# US 7,411,928 B2 · Simplified decoder for a bit interleaved COFDM-MIMO system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,411,928 B2 - Document ID: US7411928B2 - Status: Granted - Kind: B2 - Application number: 10/537,221 - Filed: 2003-11-18 - Published: 2006-05-04 - Granted: 2008-08-12 - Earliest claimed: 2002-12-03 - Assignees: Koninklijke Philips Electronics N.V. - Inventors: Monisha Ghosh; Xuemei Ouyang - Web page: https://patentgrep.com/patent/US7411928B2 ## CPC - H04L 1/0071: {Use of interleaving (interleaving per se H03M13/27)} - H04B 7/0854: {using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion} - H04L 1/0054: {Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms} - H04L 1/06: using space diversity - H04L 27/2601: {Multicarrier modulation systems} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Multiple input multiple output (MIMO) systems are candidates for higher data rate wireless communication systems. Currently, for a single input single output (SISO) 1802.11a system can provide a transmission data rate up to 54 Mbps. The present invention is a 2 by 2 Multiple In Multiple Out (MIMO) system having a decoding apparatus that increases the data rate to over 100 Mbps but at a computation cost about the same as for optimal decoding for a SISO system and 1/64 of the optimal decoding for a 2 by 2 MIMO system. At a bit error rate (BER) of 10-4 level, the 2 by 2 MIMO system of the present invention provides double the transmission data rate of the SISO system with approximately the same signal to noise ratio (SNR). ## Claims ### Claim 1 A 2×2 wireless local area network, comprising: a first and a second single input single output (SISO) system respectively having a first and second transmitter antenna that transmit a first and second transmitted signal s1 and s2; a first and second receiver antenna that receive a first and second received signal r1 and r2; and a demapping and signal separation module that employs zero forcing (ZF) to guide maximum likelihood (ML) decoding and is connected to said first and second SISO system and is adapted to process said first and second received signal, wherein a data transmission rate of the 2×2 system is greater than 100 Mbps at a bit error rate of 10−4 and a computation cost for decoding on the order of the decoding cost for an optimal SISO system; wherein the demapping and signal separation module employs zero forcing (ZF) of the first and second received signal, respectively, which received signals correspond to ( r 1 r 2 ) = ( h 11 h 21 h 12 h 22 ) ⁢ ( s 1 s 2 ) + ( n 1 n 2 ) and results in the first and second transmitted signal being calculated as ( s ~ 1 s ~ 2 ) = ( h 11 h 21 h 12 h 22 ) - 1 ⁢ ( r 1 r 2 ) and finds the minimum Euclidean distance between ZF calculated symbol and a constellation point to estimate by hard decision the first and second transmitted signal as first and second estimated signal as ( s ^ 1 s ^ 2 ) which are then used to guide the maximum likelihood (ML) decoding, wherein, hij represents a channel from the ith transmitter antenna to the jth receiver antenna and ni are noise signal for i,j=1,2. ### Claim 2 (depends on 1) The 2×2 system of claim 1, wherein respective bit metrics calculated for first and second transmitted signal s1 and s2 are calculated using ( s ^ 1 s ^ 2 ) as follows for s1 m 1 ⁢ i 0 = min s m ∈ S 0 ⁢ ( (  r 1 - h 11 ⁢ s m - h 21 ⁢ s ^ 2  2 +  r 2 - h 12 ⁢ s m - h 22 ⁢ s ^ 2  2 ) | b 1 ⁢ i = 0 ) m 1 ⁢ i 1 = min s m ∈ S 1 ⁢ ( (  r 1 - h 11 ⁢ s m - h 21 ⁢ s ^ 2  2 +  r 2 - h 12 ⁢ s m - h 22 ⁢ s ^ 2  2 ) | b 1 ⁢ i = 1 ) and for s2 m 2 ⁢ i 0 = min s n ∈ S 0 ⁢ ( (  r 1 - h 11 ⁢ s ^ 1 - h 21 ⁢ s n  2 +  r 2 - h 12 ⁢ s ^ 1 - h 22 ⁢ s n  2 ) | b 2 ⁢ i = 0 ) m 2 ⁢ i 1 = min s n ∈ S 1 ⁢ ( (  r 1 - h 11 ⁢ s ^ 1 - h 21 ⁢ s n  2 +  r 2 - h 12 ⁢ s ^ 1 - h 22 ⁢ s n  2 ) | b 2 ⁢ i = 1 ) and the bit metrics pairs (m1i0, m1i1) (m2i0, m2i1) are sent to a respective first and second deinterleaver and a first and secondViterbi decoder for decoding, wherein b1i and b2i respectively is a bit in signal s1 and s2 for which a decision is being made. ### Claim 3 (depends on 1) The 2×2 system of claim 1, wherein the demapping and signal separation module obtains a first and second constellation point, s1ip and s2ip, satisfying the minimum Euclidean distance from first and second transmitted signal {tilde over (s)}1 and {tilde over (s)}2 for bit i min s ∈ S i p ⁢  s ~ q - s  2 where q=1, 2 and sip represents the subset of a constellation point set for bit i, the bit for which a decision is being made, such that pε{0,1}, uses these constellation points as input to a maximum likelihood calculation in the form of a bit metrics calculation for p=0,1 m 1 ⁢ ⁢ i p = (   r 1 - h 11 ⁢ s 1 ⁢ i p - h 21 ⁢ s ^ 2   2 +   r 2 - h 12 ⁢ s 1 ⁢ i p - h 22 ⁢ s ^ 2   2 ) m 2 ⁢ i p = (   r 1 - h 11 ⁢ s ^ 1 - h 21 ⁢ s 2 ⁢ i p   2 +   r 2 - h 12 ⁢ s ^ 1 - h 22 ⁢ s 2 ⁢ i p   2 ) and the bit metrics pairs (m1i0, m1i1) (m2i0, m2i1) are sent to a respective first and second deinterleaver and a first and second Viterbi decoder for decoding. ### Claim 4 (depends on 1) The 2×2 system of claim 1, wherein the demapping and signal separation module performs a slice-compare-select operation to determine a first and second constellation point, s1ip and s2ip, corresponding to the ZF signal which first and second constellation point is used as input to a maximum likelihood calculation in the form of a bit metrics calculation for p=0,1 m 1 ⁢ ⁢ i p = (   r 1 - h 11 ⁢ s 1 ⁢ i p - h 21 ⁢ s ^ 2   2 +   r 2 - h 12 ⁢ s 1 ⁢ i p - h 22 ⁢ s ^ 2   2 ) m 2 ⁢ i p = (   r 1 - h 11 ⁢ s ^ 1 - h 21 ⁢ s 2 ⁢ i p   2 +   r 2 - h 12 ⁢ s ^ 1 - h 22 ⁢ s 2 ⁢ i p   2 ) and the bit metrics pairs (m1i0, m1i1) (m2i0, m2i1) are sent to a respective first and second deinterleaver and a first and second Viterbi decoder for decoding. ### Claim 5 (depends on 1) The 2×2 system of claim 1, wherein said first and second SISO system is based on a 54 Mbps IEEE 802.11a SISO orthogonal frequency division multiplexing (OFDM) system.