GB2468893A

GB2468893A - Frame structure for use in an ad hoc communication network

Info

Publication number: GB2468893A
Application number: GB0905162A
Authority: GB
Inventors: Prince Arora
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2009-03-26
Filing date: 2009-03-26
Publication date: 2010-09-29
Also published as: GB0905162D0

Abstract

The invention provides for an Ad-hoc WiMAX network employing WiMAX end-user devices and a related method of network formation employing an underlying WiMAX physical layer frame structure for use in an Ad-hoc WiMAX network formed of WiMAX end user devices wherein the frame structure comprises a control and synchronisation sub-frame preceding series first and second sub-frames, the said first and second sub-frames being arranged to include user-related data as specified in a preceding control and synchronisation sub-frame which generally can be provided in a preceding frame.

Description

AD-HOC COMMUNJCATJONS NETWORK

The present invention relates to an Ad-hoc communications network and to end user devices arranged to be employed therein, a method of forming the same and a underlying physical layer frame structure for use in such a network.

Various forms of network configuration and arrangement have been provided for allowing communication between mobile radio communication devices. An example of one such arrangement comprises a so-called Ad-hoc network arrangement allowing for communication between network end user devices such as User Equipment devices in the form of mobile phone handsets.

While networks for such devices generally require the existence of a Base-Station (BS) and Core Network (CN) arrangement allowing for central administration of the communication process and the appropriate routing of messages etc. to the UP devices, Ad-hoc network arrangements serve to allow for communication between the UP devices but in a manner not involving, nor requiring, such central administration provided by the BS and CN.

An Ad-hoc network is therefore considered to comprise a network which consists of nodes employing a wireless interface to send packet data without any such central administration. To date Ad-hoc networks have been proposed for WiFi and Bluetooth capable devices and one such example is known from US 7 385 958.

However, such known arrangements are somewhat limited and do not readily allow for incorporation of an Ad-hoc functionality for all user devices and known network structures.

The present invention therefore seeks to provide for an Ad-hoc network and related communication features and devices having advantages over known such devices and networks.

In particular the present invention seeks to provide for a WiMAX Ad-hoc network for WiMAX end-user devices.

According to one aspect of the present invention there is provided a WiMAX physical layer frame structure for use in an Ad-hoc WiMAX network formed of WiMAX end user devices, the structure comprising a control and synchronisation sub-frame preceding series first and second sub-frames, the said first and second sub-frames being arranged to include user-related data as specified in a preceding control and synchronisation sub-frame.

The novel frame structure of the present invention is particularly advantageous in enabling WiMAX end user devices to form and function as an Ad-hoc WiMAX network.

Preferably the said user related data of the said first and second sub-frames can be specified in a control and synchronisation sub-frame of a previous frame.

Further, all of the said sub-frames can be separated by a guard space identified as a transition gap serving to allow for radio transmit/receive mode switching within the end user devices. As an example, such a guard space can be provided following the control and synchronisation sub-frame so that WiMAX Ad-hoc clients of a server-client network arrangement defined by the end-user devices can also transmit in the first sub-frame The control and synchronisation sub-frame can include a preamble portion serving to allow for ready detection of the said fmme structure as required by an end-user device.

Advantageously, the control and synchronisation sub-frame can include first and second MAP messages serving to locate positions of bursts and the first of which defines access and timing information for the said first sub-frame and second which defines access and timing information for the second sub-frame. Further the said first MAP can specify the length of the second MAP.

Yet further, the first sub-frame can be arranged to contain user related data which can included signalling messages between the end user devices and, for example, as specified in the first MAP and the second sub-frame can be arranged to contain user related data as specified in the second MAP.

In one example of the invention, the control and synchronisation sub-frame can be arranged to include a network information message including server information and network links information. In particular, the network information message is to be decoded by each node for providing updates concerning the status of the network.

The invention also provides for a WiMAX end user device arranged to operate within an Ad-hoc network and employing a frame structure as defined above. As one example, such an end user device can be arranged to operate as a server within the Ad-hoc network.

In this manner the device can be arranged to transmit data within the said control and synchronisation sub-frame.

Further, the device can be arranged for the allocation of one or more of client-device bandwidth, network connection identifiers and network link identifiers.

For transmission and reception scenarios, the device can be arranged to employ the first sub-frame for data transmission to a client device, and to employ the second sub-frame for receiving messaging from a client device.

In addition, or alternatively, the device can be arranged to fUnction as a client within the Ad-hoc network and for network monitoring on the control and synchronisation sub-frame.

Advantageously, when ftinctioning as a client, the transmit/receive function within either of the first and second sub-frames can be controlled by signalling from the server.

Further the device can be arranged to transmit to a server only within the second sub-frame. Also, the device can be arranged to transmit to a client selectively in either of the first and the second sub-frames.

For client-server communication, the control and synchronisation sub-frame can specify user-related data in a subsequent frame associated with the server.

For client to client, that is peer-to-peer communication the control and synchronisation sub-frame can serve to specify user-related data in a subsequent frame associated with a client within the network, In yet a further aspect of the invention there is provided a WiMAX network including a plurality of end user devices as defined above and comprising a server device and at least one client device.

The invention can also provide for a method of establishing an Ad-hoc WiMAX network comprising establishing a client server relation between a plurality of end user devices as defined above.

As will therefore be appreciated, the present proposal provides for means for implementing a WiMAX Ad-hoc network structure employing a client-server model.

Within such a client-server model, one WiMAX end user device, or node, is arranged to act as a WiMAX Ad-hoc Server, while the other one or more WiMAX devices (nodes) acts as a WiMAX Ad-hoc Client. This is advantageously enabled through the provision of the particular physical layer frame structure outlined above and employing three sub-frames comprising, as discussed further below, a broadcast sub-frame and first and second sub-frames. Such sub-frames are advantageously separated by way of guard spaces which allow for the radios of the end user devices to switch between transmitting and receiving modes, or vice versa, as required in particular during peer-to-peer communications.

In particular, it will be appreciated that the present invention exhibits an advantageous feature of enabling peer-to-peer communication between WiMAX Ad-hoc client devices such that the transit of information through the WiMAX Ad-hoc server device is not required.

The invention is described further hereinafter by way of example only, with reference to the accompanying drawings in which: Fig. I is a schematic diagram of a physical layer frame structure according to an embodiment of the present invention; Fig. 2 is a schematic representation of a WiMAX Ad-hoc network according to an embodiment of the present invention; Fig. 3 is a schematic representation of the relationship between consecutive frames employing the structure such as that illustrated with reference to Fig. 1; Fig. 4 is a timing diagram illustrating employment of a structure such as that of Fig. I in relation to four WiMAX Ad-hoc nodes engaged in server-client communication; and Fig. 5 is a timing diagram illustrating employment of a structure such as that of Fig. I in relation to four WiMAX Ad-hoc nodes engaged in client-communication.

Outlined first below is a description of the physical layer characteristics, and operational characteristics, of an Ad-hoc network arranged in particular to employ WiMAX end user devices.

As will be appreciated, a WiMAX Ad-hoc network comprises a personal area network, or other small network, in which WiMAX user devices such as PCMCIA, USB, MS etc. form part of the network for the duration of communication session. In the WiMAX Ad-hoc network, WiMAX user devices (also WiMAX Ad-hoe nodes/devices) can be connected by wireless links based on IEEE 802.1 6e-2005 standard and the WiMAX Ad-hoe network can be considered as a subset of a WiMAX network in which there is no requirement for centralised message passing devices, i.e. a BS or CN. Thus, two or more WiMAX user devices having an ability to cooperate can form a WiMAX Ad-hoc network.

Turning now to Fig. 1, there is provided a schematic diagram of a physical layer frame-structure 10 according to an embodiment of the present invention and upon which the advantageous operation of the WiMAX Ad-hoc network is based.

As illustrated, the physical layer of the WiMAX Ad-hoc network is structured into frames 10, each containing a Broadcast Sub-frame 12, First Sub-frame 14 and Second Sub-frame 16. The Broadcast Sub-frame 12 is arranged to provide key control and synchronisation information. The WiMAX Ad-hoc Server will be responsible for transmitting the Broadcast Sub-frame 12 and each WiMAX Ad-hoc Client can be arranged to decode the Broadcast Sub-frame 12. The illustrated components of the WiMAX Ad-hoc physical layer frame structure are as follows: An Ad-hoc Preamble 20 found at the start of a Broadcast Sub-frame and that serves for detection of the start of WiMAX Ad-hoc physical layer frame. After power-on, the WiMAX user devices will scan the frequency to detect the Ad-hoc preamble 20.

PCI-I. The Ad-hoc preamble is followed by a Frame Control Header (FCH) 22, as known from IEEE 802.16 which serves to specify the length of a First-MAP 24.

First-MAP. The broadcast First-MAP message 24 specifies the length of a Second-MAP 26, Ad-hoc Network Information portion 28 and also serves to define bursts start times and entire access for a scheduling interval of the First Sub-frame 14.

A broadcast Second-MAP message 26 is provided to define bursts start times and entire access for a scheduling interval of the Second Sub-frame 16.

Within the First Sub-Frame 14, First MAP Bursts 30 can be provided and which contain data corresponding to each user specified by the First-MAP 24.

Importantly, guard spaces 18 can be provided as illustrated after every Broadcast 12, First 14 and Second 16 Sub-frame which will allow end-user device radios to switch between transmitting and receiving mode or vice-versa, if required. The provision of the guard spaces 18 after the Broadcast Sub-frame 12 allows for WiMAX Ad-hoc Clients to also transmit in the First Sub-frame 14 if required. These guard spaces 18 are identified as Transition Gaps within Fig 1.

Second MAP Bursts 32 are provided within the Second Sub-Frame 16 and are arranged to contain data corresponding to each user specified by the Second-MAP 26.

Lastly, the Broadcast Sub-Frame includes an Ad-hoc Network Information portion 28.

An Ad-hoc Network Information message consisting of information related to the WiMAX Ad-hoc network. Each WiMAX Ad-hoc node will decode the Ad-hoc Network Information 28 in order to update with the status of the WiMAX Ad-hoc network.

A tabulated illustration of the content of the Ad-hoc Network Information portion is shown below.

Ad-hoc Network Information WiMAX Ad-hoc Server IP Address.

Information MAC Address.

Mode. Tx->Rx.

WiMAX Ad-hoc Links Information Link-Id Status (Idle/Active).

WiNfAX Ad-hoc Node#l WiMAX Ad-hoc Node#2 Information Information IP Address. IP Address.

MAC Address. MAC Address.

BConn. B_Conn.

P_Conn. P_Conn.

List of TCIDs with their List of TCIDs with their location (First/Second Sub-location (First/Second Sub-frame) information, frame) information.

Mode (Tx->Rx/Rx->Tx). Mode (Tx->Rx/Rx->Tx).

As shown, the Ad-hoc Network Information can consist of WiMAX Ad-hoc Server Information and WiMAX Ad-hoc Links Information.

In further detail the WiMAX Ad-hoc Server Information can consist of the IP Address and MAC Address of the WiMAX Ad-hoc Server. A Mode field can be provided to represent the mapping of transmitting (Tx)/receiving (Rx) mode with the First/Second Sub-frame of the WiMAX Ad-hoc Server.

The left side to the "->"can represent the mode following the First Sub-frame, while right side of the "->" will represent the mode following the Second Sub-frame. It should be appreciated that the Mode of the WiMAX Ad-hoc Server will be always Tx- >Rx. When an WiMAX Ad-hoc Client is reading only broadcast information or communicating with the WiMAX Ad-hoe Server, the Mode of the WiMAX Ad-hoe Client will be Rx->Tx. In the WiMAX Ad-hoe Client to Client communication, when WiMAX Ad-hoc Client is transmitting in the First Sub-frame, then the Mode of the WiMAX Ad-hoc Client will be represented by Tx->Rx. The Mode field in the Ad-hoc Network Information will help WiMAX Ad-hoe Clients to determine whether they have to transmit or receive in the First Sub-frame or Second sub-frame respectively.

Based upon the Mode field, WiMAX Ad-hoc Clients can configure themselves and start operating.

The WiMAX Ad-hoc Links Information can comprise information related to the links in the WiMAX Ad-hoc network, Primarily it can comprise an IP Addresses, MAC Addresses, B_Conns, P_Conns and TCIDs associated with the WiMAX Ad-hoc nodes.

The "Status" field can serve to represent whether the Link status is Idle or Active. The Active status of a link will indicate that some transaction/data session is in progress on this link, while the Idle status will indicate that WiMAX Ad-hoc nodes of this link are not communicating with each other or that the WiMAX Ad-hoc Clients are reading only broadcast information. The "Mode" field is as outlined above.

For an Active Link, the Mode field will not be same for both the WiMAX Ad-hoc nodes. Further the Mode field can be considered irrelevant when the status of link is Idle.

Turning now to Fig. 2, there is provided an illustration of a WiMAX Ad-hoe network 34 established between three WiMAX Nodes #1, #2, #3.

In the Illustrated example, Node #1 is defined as the server of the Ad-hoc network 34 whereas Nodes #2, #3 are defined as respective clients within the WiMAX Ad-hoc network 34.

In further detail, the first Ad-hoc node in the WiMAX Ad-hoc network which initiates the WiMAX Ad-hoc network will be known as W1MAX Ad-hoc Server. This node will be responsible for allocating CTDs, Link-Ids and bandwidth to other WiMAX Ad-hoc nodes and also broadcasting the physical layer frames and the broadcast information related to the WiMAX Ad-hoc network.

All of the other nodes except the WiMAX Ad-hoc Server to form the WiMAX Ad-hoc network will be act as WiMAX Ad-hoc Clients. To join the WiMAX Ad-hoc network, the WiMAX Ad-hoc Client will register with the WiMAX Ad-hoc Server. Further, the WIMAX Ad-hoc Client will establish a connection with other WiMAX Ad-hoc Clients with the help of WiMAX Ad-hoc Server which is responsible for allocating bandwidth to the link between two WiMAX Ad-hoc Clients.

With further reference to Fig 2, TP_Addr#[l..N] represents the IP Address of the WiMAX Ad-hoc node where N is the number of nodes in the WiMAX Ad-hoc network and as shown IP Addr# I is the IP Address of WiMAX Ad-hoc Node# 1.

MAC Addr4t[1..N] serves to identify the MAC Address of the WiMAX Ad-hoc node where N is the number of nodes in the WiMAX Ad-hoc network. Again, as illustrated MAC Addr#1 is the MAC Address of WiMAX Ad-hoc Node#1.

Link-Id#[1..NI[l..N] serves to identify the connection between two WiMAX Ad-hoc nodes. As shown in Fig 2, Link-Jd#13 illustrates the link between WiMAX Ad-hoc Node#I and Node#3 and so N is number of nodes in the WiMAX Ad-hoc network.

B_Conn# [I. .N] [1. .N] serves to identify Basic management Connection associated with the Link in the WiMAX Ad-hoc network. For example, B_Conn#12 represents the Basic management Connection assigned to WiMAX Ad-hoc Node#1 for communicating with the WiMAX Ad-hoc Node#2 on Link#12, while BConn#21 represents the Basic management Connection assigned to WiMAX Ad-hoc Node#2 for communicating with the WiMAX Ad-hoc Node#1 on Link#12. N is number of nodes in the WiMAX Ad-hoc network. B_Conn is similar to the Basic management Connection known from IEEE 802.16 or WiMAX Air Interface specification, but differs in that the Basic management connection will be unidirectional in WiMAX Ad-hoe network, while in IEEE 802.16 specification Basic Management connection is same in both uplink and downlink direction.

P_Conn#[1..N] [1..N] serves to identif' Primary management Connection associated with the Link in the WiMAX Ad-hoc network. For example, P Conn#23 represents the Primary management Connection assigned to WiMAX Ad-hoc Node#2 for communicating with the WiMAX Ad-hoc Node#3 on Link#23, while P_Conn#32 represents the Primary management Connection assigned to WiMAX Ad-hoc Node#3 for communicating with the WiMAX Ad-hoc Node#2 on Link#23. N is number of nodes in the WiMAX Ad-hoc network. P_Conn is similar to the primary management Connection known from in IEEE 802.16 or WiMAX Air Interface specification, but differs in that the Primary management connection will be unidirectional in WiMAX Ad-hoc network, while in IEEE 802.16 specification Primary Management connection is same in both uplink and downlink direction.

As will be explained further, the Ad-hoe network such as that illustrated in Fig 2 can provide for server-client, or if required, more client-client communication, and as based upon the relative frame relationships.

Turning now to Fig. 3 there is provided a schematic representation of three frames comprising a central frame 36, a preceding frame 38 and subsequent frame 40, The structure of each of the frames is in accordance with that illustrated by reference to Fig. I but for ease of reference only the first and second MAP portions 24, 26 of the broadcast sub-frame 12, and respective first and second MAP bursts 30, 32 of the first and second sub-frames 14, 16 are shown so as to elarifS' their relationship.

As will be appreciated from Fig 3, and in particular the arrows provided therein, a timing information within the first MAP and second Map 24, 26 will be reLative such that the first MAP 24 and second MAP 26 of each frame will in fact represent the location of the first MAP burst 30 and second MAP bursts 32 of a next frame respectively, i.e. the MAP of frame 38 represents the location of the MAP bursts of frame 36.

Turning now to Fig. 4, there is provided an illustration of data transfer between the server node and the client nodes of a WiMAX Ad-hoc network according to an embodiment of the present invention.

As will be appreciated, node #1 is defined as the server within the server-client relationship and, at the beginning of the time span illustrated by the diagram each of the client nodes #2, #3 and #4 is arranged to transmit data 42 to the server node #1 during the respective second sub-frames 16 of the frame structure.

As discussed previously, the server node #1 is arranged so as to always transmit on its broadcast sub-frame and also during the first sub-frame 14 and to allow for reception during its second sub-frame 16.

For alignment with this, the first 12 and second 14 sub-frames of the client nodes #2, #3, #4 are conversely arranged for reception during the broadcast sub-frame and the first sub-frame and transmission during the second sub-frame as illustrated.

Continuing further through the timing diagram, it is determined that a first MAP portion of a broadcast sub-frame 12' of a later frame provides an indication that MAP burst containing data for the three client nodes #2, #3, #4 is provided in the first sub-frame 14' of the next frame; such data transfer being illustrated by arrows 44.

As will be appreciated, for such server-client communication, the first and second sub-frames of the server node #1 are established as transmission and reception sub-frames respectively, whereas the first and second sub-frames of the client nodes #2, #3, #4 are established as reception/transmission respectively.

With regard to Fig. 5, there is provided a similar timing diagram but now relating to the control of data transfer arising for client-to-client i.e. peer-to-peer communication.

A frame structure substantially as illustrated in Fig. 1 is again apparent for each of the four nodes and again with each of the sequential frames comprising a broadcast sub-frame 12, first sub-frame 14 and second sub-frame 16 and with the frames repeated as shown in the diagram.

The server node #1 is again arranged for transmission during the first sub-frame 14 and reception during the second sub-frame 16.

In this illustrated example however, the first MAP portion of the broadcast sub-frame 12 from the server node #l indicates bursts allocated within the next preceding frame to client nodes #2, #3 to perform a transfer of data to node #4 as illustrated by arrows 46.

However, as will be appreciated, although initiated from the server node #1, it will be appreciated that the client-to-client transfer of data is executed in a peer-to-peer manner and so does not itself involve the server node #1. Thus, while the invention proposes an Ad-hoc client-server structure not requiring a BS nor CN, a peer-to-peer arrangement can be provided within this structure wherein no data is transferred to the server and so only between the clients.

Also, through reference to the respective first sub-frames 14' of client nodes #2, #3, #4, subsequent to the burst allocation from the server node #1, the mode of operation of the first sub-frame of client nodes #2, #3 is switched to "transmit" whereas the mode of the first sub-frame of client node #4, remains as "receive".

Thus to summarise the above example in particular, in the WiMAX Ad-hoc network, one WiMAX Ad-hoc node will act as a WiMAX Ad-hoe Server, while others will act as WiMAX Ad-hoc Clients. The WiMAX Ad-hoe Server is arranged to transmit the physical layer frame, and all nodes in the WiMAX Ad-hoc network can be provided with a unique TP/MAC address.

Further, the WiMAX Ad-hoc Server assumes responsibility for broadcasting the WiMAX Ad-hoc network information, and for allocating CIDs and Link-Ids, which will be unique in the WiMAX Ad-hoc network.

As noted, the B_Conn, P_Conri and Transport connections are associated with each Link-Id and are arranged to be unidirectional in nature.

The WiMAX Ad-hoc Server can also be responsible for allocating bandwidth to the WiMAX Ad-hoc Clients and is arranged to always use the First Sub-frame to transmit the information to the WiMAX Ad-hoe Client. The WiMAX Ad-hoc Clients will always use the Second Sub-frame to transmit the information to the WiMAX Ad-hoc Server and so this implies that in the WiMAX Ad-hoc Server and WiMAX Ad-hoc Client communication, when the WiMAX Ad-hoc Server is transmitting, the WiMAX Ad-hoc Client will be in receiving mode or vice-versa.

Thus, the WiMAX Ad-hoc Server will be in transmitting and receiving mode in the First and Second Sub-frames respectively and can be arranged to always transmit the Broadcast Sub-frame and each client will be arranged to listen on the Broadcast Sub-frame.

As for the WiMAX Ad-hoc Clients, there can transmit or receive information in both the First and Second Sub-frames and so it is determined that same mode (transmitting/receiving) will not exist in both the First and Second Sub-frames in one frame.

In the WiMAX Ad-hoc Server to Client communication or when WiMAX Ad-hoc Client is reading only broadcast information, the WiMAX Ad-hoc Client will be in receiving and transmitting mode in the First and Second Sub-frames respectively.

However, in the WiMAX Ad-hoc Client to Client communication, such directions will not be fixed and the WiMAX Ad-hoc Server can determine whether the WiMAX Ad-hoc Client transmits in the First or Second Sub-frame.

Alternatively, in the WiMAX Ad-hoc Client to Client communication, during transmission in the First Sub-frame, the WiMAX Ad-hoc Client will not be able to receive information from the WiMAX Ad-hoc Server nor from other WiMAX Ad-hoc Clients which are transmitting in the First Sub-frame of the same frame.

En the receiving mode, the WiMAX Ad-hoc Client will not receive information in the First Sub-frame from other WiMAX Ad-hoe Clients which are receiving in the same First Sub-frame.

As noted, the invention allows for client peer-to-peer communication and so two WiMAX Ad-hoc clients can communicate with each other directly without passing information via the WiMAX Ad-hoc Server.

It should however be appreciated that the present invention is not restricted to the details of the foregoing enhancements.

Claims

CLAIMS1. A W1MAX physical layer frame structure for use in an Ad-hoc WiMAX network formed of WiMAX end-user devices, the structure comprising a control and synchronisation sub-frame preceding series first and second sub-frames, the said first and second sub-frames being arranged to include user-related data as specified in a preceding control and synchronisation sub-frame.
2. A frame structure as claimed in Claim I, wherein the said user-related data of the said first and second sub-frames is specified in a control and synchronisation sub-frame of a previous frame.
3. A frame structure as claimed in Claim 1 or 2, wherein all of the said sub-frames are separated by a transition gap serving to allow for radio transmit/receive mode switching within the end-user devices.
4. A frame structure as claimed in Claim 1, 2 or 3, wherein the control and synchronisation sub-frame includes a preamble portion serving to allow for detection of the said frame structure.
5. A frame structure as claimed in Claim 1, 2, 3, or 4, and wherein the control and synchronisation sub-frame includes first and second MAP messages the first of which defines access and timing information for the said first sub-frame and the second of which defines access and timing information for the second sub-frame.
6. A frame structure as claimed in Claim 5, wherein the said first MAP specifies the length of the second MAP.
7. A frame structure as claimed in Claim 5 or 6, wherein the first sub-frame is arranged to contain user related data as specified in the first MAP and the second sub-frame is arranged to contain user related data as specified in the second MAP.
8. A frame structure as claimed in any one of more of the preceding claims, wherein the control and synchronisation sub-frame is arranged to include a network information message including server information and network links information.
9. A WiMAX end user device arranged to operate within an Ad-hoc network and employing a frame structure as claimed in any one or more of the preceding claims.
10. A user device as claimed in Claim 9, and ananged to operate as a server within the Ad-hoc network.
11. A device as claimed in Claim 10, and arranged to transmit data within the said control and synchronisation sub-frame.
12. A device as claimed in Claim 10 or 11, and arranged for the allocation of one or more of client-device bandwidth, network connection identifiers and network link identifiers within the network.
13. A device as claimed in Claim 10, 11 or 12, and arranged to employ the first sub-frame for data transmission to a client device.
14. A device as claimed in Claim 10, 11, 12 or 13, and arranged to employ the second sub-frame for receiving messaging from a client device.
15. A device as claimed in any one or more of Claims 9 to 14, and arranged to operate as a client within the Ad-hoc network and for monitoring the network during the control and synchronisation sub-frame.
16. A device as claimed in any one or more of Claims 9 to 15, wherein a transmit/receive function within either of the first and second sub-frames is controlled by signalling from the server.
17. A device as claimed in any one of Claims 9 to 16, and arranged to transmit to a server only within the second sub-frame.
18. A device as claimed in any one of Claims 9 to 17, and arranged to transmit to another client device selectively in either of the first and the second sub-frames.
19. A device as claimed in Claim 18, the said selective transmission being responsive to resource allocation from a server device.
20. A device as claimed in any one or more of Claims 9 to 19, and arranged such that the control and synchronisation sub-frame serve to specify user-related data in a subsequent frame associated with the server for server-client communication.
21. A device as claimed in any one or more of Claims 9 to 19, wherein the control and synchronisation sub-frame serve to specify user-related data in a subsequent frame associated with a client within the network for client peer-to-peer communication.
22. A WiMAX network including a plurality of end-user devices according to any one or more of Claims 9 to 21 and comprising a server device and at least one client device.
23. A method of establishing an Ad-hoc WiMAX network comprising establishing a client server relation between a plurality of end user devices as defined in any one or more of Claims 9 to 21.
24. WiMAX physical layer frame structure substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1, 3, 4 and 5 of the accompanying drawings.
25. A WiMAX end user device substantially as hereinbefore described with reference to any one or more of the accompanying drawings.
26. A WIMAX network substantially as hereinbefore described with reference to, and as illustrated in, Fig. 1 of the accompanying drawings.
27. A method of establishing an Ad-hoc WiMAX network substantially as hereinbefore described with reference to the accompanying drawings.