GB2324006A

GB2324006A - Electronic modulation scheme

Info

Publication number: GB2324006A
Application number: GB9706664A
Authority: GB
Inventors: David Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-04-02
Filing date: 1997-04-02
Publication date: 1998-10-07
Anticipated expiration: 2017-04-02
Also published as: GB2324006B; GB9706664D0

Abstract

An electronic modulation scheme comprising a set of possible components, (frequencies, amplitudes, phases), for example as in fig 1 a set of 8 different frequencies, in which a group of symbols is made up by combinations of half the number of available frequencies, in this example always transmitting 4 frequencies. Each symbol is made by combining the same number of components. For this example 70 symbols are possible, that is the number of combinations of 4 out of 8 possibilities.

Description

Electronic Modulation Scheme Information can be transmitted to a receiver by assigning a meaning to the symbols sent, for example the meaning may be a group of digital bits, and the symbol a particular frequency transmitted for a given time.

Electronic equipment can be used to generate and detect different frequencies, phases and amplitudes for use as components ofthe symbol.

By selecting a set of possible components, for example as in fig 1 a set of 8 different frequencies, a group of symbols is made up by combinations of half the number of available components, in this example always transmitting 4 frequencies, an example of one symbol is shown in figure 2. Each symbol is made by combining the same number of components. For this example 70 symbols are possible that is the number of combinations of4 out of8 possibilities.

In the case of a set of possible components having an odd total number of components each symbol is made up of a combination of half the number of available components rounded down to the nearest integer.

The number of component generators required is found from the number of possible components chosen, where X represents the total number of possible components, the number of component generators is X/2 if X is even or (X-l)/2 if X is odd.

The total number of possible symbols is found from:

for X even and

for X odd.

where ! means factorial.

The choice of the set of components is made to ensure any combination of half the total number may be generated and detected without ambiguity with other combinations or no symbol being present. The transmitter is able to generate simultaneously any combination of half the total number of possible components and the receiver can detect which have been transmitted.

A second example is shown in Figs 3 and 4, Fig 3 shows the set of 6 possible components using different amplitudes only. Fig 4 shows one possible symbol as the combination of 3 amplitudes. The component amplitudes are chosen so that the result of combining any 3 is different from the result of combining any other 3, there are 20 different symbols for this example. In the example this is achieved using amplitudes with ratiosof.- 1,2,4,8, 16 and 32.

A third example is shown in Figs 5 and 6, Fig 5 shows the set of 5 possible components using different phases of a single frequency, represented as vectors, the phases of the components are separated by 72" and their amplitudes are the same. Fig 6 shows one possible symbol as the combination of 2 of the components, there are 10 different symbols for this example.

The connection of an example of the modulation scheme is shown in Fig 7. In the transmitter the data to symbol converter takes a group of digital bits and decides which of the possible symbols to transmit. The converter sends instructions to the component generators for that symbol, the components are then combined and passed across the medium through interfaces. In the receiver the demodulator converts the symbol to a signal indicating which components are present and the component to data converter recovers and outputs the original data. For this example the set of components is as shown in Fig 1, the number of component generators is 4. The number of bits in a group is 6, because 6 bits has 64 different combinations of logical is or Os and this is the largest number that gives a number of combinations less than or equal to the number of symbols that can be generated. The relation between a symbol and it's meaning as a group of bits is illustrated by an example listing shown in fig 8 and fig 2 corresponds to the group of bits 010000.

Claims

1. An electronic modulation scheme comprising a set of possible components to make up a symbol, a group of symbols is made up by combinations of half the number of available components. Each symbol is made by combining the same number of components.

2. An electronic modulation scheme as claimed in claim 1 for the case of a set of possible components having an odd total number of possible components the group of symbols is made up of a combination of half the number of available components rounded down to the nearest integer.

Amendments to the claims have been filed as follows 1. An electronic modulation scheme comprising a set of possible phase components to make up a symbol, a group of symbols is made up by combinations of half the number of available components. Each symbol is made by combining the same number of còmponents. The set of possible phase components comprises 8 different phases of the same carrier frequency.