Patent Application
20080081652
Some methods and embodiments in accordance with the present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:
a) and (b) schematically illustrates another communications system in accordance with the invention.
With reference to
Users tend to cluster into communicating groups or “bubbles”. When a bubble has access to the Internet (IP) “cloud”, it announces its presence via a shared database. The shared database is used for low speed purposes such as to aid in discovery for handover purposes, inter-bubble power-control feedback and channel use negotiation. When a bubble has no access to the IP cloud, its presence is unknown to other/users and it is termed “unannounced”. In the system shown in
To instigate user discovery, the isolated user 1 deliberately transmits a signal intended to produce interference at any bubbles that may exist in range of the signal, and thus attempts to announce its presence to unknown nodes included in the bubbles. The transmit band supported by the isolated node 1 implicitly alerts only those nodes that are listening on that band. By way of explanation,
The isolated user 1 repeatedly passes through the transmit band, transmitting a narrow band signal at different frequencies fl to fin, as illustrated in
Additionally, each pass through the transmit band by the isolated user 1 is of a higher transmit power than the previous one, as illustrated in
Furthermore, as shown in
A bubble may be described as “hearing” an isolated user when one or more of the users in the communicating bubble detects the isolated user's presence. The detection may be achieved, for example, by detecting a periodic spike in the receive channel of a node.
In the example shown in
Node 6′ detects the presence of the isolated user 1 and transmits the information to the node 6″ to which it is connected, and which has a more direct connection with the network 2. The node 6″ then sends a response to the isolated user 1 and a first link is established between them when the isolated user 1 receives the response. In addition, the node 5′ also establishes a second link with the isolated user 1. The node 6″ is a licensed user, enabling it to make use of a licensed part of the wireless spectrum when communicating with the network 2.
The initial links enable radio capabilities and service requirements to be exchanged between the isolated user 1 and the nodes 5′ and 6″. The nodes 5′ and 6″ coordinate their shared access of the isolated user 1 interference bands via the IP cloud 2. A standardized protocol coupled with an air interface physical layer of low computational complexity forms the initial communication link, for example, convolution FEC with BPSK modulation. This low-bit rate duplex link is used to communicate the radio capabilities of the isolated user 1 and for the nodes 5′ and 6″ to respond with a service offer.
The next stage in the bid-offer process, is for the isolated user 1 to establish a more suitable communication link to replace the initial link using a bid-offer procedure. On acceptance of the offer, the isolated user 1 becomes a full member of the announced bubble to which the successful node belongs. Then, the isolated user 1 establishes full communication links with other members of the bubble, adapting to their physical layer parameters and medium access control.
In the case of a simplex radio it is not possible to listen and transmit simultaneously. To cater for this, the isolated node's transmission and reception is time interleaved in a well-defined manner. Upon successful interference injection, the alerted node knows the time of occurrence, the frequency band of occurrence and from the content of the signal received, the isolated node's RX capability. Using this information and a well-defined protocol which describes the interleave pattern, the alerted node can calculate when the isolated node will be listening on each frequency band. The alerted node can then schedule its response.
With reference to
The present invention may be embodied in other specific forms, and implemented by other methods, without departing from its spirit or essential characteristics. The described embodiments and methods are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
