Channel estimation and detection for digital communication systems

Claim 3

A method according to claim 1 wherein the m second vectors selected are those which have the lowest distance quantities as derived from the received sample and one of j stored predictions of the channel for the current sample instant.

Claim 4

A method according to claim 1 wherein the costs associated with each respective second vector are determined from the received sample, a stored cost associated with the first vector from which the second vector is derived and one of the stored predictions of the channel for the current sample instant.

Claim 5

A method according to claim 1 wherein the earliest component of each of the k second vectors is omitted before storage.

Claim 6

A method according to claim 1 wherein each received sample represents more than one data symbol.

Claim 7

A method according to claim 1 wherein each sample represents one data symbol only and one data symbol only is added to each first vector in expanding the first vectors into second vectors.

Claim 8

A method according to claim 1 for use when no intersymbol interference is expected wherein the number of predictions j is equal to the number of stored vectors k and each prediction is associated with a respective stored vector and its cost.

Claim 9

A method according to claim 7 wherein each new prediction to be associated with a new stored vector is derived from the current sample, an estimate thereof, and the stored prediction of the channel for that sample, associated with the stored vector from which the new vector is derived.

Claim 10

A method according to claim 1 wherein the number m of second vectors expanded from each first vector varies with each first vector, the lower the cost associated with a first vector, the higher the number of second vectors derived from that first vector.

Claim 11

A method according to claim 1 wherein each possible data symbol is used in expanding each first vector to provide vectors from which the m second vectors are selected.

Claim 12

A method according to claim 1 wherein the detected data symbol is the earliest component of that second vector which has the lowest cost.

Claim 13

A method according to claim 1 wherein the k second vectors are selected by firstly selecting all those second vectors which include the detected data symbols, and secondly selecting from the vectors so selected those with lowest costs.

Claim 14

A method according to claim 1 wherein each new channel prediction for the next sample instant is formed from an error between the current sample and a respective one of the j stored predictions of the channel for the current sample.

Claim 15

Apparatus for channel estimation and detection at a receiver comprising: means for receiving over a communication channel a digital sample which is dependent on one or more of the most recently transmitted data symbols, storage means for storing a first number k of first vectors, each representing a different possible received sequence of a second number n of data symbols by means of n components, means for expanding each of a third number k of stored first vectors into a fourth number m of second vectors by adding for each of possible second vectors a further component representing a respective combination of data symbols which could be received at that sample instant and selecting as the m second vectors those of the possible vectors which represent the data symbol sequences most likely to have been received as derived from the received sample and one of j stored predictions of the channel for the current sample instant, means for determining costs, of a type where a lower cost is indicative of a higher likelihood that sequences are correct, associated with each respective second vector, means for selecting that combination of data symbols represented by one component of a second vector having a relatively low cost as the detected data symbol, means for selecting k second vectors with relatively low cost, and for passing the selected vectors to the storage means, the storage means also being arranged to receive and store the costs associated with each stored vector, and means for forming and storing j new predictions of the channel for the next sample instant, the new predictions representing the attenuation and phase change introduced into the signal by the channel, each new prediction being formed using the current sample, and a respective one of the j stored predictions of the channel for the current sample instant, each of the said means being arranged to carry out its function at each of a series of sample instants.

Claim 16

Apparatus for channel estimation and detection at a receiver comprising: means for receiving over a communication channel a digital sample which is dependent on one or more of the most recently transmitted data symbols, storage means for storing a first number k of first vectors, each representing a different possible received sequence of a second number n of data symbols by means of n components, means for expanding each of a third number k of stored first vectors into a fourth number m of second vectors by adding for each of possible second vectors a further component representing a respective combination of data symbols which could be received at that sample instant and selecting as the m second vectors those of the possible vectors which represent the data symbol sequences most likely to have been received as derived from the received sample and one of j stored predictions of the channel for the current sample instant, means for determining costs, of a type where a lower cost is indicative of a higher likelihood that sequences are correct, associated with each respective second vector, means for selecting that combination of data symbols represented by one component of a second vector having a relatively low cost as the detected data symbol, means for selecting k second vectors with relatively low cost, and for passing the selected vectors to the storage means, the storage means also being arranged to receive and store the costs associated with each stored vector, and means for forming and storing j new predictions of the channel for the next sample instant, the new predictions representing the attenuation and phase change introduced into the signal by the channel, each new prediction being formed using the current sample, and a respective one of the j stored predictions of the channel for the current sample instant, each of the said means being arranged to carry out its function at each of a series of sample instants.

Claim 17

Apparatus according to claim 14 wherein the means for expanding each of the k first vectors is arranged to select the m second vectors which have the lowest distance quantities as derived from the received sample and one of j stored predictions of the channel for the current sample instant.

Claim 18

Apparatus according to claim 14 wherein the means for determining costs determines the costs associated with each respective second vector from the received sample, a stored cost associated with the first vector from which the second vector is derived and one of the stored predictions of the channel for the current sample instant.

Claim 19

Apparatus according to claim 14 wherein the means for selecting k second vectors is arranged to omit the earliest component of each of the k second vectors before passing the second vectors to the storage means.

Claim 20

Apparatus according to claim 14 wherein at least some of the said means are in the form of a programmed computer.