WO2011123982A1

WO2011123982A1 - Base station, mobile euipment and method in wireless heterogeneous network

Info

Publication number: WO2011123982A1
Application number: PCT/CN2010/000458
Authority: WO
Inventors: 庞继勇; 王栋耀; 王钧; 刘建国; 蒋琦; 沈钢
Original assignee: 上海贝尔股份有限公司; 阿尔卡特朗讯
Priority date: 2010-04-07
Filing date: 2010-04-07
Publication date: 2011-10-13
Also published as: CN102823299B; CN102823299A

Abstract

The present invention provides a base station in wireless communication network. The base station includes a transmitting unit, which is configured to transmit messages to mobile equipments and neighbour base stations; a receiving unit, which is configured to receive messages from the mobile equipments and the neighbour base stations; and a handoff unit, which is configured to perform handoff based on network performance and signal strength according to the messages from mobile equipments and neighbour base stations. The present invention further provides a mobile equipment including a transmitting unit, which is configured to transmit messages to a base station; a receiving unit, which is configured to receive messages from base stations, and a handoff unit, which is configured to perform handoff based on network performance and signal strength according to the messages from the base stations. Additionally, the present invention provides a corresponding handoff method. The present invention can provide a higher service rate, and therefore provide a better user experience especially for the users at the edge of a cell.

Description

Base station, mobile device and method in wireless heterogeneous network

The present invention relates to the field of wireless communications, and in particular, to a base station, a mobile device, and a method for use in a wireless heterogeneous network. Background technique

Mobility is an important feature of wireless cellular communication systems. Therefore, the most basic requirement for the system is that a good cell handover criterion is a prerequisite for obtaining a better quality of service (QoS) when the mobile device enters the network or moves from one cell to another. In general, continuous services are implemented by switching from one cell to another (which can be considered as a special case of handover). Handover refers to changing the channel (frequency, time slot, spreading code, or a combination thereof) associated with the current connection when the call is in progress. As shown in Fig. 1, when the mobile device MS enters the service area of the base station BS2 from the service area of the base station BS1, the handover from BS1 to BS2 is performed in accordance with the signal strength to ensure continuous service of the mobile device MS. This is detailed in Document 1 (Q. An Zeng, D. Agrawal, "Handof f in Wireless Mobi le Networks," Chap 1 in Handbook of Wireless Networks and Mobile Computing, John Wiley & Sons, Inc. 2002). description.

In any cellular telecommunication network, cell handover is very important and has a large impact on system performance. Since handover is generally initiated by passing through cell boundaries or deterioration of signal quality in the current channel, a well-designed cell handover scheme has outstanding value when the size of the cell is relatively small and the deployment of the cell becomes complicated. For example, the heterogeneous network (HTN) involved in the 3GPP LTE evolution described in Document 2 (3GPP TR 36. 814, "More Advancements for E-UTRA Physical Layer Aspects, " vl. 5. 2, Dec. 2009) Because of its denser structure and more complex cell deployment, the more frequent handover of mobile devices, the design of the handover scheme will greatly affect the performance of the HTN network.

Currently, existing cell handover criteria are based primarily on received signal strength/quality or the relative distance between the mobile device and the base station to determine when to switch and to which cell. Obviously, cell switching based on signal strength or relative distance does not take into account its network. The impact of the overall throughput of the network. In other words, the ideal cell handover should be based not only on the measurement of the received signal, but also on the optimization of overall system performance (including user fairness).

The existing cell handover scheme can only try to provide satisfactory signal quality for the target mobile device, but cannot guarantee that the performance of the network does not degrade after the cell handover is performed. Therefore, there is a need for a cell switching scheme based on network throughput and user fairness. Summary of the invention

In order to solve the above problems, the basic idea of the present invention is to improve the existing cell handover scheme with as little modification as possible. In particular, the present invention proposes an enhanced handover decision condition based on network throughput that is redefined in the form of a product of the average user service rate. In the present invention, the switched target base station not only provides acceptable signal strength, but also provides maximum network throughput. That is, if the signal of the current base station is still at an acceptable level, the handover is performed only when the total network throughput after the possible handover is greater than the network throughput before the handover (eg, greater than a certain difference); If the signal of the current base station is below an acceptable level, the handover is performed and the target base station not only provides acceptable signal strength, but also provides maximum network throughput.

Specifically, an aspect of the present invention provides a base station in a wireless communication network, comprising: a transmitting unit configured to transmit a message to a mobile device and a neighboring base station; and a receiving unit configured to receive from the mobile device and adjacent a message of the base station; and a handover unit configured to: perform handover based on network performance and signal strength based on messages from the mobile device and the neighboring base station.

Preferably, the network performance includes network throughput defined in the form of an average service rate of the mobile device in the network.

Preferably, the switching unit is configured to: if the current signal strength of the mobile device is still at an acceptable level, only the network throughput after the possible handover is greater than the current network throughput specific threshold and still provide acceptable The switching is performed at signal strength; if the current signal strength of the mobile device is below an acceptable level, the mobile device is switched to a base station that is capable of providing not only acceptable signal strength but also providing maximum network throughput; If there is no base station capable of providing acceptable signal strength, or Switching to a base station that provides acceptable signal strength results in a decrease in network throughput, and the mobile device is switched to the base station with the strongest signal.

Preferably, the switching unit is configured to: estimate the average service rate of the mobile device based on Shannon's theory or modulation and coding scheme mapping, thereby obtaining network throughput.

Preferably, the transmitting unit and the receiving unit of the base station exchange information of the associated mobile device with the neighboring base station via the X2 interface, and the transmitting unit of the base station transmits the information to the newly connected mobile device via the air interface.

Preferably, the wireless communication network is an LTE heterogeneous network, and the base station includes a macro base station, a micro base station, a home base station, and a relay base station.

Another aspect of the present invention provides a handover method performed by a base station in a wireless communication network, comprising the steps of: receiving a message from a mobile device and a neighboring base station; and based on network performance based on messages from the mobile device and the base station And signal strength to perform the switch.

Preferably, network performance includes network throughput defined in the form of an average service rate of mobile devices in the network.

Preferably, if the current signal strength of the mobile device is still at an acceptable level, then only when the network throughput after the possible handover is greater than the current network throughput specific threshold and still provides acceptable signal strength The handover; if the current signal strength of the mobile device is below an acceptable level, the mobile device is switched to a base station that is capable of providing not only acceptable signal strength but also providing maximum network throughput; A base station that accepts signal strength, or switching to a base station that provides acceptable signal strength, results in a decrease in network throughput, and the mobile device is switched to the base station with the strongest signal.

Preferably, the mobile device average service rate is estimated based on Shannon's theory or modulation and coding scheme mapping to obtain network throughput.

A still further aspect of the present invention provides a mobile device, comprising: a transmitting unit configured to transmit a message to a base station; a receiving unit configured to receive a message from the base station; and a switching unit configured to: according to the base station Messages, switching based on network performance and signal strength.

Preferably, network performance is in the form of an average service rate of mobile devices in the network And the defined network throughput.

Preferably, the switching unit is configured to: if the current signal strength of the mobile device is still at an acceptable level, then only the network throughput after the possible handover is greater than the current network throughput specific threshold and still provide acceptable The switching is performed at signal strength; if the current signal strength of the mobile device is below an acceptable level, the mobile device is switched to a base station that is capable of providing not only acceptable signal strength but also providing maximum network throughput; If there is no base station capable of providing acceptable signal strength, or switching to a base station capable of providing acceptable signal strength will result in a decrease in network throughput, the mobile device is handed over to the base station with the strongest signal.

The present invention provides an easy-to-implement cell handover scheme by improving the existing cell handover scheme. This solution provides improved user fairness and as much network throughput as possible. Thus, the present invention is able to provide an improved service rate, thereby providing a better user experience, particularly for users at the cell edge. DRAWINGS

The above and other features of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.

1 is a schematic diagram showing a handover of a mobile device between base stations in the prior art; FIG. 2 is a block diagram showing a base station according to an embodiment of the present invention;

Figure 3 shows a block diagram of a mobile device in accordance with one embodiment of the present invention;

FIG. 4 illustrates an example application scenario in accordance with one embodiment of the present invention;

FIG. 5 shows a detailed parameter table in the example application scenario of FIG. 4;

6 shows a cumulative distribution function graph based on the parameter table shown in FIG. 5; FIG. 7 shows a flowchart of a switching method according to an embodiment of the present invention; and FIG. 8 shows another according to the present invention. A flowchart of a handover method of an embodiment. detailed description

The principles and implementation of the present invention will be apparent from the description of the embodiments of the invention. It should be noted that the present invention should not be limited to the specific embodiments described below. In addition, it should be noted that, for the sake of simplicity, A well-known component related to the invention.

2 shows a block diagram of a base station 200 for use in a wireless heterogeneous network, including but not limited to: a macro base station, a micro base station, a home base station, a relay base station, and other types, in accordance with an embodiment of the present invention. Service node, and so on. As shown in FIG. 2, in the present example, the base station 200 includes a transmitting unit 202, a receiving unit 204, and a switching unit 206. Transmitting unit 202 is configured to transmit messages to mobile devices in its service area as well as to neighboring base stations. Receiving unit 204 is configured to receive messages from mobile devices and neighboring base stations. Switching unit 206 is configured to perform handover based on network performance and signal strength based on messages from the mobile device and neighboring base stations. Specifically, in the present invention, the two cases of normal switching and network access are considered, and the following description will be respectively made.

Normal switching includes two types of switching: active switching and passive switching. The meaning of active handover is that switching may occur even if the signal transmitted from the transmitting unit 202 of the base station 200 to the target mobile device is still above an acceptable level. That is, as long as there are potential base stations that can provide greater network throughput, even if the signal strength may be slightly reduced (but still above an acceptable level), the target mobile device will be handed over to the base station. The meaning of passive handover is: If the signal transmitted from the transmitting unit 202 of the current base station 200 to the target mobile device is below an acceptable level (such as below a certain threshold), the handover is performed. The target base station is a base station that not only provides acceptable signal strength, but also provides maximum network throughput. If there is no target base station that meets the conditions, it switches to the neighboring base station with the strongest received signal.

In the real world, multiple parameters need to be known to determine if a reasonable switch needs to be performed. The mobile device continuously monitors the strength of its received signal from the base station (including its signal used by tr) and feeds back the information. The receiving unit 204 of the base station 200 receives the feedback information and passes the information to the switching unit 206, which determines, by the switching unit 206, when to perform the handover and to which cell.

Specifically, the switching unit 206 estimates the potential data rate from each target base station to the mobile device based on the feedback information of the signal strength. For example, the link data rate from each target base station to the mobile device, i.e., the mobile device average service rate, is estimated based on Shannon's formula or MCS (Modulation and Coding Scheme) mapping. Switching unit 206 then calculates the potential network throughput (assuming that the mobile device is handed over to the base station). Based on this, the switching unit 206 compares the throughput before and after the potential handover to decide whether to perform the handover. For example, assume that there are N base stations (including macro base stations, micro base stations, home base stations, and relay base stations, etc.), each of which has an associated mobile device. The switching unit 206 calculates the downlink network throughput under proportional fair scheduling (PFS) according to the following formula:

" ^2,1...

T )'( , +1,2 · ) ' ' ' ^«,+...+«^.,+2,^ ·■·

•"2

(1) where is the average link data rate provided by the nth base station to its attached mobile device numbered u. Estimate based on signal strength feedback. Note that the τ defined in equation (1) can provide a proportional fair service to each user.

Accordingly, assuming that the mobile device numbered k is currently served by the i-th base station, if the handover to the j-th base station, the ratio of the throughput after the handover and before the handover is

Ti—>j ¹ after _h ^l kJ ^M ,; “j

l _r = ~ = r- rn)

Ding'(" +ι ¹

Obviously, 7 ≥ 1 becomes a necessary condition for performing the handover. Thus, the final cell handover criteria can be written as j* = max T'~ ^>J

St"T; ^→J ≥ 1, and R _{k J} ≥ R^ ^oS ( ³⁾

That is, the target base station is a base station that provides not only acceptable signal strength but also maximum network throughput (where ^s is the lowest signal strength that the mobile device numbered k can accept).

The following is a detailed description of the mobile device's access to the network. In fact, the cell handover scheme in the case of network access is very similar to that in the case of normal handover. Assume a new mobile device k Start to enter the jth base station in the network, then the ratio of the throughput after entering the network and before entering the network is

T after- e ^k ,j ' ^U j '

e ore _e ( _Uj + 1)

Similarly, Γ/≥1 becomes a necessary condition for accessing the network. Therefore, the final cell handover criteria can be written as j = max T ^J

j

s,t., Τ;≥ 1, and R _kj ≥ R^ ^oS ( ^{5 )}

That is, the target base station is a base station that not only provides acceptable signal strength, but also provides maximum network throughput.

In summary, in the base station 200 according to an embodiment of the present invention, it is necessary to know in advance the average link rate and the number of mobile devices served by the neighboring base stations. The mobile device only needs to feed back channel measurements (measured by the pilot channel) to its current serving base station, and then the rest of the work is performed in the switching unit 206 of the base station 200. In addition, base station 200 can exchange the number of mobile devices served by each of the neighboring base stations via the X2 interface. By improving the existing cell handover scheme, base station 200 in accordance with one embodiment of the present invention provides better user fairness and as much network throughput as possible.

However, those skilled in the art will appreciate that the above-described handoff can also be performed by the mobile device, particularly when the mobile device has just booted into the network. FIG. 3 shows a block diagram of a mobile device 300 in accordance with one embodiment of the present invention. The mobile device 300 includes a transmitting unit 302, a receiving unit 304, and a switching unit 306. When the mobile device 300 has just turned on to enter the wireless communication network, the receiving unit 304 receives the number information of the mobile devices associated with each of the neighboring base stations from the base station serving the current cell over the air interface. Then, the switching unit 306 is most reasonable based on the information and the quality of the link with each base station detected via the pilot. The target base station sends a network access request, and after obtaining permission, switches to the base station. Switching unit

The process performed by 306 is similar to the operation of switching unit 206 of base station 200 described above and will not be described again herein.

Of course, the mobile device 300 can also first access the base station that can provide the maximum received signal, and then the base station performs a handover operation to access the mobile device 300 to the most suitable base station.

An application scenario according to an embodiment of the present invention is described below with reference to FIGS.

Figure 4 shows an example of the application of the present invention in a 3GPP LTE-A heterogeneous network. Figure 5 shows a detailed parameter table for the example application of Figure 4. As can be seen from Figure 5, the cellular layout of the example application scenario includes seven macro base stations, each of which governs three cells. However, for the sake of clarity, only the multi-cell hexagonal layout including one macro base station (eNB in FIG. 4) is schematically illustrated in FIG. 4, and the macro base station governs three cells, each of which has Two micro base stations (pico in Figure 4). Those skilled in the art will appreciate that the other six macro base stations have similar layouts.

Fig. 6 shows a function graph based on the parameter table shown in Fig. 5, which is a technical solution (solid line) of the present invention and a SINR-based technical scheme (dashed line) in the prior art. A cumulative distribution function curve for the corresponding normalized user throughput. A point on the cumulative distribution function curve indicates that a user in the system having a percentage corresponding to (1 - the ordinate of the point) can achieve a normalized data rate as indicated by the abscissa of the point. Correspondingly, the more the curve is to the right, the better the performance of the corresponding scheme. The following table lists the 5% (cell edge), 50% (median) and mean (cell average) user throughputs in Figure 4:

Table 1 - Normalized User Throughput As can be seen from Table 1, the present invention is at 5% and 50% throughput compared to prior art solutions. The amount has increased by 23.3% and 21.3% respectively, which means that most users (especially users at the edge of the community) can significantly feel the improvement of service quality. In other words, user fairness is better ensured. Further, it is noted that the average user throughput of the cell of the present invention has a decrease of 7.9% because in the SINR-based cell handover scheme, fewer users obtain very high throughput.

FIG. 7 shows a flow chart of a handover method 700 in accordance with one embodiment of the present invention. The method can be performed, for example, by the base station 200 shown in Fig. 2 in accordance with one embodiment of the present invention. Specifically, method 700 begins at step 702. Next, at step 704, the mobile device continuously monitors the strength of the signal it receives from the base station, including the signal it is currently using, and feeds back the information to the current serving base station. Thereafter, at step 706, the serving base station obtains information about other mobile devices in the network from neighboring base stations. At step 708, the base station performs cell handover for the mobile device based on network performance and signal strength based on messages from the mobile device and neighboring base stations, as described above.

It should be noted that the order of execution of the method shown in Fig. 7 is merely illustrative, and the switching method of the present invention is not necessarily limited to the order shown in Fig. 7. For example, the order of execution of steps 704 and 706 can be reversed.

FIG. 8 shows a flow chart of a switching method 800 in accordance with another embodiment of the present invention. The method can be performed, for example, by the mobile device 300 according to one embodiment of the present invention shown in Figure 3 when it is connected to the network. Specifically, method 800 begins at step 802. At step 804, the mobile device just entering the network receives information on the number of mobile devices in the network from the base station. Thereafter, in step 806, the mobile device measures the quality of the channel between it and the base station. Then, at step 808, the mobile device performs handover based on network performance and signal strength based on information received from the base station to determine which base station it should access, as described above.

The present invention proposes a base station and mobile device with enhanced handover decisions and a corresponding method, wherein the switched target base station not only provides acceptable signal strength, but also provides maximum network throughput. That is, if the signal of the current base station is still at an acceptable level, the active handover is performed only when the total network throughput after the possible handover is greater than the network throughput before the handover (eg, greater than a certain difference). If the signal of the current base station is below an acceptable level, passive handoff is performed and the target base station not only provides acceptable signal strength, but also provides maximum network throughput. The present invention can provide better user fairness and as much network throughput as possible. Thus, the present invention is able to provide a better user experience, especially for users at the edge of the cell.

While the invention has been described in terms of the preferred embodiments of the present invention, it will be understood by those skilled in the art that the invention may be variously modified, substituted, and changed without departing from the spirit and scope of the invention. Therefore, the invention should be construed as limited by the appended claims and the appended claims.

Claims

Rights request

A base station in a wireless communication network, comprising:

a transmitting unit configured to transmit a message to a mobile device and a neighboring base station;

a receiving unit configured to receive a message from the mobile device and the neighboring base station; and a switching unit configured to: perform handover based on network performance and signal strength based on messages from the mobile device and the neighboring base station.

2. The base station of claim 1, wherein the network performance comprises: network throughput defined in the form of a mobile device average service rate in the network.

3. The base station according to claim 2, wherein the switching unit is configured to: if the current signal strength of the mobile device is still at an acceptable level, only the network throughput after the possible handover is greater than the current network The t-switching is performed when the throughput is at a certain threshold and still provides acceptable signal strength.

4. The base station according to claim 2, wherein the switching unit is configured to: if the current signal strength of the mobile device is below an acceptable level, switch the mobile device to not only provide acceptable signal strength And a base station capable of providing maximum network throughput.

5. The base station according to claim 4, wherein the switching unit is configured to: if there is no base station capable of providing acceptable signal strength, or switch to a base station capable of providing acceptable signal strength, causing network throughput When the amount drops, the mobile device is switched to the base station with the strongest signal.

6. The base station according to claim 2, wherein the switching unit is configured to: estimate a mobile device average service rate based on a Shannon theory or a modulation and coding scheme mapping, thereby obtaining network throughput.

7. The base station according to claim 1, wherein a transmitting unit and a receiving unit of the base station exchange information of an associated mobile device with a neighboring base station via an X2 interface, and a transmitting unit of the base station transmits the information via an air interface. Information is passed to the newly connected mobile device.

The base station according to any one of claims 1 to 7, wherein the wireless communication network is an LTE heterogeneous network, and the base station comprises a macro base station, a micro base station, a home base station, and a relay base station.

9. A handover method performed by a base station in a wireless communication network, comprising, for example:

Receiving messages from mobile devices and neighboring base stations;

Switching is performed based on network performance and signal strength based on messages from mobile devices and base stations.

10. The handover method of claim 9, wherein the network performance comprises: network throughput defined in the form of a mobile device average service rate in the network.

11. The handover method of claim 10, wherein if the current signal strength of the mobile device is still at an acceptable level, then only the network throughput after the possible handover is greater than the current network throughput specific threshold, and still This switching is performed when an acceptable signal strength is provided.

12. The handover method of claim 10, wherein if the current signal strength of the mobile device is below an acceptable level, switching the mobile device to not only provide acceptable signal strength, but also provide a maximum network Base station for throughput.

13. The handover method according to claim 12, wherein if there is no base station capable of providing acceptable signal strength, or switching to a base station capable of providing acceptable signal strength causes a decrease in network throughput, the mobile device is Switch to the base station with the strongest signal.

The handover method according to claim 10, wherein the mobile device average service rate is estimated based on Shannon's theory or modulation and coding scheme mapping, thereby obtaining network throughput.

15. A mobile device, comprising:

a transmitting unit configured to transmit a message to a base station;

a receiving unit configured to receive a message from a base station;

The switching unit is configured to: perform handover based on network performance and signal strength based on a message from the base station.

16. The mobile device of claim 15, wherein the network performance comprises: network throughput defined in the form of a mobile device average service rate in the network.

17. The mobile device of claim 16, wherein the switching unit is configured to: if the current signal strength of the mobile device is still at an acceptable level, then only the network throughput after the possible handover is greater than the current Network throughput specific threshold and still This switching is performed when an acceptable signal strength is provided.

18. The mobile device of claim 16, wherein the switching unit is configured to switch the mobile device to not only provide an acceptable signal if the current signal strength of the mobile device is below an acceptable level A base station that is strong and capable of providing maximum network throughput.

19. The mobile device of claim 18, wherein the switching unit is configured to cause a network if there is no base station capable of providing acceptable signal strength, or switching to a base station capable of providing acceptable signal strength As the throughput decreases, the mobile device is switched to the base station with the strongest signal. ·