AU2010201714A1 - Method and device for implementing ultra far coverage - Google Patents

Description

AUSTRALIA Patents Act COMPLETE SPECIFICATION (ORIGINAL) Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Huawei Technologies Co., Ltd. Actual Inventor(s): Weidong Kong, Dagang Zhang Address for Service and Correspondence: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: METHOD AND DEVICE FOR IMPLEMENTING ULTRA FAR COVERAGE Our Ref: 886227 POF Code: 462917/469582 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): - 1 8000q METHOD AND DEVICE FOR IMPLEMENTING ULTRA FAR COVERAGE This application claims priority from Chinese Application No.200910135929.4 filed on 30 April 2009, the contents of which are to be taken as incorporated herein by this reference. 5 FIELD OF THE TECHNOLOGY 100011 The present invention relates to communication technology, and more particularly to a method and a device for implementing ultra far coverage. BACKGROUND OF THE INVENTION 100021 The Worldwide Interoperability for Microwave Access (WiMAX) features wide 10 coverage and high-rate radio access, and supports non-line-of-sight propagation. 100031 WiMAX system is often limited by many conditions, for example, limited by a transmit/receive transition gap (TTG), so the coverage distance of the WiMAX system is limited to a certain range. According to the formula BSTTG > 2r + SSRTG , the maximum distance of the coverage of the WiMAX system is 8.357145 km, in which 15 BSTTG indicates a base station transmit/receive transition gap, and SSRTG indicates a subscriber station receive/transmit transition gap. 100041 However, under some special situations, for example, the ultra far coverage over 20 km is not supported currently. The reason is as follows: In the case of ultra far coverage, round trip delays (RTDs) of remote subscribers differ significantly, and after adjustment, the 20 sending time of an uplink signal may be advanced greatly, so that the time for a mobile station (MS) to send the uplink signal is reached before the MS demodulates signals in the last one or more downlink symbols. That is, influenced by the RTD, the longer the distance between the MS and a BS is, the earlier the time for the MS to adjust the sending time of the uplink signal will be. With the increase of the RTD, the time of the uplink 2 signal of the MS must be adjusted more greatly. When the RTD reaches or exceeds the TTG, the last part of the downlink signal cannot be correctly received by the MS. [00051 Therefore, during the research and practice of the prior art, the inventor of the present invention finds that the prior art at least has the following problem: when the ultra 5 far coverage is implemented, with the increase of the RTD, the downlink signal cannot be correctly received by the MS; that is, the coverage distance is short in the prior art, so a user is limited to some extent when using the system. SUMMARY OF THE INVENTION 100061 The present invention is directed to a method and a device for allocating downlink 10 resources, which solve the problem of correctly receiving downlink signals with the increase of the RTD in the ultra far coverage, so as to improve user satisfaction. 100071 To solve the above technical problem, an embodiment of the present invention provides a method for allocating downlink signals. The method includes: determining a coverage range of a BS; 15 determining downlink resources to be reserved according to the coverage range; and allocating downlink resources of the BS except for the reserved downlink resources to subscribers including ultra far subscribers. 100081 Correspondingly, in an embodiment, the present invention provides a device for allocating downlink resources. The device includes: 20 a determining unit, configured to determine the coverage range of a BS; a calculating unit, configured to calculate downlink resources to be reserved according to the coverage range determined by the determining unit; and an allocating unit, configured to allocate downlink resources in the BS except for 3 the reserved downlink resources calculated by the calculating unit to subscribers including ultra far subscribers. 100091 It is known from the above technical solutions that in the embodiments of the present invention, the downlink resources to be reserved are determined according to the 5 coverage range of the BS, and the reserved downlink resources are allocated to non-ultra far subscribers. That is, according to the maximum RTD of ultra far subscribers, corresponding downlink resources are reserved for the subscribers, and the reserved downlink resources are used to preferentially fill data of the non-ultra far subscribers, so as to ensure that the ultra far subscribers have completed demodulation of all downlink signals 10 before sending an uplink signal. Thus, the present invention solves the problem of correctly receiving downlink signals by the ultra far subscribers with the increase of the RTD in the ultra far coverage, so as to increase the utilization of the reserved resources, and to improve user satisfaction. BRIEF DESCRIPTION OF THE DRAWINGS 15 100101 FIG. I is a flow chart of a method for allocating downlink resources according to Embodiment 1 of the present invention; 100111 FIG. 2 is a flow chart of a method for allocating downlink resources according to Embodiment 2 of the present invention; 100121 FIG 3 is a flow chart of a method for allocating downlink resources according to 20 Embodiment 3 of the present invention; [00131 FIG. 4 is a flow chart of a method for allocating downlink resources according to Embodiment 4 of the present invention; 100141 FIG. 5 is a schematic structural view of a first device for allocating downlink resources according to an embodiment of the present invention; 25 100151 FIG. 6 is a schematic structural view of a second device for allocating downlink 4 resources according to an embodiment of the present invention; 100161 FIG. 7 is a schematic structural view of a third device for allocating downlink resources according to an embodiment of the present invention; 100171 FIG 8 is a schematic structural view of a fourth device for allocating downlink 5 resources according to an embodiment of the present invention; [00181 FIG 9 is a schematic structural view of a fifth device for allocating downlink resources according to an embodiment of the present invention; and 100191 FIG 10 is a schematic structural view of a sixth device for allocating downlink resources according to an embodiment of the present invention. 10 DETAILED DESCRIPTION OF THE EMBODIMENTS 100201 The embodiments of the present invention provide solutions of reserving downlink resources for ultra far coverage in the WiMAX. Because of the ultra far coverage, the RTD of a remote subscriber is great. If the sending time of an adjusted uplink signal is earlier than the time specified by the TTQ the time for the subscriber to send the uplink 15 signal may be reached before signals in the last symbol of a downlink frame of the remote subscriber sent by a BS are correctly demodulated. Here, the TTG is the reserved protection time for transmit/receive transition. Therefore, in the embodiments of the present invention, according to the maximum RTD of remote subscribers (for example, ultra far subscribers), corresponding downlink resources are reserved for the subscribers, 20 and the reserved downlink resources are used for sending downlink signals of non-ultra far subscribers, so as to ensure that the ultra far subscribers have completed demodulation of all downlink signals before sending the uplink signal. For example, the ultra far subscribers do not use the reserved downlink resources to send information, and the non-ultra far subscribers can use the reserved resources to send information. Thus, the 25 present invention solves the problem of incorrectly receiving downlink signals by the ultra far subscribers with the increase of the RTD in the ultra far coverage, so as to increase the 5 utilization of the reserved resources, and to improve user satisfaction. 100211 Next, embodiments of the present invention are described in detail with reference to the accompanying drawings. 100221 FIG 1 is a flow chart of a method for allocating downlink resources according to 5 Embodiment I of the present invention. As shown in FIG 1, the method includes the following steps. 100231 Step 101: Determine a coverage range of a BS. 100241 In this embodiment, the coverage range of the BS may be determined according to network planning. For example, to persons skilled in the art, it is understood that the 10 maximum distance of the coverage of the BS is normally 8.357 km. In order to increase the coverage distance of the BS, resources of downlink frames need to be reserved. For the resource structure of a two-dimensional frame, the minimum unit of one frame is a symbol. [00251 Step 102: Determine downlink resources to be reserved according to the coverage 15 range. 100261 In this step, the reserved resources are the last one or more symbols of the downlink frame. If the one or more symbols are used for sending downlink signals of an ultra far subscriber, the ultra far subscriber may be incapable of performing correct demodulation. The downlink resources may be reserved in the following mode. On the basis of the 20 current coverage range of the BS, the reservation is started from the last symbol in the downlink frame when every fixed distance is added to the coverage range. For example, when every 15 km is added to the coverage range of the BS, the ultra far MS will be incapable of demodulating one symbol. Therefore, in the downlink resource reservation, one symbol is reserved from the last symbol in the downlink frame. The above 25 description is only exemplary, and the present invention is not thus limited. 6 100271 Step 103: Allocate downlink resources in the BS except for the reserved downlink resources to subscribers including ultra far subscribers. 100281 In this embodiment, the WiMAX system is taken for example, and the resource utilization and allocation is uniformly controlled by the BS. For example, when the RTD 5 is small, that is, the coverage of the BS is not very far, few resources need to be reserved. At this time, simple processing can be performed, for example, reserving the resources directly. As the BS can uniformly control the utilization of resources, when the BS schedules or sends the downlink signal, the reserved resources may not be used. 100291 The subscribers comprises the ultra far subscribers and non-ultra far subscribers 10 which are classified according to the round trip delay (RTD) differences between ultra far subscribers and non-ultra far subscribers. Therefore, the method may further include detecting RTD differences between subscribers, and classifying the subscribers into the ultra far subscribers and non-ultra far subscribers according to the RTD differences. 100301 The method of the embodiment may further include allocating all of the reserved 15 downlink resources to the non-ultra far subscribers. 100311 FIG. 2 is a flow chart of a method for allocating downlink resources according to Embodiment 2 of the present invention. As shown in FIG. 2, in this embodiment, when the BS system has only one zone, the reserved resources can be used. Firstly, RTDs of subscribers are detected, so as to categorize the subscribers. For example, the subscribers 20 are categorized into ultra far subscribers and non-ultra far subscribers. Then, downlink resources to be reserved are determined according to the coverage range of the BS. Thus, a zone formed by the downlink resources in the BS is divided into two downlink resource zones, namely, a reserved downlink resource zone and a non-reserved downlink resource zone. The reserved downlink resource zone is configured to be scheduled to the non-ultra 25 far subscribers only, and the non-reserved downlink resource zone can schedule all the subscribers. In this embodiment, the reserved downlink resources may be the last one or more symbols of the downlink frame, or other symbols, which is not limited in this 7 embodiment, as long as the downlink signals of the ultra far subscribers sent by using the symbols except for the reserved symbols can be correctly demodulated by the ultra far subscribers. The implementation process is as follows. 100321 Step 201: Determine a coverage range of a BS according to network planning. 5 100331 Step 202: Determine downlink resources to be reserved according to the coverage range. 100341 Step 203: Record a region formed by the downlink resources. 100351 Step 204: Allocate the downlink resources in the formed region to a part of or all of non-ultra far subscribers. 10 100361 Step 205: Allocate downlink resources in the BS except for the downlink resources in the region are allocated to other subscribers including ultra far subscribers. 100371 That is, in this step, data of a part of or all of the non-ultra far subscribers is filled in the downlink resource region in the formed region, and data of all other subscribers is filled in the remaining downlink resource region. Here, the other subscribers may be the 15 remaining non-ultra far subscribers or ultra far subscribers, which are not limited in the embodiment of the present invention. 100381 In Embodiment 2, all subscribers are associated with one zone, so the operation may become messy. Therefore, in Embodiment 3 of the present invention, requirements for scheduling and filling the downlink resources of Embodiment 2 are raised. FIG 3 is a 20 flow chart of a method for allocating downlink resources according to Embodiment 3 of the present invention. As shown in FlG 3, in this embodiment, the reserved resources are used as a new zone, and the new zone is defined as a non-ultra far zone. Then, according to the resource amount in the new zone and the load of the entire carrier sector, a part of non-ultra far subscribers associated with other zones are switched to the new zone, and the 25 resources of the zone are used to perform data transmission. Thus, downlink data of the 8 ultra far subscribers can be sent in the resources that are not reserved. The method includes the following steps. 100391 Step 301: Determine a coverage range of a BS according to network planning. [00401 Step 302: Determine downlink resources to be reserved according to the coverage 5 range. 100411 In step 303, use the reserved resources as downlink resources of a new zone of the BS, and the new zone is defined as a non-ultra far subscriber zone. 100421 In this step, the new zone may be directly defined as a non-ultra far subscriber zone. 100431 Step 304: Notify information about the new zone to user equipments (UEs) through 10 broadcast signaling. 100441 Step 305: Allocate the downlink resources of the new zone to a part of or all of non-ultra far subscribers. 100451 Step 306: Allocate the remaining downlink resources in the BS to other subscribers including the non-ultra far subscribers. 15 100461 In another embodiment, when the BS system has multiple zones, the processing of the reserved resources is similar to the description in Embodiment 3, that is, a new zone is created for the reserved downlink resources. However, the difference between said another embodiment and Embodiment 3 lies in that: the type of the zone may be selected as follows in said another embodiment. 20 100471 Loads of the zones in the BS system are scanned. The zone with the highest load, the zone with the highest non-ultra far subscriber load, or the zone with the highest load and having the most non-ultra far subscribers may be selected. The type of the selected zone is used as the type of the new zone. According to the load of the new zone, a part of the non-ultra far subscribers associated with the selected zone are switched to the new zone. 9 However, as the conditions of the highest zone load and the most non-ultra far subscribers may not be satisfied at the same time, an appropriate zone type may be selected as the type of the zone created for the reserved resources according to the two conditions, and a part of the non-ultra far subscribers are selected and switched to the zone, so as to use the resources 5 of the zone to perform data transmission. The detailed implementation is similar to the description in Embodiment 3, while the difference is that the solution according to said another embodiment is applicable to multiple zones. Other details of the implementation are as shown in FIG 3, and will not be described herein. 100481 FIG 4 is a flow chart of a method for allocating downlink resources according to 10 Embodiment 4 of the present invention. As shown in FIG. 4, when the BS system has multiple zones, the reserved downlink resources and the downlink resources of the last zone form a new zone, that is, it is unnecessary to create a new zone, which is simple and has low overhead. The specific resource allocation is similar to the processing on a single zone in Embodiment 2. The method includes the following steps. 15 100491 Step 401: Determine a coverage range of a BS according to network planning. 100501 Step 402: Determine downlink resources to be reserved according to the coverage range. 100511 Step 403: Form downlink resources of a new zone with the reserved downlink resources and downlink resources in a last zone of the BS. 20 100521 Step 404: Allocate the downlink resources of the formed new zone to a part of or all of non-ultra far subscribers. 100531 Step 405: The remaining downlink resources in the BS are allocated to other subscribers including ultra far subscribers. 100541 In this step, the remaining downlink resources are other downlink resources except 25 for the downlink resources of the new zone. 10 100551 The above embodiments describe the procedure for processing reserved downlink resources for ultra far coverage in the WiMAX system. Because of the ultra far coverage, the RTD of a remote subscriber is great. If the sending time of an uplink signal after adjustment is earlier than the time specified by the TTQ signals in the last downlink symbol 5 are not correctly demodulated. Therefore, in the embodiments of the present invention, according to the maximum RTD of ultra far subscribers, corresponding downlink resources are reserved for the subscribers. Thus, the last one or more symbols of the downlink frame are reserved, and the reserved symbols are preferentially allocated to the non-ultra far subscribers, that is, the data of the non-ultra far subscribers is filled in the reserved symbols, 10 and other downlink resources except for the reserved downlink resources are used for sending downlink signals of ultra far subscribers, so as to ensure that all downlink signals are demodulated before the ultra far subscribers send uplink signals. Thus, user satisfaction is improved. 100561 Based on the implementation processes of the method described above, the present 15 invention further provides a device for allocating downlink resources. FIG 5 is a schematic structural view of the device. As shown in FIG 5, the device includes a determining unit 51, a calculating unit 52, and an allocating unit 53. The determining unit 51 is configured to determine a coverage range of a BS. The calculating unit 52 is configured to determine downlink resources to be reserved according to the coverage range 20 determined by the determining unit 51. The allocating unit 53 is configured to allocate downlink resources in the BS except for the reserved downlink resources to subscribers including ultra far subscribers. The allocating unit 53 can be further configured to allocate all of the reserved downlink resources to non-ultra far subscribers. 100571 The device may further include a detecting unit 54 and a determining unit 55. The 25 detecting unit 54 is configured to detect RTD differences between subscribers. The determining unit 55 is configured to classify the subscribers into non-ultra far subscribers and ultra far subscribers according to the RTD differences detected by the detecting unit 54. The structure of the device is as shown in FIG 6. 11 100581 Optionally, on the basis of FIG 5 or 6, the device may further include a recording unit 56 configured to record a region formed by the reserved downlink resources. The allocating unit 53 is further configured to allocate the downlink resources in the formed region recorded by the recording unit 56 to the non-ultra far subscribers. The detailed 5 structure is as shown in FIG 7, which is a schematic view on the basis of FIG. 6. 100591 Optionally, on the basis of FIG 5 or 6, the device may further include a defining unit configured to use the reserved downlink resources as downlink resources of a new zone in the BS, and use the new zone as a non-ultra far subscriber zone. The allocating unit 53 is further configured to allocate the downlink resources of the new zone defined by the 10 defining unit to the non-ultra far subscribers. 100601 The defining unit may include a first defining unit 57 configured to directly define the new zone formed by the reserved downlink resources as a non-ultra far subscriber zone. The detailed structure is as shown in FIG. 8, which is a schematic view on the basis of FIG 6. 15 100611 The defining unit may include a scanning unit 58, a selecting unit 59, a second defining unit 60, and a switching unit 61. The scanning unit 58 is configured to scan loads of zones in the BS. The selecting unit 59 is configured to select the zone with the highest load, the zone with the highest non-ultra far subscriber load, or the zone with the highest load and having the most non-ultra far subscribers according to the loads of the zones 20 scanned by the scanning unit 58. The second defining unit 60 is configured to define a type of a new zone formed by the downlink reserved resources according to a type of the zone selected by the selecting unit 59. The switching unit 61 is configured to switch a part of non-ultra far subscribers associated with the selected zone selected by the selecting unit 59 to the new zone according to the load of the new zone. The detailed structure is as 25 shown in FIG 9, which is a schematic view on the basis of FIG 6. 100621 The device may further include a notifying unit configured to notify information of the new zone to UEs through broadcast signaling. 12 100631 Optionally, on the basis of FIG 5 or 6, the device may further include a forming unit 62, configured to form downlink resources of a new zone with the reserved downlink resources and downlink resources of a last zone in the BS. The allocating unit 53 is further configured to allocate the downlink resources of the new zone formed by the 5 forming unit 62 to non-ultra far subscribers. The detailed structure is as shown in FIG 10, which is a schematic view on the basis of FIG 6. 100641 The device may further include a notifying unit configured to notify information of the new zone to UEs through broadcast signaling. 100651 It is known from the above embodiments that in the embodiments of the present 10 invention, the downlink resources to be reserved are determined according to the coverage range of the BS, and the reserved downlink resources are allocated to a part of or all of the non-ultra far subscribers. That is, corresponding downlink resources are reserved according to the maximum RTD of the ultra far subscribers, and the reserved downlink resources are used to preferentially fill data of the non-ultra far subscribers, while downlink 15 data of the ultra far subscribers may be sent by using downlink resources except for the reserved downlink resources, so as to ensure that the ultra far subscribers have completed demodulation of all downlink signals before sending an uplink signal. Thus, the present invention solves the problem of correctly receiving downlink signals by the ultra far subscribers with the increase of the RTD in the ultra far coverage, so as to increase the 20 utilization of the reserved resources, and to improve user satisfaction. 100661 Through the descriptions of the preceding embodiments, those skilled in the art may understand that the present invention may be implemented by hardware only or by software and a necessary universal hardware platform. However, in most cases, using software and a necessary universal hardware platform are preferred. Based on such understandings, all 25 or part of the technical solution under the present invention that makes contributions to the prior art may be essentially embodied in the form of a software product. The software product may be stored in a storage medium, which can be a Read-Only Memory (ROM), a 13 Random Access Memory (RAM), a magnetic disk, or a Compact Disk Read-Only Memory (CD-ROM). The software product includes a number of instructions that enable a computer device (personal computer, server, or network device) to execute the methods provided in the embodiments of the present invention. 5 100671 It should be noted that the above descriptions are merely some exemplary embodiments of the present invention, and person having ordinary skill in the art may make various improvements and refinements without departing from the spirit of the invention. All such modifications and refinements are intended to be covered by the present invention. 14

Claims (16)

1. A method for allocating downlink resources, comprising: determining a coverage range of a base station (BS); 5 determining downlink resources to be reserved according to the coverage range; and allocating downlink resources of the BS except for the reserved downlink resources to subscribers including ultra far subscribers.

2. The method according to claim 1, wherein the subscribers comprises the ultra far subscribers and non-ultra far subscribers which are classified according to the round trip 10 delay (RTD) differences between ultra far subscribers and non-ultra far subscribers.

3. The method according to claim 2, further comprising: recording a region formed by the reserved downlink resources; and allocating the downlink resources in the region to the non-ultra far subscribers.

4. The method according to claim 2, further comprising: 15 using the reserved resources as downlink resources of a new zone of the BS, and defining the new zone as a non-ultra far subscriber zone; and allocating the downlink resources of the new zone to the non-ultra far subscribers.

5. The method according to claim 2, further comprising: using the reserved resources as downlink resources of a new zone of the BS; 20 scanning loads of zones in the BS system, and selecting the zone with the highest load, 15 the zone with the highest non-ultra far subscriber load, or the zone with the highest load and having the most non-ultra far subscribers; and switching a part of the non-ultra far subscribers associated with the selected zone to the new zone according to the load of the new zone. 5

6. The method according to claim 5, wherein after selecting the zone with the highest load, the zone with the highest non-ultra far subscriber load, or the zone with the highest load and having the most non-ultra far subscribers, the method further comprises: using a type of the selected zone as a type of the new zone.

7. The method according to claim 1, further comprising: 10 forming downlink resources of a new zone with the reserved downlink resources and downlink resources in a last zone of the BS; and allocating the downlink resources of the formed new zone to the non-ultra far subscribers.

8. The method according to claim 2, further comprising: 15 allocating the reserved downlink resources to the non-ultra far subscribers.

9. The method according to any one of claims I to 6, wherein the determining the downlink resources to be reserved according to the coverage range comprises: determining one symbol to be reserved from a last symbol of a downlink frame when every fixed distance added to the coverage range of the current BS. 20

10. A device for allocating downlink resources, comprising: a determining unit, configured to determine a coverage range of a base station (BS); a calculating unit, configured to determine downlink resources to be reserved 16 according to the coverage range determined by the determining unit; and an allocating unit, configured to allocate downlink resources in the BS except for the reserved downlink resources to subscribers including ultra far subscribers.

11. The device according to claim 10, wherein the allocating unit is further configured 5 to allocate the reserved downlink resources to non-ultra far subscribers.

12. The device according to claim 10, further comprising: a detecting unit, configured to detect round trip delay (RTD) differences between the subscribers; and a determining unit, configured to classify the subscribers into the ultra far subscribers 10 and non-ultra far subscribers according to the RTD differences detected by the detecting unit.

13. The device according to claim 11, wherein: the device further comprises a recording unit, configured to record a region formed by the reserved downlink resources; and 15 the allocating unit is further configured to allocate the downlink resources in the region recorded by the recording unit to the non-ultra far subscribers.

14. The device according to claim 10, wherein: the device further comprises a first defining unit, configured to directly define a new zone formed by the reserved downlink resources as a non-ultra far subscriber zone; and 20 the allocating unit is further configured to allocate the downlink resources in the new zone to the non-ultra far subscribers.

15. The device according to claim 10, further comprising: 17 a scanning unit, configured to scan loads of zones in the BS; a selecting unit, configured to select the zone with the highest load, the zone with the highest non-ultra far subscriber load, or the zone with the highest load and having the most non-ultra far subscribers according to the loads of the zones scanned by the scanning unit; 5 a second defining unit, configured to define a type of a new zone formed by the downlink reserved resources according to a type of the zone selected by the selecting unit; and a switching unit, configured to switch a part of the non-ultra far subscribers associated with the selected zone selected by the selecting unit to the new zone according to the load 10 of the new zone.

16. The device according to claim 10, wherein: the device further comprises a forming unit, configured to form downlink resources of a new zone with the reserved downlink resources and downlink resources in a last zone of the BS; and 15 the allocating unit is further configured to allocate the downlink resources in the new zone formed by the forming unit to the non-ultra far subscribers. 18