Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1999-06-17
2003-04-22
Trost, William (Department: 2683)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S328000, C370S336000, C370S337000, C370S345000, C455S445000, C455S422100, C455S517000
Reexamination Certificate
active
06553020
ABSTRACT:
The present invention relates to a communications system and method.
There is an increasing demand for high bandwidth communications systems which can carry data at rates which are significantly higher than those which are presently available to business or residential users. Systems which would benefit from very high data transfer rates include video-on-demand, video conferencing and video “telephony”, business and home Internet access, local area networks (LAN) interconnects, virtual private networks, teleworking, on-line games, high definition television, and many other applications demanding high information transfer rates.
In a conventional telephone communications system, the system operator's main switched trunk network is connected to an access network which connects the trunk network to a subscriber's individual telephone handset or private branch exchange (PBX). The access network is often known as the “local loop”.
The vast majority of local loop networks in the United Kingdom and many other countries are based on wires which are either buried in the ground or are suspended overhead from poles. The wire extends from the regional access switch to the subscriber and is essentially dedicated to one subscriber and carries signals for no-one else.
Copper wire has conventionally been used primarily because of its relative low cost. However, copper wire can only carry data at a rate of about 2,400 to 9,600 bits per second (bps) without data compression. With more sophisticated techniques, this limit has been increased to about 57,000 bps. However, this is extremely slow when compared with the rate required for real-time video, which is in the region of 2 to 9 million bps (Mbps).
Some UK operators are now offering digital access services using the integrated services digital network (ISDN) system. However, the data transfer rate is still only about 64,000 to 128,000 bps and ISDN or ISDN
2
and wired technology is still used. More recently, wired systems such as HDSL (high speed digital subscriber line) and ADSL (asymmetric digital subscriber line) can deliver up to 2,000,000 bps (2Mbps). However, as these are still wired systems, there is a very substantial start-up cost for any such system in that the operator must incur the significant cost of digging up roads, pavements, etc. to lay the cables or wires to a large number of subscribers before the system can begin operating. Indeed, the operator must take a large financial risk when setting up a new wired system in that the operator must lay a very large number of cables or wires before potential customers have committed themselves to the system so that the operator can offer a system which is already functional. This is obviously a significant risk, particularly where new technology is involved and the level of customer take-up of the system is unknown at the time the operator installs the infrastructure for the system.
Similarly, in a conventional, point-to-multipoint (broadcast) cellular system, each subscriber unit deals only with information intended for that subscriber.
Both the standard telephone system and cellular system mentioned above require some form of central station sending information to and receiving information from outlying or peripheral subscriber stations.
A wireless system is very much cheaper to install as no mechanical digging or laying of cables or wires is required. User sites can be installed and de-installed very quickly. Thus, radio communications systems have many attractive features in the area of large-scale system deployment. However, it is a feature of radio systems when a large bandwidth (data transfer rate) is required that, as the bandwidth which can be given to each user increases, it is necessary or the bandwidth of the radio signals to be similarly increased. Furthermore, the frequencies which can be used for radio transmission are closely regulated and it is a fact that only at microwave frequencies (i.e. in the gigahertz (GHz) region) or higher are such large bandwidths now available as the lower radio frequencies have already been allowed.
The problem with microwave or higher frequencies is that these radio frequencies are increasingly attenuated or completely blocked by obstructions such as buildings, vehicles, trees, etc. Such obstructions do not significantly attenuate signals in the megahertz (MHz) band but becomes a serious problem in the gigahertz (GHz) band. Thus, conventional wisdom has been that microwave or higher frequencies are difficult to use in a public access network which provides communication with a large number of distributed users.
The spectral efficiency of any wireless communications system is extremely important as there are many demands on radio bandwidth. As a matter of practice, the regulatory and licensing authorities are only able to license relatively narrow regions of the radio spectrum. A cellular system, which uses point-to-multipoint broadcasts, places high demands on the radio spectrum in order to provide users with a satisfactory bandwidth and is therefore not very efficient spectrally.
The use of repeaters or relays to pass on data from one station to another is well known in many applications. However, in each case, such repeaters broadcast signals, in a point-to-multipoint manner, and are therefore similar to a cellular approach and suffer from a corresponding lack of spectral efficiency.
According to a first aspect of the present invention, there is provided a communication system, the system comprising: a plurality of nodes, each node having: receiving means for receiving a signal transmitted by wireless transmitting means; transmitting means for wireless transmission of a signal; and, means for determining if a signal received by said node includes information for another node and causing a signal including said information to be transmitted by said transmitting means to another node if said received signal includes information for another node; each node having one or more substantially unidirectional point-to-point wireless transmission links, each of said links being to one other node only, at least some of the nodes being the origination and termination point of user traffic.
According to a second aspect of the present invention, there is provided a communications system, the system comprising: a plurality of nodes, each node having: receiving means for receiving a signal transmitted by wireless transmitting means; transmitting means for wireless transmission of a signal; and, means for determining if a signal received by said node includes information for another node and causing a signal including said information to be transmitted by said transmitting means to another node if said received signal includes information for another node; each node having one or more substantially unidirectional point-to-point wireless transmission links, each of said links being to one other node only, and being arranged such that transmission or reception of a signal at any particular frequency by the node takes place on only one link at a time.
According to a third aspect of the present invention, there is provided a communications system, the system comprising: a plurality of nodes, each node having: receiving means for receiving a signal transmitted by wireless transmitting means; transmitting means for wireless transmission of a signal; and, means for determining if a signal received by said node includes information for another node and causing a signal including said information to be transmitted by said transmitting means to another node if said received signal includes information for another node; each node having one or more substantially unidirectional point-to-point wireless transmission lines, each of said links being to one other node only, the links being arranged such that at least some of the nodes are not linked only to the nearest neighbour node(s).
Wireless transmission is used to provide communication with each node. In practice, each node is likely to be equipment associated with a user of or subscriber to the system.
Hughes Philip T.
Jackson Timothy
Newman James
Ferguson Keith
Pillsbury & Winthrop LLP
Radiant Networks PLC
Trost William
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