Metrics Calculations Utilising Pre-Stored Values
AssigneeTTP Com Limited
InventorCyril Valadon
Life of this patent
Estimating the term…
Abstract
The trellis processing apparatus and method achieve a reduced computational structure when implementing a DDFSE-like branch metrics calculation by pre-storing computed values, which can be re-used.
Claims9
Trellis processing apparatus for estimating a transmitted signal from a received signal acquired through a channel, wherein the received signal comprises a sequence of received symbols, the transmitted signal comprises a sequence of transmitted symbols, the channel is characterised by a channel response estimate comprising a series of channel coefficients each corresponding to a different time delay and the apparatus comprises:
- a memory containing differences between a received symbol and different products, each product being a product of the channel coefficient corresponding to the least time delay and a different one of the possible transmitted symbols;
- a processor for calculating a summation of products, each product being a product of a possible transmitted signal symbol and a channel coefficient other than the one corresponding to the least time delay and the summation being specific to a branch-start state in a trellis;
- and wherein the processor is arranged to combine the result of the summation with different differences from the memorv means in the calculation of branch metrics leading to different branch-end states in the trellis.
Trellis processing apparatus for calculating branch metrics in a reduced state trellis comprising a processor adapted to pre-calculate for a trellis state a sum of products of channel coefficient values and signal symbol values corresponding to at least the oldest part of the section of the channel that is not hypothesised by the state such that the sum can be re-used in calculating branch metrics for different trellis branches leading out of different states and further comprising a memorv for storing the products.
A trellis processing method for estimating a transmitted signal from a received signal acquired through a channel, wherein the received signal comprises a sequence of received symbols, the transmitted signal comprises a sequence of transmitted symbols, the channel is characterised by a channel response estimate comprising a series of channel coefficients each corresponding to a different time delay and the method comprises:
- storing a group of differences between a received symbol and different products, each product being a product of the channel coefficient corresponding to the least time delay and a different one of the possible transmitted symbols;
- a calculating step comprising calculating a summation of products, each product being a product of a possible transmitted signal symbol and a channel coefficient other than the one corresponding to the least time delay and the summation being specific to a branch-start state in a trellis;
- and wherein the calculating step further comprises combining the result of the summation with different differences from said stored group in the calculation of branch metrics leading to different branch-end states in the trellis.
A trellis processing method for calculating branch metrics in a reduced state trellis comprising precalculating for a trellis state a sum of products of channel coefficient values and signal symbol values corresponding to at least the oldest part of the section of the channel that is not hypothesised by the state such that the sum can be re-used in calculating branch metrics for different trellis branches leading out of different states and storing the products in a memory.
Dependencies are inferred from the claim text.