CHANNEL ESTIMATION FOR RAPID DISPERSIVE FADING CHANNELS
First Claim
1. A method of channel estimation and data detection for transmissions over a multipath channel, comprising the following steps:
- receiving a transmission over a communications channel, wherein the transmission comprises a series of frames wherein each frame comprises a series of blocks of information data, or symbols, wherein each symbol is divided into multiple samples which are transmitted in parallel using multiple subcarriers, and wherein pilot tones are inserted into each symbol to assist in channel estimation and data detection;
I decoding a symbol of the received transmission by retrieving pilot tones from it and using these to estimate variations in the channel frequency response using an iterative maximum likelihood channel estimation process, in which the estimation process comprises the following steps;
in a first iteration, deriving soft decoded data information, that is information having a confidence value or reliability associated with it, from the estimates of the channel frequency response for the symbol obtained from pilot tones;
and, in at least a second iteration using the soft decoded data information as virtual pilot tones together with the pilot tones to re-estimate the channel frequency response for the symbol.
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Abstract
This invention addresses the problem of channel estimation in fast fading communications channels, particularly for OFDM systems. It finds wide application in existing and future systems such as WLAN and WiMax. In particular, the invention involves a method of channel estimation and data detection for rapid dispersive fading channels due to high mobility. The invention involves decoding a symbol of the received transmission by retrieving pilot tones from it and using these to estimate variations in the channel frequency response using an iterative maximum likelihood channel estimation process, in which the estimation process comprises the following steps: In a first iteration, deriving soft decoded data information, that is information having a confidence value or reliability associated with it, from the estimates of the channel frequency response for the symbol obtained from pilot tones. And, in at least a second iteration using the soft decoded data information as virtual pilot tones together with the pilot tones to re-estimate the channel frequency response for the symbol. In other aspects the invention concerns a receiver and software designed to perform the method.
84 Citations
20 Claims
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1. A method of channel estimation and data detection for transmissions over a multipath channel, comprising the following steps:
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receiving a transmission over a communications channel, wherein the transmission comprises a series of frames wherein each frame comprises a series of blocks of information data, or symbols, wherein each symbol is divided into multiple samples which are transmitted in parallel using multiple subcarriers, and wherein pilot tones are inserted into each symbol to assist in channel estimation and data detection;
I decoding a symbol of the received transmission by retrieving pilot tones from it and using these to estimate variations in the channel frequency response using an iterative maximum likelihood channel estimation process, in which the estimation process comprises the following steps;in a first iteration, deriving soft decoded data information, that is information having a confidence value or reliability associated with it, from the estimates of the channel frequency response for the symbol obtained from pilot tones; and, in at least a second iteration using the soft decoded data information as virtual pilot tones together with the pilot tones to re-estimate the channel frequency response for the symbol. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20)
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19. A receiver able to estimate channel variation and detect data received over a multipath channel, the receiver comprising:
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a reception port to receive a transmission over a communications channel, wherein the transmission comprises a series of frames wherein each frame comprises a series of blocks of information data, or symbols, wherein each symbol is divided into multiple samples which are transmitted in parallel using multiple subcarriers, and wherein pilot tones are inserted into each symbol to assist in channel estimation and data detection; a decoding processor to decode a symbol of the received transmission by retrieving pilot tones from it and using these to estimate variations in the channel frequency response using an iterative maximum likelihood channel estimation process, in which the processor performs the estimation process comprises the following steps; in a first iteration, deriving soft decoded data information, that is information having a confidence value or reliability associated with it, from the estimates of the channel frequency response for the symbol obtained from pilot tones; and, in at least a second iteration using the soft decoded data information as virtual pilot tones together with the pilot tones to re-estimate the channel frequency response for the frame.
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Specification