GB2430113A

GB2430113A - Inter-piconet communication

Info

Publication number: GB2430113A
Application number: GB0518468A
Authority: GB
Inventors: Zhong Fan
Original assignee: Toshiba Research Europe Ltd
Current assignee: Toshiba Europe Ltd
Priority date: 2005-09-09
Filing date: 2005-09-09
Publication date: 2007-03-14
Anticipated expiration: 2025-09-09
Also published as: GB0518468D0; GB2430113B

Abstract

The present invention relates to inter-piconet communication amongst wireless communications devices, and in particular though not exclusively to the IEEE802.15.3 wireless piconet protocol. The present invention provides a wireless communications system comprising: a plurality of piconets each supporting wireless communications amongst a number of wireless devices on a respective piconet channel (ch1,ch2), each piconet having an associated piconet coordinator device (PNC) which coordinates use of the respective piconet channel; wherein communications between a sending device (S) in a sending piconet and a destination device (D) in a destination piconet are routed through their respective piconet coordinator devices (PNC1,PNC2), the respective piconet coordinator devices communicating with each other using a said piconet channel (ch1 or ch2).

Description

1 2430113 Inter Piconet Communication

Field of the Invention

The present invention relates to inter-piconet communication amongst wireless communications devices, and in particular though not exclusively to the IEEE8O2. 15.3 wireless piconet protocol.

Background of the Invention

Wireless devices capable of communicating over relatively short distances (compared with cellular or walkie talkie type systems) are increasingly ubiquitous. Example devices include PDAs, laptop computers, printers and other peripheral devices, cameras, and mobile or cell phones (in addition to their cellular wireless communications capabilities). Various applications benefit, including providing office and home connectivity amongst local devices without the use of cables. Common protocols include WiFi (IEEE8O2. 11) which provides a medium range wireless local area network (WLAN) and Bluetooth TM which provides a short range piconet. These two protocols have different power consumption requirements and available bandwidths, and respectively have ranges of approximately I OOm and 1 Om.

However there is an increasing need for short range and very high data rate wireless communications amongst suitably capable wireless communications devices, for example to transfer data between "personal" devices such as PDA's and cameras, headsets, cell phones, and media centres. An example of a high data rate application is transmitting HDTV signals between a DVD player/recorder and a TV. Typically many of these devices will be held within the clothing or hands of a user in order to form a wireless personal area network (WPAN), but also known here as a piconet. Ultra-wide- band (UWB) technologies are being promoted for such applications, and an example UWB enabling technology is multi-band orthogonal frequency division multiplexing (MB-OFDM). This uses 2 or 3 OFDM bands in order to define a band group, which is then channelised using time and frequency codes.

This MB-OFDM technology can be used to support UWB piconets or WPAN's such as those defined in the IEEE8O2.1 5.3 specification. This defines how intra-piconet communications using an allocated PHY channel such as a MB-OFDM UWB channel are achieved. The devices on a piconet communicate with each other on a peer-to-peer basis, however a piconet coordinator device (PNC) is determined which allocates time on the piconet's UWB/MBOFDM channel for these peer-to-peer connections. This time allocation may be achieved on a contention basis or using time slots. At the MAC layer, shortened addresses are defined and used within the piconet to identify and communicate with other devices therein.

In order to communicate with "external" devices outside the piconet, inter-piconet communications, the 802.15.3 protocol defines the concept of a child piconet in which one of the devices in the piconet which is within wireless range of an external device - a device defined as a child piconet coordinator (child PNC) - communicates with the external device using the piconet's UWB channel. Because the child piconet is an extension of the piconet and uses the same channel, the coordinator device (PNC for the entire piconet including child piconet) allocates time for communications between the external device and devices within the piconet proper. These communications are relayed from the external device through the child PNC device to the rest of the piconet.

This significantly increases channel overhead because two time slots are required to relay communications between the external device and the rest of the piconet; and this also complicates the time allocation overhead on the PNC.

Summary of the Invention

In general terms, the present invention provides a system and method in which inter- piconet communications between devices in different piconets, for example IEEE8O2. 15.3 piconets, are relayed using piconet co-ordinator (PNC) devices within each separate piconet. The co-ordinator devices are coupled together using one of the piconet channels or a separate communications channel, for example a wired link, WiFi or possibly even a further separate piconet channel. Such an arrangement reduces the overhead on the respective piconet channels because only a single connection is required between a device wanting to communicate with a device in another piconet and respective piconet coordinators. Using a connection set up across multiple piconets on multiple PI-IY channels makes use of the multiple channel capacity. Therefore the capacity of the piconets is increased because they are using two or more UWB or PHY channels rather than the single UWB or PHY channel of the child piconet approach.

Furthermore, the timing allocation task is eased, and the range extension achieved can be significantly improved as there is no requirement for the external device to be within the piconet (UWB) channel wireless range of one of the piconet devices. For example the separate communications channel between the two piconet coordinator devices may be a WiFi link, at up to lOOm compared to the more typical lOm of a piconet, or it may be a wired connection through the Internet for example; and therefore in principle an unlimited range extension.

In one aspect there is provided a wireless communications system comprising a plurality of piconets, such as IEEE8O2.15.3 piconets, each supporting wireless communications amongst a number of wireless devices on a respective piconet channel, each piconet having an associated piconet coordinator device (PNC) which coordinates use of the respective piconet channel. The system is arranged such that communications between a sending device in a sending piconet and a destination device in a destination piconet are routed through their respective piconet coordinator devices, and the respective piconet coordinator devices communicate with each other using a said piconet channel, for example either the sending or destination piconet channels.

In addition to the advantages mentioned above, the use of a piconet channel for communications between the two piconet coordinator devices provides a simple low cost solution that can be implemented by low cost single transmitter devices.

The piconet channel used between the coordinator devices may be that of the destination device, the sending device, or another piconet. The destination device can be "found" by implementing the coordinator of the sending device to sequence through a number of piconet channels with a request message until the coordinator device for the destination device is found. Alternatively, a look-up table of which piconet channel the destination device is currently associated with could be used.

The sending and destination devices may be arranged to switch to the same piconet channel for communications with their respective piconet coordinator devices, or one of the coordinator devices could be used to switch between channels. The devices switching channels from their "normal" piconet channel can be configured to send "switiching channel" messages to other devices on their normal piconet.

In an embodiment, a sending or requesting device within a piconet sends a request on the piconet channel (Ch. 1) to its respective coordinator device for communicating with an external or destination device which does not form part of the piconet. The coordinator device then sends requests to other piconet coordinator devices using different piconet channels over the separate communications channel. When a piconet coordinator on one of those different piconet channels (Ch.2) receives the request and the destination device is within its piconet, it forwards the request to the destination device on the respective piconet or UWB channel (Ch.2). The device responds to its respective piconet coordinator over the respective piconet channel (Ch.2), and in turn this response is forwarded to the initial or sending piconet coordinator over the same channel (Ch.2). The coordinating device of the original or sending piconet then forwards the response to the sending or requesting device on the first piconet channel (Ch. 1). The sending device then sends data to the destination device using the channel of the destination device (Ch.2), via the two coordinator devices. Alternatively, the data from the sending device can be sent first to its respective coordinating device on the piconet's normal channel (Ch. 1), and the coordinating device then switches to the other channel (Ch.2) for transmitting to the other coordinating device and the destination device.

The multi-hop multi-channel arrangement of the embodiment reduces traffic on the piconet of the sending device, and can significantly extend the range of the requesting device compared with known arrangements. It also makes more efficient use of the multiple channels available, and can be used by simple single transmitter devices as only the piconet channels are used.

Also rather than broadcasting requests to communicate to a destination device outside a piconet and relying on an ad hoc multi-hop propagation mechanism as described in the AODV (ad-hoc on-demand distance routing vector) protocol for example, the requesting device forwards the request to its piconet coordinating device which uses a separate inter-piconet communications channel to find the destination device in another piconet.

The embodiments are especially well suited to extending the range of devices using the IEEE8O2. 15.3 protocol to communicate using UWB channel based piconets, however they are not restricted to this protocol or underlying channel technology. For example another physical layer PHY technology could be used such as DS-UWB (direct sequence ultra wideband), or even a narrower channel bandwidth technology such as OFDM as used in IEEE8O2. 11 (WiFi). Similarly, the embodiments may be applied to any multi-channel wireless networks such as IEEE8O2. 11 (WiFi) for example, and are not restricted to piconets or WPAN.

In another aspect there is provided a wireless communications system comprising: a plurality of piconets each supporting wireless communications amongst a number of wireless devices on a piconet channel, each piconet having a piconet coordinator device which coordinates use of the respective piconet channel by dividing portions of channel use time amongst the devices; such as implemented in the IEEE8O2.15.3 protocol. The system also comprises an inter-piconet communications link which couples the piconet coordinator devices together; and means for enabling communication between a sending device in a sending piconet and a destination device in a destination piconet using respective intermediate piconet coordinating devices and the inter-piconet communications link.

A network layer address can be used for the request message for the destination device when using a non-piconet channel between the coordinating devices, and the inclusion of for example such an IP address can be used to trigger the coordinator devices to process the corresponding packet as destined for another device (sending or destination).

There is also provided a wireless communication device for communicating with a destination wireless communication device and comprising: means for sending a request for connection to the destination device on a sending piconet channel to a sending piconet coordinator device which coordinates access to the first piconet channel amongst wireless communications device forming the first piconet; means for receiving a response on the first piconet channel from the coordinator device noting another piconet channel to switch to for communicating with destination device; means for sending traffic data for the destination wireless communications device to the sending piconet coordinator wireless communications device using the other piconet channel.

There is also provided a piconet coordinating device comprising: means for coordinating access to a sending piconet channel amongst a number of devices forming a sending piconet; means for receiving a request for connection to a destination device on the sending piconet channel from a sending device, the destination device not being part of the first piconet; means for forwarding the request on a destination piconet channel to a destination piconet coordinating device for a second piconet comprising the destination device; means for receiving a response on the destination piconet channel from the destination piconet coordinating device; means for forwarding the response to the sending device on the sending piconet channel; and means for relaying communications between the sending and destination devices including means for communicating with the destination piconet coordinating device using the destination piconet channel.

There are also provided corresponding methods of operating the systems and devices defined above.

There is also provided a method of establishing a communications route between devices using different piconets, the method comprising: sending a route request message from a sending device on a sending piconet for establishing a route with a destination device to a coordinator device for said sending piconet on an associated sending piconet channel; receiving the route request message and forwarding to a coordinator device for a destination piconet associated with the destination device on a destination device channel. The destination coordinator device may then forward this message to the destination device on the respective destination device piconet channel.

The method further comprises forwarding a route reply message from the destination device to the sending piconet coordinating device on the destination piconet channel; forwarding the route reply message to the sending device on the sending piconet channel. The route reply message may be forwarded between coordinating devices on either of these piconet channels, a separate piconet channel, or over a different teclmology link such as wired Ethernet for example.

The route reply message can indicate a piconet channel for the communications route, such that the two coordinator devices and optionally both of the sending and receiving devices communicate with each other using the indicated piconet channel.

There is also provided a method of inter-piconet communications between a sending device in a sending piconet having a sending piconet channel and a destination device in a destination piconet having a destination piconet channel, the piconets operating according to the IEEE8O2. 15.3 protocol. The method comprising establishing a communications route between the sending and destination devices and respective sending and destination piconet coordinator devices; and establishing a communications route between the sending and destination piconet coordinator devices using one of the sending or destination piconet channels.

Brief Description of the Drawings

Embodiments will now be described with reference to the following drawings, by way of example only and without intending to be limiting, in which: FIG 1 illustrates a known method of extending the range of a piconet defined by the IEEE8O2. 15.3 protocol; FIG 2 is a schematic illustrating a communications system according to an embodiment; FIG 3 is a flow chart illustrating a method of operating the system of FIG 2; FIG 4 is a signal flow diagram also illustrating operation of the system of FIG 2; FIG 5 is a schematic illustrating a communications system according to another embodiment; and FIG 6 is a schematic illustrating the MAC and Network layer processes operating on the various devices involved in the embodiments.

Detailed Description

Figure I is a schematic illustrating a number of wireless communications devices arranging themselves into a piconet according to the IEEE8O2.15.3 protocol. The IEEE8O2. 15.3 piconet 1 utilises a single UWB MB-OFDM channel to enable peer-to- peer connections 3 between devices 2 (m, n, o, p, q) making up the piconet 1. A discovery procedure is defined in order to allow each device 2q to discover other devices 2m-p in the piconet 1. If the necessary peer information is not available, a device executes the peer discovery procedure before any actual data transmission. Each device in the 802.15. 3 piconet may use a PNC Information Request (Info Req) command to obtain information about other devices in the piconet from the PNC. In addition or alternatively, a device may send a Probe Request command directly to another device to obtain other information required for peer-to-peer communication.

Furthermore, all devices in the piconet are able to use the Channel Status Request and Channel Status Response commands to gather information about the quality of their links with other devices. All these commands are exchanged in the contention access period (CAP) of superframes which are described in more detail below.

Following discovery, a sending device 2q can send data or otherwise communicate with another device 2n in the piconet 1 using the piconets UWB channel. The piconet 1 can support multiple peer-to-peer connections 3 by allocating time on the piconets channel to the different connections 3. The time allocation is provided by a piconet coordinator (PNC) 6, which is one of the devices 2 within the piconet 1 that is "appointed" as such.

Determination of the PNC 6 may be made based on processing power and battery resources of the various devices, and this is detailed in the IEEE8O2.15.3 specification.

The PNC 6 then controls access to the common piconet channel by allocating time slots or dividing portions of channel use time amongst the devices of the piconet; or using a contention based mechanism for requesting peer-to-peer connections 3, as detailed in the specification. The allocation of slots of channel use time compares with other protocols such as IEEE8O2.11 in which all of the channel use time per frame is allocated to a device using a contention mechanism.

The IEEE8O2.15.3 specification includes a mechanism for extending the range of the piconet 1, using a child piconet 4. External devices 2r-s are outside the normal range of the piconet I, but are linked into it by using the closest in-piconet node 2p as a relay - this is defined as the child piconet coordinator or child PNC. The range of the "un-extended" piconet corresponds to the extent to which each of the devices within the piconet can communicate with the PNC device, and may roughly be thought of as a circle centred on the PNC; the radius of which will depend on factors such as the beacon transmit power from the PNC, the modulation used and other factors well known to those skilled in the art. Using the same UWB channel, the external devices 2r-s are able to form connections 5 with the child PNC or relay device 2p, which can then route connections on to the appropriate device 2m-o,q within the piconet proper 1. As the devices 2r-s within the child piconet are using the same piconet channel, their time allocation on the channel is also controlled by the PNC 6.

This arrangement increases traffic on the allocated piconet channel because two time allocations of connections 3 and 5 are required to support a virtual connection between a device 2s in the child piconet 4 and a device 2n in the piconet 1. Further, the relay or child PNC device p is required to support these two connections in addition to any of its own, which reduces its battery life and may interfere with its capability to support its own connections. The time allocation process and signalling is also complicated by having to allow for two connections 3 and 5 to support a child piconet device 2r-s.

Figure 2 shows a wireless communications system comprising piconets such as those defined in the IEEE8O2.15.3 specification. The system comprises two piconets lOlA and 1OIB each supporting a number of wireless devices 102. The wireless devices 102 of each piconet 101 organise themselves into separate piconets using distinct piconets channels, for example different UWB MB-OFDM channels (Chi, Ch2). Each piconet 101 A and 101 B has a respective piconet coordinator 106 - PNC 1 and PNC2 respectively. A possible piconet channel connection 108 between the two piconets lOlA and 1OIB is available between the two piconet coordinators 106. This will typically be supported by either of the two piconet channels Chi or Ch2. Alternatively a separate non-piconet channel communications link 107 could be used, for example a wired link using an Ethernet connection, an Internet "connection"; or another wireless link for example IEEE8O2. 11. Both the piconet (108) and the non-piconet (107) communications links can be termed an inter-piconet communications link.

Referring also to Figure 3 which shows a method of inter-piconet communication, and Figure 4 which illustrates a signalling diagram showing the movement of control messages between the various devices. When a sending device S within the first or sending piconet 101 A wants to communicate with a destination device D, it first tries the discovery procedure noted above to locate the destination device D within the piconet lOlA (210). If that fails, the sending device S sends a route request message and here termed a RREQ message using the sending devices piconet channel (Chi) to the piconet's coordinator PNCI 106 (220), requesting a communications route to the destination device D. The coordinator PNC I multicasts the RREQ to other coordinators PNC2 106 on other piconets 101 B (225). Typically this is implemented by repeating the message transmission (on the piconet channel based inter- piconet link 108) but stepping through the various piconet channels (Ch 1 - Ch2), such as those defined by MB-OFDM. The coordinating device PNC1 sends the request message RREQ on the first channel (Ch2), and awaits a response. If after a timeout period, no response is received, the next channel is tried and so on. Other piconet coordinators PNC2 receiving the request RREQ determine whether the destination device D is part of their piconet 1O1B (230), and if so, forwards the request on to the destination device D (240) using that piconet's channel (Ch2).

A standard contention protocol such as CSMA (carrier sense multiple access) can be used in case PNC1 and a device on another channel (eg Ch.2) try to communicate at the same time. Also PNC 1 can be configured to transmit the RREQ more than once if it doesn't get through. The RRFQ message sent by PNC 1 can be part of a standard request for connection to the corresponding piconet (eg of Ch.2) or a separately defined control signal.

On receiving the request message RREQ, the destination device D selects a channel for communication (Ch2) to include in a responding message, typically that of the destination piconet 101 B. The destination device D then sends a response message or route reply packet RREP back to its piconet coordinator PNC2, again using the destination piconet's channel (Ch2) (245). The message also includes a channel time allocation request (CTA) for its coordinator PNC2, and optionally the coordinator PNC1 of the sending device S. The destination device's piconet coordinator PCN2 then forwards the RREP message back to the sending device's piconet coordinator PCN1 using the same destination piconet channel Ch2. The sending device's coordinator PNC1 receives this RREP message on the other (destination) piconet's channel (Ch2), and forwards it to the sending device S on its own (sending) piconet channel (Ch 1).

On receiving the response message RREP containing the "switch-to" channel information (Ch2), the sending device S starts communication with the destination device D by forwarding and receiving packets to its piconet coordinator device PNC 1, which relays them to the destination device's piconet coordinator PNC2, which in turn relays them to the destination device D. The piconet channel used for supporting this virtual multi-hop connection 108 is configurable. Typically, the destination device's piconet channel (Ch2) is used, and in this case the sending device S communicates with its coordinator PNC 1 using that channel (Ch2). Once the connection is no longer needed, the sending device reverts to the channel (Chi) of its own piconet lOlA. This is particularly useful for devices which support only one channel connection at a time. A "switch" or "channel switching notification" control message can be employed to let other members of the piconet know that the sending and coordinator devices will be temporarily on another channel whilst the connection to the destination device is supported. A "switch-back" or another "channel switching notification" message can then be used to let the rest of the piconet know that these devices are back on the original channel.

By having all devices in the route on the same channel (eg Ch2), this reduces per packet switching times which reduces delay on the interpiconet connection 108. It does however require the sending device S and the coordinating device PNC 1 to switch to a different channel from the rest of their piconet 101 A for each packet for the duration of the connection to the destination device D. In an alternative arrangement, the sending device S may send and receive packets to and from the destination device using its own (sending) piconet's channel (Chi). The sending device's piconet coordinator PNCI then switches these packets between its own piconet's channel (Chi) and the destination device's piconet channel (Ch2). The advantage of this approach is that route establishment is decoupled from channel assignment. However there is a channel switching delay of about 9ns for MB-OFDM which can add overhead (delay) to the protocol.

In further alternatives, the destination device's coordinator PNC2 may switch packets between the two piconet channels (Chi and Ch2), or the destination device D may communicate with its coordinator device PNC2 using the sending device's piconet channel (Chi) for the duration of the connection to the sending device S. Whatever arrangement is used, the two coordinator devices PNC 1 and PNC2 allocate time for the various connections to make the inter-piconet connection 108 between the sending S and destination D devices (250). The CTA (channel time allocation) request included in the RREP by the destination device D can be used, and the time allocation for the connection set up as is known. The PNC transmits a beacon at the start of each time period or superframe. This superframe contains a number n of channel use time allocation periods (CTA1 - CTAn) which are allocated to the devices within the piconet by the PNC, and notified using the beacon. The superframe also includes a contention access period for devices to request new or additional channel time allocations, or to release them. In the first arrangement described above, the destination device's coordinator PNC2, in addition to allocating time (eg CTA1 - CTA6) on the common channel for the other various devices 102 of its piconet biB, must allocate time (eg CTA7) for a connection between itself and the destination device D, as well as a connection or destination piconet channel use time allocation (eg CTA8) between itself (PNC2) and the coordinator device (PNCI) of the sending device's piconet lOlA.

By just using the two piconet channels (eg Ch.1 and Ch.2) for setting up the inter-piconet communications session or external link 108, a simple low complexity and low cost solution is provided, which supports devices with a single transmitter.

In another embodiment, a separate communications link 107 is used as the inter- piconet link, and may comprise a wired link such as Ethernet, or a wireless link not using one of the sending or destination piconet channels (Chl,Ch2). Examples include a third piconet channel, or a different technology such as IEEE8O2. 11 (WiFi). In an IEEE8O2. 15.3 piconet 101 A, devices 102 communicate with each other by sending packets on the UWB channel with the appropriate shortened MAC layer address.

However in order to send packets to a device D on a different piconet 101 B, the packets additionally include that device's IP address, for example as part of the payload or data part of a standard MAC layer traffic packet. This IP address or some other network layer address or flag can beused by a network layer process within the PNC1 as described in more detail later. This allows the coordinating device (PNC1) to recognise that packets addressed to its shortened MAC layer address, from the sending device S are in fact destined for the destination device D and not the coordinator PNC 1. The coordinator PNC I is then triggered to relay the relevant data (eg RREQ and IP address) from these packets to the coordinator PNC2 of the other piconet 1O1B. Thus intra- piconet communications 107 are implemented at the MAC layer, whereas inter-piconet communications are implemented at the network layer. The network layer connection between PNC I and PNC2 will typically be implemented over the separate communications link 107 using the IP network layer protocol.

This arrangement requires additional network layer processing which will be familiar to those skilled in the art, however it can extend the range of the inter-piconet link 107 as this is no longer dependent on the proximity of the two PNC devices to ensure wireless communications using the IEEE8O2.1 5.3 protocol.

These embodiments provide a simple low cost method of inter-piconet communication, especially amongst single transceiver devices which can only support connections on one piconet channel at a time. Also, whilst only two piconets are shown, it will be recognised that this system can be easily scaled to incorporate a much larger number of piconets.

The embodiments also compare favourably with methods such as those in the AODV protocol in which the sending or requesting device floods route request messages (RREQ) to all devices it is wirelessly connected to. These devices in turn broadcast the RREQs and so on until the destination device is reached; thus the RREQ propagates out using multiple intermediate devices. The destination device responds and this is propagated back to the requesting device with additionally receives routing information to get to the destination device. Since the RREQ messages are all broadcast in the contention access period, this adds considerably to the channel overhead, and may result in many collisions.

In the embodiments, the format of AODV RREQ and RREP messages can be used, however these messages are unicast, for example from the sending device S to its coordinating device PNCI, which reduces control traffic.

Figure 5 illustrates another embodiment in which like entities are labelled the same. The system is similar to that of Figures 2-4, however in this embodiment each coordinating device (PNC 1, PNC2) maintains a neighbour piconet table NPT. The NPT contains a list of neighbouring piconets, their devices and channel information. The NPT can be maintained using HELLO messages sent on all channels in a round-robin fashion. PNCs exchange a complete copy of their NPT tables upon initialization. Then like link-state protocols, updates are multicast only when a change (e.g. device arriving or leaving) has occurred. When a PNC receives the HELLO message, it updates its neighbour piconet table according to the information given in the message.

For route discovery, the sending device S unicasts a RREQ message to PNC I as shown trying to discover D. Upon receiving this RREQ, PNC 1 looks up its NPT table and learns that device D is actually in piconet 2. So PNCI informs PNC2 straightaway, rather than going through the incremental channel inquiries of the first embodiment.

Upon receiving the RREQ from PNC 1, PNC2 knows that there is an incoming connection destined for one of the devices D in its piconet. It builds a beacon and allocates channel time accordingly in piconet 2 for this connection. In the meantime PNC2 sends a response to PNCI indicating that channel time has been allocated for this connection. PNC 1 will then informs S and allocate channel time in piconet 1. This time allocation sequence could also be used for the first embodiment.

This embodiment reduces the communication overhead in discovering D as PNC1 no longer needs to contact all the other PNCs. However it may be less scalable due to the potential large size of the NPT tables when there are many piconets and/or devices.

FIG 6 shows a further schematic illustrating operation of the various devices in the MAC and network layers in the embodiments where a piconet channel based inter- piconet link 108 is used. The sending or requesting device (S) 601 initially carries out the MAC discovery procedure 602 according to the 802.15.3 protocol, which can include sending a MAC layer packet 603 to the PNCI device 610 on the piconet's channel (Ch. 1). The coordinator device 610 for the sending device's piconet (Ch. 1) includes a network layer process 611 for reading the data in the MAC packet, and if this is a simple control command such as the Info Request, and standard response 612 is performed such as sending back the requested information using another MAC packet addressed to the sending device (S) 601.

If this fails, an inter-piconet process 604 is launched within the sending device which forwards a RREQ packet 605 to the PNC 610. Again this is read (611) and the contents determine that the inter-piconet process 613 is required. As described above, this involves forwarding the RREQ to one or more other piconet coordinators (PNCs) on different piconet channels (Ch.2). In one embodiment this can be achieved by stepping through various piconet channels, or a NPT table may be consulted. The RREQ packet 615 is forwarded on the new channel (Ch.2) to a coordinator device (PNC2) 620 for that piconet.

The forwarded RREQ packet 615 is formated as another IEEE8O2.15.3 MAC or data link layer packet, but is sent on a different physical layer (PHY) channel. The packet 615 is received by the coordinator device 620 and the data from this MAC layer packet 615 is read in by a network layer process 621 and determined to be the inter-piconet process 623 which is triggered to determine whether the destination device D is within its piconet.

If the destination device D is within the piconet (Ch.2), the PNC2 620 forwards a new MAC layer request packet 626 to the destination device 630. This is the same physical layer (PHY) or piconet channel (Ch2) but with the destination device (D) address. The device 630 reads the data using a network layer process 631 from the MAC packet 626, determines it refers to the inter-piconet process 632, and responds 634 to its PNC 620 using another MAC layer packet 635. The rest of the procedure proceeds as described above, using analogous MAC and Network layer processes described with respect to Figures 2, 3 and 4.

UWB-based 802.15.3 networks have the potential to support high data rate applications, but have short range transmission limitations. The Child piconet approach in the standard is not flexible and does not fully utilize the channel capacity. On the other hand, range extension in multichannel 802.15.3 networks is not covered in the current standard. The embodiments makes use of the PNC of a piconet as a "switching hub".

This combines the functionalities of MAC layer piconet management and network layer route discovery in the separate (non-piconet channel based) link embodiments.

Involving PNCs in multi-hop route establishment facilitates easier resource management as PNCs are responsible for channel time allocation in 802.15.3 networks.

The protocol also avoids network-wide flooding which would add extra delay and overhead. As a result, the embodiments can be used as a simple, low-cost solution to extending coverage of 802.15.3 networks.

The embodiments additionally offer further advantages. They provide a flexible arrangement in that various routing and channel assignment techniques can be applied according to the trade-off between performance improvement and implementation complexity. For example, traffic load can be taken into account in piconet formation to achieve load balancing and better QoS. When piconet 1 in Figure 2 has a much lighter load than piconet 2, node D can switch to channel 1 and associate with piconet 1.

The embodiments can be usefully combined with route maintenance procedures such as those described in the AODV protocol. This avoids waste of resources, for example, if the link in piconet 1 fails, PNC2 would otherwise be unaware of this and could continue allocating channel times for other hops of the flow. Using the route maintenance approach, when a route breaks, a Route Error (RERR) message is sent to the upstream nodes or devices that traffic needs to be re-routed. PNCs then terminate (release) or re- allocate channel times accordingly. Further, a unique flow ID for the entire flow over multiple hops can be defined. In the original 802.15.3 standard, there is a stream index defined for use only in a single piconet. The new flow ID can replace the old stream index in channel time allocation so that the flow can be identified over multiple piconets.

QoS can also be combined with route discovery. Bandwidth requirements can be incorporated in the RREQ packets and PNCs can perform admission control for flows based on this QoS information and their available resources. For delay-sensitive multimedia traffic such as MPEG-4 encoded video, more sophisticated channel time allocation approaches may be used.

The skilled person will recognise that the above-described apparatus and methods may be embodied as processor control code, for example on a carrier medium such as a disk, CD- or DVD-ROM, programmed memory such as read only memory (Firmware), or on a data carrier such as an optical or electrical signal carrier. For many applications embodiments of the invention will be implemented on a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). Thus the code may comprise conventional programme code or microcode or, for example code for setting up or controlling an ASIC or FPGA. The code may also comprise code for dynamically configuring re-configurable apparatus such as re- programmable logic gate arrays. Similarly the code may comprise code for a hardware description language such as Verilog TM or VHDL (Very high speed integrated circuit Hardware Description Language). As the skilled person will appreciate, the code may be distributed between a plurality of coupled components in communication with one another. Where appropriate, the embodiments may also be implemented using code running on a field-(re)programmable analogue array or similar device in order to configure analogue hardware.

The skilled person will also appreciate that the various embodiments and specific features described with respect to them could be freely combined with the other embodiments or their specifically described features in general accordance with the above teaching. The skilled person will also recognise that various alterations and modifications can be made to specific examples described without departing from the scope of the appended claims.

Claims

CLAIMS: 1. A wireless communications system comprising: a plurality of

piconets each supporting wireless communications amongst a number of wireless devices on a respective piconet channel, each piconet having an associated piconet coordinator device which coordinates use of the respective piconet channel; wherein communications between a sending device in a sending piconet and a destination device in a destination piconet are routed through their respective piconet coordinator devices, the respective piconet coordinator devices communicating with each other using a said piconet channel.
2. A system according to claim I or 2 wherein the devices communicate with each other and their respective coordinator devices using the IEEE8O2. 15.3 protocol.
3. A system according to claim 1 or 2 wherein a said piconet coordinator device is arranged to communicate with the respective sending or destination devices on their respective piconet channel and to communicate with the other piconet coordinator device on the other respective piconet channel in order to route commimications between the sending and destination devices.
4. A system according to claim I or 2 wherein the piconet coordinator devices, the sending device and the destination device are arranged to communicate with the each other on a common respective piconet channel in order to route communications between the sending and destination devices.
5. A system according to claim 4 wherein a said piconet coordinator device is arranged to switch between piconet channels in order to route communications between the sending and destination devices and is further arranged to send channel switching notification messages to the other devices associated with the piconet channel it coordinates.
6. A system according to any one preceding claim wherein the sending device is arranged to send a route request message to the destination device via the piconet coordinator devices associated with the sending and destination devices in order to establish the communications route between the sending and destination devices.
7. A system according to claim 6 wherein the piconet coordinator device associated with the sending device is arranged to sequence through a number of piconet channels until communication with the coordinating device associated with the destination piconet is established.
8. A system according to claim 6 wherein the piconet coordinator device associated with the sending device is arranged to determine from a lookup table the piconet channel associated with the destination device and to establish communication with the coordinating device associated with the destination piconet using the determined piconet channel.
9. A wireless communications system comprising: a plurality of piconets each supporting wireless communications amongst a number of wireless devices on a piconet channel, each piconet having a piconet coordinator device which coordinates use of the respective piconet channel by dividing portions of channel use time amongst the devices; an inter- piconet communications link which couples the piconet coordinator devices together; means for enabling communication between a sending device in a sending piconet and a destination device in a destination piconet using respective intermediate piconet coordinating devices and the interpiconet communications link.
10. A system according to claim 9 wherein said communications between the sending device and the respective coordinator device comprises a MAC layer address for the coordinator device and a network layer address for the destination device.
11. A wireless communication device for communicating with a destination wireless communication device and comprising: means for sending a request for connection to the destination device on a sending piconet channel to a sending piconet coordinator device which coordinates access to the first piconet channel amongst wireless communications device forming the first piconet; means for receiving a response on the first piconet channel from the coordinator device noting another piconet channel to switch to for communicating with destination device; means for sending traffic data for the destination wireless communications device to the sending piconet coordinator wireless communications device using the other piconet channel.
12. A piconet coordinating device comprising: means for coordinating access to a sending piconet channel amongst a number of devices forming a sending piconet; means for receiving a request for connection to a destination device on the sending piconet channel from a sending device, the destination device not being part of the first piconet; means for forwarding the request on a destination piconet channel to a destination piconet coordinating device for a second piconet comprising the destination device; means for receiving a response on the destination piconet channel from the destination piconet coordinating device; means for forwarding the response to the sending device on the sending piconet channel; and means for relaying communications between the sending and destination devices including means for communicating with the destination piconet coordinating device using the destination piconet channel.
13. A method of establishing a communications route between devices using different piconets, the method comprising: sending a route request message from a sending device on a sending piconet for establishing a route with a destination device to a coordinator device for said sending piconet on an associated sending piconet channel; receiving the route request message and forwarding to a coordinator device for a destination piconet associated with the destination device on a destination device channel.
14. A method according to claim 13 further comprising: forwarding the route reply message to the sending piconet coordinating device on the destination piconet channel; forwarding the route reply message to the sending device on the sending piconet channel.
15. A method according to claim 14 wherein the route reply message indicates a piconet channel for the communications route, and wherein the communication route is established using the two coordinator devices which communicate with each other using the indicated piconet channel.
16. A method according to claim 15 wherein the indicated piconet channel is also used for communications between both the sending device and the destination device and their respective coordinator devices.
17. A method according to claim 16 wherein the sending or destination device and/or their respective coordinator device issue channel switching notifications to other devices on their respective piconet channel when switching between their respective piconet channel and the indicated piconet channel in order to route communications between the sending and destination devices.
18. A method of inter-piconet communications between a sending device in a sending piconet having a sending piconet channel and a destination device in a destination piconet having a destination piconet channel, the piconets operating according to the IEEE8O2. 15.3 protocol, and the method comprising: establishing a communications route between the sending and destination devices and respective sending and destination piconet coordinator devices; establishing a communications route between the sending and destination piconet coordinator devices using one of the sending or destination piconet channels.
19. A method according to claim 18 wherein the established communication routes all use the same piconet channel.
20. A processor readable medium carrying processor code comprising instructions which when executed on a processor cause it to carry out a method according to any one of claims 13 to 19.

20. A processor readable medium carrying processor code comprising instructions which when executed on a processor cause it to carry out a method according to any one of claims 13 to 19.

Amendments to the claims have been filed as follows CLAIMS: 1. A wireless communications system comprising: a plurality of piconets each supporting wireless communications amongst a number of wireless devices on a respective piconet channel, each piconet having an associated piconet coordinator device which coordinates use of the respective piconet channel; wherein communications between a sending device in a sending piconet and a destination device in a destination piconet are routed through their respective piconet coordinator devices, the respective piconet coordinator devices communicating with each other using a said piconet channel.

2. A system according to claim 1 wherein the devices communicate with each other and their respective coordinator devices using the IEEE8O2. 15. 3 protocol.

3. A system according to claim 1 or 2 wherein a said piconet coordinator device is arranged to communicate with the respective sending or destination devices on their respective piconet channel and to communicate with the other piconet coordinator device on the other respective piconet channel in order to route communications between the sending and destination devices.

4. A system according to claim 1 or 2 wherein the piconet coordinator devices, the sending device and the destination device are arranged to communicate with each other on a common respective piconet channel in order to route communications between the sending and destination devices.

5. A system according to claim 3 wherein a said piconet coordinator device is arranged to switch between piconet channels in order to route communications between the sending and destination devices and is further arranged to send channel switching notification messages to the other devices associated with the piconet channel it coordinates.

6. A system according to any one preceding claim wherein the sending device is arranged to send a route request message to the destination device via the piconet coordinator devices associated with the sending and destination devices in order to establish the communications route between the sending and destination devices.

7. A system according to claim 6 wherein the piconet coordinator device associated with the sending device is arranged to sequence through a number of piconet channels until communication with the coordinating device associated with the destination piconet is established.

8. A system according to claim 6 wherein the piconet coordinator device associated with the sending device is arranged to determine from a lookup table the piconet channel associated with the destination device and to establish communication with the coordinating device associated with the destination piconet using the determined piconet channel.

9. A wireless communications system comprising: a plurality of piconets each supporting wireless communications amongst a number of wireless devices on a piconet channel, each piconet having a piconet coordinator device which coordinates use of the respective piconet channel by dividing portions of channel use time amongst the devices; an inter- piconet communications link which couples the piconet coordinator devices together; means for enabling communication between a sending device in a sending piconet and a destination device in a destination piconet using respective intermediate piconet coordinating devices and the interpiconet communications link.

10. A system according to claim 9 wherein said communications between the sending device and the respective coordinator device comprises a MAC layer address for the coordinator device and a network layer address for the destination device.

11. A wireless communication device for communicating with a destination wireless communication device and comprising: means for sending a request for coimection to the destination device on a sending piconet channel to a sending piconet coordinator device which coordinates access to the first piconet channel amongst wireless communications device forming the first piconct; means for receiving a response on the first piconet channel from the coordinator device noting another piconet channel to switch to for communicating with destination device; means for sending traffic data for the destination wireless communications device to the sending piconet coordinator wireless communications device using the other piconet channel.

12. A piconet coordinating device comprising: means for coordinating access to a sending piconet channel amongst a number of devices forming a sending piconet; means for receiving a request for connection to a destination device on the sending piconet channel from a sending device, the destination device not being part of the first piconet; means for forwarding the request on a destination piconet channel to a destination piconet coordinating device for a second piconet comprising the destination device; means for receiving a response on the destination piconet channel from the destination piconet coordinating device; means for forwarding the response to the sending device on the sending piconet channel; and means for relaying communications between the sending and destination devices including means for communicating with the destination piconet coordinating device using the destination piconet channel.

13. A method of establishing a communications route between devices using different piconets, the method comprising: sending a route request message from a sending device on a sending piconet for establishing a route with a destination device to a coordinator device for said sending piconet on an associated sending piconet channel; 2-7 receiving the route request message and forwarding to a coordinator device for a destination piconet associated with the destination device on a destination device channel.

14. A method according to claim 13 further comprising: forwarding the route reply message to the sending piconet coordinating device on the destination piconet channel; forwarding the route reply message to the sending device on the sending piconet channel.

15. A method according to claim 14 wherein the route reply message indicates a piconet channel for the communications route, and wherein the communication route is established using the two coordinator devices which communicate with each other using the indicated piconet channel.

16. A method according to claim 15 wherein the indicated piconet channel is also used for communications between both the sending device and the destination device and their respective coordinator devices.

17. A method according to claim 16 wherein the sending or destination device and/or their respective coordinator device issue channel switching notifications to other devices on their respective piconet channel when switching between their respective piconet channel and the indicated piconet channel in order to route communications between the sending and destination devices.

18. A method of inter-piconet communications between a sending device in a sending piconet having a sending piconet channel and a destination device in a destination piconet having a destination piconet channel, the piconets operating according to the JEEE8O2. 15.3 protocol, and the method comprising: establishing a communications route between the sending and destination devices and respective sending and destination piconet coordinator devices; establishing a communications route between the sending and destination piconet coordinator devices using one of the sending or destination piconet channels.

19. A method according to claim 18 wherein the established communication routes all use the same piconet channel.