WO2011072440A1 - Handover triggering method for wireless network and apparatus thereof - Google Patents

Abstract

Disclosed are a handover triggering method for a wireless network and an apparatus thereof, which are used to solve the technical defects of the dropped calls caused by the imbalance between uplink and downlink coverage in a multi-antenna system, and the misjudgment easily caused by adopting the same handover threshold for all the Mobile Stations (MSs) and so on. In the present invention, a base station modified, according to the own capacity and channel conditions of the MS, the downlink Carrier to Interference plus Noise Ratio (CINR) reported from the MS, and performs handover decision according to the modified downlink CINR, which enables the self-adaptive handover threshold to the utmost extent and reduces the misjudgment during the handover of the MS. Meanwhile, the present invention also takes into account the situation of imbalance between uplink and downlink coverage, and the handover decision is performed for the uplink CINR at the BS side when the MS transmits at full power, which allows the MS to avoid the dropped calls caused by not handing over when the uplink exceeds the coverage range. Based on the above characteristics, the present invention can improve the performance of multi-antenna system and the customer satisfaction.

Description

 Switching trigger method and device for wireless network

 The present invention relates to the field of wireless communication technologies, and in particular, to a handover triggering method and apparatus for a terminal for adapting different processing capabilities of a wireless network and an uplink and downlink coverage imbalance system. Background technique

 With the improvement of system processing power, a new generation of wireless communication systems, such as Wimax and LTE, widely use multi-antenna technology. With appropriate transmit signal form and receiver design, multi-antenna technology can not significantly increase wireless communication. At the same time as the system cost, the system capacity is increased. The Wimax system is taken as an example to introduce the multi-antenna technology.

 Wimax supports multiple multi-antenna technologies such as MIMO (Multiple Input Multiple)

Output, Multiple Input Multiple Output) technology, CDD (Cyclic Delay Diversity) technology, Beamforming technology, these multi-antenna technologies can greatly increase system capacity.

The WiMAX 16e protocol defines three MIMO transmit matrices that use space-time coding, namely Matrix A, Matrix B, and Matrix C. Matrix A uses the transmit diversity structure to obtain spatial diversity gain. The spatial diversity gain means that the signal of a single antenna system may have deep fading due to the fading characteristics of the wireless channel. After using multi-antenna technology, usually the antennas are far enough apart to ensure that the signal fading of different antennas is relatively independent. Therefore, the signal-to-noise ratio fluctuation of the combined received signal will become smooth, thereby improving the received signal quality. Matrix B uses a spatial multiplexing structure to obtain multiplexing gain. The spatial multiplexing gain refers to the improvement of data throughput/transmission rate under the same transmission power and the same bandwidth. The spatial multiplexing gain can be obtained by transmitting multiple parallel data streams on the same time-frequency resource, and these multiplexed data streams are distinguished by different antennas. Matrix C uses a hybrid structure of diversity and multiplexing to obtain both multiplexing gain and diversity gain. For the downlink common channel, the protocol stipulates that space-time coding cannot be used. In this case, the CDD technique can be used to obtain the diversity gain. CDD technology improves the coverage of common channels by transmitting different delayed copies of the same data stream on different antennas to achieve multipath diversity. According to the simulation results, the CDD of 2 antennas has at least 2 dB gain than the single antenna, and the CDD of 4 antennas has more than 1 dB of gain than the CDD of 2 antennas. In addition, the combination of CDD and MIMO Matrix A or Matrix B for the data channel can further improve diversity performance or diversity plus multiplexing performance.

 Downforming beamforming (Beamforming) is that the transmitting end weights and transmits the data first, forming a narrow transmitting beam, and aligning the energy with the target user, thereby improving the demodulation signal-to-noise ratio of the target user, which is particularly suitable for improving the throughput of the cell edge user. effective. Beamforming can obtain array gain, diversity gain and multiplexing gain. Array gain refers to the improvement of the average signal-to-noise ratio at the receiving end under the premise of the same total transmit power. By coherently combining the signals, the received signal-to-noise ratio can be improved. . Beamforming technology and MIMO technology can be used together to achieve greater gain.

MIMO, CDD and Beamforming are all implemented in the downlink through BS (Base Stastion). Because BS has strong processing capability, it will generally be equipped with 4T4R (4 rounds and 4 receivers), 4T8R (4 rounds and 8 receivers) and other antennas. Capability, while MS (Mobile Station) is limited by the processing capability and mobility, and generally only configures the antenna capability of 1T1R (1 send 1 receive) or 1T2R (1 send 2 receive), so the uplink multi-antenna The technology is also implemented by the BS. There are two main technologies: uplink multi-antenna receive diversity and uplink CSM (Collaborate Spatial Multiplex). Uplink multi-antenna receive diversity is the most commonly used multi-antenna technology. The signals received by multiple antennas are coherently combined at the base station side to obtain the array gain. The array gain refers to the receiver with the same total transmit power. The amount of improvement in the average signal to noise ratio. By coherently combining the signals, the array gain can be obtained for various multi-antenna systems, that is, the multi-antenna technique can be used to improve the received signal-to-noise ratio. Compared with single-antenna reception, with 2 antenna diversity reception, the uplink coverage will improve by more than 3dB, and the 4-antenna diversity reception can further improve l-2dB. Over-multiplexing to increase the capacity of the uplink. When selecting a cooperative terminal, to ensure the orthogonality between users, there is a high requirement for the scheduling algorithm.

 The excellent multi-antenna technology will greatly improve the spectrum efficiency, reduce the cost per bit, effectively improve the user experience, improve coverage, improve the throughput of cell edge users, reduce the number of base stations, and reduce network construction and maintenance costs.

 Due to the limited processing power and transmit power of the MS, the coverage of the WiMAX system is usually limited by the uplink, that is, the uplink coverage is less than the downlink coverage. As can be seen from the above description, the multi-antenna technology mainly increases the downlink gain in the BS side application, although the uplink multi-antenna receive diversity can increase the gain by more than 3 dB, and the uplink due to the MIMO and Beamforming techniques that simultaneously obtain multiple gains. The gain obtained by the antenna is far less than the gain obtained by the multi-antenna in the downlink, so the multi-antenna technology exacerbates the coverage imbalance between the uplink and the downlink. Figure 1 is a schematic diagram of the difference in coverage when uplink, downlink, and multi-antenna technologies are used. As shown in the figure, the inner circle range 1 indicates the uplink coverage, that is, the MS is within this range, and the BS can receive the uplink signal of the MS. The outer circle range 2 indicates the downlink coverage when MIMO and Beamforming are not used; the sector area range 3 refers to the downlink coverage of MS 1 when Beamforming is enabled, and the MS has a capability of 1T2R.

 After the multi-antenna technology is widely used, when there are multiple MSs with multiple processing capabilities in a cell, such as a single antenna MS, a MIMO-capable MS, and a MIMO and Beamforming MS, the existing Wimax switching mechanism will be adopted. Come ^ ί艮 big impact.

The existing Wimax cell handover mechanism is mainly triggered according to the value of the downlink CINR (Carrier to Interference plus Noise Ratio), because the downlink transmission power of the BS is fixed, in the case of a single antenna. The value of the downlink CINR can be used to determine the distance from the BS, and the uplink transmit power is variable. To reduce the uplink interference, the BS will indicate the MS with lower CINR and the MS with lower CINR. Power, unless the MS is already full power. The BS notifies the handover threshold and the relative handover threshold to the MS through the broadcast message, and the MS measures the downlink CINR, and if the handover threshold is reached, the scan is initiated, and the record is recorded. If the CINR of the neighboring cell is smaller than the relative handover threshold, the downlink CINR of the neighboring cell initiates the handover. If a BS load is severe, the BS will only initiate the handover by the MS with poor downlink CINR.

 The use of multi-antenna technology will increase the individual difference of MS. Whether to use multi-antenna technology and which multi-antenna technology is used is related to the capability of MS, there will be multiple MS access under one BS cell. The downlink CINR of the MS is related to the multi-antenna technology used by the downlink in addition to the distance of the BS. The downlink CINR of the MS at the cell edge that enables MIMO and/or Beamforming is not necessarily more than that of the non-MIMO non-Beamforming. The downlink CINR of the MS in the center of the cell is low. Moreover, the multi-antenna technology exacerbates the coverage imbalance between the uplink and the downlink. That is to say, due to the use of multi-antenna technology, when the MS is at the edge of the cell, the downlink CINR is still 4 艮, but the uplink has dropped. In addition, all MSs in a cell now use the same handover threshold. In the multi-antenna design, the downlink CINR cannot fully represent the location of an MS in the cell. MSs with different capabilities should have different switching thresholds. Summary of the invention

 The object of the present invention is to provide an enhanced handover triggering method for a wireless network, which is used to solve the call drop caused by the uplink and downlink coverage imbalance in a multi-antenna system, because the same handover threshold is easily caused for all MSs. Technical defects such as misjudgment.

 The present invention uses the following technical solutions. The handover triggering method of the present invention mainly includes: a handover triggering method for a wireless network, the method comprising:

 Correcting a downlink carrier to interference and noise ratio (CINR) of the mobile station (MS), and performing handover decision according to the corrected downlink CINR of the MS, and if the corrected downlink CINR of the MS reaches a handover threshold, notify the The MS performs the handover.

 Further, the modification is specifically:

According to the MS, the average difference between the CINR before and after the multi-antenna technology is enabled or changed The CINR of the MS is corrected; or the downlink CINR of the MS is corrected according to a preset CINR average correction difference corresponding to each multi-antenna technology type.

 Further, in the case that the downlink coverage is unbalanced, the handover decision is performed in combination with the uplink CINR and the transmit power, and the specific steps are:

 It is determined whether the MS is in an uplink full power transmission state, and if it is in a full load transmission state, it continues to determine whether the uplink CINR of the MS reaches a handover threshold, and if the handover threshold is reached, the MS is notified to perform handover.

 Based on the above method, the present invention also provides a handover triggering apparatus for a wireless network, including:

 a downlink CINR collector, configured to collect downlink CINR information on the MS;

 a downlink CINR correction information base for storing a correction parameter for correcting the MS downlink CINR;

 a handover determiner, configured to modify a CINR reported by the MS according to a modified parameter of the downlink CINR correction information store, and perform a handover decision according to the corrected downlink CINR value of the MS;

 The BS signaling processing module is configured to process the interaction signaling with the MS, and notify the MS to initiate the handover procedure according to the handover decision information of the handover decider.

 Further, the correction parameter stored in the downlink CINR correction information base is an average difference between the CINR calculated by the downlink CINR collector and the CINR before or after the multi-antenna technology is enabled or changed; the handover decider is according to the The MS corrects the CINR of the MS by the average difference between the CINR before and after the multi-antenna technology is enabled or changed.

Further, the correction parameter stored in the downlink CINR correction information base is a preset CINR average correction difference value corresponding to each multi-antenna technology type; the handover decider is corresponding to each multi-antenna technology type. The CINR average ^ ί ' 爹 positive difference is positive for the downlink CINR of the MS. Further, the device further includes:

 An uplink CINR/power collector, configured to collect uplink CINR information and transmit power information of the MS;

 The handover determiner is further configured to determine, according to the transmit power of the MS obtained by the uplink CINR/power collector, whether the MS is in an uplink full power transmission state, and if in a full load transmission state, continue to determine an uplink of the MS. Whether the CINR reaches the handover threshold, and if the handover threshold is reached, the handover decision information is sent to the BS signaling processing module.

 In the present invention, the base station corrects the downlink CINR reported by the MS according to the MS's own capabilities and channel conditions, and performs handover decision according to the modified downlink CINR, which can maximize the handover threshold adaptation and reduce the misjudgment of the MS during handover. At the same time, the present invention also considers the case where the uplink and downlink coverage is unbalanced, and performs handover decision on the uplink CINR of the MS when the full power is transmitted on the base station side, so that the MS does not switch because the uplink exceeds the coverage range; The invention can improve the performance and user satisfaction of a multi-antenna system. DRAWINGS

 1 is a schematic diagram of differences in coverage when uplink, downlink, and multi-antenna technologies are used; FIG. 2 is a schematic structural diagram of an enhanced handover triggering apparatus for a wireless network according to the present invention; FIG. 3 is an enhanced type of the present invention for wireless networks. Schematic diagram of a simplified device structure for handover triggering; FIG. 4 is a flow chart showing a specific implementation of maintaining and updating a CINR correction difference value of an MS in an enhanced handover trigger of a wireless network according to the present invention;

 5 is a flow chart showing a specific implementation of an enhanced handover triggering method for a wireless network according to the present invention;

6 is a flow chart of a specific implementation of an enhanced handover triggering method for a wireless network of the present invention. The basic idea of the present invention is: the base station corrects the downlink CINR of the MS according to the difference between the downlink and the CINR of the MS enabled multi-antenna technology, and performs handover decision according to the corrected CINR value; or for different The antenna technology type sets different downlink CINR correction differences, and corrects the downlink CINR reported by the MS according to the multi-antenna technology type used by the MS, and performs handover decision according to the corrected CINR value; in the case where the uplink and downlink coverage is unbalanced The BS also detects the uplink CINR, and notifies the MS to initiate the handover when the MS is already transmitting at full power and reaches the handover threshold.

 The technical solutions of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

 2 is a schematic structural diagram of an enhanced handover triggering apparatus for a wireless network according to the present invention. The apparatus configuration is applicable to a scenario in which a downlink CINR of each MS is corrected according to an average difference between CINRs before and after multi-antenna technology. When the technical solution is adopted, the actual switching thresholds of each MS are different. The device can implement the switching threshold control at the user granularity, and improves the accuracy of the downlink CINR switching threshold of each MS. The apparatus includes the following parts: a downlink CINR collector 101, configured to collect downlink CINR information of >3⁄4 on the MS; and calculate a multi-antenna technology enabling or changing downlink of the MS after the multi-antenna technology of the MS is enabled or changed CINR correction difference;

 The MS downlink CINR information base 102 is configured to save the downlink CINR correction difference of each MS. If the MS does not enable the multi-antenna technology, the corresponding correction difference is 0.

 The uplink CINR/power collector 103 is configured to collect uplink CINR information and transmit power information of the MS.

 The handover determiner 104 is configured to modify, according to the downlink CINR correction difference of each MS, the downlink CINR of the MS collected by the downlink CINR collector, and perform handover decision according to the modified value, if there is an imbalance between the uplink and downlink coverage, The handover decision is made in combination with the uplink CINR and the transmit power.

a BS signaling processing module 105, configured to process interaction signaling with the MS, according to the handover decider The handover decision information informs the MS to initiate the handover procedure.

 The specific implementation steps of the enhanced handover decision for the wireless network of the present invention are described in detail below.

 FIG. 4 is a flowchart of a specific embodiment of a CINR correction difference for maintaining and updating an MS based on the handover triggering apparatus shown in FIG. 2 according to the present invention. The specific steps are as follows:

 Step 401: The MS initially accesses the network.

 Step 402: The MS downlink CINR information base 102 creates a corresponding downlink CINR information item for the MS, and sets the CINR correction difference value to zero.

 Step 403: The MS performs capability negotiation with the BS.

 Step 404: Determine whether the MS needs to enable or change the multi-antenna technology, and if necessary, go to step 405; otherwise, go to step 408;

 Step 405: The BS signaling processing module 105 notifies the MS of the downlink CINR collector 101 and the MS downlink CINR information base 102 after a certain (MIMO A/B/C, Beamforming, and MIMO+Beamforming) multi-antenna technology is enabled or changed. The type of multi-antenna technology enabled;

 Step 406: The downlink CINR collector 101 obtains an average value of the CINR difference values before and after the enable or change according to the downlink CINR value of the MS enable or change, and notifies the MS downlink CINR information base 102;

 Step 407: The MS downlink CINR information base 102 records the multi-antenna technology type used by the MS and the updated CINRJ爹 positive difference value;

 For example, after the MS switches from a single antenna to MIMO A, the CINR is increased by 4 dB, the CINR correction difference is 4, and then the MIMO A is cut to MIMO C, and the CINR is reduced by IdB, and the CINR correction difference is 3.

 Step 408: If the MS is in the network, whether to enable/change the multi-antenna technology, if yes, go to step 405, otherwise go to step 409.

Step 409: The MS exits the network, and the process ends. FIG. 5 is a flowchart of processing performed by the apparatus according to FIG. 2 for performing enhanced handover triggering according to the present invention, and the specific steps are as follows:

 Step 501: The uplink CINR/power collector 103 checks whether the MS is already uplink full power transmission, if yes, go to step 502, otherwise go to step 504;

 Step 502: The uplink CINR/power collector 103 reports the uplink CINR of the MS to the switch determiner 104.

 Step 503: The handover determiner 104 determines whether the uplink CINR of the MS has reached or is less than the uplink handover threshold, if yes, go to step 507, otherwise go to step 504;

 Step 504: The downlink CINR collector reports the received MS downlink CINR to the handover determiner 104;

 Step 505: The handover determiner 104 corrects the downlink CINR value of the MS according to the downlink CINR correction value of the MS in the MS downlink CINR information database, and obtains the corrected downlink CINR value of the MS.

 The method for modifying the downlink CINR value of the MS by the BS of the present invention is: after receiving the downlink CINR reported by the MS, the BS subtracts the downlink CINR correction difference of the MS from the downlink CINR value currently reported by the MS, so that the MS is corrected. Downstream CINR value;

 Step 506: The handover determiner 104 determines whether the corrected downlink CINR value of the MS has reached or is less than the downlink handover threshold. If yes, go to step 507; otherwise, go to step 501;

 Step 507: The handover decider 104 notifies the BS signaling processing module 105 of the MS information that needs to be switched;

 Step 508: The BS signaling processing module 105 notifies the MS to initiate a handover procedure.

3 is a simplified block diagram of an apparatus for enhanced handover triggering of a wireless network of the present invention, the apparatus structure being adapted to set a fixed CINR average difference for each type of multi-antenna technology type, and for each MS used The multi-antenna technique type uses the above fixed CINR average difference to correct the downlink CINR of the MS. The scheme is relative to the scheme of Figure 2, for each The accuracy of the control of the user switching threshold is not as high as that of the scheme of Fig. 2, but the implementation is simpler and more efficient. The simplified enhanced switching trigger device includes:

 The downlink CINR collector 201 is configured to collect downlink CINR information on the MS, and the multi-antenna downlink CINR switching threshold information base 202 is configured to save a preset CINR average correction difference corresponding to each multi-antenna technology type. If the MS does not enable multiple antennas, the value is

0.

 The uplink CINR/power collector 203 is configured to collect uplink CINR information and transmit power information of the MS.

 The handover determiner 204 is configured to modify, according to the CINR average correction difference corresponding to each multi-antenna technology type, the downlink CINR of the MS collected by the downlink CINR collector, and perform handover decision according to the modified value, if there is uplink and downlink coverage. In the case of balance, the handover decision is made in combination with the uplink CINR and the transmit power.

 The BS signaling processing module 205 is configured to process the interaction signaling with the MS, and notify the MS to initiate the handover procedure according to the handover decision information of the handover determiner.

 FIG. 6 is a flowchart of a handover triggering process of the simplified device based on the enhanced handover trigger of FIG. 3, which specifically includes the following steps:

 Step 601: The uplink CINR/power collector 203 checks whether the MS is already uplink full power transmission, if yes, go to step 602, otherwise go to step 604.

 Step 602: The uplink CINR/power collector 203 reports the uplink CINR of the MS to the handover decider 204.

 Step 603: The handover determiner 204 determines whether the uplink CINR of the MS has reached or is less than the uplink handover threshold. If yes, go to step 607. Otherwise, go to step 604.

 Step 604: The downlink CINR collector reports the received MS downlink CINR to the handover decider 204.

Step 605: The handover determiner 204 switches the threshold information base 202 according to the multi-antenna downlink CINR. The CINR average correction difference corresponding to the multi-antenna technology type used by the MS corrects the downlink CINR value of the MS.

 Step 606: Whether the downlink CINR correction value of the MS has reached or is less than the downlink handover threshold, if yes, go to step 607, otherwise go to step 601.

 Step 607: The handover decider 204 notifies the BS signaling processing module 205 of the MS information that needs to be handed over.

 Step 608: The BS signaling processing module 205 notifies the MS to initiate a handover procedure.

 The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

Claims

Claim  A handover triggering method for a wireless network, the method comprising: correcting a downlink carrier to interference and noise ratio (CINR) of a mobile station (MS), and correcting the downlink according to the MS The CINR performs a handover decision. If the corrected downlink CINR of the MS reaches a handover threshold, the MS is notified to perform handover.  The method according to claim 1, wherein the modifying is specifically: correcting the CINR of the MS according to an average difference between the CINR of the MS before or after the multi-antenna technology is enabled or changed.  The method according to claim 1, wherein the modification is specifically: correcting a downlink CINR of the MS according to a preset CINR average correction difference corresponding to each multi-antenna technology type.  The method according to claim 1 or 2, wherein the handover decision is performed in combination with an uplink CINR and a transmit power in a case where the downlink coverage is unbalanced, and the specific steps are: determining whether the MS is on the uplink The power transmission state, if in the full-load transmission state, continues to determine whether the uplink CINR of the MS reaches a handover threshold, and if the handover threshold is reached, notifying the MS to perform handover.  5. A handover triggering apparatus for a wireless network, comprising:  a downlink CINR collector, configured to collect downlink CINR information reported by the MS;  a downlink CINR correction information base for storing a correction parameter for correcting the MS downlink CINR;  a handover determiner, configured to modify a CINR reported by the MS according to a modified parameter of the downlink CINR correction information store, and perform a handover decision according to the corrected downlink CINR value of the MS; The BS signaling processing module is configured to process the interaction signaling with the MS, and notify the MS to initiate the handover procedure according to the handover decision information of the handover decider. The device according to claim 5, wherein the correction parameter stored in the downlink CINR correction information base is that the MS calculated by the downlink CINR collector is enabled or changed before and after multi-antenna technology The average difference value; the handover decider corrects the CINR of the MS according to the MS's average difference between the CINR before or after the multi-antenna technology is enabled or changed.  The apparatus according to claim 5, wherein the correction parameter stored in the downlink CINR correction information base is a preset CINR average correction difference corresponding to each multi-antenna technology type; the handover decision The device corrects the downlink CINR of the MS according to the CINR average correction difference corresponding to each multi-antenna technology type.  The device according to claim 6 or 7, wherein the device further comprises: an uplink CINR/power collector, configured to collect uplink CINR information and transmit power information of the MS;  The handover determiner is further configured to determine, according to the transmit power of the MS obtained by the uplink CINR/power collector, whether the MS is in an uplink full power transmission state, and if in a full load transmission state, continue to determine an uplink of the MS. Whether the CINR reaches the handover threshold, and if the handover threshold is reached, the handover decision information is sent to the BS signaling processing module.