handles: That is, the cell state, the mobile station measurements from cell N52, the state 54 of other RAN elements (as described below), and the resource state of cell N56. The purpose of the prioritization algorithm is to give a priority WN to a cell. Mobile station measurements and recognition of candidate cells are given by candidate cell list 60. In addition, the radio resource controller provides each part of the algorithm via input 58 with mobile station class marks and radio access bearer parameters such as service quality requirements and / or the like.

Each part 50 of the algorithm also receives an operator preference 62 and also receives parameters of the algorithm and information related to the network configuration from the network operation and maintenance part 64. Based on the information received, each algorithm part calculates a priority or weight for each candidate cell. That information from algorithm part 50 is compiled into Listing 66, which is sent to the radio resource controller. It will be clear that the algorithm part can use the received information to execute the appropriate algorithm. Those skilled in the art could come up with such an algorithm.

As used herein, it will be apparent that the term wireless resource controller includes any entity within an access system that provides control within that wireless access system. For example, this is a base station controller (BSC) for GSM / EDGE systems, a wireless network controller (RNC) for CDMA systems, a cell resource server (CRS) for IP RAN systems, and so on. Emergency handovers, such as rapid field drop handovers, can be performed without consulting CRRM20 so as not to delay the procedure.

As mentioned above, the methods of the invention can be carried out intensively or decentrally. In a decentralized solution, each radio resource controller is responsible for performing cell prioritization for events triggered in the cell controlled by that particular radio resource controller. A decentralized solution requires exchanging network element state information from each radio resource controller to all adjacent radio resource controllers. In a centralized CRRM solution, this signaling only needs to be sent from each radio resource controller to its corresponding CRRM.

In the presence of a large number of CRRMs, signaling between CRRMs can be performed as in the case of distributed CRRM functions. FIG. 6 shows a network with two CRRM20s, each controlling a large number of cells or areas 68. The CRRM20 is configured to receive information from those cells or areas. A cell or area is associated with only one CRRM. CRRM20s are connected together to receive information about boundary cells or areas.

The centralized CRRM can also handle large areas, so the radio resource controller sends load information and / or other information from a particular "area" to the centralized CRRM rather than the cell. The CRRM then selects only the best "area", and the radio resource controller can select the best cell / resource within this area. Figure 7 shows another form in which the radio resource controller located in the boundary area 68 of the CRRM sends cell state information to a large number of CRRM20s. Therefore, a border cell or area can be reported to more than one CRRM and to all CRRMs that control adjacent areas or cells. A CRRM-to-CRRM interface is not required.

A preferred embodiment of the present invention combines the configurations of FIGS. 6 and 7 to allow cells or areas to report to two or more CRRMs and allow the CRRMs to communicate with each other. This has the effect that one or the other of any form can be used. This depends on the size of the CRRM, the available transport capacity, the base station capacity, and so on. It is clear that different systems may cover adjacent or at least partially overlapping areas. Therefore, the term "boundary cell" should be construed to include adjacent or superposed cells in the network or cells of different systems.

The CRRM20 is configured to be able to direct incoming calls to the most relevant candidate cells based on its QoS request (eg, wireless access bearer RAB parameters). In addition, the ability of candidate cells to support the requested QoS in the case of handover or network controlled cell reselection must be known. Among other parameters (eg traffic load, Rx level, operator priority), it is preferable to estimate the throughput for each cell, otherwise QoS (required) before selecting a new cell. Throughput) cannot be guaranteed. Throughput is important to know before a call is set up or handed over, especially in the case of real-time (RT) services. Similarly, it is important to know whether the load increases in order to check whether sufficient capacity is left in the candidate cells and to consider the capacity difference between the cells.

Methods for estimating throughput in GSM / EDGE cells based on measurement reports and dynamic frequency and channel allocation (DFCA) are described below. The mobile station periodically reports measurement reports from a large number of adjacent cells, for example, the 6 strongest cells, or 32 cells in the case of an extended measurement report, to its transmitting base station. Of course, any other suitable number of cells may be reported. The transmitting base station or radio resource controller calculates the throughput of each candidate cell and gives that information to the CRRM. Analysis / estimation of the C / I ratio and available slots (which is the throughput) is done using the DFCA one-way check for each channel allocation, ie handover, call setup, etc. Throughput is defined based on mobile station measurement reports and channel assignments (obtained from inter-cell DFCA reports) in each candidate cell.

In addition, background interference matrix (BIM) from each candidate cell can be used to obtain more accurate estimates. This requires BIM to be sent to the outgoing cell. The estimated C / I value per time slot can be mapped to the actual throughput value using a mapping table. The number of available time slots is taken into account when the maximum throughput value is defined.

Figure 8 shows the procedure for estimating C / I based on the MS measurement report and the DFCA resource table from other candidate cells. Figure 9 shows how C / I maps to actual throughput per time slot. The radio resource controller receives a measurement report from the mobile station that includes the reception level of each adjacent cell (the six most powerful adjacent cells and the signal level from the current cell). Up to 32 of the most powerful adjacent cells can be considered when improved measurement reports are used. The radio resource controller (including the DFCA algorithm) also receives information from Table 200 regarding the current channel allocation (reserved time slot per frequency) of the adjacent cell. Based on this information, the serviced radio resource controller forms a table 202 of all physical channels (time slots / transmitters) showing all available and occupied channels for each candidate cell. ..

The in-service radio resource controller (DFCA) can calculate the C / I for each time slot / frequency in each adjacent cell. This procedure is the same as the DFCA one-way check, but the BIM of the adjacent cell is not used. Calculating C / I for the largest multislot group only is not the only way to do it. Note, for example, that three slots with a good average C / I produce higher throughput than four slots with a bad C / I.

In addition, the C / I value can be calculated for one or more of the next best time slot combinations in addition to the maximum multislot group. It should be understood that this is just one method of calculating the C / I ratio, and other methods can be used. Based on the average C / I and the maximum number of available slots (whether the slots need to be sequential is a practical issue), the radio resource controller calculates the throughput scale for each candidate cell. .. This is sent to CRRM. In addition, the average C / I value per time slot can be sent to CRRM. This can then be mapped to throughput per time slot in CRRM, based on Figure 9.

FIG. 8 shows a procedure for estimating the carrier-to-interference ratio based on the mobile station measurement report and the DFCA resource table from other candidate cells. First, in step 1, a resource table 200 is defined for each cell and each frequency. This table 200 has an entry for each frequency f and each time slot T. Then, in step 2, table 202 is defined, which defines a resource table for each cell and each transmitter. In other words, this table contains information for each transmitter for available time slots. Therefore, the first table 200 includes an entry for each frequency and time slot, i.e. whether the transceiver uses that time slot at that frequency, and if so, the recognition of that transceiver. If a given frequency and time slot is not used, the table may be left blank or may have other suitable indications that a time slot of that frequency can be used.

The second table 202 shows, for each transceiver, which time slot is used by each transceiver. In step 3, the third step, the largest set of subsequent time slots or multislots is selected. In the example shown in table 202, it is time slot T₁Or time slot T₄Is.

In step 4, the carrier-to-interference ratio for each frequency and the associated slot that can accept the multislot is calculated. It is based on resource tables and measurement reports for other candidate cells. This is shown in Table 3 204. As is clear, the third table 204 is based on the first table 200, but at the selected frequency the time slot T₁Or time slot T₄Includes the calculated carrier-to-interference ratio for. The selected frequency is time slot T₁Or T₄Are all empty frequencies. Information from other cells in a table similar to table 200 is used. The carrier-to-interference ratio is calculated using the following equation. C / I = Divide the signal strength RxLev (c) of your cell (cell n) by the average (decibel) or worst (maximum) value of the measurement level (I) from other cell levels. If the measured cell (n-1) uses the same time slot, it must be considered as interference in cell n.

In step 5, the best mean carrier-to-interference ratio is selected. The average carrier-to-interference ratio can be mapped to a common throughput scale and multiplied by the number of time slots. This is done in step 6. In this regard, FIG. 9 illustrates how the carrier-to-interference ratio can be mapped to throughput. More specifically, FIG. 9 is a graph in which throughput per time slot is mapped to carrier-to-interference ratio.

Figure 9 shows the different statistical information collected for different multicode skims. This graph can be used to estimate throughput when the C / I is known. As is clear from this graph, the higher the interference and noise, the lower the throughput (and therefore the better the other cell). More specifically, FIG. 9 shows the adaptation of the link, i.e. the better the C / I, the less channels / error codes are available and the better the throughput. The reverse is also true, the lower the C / I, the more robust the required code skim. This graph / table must be in the CRRM or radio resource controller. This method can be used for any network where DFCA is used. However, known DFCA reports from adjacent cells do not receive information about the transmitter. Therefore, in order to use the embodiments of the present invention, some extra information, i.e. the number of transmitters used for each frequency / slot and the total number of transmitters in each cell, comes from adjacent cells. Added to the DFCA report.

This next embodiment describes a distributed method for estimating GSM / EDGE cell throughput based on measurement reports and dynamic frequency and channel allocation (DFCA). Figure 10a-c shows the procedure for estimating the C / I (maximum throughput) of each candidate cell based on the distributed mobile station measurement report and the DFCA resource table (and BIM) of each candidate cell. Similar to the embodiments described above, FIG. 9 shows how C / I actually maps to throughput per time slot.

The following steps are performed, as shown in Figures 10a-c. The mobile station measures the signal strength of a large number of adjacent cells, eg, 6 or 32 strongest adjacent cells in the case of an extended measurement report, as well as the current cell. Of course, in another embodiment of the invention, any other suitable number of measurements can be used. The mobile station periodically reports the measurement report to its transmitting base station. The transmitting base station uses the DFCA one-way check, i.e. estimates the maximum throughput based on the measurement report and the DFCA background interference matrix (BIM).

The transmitting base station transmits the measured values obtained in the previous step to each cell in the candidate list. Candidate cells estimate their maximum throughput based on measurements and BIM. This is done by each cell finding the maximum set of possible time slot combinations available (sequential time slots or distributed based on practice). Each cell then uses both the measured and BIM values to calculate the average C / I for these slot combinations (in the case of cells not in the measurement report). The average estimated C / I value per time slot is mapped to the actual throughput value per time slot using the mapping table. This can be done in the same manner as described for the embodiments described above. The number of available time slots is taken into account when the maximum throughput value is defined.

In some embodiments, maximum throughput is only needed if subsequent time slots are required. Otherwise, throughput per time slot is sufficient. Each cell then sends the calculated throughput (throughput per timeslot or C / I per timeslot) values to CRRM, which uses those values for the cell prioritization process. This method can be used for any network where DFCA is used. The measurement report needs to be multicast to other candidate cells, and the correspondingly estimated throughput value is forwarded to CRRM20.

A method for estimating throughput and load increase in a WCDMA cell will be described below. In the handover and call settings, all candidate cells can be prioritized by CRRM as described above. Therefore, every cell reports a large number of directives such as traffic load and throughput to CRRM. For low bitrate services, such as speech services (eg 12.2kbps), the measured load percentage values are sufficient to distinguish between the candidate cells, even if there is a capacity difference between them. However, for high bitrates (eg&gt; 50kbps), capacity differences between cells (Ptx_target downlink transmit power, number of transceivers, etc.) must be taken into account. For example, if a GSM candidate cell and a WCDMA candidate cell have the same load percentage but different maximum capacities, it is desirable to hand over to WCDMA (other parameters / directives included in the prioritization process). Assuming that does not affect this).

The WCDMA acceptance control algorithm is used to estimate the required transmit power, i.e., the load increase by the new user in each WCDMA candidate cell. Then the required maximum power and mobile measurement report (ρ)_c= E_c/ I_{o o}) Can be used to estimate the available throughput of each cell, i.e. check if the cell can support the requested QoS. Here we assume that the downlink direction limits load and throughput due to cell traffic asymmetry. Therefore, only downlink estimation is considered here. However, it is also desirable to estimate the upling load, especially if most connections generate approximately equal traffic in both directions. Similar techniques can be used for uplink estimation.

FIG. 11 which is a graph showing the downlink transmission power with respect to the load will be described. For each cell, the threshold Ptx_target for the maximum planned downlink transmit power is determined in FIG. This Ptx_target forms the optimum operating point (100% target load) of the cell load, and up to that point, the acceptance control of the radio resource controller can work. When the uncontrollable portion of the cell load, the real-time portion of transmit / receive power that cannot be dynamically adjusted as an NRT, exceeds this target limit, acceptance control at least means an immediate uplink UL load increase. Reject. Ptx_target is defined by the wireless network planning RNP parameter PtxTarget.

The total transmit power Ptx_total can be expressed as the sum of the power Ptx_nc generated by uncontrollable traffic and the power Ptx_nrt generated by non-real-time user controllable traffic. Ptx_total = Ptx_nc + Ptx_nrt (1) Here, the load percentage for both the total load (including both RT and NRT data) and the RT load can be calculated in the radio resource controller as follows.<maths num="1"><img file="JP4671995B2_D0001.tif" /></maths> For the RT radio access bearer RAB to be established, an uncontrollable load increase ΔPtx_nc must be estimated to obtain an estimated load percentage including the requested RAB radio access bearer. Then the RT load percentage is:<maths num="2"><img file="JP4671995B2_D0002.tif" /></maths>

The uncontrollable load increase ΔPtx_nc can be estimated by determining the maximum downlink DL transmit power of the wireless link. One radio access bearer RAB with the required guaranteed bit rate RImax and the target E for it_b/ N_{o o}Consider a single service call with = ρ. Ptx, ref represents the maximum DL transmission power of the reference service (for example, 12.2 kbit / s speech service can be used as the reference service), RI_refIs its bitrate, and ρ_refIs its target E_b/ N_{o o}If, the maximum power Ptx, max of the wireless link is determined from Ptx, ref by the following equation (linear form). ΔPtx = Ptx, max = MIN (RImax, eff Ptx, ref, Ptx_DPCH_max) (4) However, the "maximum effective bit rate correction factor" is defined by the following equation.<maths num="3"><img file="JP4671995B2_D0003.tif" /></maths>However, Ptx_DPCH_max is the absolute maximum value for the DL DPCH (dedicated physical channel) code channel transmission power determined by the parameter PtxDPCHMax.

When the maximum downlink DL transmit power for the requested radio access bearer RAB is defined, it is used to check or estimate the maximum bit rate Rmax (= throughput) that can be achieved with a given transmit power Ptx, max. can do. Therefore, the formula of "initial DL transmission power"<maths num="4"><img file="JP4671995B2_D0004.tif" /></maths>Can be changed. Knowledge of many parameter values is required to determine the transmit power. They are obtained as follows. ρ = E_b/ N_{o o}Is the energy / bit / noise density for the required bit rate. ρ_c= E_c/ N_{o o}Is the signal-to-interference ratio per chip (MS measurement report) of the perch channel measured by the terminal. W is the chip rate (3.84M chip). R is the bit rate specified by the network. Ptx_total is measured by the base station. Ptx and CPICH are wireless network planning parameters for determining the transmission power of the primary CPICH (common pilot channel). α is difficult to determine because it depends on various factors that can change rapidly. This is pre-fixed to 0.5.

Rather than finding the initial transmission power for a known bit rate R, the maximum achievable bit rate Rmax associated with knowing the maximum transmission power Ptx, max is determined as follows.<maths num="5"><img file="JP4671995B2_D0005.tif" /></maths> Similar to the above-described embodiment, this embodiment can be carried out in a decentralized manner or can be carried out intensively. In a decentralized form, the requested MS measurement report values are sent to candidate cells, which then calculate throughput and load increases and transfer them to CRRM. In the centralized form, MS measurement reports are sent directly to CRRM, where throughput and load increases are calculated. In this case, RI for different data rates_ref, Ρ_ref(Target E_b/ N_{o o}), P_{tx, ref}, P_tx-DPCH-max, Α and E_b/ N_{o o}Cell-specific Radio Network Planning (RNP) parameters, including tables, are also required by CRRM, which are kept in the database within the CRRM server and updated from the cell if they change.

Hereinafter, a similar load increase estimation method for the GSM cell will be described with reference to FIG. The load on a GSM cell is illustrated. Time slots can be completely dedicated to RT / NRT traffic or shared between different traffic classes. For real-time users, the guaranteed bandwidths are added together to give the total guaranteed bandwidth. The NRT load is not important to RT users as it can be flexibly controlled by the packet scheduler. Each GSM cell should have the number of time slots used for user data (TSL) based on the transceiver TRX and the number of reserved slots in the cell._max). The full load consists of RT and NRT data. TSL_total= TSL_RT+ TSL_NRT (1)

Therefore, the load percentage for both the total load (both dedicated and shared time slots, including both RT and NRT data) and the RT load can be calculated in the radio resource controller as follows:<maths num="6"><img file="JP4671995B2_D0006.tif" /></maths> Bitrate request R_reqThe available throughput R per time slot to estimate the new load percentage, including the requested RAB, for the RT RAB to be established in_{est, tsl}(Based on mobile measurements and BTS statistical information) must be estimated. The RT load percentage can then be approximated as:<maths num="7"><img file="JP4671995B2_D0007.tif" /></maths>

For example, currently Load_RT = 60%, TSL_maxAssuming = 30, throughput per TSL = 25kbps, requested service = 64kbps, then<maths num="8"><img file="JP4671995B2_D0008.tif" /></maths>The service requires at least 3TSL multislots. This does not mean that three time slots are assigned to the service, but gives a rough estimate of the load increase by new users. Throughput estimates are made on a cell basis, i.e. by collecting statistical information on the entire cell area and using a safe 95% estimate of available throughput per time slot. Alternatively, it is possible to estimate the maximum throughput of a true connection base based on movement measurements and BTS statistical information for a given user in each candidate cell. This estimation can be performed by using the existing DFCA algorithm in each candidate cell. This requires some additional signaling between cells.

In the next embodiment, a method of estimating GSM / EDGE cell throughput is used based on cell interference statistics, mobile station location, and mobile station measurement reports. In this embodiment, interference statistical information from ongoing calls in each cell as a function of mobile station location (eg, a cumulative distribution function with a 90-95% outage probability) is collected. The cell area (or other form of area) is divided into smaller areas for collecting statistical information. The values collected as statistical information may be based on the actual interference level reported by the mobile station, or as a function of the received signal level based on the received bit error rate, which leads to interference. You may map and memorize it. Each time there is a channel assignment, i.e. during handoff or call setup, the C / I (Carrier vs. Interference) value is the mobile station measurement report (given the value for C), as well as the mobile station position and interference statistics ( It can be estimated from (given the value of I).

The estimated C / I value can then be mapped to throughput per time slot. The number of available time slots is taken into account when the maximum throughput value is defined. Interference statistical information can be collected as a function of path loss if the location of the mobile station cannot be given (the level of reception of the signal from the base station is a measure of the radius of the cell and within the cell. Gives instructions on the location of the mobile station). This is not as accurate as position-based statistical information, but can give more accurate estimates than a single average statistical information over the entire cell range. Similar statistical information can be collected for the uplink direction.

A single statistical piece of interference, C / I or throughput can be collected for all cells. This is not very accurate. This is because the interference is not the same across areas of the cell and does not take into account changes in interference. By adding more accuracy, more processing power and signaling are required. FIG. 12 shows the procedure for collecting interference statistical information as a function of the position of the mobile station. As is clear, cell 100 is subdivided into a plurality of smaller areas 102. For each of these areas, the carrier-to-interference ratio is calculated using the mobile station measurement report to give C and the mobile station position and mobile station measurement report statistical information to give I. When C / I statistical information per geographic area is collected, the C / I value for the new connection is only a function of the location of the MS, not a function of the current measurement (C).

Interference (I) (or C / I) statistics are collected for each small area with coordinates (X and Y), and 90-95% of those statistics (curve 110 in Figure 12). ) Is stored in the table (x vs y). FIG. 13 showing a procedure for collecting interference statistical information as a function Rx_level (path loss) will be described. In this embodiment, the cell is divided into a plurality of ring-shaped regions at each distance from the base station. In this embodiment, the carrier-to-interference ratio is calculated. The carrier wave is calculated as described with reference to the previous figure. The interference value is calculated from a function of path loss in the air interface.

See again Figure 9, which shows how the carrier-to-interference ratio maps to throughput. Collection of statistical information must be carried out at each base station. The base station can report the interference matrix to CRRM, which then maps the mobile MS measurement report, the location of the mobile MS and the available time slots to maximum throughput. Alternatively, the measurement report of the mobile station MS can be transferred to each candidate cell, and the candidate cell can calculate the corresponding throughput value and transfer it to CRRM. Different interference / load conditions appear during different times of the day, so some oblivion factor (eg, filter the data with an IIR filter: new_stat_value = 0.98 * old_stat_value + 0.02 * new_sample) to fill the collected data. Must be.

It will be clear that one or more methods for determining throughput can be used for the same network. Different systems can use different methods. It is possible that the same system uses more than one method to determine throughput. In another embodiment of the invention, it will be clear that throughput is not determined and other parameters such as load may be determined. The parameters can be determined using a method similar to that described above.

The method according to the present invention will be described below. The signal-to-interference ratio (SIR) calculation can be cell-based or connection-based. Connection-based estimation requires a significant amount of signaling as it needs to be done for each allocation (handover, call setup). Cell-based estimates, on the other hand, only require one (or one or more in certain embodiments of the invention) statistical information for each cell, which may be other, such as load. Can be reported to CRRM along with periodic reports. Connection-based throughput / SIR estimates can be calculated as follows: Intensive throughput calculation based on DFCA; Distributed throughput calculation based on DFCA; Throughput calculation based on BEP (bit error probability) and / or C / I statistical information, as well as knowledge of the location of the mobile station MS.

The statistical method used for the cell is as follows. --Collect BEP values from the measurement report for each ongoing call in each GSM / GERAN cell. --Map them to the C / I value (Figure 15) and add the power control difference (MaxTx power-actual Tx power) to the C / I value. In the absence of DL power control, BEP pairs (MEAN_BEP, CV_BEP) can be mapped directly to throughput / TSL based on Table 1 (included below). --Add those values to the C / I statistics. --C / I Periodically report 90-95% of statistical information to CRRM.

CRRM allows you to map the C / I statistics for each cell to Throughput / TSL using, for example, Table 1 (Direct C / I vs. Throughput Table) based on the capacity of the cell. For EDGE-enabled cells, a different mapping table must be used for cells that only GMSK can. If all cells have the same capacity (eg, EDGE), cell statistics can be collected directly from the individual BEPs to give throughput / TSL values.

If the proportion of high bitrate users in a cell is high, it may be much more attractive than a cell, which is mostly low bitrate users, and vice versa. This can be resolved by collecting statistical information for a set of traffic classes and reporting their different values to CRRM separately, or by weighting the statistical information in proportion to the distribution of users. Can be done. Benchmark services can also be used for statistical information purposes. For example, only measurements from AMR 12.2 kbit / s users can be collected as statistical information. It was assumed that this type of report was not needed from WCDMA cells. However, in certain embodiments of the invention, reports in this form may be used with CDMA cells.

<tables num="1"><img file="JP4671995B2_D0009.tif" /></tables>

<figref num="1">It is a figure which shows the network which consists of the system of a plurality of different wireless access technologies.</figref><figref num="2">It is a figure which shows the common radio resource management which controls a plurality of radio access systems.</figref><figref num="3">It is a figure which shows the CRRM concept of a handover function.</figref><figref num="4">It is a figure which shows the event sequence in the handover process.</figref><figref num="5">It is a figure which shows the priority determination algorithm of the handover judgment.</figref><figref num="6">It is a figure which shows one Embodiment of this invention which consists of a plurality of CRRMs.</figref><figref num="7">It is a figure which shows the 2nd Embodiment of this invention which consists of a plurality of CRRMs.</figref><figref num="8">It is a figure which shows the 1st method of determining a throughput.</figref><figref num="9">It is a figure which shows the place which maps the C / I ratio to the throughput.</figref><figref num="10a">It is a figure which shows the 2nd method of determining a throughput.</figref><figref num="10b">It is a figure which shows the 2nd method of determining a throughput.</figref><figref num="10c">It is a figure which shows the 2nd method of determining a throughput.</figref><figref num="11">It is a graph which shows the downlink transmission power with respect to the load in the 3rd method of determining a throughput.</figref><figref num="12">It is a figure which shows the 4th method of determining a throughput.</figref><figref num="13">It is a figure which shows the modification of the method shown in FIG.</figref><figref num="14">It is a figure which shows the load of a GSM cell.</figref><figref num="15">It is a graph which shows the bit error rate as a function of a carrier wave-to-interference ratio.</figref>

Code description

2 mobile station 20 CPRM (Common Radio Resource Management) 30 cell resources