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Wireless communication apparatus

a wireless communication and wireless communication technology, applied in multiplex communication, orthogonal multiplex, baseband system details, etc., can solve problems such as difficulty in performing automatic gain control (agc)

Inactive Publication Date: 2008-08-28
TAKEDA DAISUKE +5
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0011]It is another object of the present invention to make accurate channel estimation by known symbols possible.
[0012]It is still another object of the present invention to allow the receiving side to readily estimate the number of antennas used in transmission without adding any extra information to a preamble, thereby making correct demodulation of data symbols feasible.

Problems solved by technology

On the other hand, if the power of received signals largely fluctuates in a receiver because the number of antennas used in transmission changes, it becomes difficult to perform automatic gain control (AGC) by which the input signal level of an analog-to-digital converter (ADC) for converting a received signal into a digital signal is controlled within the dynamic range of this ADC.

Method used

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first embodiment

[0032]First, a transmitter according to a first embodiment of the present invention will be described below with reference to FIG. 1. FIG. 1 shows physical layers of this transmitter. Data (a bit stream) 10 is transmitted in certain transmission units (e.g., frames or packets) from an upper layer. An encoder 11 performs, e.g., error correction coding on the input data 10, and generates a coded bit sequence. A serial-to-parallel (S / P) converter 12 divides the coded bit sequence into a plurality of streams by serial-to-parallel conversion. Modulators 13-1 to 13-M map these streams on a complex plane to generate modulated data symbols.

[0033]S / P converters 14-1 to 14-M perform serial-to-parallel conversion on the modulated data symbols so that they are transmitted on subcarriers of orthogonal frequency-division multiplexing (OFDM). In addition, inverse fast Fourier transform (IFFT) units 18-1 to 18-M transform these signals on the frequency domain into the time domain signals. The outpu...

second embodiment

[0082]In the first embodiment, the number N of subcarriers is divisible by the number M of antennas. In a second embodiment, an example of a case in which N is indivisible by M, such as a long preamble of a wireless LAN, will be explained. Of 64 IFFT samples in a wireless LAN, usable subcarriers are 52 subcarriers, and other subcarriers are not carried on signals. In this case, if the number M of antennas is three, N is indivisible by M, so the number of subcarriers allocated to each antenna changes from one antenna to another.

[0083]For example, in a long preamble L−26,26 of the IEEE 802.11a, signals having patterns as shown in Table 2 below are present in the −26th to 26th subcarriers, and transmitted by BPSK modulation.

TABLE 2IEEE 802.11a long preamble structure (L−26, 26)Carrier number−26−25−24−23−22−21−20−19−18−17−16−15−14Sequence11−1−111−11−11111Carrier number−13−12−11−10−9−8−7−6−5−4−3−2−1Sequence11−1−111−11−11111Carrier number+1+2+3+4+5+6+7+8+9+10+11+12+13Sequence1−1−111−11−11...

third embodiment

[0097]A method of transmitting known symbols for channel estimation according to a third embodiment of the present invention will be described below with reference to FIGS. 4A and 4B. FIGS. 4A and 4B show the structures of radio frames containing preambles when the numbers of antennas which simultaneously transmit known symbols are two and three, respectively.

[0098]In the first embodiment, channel estimation can be performed by receiving M known symbols for the number M of transmitting antennas. In contrast, the third embodiment assumes the reception of 2M known symbols in order to raise the accuracy of channel estimation in FIG. 3. When the known symbol pattern LP(M,n) (M is the number of transmitting antennas, and n is the pattern number) explained in the first embodiment is used, known symbols are transmitted as follows in the third embodiment.

[0099]Antenna 1: transmitted in the order of LP(2,1), LP(2,1), LP(2,2), and LP(2,2);

[0100]Antenna 2: transmitted in the order of LP(2,2), ...

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Abstract

Before data is transmitted from a plurality of antennas, a plurality of known symbol sequences are transmitted from these antennas. Each known symbol sequence contains a plurality of known symbols having different subcarrier arrangements. Known symbols transmitted from different antennas have different subcarrier arrangements.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. patent application Ser. No. 11 / 135,298 filed on May 24, 2005, all of which is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-160268, filed May 28, 2004, the entire contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a so-called MIMO-OFDM wireless communication apparatus particularly useful in a high-speed wireless LAN which performs communication by using a plurality of antennas and a plurality of subcarriers.[0004]2. Description of the Related Art[0005]In the conventional wireless LAN standard, e.g., the IEEE 802.11a, synchronous processing and channel estimation are performed by transmitting known symbols (a short preamble and long preamble) before a data signal. By using these preambles, the subsequent signal portion and data portion can be demodulate...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04L1/02H04J99/00H04B7/04H04B7/06H04J11/00H04L25/02H04L27/26
CPCH04B7/04H04L5/0023H04L25/0226H04L25/0204H04L5/0048
Inventor TAKEDA, DAISUKEEGASHIRA, YOSHIMASAAOKI, TSUGUHIDETANABE, YASUHIKOHARADA, KOHSUKEUCHIKAWA, HIRONORI
Owner TAKEDA DAISUKE
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