Space Time Coded Mb-Ofdm Uwb System

• US 20080247483A1
• Filed: 09/22/2006
• Published: 10/09/2008
• Est. Priority Date: 09/23/2005
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Seyedi-Esfahani, Seyed-Alireza
• Granted Patent: US 8,149,943 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 1/71635 Transmitter aspects H04B1/7174 takes precedence
• CPC Class Codes: H04L 1/0668 Orthogonal systems, e.g. using Alamouti codes
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A system, apparatus, and method is provided for space-time coding a multiband OFDM UWB system that employs a scheme that transmits channel symbols corresponding to an incoming signal on the same sub-carrier (204.i 206.i) of different antennas (202.1 202.2).

Claims

1. An MB OFDM system comprising:

a coder (201.1), responsive to a stream of at least one incoming symbol, to form therefrom a set including a plurality of channel symbols (203.ij) that correspond to each at least one incoming symbol, such that the channel symbols (203.ij) that correspond to each at least one incoming symbol include the incoming symbol, the negative of the incoming symbol, the complex conjugate of an incoming symbol, and a negative of a complex conjugate of an incoming symbol;

a plurality of antennas (202.i);

an output stage (201.2) configured to;

a. when two of the channel symbols (203.ij) are complex conjugates of one another, the output stage is further configured to;

i. transform one of the two channel symbols as the output of a single IFFT and the other of the two channel symbols by a reversal of the index of the output;

ii. create OFDM symbols from the transformed symbols using an IFFT such that the two transformed OFDM symbols are copies of each other with inversed indices; and

otherwise, translate the channel symbols to a time domain,

wherein the stream of channel symbols is translated to OFDM symbols; and

b. apply the OFDM symbols to the plurality of antennas (202.i) to form a plurality of distinct channels (024 206) over a transmit medium such that a subset of the plurality of OFDM symbols that correspond to an incoming symbol are simultaneously transmitted on the same subcarrier (204.i) (206.i) of a different channel (204) (206) of said plurality of distinct channels (204) (206) by a different antenna (202.1) (202.2) of said plurality (202.i); and

a receiver having a single antenna that is adapted to receive and decode signals transmitted by the output stage, wherein the stream is space-time coded for transmission.

2. The system of claim 1, further comprising a receiver having a single antenna that is adapted to receive and decode signals transmitted by the output stage.

3. The system of claim 1, wherein the plurality of distinct channels direct transmissions therefrom to a single receiver antenna.

4. The system of claim 1, wherein the coder encodes incoming symbols in blocks of n channel symbols.

5. The system of claim 1, wherein:

the coder encodes incoming symbols in blocks of 2 channel symbols such that each block of 2 channel symbols {s₀ s₁} is encoded into a first sequence of 2 symbols {s₀, −

s₁*} and into a second sequence of 2 channel symbols {s₁,s₀*)}, where s_i* is the complex conjugate of s_i;

the plurality of antennas consists of a first antenna and a second antenna; and

the output stage applies the first sequence to the first antenna and the second sequence to the second antenna.

6. An MB OFDM transmitter (201) comprising:

a coder (201.1), responsive to a stream of at least one incoming symbol, for forming therefrom a set including a plurality of channel symbols (203.ij) that correspond to each at least one incoming symbol such that the channel symbols (203.ij) that correspond to each at least one incoming symbol include the incoming symbol, the negative of the incoming symbol, the complex conjugate of an incoming symbol, and a negative of a complex conjugate of an incoming symbol;

a plurality of antennas (202.i);

an output stage (201.2) to;

a. when two of the channel symbols (203.ij) are complex conjugates of one another, the output stage is further configured to;

i. transform one of the two channel symbols as the output of a single IFFT and the other of the two channel symbols by a reversal of the index of the output; and

ii. create OFDM symbols from the transformed symbols using an IFFT such that the two transformed OFDM symbols are copies of each other with inversed indices; and

otherwise, translate the channel symbols to a time domain,

wherein the stream of channel symbols is translated to OFDM symbols; and

b. applies the OFDM symbols to the plurality of antennas (202.i) to form a plurality of distinct channels (024 206) over a transmit medium such that a subset of the plurality of OFDM symbols that correspond to an incoming symbol are simultaneously transmitted on the same subcarrier (204.i) (206.i) of a different channel (204) (206) of said plurality of distinct channels (204) (206) by a different antenna (202.1) (202.2) of said plurality (202.i); and

a receiver having a single antenna that is adapted to receive and decode signals transmitted by the output stage, wherein the stream is space-time coded for transmission.

7. A method for transmitting over transmission medium information corresponding to a plurality of incoming symbols, comprising the steps of:

encoding the plurality of incoming symbols in at least one block of n symbols, to form n*m channel symbols, where m is a number of distinct space diverse channels 203.ij over which said symbols are transmitted, wherein said encoding generates a plurality of channel symbols (203.ij) that correspond to each of said plurality of incoming symbols such that the plurality of channel symbols (203.ij) includes an incoming symbol, the negative of the incoming symbol, the complex conjugate of the incoming symbol, and a negative of a complex conjugate of the incoming symbol;

when two of the channel symbols are complex conjugates of one another, replacing one of the two channel symbols with the output of a single IFFT and the other of the two channel symbols with a symbol obtained by reversing the index of the output; and

creating OFDM symbols from the channel symbols using an IFFT such that the OFDM symbols corresponding to complex conjugates in the incoming symbols are copies of each other with inversed indices; and

transmitting said n*m channel symbols over said m channels so that each incoming symbol has a corresponding channel symbol in the same subcarrier (204.i) (206.i) of said m channels.

8. The method of claim 7, further comprising the step of a receiver (205) having a single antenna performing the steps of:

receiving the transmitted n*m channel symbols; and

decoding the received n*m channel symbols.

9. The method of claim 8, wherein

n=m-2;

the encoding step further comprises the step of encoding the incoming symbols in blocks of 2 channel symbols such that each block of 2 channel symbols {s₀s₁} is encoded into a first sequence of 2 channel symbols {s₀,−

s₁*} and into a second sequence of 2 channel symbols {s₁,s₀*}, where s_i* is the complex conjugate of si; and

the transmitting step further comprises the step of applying the first sequence to a first channel and the second sequence to a second channel.