Wireless Communication Systems

Abstract

A wireless communication method in a wireless communication system is provided. In the wireless communication system, subscriber stations are each operable to communicate with a base station and the base station is capable of performing simultaneous communications with a number of subscriber stations by allocating an available capacity among the subscriber stations. The subscriber stations are required to issue capacity requests in order to obtain and/or maintain a connection with the base station, and communications between the subscriber stations and the base station are performed partly or wholly through at least one relay station. The provided wireless communication method includes, in the relay station, detecting capacity requests issued from a plurality of the subscriber stations, using the detected requests to form at least one combined capacity request, and transmitting the combined capacity request to the base station. Furthermore, the method includes, in the base station, responding to the combined capacity request by reserving capacity for said plurality of subscriber stations. In addition, the method includes, in the relay station or in the base station, allocating the reserved capacity among the plurality of subscriber stations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows protocol layering in accordance with IEEE 802.16;

FIG. 2 shows the relationship between CID, SFID and QoS in an IEEE 802.16 network;

FIG. 3 shows a packet format capable of being used in an IEEE 802.16 network;

FIG. 4 shows a generic MAC header of a packet as set forth in the IEEE 802.16 specification;

FIG. 5 illustrates a simple bandwidth request protocol in a multi-hop wireless communication system;

FIG. 6 illustrates the bandwidth request (BR) protocol employed in particular embodiments of the present invention;

FIG. 7 is a flowchart of processing of initial bandwidth requests in a relay station (RS);

FIG. 8 is a flowchart of processing of further bandwidth requests in the RS;

FIG. 9 shows a first message format of a combined instant BR in accordance with particular embodiments of the present invention; and

FIG. 10 shows a second message format of a combined instant BR in accordance with particular embodiments of the present invention.

DETAILED DESCRIPTION

An embodiment of the present invention will now be described with reference to FIGS. 6-10, using an IEEE 802.16 network as an example. An algorithm is proposed by which the relay station can classify and combine the bandwidth requests from the subscriber stations (or any other relay station) within its cell, and submit the combined bandwidth requests to the base station, thus decreasing the overhead and collision of bandwidth request messages. This is schematically shown in FIG. 6, in which the subscriber stations are mobile stations denoted by MS. The thick arrow in FIG. 6 represents a combined BR formed in the RS and replacing the multiple parallel BRs relayed by the RS in FIG. 5. As already mentioned, bandwidth requests (BRs) fall into two categories, initial BRs and further BRs, and these are treated differently in the present embodiment.

1. Initial Bandwidth Request

In the network entry and initialization stage, each SS within range of an RS will use contention-based CDMA ranging for requesting initial bandwidth. When the RS detects these CDMA codes, it can send a different CDMA code to the BS to request bandwidth for these SSs, rather than simply relaying two detected CDMA codes to BS, thus saving bandwidth and decreasing the collision probability of the CDMA code transmission surround BS. Alternatively, the RS can use a stand-alone bandwidth request MAC header to request bandwidth for these SSs. This procedure is shown in the flowchart of FIG. 7.

2. Further Bandwidth Request

As explained above, once the SS gets some initial bandwidth, it may subsequently use a stand-alone bandwidth request MAC (Media Access Control) header or Piggyback request to further request bandwidth. In this stage, the RS classifies the received standalone or Piggyback BRs into “Instant BR” (IBR), and “Non-instant BR” (NIBR). The IBRs will be combined and sent to BS by RS as soon as possible. The NIBRs will be combined and sent by periodical aggregate BR by RS. The procedure in the relay station for processing such further BRs is shown in FIG. 8. The first stage is for the RS to receive BRs. Then RS shall identify the QoS parameters relating to the service flow of the corresponding bandwidth request. For example, an RS can index the connection ID (CID) enclosed within the BRs to find the QoS demands. To allow RS to learn the QoS demands of service flows, during the service connection request period, BS has to tell the RS the information of the approved service flows. Alternatively, an RS can “listen in” to the information exchanged during the service connection request period to obtain the QoS associated with the CID, and the relationship between service flow and CID.

In light of QoS demands, the received BRs will be classified into two categories, IBR, and NIBR, by RS. For example, the BRs relevant to Unsolicited Grant Service (UGC), and Real-time Polling Service (rtPS) may be identified as IBR. The BRs for Best Effort (BE), and Non-real-time Polling Service (nrtPS) may be classified as NIBR.

If the number of received IBRs is one, then RS records the amount of the bandwidth requested by this IBR, and simply sends this IBR to BS as soon as possible. This IBR can be incremental or aggregate. The RS will keep the original CID for this IBR. If the number of received IBRs in the current frame is more than one, then RS will combine these IBRs to one BR, called combined IBR, and send this combined BR to BS as soon as possible. In this case, the RS will also record the aggregation of the requested bandwidth of all IBRs. This combined BR can be incremental or aggregate.

A first possible message format of a combined IBR is shown in FIG. 9 (Format A). The details of this control message format are listed in Table 1 below.

TABLE 1
Bandwidth request control message format A of a combined IBR
Name                             Description
Head                             Type of the message, etc.
Amount of the Nth IBR            The number of units, such as bytes, of
                                 uplink bandwidth requested by the Nth
                                 IBR
Other information of the Nth IBR It is optional. It could be the relevant
                                 transmission power, and CINR etc.
Connection ID of the Nth IBR     Connection ID
Check sequence                   To check the received message, such as
                                 CRC sequence

To decrease the size of the control message of a combined IBR, the RS can use the message format shown in FIG. 10 (Format B). The details of this control message are listed in Table 2. When using this message format, the RS will use one of its existing (previously configured) CIDs, which is associated with all CIDs used by its SS, or MS, and RS. The BS will know that the bandwidth request enclosed with this CID is used for the SSs and any other RSs connected to the RS.

TABLE 2
Bandwidth request message format B of a combined IBR
Name                       Description
Head                       Type of the message, etc.
The aggregation of all IBR The total number of units, such as
                           bytes, of uplink bandwidth requested by
                           the all IBRs
Other information          It is optional. It could be the relevant
                           transmission power, and CINR etc.
Connection ID              RS can apply an existing connection ID,
                           which is associated with all the CIDs
                           belonging to all radio devices connected
                           with itself.
Check sequence             To check the received message, such as
                           CRC sequence

After processing the IBRs, the RS will record the aggregation of the requested bandwidth by all NIBRs. When the timer for periodical RS bandwidth request is expired, the RS will work out the aggregation of the bandwidth needed for its uplink transmission, and transmit an aggregate bandwidth request to the BS. The RS can use the “message format B” in FIG. 10 for this bandwidth request. Therefore, an existing CID is needed by RS to associate all CIDs connected to itself. The period of the aggregate bandwidth request may be a function of the QoS of the services relating to NIBRs, and of the link quality.

In response to the BR from the RS, the BS performs necessary processing for allocation of bandwidth. In the case of a format A bandwidth request (FIG. 9), the amounts of bandwidth (incremental or aggregate) required by the individual SSs (or other RSs) is contained in the request from the RS. In this case the BS must allocate bandwidth on an individual basis and notify the RS accordingly, the RS then simply noting the amounts so notified. In the case of a format B bandwidth request (FIG. 10), the BS grants the requested amount (if possible; otherwise a lesser amount) and informs the RS accordingly. It is then up to the RS to allocate the granted bandwidth by dividing up the granted amount appropriately among the requesting SSs/RSs, in dependence upon their QoS requirements.

Although the above description concerns the processing in a single RS and BS, other RSs may be present in the network. In this case, in relation to each other RS, the first RS may act like the BS in the above explanation. Each other RS will serve its own set of SSs and combine the BRs received from those SSs in the same manner as explained above for the first RS.

In summary, certain embodiments of the present invention may provide one or more of the following features:

• • Defining a protocol for an RS to process the received bandwidth requests.
  • Minimizing the control message overhead by classifying and combining received bandwidth requests in RS.
  • Decreasing the collision probability for the contention style bandwidth request.
  • The method proposed can be used for other message relaying, thus achieving the above benefits.

Embodiments of the present invention may be implemented in hardware, or as software modules running on one or more processors, or on a combination thereof. That is, those skilled in the art will appreciate that a microprocessor or digital signal processor (DSP) may be used in practice to implement some or all of the functionality of the RS or BS in particular embodiments of the present invention. It is also possible to provide each SS with some or all of the functionality of the RS. Particular embodiments of the invention may also be embodied as one or more device or apparatus programs (e.g. computer programs and computer program products) for carrying out part or all of any of the methods described herein. Such programs embodying the present invention may be stored on computer-readable media, or could, for example, be in the form of one or more signals. Such signals may be data signals downloadable from an Internet website, or provided on a carrier signal, or in any other form.

Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.

Claims

1. A wireless communication method in which subscriber stations are each operable for communication with a base station, the base station being capable of performing simultaneous communications with a number of subscriber stations by allocating an available capacity among the subscriber stations, the subscriber stations being required to issue capacity requests in order to obtain and/or maintain a connection with the base station, and communications between the subscriber stations and the base station being performed partly or wholly through at least one relay station, the method comprising steps of: in the relay station, detecting capacity requests issued from a plurality of the subscriber stations, using the detected requests to form at least one combined capacity request, and transmitting the combined capacity request to the base station;in the base station, responding to the combined capacity request by reserving capacity for said plurality of subscriber stations; andin the relay station or in the base station, allocating the reserved capacity among the plurality of subscriber stations.

2. The method according to claim 1, wherein each subscriber station issues a capacity request as part of a network entry procedure to obtain a connection with the base station.

3. The method according to claim 1, wherein at least some subscriber stations issue a capacity request during communication with the base station to maintain or change an existing connection with the base station.

4. The method according to claim 2, wherein the capacity request is a request for an absolute amount of capacity.

5. The method according to claim 3, wherein the capacity request is a request for an incremental amount of capacity.

6. The method according to claim 1, wherein each capacity request is a bandwidth request for allocation of bandwidth from the base station.

7. The method according to claim 6, wherein the bandwidth request is an initial bandwidth request in the form of a CDMA ranging code.

8. The method according to claim 7, wherein the relay station transmits the combined bandwidth request in the form of a CDMA code.

9. The method according to claim 6, wherein the bandwidth request is a further bandwidth request in the form of a stand alone media access control header.

10. The method according to claim 6, wherein the relay station transmits the combined bandwidth request in the form of a stand alone media access control header.

11. The method according to claim 1, wherein communication is performed through exchange of packets and the relay station transmits the combined capacity request in a medium access control layer header of such a packet.

12. The method according to claim 1, wherein the combined capacity request includes details of individual capacity requests detected in said detecting step.

13. The method according to claim 12, wherein each connection between a subscriber stations and the base station has a connection ID, and said details include connection IDs corresponding to the detected capacity requests.

14. The method according to claim 1, wherein the combined capacity request aggregates the amounts of capacity contained in the detected capacity requests without including details of the individual capacity requests.

15. The method according to claim 14, wherein the connection between the relay station and the base station has a connection ID, and said combined capacity request includes said connection ID.

16. The method according to claim 1, further comprising the step, in the relay station, of classifying the detected capacity requests based on properties thereof.

17. The method according to claim 16 wherein the relay station classifies the detected capacity requests into urgent and non-urgent requests.

18. The method according to claim 17 wherein separate combined capacity requests are formed using the urgent and the non-urgent requests respectively.

19. The method according to claim 18 wherein said step of transmitting the combined capacity request includes immediately transmitting a combined capacity request formed using urgent requests, whilst delaying transmission of a combined capacity request formed using non-urgent requests.

20. The method according to claim 19 wherein the relay station waits for a predetermined time period to elapse before transmitting the combined capacity request formed from non-urgent requests.

21. The method according to claim 16, wherein each connection between a subscriber station and the base station is assigned one of a plurality of levels of quality-of-service (QoS), and said classifying step is performed based on the QoS.

22. The method according to claim 21, wherein each connection between a subscriber station and the base station has a connection ID with which QoS information is associated, the relay station obtaining the QoS based on the connection ID.

23. The method according to claim 1, wherein the system comprises at least one further relay station in communication with said relay station, the further relay station performing the same steps as said relay station in relation to further subscriber stations with said relay station acting as its base station, said relay station detecting a capacity request from said further relay station and using that capacity request in forming said combined capacity request.

24. The method according to claim 1, wherein one or more of the subscriber stations are mobile stations.

25. A wireless communication system in which subscriber stations are each operable for communication with a base station, the base station being capable of performing simultaneous communications with a number of subscriber stations by allocating an available capacity among the subscriber stations, the subscriber stations being required to issue capacity requests in order to obtain and/or maintain a connection with the base station, and communications between the subscriber stations and the base station being performed partly or wholly through at least one relay station, wherein: the relay station is arranged to detect capacity requests issued from a plurality of the subscriber stations, to use the detected requests to form at least one combined capacity request, and transmit the combined capacity request to the base station;the base station is responsive to the combined capacity request to reserve capacity for said plurality of subscriber stations; andthe relay station or the base station is arranged to allocate the reserved capacity among the plurality of subscriber stations.

26. A relay station for use in a wireless communication system in which subscriber stations are each operable for communication with a base station, the base station being capable of performing simultaneous communications with a number of subscriber stations by allocating an available capacity among the subscriber stations, the subscriber stations being required to issue capacity requests in order to obtain and/or maintain a connection with the base station, and communications between the subscriber stations and the base station being performed partly or wholly through the relay station, wherein the relay station comprises: a detector for capacity requests issued from a plurality of the subscriber stations;a combiner arranged to form at least one combined capacity request from the detected requests; anda transmitter for transmitting the combined capacity request to the base station; wherein the relay station is responsive to a notification of reserved capacity received from the base station, to allocate the reserved capacity among the plurality of subscriber stations.

27. The relay station according to claim 26, wherein communication in said system is performed through exchange of packets and the transmitter is arranged to transmit the combined capacity request in a medium access control layer header of such a packet.

28. The relay station according to claim 26, wherein the combined capacity request includes details of individual capacity requests detected by said detector.

29. The relay station according to claim 28, wherein the notification of reserved capacity received from the base station includes information on an individual amount of capacity for each subscriber station to be allocated by the relay station.

30. The relay station according to claim 26, wherein the combined capacity request does not include details of individual capacity requests detected by said detector.

31. The relay station according to claim 30, wherein the notification of reserved capacity includes an aggregate amount of capacity and the relay station is arranged to partition the reserved capacity among the plurality of subscriber stations.

32. The relay station according to claim 26, wherein the combiner is arranged to classify the detected capacity requests based on properties thereof.

33. The relay station according to claim 32, wherein the combiner classifies the detected capacity requests into urgent and non-urgent requests.

34. The relay station according to claim 33, wherein the combiner is arranged to form separate combined capacity requests using the urgent and the non-urgent requests respectively.

35. The relay station according to claim 34, wherein the transmitter is arranged for immediately transmitting a combined capacity request formed using urgent requests, whilst delaying transmission of a combined capacity request formed using non-urgent requests.

36. The relay station according to claim 35, wherein the transmitter is arranged to wait for a predetermined time period to elapse before transmitting the combined capacity request formed from non-urgent requests.

37. The relay station according to claim 32, wherein each connection between a subscriber station and the base station is assigned one of a plurality of levels of quality-of-service (QoS), and the classifying is performed based on the QoS.

38. The relay station according to claim 37, wherein each connection between a subscriber station and the base station has a connection ID with which QoS information is associated, and said classifying involves obtaining the QoS based on the connection ID.

39. The relay station according to claim 26, wherein the detector is arranged to detect a capacity request from at least one further relay station, the further relay station performing the same role as said relay station in relation to further subscriber stations, and said combiner is arranged to use that capacity request in forming said combined capacity request.

40. A base station for use in a wireless communication system in which subscriber stations are each operable for communication with the base station, the base station being capable of performing simultaneous communications with a number of subscriber stations by allocating an available capacity among the subscriber stations, the subscriber stations being required to issue capacity requests in order to obtain and/or maintain a connection with the base station, and communications between the subscriber stations and the base station being performed partly or wholly through at least one relay station, wherein the relay station detects capacity requests issued from a plurality of the subscriber stations and transmits a combined capacity request to the base station; the base station comprising: a decoder for decoding the combined capacity request received from the relay station;a processor, responsive to results of said decoding to reserve capacity for the plurality of subscriber stations; anda transmitter for informing the relay station of the reserved capacity.

41. The base station according to claim 40, wherein communication in said system is performed through exchange of packets and the decoder is arranged to decode the combined bandwidth request in a medium access control layer header of such a packet.

42. The base station according to claim 40, wherein the decoder is arranged to extract details of individual capacity requests made by the subscriber stations and contained in the combined capacity request.

43. The base station according to claim 42, wherein the processor is arranged to reserve an individual amount of capacity for each subscriber stations, said transmitter informing the relay station of the individual amounts of capacity.

44. The base station according to claim 40, wherein in the event that the combined capacity request does not include details of individual capacity requests, the processor reserves an aggregate amount of capacity for the subscriber stations, said transmitter informing the relay station of the aggregate amount of capacity.