Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-12-02
2001-10-09
Yao, Kwang B. (Department: 2664)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S437000, C370S461000
Reexamination Certificate
active
06301243
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for transmitting items of information from a plurality of data sources to a data destination over a common data channel.
DESCRIPTION OF THE PRIOR ART
An example of a system of this type is an interactive home entertainment games console. A number of players are each provided with a handset. Each player presses buttons on their respective handset, causing the handset to generate game-play data which is transmitted via an infra-red link to a central game controller.
Since all handsets are transmitting over a common infra-red data channel it is necessary to multiplex the data from the different handsets. Conventionally this is achieved by time division multiplexing in which each handset transmits data in a defined time slot. A problem with time division multiplexing is that the handsets must be synchronised under control of the central game controller to ensure that only one handset is transmitting at any one time. This requires a two-way link between the handsets and the central game controller, along with additional computing power to provide synchronisation control. As a result the system can be expensive.
U.S. Pat. No. 4,924,216 describes joy stick controller apparatus in which a pair of joy stick controllers may send signal bursts on the same communication channel in the infra-red frequency range by means of an electromagnetic transmission. One joy stick transmits signals having a duration of T0 and a repetition period of T1 while the second joy stick transmits a signal having a duration equal to T0 and a repetition period of T2 where T2 is selected to be at least two T0 greater than T1, at least four times greater than T0 and less than 16.6 milliseconds. This approach is suitable where a simple video game apparatus is concerned but is not suitable more generally in the field of broadcast media control and game playing which involve much more complex signalling arrangements and usually more than two data sources.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention there is provided a method of transmitting items of information from a plurality of data sources to a data destination over a common data channel, the method comprising:
transmitting the items of information from each data source to the data destination as a series of data packets, each data packet being separated from successive data packets transmitted by the same data source by a repetition period, the repetition period of each data source being different from the repetition periods of the other data sources; and
repeatedly transmitting each item of information from the same data source in at least N adjacent data packets, where N is the number of data sources, in order to ensure that at least one of the N adjacent data packets is received at the data destination without overlapping with data packets from the other data sources, wherein
Period
n=
2*burst period*[(
N−
1)
2
+n]
where Period n is the repetition period of the nth data source and burst period is a parameter related to the length of the data packets.
In accordance with a second aspect of the present invention there is provided communication apparatus comprising a data destination having a receiver for receiving data transmitted over a common data channel; and a plurality of data sources each comprising:
a) a transmitter for transmitting items of information to the data destination over the common data channel; and
b) a processor for controlling the transmitter such that the transmitter transmits the items of information as a series of data packets, each data packet being separated from successive data packets transmitted by the same data source by a repetition period, and each item of information being transmitted in at least N adjacent data packets from the same data source, where N is the number of data sources,
wherein the repetition period of each data source is different from the repetition periods of the other data sources, and wherein
Period
n=
2*burst period*[(
N−
1)
2
+n]
where Period n is the repetition period of the nth data source and burst period is a parameter related to the length of the data packets.
The present invention provides a particularly convenient method of multiplexing without requiring any two-way communication or synchronisation between the data sources and the data destination. The system is also robust and can cope with drift in the repetition periods of the data sources without significantly affecting the reliability of transmission. As a result much cheaper components can be used than in previous systems.
The repetition period is typically defined by the time between the start of two successive data packets. Depending on the coding scheme the data packets may always have the same length or may have a length which varies in accordance with the amount of information being transmitted by the data packet. However in both cases each data source typically has a predetermined maximum data packet length, ie. a limited time slot in which the data source is permitted to transmit data.
Each data source may have different maximum data packet lengths. For instance the data source with the shortest repetition period may have a shorter maximum data packet length (and hence each data packet transmits less data) than the data source with the longest repetition period. However preferably each data source has the same maximum data packet length.
Each item of information may be repeated over more than N data packets. However preferably each item of information is transmitted from the same data source in N data packets in order to optimise the data rate.
One or more of the data sources may have a repetition period which varies during the transmission of the N successive data packets. However preferably each data source has a repetition period which remains substantially constant (apart from the effect of drift) at least during the transmission of the N successive data packets, and preferably at all times.
The repetition periods of the data sources may be unequally spaced. For example four data sources may be provided with repetition periods of 20 ms,22 ms,26 ms, and 28 ms. However in a preferred example the repetition periods of the data sources are equally spaced.
In this invention, the difference in repetition period between any two data sources is great enough so that if overlap occurs between two data packets, it will not occur between the same two data sources on the next two data packets. Also, the difference in repetition period between any two data sources is small enough that if the data packets from two handsets overlap once they will not overlap again for at least another N repetition periods.
The method may be employed in any communication system which transmits data from a number of sources over a common data channel.
The invention can be implemented to transmit items of information to a variety of data destinations. However, the invention is particularly suited to a method of controlling a broadcast media receiving system, the method comprising transmitting control items of information to the broadcast media receiving system using a method according to the first aspect of the invention.
The invention also provides broadcast media receiving apparatus comprising a broadcast media receiving system; and communication apparatus according to the second aspect of the invention for controlling the broadcast media receiving system.
The broadcast media receiving system may comprise an analogue and/or digital broadcast media receiving system and will typically include a set top box (STB) or an integrated TV or video cassette recorder (VCR) which in one example is controlled by items of information supplied from the data sources. These data sources typically comprise remote control apparatus.
For example, each data source could comprise a remote control including a plurality of input buttons representing numbers, channels, TV operations, VCR operations, and/or STB operati
Copper Andrew James
Johnson Andrew
Walton Anthony Stephen
Weston David Robert
Woodfield David Alan
Price and Gess
Two Way TV Limited
Yao Kwang B.
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